7.8-i

Table of Contents

Section 7 ..................................................................................................................................................

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.8 Prestressed Double Tees ........................................................................ 7.8.1 

 

 7.8.1 Introduction ................................................................................ 7.8.1 

 

 7.8.2 Design Characteristics ................................................................ 7.8.1 

 General ............................................................................... 7.8.1 

 Primary Members and Secondary Members ...................... 7.8.3 

 Steel Reinforcement ........................................................... 7.8.3 

 

 7.8.3 Overview of Common Defects................................................... 7.8.4 

 

 7.8.4 Inspection Procedures and Locations ......................................... 7.8.4 

 Procedures .......................................................................... 7.8.4 

 Visual........................................................................... 7.8.4 

 Physical........................................................................ 7.8.4 

 Advanced Inspection Techniques ................................ 7.8.5 

 Locations ............................................................................ 7.8.5 

 Bearing Areas............................................................... 7.8.5 

 Shear Zones.................................................................. 7.8.6 

 Tension Zones.............................................................. 7.8.6 

 Secondary Members..................................................... 7.8.6 

 Areas Exposed to Drainage.......................................... 7.8.6 

 Areas Exposed to Traffic ............................................. 7.8.7 

 Areas Previously Repaired........................................... 7.8.7 

General......................................................................... 7.8.7 

 7.8.5 Evaluation................................................................................... 7.8.7 

 NBI Rating Guidelines ....................................................... 7.8.7 

Element Level Condition State Assessment....................... 7.8.7 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.8: Prestressed Double Tees 

7.8-ii

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7.8.1 

Topic 7.8 Prestressed Double Tees 

7.8.1 

Introduction A prestressed double tee beam, like the name implies, resembles two capital letter 

T’s that are side by side (see Figure 7.8.1). The horizontal section is called the 

deck or flange, and the two vertical leg sections are called the webs or stems. This 

type of bridge beam is mostly used in short spans or in situations where short, 

obsolete bridges are to be replaced. 

Figure 7.8.1 Typical Prestressed Double Tee Beam 

7.8.2 

Design 

Characteristics 

General Prestressed concrete double tee beams have a monolithic deck and stem design 

that allows the deck to act integrally with the superstructure. The integral design 

provides a stiffer member, while the material-saving shape reduces the dead load

(see Figure 7.8.2). 

This type of construction was originally used for buildings and is quite common in 

parking garages. They have been adapted for use in highway structures. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.8: Prestressed Double Tees 

7.8.2 

Lateral Connectors, all 

Double Tee types

4 1⁄2" Min.

Usually at 

Mid-Span

4 1⁄2"

1'-0"

Max.

(under rail)

Wearing Surface

Figure 7.8.2 Prestressed Double Tee Beam Typical Section 

Prestressed double tees have a typical stem depth of 305 to 865 mm (12 to 34 

inches). The average flange width is 2.4 to 3.1 m (8 to 10 feet), with a typical span 

length of approximately 7.6 to 16.8 m (25 to 55 ft). Prestressed double tees can be 

used in spans approximately 24.4 m (80 ft) long with stem depths up to 1.5 m (5 

feet) and flange widths up to 3.7 m (12 feet). Prestressed double tee bridges are 

typically simple spans, but continuous spans have also been constructed. 

Continuity is achieved from span to span by forming the open section between 

beam ends, placing the required reinforcement, and casting concrete in the void 

area. Once the concrete reaches its design strength, the spans are considered to be 

continuous for live load. 

In some prestressed double tee designs, the depth of the stems at the beam end is 

dapped, or reduced (see Figure 7.8.3). This occurs so that the beam end can sit 

flush on the bearing seat. 

Dapped Ends

Figure 7.8.3 Dapped End of a Prestressed Double Tee Beam 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.8: Prestressed Double Tees 

7.8.3 

The top of the flange or deck section of prestressed double tees can act as the 

integral wearing surface or be overlaid. Bituminous asphalt and concrete are 

typical examples of wearing surfaces that may be applied. See Topic 5.2.3 for a 

detailed description of the different types of concrete deck wearing surfaces. 

Primary Members and 

Secondary Members 

The primary members of a prestressed double tee beam are the stems and the deck. 

The secondary members of a prestressed double tee bridge are the transverse 

diaphragms. The diaphragms are located at the span ends. They connect adjacent 

stems and prevent lateral movement. In the case of longer spans, intermediate 

diaphragms may also be placed to compensate for torsional forces. The 

diaphragms can be constructed of reinforced concrete or steel. 

Steel Reinforcement The primary tension and shear steel reinforcement consists of prestressing strands 

and mild reinforcement (see Figure 7.8.4). The prestressing strands are placed 

longitudinally in each stem at the required spacing and clearance. When the 

double tees are to be continuous over two or more spans, conduits may be draped 

through the stems of each span to allow for post-tensioning. The shear 

reinforcement in a prestressed double tee beam consists of vertical U-shaped 

stirrups that extend from the stem into the flange. The shear reinforcement or 

stirrups are spaced along the length of the stem at a spacing required by design. 

The primary reinforcement for the deck or flange section of a prestressed double 

tee beam follows the reinforcement pattern of a typical concrete deck (see Topic 

5.2.2). 

In some wider applications, the deck or flange portions of adjacent prestressed 

double tee beams may be transversely post-tensioned together through posttensioning ducts. Transverse post-tensioning decreases the amount of damage that 

can occur to individual flange sides due to individual deflection and helps the 

double tee beams deflect as one structure. 

The secondary, or temperature and shrinkage, reinforcement is placed 

longitudinally on each side of each stem and deck. In some newer designs, 

welded-wire-fabric is used as the secondary and shear reinforcement in the stems. 

The vertical bars in the welded-wire-fabric act as the shear reinforcement and the 

longitudinal bars perform as the secondary reinforcement. Tests have shown that 

temperature and shrinkage cracking can be reduced when welded-wire-fabric is 

used. 

Prestressing Strands

Temperature and 

Shrinkage 

Reinforcement

Deck Tension Reinforcement

Stem

Shear 

Reinforcement

Figure 7.8.4 Steel Reinforcement in a Prestressed Double Tee Beam 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.8: Prestressed Double Tees 

7.8.4 

7.8.3 

Overview of 

Common Defects 

Common defects that occur on prestressed concrete double tee beam bridges 

include: 

3⁄4 Cracking (flexure, shear, temperature, shrinkage, mass concrete) 

3⁄4 Scaling 

3⁄4 Delamination 

3⁄4 Spalling 

3⁄4 Chloride contamination 

3⁄4 Efflorescence 

3⁄4 Ettringite formation 

3⁄4 Honeycombs 

3⁄4 Pop-outs 

3⁄4 Wear 

3⁄4 Collision damage 

3⁄4 Abrasion 

3⁄4 Overload damage 

3⁄4 Reinforcing steel corrosion 

3⁄4 Prestressed concrete deterioration 

3⁄4 Stress corrosion of prestressing strands 

Refer to Topic 2.2 for a detailed explanation of the properties of concrete, types 

and causes of concrete deterioration, and the examination of concrete. 

7.8.4 

Inspection 

Procedures 

Locations 

Inspection procedures to determine other causes of concrete deterioration are 

discussed in detail in Topic 2.2.8. 

Procedures Visual 

The inspection of prestressed double tees for cracks, spalls, and other defects is 

primarily a visual activity. 

Physical 

Sounding by hammer can be used to detect delaminated areas. A delaminated area 

will have a distinctive hollow “clacking” sound when tapped with a hammer or 

revealed with a chain drag. A hammer hitting sound concrete will result in a solid 

"pinging" type sound. In most cases, a chain drag is used to check the top surface 

of a concrete deck. 

Since prestressed beams are designed to maintain all concrete in compression, 

cracks are indications of serious problems. For this reason, any crack should be 

carefully measured with an optical crack gauge or crack comparator card and 

documented. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.8: Prestressed Double Tees 

7.8.5 

Advanced Inspection Techniques 

Several advanced techniques are available for concrete inspection. Nondestructive 

methods, described in Topic 13.2.2, include: 

3⁄4 Acoustic wave sonic/ultrasonic velocity measurements 

3⁄4 Delamination detection machinery 

3⁄4 Electrical methods 

3⁄4 Electromagnetic methods 

3⁄4 Pulse velocity 

3⁄4 Flat jack testing 

3⁄4 Ground-penetrating radar 

3⁄4 Impact-echo testing 

3⁄4 Infrared thermography 

3⁄4 Laser ultrasonic testing 

3⁄4 Magnetic field disturbance 

3⁄4 Neutron probe for detection of chlorides 

3⁄4 Nuclear methods 

3⁄4 Pachometer 

3⁄4 Rebound and penetration methods 

3⁄4 Ultrasonic testing 

Other methods, described in Topic 13.2.3, include: 

3⁄4 Core sampling 

3⁄4 Carbonation 

3⁄4 Concrete permeability 

3⁄4 Concrete strength 

3⁄4 Endoscopes and videoscopes 

3⁄4 Moisture content 

3⁄4 Petrographic examination 

3⁄4 Reinforcing steel strength 

3⁄4 Chloride test 

3⁄4 Matrix analysis 

3⁄4 ASR evaluation 

Locations Bearing Areas 

Examine bearing areas for cracking, delamination or spalling where friction from 

thermal movement and high bearing pressure could overstress the concrete. Check

for crushing of the stem near the bearing seat. Check the condition and operation 

of any bearing devices. 

For dapped-end double tee beams, look for vertical flexure cracks and diagonal 

shear cracks in the reduced depth section that sits on the bearing seat. At the full 

depth-to-reduced depth vertical interface, check for vertical direct shear cracking. 

At the bottom corner where the reduced section meets the full depth section, check 

for diagonal shear corner cracks. At the bottom corner of the full depth section, 

check for diagonal tension cracks (see Figure 7.8.5). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.8: Prestressed Double Tees 

7.8.6 

1. Nib 

Flexure 

Crack

2. Direct Shear Crack

3. Shear Corner 

Crack

4. Nib Inclined 

Shear Crack

5. Diagonal 

Tension 

Crack

Figure 7.8.5 Crack Locations for Dapped End Double Tee Beams 

 Shear Zones 

Inspect the area near the supports for the presence of shear cracking. The presence 

of transverse cracks on the underside of the stems or diagonal cracks on the sides 

of the stem indicate the onset of shear failure. These cracks represent lost shear 

capacity and should be carefully measured. 

Tension Zones 

Tension zones should be examined for flexure cracks, which would be transverse 

across the bottom of the stems and vertical on the sides. The tension zones are at 

the midspan along the bottom of the stem for both simple and continuous span 

bridges. Additional tension zones are located on the deck over the piers of 

continuous spans. 

Flexural cracks caused by tension in the deck will be found on the underside in a 

longitudinal direction between the stems. 

 

Check for deteriorated concrete near the tension zones, which could result in the 

debonding of the tension reinforcement. This would include delamination, spalls, 

and contaminated concrete. 

 Secondary Members 

The diaphragms are designed as simple beams and should be inspected for flexure 

and shear cracks as well as typical concrete defects. Cracks in the diaphragms 

could be an indication of overstress or excessive differential deflection in the 

double tee beams or differential settlement of the substructure. 

 Areas Exposed to Drainage 

If the roadway surface is bare concrete, check for delamination, scaling and spalls. 

The curb lines are most suspect. If the deck has an asphalt wearing surface, check 

for indications of deteriorated concrete such as reflective cracking and depressions.
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.8: Prestressed Double Tees 

7.8.7 

Inspect the seam or joint between adjacent beams for leakage. 

Check around scuppers or drain holes and deck fascias for deteriorated concrete. 

Check areas exposed to drainage for concrete spalling or cracking. This may 

occur at the ends of the beams where drainage has seeped through the deck joints. 

 Areas Exposed to Traffic 

For grade crossing structures, check areas of damage caused by collision. This 

will generally be a corner spall with a few exposed rebars or prestressing strands. 

 Areas Previously Repaired 

Examine areas that have been previously repaired. Determine if the repairs are in 

place and if they are functioning properly. 

 General 

Check for efflorescence from cracks and discoloration of the concrete caused by 

rust stains from the reinforcing steel. In severe cases, the reinforcing steel may 

become exposed due to spalling. Document the remaining cross section of 

reinforcing steel since section loss will decrease live load capacity. See Table 

2.2.2 for concrete crack width guidelines. 

Using a string line, check for horizontal alignment and camber of the prestressed 

double tee beams. Signs of downward deflection usually indicate loss of prestress. 

Signs of excessive upward deflection usually indicate extreme creep and 

shrinkage. 

7.8.5 

Evaluation State and federal rating guideline systems have been developed to aid in the 

inspection of concrete superstructures. The two major rating guideline systems 

currently in use are the FHWA's Recording and Coding Guide for the Structural 

Inventory and Appraisal of the Nation's Bridges used for the National Bridge 

Inventory (NBI) component rating method and the AASHTO element level 

condition state assessment method. 

NBI Rating Guidelines Using NBI rating guidelines, a 1-digit code on the Federal Structure Inventory and

Appraisal (SI&A) sheet indicates the condition of the deck and the superstructure. 

Rating codes range from 9 to 0, where 9 is the best rating possible. See Topic 4.2

(Items 58 and 59) for additional details about NBI Rating Guidelines. 

The previous inspection data should be considered along with current inspection 

findings to determine the correct rating. 

For prestressed double tees, the deck condition influences the superstructure 

component rating. When the deck component rating is 4 or less, the superstructure 

component rating may be reduced if the recorded deck defects reduce its ability to 

carry applied stresses associated with superstructure moments. 

Element Level Condition 

State Assessment 

In an element level condition state assessment of a prestressed double tee beam 

bridge, the AASHTO CoRe element is one of the following, depending on the 

riding surface: 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.8: Prestressed Double Tees 

7.8.8 

Element No. Description

Concrete Deck

012 Concrete Deck – Bare 

013 Concrete Deck – Unprotected with AC Overlay 

014 Concrete Deck – Protected with AC Overlay 

018 Concrete Deck – Protected with Thin Overlay 

022 Concrete Deck – Protected with Rigid Overlay 

026 Concrete Deck – Protected with Coated Bars 

027 Concrete Deck – Protected with Cathodic System 

P/S Girder/Beam

109 P/S Concrete Open Girder/beam 

The unit quantity for the deck elements is “each”, and the entire element must be 

placed in one of the five available condition states based solely on the top surface 

condition. Some states have elected to use the total deck area (m2 or ft2). When a 

total area is used, the total area must be distributed among the five available 

condition states depending on the extent and severity of deterioration. The sum of 

all condition states must equal the total quantity of the CoRe element. The 

inspector must know the total deck surface area in order to calculate a percent 

deterioration and fit into a given condition state description. The unit quantity for 

the prestressed double tee beam is meters or feet, and the total length must be

distributed among the four available condition states depending on the extent and 

severity of deterioration. Condition state 1 is the best possible rating. See the 

AASHTO Guide for Commonly Recognized (CoRe) Structural Elements for 

condition state descriptions. 

A Smart Flag is used when a specific condition exists, which is not described in 

the CoRe element condition state. The severity of the damage is captured by 

coding the appropriate Smart Flag condition state. The Smart Flag quantities are 

measured as each, with only one each of any given Smart Flag per bridge. 

For structural cracks in the top surface of bare decks, the “Deck Cracking” Smart 

Flag, Element No. 358, can be used and one of four condition states assigned. Do 

not use Smart Flag, Element No. 358, if the bridge deck/slab has any overlay 

because the top surface of the structural deck is not visible. For concrete defects 

on the underside of a deck element, the “Soffit” Smart Flag, Element No. 359, can 

be used and one of five condition states assigned. For damage due to traffic 

impact, the “Traffic Impact” Smart Flag, Element No. 362, can be used and one of 

three condition states assigned. 

Figure 7.8.6 Components/Elements for Evaluation 
7.9-i

Table of Contents

Section 7 ..................................................................................................................................................

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.9 Prestressed I-Beams and Bulb-Tees....................................................... 7.9.1 

 7.9.1 Introduction............................................................................... 7.9.1 

 

 7.9.2 Design Characteristics............................................................... 7.9.1 

 General................................................................................. 7.9.1 

 Materials - Strength and Durability ..................................... 7.9.2 

 Continuity ............................................................................ 7.9.3 

 Composite Action ................................................................ 7.9.4 

 Primary Members and Secondary Members........................ 7.9.5 

 Steel Reinforcement............................................................. 7.9.5 

 Primary Reinforcement................................................ 7.9.5 

 High Strength Steel ............................................... 7.9.5 

 Mild Steel .............................................................. 7.9.5 

 Secondary Reinforcement............................................ 7.9.6 

 Composite Strands ............................................................... 7.9.6 

 7.9.3 Overview of Common Defects ................................................. 7.9.6 

7.9.4 Inspection Procedures and Locations ....................................... 7.9.7 

 Procedures .......................................................................... 7.9.7 

 Visual........................................................................... 7.9.7 

 Physical........................................................................ 7.9.7 

 Advanced Inspection Techniques ................................ 7.9.7 

 Locations ............................................................................ 7.9.8 

 Bearing Areas............................................................... 7.9.8 

 Shear Zones.................................................................. 7.9.9 

 Tension Zones.............................................................. 7.9.9 

 Secondary Members................................................... 7.9.10 

 Areas Exposed to Drainage........................................ 7.9.11 

 Areas Exposed to Traffic ........................................... 7.9.12 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb Tees 

7.9-ii

 Areas Previously Repaired......................................... 7.9.13 

 General....................................................................... 7.9.13 

 

 7.9.5 Evaluation ............................................................................... 7.9.14 

 NBI Rating Guidelines ..................................................... 7.9.14 

 Element Level Condition State Assessment..................... 7.9.14 
7.9.1

Topic 7.9 Prestressed I-Beams and Bulb-Tees 

7.9.1 

Introduction Prestressed I-beams and bulb-tees have been used since the 1950’s. They have 

proven to be effective because of their material saving shapes. The I or T shape 

allows a designer to have enough space to place the proper amount of 

reinforcement while reducing the amount of concrete needed (see Figure 7.9.1). 

Figure 7.9.1 Prestressed I-beam Superstructure 

7.9.2 

Design 

Characteristics 

Prestressed I-beams and bulb-tees make economical use of material since most of 

the concrete mass is located away from the neutral axis of the beam.

General Prestressed I-beams are shaped to provide minimum dead load with ample space 

for tendons. The most common prestressed concrete I-beam shapes are the 

AASHTO shapes used by most state highway agencies (see Figure 7.9.2). 

However, some highway agencies have developed variations of the AASHTO 

shapes to accommodate their particular needs. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.2

1067 mm

(42")

1600 mm &

1829 mm

(63" & 72")

711 mm

(28")

635 -

1372 mm

(28" - 54")

305 - 508 mm

(12" - 20")

406 - 560 mm

(16" - 26")

Type 1 - 4 Type 5 & 6

Figure 7.9.2 AASHTO Cross Sections of Prestressed I-beams 

Prestressed I-beams are used in spans ranging from 6 to 46 m (20 to 150 feet). 

They are generally most economical at spans from 18 to 35 m (60 to 115 feet). 

Materials – Strength and 

Durability 

Steel tendons with a tensile strength as high as 1860 Mpa (270 ksi) are located in 

the bottom flange. These tendons are used to induce compression across the entire 

section of the beam prior to and during application of live load. This results in a 

crack free beam when subjected to live load (see Topic 2.2.4). 

New technology may allow designers to reduce corrosion of prestressing strands. 

This reduction is made possible by using composite materials in lieu of steel. 

Carbon or glass fibers are two alternatives to steel prestressing strands that are 

being researched. 

Concrete used is also of higher strength ranging from 34 Mpa (5,000 psi) 

compressive strength up to 83 Mpa (12,000 psi). In addition, concrete has a higher 

quality due to better control of fabrication conditions in a casting yard. 

Reactive Powder Concrete (RPC) prestressed beams can come in an X shape (see 

Figure 7.9.3) or other concrete beam shapes. RPC prestressed beams may have an 

hourglass shape so as to take maximum advantage of RPC properties. Tested 

prestressed RPC beams are made without any secondary steel reinforcement and 

can carry the same load as a steel I-beam with virtually the same depth and weight. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.3

Figure 7.9.3 Reactive Powder Concrete (RPC) Prestressed X-beam 

Reactive Powder Concrete (RPC) creates a better bond between the cement and 

aggregate. This bond produces a material with a higher density, shear strength, 

and ductility than normal strength concrete. Silica fume is one of the ingredients 

in Reactive Powder Concrete that increases the strength. RPC prestressed beams 

are effective in situations where steel I-beams may be used, but are not effective 

where conventional strength prestressed concrete I-beams are strong enough. 

Continuity To increase efficiency in multi-span applications, prestressed I-beams and bulbtees can be made continuous for live load and/or to eliminate the deck joint. This 

is done using a continuous composite action deck and anchorage of mild steel 

reinforcement in a common end diaphragm (see Figures 7.9.4 and 7.9.5). 

Continuity has also been accomplished using posttensioning ducts cast into 

pretensioned beams. Tendons pulled through these ducts across several spans then 

are stressed for continuity. Cast-in-place concrete diaphragms are framed around 

the beams at the abutments and piers. 

Beam Beam

CL Pier

Beam Beam

CL Pier

Figure 7.9.4 Continuous Prestressed I-beam Schematic 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.4

Figure 7.9.5 Continuous Prestressed I-Beam Bridge 

Composite Action The deck is secured to and can be made composite with the prestressed beam by 

the use of extended stirrups which are cast into the I-beam (see Figure 7.9.6). 

Figure 7.9.6 Cast-In-Place Stirrups 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.5

Primary Members and 

Secondary Members 

The primary members are the prestressed beams. The secondary members are the 

end diaphragms and the intermediate diaphragms. End diaphragms are usually full 

depth and located at the abutments or piers. Intermediate diaphragms are partial 

depth and are used within the span for longer spans (see Figure 7.9.7). 

Diaphragms are cast-in-place concrete or rolled steel sections and are placed at 

either the end points, mid points, or third points along the span. 

Figure 7.9.7 Concrete End Diaphragm 

Steel Reinforcement Primary Reinforcement 

Primary reinforcement consists of main tension steel and shear reinforcement or 

stirrups. 

High Strength Steel 

Main tension steel consists of pretensioned high strength prestressing strands or 

tendons placed symmetrically in the bottom flange and lower portion of the web. 

Strands are 9.5, 11.1, 12.7, or15.2 mm (3/8, 7/16, 1/2 or 0.6 inch) in diameter and 

are generally spaced in a 50.8 mm (2 inch) grid. In the larger beams, main tension 

steel can include posttensioned continuity tendons which are located in ducts cast 

into the beam web (see Figure 7.9.8). 

 

Mild Steel 

Mild steel stirrups are vertical in the beam and located throughout the web at 

various spacings required by design (see Figure 7.9.8). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.6

 

Posttensioning 

Ducts

High Strength 

Steel Strands

Composite Action 

Stirrup Extension

Stirrups

Temperature and 

Shrinkage Steel

Figure 7.9.8 Prestressed I-beam Reinforcement (Schematic) 

 Secondary Reinforcement 

Secondary reinforcement includes mild steel temperature and shrinkage 

reinforcement which is longitudinal in the beam. 

Composite Strands Composite strands can be carbon fiber or glass fiber and are fairly new to the 

bridge prestressing industry. These strands are gaining acceptance due to the low 

corrosive properties compared to steel strands and will just be mentioned in this 

manual. 

7.9.3 

Overview of 

Common Defects 

Common defects that occur on prestressed I-beams and bulb-tees include: 

3⁄4 Cracking (flexure, shear, temperature, shrinkage, mass concrete) 

3⁄4 Scaling 

3⁄4 Delamination 

3⁄4 Spalling 

3⁄4 Chloride contamination 

3⁄4 Efflorescence 

3⁄4 Ettringite formation 

3⁄4 Honeycombs 

3⁄4 Pop-outs 

3⁄4 Wear 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.7

3⁄4 Collision damage 

3⁄4 Abrasion 

3⁄4 Overload damage 

3⁄4 Reinforcing steel corrosion 

3⁄4 Prestressed concrete deterioration 

3⁄4 Stress corrosion of prestressing strands 

Refer to Topic 2.2 for a detailed presentation of the properties of concrete, types 

and causes of concrete deterioration, and the examination of concrete. 

7.9.4 

Inspection 

Procedures and 

Locations 

Inspection procedures to determine other causes of concrete deterioration are 

discussed in detail in Topic 2.2.8. 

Procedures Visual 

The inspection of prestressed concrete I-beams and bulb-tees for cracks, spalls, 

and other defects is primarily a visual activity. 

Physical 

Sounding by hammer can be used to detect delaminated areas. A delaminated area 

will have a distinctive hollow “clacking” sound when tapped with a hammer or 

revealed with a chain drag. A hammer hitting sound concrete will result in a solid 

"pinging" type sound. 

Since prestressed beams are designed to maintain all concrete in compression, 

cracks are indications of serious problems. For this reason, any crack should be 

carefully measured with an optical crack gauge or crack comparator card and 

documented. 

Advanced Inspection Techniques 

Several advanced techniques are available for concrete inspection. Nondestructive 

methods, described in Topic 13.2.2, include: 

3⁄4 Acoustic wave sonic/ultrasonic velocity measurements 

3⁄4 Delamination detection machinery 

3⁄4 Electrical methods 

3⁄4 Electromagnetic methods 

3⁄4 Pulse velocity 

3⁄4 Flat jack testing 

3⁄4 Ground-penetrating radar 

3⁄4 Impact-echo testing 

3⁄4 Infrared thermography 

3⁄4 Laser ultrasonic testing 

3⁄4 Magnetic field disturbance 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.8

3⁄4 Neutron probe for detection of chlorides 

3⁄4 Nuclear methods 

3⁄4 Pachometer 

3⁄4 Rebound and penetration methods 

3⁄4 Ultrasonic testing 

Other methods, described in Topic 13.2.3, include: 

3⁄4 Core sampling 

3⁄4 Carbonation 

3⁄4 Concrete permeability 

3⁄4 Concrete strength 

3⁄4 Endoscopes and videoscopes 

3⁄4 Moisture content 

3⁄4 Petrographic examination 

3⁄4 Reinforcing steel strength 

3⁄4 Chloride test 

3⁄4 Matrix analysis 

3⁄4 ASR evaluation 

Locations Bearing Areas 

Check bearing areas for defects such as delaminations, spalls or vertical cracks 

(see Figure 7.9.9). Defects may be caused by corrosion of steel due to water 

leakage or restriction of thermal movement due to a faulty bearing mechanism. 

Spalling could also be caused by poor quality concrete placement (see Figure 

7.9.10). 

Check for crushing of flange near the bearing seat. 

Check for rust stains which indicate corrosion of steel reinforcement. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.9

Figure 7.9.9 Bearing Area of a Typical Prestressed I-beam 

Figure 7.9.10 Spalling Due to Poor Concrete

Shear Zones 

Check beam ends and sections over piers for transverse cracks on the bottom 

flange and for diagonal shear cracks in webs. These web cracks will project 

diagonally upward from the support toward midspan. 

 Tension Zones 

Inspect the tension zones of the beams for structural cracks. Cracking indicates a 

very serious problem resulting from overloading or loss of prestress. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.10

Check for deteriorated concrete that could cause debonding of the tension 

reinforcement. This would include spalls, delamination, and cracks with 

efflorescence. 

Check bottom flange for longitudinal cracks that may indicate a deficiency of 

prestressing steel, insufficient cover, inadequate spacing, or possibly an 

overloading of the concrete due to use of prestressing strands that are too large. 

Check bottom flange at midspan for flexure cracks due to positive moment (see 

Figure 7.9.11). These cracks will be quite small and difficult to detect. An optical 

crack gauge or crack comparator card should be used to measure any cracks found.

For continuous bridges, check the deck area over the piers for flexure cracks due to 

negative moment. 

Check for rust stains from cracks, indicating corrosion of steel reinforcement or 

prestressing tendons. 

Check for exposed tension reinforcement and document section loss. Measurable 

section loss will decrease live load capacity. Exposed prestressing tendons are 

susceptible to stress corrosion and sudden failure. 

Figure 7.9.11 Flexure Crack 

 Secondary Members 

Inspect the end diaphragms for spalling or diagonal cracking (see Figure 7.9.12). 

This is a possible sign of overstress caused by substructure movement. 

Investigate the intermediate diaphragms for cracking and spalling concrete. 

Flexure and shear cracks may indicate excessive differential movement of the Ibeams. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.11

Figure 7.9.12 Typical Concrete Diaphragm 

 

Areas Exposed to Drainage 

Check around joints, scuppers, inlets or drain holes for leaking water or 

deterioration of concrete (see Figure 7.9.13). 

Figure 7.9.13 Leakage of Water at Joint between Spans 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.12

 Areas Exposed to Traffic 

Check areas damaged by collision. A significant amount of prestressed concrete 

bridge deterioration and loss of section is caused by traffic damage. Document the 

number of exposed and severed strands as well as the loss of concrete section. The 

loss of concrete due to such an accident is not always serious, unless the bond 

between the concrete and steel reinforcement is affected (see Figure 7.9.14). 

Figure 7.9.14 Collision Damage on Prestressed Concrete I-beam
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.13

 Areas Previously Repaired 

Examine thoroughly any repairs that have been previously made. Determine if 

repaired areas are sound and functioning properly. Effective repairs and patching 

are usually limited to protection of exposed tendons and reinforcement (see Figure 

7.9.15). 

 

Figure 7.9.15 Collision Damage Repair on Prestressed Concrete I-bBeam. Note 

Epoxy Injection Ports

 General 

Using a string line, check for horizontal alignment and camber of the prestressed 

beams. Signs of downward deflection usually indicate loss of prestress. Signs of 

excessive upward deflection usually indicate extreme creep and shrinkage. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.9: Prestressed I-Beams and Bulb-Tees 

7.9.14

7.9.5 

Evaluation State and federal rating guideline systems have been developed to aid in the 

inspection of concrete superstructures. The two major rating guideline systems 

currently in use are the FHWA's Recording and Coding Guide for the Structural 

Inventory and Appraisal of the Nation's Bridges used for the National Bridge 

Inventory (NBI) component rating method and the AASHTO element level 

condition state assessment method. 

NBI Rating Guidelines Using NBI rating guidelines, a 1-digit code on the Federal Structure Inventory and 

Appraisal (SI&A) sheet indicates the condition of the superstructure. Rating codes 

range from 9 to 0, where 9 is the best rating possible. See Topic 4.2 (Item 59) for 

additional details about NBI Rating Guidelines. 

The previous inspection data should be considered along with current inspection 

findings to determine the correct rating. 

Element Level Condition 

State Assessment 

In an element level condition state assessment of a prestressed I-beam or bulb-T 

bridge, the AASHTO CoRe element is: 

Element No. Description

109 Prestressed Concrete Open Girder/beam 

The unit quantity for the prestressed double I-beam is meters or feet, and the total 

length must be distributed among the four available condition states depending on 

the extent and severity of deterioration. Condition state 1 is the best possible 

rating. See the AASHTO Guide for Commonly Recognized (CoRe) Structural 

Elements for condition state descriptions. 

A Smart Flag is used when a specific condition exists, which is not described in 

the CoRe element condition state. The severity of the damage is captured by 

coding the appropriate Smart Flag condition state. The Smart Flag quantities are 

measured as each, with only one each of any given Smart Flag per bridge. 

For damage due to traffic impact, the “Traffic Impact” Smart Flag, Element No. 

362, can be used and one of the three condition states assigned. 
7.10-i

Table of Contents

Section 7 ..................................................................................................................................................

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.10 Prestressed Box Beams ........................................................................ 7.10.1 

 

 7.10.1 Introduction........................................................................... 7.10.1 

 

 7.10.2 Design Characteristics........................................................... 7.10.1 

 General ............................................................................. 7.10.1 

 Design............................................................................... 7.10.2 

 Simple/Continuous Spans .......................................... 7.10.2 

 Composite/Noncomposite.......................................... 7.10.2 

 Construction ..................................................................... 7.10.3 

 Advantages ....................................................................... 7.10.3 

 Dead Load Reduction ................................................ 7.10.3 

 Construction Time Savings........................................ 7.10.3 

 Shallow Depth............................................................ 7.10.4 

 Applications...................................................................... 7.10.4 

 Adjacent Box Beams.................................................. 7.10.4 

 Monolithic Action................................................. 7.10.5 

 Spread Box Beams..................................................... 7.10.6 

 Primary Members and Secondary Members ................... 7.10.6 

 Steel Reinforcement ......................................................... 7.10.7 

 Primary Reinforcement.............................................. 7.10.7

 Secondary Reinforcement.......................................... 7.10.8 

 Fiber Reinforced Polymer Strands ................................... 7.10.8 

 

 7.10.3 Overview of Common Defects ............................................. 7.10.8 

 

7.10.4 Inspection Procedures and Locations...................................... 7.10.9 

 Procedures ........................................................................ 7.10.9 

 Visual......................................................................... 7.10.9 

 Physical...................................................................... 7.10.9 

 Advanced Inspection Techniques .............................. 7.10.9 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10-ii

 Locations ........................................................................ 7.10.10 

 Bearing Areas........................................................... 7.10.10 

 Shear Zones.............................................................. 7.10.12 

 Tension Zones.......................................................... 7.10.12 

 Secondary Members................................................. 7.10.13 

 Areas Exposed to Drainage...................................... 7.10.14 

 Areas Exposed to Traffic ......................................... 7.10.15 

 Areas Previously Repaired....................................... 7.10.15 

 General..................................................................... 7.10.15 

 

 7.10.5 Evaluation ........................................................................... 7.10.16 

 NBI Rating Guidelines ................................................... 7.10.16 

 Element Level Condition State Assessment................... 7.10.17 
7.10.1

Topic 7.10 Prestressed Box Beams 

7.10.1 

Introduction Prestressed box beams are quite popular and have been used since the early 1950’s 

(see Figure 7.10.1). These precast prestressed members provide advantages from a 

construction and an economical standpoint by increasing strength while decreasing 

the dead load. 

Figure 7.10.1 Typical Box Beam Bridge 

7.10.2 

Design 

Characteristics 

General Prestressed box beams are constructed having a rectangular cross section with a 

single rectangular void inside. Many prestressed box beams constructed in the 

1950’s have single circular voids. The top and bottom slabs act as the flanges, 

while the side walls act as webs. The prestressing reinforcement is typically 

placed in the bottom flange and into both webs (see Figure 7.10.2). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.2

 

Void

Top Flange

Web

(typ.)

Bottom Flange

High Strength

Steel Strands

Figure 7.10.2 Box Beam Cross-Section 

The typical span length for prestressed concrete box beams ranges from 6 to 27 m 

(20 to 90 ft) depending on the beam size and spacing. 

Prestressed box beams are typically either 915 to 1220 mm (36 or 48 inches) wide. 

The depth of a box beam is typically 690 to 1070 mm (27 to 42 inches). Web wall 

thickness are typically 125 mm (5 inches) but can range from 75 to 150 mm (3 to 6 

inches). 

Design Simple/Continuous Spans 

Prestressed box beams can be simple or continuous spans. In the case of simple 

spans, the ends of the beams from span to span are not connected together at the 

support. An expansion joint is placed over the support in the concrete deck and 

the spans act independently. For continuous spans, the beam-ends from span to 

span are connected together by means of a cast-in-place concrete end diaphragm 

over the support. Mild steel reinforcement is placed in this diaphragm area and is 

spliced with steel reinforcement from the prestressed box beams (see Figure 

7.10.3). Additional mild steel reinforcement is placed longitudinally in the deck. 

Continuous spans provide advantages such as eliminating deck joints, making a 

continuous surface for live loads, distributing live loads, and lowering positive 

moment. 

Composite/Non-composite 

Prestressed box beams can be composite or non-composite. To obtain composite 

action, some prestressed box beams are constructed with stirrups extending out of 

the top flange (see Figure 7.10.3). These stirrups are engaged when a cast-in-place 

concrete deck is placed and hardens. Once the concrete deck hardens, the deck 

becomes composite with the prestressed box beams. This configuration can be 

considered composite since the compressive strength of the cast-in-place deck is 

significantly different than the precast prestressed box beams. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.3

Prestressed box beams can also be non-composite. If the stirrups are not extended 

into the deck, the prestressed box beams cannot achieve composite action with the 

deck. 

Figure 7.10.3 Box Beams at Fabrication Plant Showing Stirrups Extended as 

Shear Connectors and Extended Rebar for Continuity 

Construction Box beams are constructed similar to I-beams, with high strength steel strands or 

tendons placed in the bottom flange and lower web area The strength of the steel 

strands can be as high as 1860 MPa (270 ksi). 

Concrete compressive strengths of 27 to 41 MPa (4000 to 6000 psi) are typically 

used in prestressed box beams, but concrete with ultimate strengths over 83 MPa 

(12,000 psi) is available and becoming popular. 

High performance concrete (HPC), which is a new type of concrete being used in 

bridge members, is designed to meet the specific needs of a specific project. The 

mix design is based on the environmental conditions, strength requirements, and 

durability requirements. This type of concrete allows engineers to design smaller, 

longer, and more durable members with longer life expectancies. 

Advantages Dead Load Reduction 

The voided box beam reduces dead load while still providing flanges to resist the 

design moments and webs to resist the design shears. 

Construction Time Savings 

Precast members are cast and cured in a quality controlled casting yard. Because 

box beams are precast, the construction process takes less time. When 

construction is properly planned, using precast members allows structure to be 

erected with less traffic disruption than typical cast-in-place concrete construction.

Shear Connectors 

Continuity 

Reinforcement 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.4

Shallow Depth 

Prestressed box beams are designed with a typical maximum depth of 1070 mm 

(42 inches). This shallow depth makes box beams viable solutions for field 

conditions where shallow vertical clearances exist. 

Applications There are two applications of prestressed box beams (see Figure 7.10.4): 

3⁄4 Adjacent box beams 

3⁄4 Spread box beams 

Adjacent Box Beams

Spread Box Beams

Figure 7.10.4 Applications of Prestressed Box Beams 

 Adjacent Box Beams 

On an adjacent box beam bridge, the adjacent box beams are placed laterally side 

by side with no space between them. In some early applications, the top flange of 

each box is exposed and functions as the deck (see Figure 7.10.5). The practical 

span lengths range from 6 to 40 m (20 to 130 feet), with the most economical 

spans ranging from 12 to 27 m (40 to 90 feet). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.5

Figure 7.10.5 Adjacent Box Beams: Top Flanges Acting as the Deck 

In modern longer span applications, the deck is typically cast-in-place concrete,

and composite action with the box beam is achieved after the concrete hardens. 

For composite decks, stirrups extend above the top of the box to provide the 

transfer of shear forces. For the majority of shorter spans, nonstructural asphalt 

overlays are applied. Sometimes a waterproofing membrane is applied prior to the 

overlay placement. 

Monolithic Action 

Like precast slab units, adjacent box beams are post tensioned transversely. This 

is generally done using 1000 MPa (145 ksi) threaded bars and lock nuts, or 1860 

MPa (270 ksi) strands with locking wedges. Transverse post tensioning combined 

with grouted shear keys provides for monolithic action (see Figure 7.10.6). 

Post-tensioning duct

and tendon

Locking device and grout 

pocket

Grouted Shear Key 

(typical)

Figure 7.10.6 Transverse Post-tensioning of an Adjacent Box Beam Bridge 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.6

 Spread Box Beams 

On a spread box beam bridge, the box beams are usually spaced from 610 to 

1830 mm (2 to 6 feet) apart and typically use a composite cast-in-place concrete 

deck (see Figure 7.10.7). This application is practical for span lengths from 8 to 

26 m (25 to 85 feet). Stay-in-place forms or removable formwork is used between 

the box beams to provide a support when the concrete deck is placed. 

Figure 7.10.7 Underside of a Typical Spread Box Beam 

All modern box beams should have drain holes that are installed in the bottom slab 

during fabrication to allow any moisture in the void to escape. 

Primary Members and 

Secondary Members 

The primary members of box beam bridges are the concrete box beams. External 

diaphragms are the only secondary members on box beam bridges, and they are 

only found on spread box beam bridges (see Figure 7.10.8). The diaphragms may 

be cast-in-place, precast, or steel and are placed at either the mid points or third

points along the span and at the span ends. End diaphragms can provide restraint 

and act as a backwall. End diaphragms are located at the abutments and piers and 

can be full or partial depth. Intermediate diaphragms are usually partial depth. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.7

Figure 7.10.8 End and Intermediate Diaphragms on a Spread Box Beam Bridge 

Internal Diaphragms are considered a part of the prestressed box beams and not a 

secondary member (see Figure 7.10.9). 

2 or 3 spaces 

Duct for Thread

Bar or Strand Tendon

Voided Area

Figure 7.10.9 Schematic of Internal Diaphragms 

Steel Reinforcement Primary Reinforcement 

Primary reinforcement consists of main tension steel and shear reinforcement or 

stirrups. 

High Strength Steel 

Main tension steel consists of high strength pretensioned prestressing strands 

placed in the flange and lower web of the box beam. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.8

Depending on the age of the structure, the strand size will be 6, 10, 11 or 13 mm 

(1/4, 3/8, 7/16, or 1/2 inch) in diameter and spacing is normally 51 mm (2 inches) 

apart (see Figure 7.10.10). In some newer applications of prestressed box beams 

using HPC, 15mm (0.6-inch) strand sizes with a spacing of 51mm (2 inches) are 

used to fully implement the increased concrete strengths. 

Mild Steel 

Mild steel stirrups are placed vertically in the web at spacings required by design 

for shear reinforcement. Mild steel stirrups are more closely spaced near beam 

ends and typically grade 60. 

Secondary Reinforcement 

Transverse post-tensioning strands through the diaphragms helps maintain 

monolithic action between the adjacent box beams. Temperature and shrinkage 

reinforcement consisting of mild steel is placed longitudinal in the beam webs and 

top flange. 

High strength 

steel strands

Composite action

stirrup extension

Temperature and

shrinkage steel

Stirrups

Figure 7.10.10 Typical Prestressed Box Beam Reinforcement 

Fiber Reinforced 

Polymer Strands 

Composite strands can be carbon fiber or glass fiber and are fairly new to the 

bridge prestressing industry. These strands are gaining acceptance due to the low 

corrosive properties compared to steel strands and will just be mentioned in this 

manual. 

7.10.3 

Overview of 

Common Defects 

Common defects that occur on prestressed box beams include: 

3⁄4 Cracking (flexure, shear, temperature, shrinkage) 

3⁄4 Scaling 

3⁄4 Delamination 

3⁄4 Spalling 

3⁄4 Chloride contamination 

3⁄4 Efflorescence 

3⁄4 Ettringite formation 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.9

3⁄4 Pop-outs 

3⁄4 Wear 

3⁄4 Collision damage 

3⁄4 Abrasion 

3⁄4 Overload damage 

3⁄4 Reinforcing steel corrosion 

3⁄4 Prestressed concrete deterioration 

3⁄4 Stress corrosion of prestressing strands 

Refer to Topic 2.2 for a detailed presentation of the properties of concrete, types 

and causes of concrete deterioration, and the examination of concrete. 

7.10.4 

Inspection 

Procedures and 

Locations 

Inspection procedures to determine other causes of concrete deterioration are 

discussed in detail in Topic 2.2.8. 

Procedures Visual 

The inspection of prestressed concrete box beams for cracks, spalls, and other 

defects is primarily a visual activity. 

Physical 

Sounding by hammer can be used to detect delaminated areas. A delaminated area 

will have a distinctive hollow “clacking” sound when tapped with a hammer or 

revealed with a chain drag. A hammer hitting sound concrete will result in a solid 

"pinging" type sound. In most cases, a chain drag is used to check the top surface 

of an exposed top flange. 

Since prestressed box beams are designed to limit tensile stresses in concrete to 

specified thresholds, cracks are indications of serious problems. For this reason, 

any crack should be carefully measured with an optical crack gauge or crack 

comparator card and documented. 

Advanced Inspection Techniques 

Several advanced techniques are available for concrete inspection. Nondestructive 

methods, described in Topic 13.2.2, include: 

3⁄4 Acoustic wave sonic/ultrasonic velocity measurements 

3⁄4 Delamination detection machinery 

3⁄4 Electrical methods 

3⁄4 Electromagnetic methods 

3⁄4 Pulse velocity 

3⁄4 Flat jack testing 

3⁄4 Ground-penetrating radar 

3⁄4 Impact-echo testing 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.10

3⁄4 Impact-echo testing 

3⁄4 Infrared thermography 

3⁄4 Laser ultrasonic testing 

3⁄4 Magnetic field disturbance 

3⁄4 Neutron probe for detection of chlorides 

3⁄4 Nuclear methods 

3⁄4 Pachometer 

3⁄4 Rebound and penetration methods 

3⁄4 Ultrasonic testing 

Other methods, described in Topic 13.2.3, include: 

3⁄4 Core sampling 

3⁄4 Carbonation 

3⁄4 Concrete permeability 

3⁄4 Concrete strength 

3⁄4 Endoscopes and videoscopes 

3⁄4 Moisture content 

3⁄4 Petrographic examination 

3⁄4 Reinforcing steel strength 

3⁄4 Chloride test 

3⁄4 Matrix analysis 

3⁄4 ASR evaluation 

Locations Bearing Areas 

Check bearing areas for concrete delaminations, spalls or vertical/horizontal

cracks. Spalls and cracks may be caused by corrosion of steel reinforcement due 

to water leakage or restriction of thermal movement due to a faulty bearing 

mechanism. Delaminations, spalls and cracks may also be caused by the stresses 

created at the transfer of the prestressing forces (see Figure 7.10.11). 

Check for rust stains, which indicate corrosion of steel reinforcement (see Figure 

7.10.12). 

Check the bottom of beams for longitudinal cracks originating from the bearing 

location. These cracks are sometimes caused by the unbalanced transfer of 

prestress force to the concrete, or by the accumulation of water inside the box, 

freezing and thawing (see Figure 7.10.13). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.11

Figure 7.10.11 Spalled Beam Ends 

Figure 7.10.12 Exposed Bars at End of Box Beam 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.12

Figure 7.10.13 Longitudinal Cracks in Bottom Flange of Beam 

 Shear Zone 

Check beam ends and sections over piers for diagonal shear cracks in webs. These 

web cracks will project diagonally upward at approximately a 45 degree angle

from the support toward midspan (see Figure 7.10.14). 

Figure 7.10.14 Diagonal Shear Crack in Web of Beam 

 Tension Zones 

Inspect the lower portion of the beam, particularly at mid span, for flexure cracks. 

This indicates a very serious problem resulting from overloading or loss of 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.13

prestress. 

Check for delaminations, spalls and exposed reinforcing steel. Exposed strands fail 

prematurely due to stress corrosion (see Figure 7.10.15). 

Check for deteriorated concrete, which could cause debonding of the tension 

reinforcement. This would include spalls, delaminations, and cracks. 

Check bottom flange for longitudinal cracks which may indicate a deficiency of 

prestressing steel, or possibly an overloading of the concrete due to use of 

prestressing forces that are too large. 

For continuous bridges, check the deck area over the supports for flexure cracks 

due to negative moment in the beam. 

Figure 7.10.15 Spall and Exposed Reinforcement 

 Secondary Members 

Inspect the end diaphragms of spread box beams for delaminations, spalling and 

cracking. Diagonal cracking is a possible sign of shear failure and can be caused 

by substructure movement.

Inspect the intermediate diaphragms of spread box beams for delaminations, spalls 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.14

and cracks. Flexure and shear cracks may indicate excessive differential beam 

deflection. 

 Areas Exposed to Drainage 

Examine joints between adjacent box beams for leakage and rust stains. Look for 

reflective cracking in the traffic surface and differential beam deflection under live 

load. These problems indicate that the shear key between boxes has been broken 

and that the boxes are acting independently of each other (see Figure 7.10.16). 

These problems could also indicate the transverse post-tensioning is not acting as 

designed. The transverse post tensioning may have failed due to the leaking shear 

keys. 

Check around scuppers and inlets for leaking water or deterioration of concrete. 

Check the underside of beam ends for leakage at the expansion joint areas and the 

fascia of exterior beams. 

Check drain holes for proper function as accumulated water can freeze and crack 

the beam. 

Figure 7.10.16 Joint Leakage and Rust Stain 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.15

 Areas Exposed to Traffic 

Check areas damaged by collision. A significant amount of prestressed concrete 

bridge deterioration and loss of section is due to traffic damage. Document the 

number of exposed and severed strands as well as the loss of concrete section. The 

loss of concrete due to such an accident is not always serious, unless the bond 

between the concrete and steel reinforcement is affected (see Figure 7.10.17). 

Figure 7.10.17 Close-up of Collision Damage 

 Areas Previously Repaired 

Examine thoroughly any repairs that have been previously made. Determine if 

repaired areas are functioning properly. Effective repairs and patching are usually 

limited to protection of exposed tendons and reinforcement. 

 General 

Examine the sides of the beams for cracks. Adjacent box beam side surfaces are 

visible only on the fascias. For interior beams, inspect the bottom chamfers for 

cracks, which may extend along the sides of the beams. 

Using a string line, check for horizontal alignment and camber of the prestressed 

beams. Downward deflection usually indicates loss of prestress or damage to the 

post-tensioning tendon. Upward deflection usually indicates extreme initial 

prestressing forces or shrinkage. 

Note the presence of surface irregularities caused by burlap folds used in the old 

vacuum curing process. This dates the beam construction to the early 1950’s and 

should alert the inspector to possible deficiencies common in early box beams, 

such as inadequate or non-existent drainage openings and strand cover (see Figure 

7.10.18). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.16

Figure 7.10.18 Burlap Fold Depressions in an Early 1950's P/S Box Beam 

7.10.5 

Evaluation State and federal rating guideline systems have been developed to aid in the 

inspection of concrete superstructures. The two major rating guideline systems 

currently in use are the FHWA's Recording and Coding Guide for the Structural 

Inventory and Appraisal of the Nation's Bridges used for the National Bridge 

Inventory (NBI) component rating method and the AASHTO element level 

condition state assessment method. 

NBI Rating Guidelines Using NBI rating guidelines, a 1-digit code on the Federal Structure Inventory and 

Appraisal (SI&A) sheet indicates the condition of the superstructure. Rating codes 

range from 9 to 0, where 9 is the best rating possible. See Topic 4.2 (Items 58 

and 59) for additional details about NBI Rating Guidelines for decks and 

superstructures. 

The previous inspection data should be considered along with current inspection 

findings to determine the correct rating. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.17

Element Level Condition 

State Assessment 

In an element level condition state assessment of a prestressed box beam bridge, 

the AASHTO CoRe element for the deck is one of the following, depending on the 

riding surface; plus Element No. 104.: 

Element No. Description

Concrete Deck

012 Concrete Deck – Bare 

013 Concrete Deck – Unprotected with AC Overlay 

014 Concrete Deck – Protected with AC Overlay 

018 Concrete Deck – Protected with Thin Overlay 

022 Concrete Deck – Protected with Rigid Overlay 

026 Concrete Deck – Protected with Coated Bars 

027 Concrete Deck – Protected with Cathodic System 

P/S Box Girder

104 Prestressed Concrete Closed Girder/beam 

For this bridge type, the box girder top flange acts as a structural deck and is 

supported by the box girder webs. The unit quantity for the deck elements is 

“each”, and the entire element must be placed in one of the five available condition 

states based solely on the top surface condition. Some states have elected to use 

the total deck area (m2 or ft2). When a total area is used, the total area must be 

distributed among the five available condition states depending on the extent and 

severity of deterioration. The sum of all condition states must equal the total 

quantity of the CoRe element. The inspector must know the total deck surface 

area in order to calculate a percent deterioration and fit into a given condition state 

description. The unit quantity for the prestressed box beam is meters or feet, and 

the total length can be distributed among the four available condition states 

depending on the extent and severity of deterioration. Condition state 1 is the best 

possible rating. See the AASHTO Guide for Commonly Recognized (CoRe) 

Structural Elements for condition state descriptions. 

A Smart Flag is used when a specific condition exists, which is not described in 

the CoRe element condition state. The severity of the damage is captured by 

coding the appropriate Smart Flag condition state. The Smart Flag quantities are 

measured as each, with only one each of any given Smart Flag per bridge. 

For structural cracks in the top surface of bare decks, the “Deck Cracking” Smart 

Flag, Element No. 358, can be used and one of four condition states assigned. Do 

not use Smart Flag, Element No. 358, if the bridge deck/slab has any overlay 

because the top surface of the structural deck is not visible. Defects on the 

underside of a deck element are not visible in a box member. Therefore, the

“Soffit” Smart Flag, Element No. 359, is not applicable. For damage due to traffic 

impact, the “Traffic Impact” Smart Flag, Element No. 362, can be used and one of 

three condition states assigned. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.10: Prestressed Box Beams 

7.10.18

Figure 7.10.19 Components/Elements for Evaluation 
7.11-i

Table of Contents

Section 7 ..................................................................................................................................................

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.11 Concrete Box Girders........................................................................... 7.11.1 

 7.11.1 Introduction............................................................................. 7.11.1 

 7.11.2 Design Characteristics............................................................. 7.11.2 

 Concrete Box Girder......................................................... 7.11.2 

 Construction Methods................................................ 7.11.3 

 High Level Casting.............................................. 7.11.3 

 At-grade Casting.................................................. 7.11.4 

 Primary Members....................................................... 7.11.5 

 Steel Reinforcement................................................... 7.11.5 

 Segmental Box Girder ...................................................... 7.11.7 

 Segment Configurations............................................. 7.11.9 

 Segmental Classification.......................................... 7.11.10 

 Cast-in-place...................................................... 7.11.10 

 Precast ............................................................... 7.11.10 

 Construction Methods.............................................. 7.11.12 

 Balanced Cantilever .......................................... 7.11.12 

 Span-by-span Construction ............................... 7.11.13 

 Progressive Placement Construction ................. 7.11.16 

 Incremental Launching Construction ................ 7.11.17 

 7.11.3 Overview of Common Defects ............................................. 7.11.18 

7.11.4 Inspection Procedures and Locations.................................... 7.11.18 

 Procedures ...................................................................... 7.11.18 

 Visual................................................................. 7.11.18 

 Physical ............................................................. 7.11.18 

 Advanced Inspection Techniques...................... 7.11.19 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11-ii

 Locations ........................................................................ 7.11.19 

 Concrete Box Girder................................................ 7.11.19 

 Bearing Areas.................................................... 7.11.20 

 Shear Zones ....................................................... 7.11.21 

 Tension Zones ................................................... 7.11.21 

 Anchor Blocks................................................... 7.11.23 

 Secondary Members.......................................... 7.11.23 

 Areas Exposed to Drainage ............................... 7.11.24 

 Areas Exposed to Traffic................................... 7.11.24 

 Areas Previously Repaired ................................ 7.11.24 

 Miscellaneous Areas.......................................... 7.11.24 

 Segmental Box Girder.............................................. 7.11.28 

 Bearing Areas.................................................... 7.11.28 

 Shear and Tension Zones................................... 7.11.29 

 Anchor Blocks................................................... 7.11.30 

 Secondary Members.......................................... 7.11.30 

 Joints.................................................................. 7.11.30 

 Internal Diaphragms .......................................... 7.11.31 

 Areas Exposed to Drainage ............................... 7.11.32 

 Areas Exposed to Traffic................................... 7.11.32 

 Areas Previously Repaired ................................ 7.11.32 

 Miscellaneous Areas.......................................... 7.11.32 

 7.11.5 Evaluation ............................................................................. 7.11.33 

 NBI Rating Guidelines ................................................... 7.11.33 

 Element Level Condition State Assessment................... 7.11.33 
7.11.1

Topic 7.11 Concrete Box Girders 

7.11.1 

Introduction The popularity of box girder design is increasing. A trapezoidal box shape with 

cantilevered top flange extensions combines mild steel reinforcement and high 

strength post-tensioning tendons into a cross section capable of accommodating an 

entire roadway width. Both segmental and monolithic box girders are in service. 

Older box girder bridges can be cast-in-place concrete with mild steel 

reinforcement and post-tensioning reinforcement (see Figures 7.11.1, 7.11.2 and 

7.11.3). Current designs for concrete box girders typically use post-tensioning. 

Figure 7.11.1 Typical Concrete Box Girder Cross Sections 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.2

Figure 7.11.2 Cast-in-place Concrete Box Girder Bridge 

7.11.2 

Design 

Characteristics 

Concrete Box Girder For wide roadways, the box portion generally has internal webs and is referred to as a 

multi-cell box girder (see Figure 7.11.3). Concrete box girder bridges are typically 

either single span or continuous multi-span structures. Spans can have a straight or 

curved alignment and are generally in excess of 46 m (150 feet) (see Figure 7.11.4). 

The following description applies to monolithic box girder construction only. A 

detailed description of segmental concrete bridges appears later in this Topic. 

Figure 7.11.3 Multi-cell Girder: Post Tensioned 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.3

Figure 7.11.4 Cast-in-place Concrete Box Girder Bridge

 Construction Methods 

The two basic construction techniques used for cast-in-place monolithic box girders 

are high level casting and at-grade casting. 

High Level Casting 

The high level casting method employs formwork supported by falsework. This 

technique is used when the structure must cross an existing feature, such as a roadway, 

railway, or waterway (see Figure 7.11.5). 

Figure 7.11.5 High Level Casting Formwork on Falsework 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.4

At-grade Casting 

The at-grade casting method employs formwork supported by fill material or the 

existing ground. When the construction is complete, the fill beneath the bridge is 

removed. This technique is used when the structure is crossing, or is part of a new 

highway system or interchange (see Figures 7.11.6 and 7.11.7). 

Figure 7.11.6 At-grade Formwork with Post-tensioning Ducts 

Figure 7.11.7 Box Girder Bridge Construction 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.5

 Primary Members

For box girder structures, the primary member is the box girder. When a single-cell box 

girder design is used, the top flange or deck, the bottom flange, and both webs are all 

primary elements of the box girder (see Figure 7.11.8). The top flange is considered an 

integral deck component/element. 

Top flange

Bottom flange

Webs

Figure 7.11.8 Basic Components/Elements of a Concrete Box Girder

In some multi-cell box girder applications, the top flange or deck must be removable for 

future replacement. The top flange in these cases functions similarly to a composite deck 

and is in fact considered a separate deck component. Most exterior webs have higher 

stress levels than interior webs. The interior webs of the box also play a significant role 

in the box girder and help support the deck (see Figure 7.11.9). 

Construction Joints

Interior Webs

Figure 7.11.9 Replaceable Deck on a Multiple Cell Cast-in-place Box Girder 

 Steel Reinforcement 

Box girder structures use a combination of primary mild steel reinforcement and high 

strength post-tensioning steel tendons to resist tension and shear forces (see Figure 

7.11.10). 

Flexure reinforcement is provided in the top and bottom flanges of the box girder as 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.6

necessary (bottom flange at midspan in areas of positive moment and top flange over 

supports in areas of negative moment). However, because of the design span lengths, 

mild steel reinforcement does not have sufficient strength to resist all of the tension 

forces. To reduce these tensile stresses to acceptable levels, prestressing of the concrete 

is introduced through post-tensioning. Galvanized metal and polyethylene ducts are 

placed in the forms at the desired location of the tendons. When the concrete has cured 

to an acceptable strength level, the tendons are installed in the ducts, tensioned, and then 

grouted (see Figure 7.11.6). 

The top flanges or decks of precast or cast-in-place segmental boxes are often 

transversely post-tensioned. The multi-strand tendons are grouted after stressing. The 

tendons anchor in block-outs in the edges of top slab cantilever wings. These block-outs 

are then filled with concrete and covered with a traffic barrier. For precast units, the top 

flange tendons are generally tensioned and grouted in the casting yard. Wide bridges 

may have parallel twin boxes transversely post-tensioned. When this is the case, only 

about one-half of the transverse post-tensioning is stressed before shipment. The 

remainder of the post-tensioning is placed through ducts in adjacent box girders and the 

closure strip and stressed across the entire width of the bridge. 

Special “confinement” reinforcement is also required at the anchorage locations to 

prevent cracking due to the large transfer of force to the surrounding concrete (see 

Figure 7.11.11). 

Stirrups in the web are provided to resist standard beam action shear. For curved girder 

applications, torsional shear reinforcement is sometimes required. This reinforcement is 

provided in the form of additional stirrups. 

The secondary (temperature and shrinkage) reinforcing steel is oriented longitudinally in 

the deck and webs and flanges in the box girder. The primary and secondary reinforcing 

steel for the deck portion of the girder is the same as for a standard concrete deck (see 

Figure 7.11.10). 

Temperature 

and Shrinkage 

Reinforcement

High Strength 

Steel Tendons

Deck Reinforcement 

Stirrups

Figure 7.11.10 Primary and Secondary Reinforcement in a Concrete Box Girder 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.7

Figure 7.11.11 Formwork with Post-tensioning Anchorage and Spiral Anchorage 

Reinforcement 

Segmental Box 

Girder 

Many current box girders are built using segmental construction. A segmental concrete 

bridge is fabricated piece by piece. These pieces, or segments, are post-tensioned 

together during the construction of the bridge (see Figures 7.11.13 and 7.11.14). The 

superstructure can be constructed of precast concrete or cast-in-place concrete segments. 

Several characteristics are common to most segmental bridges: 

3⁄4 Used for long span bridges 

3⁄4 Used when falsework is undesirable or cost-prohibitive such as bridges over 

steep terrain or environmentally sensitive areas 

3⁄4 For most bridges, each segment is the full width and depth of the bridge; for 

very wide decks, many segmental box girders may consist of two-cell boxes or 

adjacent single boxes with a longitudinal cast-in-place concrete closure pour 

(see Figure 7.11.12) 

3⁄4 The length of the segments is determined by the construction methods and 

equipment available to the contractor 

3⁄4 Depending on the construction method, a new segment may be supported from 

previously erected segments 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.8

Figure 7.11.12 Adjacent Single Cell Boxes with Closure Pour 

Figure 7.11.13 Segmental Concrete Bridge 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.9

Figure 7.11.14 Close-up of Segment 

 Segment Configurations

The majority of concrete segmental bridges use a box girder configuration (see Figure 

7.11.15). The box girder is preferred due to the following: 

3⁄4 The top flange can be used as the roadway traffic surface (deck) 

3⁄4 The wide top and bottom flanges provide large areas to resist compression 

3⁄4 The box shape provides excellent torsional rigidity 

3⁄4 The box shape lends itself well to horizontally curved alignments 

The typical box girder section will have the following elements: 

3⁄4 Top deck/flange 

3⁄4 Bottom flange 

3⁄4 Web walls 

3⁄4 Interior web walls (multi-cell) 

Single box girder segments are usually used, although spread multiple boxes can be used 

if they are connected together by external diaphragms. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.10

Segmental Classification

Individual segments can either be cast-in-place or precast concrete. 

Cast-in-Place 

Cast-in-place segmental construction is generally performed by supporting the segment 

formwork from the previous cast segment. Reinforcement and concrete is placed and 

the segment is cured. When the newly cast segment has reached sufficient strength, it is 

post-tensioned to the previous cast segments (see Figure 7.11.15). This process 

proceeds until the bridge is completed. 

 

Figure 7.11.15 Cast-in-place Box Girder Segment 

Precast 

Precast segmental construction is performed by casting the individual segments prior to 

erecting them. The actual casting can take place near the project location or at an offsite fabrication plant. Once the precast segment is positioned adjacent to the previous 

placed segment, it is post-tensioned in the same manner as the cast-in-place segment 

previously mentioned. This process also repeats itself until the bridge is completed (see 

Figure 7.11.16). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.11

Figure 7.11.16 Box Girder Segment 

Precast construction lends itself well to repetitive operations and associated efficiencies. 

Fabrication plant operations also tend to offer higher degrees of quality control than 

field operations associated with cast-in-place construction. Precast construction must be 

monitored and controlled to ensure the proper fit in the field with regards to vertical and 

horizontal alignment. In order to control this situation, match casting is usually 

employed. Match casting utilizes the previous segment as part of the formwork for the 

next segment to ensure proper mating segments. Epoxy bonding adhesive is applied to 

the match-cast joints during initial erection. 

Cast-in-place construction frequently does not benefit from the efficiencies of precast 

construction but does have the advantage of relatively easy field adjustments for 

controlling line and grade of alignment. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.12

 Construction Methods 

Balanced Cantilever 

This form of construction requires individual segments to be placed symmetrically about 

a pier. As the segments are alternately placed about the pier, the bending moments 

induced into the pier by the cantilever segments tend to balance each other. Once the 

mid-span is reached, a closure segment is cast together with the previously erected halfspan from the adjacent pier. This procedure is repeated until all the spans have been 

erected (see Figures 7.11.17, 7.11.18 and 7.11.19). Both cast-in-place and precast 

construction is suitable for this form of construction. 

Figure 7.11.17 Balanced Cantilever Method 

Figure 7.11.18 Balanced Cantilever Construction 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.13

Figure 7.11.19 Balanced Cantilever Construction 

Span-by-span Construction 

This form of construction may require a temporary steel erection truss or falsework, 

which spans from one pier to another. The erection truss provides temporary support of 

the individual segments until they are positioned and post-tensioned into their final 

configuration. This type of construction allows a total span to be erected at one time. 

Once the span has been completed the erection truss is removed and repositioned on the 

next adjacent span. This procedure is repeated until all the spans have been erected (see 

Figures 7.11.20 and 7.11.21). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.14

Figure 7.11.20 Span-by-Span Construction (with Erection Truss) 

Figure 7.11.21 Span-by-span Close-up (with Erection Truss) 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.15

The entire span may also be assembled or cast on the ground, or on a floating barge. 

The span is raised to final position with cranes or lifting jacks and made continuous 

with the previously placed pier segments by closure pours and longitudinal posttensioning. Both cast-in-place and precast construction is suitable for this form of 

construction (see Figure 7.11.22). 

Figure 7.11.22 Span-by-span Total Span Erection (Lifting) 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.16

Progressive Placement Construction 

 

This form of construction is much like the span-by-span construction described above. 

Construction proceeds outward from a pier towards an adjacent pier and once 

completed, the process is repeated in the next span and so on until the bridge is 

completed (see Figure 7.11.23). Because of the large bending forces associated with 

this type of construction, temporary bents or erection cables tied off to a temporary 

erection tower are often employed. 

Figure 7.11.23 Progressive Placement Construction 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.17

Incremental Launching Construction 

This form of construction permits the individual segments to be fabricated or 

positioned behind an abutment, post-tensioned, and then launched forward towards an 

adjacent pier by means of hydraulic jacks. Both cast-in-place and precast construction 

is suitable for this type of construction. This process is repeated until the entire bridge 

is constructed (see Figure 7.11.24). 

Movement

Fabrication Area Launching Nose

Temporary Pier

Figure 7.11.24 Incremental Launching Method 

To aid the advancement and guide the already completed segments, a steel launching 

nose is attached to the leading segment. If the spans become very large, temporary 

bents are often used to reduce the large negative bending effects developed in the 

completed cantilever segments (see Figure 7.11.25). 

Figure 7.11.25 Incremental Launching Overview (Note Temporary Pile Bent) 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.18

7.11.3 

Overview of 

Common Defects 

Common defects that occur on concrete box girder bridges include: 

3⁄4 Cracking (flexure, shear, temperature, shrinkage, mass concrete) 

3⁄4 Scaling 

3⁄4 Delamination 

3⁄4 Spalling 

3⁄4 Chloride contamination 

3⁄4 Efflorescence 

3⁄4 Ettringite formation 

3⁄4 Honeycombs 

3⁄4 Pop-outs 

3⁄4 Wear 

3⁄4 Collision damage 

3⁄4 Abrasion 

3⁄4 Overload damage 

3⁄4 Reinforcing steel corrosion 

3⁄4 Prestressed concrete deterioration 

3⁄4 Stress corrosion of prestressing strands 

Refer to Topic 2.2 for a detailed explanation of the properties of concrete, types and 

causes of concrete deterioration, and the examination of concrete. 

7.11.4 

Inspection 

Procedures and 

Locations 

Inspection procedures to determine other causes of concrete deterioration are 

discussed in detail in Topic 2.2.8. 

Procedures Visual 

The inspection of prestressed concrete box girders for cracks, spalls, and other 

defects is primarily a visual activity. 

Physical 

Sounding by hammer can be used to detect delaminated areas. A delaminated area 

will have a distinctive hollow “clacking” sound when tapped with a hammer or 

revealed with a chain drag. A hammer hitting sound concrete will result in a solid 

“pinging” type sound. In most cases, a chain drag is used to check the top surface of 

a concrete deck. 

Since prestressed box girders are designed to limit tensile stresses in concrete to 

specified thresholds, cracks are indications of serious problems. For this reason, any 

crack should be carefully measured with an optical crack gauge or crack comparator 

card and documented. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.19

Advanced Inspection Techniques 

Several advanced techniques are available for concrete inspection. Nondestructive 

methods, described in Topic 13.2.2, include: 

3⁄4 Acoustic wave sonic/ultrasonic velocity measurements 

3⁄4 Delamination detection machinery 

3⁄4 Electrical methods 

3⁄4 Electromagnetic methods 

3⁄4 Pulse velocity 

3⁄4 Flat jack testing 

3⁄4 Ground-penetrating radar 

3⁄4 Impact-echo testing 

3⁄4 Infrared thermography 

3⁄4 Laser ultrasonic testing 

3⁄4 Magnetic field disturbance 

3⁄4 Neutron probe for detection of chlorides 

3⁄4 Nuclear methods 

3⁄4 Pachometer 

3⁄4 Rebound and penetration methods 

3⁄4 Ultrasonic testing 

3⁄4 Radiography 

Other methods, described in Topic 13.2.3, include: 

3⁄4 Core sampling 

3⁄4 Carbonation 

3⁄4 Concrete permeability 

3⁄4 Concrete strength 

3⁄4 Endoscopes and videoscopes 

3⁄4 Moisture content 

3⁄4 Petrographic examination 

3⁄4 Reinforcing steel strength 

3⁄4 Chloride test 

3⁄4 Matrix analysis 

3⁄4 ASR evaluation 

Locations 

Concrete Box Girder The inspection of a box girder bridge requires a clear understanding of the girder 

function. This requires a thorough review of design or as-built drawings prior to the 

inspection and a realization of the high stress regions in a particular structure. 

Because of the complexities of box girders, many agencies develop an inspection and 

maintenance manual for a structure, which is written by the structural designer. 

Arguably, the most important inspection a box girder will receive is the first or initial 

inspection. This inspection will serve as a benchmark for all future inspections. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.20

Since the initial inspection is so important, it should be scheduled as early as possible 

after the construction of the bridge. Because of the complex nature of the box girder, 

all surfaces on the interior and exterior of the girder require visual examination. 

Bearing Areas 

Check the bearing area for delaminations, spalls and cracks. Delaminations, spalls 

and cracks may be caused by corrosion of steel reinforcement due to water leakage or 

restriction of thermal movements. 

The effects of temperature, creep, and concrete shrinkage may produce undesirable 

conditions at the bearings. Check the bearing areas and the bearings for proper 

movement and movement capability (see Figure 7.11.26). 

Figure 7.11.26 Bearing Area of a Cast-in-place Box Girder Bridge 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.21

 Shear Zones 

Check girder ends and sections over piers for diagonal shear cracks in webs. 

These web cracks will project diagonally upward at approximately a 45 degree 

angle from the support toward midspan (see Figure 7.11.27). 

Figure 7.11.27 Box Girder Cracks Induced by Shear 

 Tension Zones 

Direct Tension - Tension cracks can appear as a series of parallel cracks running 

transverse to the longitudinal axis of the bridge. The cracks can possibly be 

through the entire depth of the box girder section. Cracks will probably be spaced 

at approximately 1 to 2 times the minimum thickness of the girder component (see 

Figure 7.11.28). 

Figure 7.11.28 Box Girder Cracks Induced by Direct Tension 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.22

Flexure - These cracks can appear in the top flange at pier locations and on the bottom 

flange at mid-span regions. The extent of cracking will depend on the intensity of the 

bending being induced. Flexure cracks will normally propagate to the neutral axis or

to an area around the half-depth of the section. Flexural cracks found in posttensioned members should be examined very carefully. This could indicate that the 

member is overstressed. Accurately identify the location of the crack, the length and 

width of the crack, and the spacing to adjacent cracks (see Figures 7.11.29 and 

7.11.30). 

Figure 7.11.29 Box Girder Cracks Induced by Flexure (Positive Moment) 

Figure 7.11.30 Box Girder Cracks Induced by Flexure (Negative Moment) 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.23

Flexure-shear - These cracks can appear close to pier support locations. They will 

begin on the bottom flange oriented transverse to the longitudinal axis of the bridge. 

The cracking will extend up the webs approximately 45 degrees to the horizontal and 

toward mid-span (see Figure 7.11.31). 

Figure 7.11.31 Box Girder Cracks Induced by Flexure-shear 

Inspect the top side of the top flange for longitudinal flexure cracking directly over 

interior and exterior girder webs. Inside the box, examine the bottom of the top flange 

for longitudinal flexure cracking between the girder webs. These longitudinal cracks 

are caused by overstressing of the deck. Any efflorescence or leakage through the top 

flange should be documented. 

The girder should be inspected throughout for flexure and shear cracks as well as 

prestress-induced cracks. Some shrinkage cracks are to be expected. Likewise, although 

post-tensioned, some small cracks may be present. As with all prestressed concrete 

members, any cracks should be carefully measured with an optical crack gauge or crack 

comparator and its location, length, width, and crack spacing documented. 

Anchor Blocks 

Anchor blocks contain the termination of the post-tensioning tendons. Very large 

concentrated loads are developed within these blocks. They have a tendency to crack if 

not properly reinforced or if there are voids adjacent to the post-tensioning tendons. 

The cracking will be more of a splitting failure in the web and would be oriented in the 

direction of the post-tensioning tendon (see Figure 7.11.32).

Secondary Members 

If there are external diaphragms between the girders, check for delaminations, spalls 

and cracking. Defects on end diaphragms may indicate differential substructure 

settlement while defects in the intermediate diaphragms may indicate excessive 

deflection in the girders. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.24

Figure 7.11.32 Web Splitting near an Anchorage Block 

 Areas Exposed to Drainage 

Examine the girder for any delaminations, spalling, or scaling which may lead to 

exposure of reinforcing steel. Areas such as joints, scuppers and curb lines exposed to 

drainage should receive special attention. 

Areas Exposed to Traffic 

Check areas damaged by collision. A significant amount of concrete box girder bridge 

deterioration and loss of section is due to traffic damage. Document the number of 

exposed tendons, the length of exposed tendons, number of severed strands, the extent 

of, as well as the loss of, concrete section. The loss of concrete due to such a collision

is not always serious, unless the bond between the concrete and steel reinforcement is 

affected. 

Inspection of the roadway surface for delaminations, cracking, spalling, and 

deformation; the presence of these defects can increase the impact effect of traffic. 

This may be of greater significance if the top flange does not have an added wearing 

surface. 

Areas Previously Repaired

Examine thoroughly any repairs that have been previously made. Determine if repaired 

areas are sound and functioning properly. Effective repairs and patching are usually 

limited to protection of exposed tendons and reinforcement. 

Miscellaneous Areas 

Cracks Caused by Torsion and Shear - This type of cracking will occur in both the 

flanges and webs of the box girder due to the twisting motion induced into the section. 

This cracking is very similar to shear cracking and will produce a helical configuration 

if torsion alone was present. Bridge structures most often will not experience torsion 

alone; rather bending, shear and torsion will occur simultaneously. In this event, 

cracking will be more pronounced on one side of the box due to the additive effects of 

all forces (see Figure 7.11.33). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.25

Figure 7.11.33 Box Girder Cracks Induced by Torsion and Shear 

Thermal Effects - These cracks are caused by non-uniform temperatures between two 

surfaces located within the box girder. Cracking will typically be transverse in the 

thinner flanges of the box and longitudinal near changes in cross section thickness (see 

Figures 7.11.34 and 7.11.35).

Figure 7.11.34 Thermally Induced Cracks in Box Girder Flanges 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.26

Figure 7.11.35 Thermally Induced Cracks at Change in Box Girder Cross Section 

Post-tensioning - Cracking can occur along any of the lines of post-tensioning tendons. 

For this reason it is important for the inspector to be aware of where tendons are 

located in the box section (see Figure 7.11.36). This cracking may be the result of a 

bent tendon, a misaligned tendon with insufficient concrete cover or voids around the 

tendons. Shrinkage of concrete adjacent to large tendons has also caused this type of 

cracking.

Figure 7.11.36 Post-tensioning Tendon Duct 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.27

Overstress - Older cast-in-place box girder interiors should be inspected to verify that 

inside forms left in place do not provide unintentional load paths, which may result in 

overloading elements of the box (see Figure 7.11.37). 

Figure 7.11.37 Interior Formwork Left in Place 

Structure Alignment - An engineering survey needs to be performed at the completion 

of construction and a schedule for future surveys established. The results of these 

surveys will aid the bridge engineer in assessing the behavior and performance of the 

bridge. Permanent survey points at each substructure and at each mid-span should be 

established. Likewise, several points need to be set at each of these locations in the 

transverse direction across the deck (see Figure 7.11.38). During the inspection, the 

inspector should: 

3⁄4 Inspect the girder for the proper camber by sighting along the fascia of the 

bottom flange. 

3⁄4 On curved box girders, check for irregularities in the superelevation of the 

flanges, which could indicate torsional distress. 

Radial Cracking - Post-tensioning tendons can be aligned vertical, horizontal or both 

depending on the vertical and horizontal geometry of the finished structure. The 

tendons produce a component of force normal to the curvature of their alignment. The 

result of this force can be cracking or spalling of the concrete components that contain 

these tendons. This type of distress is localized to the tendon in question, but can 

occur virtually anywhere along the length of the tendon. Joints of match cast precast 

segments are particularly sensitive to this type of cracking. 

Investigate unusual noises, such as banging and screeching, which may be a sign of 

structural distress. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.28

Observe and record data from any monitoring instrumentation (e.g., strain gauges, 

displacement meters, or transducers) that has been installed on or within the bridge. 

Check the condition of the drainage holes to see if they are clear and functioning 

properly. 

Observation Points

Figure 7.11.38 Location of Observation Points Across the Top Flange 

Segmental Box Girder In addition to the inspection locations and procedures for concrete box girders, there 

are several special components that are unique to segmental bridges. The bridge 

inspector should be familiar with these special components. 

Inspecting a segmental box girder bridge is similar to the procedures mentioned 

previouslyThis is described in Topic 2.2 and this format is consistent with similar 

topics. for concrete box girders, and includes the following specific procedures: 

Bearing Areas 

Due to the inherent behavior of prestressed concrete structures, the effects of 

temperature, creep and shrinkage of the concrete may produce undesirable conditions 

to the bearings. These undesirable conditions take the form of distorted elastomeric

bearings or loss of movement to mechanical bearings. Additionally, the areas where 

bearings interface with the bottom flange of the box girder need special attention. 

Large vertical forces from the superstructure are required to be transmitted to the 

bearings and, therefore, sizable bearing stresses are produced in these areas (see 

Figure 7.11.39).
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.29

Figure 7.11.39 Segmental Box Girder Bearings at Intermediate Pier 

 Shear and Tension Zones 

Inspect both the interior and the exterior surfaces of the box girder. The inspection 

procedures for shear and tension zones in segmental box girder bridges are the same as 

for concrete box girder bridges. Examples of cracking in segmental box girder bridges 

are shown in Figures 7.11.27 to 7.11.35. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.30

 Anchor Blocks 

Segmental construction relies on the tremendous post-tensioning forces to hold the 

individual segments together. Inspection of anchor blocks for segmental box girder 

bridges is the same as for concrete box girder bridges. Additionally, the inspection 

needs to focus on the box girder webs adjacent to the anchor blocks and look for the 

development of vertical cracks on either side of the anchors. Examine the condition of 

the tendons adjacent to the anchor blocks. The flange or web on which the anchor 

block is located will require attention concerning the potential for transverse cracking 

in the vicinity of the anchor (see Figures 7.11.40 and 7.11.42). 

Figure 7.11.40 Segmental Box Girder Cracks Adjacent to Anchorage Block 

 Secondary Members 

Internal diaphragms are located at abutments and piers and should receive close 

examination of the tendon anchorages located within them. The diaphragms stiffen 

the box section and distribute large bearing reaction loads. This region is highly 

stressed and should be examined closely for cracks. 

If there are external diaphragms between the girders, check for cracking and spalling. 

Defects on end diaphragms may indicate differential substructure settlement while 

defects in the intermediate diaphragms may indicate excessive deflection in the 

girders. 

Joints 

Joints should be inspected for crushing and movement of the shear keys (see Figure 

7.11.41). The presence of open or loose joints needs to be documented. Areas where 

the type of construction required closure joints or segments to be poured in place will 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.31

need close attention. These areas sometimes are regions of tendon anchorages and 

couplers. The stress concentrations in these areas are very much different than a 

section away from the anchorages where a distributed stress pattern exists (see Figure 

7.11.42). Additionally, the effects of creep and tendon relaxation are somewhat higher 

in these regions. 

Figure 7.11.41 Close-up View of Box Girder Shear Keys 

Figure 7.11.42 View of Box Girder Joint and Anchorage Block 

 Internal Diaphragms 

Internal diaphragms at the piers and abutments serve to stiffen the box section and to 

distribute the large bearing reaction loads. Tendon anchorages located within the 

Shear Keys 

Anchorage 

Block 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.32

diaphragm can also contribute to additional loads. This region of the structure is very 

highly stressed and, therefore, prone to crack development. The internal diaphragms

require close examination during inspection (see Figure 7.11.43). 

Figure 7.11.43 Box Girder Interior (End) Diaphragm 

 Areas Exposed to Drainage 

Inspection of areas exposed to drainage is the same as those for concrete box girder 

bridges. 

The joints between the segments should be closely examined for any signs of leakage 

or infiltration. 

Areas Exposed to Traffic 

Inspection of areas exposed to traffic is the same as those for concrete box girder 

bridges. 

Areas Previously Repaired 

Inspection of previous repairs is the same as those for concrete box girder bridges. 

Miscellaneous Areas 

Cracks caused by torsion and shear are the same as those for concrete box girder 

bridges. 

Thermal Effects - The effects of temperature and the appropriate inspection 

procedures to accommodate for it is the same as those for concrete box girder bridges. 

Additionally, these cracks can also occur at component changes in thickness such as 

that between a web and a flange. In this case the cracking will occur at the juncture 

between these two elements. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.33

For externally post-tensioned box girders, deviation blocks and blister blocks should 

be carefully examined for spalling and/or cracking distress (see Figure 7.11.44). 

These are points of very high stress concentrations and their integrity is essential to 

the integrity of span continuity post-tensioning. Locating and mapping areas of 

delaminations, spalling and delamination on the top flange is essential because of the 

structural importance of this component.

Figure 7.11.44 Inside View of Externally Post-tensioned Box Girder 

7.11.5 

Evaluation State and federal rating guideline systems have been developed to aid in the 

inspection of concrete superstructures. The two major rating guideline systems 

currently in use are the FHWA's Recording and Coding Guide for the Structural 

Inventory and Appraisal of the Nation's Bridges used for the National Bridge 

Inventory (NBI) component rating method and the AASHTO element level condition 

state assessment method. 

NBI Rating Guidelines Using NBI rating guidelines, a 1-digit code on the Federal Structure Inventory and 

Appraisal (SI&A) sheet indicates the condition of the superstructure. Rating codes 

range from 9 to 0, where 9 is the best rating possible. See Topic 4.2 (Items 58 and 

59) for additional details about NBI Rating Guidelines. 

The previous inspection data should be considered along with current inspection 

findings to determine the correct rating. 

Element Level 

Condition State 

Assessment 

In an element level condition state assessment of a concrete box girder bridge, the 

AASHTO CoRe element is one of the following, depending on the riding surface: 

Element No. Description

Concrete Deck 

012 Concrete Deck – Bare 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.11: Concrete Box Girders 

7.11.34

013 Concrete Deck – Unprotected with AC Overlay 

014 Concrete Deck – Protected with AC Overlay 

018 Concrete Deck – Protected with Thin Overlay 

022 Concrete Deck – Protected with Rigid Overlay 

026 Concrete Deck – Protected with Coated Bars 

027 Concrete Deck – Protected with Cathodic System 

Concrete Box Girder 

104 Prestressed Concrete Closed Web/Box Girder 

105 Reinforced Concrete Closed Web/Box Girder 

The unit quantity for the deck elements is “each”, and the entire element must be 

placed in one of the five available condition states based solely on the top surface 

condition. Some states have elected to use the total deck area (m2 or ft2). When a total 

area is used, the total area must be distributed among the five available condition 

states depending on the extent and severity of deterioration. The sum of all condition 

states must equal the total quantity of the CoRe element. The inspector must know the 

total deck surface area in order to calculate a percent deterioration and fit into a given 

condition state description. The unit quantity for the girder is meters or feet, and the 

total length must be distributed among the four available condition states depending 

on the extent and severity of deterioration. Condition state 1 is the best possible 

rating. See the AASHTO Guide for Commonly Recognized (CoRe) Structural 

Elements for condition state descriptions. 

A Smart Flag is used when a specific condition exists, which is not described in the 

CoRe element condition state. The severity of the damage is captured by coding the 

appropriate Smart Flag condition state. The Smart Flag quantities are measured as 

each, with only one each of any given Smart Flag per bridge. 

For structural cracks in the top surface of concrete bare decks, the “Deck Cracking” 

Smart Flag, Element No. 358, can be used and one of four condition states assigned. 

Do not use Smart Flag, Element No. 358, if the bridge deck/slab has any overlay 

because the top surface of the structural deck is not visible. For concrete defects on 

the underside of a deck element, the “Soffit” Smart Flag, Element No. 359, can be 

used and one of five condition states assigned. For damage due to traffic impact, the 

“Traffic Impact” Smart Flag, Element No. 362, can be used and one of three condition 

states assigned. 

Deck

Superstructure

Figure 7.11.45 Components/Elements for Evaluation 
7.12-i

Table of Contents

Section 7 ..................................................................................................................................................

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.12 Concrete Box Culverts......................................................................... 7.12.1 

 7.12.1 Introduction............................................................................. 7.12.1 

 7.12.2 Design Characteristics............................................................. 7.12.2 

 Loads on Concrete Box Culverts...................................... 7.12.2 

 Types of Box Culverts...................................................... 7.12.3 

 Cast-in-place .............................................................. 7.12.3 

 Precast........................................................................ 7.12.3 

 Steel Reinforcement ......................................................... 7.12.4 

 Primary Reinforcement.............................................. 7.12.4 

 Secondary Reinforcement.......................................... 7.12.4 

 

 7.12.3 Overview of Common Defects ............................................... 7.12.5 

 7.12.4 Inspection Procedures and Locations...................................... 7.12.5 

 Procedures ........................................................................ 7.12.5 

 Visual......................................................................... 7.12.6 

 Physical...................................................................... 7.12.6 

 Advanced Inspection Techniques .............................. 7.12.6 

 Locations .......................................................................... 7.12.7 

 Joints .......................................................................... 7.12.7 

 Slabs and Walls.......................................................... 7.12.8 

 Weep Holes................................................................ 7.12.9 

 

 7.12.5 Evaluation ............................................................................. 7.12.10 

 NBI Rating Guidelines ................................................... 7.12.10 

Element Level Condition State Assessment................... 7.12.11 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12-ii

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7.12.1

Topic 7.12 Concrete Box Culverts 

7.12.1 

Introduction One of the most common types of culverts used today is the concrete box culvert 

(see Figure 7.12.1). A box culvert has an integral bottom slab that supports the 

side walls and provides a lined channel for the water to flow. The dimensions of 

the box culvert are determined by the peak flow of the channel. Box culverts are 

used in a variety of circumstances for both small and large channel openings and 

are easily adaptable to a wide range of site conditions, including sites that require 

low profile structures. In situations where the required size of the opening is very 

large, a multi-cell box culvert can be used (see Figure 7.12.2). It is important to 

note that although a box culvert may have multiple barrels, it is still a single 

structure. The internal walls are provided to reduce the unsupported length of the 

top slab. 

Figure 7.12.1 Concrete Box Culvert 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.2

Figure 7.12.2 Multi-cell Concrete Box Culvert 

7.12.2 

Design 

Characteristics 

Loads on Concrete 

Box Culverts 

There are several basic loads applied in the design of a culvert (see Figure 7.12.3) 

and include: 

3⁄4 Dead loads (culvert self –weight) 

3⁄4 Vertical earth pressure (weight of earth such as fill and road surface) 

3⁄4 Horizontal (lateral) earth pressure 

3⁄4 Live loads (vehicular traffic, pedestrian traffic) 

Vertical

Earth

Pressure

(Dead Load)

Reaction from Supporting Rock or Soil

Vehicular Live Loads

Roadway Surface

Live Load

Distribution at

Culvert Elevation

Lateral

Earth

Pressure

Lateral

Earth

Pressure

Figure 7.12.3 Loads on a Concrete Box Culvert 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.3

For a detailed description of loads on culverts, see Topic P.3.3. 

Types of Box Culverts There are two basic types of concrete box culverts – cast-in-place and precast. 

Several factors, such as span length, vertical clearance, peak stream flow, and 

terrain, determine which type of box culvert is used. 

 Cast-in-Place

Reinforced cast-in-place (CIP) concrete culverts are typically rectangular (box) 

shaped. The rectangular shape is usually constructed with multiple cells (barrels) 

to accommodate longer spans. The major advantage of cast-in-place construction 

is that the culvert can be designed to meet the specific geometric requirements of 

the site. 

 Precast

Precast concrete box culverts are designed for various depths of cover and various 

live loads and are manufactured in a wide range of sizes. Standard box sections are 

available with spans as large as 3.7 meters (12 feet). Some box sections may have 

spans of up to 6.1 meters (20 feet) if a special design is used. 

ASTM C 1433 Precast Reinforced Concrete Box Sections for Culverts, Storm 

Drains and Sewers: Covers single-cell precast reinforced concrete box sections 

intended to be used for the construction of culverts for the conveyance of storm 

water and industrial wastes and sewage. 

Figure 7.12.4 Precast Concrete Box Culvert 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.4

Steel Reinforcement Primary Reinforcement 

The primary reinforcing steel for box culverts consists of tension and shear steel. 

Tension steel is placed transversely in the slabs and vertically in the walls. Shear 

reinforcement may be placed diagonally in each of the corners (see Figure 7.12.5). 

Single cell precast concrete box culverts may use steel welded wire for 

reinforcement. 

Secondary Reinforcement

Longitudinal temperature and shrinkage reinforcement is included in the slabs and 

the walls of box culverts. Ducts may be provided in the precast box sections for 

optional longitudinal post-tensioning of the boxes with high strength steel strands

or bars (see Figure 7.12.6). 

Temperature / Shrinkage Steel

Shear (if present)

Tension Reinforcement

(“+” Moment)

Tension Reinforcement

(“-” Moment)

Figure 7.12.5 Steel Reinforcement in a Concrete Box Culvert 

Post-tensioning Steel Ducts

Precast culverts have

the same reinforcing,

but they also have

ducts for strands

which are used for

post-tensioning when

boxes are placed.

Figure 7.12.6 Precast Box Sections with Post-tensioning Steel Ducts 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.5

7.12.3 

Overview of 

Common 

Defects 

Common defects that occur in concrete box culverts include: 

3⁄4 Cracking (flexure, shear, temperature, shrinkage, mass concrete) 

3⁄4 Scaling 

3⁄4 Delamination 

3⁄4 Spalling 

3⁄4 Chloride contamination 

3⁄4 Efflorescence 

3⁄4 Ettringite formation 

3⁄4 Honeycombs 

3⁄4 Pop-outs 

3⁄4 Wear 

3⁄4 Collision damage 

3⁄4 Abrasion 

3⁄4 Overload damage 

3⁄4 Reinforcing steel corrosion 

3⁄4 Prestressed concrete deterioration 

3⁄4 Stress corrosion of prestressing strands 

3⁄4 Embankment scour at culvert inlet and outlet 

3⁄4 Roadway settlement 

Refer to Topic 2.2 for a detailed explanation of the properties of concrete, types and 

causes of concrete deterioration, and the examination of concrete. 

7.12.4 

Inspection 

Procedures and 

Locations 

See Topic P.3 for additional discussion on inspection procedures and locations for 

culverts. 

Previous inspection reports and as-built plans, when available, should be reviewed prior 

to, and during, the field inspection. A review of previous reports will familiarize the 

inspector with the structure and make detection of changed conditions easier. Review of 

the previous inspection reports will also indicate critical areas that need special attention 

and the possible need for special equipment. 

A logical sequence for inspecting culverts helps ensure that a thorough and complete 

inspection will be conducted. In addition to the culvert components, the inspector 

should also look for high-water marks, changes in the drainage area, settlement of the 

roadway, and other indications of potential problems. In this regard, the inspection of 

culverts is similar to the inspection of bridges. 

Procedures Inspection procedures to determine other causes of concrete deterioration are discussed 

in detail in Topic 2.2.8. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.6

Visual 

The inspection of concrete for cracks, spalls, and other defects is primarily a visual 

activity. 

Physical 

Hammer sounding of the exposed concrete should be performed to determine areas of 

delamination. A delaminated area will have a distinctive hollow “clacking” sound when 

tapped with a hammer or revealed with a chain drag. A hammer hitting sound concrete 

will result in a solid “pinging” type sound. 

Advanced Inspection Techniques 

Several advanced techniques are available for concrete inspection. Nondestructive 

methods, described in Topic 13.2.2, include: 

3⁄4 Acoustic wave sonic/ultrasonic velocity measurements 

3⁄4 Delamination detection machinery 

3⁄4 Electrical methods 

3⁄4 Electromagnetic methods 

3⁄4 Pulse velocity 

3⁄4 Flat jack testing 

3⁄4 Ground-penetrating radar 

3⁄4 Impact-echo testing 

3⁄4 Infrared thermography 

3⁄4 Laser ultrasonic testing 

3⁄4 Magnetic field disturbance 

3⁄4 Neutron probe for detection of chlorides 

3⁄4 Nuclear methods 

3⁄4 Pachometer 

3⁄4 Rebound and penetration methods 

3⁄4 Ultrasonic testing 

Other methods, described in Topic 13.2.3, include: 

3⁄4 Core sampling 

3⁄4 Carbonation 

3⁄4 Concrete permeability 

3⁄4 Concrete strength 

3⁄4 Endoscopes and videoscopes 

3⁄4 Moisture content 

3⁄4 Petrographic examination 

3⁄4 Reinforcing steel strength 

3⁄4 Chloride test 

3⁄4 Matrix analysis 

3⁄4 ASR evaluation 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.7

Locations For typical installations, it is usually convenient to begin the field inspection with 

general observations of the overall condition of the structure and inspection of the 

approach roadway. The inspector should inspect the embankment, waterway, 

headwalls, wingwalls at the inlet and outlet ends, and culvert barrel. The following 

sequence is applicable to all culvert inspections: 

3⁄4 Overall condition 

3⁄4 Approach roadway and embankment settlement 

3⁄4 Waterway (see in Topic 11.2) 

3⁄4 End treatments 

3⁄4 Appurtenance structures 

3⁄4 Culvert barrel 

The following should be inspected inside the barrel of the box culvert. 

3⁄4 Joints – inspect joint locations for defects 

3⁄4 Slabs and walls – inspect slabs and walls for cracks, delaminations and spalls 

3⁄4 Weep holes 

 Joints 

 

The vertical and horizontal alignment should be checked by visual observation. Vertical 

alignment should be checked for sags or differential settlement at joints. Sags can best 

be detected during low flows by looking for areas where the water is deeper or where 

sediment has been deposited. When excessive accumulations of sediment are present, it 

may be necessary to have the sediment removed before checking for sags. An alternate 

method would be to take profile elevations of the top slab. The horizontal alignment can 

be checked by sighting along the walls and by examining joints for differential 

movement (see Figure 7.12.7). 

Figure 7.12.7 Sighting Along Culvert Sidewall to Check Horizontal Alignment 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.8

Expansion joints should be carefully inspected to verify that the filler material or joint 

sealant is in place and that the joint is not filled with incompressible material that would 

prohibit expansion (see figure 7.12.8). Spalls or cracks along joint edges are usually an 

indication that the expansion joint is full of incompressible materials or that one or more 

expansion joints are not working. Joint inspection also should identify any joints that are 

opened widely or are not open to uniform width. Water flowing or seeping into the 

culvert through open joints (infiltration) may bring with it supporting soil. Water 

flowing out of the culvert through open joints (exfiltration) may cause loss of supporting 

material. 

Figure 7.12.8 Precast Concrete Box Culvert Joint 

 Slabs and Walls 

The top slab and walls should be inspected visually for cracks and spalls. When 

either is observed, the area around the defect should be tapped with a hammer to 

detect delaminations. A ladder may be needed for inspecting the top slab. 

Longitudinal cracks (along the length of the culvert) in the top slab of box culverts 

may indicate either flexure or shear problems. Transverse cracks may indicate 

differential settlement. Longitudinal cracks may also indicate differential wall 

settlement, or structural overloading. Transverse cracks in the top slab (perpendicular 

to walls) indicate differential settlement of the culvert. Spalls may occur along the 

edges of cracks or in the concrete covering corroded reinforcing steel. Cracks in the 

sides may be caused by settlement or earth pressure. The location, width, and length 

of all cracks and spalls should be noted in the inspection report as well as crack 

spacing. 

The concrete surfaces exposed to stream flow should be checked by visual and 

physical procedures for unsound concrete due to chemical attack or abrasion. The 

bottom of the top slab, the bottom slab, and the water line on the walls are the most 

likely areas to be damaged. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.9

Figure 7.12.9 Cast in Place Concrete Box Culvert Outlet 

Figure 7.12.10 Spalls and Delaminations 

 Weep Holes 

Weep holes are often provided on the side walls and wingwalls to drain water from 

the backfill and reduce the hydraulic pressure on the side walls. Weep holes should 

be inspected to determine if they are functioning properly. Lack of flow during 

periods when flow has previously been observed may indicate blockage. Fines on the 

bottom slab also indicate improper functioning. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.10

7.12.5 

Evaluation State and federal rating guideline systems have been developed to aid in the 

inspection of concrete box culverts. The two major rating guideline systems 

currently in use are the FHWA's Recording and Coding Guide for the Structural 

Inventory and Appraisal of the Nation's Bridges used for the National Bridge 

Inventory (NBI) component rating method and the AASHTO element level condition 

state assessment method. 

NBI Rating Guidelines Using NBI rating guidelines, a 1-digit code on the Federal Structure Inventory and 

Appraisal (SI&A) sheet indicates the condition of the culvert (Item 62). This item 

evaluates the alignment, settlement, joints, structural condition, scour, and other 

items associated with culverts. Rating codes range from 9 to 0, where 9 is the best 

rating possible. See Topic 4.2 (Item 62) for additional details about NBI Rating 

Guidelines. It is also important to note that Items 58-Deck, 59-Superstructure, and 

60-Substructure should be coded “N” for all culverts. 

General NBI bridge rating guidelines are applicable but are supplemented by NBI 

guidelines created for culvert structures as well as the specific concrete box culvert 

rating guidelines shown in Figure 7.12.11. The final culvert component rating 

assigned should accurately reflect both specific and general guidelines. 

For concrete box culverts, the NBI rating guidelines yield a 1-digit code on the 

Federal (SI&A) sheet that indicates the overall condition of the culvert. The culvert 

item not only evaluates the structural condition of the culvert, but also encompasses 

the alignment, settlement in the approach roadway and embankment, joints, scour, 

and headwalls and wingwalls. Integral wingwalls are included in the evaluation up to 

the first construction or expansion joint. The 1-digit code that best describes the 

culvert’s overall condition is chosen, and the rating codes range from 9 to 0, where 9 

is the highest possible rating. 

The previous inspection data should be considered along with current inspection 

findings to determine the correct rating. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.11

Element Level 

Condition State 

Assessment 

In an element level condition state assessment of a concrete box culvert, the 

AASHTO CoRe element is: 

 

Element No. Description

241 Reinforced Concrete Culvert 

 

The unit quantity for culverts is meters or feet of culvert length along the barrel. The 

total quantity equals the culvert length times the number of barrels. The inspector 

must visually evaluate each 1 m (1 ft) slice of the culvert barrel(s) and assign the 

appropriate condition state description. The total length can be distributed among the 

four available condition states depending on the extent and severity of deterioration. 

Condition state 1 is the best possible rating. See the AASHTO Guide for Commonly 

Recognized (CoRe) Structural Elements for condition state descriptions. 

A Smart Flag is used when a specific condition exists, which is not described in the 

CoRe element condition state. The severity of the damage is captured by coding the 

appropriate Smart Flag condition state. The Smart Flag quantities are measured as 

each, with only one each of any given Smart Flag per bridge. 

Smart Flag element numbers available for use in concrete box culverts are Element 

360 “Settlement” and Element 361 “Scour”. One of the three condition states is 

chosen for each Smart Flag element that is used. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.12: Concrete Box Culverts 

7.12.12

Code Description

N Not applicable. Use if structure is not a culvert. 

9 No deficiencies. 

8 No noticeable or noteworthy deficiencies which affect the condition of the 

culvert. Insignificant scrape marks caused by drift. 

7 Shrinkage cracks, light scaling, and insignificant spalling which does not 

expose reinforcing steel. Insignificant damage caused by drift with no 

misalignment and not requiring corrective action. Some minor scouring 

has occurred near curtain walls, wingwalls, or pipes. Metal culverts have 

a smooth symmetrical curvature with superficial corrosion and no pitting. 

6 Deterioration or initial disintegration, minor chloride contamination, 

cracking with some leaching, or spalls on concrete or masonry walls and 

slabs. Local minor scouring at curtain walls, wingwalls, or pipes. Metal 

culverts have a smooth curvature, non-symmetrical shape, significant 

corrosion, or moderate pitting. 

5 Moderate to major deterioration or disintegration, extensive cracking and 

leaching, or spalls on concrete or masonry walls and slabs. Minor 

settlement or misalignment. Noticeable scouring or erosion at curtain 

walls, wingwalls, or pipes. Metal culverts have significant distortion and 

deflection in one section, significant corrosion or deep pitting. 

4 Large spalls, heavy scaling, wide cracks, considerable efflorescence, or 

opened construction joint permitting loss of backfill. Considerable 

settlement or misalignment. Considerable scouring or erosion at curtain 

walls, wingwalls, or pipes. Metal culverts have significant distortion and 

deflection throughout, extensive corrosion or deep pitting. 

3 Any condition described in Code 4 but which is excessive in scope. 

Severe movement or differential settlement of the segments, or loss of fill. 

Holes may exist in walls or slabs. Integral wingwalls nearly severed from 

culvert. Severe scour or erosion at curtain walls, wingwalls, or pipes. 

Metal culverts have extreme distortion and deflection in one section, 

extensive corrosion, or deep pitting with scattered perforations. 

2 Integral wingwalls collapsed, severe settlement of roadway due to loss of 

fill. Section of culvert may have failed and can no longer support 

embankment. Complete undermining at curtain walls and pipes. 

Corrective action required to maintain traffic. Metal culverts have 

extreme distortion and deflection throughout with extensive perforations 

due to corrosion. 

1 Bridge closed. Corrective action may put bridge back in light service. 

0 Bridge closed. Replacement necessary. 

Figure 7.12.11 NBI Condition Rating Guidelines for Culverts