7.1-i

Table of Contents

Section 7 

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.1 Cast-in-Place Slabs ................................................................................ 7.1.1 

 

 7.1.1 Introduction............................................................................... 7.1.1 

 7.1.2 Design Characteristics............................................................... 7.1.2 

 General ............................................................................... 7.1.2 

 Primary Members and Secondary Members ...................... 7.1.2 

 Steel Reinforcement ........................................................... 7.1.2 

 

 7.1.3 Overview of Common Defects ................................................. 7.1.3 

 

 7.1.4 Inspection Procedures and Locations........................................ 7.1.4 

 Procedures .......................................................................... 7.1.4 

 Visual........................................................................... 7.1.4 

 Physical........................................................................ 7.1.4 

 Advanced Inspection Techniques ................................ 7.1.4 

 Locations ............................................................................ 7.1.5 

Bearing Areas............................................................... 7.1.5 

Shear Zones.................................................................. 7.1.5 

Tension Zones.............................................................. 7.1.6 

 Secondary Members..................................................... 7.1.7 

Areas Exposed to Drainage.......................................... 7.1.7 

 Areas Exposed to Traffic ............................................. 7.1.7 

 Areas Previously Repaired........................................... 7.1.8 

 Skewed Bridges ........................................................... 7.1.8 

 7.1.5 Evaluation ................................................................................. 7.1.8 

 NBI Rating Guidelines ....................................................... 7.1.8 

 Element Level Condition State Assessment....................... 7.1.9 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1-ii

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7.1.1

Section 7 

Inspection and Evaluation of 

Common Concrete Superstructures 

Topic 7.1 Cast-in-Place Slabs 

7.1.1 

Introduction The cast-in-place slab bridge is the simplest type of reinforced concrete bridge and 

was a common choice for construction in the early 1900’s (see Figures 7.1.1 and 

7.1.2). Sometimes the terms “deck” and “slab” are used interchangeably to 

describe the same bridge component. However, this is incorrect. A deck is 

supported by a superstructure unit (beams, girders, etc.), whereas a slab is a 

superstructure unit supported by a substructure unit (abutments, piers, bents, etc.). 

A deck can be loosely defined as the top surface of the bridge, which carries the 

traffic. A slab serves as the superstructure and the top surface that carries the 

traffic. Even though slabs are defined differently than decks, many of the design 

characteristics, wearing surfaces, protective systems, inspection procedures and 

locations and, evaluation, are similar. See Topic 5.2 for further details. 

Figure 7.1.1 Typical Simple Span Cast-in-Place Slab Bridge 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.2

Figure 7.1.2 Typical Multi-span Cast-in-Place Slab Bridge 

7.1.2 

Design 

Characteristics 

General The slab bridge functions as a wide, shallow superstructure beam that doubles as 

the deck. This type of bridge generally consists of one simply supported span and 

is typically less than 9 m (30 feet) long. Simple and continuous multi-span slab 

bridges are also common. 

Primary Members and 

Secondary Members 

The only primary member in a cast-in-place slab bridge is the slab itself. There 

are no secondary members. 

Steel Reinforcement For simple spans, the slab develops only positive moment; therefore, the primary, 

or main tension reinforcement is located in the bottom of the slab. The 

reinforcement is placed longitudinally, or from support to support, parallel to the 

direction of traffic. For continuous spans, additional primary reinforcement is 

located longitudinally in the top of the slab over the piers to resist negative 

bending moments. 

Secondary reinforcement, known as temperature and shrinkage steel, is located 

transversely throughout the top and bottom of the slab. In simple span slabs, 

secondary reinforcement is also located longitudinally in the top of the slab. In 

continuous span slabs, the primary reinforcement is often placed the full structure 

length, negating the need for longitudinal secondary reinforcement. 

Nearly all slab bridges have a grid or mat of steel reinforcement in both the top 

and bottom of the slab that is formed by some combination of primary and 

secondary reinforcement (see Figure 7.1.3). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.3

Slab Section 

A-A

Elevation View

A

A

Primary Reinforcement Secondary 

Reinforcement

Figure 7.1.3 Steel Reinforcement in a Simply Supported Concrete Slab 

7.1.3 

Overview of 

Common Defects 

Common defects that occur on cast-in-place slab 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 

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. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.4

7.1.4 

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 concrete slabs for cracks, spalls, wear, and other defects is 

primarily a visual activity. 

Physical 

The physical examination of the top surface of the slab with a hammer can be a 

tedious operation. In most cases, a chain drag is used to determine delaminated 

areas. A chain drag is made of several sections of chain attached to a pipe that has 

a handle attached to it. The inspector drags this across a slab and makes note of 

the resonating sounds. 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 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.5

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, and spalling where friction 

from thermal movement and high edge or bearing pressure could overstress the 

concrete (see Figure 7.1.4). Check the condition and operation of any bearing 

devices. 

Figure 7.1.4 Bearing Area: Cast-in-Place Slab 

 Shear Zones 

Investigate areas near the supports for shear cracking. The presence of transverse 

cracks on the underside near supports or diagonal cracks on the sides of the slab 

indicate the onset of shear failure (see Figures 7.1.5 and 7.1.6). These cracks 

represent lost shear capacity and should be carefully measured. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.6

Figure 7.1.5 Shear Cracks in the Ends of a Slab Bridge 

Figure 7.1.6 Shear Zone on the Underside of a Continuous Slab Bridge Near a 

Pier

 Tension Zones 

Tension zones should be examined for flexure cracks, which would be vertical on 

the sides and transverse across the slab. The tension zones are at midspan along 

the bottom of the slab for both simple and continuous span bridges. Additional 

tension zones are located on top of the slab over the piers for continuous spans. 

Cracks greater that 2 mm (1/16 inch) wide are considered wide cracks and indicate 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.7

extreme bending stresses. 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. 

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 (see Figure 7.1.7). Slab bridges which use hooks to 

develop the primary reinforcement are not as susceptible to debonding due to 

deterioration of the concrete. 

 Secondary Members 

The slab bridge has no secondary members. 

Figure 7.1.7 Concrete Slab Tension Zone: Delamination, Efflorescence, Rust, 

and Stains 

 Areas Exposed to Drainage 

Inspect areas exposed to roadway drainage for deteriorated concrete. This 

includes the entire riding surface of the slab, particularly around scuppers or 

drains. Spalling or scaling may also be found along the curbline and fascias (see 

Figure 7.1.8).

 Areas Exposed to Traffic 

For grade crossing structures, check areas exposed to traffic for damage caused by 

collision. Such damage will generally consist of corner spalls and may include 

exposed rebars.
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.8

 Areas Previously Repaired 

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

place, and they are functioning properly.

 Skewed Bridges 

Examine skewed bridges for lateral displacement and cracking of acute corners 

due to point loading and insufficient reinforcement. 

Figure 7.1.8 Deteriorated Slab Fascia due to Roadway Deicing Agents 

7.1.5 

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

inspection of concrete bridges. 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. For a slab bridge, these guidelines 

must be applied for both the deck component and the superstructure component. 

The previous inspection data should be used along with current inspection findings 

to determine the correct rating. Typically, for this type of structure, the deck and 

superstructure components will have the same rating. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.9

Element Level Condition 

State Assessment

In an element level condition state assessment of a slab bridge, the AASHTO 

CoRe element is one of the following, depending on the riding surface: 

Element No. Description

38 Concrete Slab – Bare 

39 Concrete Slab – Unprotected with AC Overlay 

40 Concrete Slab – Protected with AC Overlay 

44 Concrete Slab – Protected with Thin Overlay 

48 Concrete Slab – Protected with Rigid Overlay 

52 Concrete Slab – Protected with Coated Bars 

53 Concrete Slab – Protected with Cathodic System 

The unit quantity for these 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 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 slab surface area in order to calculate a percent deterioration 

and fit into a given condition state description. 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 slabs, 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 slab has any overlay because 

the top surface of the structural slab is not visible. For concrete defects on the 

underside of a slab element, the “Soffit” Smart Flag, Element No. 359, can be used 

and one of five condition states assigned. This Smart Flag is particularly useful if 

the wearing surface inhibits inspection of the top surface of the slab. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.1: Cast-in-Place Slabs 

7.1.10

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7.2-i

Table of Contents

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

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.2 Tee Beam ............................................................................................... 7.2.1 

 

 7.2.1 Introduction............................................................................... 7.2.1 

 

 7.2.2 Design Characteristics............................................................... 7.2.1 

 General.............................................................................. 7.2.1 

 Primary Members and Secondary Members..................... 7.2.3 

 Steel Reinforcement.......................................................... 7.2.4 

 

 7.2.3 Overview of Common Defects ................................................. 7.2.5 

 

 7.2.4 Inspection Procedures and Locations........................................ 7.2.5 

 Procedures......................................................................... 7.2.5 

Visual ......................................................................... 7.2.5 

Physical ...................................................................... 7.2.5 

 Advanced Inspection Techniques............................... 7.2.6 

 Locations........................................................................... 7.2.7 

Bearing Areas............................................................. 7.2.7 

Shear Zones................................................................ 7.2.8 

Tension Zones ............................................................ 7.2.9 

Secondary Members................................................. 7.2.11 

Areas Exposed to Drainage ...................................... 7.2.12 

Areas Exposed to Traffic.......................................... 7.2.13 

Areas Previously Repaired....................................... 7.2.14 

 7.2.5 Evaluation ............................................................................... 7.2.15 

 NBI Rating Guidelines.................................................... 7.2.15 

 Element Level Condition State Assessment ................... 7.2.15 
ECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beam 

7.2-ii

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7.2.1

Topic 7.2 Tee Beams 

7.2.1 

Introduction The concrete tee beam, a predominant bridge type during the 1930’s and 1940’s, 

is generally a cast-in-place monolithic deck and stem system formed in the shape 

of the letter "T" (see Figure 7.2.1). 

The cast-in-place tee beam is the most common type of tee beam. However, 

precast tee beam shapes are used by some highway agencies. Types of precast tee 

beams include bulb tee, double tee, quad tee, and rib tee (see Topic 7.8, 

Prestressed Double Tee Beams). 

Recent technology has also produced the inverted tee beam, a new type of precast 

tee beam, for short to medium span bridges. Developed in Nebraska, this 

prestressed concrete beam reduces the weight up to 20% compared to conventional 

I-beams and eliminates the need for falsework construction. 

Figure 7.2.1 Simple Span Tee Beam Bridge 

7.2.2 

Design 

Characteristics 

General Care must be taken not to describe tee beam bridges as composite. They do not 

meet the definition of composite, because the deck and stem are constructed of the 

same material. The deck portion of the beam is constructed to act integrally with 

the stem, providing greater stiffness and allowing increased span lengths (see 

Figure 7.2.2). The tee beam bridge is used for spans between 9 and 15 m (30 and 

50 feet). Simple spans are most common; however, there are some multi-span 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.2

continuous tee beam bridges in use. 

Superstructure

(Deck & Stem)

Flange

(Deck)

Stem

Optional Wearing 

Surface

Diaphragm

Figure 7.2.2 Tee Beam Cross Section 

Spacing of the tee beams is generally 900 to 2400 mm (3 to 8 feet), center-tocenter of beam stems. The depth of the stems is generally 450 to 600 mm (18 to 

24 inches). Simple span design was most common but continuous span designs 

were popular in some regions (see Figure 7.2.2). A 75 or 100 mm (3 or 4 inch) 

fillet at the deck-stem intersection identifies this older form of construction. 

Figure 7.2.3 Typical Tee Beam Layout

The inspector should be careful not to mistake a concrete encased steel I-beam 

bridge for a tee beam bridge. A review of the structure file should eliminate this 

problem. If necessary, a dimensional evaluation will show the encased steel beams 

to be smaller in size (see Figure 7.2.4). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.3

(30" – 40") 

760 mm – 1015 mm 

(12" – 24") 

305 mm – 610 mm 

Figure 7.2.4 Comparison Between Tee Beam and Concrete Encased Steel Ibeam 

Figure 7.2.5 Concrete Encased Steel I-beam 

Primary Members and 

Secondary Members 

The primary members of a tee beam bridge are the tee beam stem (web) and deck

(flange) (see Figure 7.2.6). 

Diaphragms are the only secondary members on a cast-in-place tee beam bridge. 

End diaphragms support the free edge of the beam flanges. Intermediate 

diaphragms may also be present in longer span bridges and are usually located at 

the half or third points along the span. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.4

Figure 7.2.6 Tee Beam Primary and Secondary Members 

Steel Reinforcement The primary reinforcing steel consists of main tension reinforcement and shear 

reinforcement or stirrups. The main tension reinforcement is located in the bottom 

of the beam stem and oriented longitudinally (see Figure 7.2.7). If the concrete tee 

beams are continuous, there will be longitudinal reinforcement close to the top 

surface of the deck over the piers. The sides of the stem contain primary vertical 

shear reinforcement, called stirrups, and are located throughout the length of the 

stem at various spacings required by design. Stirrups are generally U-shaped bars 

and run transversely across the bottom of the stem (see Figure 7.2.7). The need 

for stirrups is greatest near the beam supports where shear stresses are the highest. 

The secondary (temperature and shrinkage) reinforcing steel for the stem is 

oriented longitudinally in the sides (see Figure 7.2.7). The primary and secondary 

reinforcing steel for the deck portion of the beam is the same as for a standard 

concrete deck (see Figure 7.2.7). 

Deck Shear 

Reinforcement

Deck Tension 

Reinforcement

Temperature/

shrinkage 

Reinforcement

Stirrups

Stem Tension 

Reinforcement

Figure 7.2.7 Steel Reinforcement in a Concrete Tee Beam 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.5

7.2.3 

Overview of 

Common Defects 

Common defects that occur on concrete 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 

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. 

7.2.4 

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 concrete tee beams for cracks, spalls, and other defects is 

primarily a visual activity. 

Physical 

The physical examination of a tee beam with a hammer can be a tedious operation. 

In most cases, a chain drag is used to determine delaminated areas on the top 

surface. The inspector drags this across a deck and makes note of the resonating 

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

TOPIC 7.2: Tee Beams 

7.2.6

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 7.2: Tee Beams 

7.2.7

Locations Bearing Areas 

Examine bearing areas for cracking, delamination and 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 (see Figures 7.2.8 through 7.2.11). 

Figure 7.2.8 Bearing Area of Typical Cast-in-Place Concrete Tee Beam Bridge 

Figure 7.2.9 Spalled Tee Beam End 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.8

Figure 7.2.10 Deteriorated Tee Beam Bearing Area

Figure 7.2.11 Steel Bearing Supporting a Cast-in-Place Concrete Tee Beam 

 Shear Zones 

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

TOPIC 7.2: Tee Beams 

7.2.9

Figure 7.2.12 Shear Zone of Cast-in-Place Concrete Tee Beam Bridge 

 Tension Zones 

Tension zones should be examined for flexure cracks, which would be vertical on 

the sides and transverse across the bottom of the stem (see Figure 7.2.13). 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 for continuous spans (see Figure 7.2.14). Cracks greater that 2 mm (1/16 

inch) wide are considered wide cracks and indicate extreme bending stresses. 

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

rust stains from the reinforcing steel (see Figure 7.2.15). 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 Figure 7.2.16). 

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 (see Figures 7.2.15 and 7.2.16). 

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

rust stains from the reinforcing steel. In severe cases, the reinforcing steel and any 

lap splices may become exposed due to spalling. Document the remaining cross 

section of reinforcing steel since section loss will decrease live load capacity. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.10

Figure 7.2.13 Flexure Cracks on a Tee Beam 

Figure 7.2.14 Flexure Cracks in Tee Beam Deck
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.11

Figure 7.2.15 Stem of a Cast-in-Place Concrete Tee Beam with Contaminated 

Concrete 

Figure 7.2.16 Spall on the Bottom of the Stem of a Cast-in-Place Tee Beam with 

Corroded Main Steel Exposed 

 Secondary Members 

The diaphragms should be inspected for flexure and shear cracks, as well as for 

typical concrete defects. Defects in the diaphragms may be an indication of 

differential settlement of the substructure or differential deflection of stems of the 

tee beams. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.12

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 

(see Figure 7.2.17). 

Check around scuppers or drain holes and deck or stem fascias for deteriorated 

concrete (see Figure 7.2.18). 

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

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

(see Figure 7.2.19). 

Figure 7.2.17 Asphalt Covered Tee Beam Deck 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.13

Figure 7.2.18 Deteriorated Tee Beam Stem Adjacent to Drain Hole 

Figure 7.2.19 Deteriorated Tee Beam End Due to Drainage 

 Areas Exposed to Traffic 

Check areas damaged by collision. Document the number of exposed and severed 

reinforcing bars with section loss as well as the spalled and delaminated concrete. 

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 7.2.20). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.14

Figure 7.2.20 Collision Damage to Tee Beam Bridge Over a Highway

 Areas Previously Repaired 

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

place, and if they are functioning properly. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.15

7.2.5 

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

inspection of concrete bridges. 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 used along with current inspection findings 

to determine the correct rating. For concrete tee beams, 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 tee beam bridge, the AASHTO 

CoRe element is one of the following, depending on the riding surface: 

Element No. Description

Concrete Deck 

12 Concrete Deck – Bare 

13 Concrete Deck– Unprotected with AC Overlay 

14 Concrete Deck – Protected with AC Overlay 

18 Concrete Deck – Protected with Thin Overlay 

22 Concrete Deck – Protected with Rigid Overlay 

26 Concrete Deck – Protected with Coated Bars 

27 Concrete Deck – Protected with Cathodic System 

Concrete Open Girder/Beam 

110 Concrete Open Girder/Beam 

The unit quantity for the deck elements is “each”, and for the tee beam it is linear 

meters or feet. 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 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.2: Tee Beams 

7.2.16

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 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. This Smart Flag is particularly 

useful if the wearing surface inhibits inspection of the top surface of the deck. 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. 

Deck

Superstructure

Figure 7.2.21 Components/Elements for Evaluation 
7.3-i

Table of Contents

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

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.3 Concrete Girders .................................................................................... 7.3.1 

 7.3.1 Introduction............................................................................... 7.3.1 

 7.3.2 Design Characteristics............................................................... 7.3.2 

 General ............................................................................... 7.3.2 

 Primary Members and Secondary Members ...................... 7.3.3 

 Steel Reinforcement ........................................................... 7.3.3 

 

 7.3.3 Overview of Common Defects ................................................. 7.3.4 

 

7.3.4 Inspection Procedures and Locations........................................ 7.3.5 

 Procedures .......................................................................... 7.3.5 

 Visual........................................................................... 7.3.5 

 Physical........................................................................ 7.3.5 

 Advanced Inspection Techniques ................................ 7.3.5 

Locations ............................................................................ 7.3.6 

 Bearing Areas............................................................... 7.3.6 

 Shear Zones.................................................................. 7.3.6 

 Tension Zones.............................................................. 7.3.6 

 Secondary Members..................................................... 7.3.7 

 Areas Exposed to Drainage.......................................... 7.3.8 

 Areas Exposed to Traffic ............................................. 7.3.9 

 Areas Previously Repaired........................................... 7.3.9 

 

 7.3.5 Evaluation ................................................................................. 7.3.9 

 NBI Rating Guidelines ....................................................... 7.3.9 

 Element Level Condition State Assessment....................... 7.3.9 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3-ii

This page intentionally left blank 
7.3.1

Topic 7.3 Concrete Girders 

7.3.1 

Introduction Concrete girder bridges generally consist of cast-in-place monolithic decks 

supported by a two girder system. Concrete girders can be used as deck girders, 

where the deck is cast on top of the girders (Figure 7.3.1), or as through girders, 

where the deck is cast between the girders (see Figure 7.3.2). Through girders are 

very large in appearance and actually serve as the bridge’s parapets, as well as the 

main supporting members. Many of the concrete deck and through girder bridges 

in service today were built in the 1940’s. 

Figure 7.3.1 Concrete Deck Girder Bridge 

Figure 7.3.2 Concrete Through Girder Bridge 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3.2

7.3.2 

Design 

Characteristics 

General For the purpose of inspection, the deck does not contribute to the strength of the 

girders and serves only to distribute traffic loads to the girders. As such, the 

superstructure condition rating is not affected by the condition of the deck. If 

floorbeams or stringers are present, they are considered part of the superstructure

(see Figure 7.3.3). 

Figure 7.3.3 Concrete Deck Girder, Underside View 

Concrete through girders are used for spans ranging from 9 to 18 m (30 to 60 feet) 

at locations with a limited under-clearance (see Figure 7.3.4). They are, however, 

not economical for wide roadways and are usually limited to about 7 m (24-foot) 

width. Girders are usually 450 to 760 mm (18 to 30 inches) wide and 1220 to 

1830 mm (4 to 6 feet) deep. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3.3

Figure 7.3.4 Concrete Through Girder Elevation View 

Care must be taken not to describe concrete girder bridges as composite. They do 

not meet the definition of composite because the concrete girders and deck consist 

of the same material, even though they are rigidly connected with rebars. 

In a deck girder as well as a through girder structure, the live loads from the 

roadway surface are carried to the girders through the deck. The girders in turn 

carry the loads to the substructure. 

Primary Members and 

Secondary Members 

The primary members of a girder bridge are the girders, floorbeams and stringers 

(if present) and the deck. The secondary members consist of diaphragms or struts. 

Steel Reinforcement The primary reinforcing steel consists of main longitudinal reinforcement and 

shear reinforcement or stirrups. The main tension reinforcement is located in the 

bottom of the girder (positve moment) and on the top (negative moment). The 

beam also contains shear reinforcement, called stirrups that are located throughout 

the girder length. A single stirrup is generally two U-shaped bars that run 

transversely across the top, bottom and sides of the girder (see Figure 7.3.5). The 

need for stirrups is greatest near the beam supports where shear stresses are the 

highest. 

The secondary (temperature and shrinkage) reinforcing steel is oriented 

longitudinally in the sides of the girders (see Figure 7.3.5). The primary and 

secondary reinforcing steel for the deck portion of the beam is the same as for a 

standard concrete deck. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3.4

Elevation

Girder Tension 

Reinforcement

Girder Shear 

Reinforcement 

Stirrups

Figure 7.3.5 Steel Reinforcement in a Concrete Through Girder 

7.3.3 

Overview of 

Common Defects 

Common defects that occur on concrete 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 

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. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3.5

7.3.4 

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 concrete girders for cracks, spalls, and other defects is primarily 

a visual activity. 

Physical 

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

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

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 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3.6

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 girder near the bearing seat. Check the condition and operation 

of any bearing devices (see Figure 7.3.6). 

Figure 7.3.6 Bearing Area of a Through Girder Bridge 

 Shear Zones 

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

presence of transverse cracks on the underside of the girders or diagonal cracks on 

the sides of the girders indicate the onset of shear failure. These cracks indicate 

extreme shear stresses and should be carefully measured and documented.

 Tension Zones 

Tension zones should be examined for flexure cracks, which would be vertical on 

the sides and transverse across the girder and possibly the deck. The tension zones 

are at the midspan along the bottom of the through girders and possibly the deck 

for both simple and continuous span bridges (see Figure 7.3.7). Additional tension 

zones are located along the top of the girders and possibly the deck over the piers 

for continuous spans. Cracks greater that 2 mm (1/16 inch) wide are considered 

wide cracks and indicate extreme bending stresses. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3.7

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. 

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

rust stains from the reinforcing steel. In severe cases, the reinforcing steel and any 

lap splices may become exposed and debonded from the surrounding concrete due 

to spalling (see Figure 7.3.8). Document loss of bonding between reinforcement 

and concrete, section loss of concrete and remaining cross section of reinforcing 

steel since section loss and any debonding will decrease live load capacity. 

Figure 7.3.7 Typical Elevation View of a Through Girder Bridge with Tension 

Zones Indicated 

 Secondary Members 

The diaphragms should be inspected for flexural and shear cracks, as well as for 

typical concrete defects. Defects in the diaphragms may be an indication of 

differential settlement of the substructure or differential deflection of the concrete 

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

TOPIC 7.3: Concrete Girders 

7.3.8

Figure 7.3.8 Exposed Reinforcement in a Through Girder (under hammer)

 Areas Exposed to Drainage 

Inspect areas exposed to drainage. These areas will usually be at any joints or 

around the scuppers. Look for contamination due to deicing agents on the interior 

face of through girders (see Figure 7.3.9). Check around drain holes for 

deterioration of girder concrete. 

Figure 7.3.9 Close-up of an Interior Face of a Through Girder with Heavy 

Scaling due to Deicing Agents 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3.9

 Areas Exposed to Traffic 

Check areas damaged by collision. Document the number of exposed and severed 

reinforcing bars with section loss as well as the spalled and delaminated concrete. 

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

between the concrete and steel reinforcement is affected. 

 Areas Previously Repaired 

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

place and if they are functioning properly. 

7.3.5 

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

inspection of concrete bridges. 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 concrete girder bridge, the 

AASHTO CoRe element is: 

Element No. Description

110 Concrete Open Girder/beam 

116 Concrete Stringer 

155 Concrete Flooream 

The unit quantity for the girder/beam, floorbeam or stringer 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. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.3: Concrete Girders 

7.3.10

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7.4-i

Table of Contents

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

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.4 Concrete Channel Beams....................................................................... 7.4.1 

 7.4.1 Introduction............................................................................... 7.4.1 

 7.4.2 Design Characteristics............................................................... 7.4.2 

 General ............................................................................... 7.4.2 

 Primary Members and Secondary Members ...................... 7.4.2 

 Steel Reinforcement ........................................................... 7.4.2 

 

 7.4.3 Overview of Common Defects ................................................. 7.4.4 

 

 7.4.4 Inspection Procedures and Locations........................................ 7.4.4 

 Procedures .......................................................................... 7.4.4 

 Visual........................................................................... 7.4.4 

 Physical........................................................................ 7.4.4 

 Advanced Inspection Techniques ................................ 7.4.5 

 Locations ............................................................................ 7.4.5 

 Bearing Areas............................................................... 7.4.5 

 Shear Zones.................................................................. 7.4.5 

 Tension Zones.............................................................. 7.4.6 

 Secondary Members..................................................... 7.4.6 

 Areas Exposed to Drainage.......................................... 7.4.7 

 Areas Exposed to Traffic ............................................. 7.4.9 

 Areas Previously Repaired......................................... 7.4.10 

 

 7.4.5 Evaluation ............................................................................... 7.4.10 

 NBI Rating Guidelines ..................................................... 7.4.10 

 Element Level Condition State Assessment..................... 7.4.10 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4-ii

This page intentionally left blank 

 
7.4.1

Topic 7.4 Concrete Channel Beams 

7.4.1 

Introduction In appearance, the channel beam bridge resembles the tee beam bridge because the 

stems of the adjacent channel beams extend down to form a single stem (see 

Figures 7.4.1 and 7.4.2). The channel beam can either be pre-cast or cast-in-place.

Figure 7.4.1 Underside View of Precast Channel Beam Bridge 

Figure 7.4.2 Underside View of a Cast-in-Place Channel Beam Bridge 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.2

7.4.2 

Design 

Characteristics 

General Channel beams are usually found on spans up to 15 m (50 ft). 

Channel beams are generally precast and consist of a mildly reinforced deck cast 

monolithically with two stems 900 to 1200 mm (3 to 4 feet) apart (see Figure 

7.4.1). Precast channel beams may be conventionally reinforced or may be 

prestressed. Stem tie bolts (see Figure 7.4.1) and shear keys (see Figure 7.4.4) are 

used to achieve monolithic action between precast channel beams. 

Channel beams can also be cast-in-place with a curved underbeam soffit 

constructed over U-shaped beam forms (see Figure 7.4.2). 

Figure 7.4.3 General View of a Precast Channel Beam Bridge 

Primary and Secondary 

Members 

The primary members of channel beam bridges are the channel beams. The 

secondary members of channel beam bridges are the diaphragms. 

Steel Reinforcement Reinforcement cover for older channel beam bridges is often less than today’s 

cover requirements. Air entrained concrete was not specified in cast-in-place 

channel beams fabricated in the 1940’s and early 1950’s, and concrete was often 

poorly consolidated. 

The primary reinforcing steel consists of stem tension reinforcement and shear 

reinforcement or stirrups. The tension reinforcement is located in the bottom of 

the channel stem and oriented longitudinally. The tension steel reinforcement in 

current channel beams consists of either mild reinforcing bars or prestressing 

strands. The sides of the stems are reinforced with stirrups. The stirrups are 

located vertically in the sides of the channel stems at various spacings throughout 

the length and closer near the beam supports. The need for stirrups is greatest near 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.3

the beam supports where the shear stresses are the highest. 

The primary reinforcing steel for the deck portion of the beam is located in the 

bottom of the deck and is placed transversely, or perpendicular to the channel 

stems (see Figure 7.4.4). 

The secondary (temperature and shrinkage) reinforcing steel is oriented 

longitudinally in the sides of deep channel stems and longitudinally in the deck. 

The primary and secondary reinforcing steel for the deck portion of the beam is the 

same as for a standard concrete deck (see Figure 7.4.4). 

Channel Beam 

Cross Section

Tension 

Reinforcement

(Stem)

Stirrups

Temperature/

Shrinkage Steel

Tension Reinforcement

(Deck)

Shear Key

Figure 7.4.4 Cross Section of a Typical Channel Beam 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.4

7.4.3 

Overview of 

Common Defects 

Common defects that occur on concrete channel 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 

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. 

7.4.4 

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 concrete channel 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 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 7.4: Concrete Channel Beams 

7.4.5

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 

Inspect 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.

 Shear Zones 

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

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

the stems indicate the onset of shear failure. These cracks indicate extreme shear 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.6

stresses and should be carefully measured and documented. 

 Tension Zones 

Superstructure tension zones should be examined for flexure cracks, which would 

be vertical on the sides and transverse across the bottom of the stem. 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 for continuous spans. 

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

longitudinal direction. 

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. These could occur on both the concrete stems and the 

deck. 

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 and debonded from the surrounding concrete due to spalling. 

Document loss of bonding between reinforcement and concrete, section loss of 

concrete and remaining cross section of reinforcing steel since section loss and any 

debonding will decrease live load capacity. Check for evidence of sagging or 

camber loss (see Figure 7.4.5). 

Figure 7.4.5 Excessive Deflection at Midspan

 Secondary Members 

The diaphragms (See Figure 7.4.10) should be inspected for flexural and shear 

cracks, as well as for typical concrete defects. Defects in the diaphragms may be 

an indication of differential settlement of the substructure or differential deflection 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.7

of the concrete channel beams.

 Areas Exposed to Drainage 

Inspect the seam or joint between adjacent precast beams for leakage. Leakage 

generally indicates a broken shear key between the channel beams (see Figure 

7.4.6). If signs of leakage are present between beams, the shear keys should be 

observed closely for differential channel beam deflection under live load (see 

Figure 7.4.7). Also, check beam ends for concrete deterioration due to leaking 

joints. 

Examine areas exposed to drainage. Look for spalls and contamination at the ends 

and edges of the channel beams, scuppers, drain holes, and the curb line. 

Check the stem tie-bolts for tightness and corrosion (see Figures 7.4.8 and 7.4.9).

Do not confuse signs of corrosion with the epoxy used for the bolt. 

Figure 7.4.6 Joint Leakage Between Channel Beams
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.8

Figure 7.4.7 Top of Deck View of Precast Channel Beam Bridge

Figure 7.4.8 Stem Tie-bolts

Grouted Shear Keys 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.9

Figure 7.4.9 Close-up of Stem Tie-bolt (Epoxy Resin) 

Figure 7.4.10 Close-up of Diaphragm 

 Areas Exposed to Traffic 

Check areas damaged by collision. Document the number of exposed and severed 

reinforcing bars with section loss, as well as the spalled and delaminated concrete. 

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

between the concrete and steel reinforcement is affected. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.10

 Areas Previously Repaired 

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

place, and if they are functioning properly. 

7.4.5 

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

inspection of concrete bridges. 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. For concrete channel beams, the deck 

condition influences the superstructure component rating (see figure 7.4.11). 

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 concrete channel beam bridge, 

the AASHTO CoRe element is: 

Element No. Description

Concrete Deck 

12 Concrete Deck – Bare 

13 Concrete Deck– Unprotected with AC Overlay 

14 Concrete Deck – Protected with AC Overlay 

18 Concrete Deck – Protected with Thin Overlay 

22 Concrete Deck – Protected with Rigid Overlay 

26 Concrete Deck – Protected with Coated Bars 

27 Concrete Deck – Protected with Cathodic System 

Concrete Open Girder/Beam 

110 Concrete Open Girder/beam 

109 Prestressed Concrete Open Girder/beam 

The unit quantity for the deck elements is “each”, and for the channel beam it is 

linear meters or feet. 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 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.11

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 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. This Smart Flag is particularly 

useful if the wearing surface inhibits inspection of the top surface of the deck. 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. 

Deck

Superstructure

Figure 7.4.11 Components/Elements for Evaluation 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.4: Concrete Channel Beams 

7.4.12

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7.5-i

Table of Contents

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

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.5 Concrete Arches and Arch Culverts....................................................... 7.5.1 

 

 7.5.1 Introduction............................................................................. 7.5.1 

 

 7.5.2 Design Characteristics............................................................. 7.5.1 

 General ............................................................................... 7.5.1 

 Open Spandrel Arch..................................................... 7.5.1 

 Closed Spandrel Arch .................................................. 7.5.2 

 Through Arch............................................................... 7.5.2 

 Precast Arch................................................................. 7.5.3 

 Arch Culvert................................................................. 7.5.5 

 Primary and Secondary Members ...................................... 7.5.6 

 Open Spandrel Arch..................................................... 7.5.6 

 Closed Spandrel Arch .................................................. 7.5.7 

 Concrete Arch Culverts................................................ 7.5.8 

 Steel Reinforcement ........................................................... 7.5.8 

 Open Spandrel Arch..................................................... 7.5.8 

 Closed Spandrel Arch .................................................. 7.5.9 

 Arch Culvert............................................................... 7.5.10 

 Other Reinforcement.................................................. 7.5.10 

 

 7.5.3 Overview of Common Defects ............................................. 7.5.10 

 

 7.5.4 Inspection Procedures and Locations.................................... 7.5.11 

 Procedures ........................................................................ 7.5.11 

 Visual......................................................................... 7.5.11 

 Physical...................................................................... 7.5.11 

 Advanced Inspection Techniques .............................. 7.5.11 

 Locations .......................................................................... 7.5.12 

 Open and Closed Spandrel Arches............................. 7.5.12 

 Bearing Areas...................................................... 7.5.12 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5-ii

 Shear Zones ......................................................... 7.5.13 

 Tension Zones ..................................................... 7.5.13 

 Compression Zones ............................................. 7.5.14 

 Secondary Members............................................ 7.5.15 

 Areas Exposed to Drainage ................................. 7.5.15 

 Areas Exposed to Traffic..................................... 7.5.16 

 Areas Previously Repaired .................................. 7.5.16 

 Concrete Arch Culverts.............................................. 7.5.16 

 

 7.5.5 Evaluation ............................................................................. 7.5.17 

 NBI Rating Guidelines ..................................................... 7.5.17 

 Element Level Condition State Assessment..................... 7.5.17 
7.5.1

Topic 7.5 Concrete Arches and Arch Culverts 

7.5.1 

Introduction A true arch has an elliptical shape and functions in a state of pure axial 

compression. It can be thought of as a long curved column. This makes the true 

arch an ideal form for the use of concrete. Unfortunately, the true arch form is 

often compromised to adjust for a specific bridge site. Because of this 

compromise, modern concrete arch bridges resist a load combination of bending 

moments, and shear in addition to axial compression. 

7.5.2 

Design 

Characteristics 

The basic design concept in arch construction utilizes a "building block" approach. 

Arch elements, although connected, are stacked or "bearing" on top of one another. 

The elements at the bottom of the pile receive the largest compressive loads due to 

the weight of the elements above. Arch spans are always considered "simple 

span" designs because of the basic arch function. 

General Open Spandrel Arch 

The open spandrel concrete arch is considered a deck arch since the roadway is 

above the arches. The area between the arches and the roadway is called the 

spandrel. 

Open spandrel concrete arches receive traffic loads through spandrel bents that 

support a deck or tee beam floor system (see Figure 7.5.1). This type of arch is

generally for 61 m (200 feet) and longer spans. 

Figure 7.5.1 Open Spandrel Arch Bridge 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.2

Closed Spandrel Arch 

Closed spandrel arches are deck arches. The spandrel area (i.e., the area between 

the arch and the roadway) is occupied by fill retained by vertical walls. The arch 

member is called a ring or barrel and is continuous between spandrel walls. 

Closed spandrel arches receive traffic loads through the fill material which is 

contained by spandrel walls (see Figure 7.5.2). This type of arch is efficient in 

short span applications. 

Figure 7.5.2 Multi-span Closed Spandrel Arch Bridge 

A closed spandrel arch with no fill material has a hollow vault between the 

spandrel walls. This type of arch has a floor system similar to the open spandrel 

arch and should be inspected accordingly. 

Through Arch 

A concrete through arch is constructed having the crown of the arch above the 

deck and the arch foundations below the deck. Hangers or cables suspend the deck 

from the arch. Concrete through arches are very rare (see Figure 7.5.3). These 

types of arches are sometimes referred to as “Rainbow Arches”. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.3

Figure 7.5.3 Concrete Through Arch Bridge 

Precast Arch 

Precast concrete arches are gaining popularity and can be integral or segmental. 

The integral arches typically have an elliptical barrel with vertical integral sides 

(see Figure 7.5.4). Segmental arches are oval or elliptical and can have several 

hinges along the arch (see Figure 7.5.5). The hinges allow for rotation and 

eliminate the moment at the hinge location. Both integral and segmental precast 

arch sections are bolted or post-tensioned together perpendicular to the arch. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.4

Figure 7.5.4 Precast Concrete Arch with Integral Vertical Legs 

Figure 7.5.5 Precast Segmental Concrete Arch

Large segmental precast arches that are post-tensioned have the ability to span 

great distances. This type of arch is constructed from the arch foundations to the 

crown using segmental hollow sections. The segmental sections are posttensioned together along the arch through post-tensioning ducts placed around the 

perimeter of the segmental section. For this type of design, the deck and 

supporting members bear on the top or crown of the arch (see Figure 7.5.6). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.5

High quality control can be obtained for precast arches. Sections are precast in a 

casting yard which allows manufacturers to properly monitor the concrete 

placement and curing. Reinforcement clearances and placement is also better 

controlled in a casting yard. Precast sections are typically tested prior to gaining 

acceptance for use. This ensures that the product can withstand the required loads 

that are applied. 

Figure 7.5.6 Precast Post-tensioned Concrete Arch without Spandrel Columns 

Arch Culvert 

Although concrete arch culverts look like and experience most of the same defects 

as concrete arch bridges, concrete arch culverts are separate from concrete arch 

bridges due to hydraulic, structural, maintenance, traffic safety, construction, 

durability, and inspection differences. An arch culvert is a curved shaped culvert 

that works primarily in compression. A variation of the arch culvert is the tied 

arch culvert. It is basically the same as the arch culvert, but it has an integral floor 

serving as a tie between the ends of the arch. Concrete arch culverts can be cast-inplace or precast. Unlike arch bridges, arch culverts are designed to flow full at 

peak flows. Also, the embankment material surrounding an arch culvert is more 

important than the embankment material around an arch bridge. These differences 

plus others require special attention to be given to culverts (see Figures 7.5.7 and 

7.5.8). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.6

Figure 7.5.7 Concrete Arch Culvert 

Designed for 

Normal Flow

C Road L

Contained Fill

Roadway 

Passes 

Through 

Headwalls

Closed Spandrel Arch

Designed for 

Peak Flow

C Road L

Headwall

Below 

Roadway Structure is 

Under Fill

Arch Culvert 

Figure 7.5.8 Closed Spandrel Arch versus Arch Culvert 

Primary Members and 

Secondary Members 

Open Spandrel Arch 

The reinforced concrete open spandrel arch consists of one or more arch ribs. The 

arch members are the primary load-carrying elements of the superstructure. The 

arch and the following members supported by the arch are also considered primary 

superstructure elements: 

3⁄4 Spandrel bents - support floor system 

3⁄4 Spandrel bent cap - transverse beam member of the spandrel bent 

3⁄4 Spandrel columns - vertical members of the spandrel bent which support 

the spandrel bent cap 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.7

3⁄4 Spandrel beams - fascia beams of the floor system 

3⁄4 Floor system - a slab or tee beam arrangement supported by the spandrel 

bent caps and the substructure elements 

The secondary members of an open spandrel arch bridge are the arch struts, which 

are transverse beam elements connecting the arch ribs. Arch struts provide 

stability against lateral forces and reduce the unsupported compression length 

between supports (see Figure 7.5.9). 

Arch Rib

Arch Strut

Spandrel

Bent

Floor System

Figure 7.5.9 Primary and Secondary Members of an Open Spandrel Arch

 Closed Spandrel Arch 

For a closed spandrel arch, the primary members are the arch rings and spandrel 

walls. The arch rings support fill material, roadway, and traffic, while the spandrel 

walls retain fill material and support the bridge parapets. 

The arch and members supported by the arch are superstructure elements. The 

arch itself is the primary load-carrying element of the superstructure (see Figure 

7.5.10). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.8

 

Spandrel Wall

(Primary)

Arch Rings

(Primary) Fill Material

Roadway Pavement

Figure 7.5.10 Primary Members of a Closed Spandrel Arch 

 Concrete Arch Culverts 

The primary member in a concrete arch culvert is the culvert barrel. The barrel 

supports fill material and any live loads crossing the structure. 

Steel Reinforcement For the proper inspection and evaluation of concrete arch bridges and culverts, the 

inspector must be familiar with the location and purpose of steel reinforcement. 

Open Spandrel Arch 

The primary reinforcing steel in an open spandrel arch follows the shape of the 

arch from support to support. Since the arch is a compression member, 

reinforcement is similar to column reinforcement. The surfaces of the arch rib are 

reinforced with equal amounts of longitudinal steel held in place with lateral ties. 

This longitudinal or column reinforcement can act as compression reinforcement 

when the arch must resist moment due to axial load eccentricity or lateral loads. 

Spandrel columns are also compression members and are reinforced similar to the 

arch rib (see Figure 7.5.11). 

In spandrel bent caps, the primary reinforcement is tension and shear steel. This is 

provided using "Z" shaped bars and stirrups since the cap behaves like a fixed end 

beam (see Figure 7.5.12). 

The floor system is designed and reinforced similar to other concrete beams (e.g. 

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

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.9

 

Arch Ring

Arch Rib

Spandrel

Column

Steel Reinforcement

Figure 7.5.11 Open Spandrel Arch Reinforcement 

Tension Reinforcement

Stirrups

Figure 7.5.12 Spandrel Bent Cap Reinforcement

 Closed Spandrel Arch 

The primary reinforcing steel in the arch ring follows the shape of the arch from 

support to support and consists of a mat of reinforcing steel on both the top and 

bottom surfaces of the arch. The inspector will be unable to inspect the top surface 

of the arch due to the backfill. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.10

The spandrel walls are designed to retain the backfill material. The primary 

tension steel for the wall is usually at the back, or unexposed, face of the wall, 

hidden from view. The front, or outside, face of the wall is reinforced in both 

directions with temperature and shrinkage steel (see Figure 7.5.13). 

Primary Reinforcement

Figure 7.5.13 Reinforcement in a Closed Spandrel Arch 

 Arch Culvert 

Reinforcement for arch culverts follows the shape of the arch from support to 

support. A mat of reinforcing steel is used on the top and bottom surfaces of the 

arch. 

 Other Reinforcement 

Temperature and shrinkage reinforcement is used in the floor system for open 

spandrel arches. 

A grid of temperature and shrinkage reinforcement is used in spandrel walls for 

closed spandrel arches. 

7.5.3 

Overview of 

Common Defects 

Common defects that occur on concrete arches and 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 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.11

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 

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. 

7.5.4 

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 concrete arches and culverts for cracks, spalls, and other defects 

is primarily a visual activity. 

Physical 

Sounding by hammer can be used to detect 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 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.12

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 

Open and Closed 

Spandrel Arches 

Bearing Areas 

The arch/skewback interface has the greatest bearing load magnitude. Inspect for 

loss of cross section of the reinforcement bars at the spalls. Examine the arch for 

longitudinal cracks. These indicate an overstress condition. 

The arch/spandrel column interface has the second greatest bearing load 

magnitude. Examine for reinforcement cross-section loss at the spalls. Check for 

horizontal cracks in the columns within several meters from the arch. These 

indicate excessive bending in the column, which is caused by overloads and 

differential arch rib deflection. 

The spandrel column/cap interface has the third greatest bearing load magnitude. 

Inspect for loss of section due to spalling. Examine the column for cracks which 

begin at the inside corner and propagate upward. These indicate differential arch 

rib deflections (see Figure 7.5.14). 

The floor system/bent cap interface has the smallest bearing load magnitude. 

Examine bearing areas as described in the deck, tee beam and girder sections. 

Examine the arch ring for unsound concrete. Look for rust stains, cracks, 

discoloration, crushing, and deterioration of the concrete. The interface between 

the spandrel wall and the arch should be carefully inspected for spalls that could 

reduce the bearing area. Investigate the arch for transverse cracks, which indicate 

an overstress condition. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.13

Figure 7.5.14 Spandrel Column Cap Interface

 Shear Zones 

Check for shear cracks at the ends of the spandrel bent caps. When arch ribs are 

connected with struts, examine the arches near the connection for diagonal cracks 

due to torsional shear. These cracks indicate excessive differential deflection in 

the arch ribs. Also investigate the floor system for shear cracks. 

 Tension Zones 

Inspect the tension areas of the spandrel bent caps and columns (i.e., mid-span at 

the bottom and ends at the top) (see Figure 7.5.15). Also check the tension areas 

in the floor system. 

Check for transverse cracks in the arch which indicate an overstress condition. 

Transverse cracks are oriented perpendicular to the arch member. 

Inspect the spandrel walls for sound concrete. Look for cracks, movement, and 

general deterioration of the concrete (see Figure 7.5.16). 

Spandrel Column 

Spandrel Cap 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.14

 

Arch Rib

Spandrel Bent

Column

Spandrel Bent Cap

Spandrel Bent

Tension Zones

Figure 7.5.15 Spandrel Bent Tension Zone

Figure 7.5.16 Deteriorated Arch/Spandrel Wall Interface 

 Compression Zones 

Investigate the compression areas throughout the arches and spandrel columns (not 

only at the bearing areas). Transverse or lateral cracks indicate excessive surface 

stresses caused by buckling forces and bending moment (see Figure 7.5.17). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.15

Figure 7.5.17 Severe Scaling and Spalling on a Spandrel Column

 Secondary Members 

The diaphragms and struts should be inspected for flexural and shear cracks, as 

well as for typical concrete defects. Defects in the secondary members may be an 

indication of differential settlement of the substructure or differential deflection of 

the concrete arches.

 Areas Exposed to Drainage 

For an open spandrel arch, check the areas exposed to drainage and roadway 

runoff. Elements beneath the floor system are prone to scaling, spalling, and 

chloride contamination (see Figure 7.5.18). 

For a closed spandrel arch, make sure that weep holes are working properly. Also, 

check that surface water drains properly and does not penetrate the fill material. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.16

Figure 7.5.18 Scaling and Contamination on an Arch Rib Due to a Failed 

Drainage System

 Areas Exposed to Traffic 

Check areas damaged by collision. Document the number of exposed and severed 

reinforcing bars with section loss as well as the spalled and delaminated concrete. 

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

between the concrete and steel reinforcement is affected. 

 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 reinforcement. 

Concrete Arch Culverts For a concrete arch culvert, the following locations should be inspected: 

Inspect the culvert barrel for rust stains, cracks, discoloration, crushing, and other 

deterioration of the concrete. Inspect the culvert barrel for spalls, delaminations, 

and rebar section loss. 

Check weep holes for partial or full blockage. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.17

Check approach conditions for dips, sags, cracks, pavement patches or other 

settlement indicators. 

Examine headwalls and wingwalls for scour, undermining and settlement. 

Cracking, tipping, or separations of the barrel from the headwall are indications of 

undermining and settlement. 

When dealing with precast concrete culverts, inspect for joint defects, leaking 

joints, cracked joints, and separated joints. 

Refer to Topics 11.1 through 11.3 for waterway inspection procedures and 

locations. 

7.5.5 

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

inspection of concrete bridges. 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 or culvert. 

Rating codes range from 9 to 0, where 9 is the best rating possible. The previous 

inspection data should be considered along with current inspection findings to 

determine the correct rating. See Topic 4.2 (Item 59 and Item 62) for additional 

details about NBI Rating Guidelines. 

For concrete arch 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. Like concrete arches, 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. 

Element Level Condition 

State Assessment 

In an element level condition state assessment of a concrete arch or arch culvert, 

the AASHTO CoRe element is one or more of the following: 

Element No. Description

 Open Spandrel Arch

109 Open Girder/Beam (P/S Concrete) 

110 Open Girder/Beam (Reinforced Concrete) 

154 Floorbeam (P/S Concrete) 

155 Floorbeam (Reinforced Concrete) 

115 Stringer (stringer floorbeam system) (P/S Concrete) 

116 Stringer (stringer floorbeam system) (Reinforced 

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

TOPIC 7.5: Concrete Arches and Arch Culverts 

7.5.18

143 Arch (P/S Concrete) 

144 Arch (Reinforced Concrete) 

204 Column or Pile Extension (P/S Concrete) 

205 Column or Pile Extension (Reinforced Concrete) 

233 Cap (P/S Concrete) 

234 Cap (Reinforced Concrete) 

 Closed Spandrel Arch

143 Arch (P/S Concrete) 

144 Arch (Reinforced Concrete) 

 Arch Culvert

241 Arch Culvert (Precast, Prestressed, or Reinforced 

Concrete) 

The quantities, when dealing with concrete arches or culverts, are all in meters or 

feet except for Elements 204 and 205, which are given in units of each. The above 

elements for concrete arches and culverts consist of three to five condition state 

descriptions to choose from for each element. The total length must be distributed 

among the three to five 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. 

Use Figure 7.5.19 to determine total quantities of concrete closed spandrel arches 

and arch culverts. 

Measurement

for Culvert

Measurement for

Closed Spandrel

Arch

Figure 7.5.19 Measurements for Closed Spandrel Arches and Arch Culverts 

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 the case of open and closed 

spandrel arches are Element 360 “Settlement”, and Element 362 “Traffic Impact”. 

In addition, concrete arch culverts can use Smart Flag Element 361 “Scour” or 

Element 362 “Traffic Impact” if needed. One of three condition state descriptions 

is chosen for each Smart Flag element that is used. 
7.6-i

Table of Contents

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

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.6 Concrete Rigid Frames........................................................................... 7.6.1 

 

 7.6.1 Introduction ................................................................................ 7.6.1 

 7.6.2 Design Characteristics ................................................................ 7.6.1 

 General................................................................................... 7.6.1 

 Primary and Secondary Members.......................................... 7.6.3 

 Steel Reinforcement............................................................... 7.6.4 

 Primary Reinforcement ................................................... 7.6.4 

 Secondary Reinforcement ............................................... 7.6.6 

 7.6.3 Overview of Common Defects................................................... 7.6.6 

 

7.6.4 Inspection Procedures and Locations ......................................... 7.6.7 

 Procedures.............................................................................. 7.6.7 

 Visual .............................................................................. 7.6.7 

 Physical ........................................................................... 7.6.7 

 Advanced Inspection Techniques.................................... 7.6.7 

 Locations ............................................................................... 7.6.8 

 Bearing Areas.................................................................. 7.6.8 

 Shear Zones..................................................................... 7.6.8 

 Tension Zones ................................................................. 7.6.9 

 Compression Zones....................................................... 7.6.10 

 Areas Exposed to Drainage........................................... 7.6.10 

 Areas Exposed to Traffic............................................... 7.6.11 

 Areas Previously Repaired............................................ 7.6.11 

 Concrete Box Culverts......................................................... 7.6.11 

 

 7.6.5 Evaluation ................................................................................ 7.6.11 

 NBI Rating Guidelines ........................................................ 7.6.11 

 Element Level Condition State Assessment ........................ 7.6.12 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6-ii

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7.6.1 

Topic 7.6 Concrete Rigid Frames 

7.6.1 

Introduction A concrete rigid frame structure is a bridge type in which the superstructure and 

substructure components are constructed as a single unit. Rigid frame action is 

characterized by the ability to transfer moments at the knee, the intersection 

between the frame legs and the frame beams or slab. Reinforced concrete rigid 

frame bridges and culverts are cast-in-place monolithic units. 

7.6.2 

Design 

Characteristics 

General The rigid frame bridge can either be single span or multi-span (see Figure 7.6.1). 

Single span frame bridges span up to 15 m (50 feet) and are generally a slab beam 

design. The basic single span frame shape is most easily described as an inverted 

“U” (see Figure 7.6.2). 

Figure 7.6.1 Three Span Concrete Rigid Frame Bridge 

Multi-span frame bridges are used for spans over 15 m (50 feet) with slab or 

rectangular beam designs (see Figure 7.6.3). Other common multi-span frame 

shapes include the basic rectangle, the slant leg or K-frame, and Delta frames (see 

Figure 7.6.4). Due to frame action between the horizontal members and the 

vertical or inclined members, multi-span frames are not considered continuous. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.2 

Figure 7.6.2 Typical Single-span Rectangular Concrete Rigid Frame Bridge 

Figure 7.6.3 Typical Concrete Frame Culvert

Rigid frame structures are utilized both at grade and under fill, such as in concrete 

frame culverts (see Figure 7.6.3). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.3 

Figure 7.6.4 Typical Concrete K-frame Bridge

Primary and Secondary 

Members 

For single span frames, the primary member is considered to be the slab portion 

and the legs of the frame (see Figure 7.6.5). For state and federal rating 

evaluation, the slab portion is considered the superstructure while the legs are 

considered the substructure. 

SUPERSTRUCTURE

RIGID FRAME

SUBSTRUCTURE

Slab - Primary

Legs - Primary

Figure 7.6.5 Elevation of a Single Span Frame 

For multi-span frames, the primary members include the frame legs (the slanted 

beam portions which replace the piers) and the frame beams or slab (the horizontal 

portion which is supported by the frame legs and abutments) (see Figure 7.6.6).

For state and federal rating evaluation, the frame beams or slabs and frame legs are 

considered the superstructure while the abutments are considered the substructure. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.4 

Figure 7.6.6 Elevation of a K-frame 

There are no secondary members for concrete rigid frames. 

Steel Reinforcement Rigid frame structures develop positive and negative moment throughout due to 

the interaction of the frame legs and frame beams (see Figure 7.6.7). In slab beam 

frames, the primary reinforcement is used to resist tension and possibly shear. 

ΔA

Load P

Simply Supported

ΔB

Load P

Frame

Inflection 

Points

Figure 7.6.7 Deflected Simply Supported Slab versus Deflected Frame Shape 

 Primary Reinforcement 

For gravity and traffic loads on single span slab frames, the tension steel is placed 

longitudinally in the bottom of the frame slab, vertically in the front face of the 

frame legs, and longitudinally and vertically in the outside corners of the frame 

(see Figure 7.6.8). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.5 

PRIMARY REINFORCEMENT

Figure 7.6.8 Tension Reinforcement in a Single Span Slab or Beam Frame 

For multi-span slab frames, the tension steel is placed longitudinally in the top and 

bottom of the frame slab and vertically in both faces of the frame legs (see Figure 

7.6.9). 

PRIMARY REINFORCEMENT

Tension Steel

Tension Steel Tension Steel

Figure 7.6.9 Tension Reinforcement in a Multi-span Slab or Beam Frame

The primary reinforcement in the frame beam portion is longitudinal tension and 

shear stirrup steel, similar to continuous beam reinforcement (see Topic 7.2.2). 

In the frame legs, the primary reinforcement is tension and shear steel near the top 

and compression steel with ties for the remaining length (see Figure 7.6.10). See 

Topic 10.2 for a discussion of compression steel and column ties. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.6 

Tension Steel

Stirrups

Frame Leg

Steel

Ties

Figure 7.6.10 Tension, Shear, and Column Reinforcement in a Typical K-frame 

 Secondary Reinforcement 

Temperature and shrinkage reinforcement is distributed similar to that of a slab 

(see Topic 7.1) or tee-beam (see Topic 7.2) or box beams (see Topic 7.10). 

7.6.3 

Overview of 

Common Defects 

Common defects that occur on concrete rigid frame 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 

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. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.7 

7.6.4 

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 concrete rigid frames for cracks, spalls, and other defects is 

primarily a visual activity. 

Physical 

Sounding by hammer or chain drag 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. 

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 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.8 

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 the 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 slab or frame beams over the frame legs. Check the 

condition of the bearings, if present. 

 Shear Zones 

Inspect the area near the supports where the frame beams or slab meet the frame 

legs or abutments. Look for shear cracks in the frame beams or slab (beginning at 

the frame legs and propagating upward toward mid-span). 

Inspect the frame legs for diagonal cracks that initiated at the frame beam/slab or 

footing (see Figure 7.6.11). 

Figure 7.6.11 Shear Zones in Single Span and Multi-span Frames 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.9 

 Tension Zones 

Inspect the tension areas for flexure cracks, rust stains, efflorescence, exposed and 

corroded reinforcement, and deteriorated concrete which would cause debonding 

of the tension reinforcement. The tension areas are located at the bottom of the 

frame beam at mid-span, the base of each frame leg (usually buried), and the 

inside faces of the frame legs at mid-height of single span slab frames (see 

Figures7.6.12 and 7.6.13). 

Tension Zones

Compression Zones

Figure 7.6.12 Tension Zones in a Single Span Beam Frame 

Tension Zones

Compression Zones

Figure 7.6.13 Tension Zones in a Multi-span Frame
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.10

 Compression Zones 

Investigate the compression areas for delamination, spalling, scaling, crushing, and 

exposed reinforcement. The legs of a frame act primarily as columns with a 

moment applied at the top (see Figures 7.6.12 and 7.6.13). Check the entire length 

of the frame legs for horizontal cracks, which indicate crushing. 

 Areas Exposed to Drainage 

Examine the areas exposed to drainage for deteriorated and contaminated concrete. 

Check the roadway surface of the slab or frame beams for delamination and spalls 

(see Figure 7.6.14). Special attention should be given to the tension zones and 

water tables. 

Figure 7.6.14 Roadway of a Rigid Frame Bridge with Asphalt Wearing Surface 

Check longitudinal joint areas of adjacent slab or frame beams for leakage and 

concrete deterioration (see Figure 7.6.15). Check around scuppers and drain holes 

for deteriorated concrete. Check slab or frame beam ends for deterioration due to 

leaking deck joints at the abutments. Check to see if weep holes are functioning 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.11

Figure 7.6.15 Longitudinal Joint Between Slab Beam Frames 

 Areas Exposed to Traffic 

Check areas damaged by collision. Document the number of exposed and severed 

reinforcing bars with section loss as well as the spalled and delaminated concrete. 

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

between the concrete and steel reinforcement is affected. 

 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 reinforcement. 

Concrete Box Culverts For additional inspection procedures and locations unique to concrete box culverts 

and waterways, see Topic 7.12 and Topic 11.2. 

7.6.5 

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

inspection of concrete bridges. 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 or 

62) for additional details about NBI Rating Guidelines. 

The previous inspection data should be considered along with current inspection 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.6: Concrete Rigid Frames 

7.6.12

findings to determine the correct rating. 

Element Level Condition 

State Assessment 

There is no specific element level condition state assessment of a concrete rigid 

frame bridges. The following AASHTO CoRe elements may be used to best 

describe a concrete rigid frame: 

Element No. Description

038 Concrete Slab - Bare 

052 Concrete Slab – Protected with Coated Bars 

053 Concrete Slab – Protected with Cathodic System 

105 Concrete Closed Web/Box Girder 

110 Concrete Open Girder/beam 

205 Column or Pile Extension – Reinforced Concrete 

210 Pier Wall – Reinforced Concrete 

215 Abutment – Reinforced Concrete 

241 Reinforced Concrete Culvert (see Topic 7.12) 

The unit quantity for slab and columns is each, and the entire element must be 

placed in one of the five available condition states. Some states have elected to 

use the total area for the slab top surface (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 

slab surface area in order to calculate a percent deterioration and fit into a given 

condition state description. The unit quantity for the girder/beam and pier wall is 

meters or feet, and the total length must be distributed among the 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 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. This Smart Flag is particularly 

useful if the wearing surface inhibits inspection of the top surface of the deck. For 

damage to traffic impact, the “Traffic Impact” Smart Flag, Element No. 362, can 

be used and one of the three condition states assigned. 
7.7-i

Table of Contents

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

Inspection and 

Evaluation of 

Common Concrete 

Superstructures 

 7.7 Precast and Prestressed Slabs................................................................. 7.7.1 

 7.7.1 Introduction............................................................................... 7.7.1 

 

 7.7.2 Design Characteristics............................................................... 7.7.1 

 General.............................................................................. 7.7.1 

 Monolithic Behavior......................................................... 7.7.2 

 Identifying Voided Slabs .................................................. 7.7.2 

 Primary and Secondary Members..................................... 7.7.2 

 Steel Reinforcement.......................................................... 7.7.2 

 Primary Reinforcement .............................................. 7.7.2 

 Secondary Reinforcement .......................................... 7.7.3 

 

 7.7.3 Overview of Common Defects ................................................. 7.7.3 

 

 7.7.4 Inspection Procedures and Locations........................................ 7.7.4 

 Procedures......................................................................... 7.7.4 

 Visual ......................................................................... 7.7.4 

 Physical ...................................................................... 7.7.4 

 Advanced Inspection Techniques............................... 7.7.4 

 Locations........................................................................... 7.7.5 

 Bearing Areas............................................................. 7.7.5 

 Shear Zones................................................................ 7.7.5 

 Tension Zones ............................................................ 7.7.6 

 Areas Exposed to Drainage ........................................ 7.7.7 

 Areas Exposed to Traffic............................................ 7.7.7 

 Areas Previously Repaired......................................... 7.7.7 

 General ....................................................................... 7.7.8 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7-ii

 7.7.5 Evaluation ................................................................................. 7.7.8 

 NBI Rating Guidelines...................................................... 7.7.8 

 Element Level Condition State Assessment ..................... 7.7.8
7.7.1 

Topic 7.7 Precast and Prestressed Slabs 

7.7.1 

Introduction Precast and prestressed slabs have gained popularity since the 1950’s. This type of 

design acts as a deck and superstructure combined (see Figure 7.7.1). Individual 

members are placed side by side and connected together so they act as one slab. 

When vertical clearances are lacking, this type of design is effective, due to the 

slab’s shallow depth. Wearing surfaces are generally applied to the top of precast 

and prestressed slabs and are either concrete or bituminous. 

Figure 7.7.1 Typical Prestressed Slab Beam Bridge 

Although precast and prestressed slabs are different from concrete decks, the 

design characteristics, wearing surfaces, protection systems, common defects, 

inspection procedures and locations, evaluation, and motorist safety concerns are 

similar to concrete decks. Refer to Topic 5.2 for additional information about 

concrete decks. For the purpose of this manual, decks are supported by 

superstructure members while slabs are supported by substructure units. 

7.7.2 

Design 

Characteristics 

General The precast voided slab bridge is the modern replacement of the cast-in-place slab. 

This type of bridge superstructure is similar to the cast-in-place slab in appearance 

only. It is comprised of individual precast slab beams fabricated with circular 

voids. The voids afford economy of material and reduce dead load (see Figure 

7.7.2). Precast slab bridges with very short spans may not contain voids. 

Precast slab units are practical for spans of 6 to 15 m (20 to 50 feet). The slabs can 

be single or multiple simple spans. The units are typically 915 to 1220 mm (36 or 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.2 

48 inches) wide and have a depth of up to 530 mm (21 inches). These special 

precast units are generally comprised of 28 to 56 MPa (4,000 to 8,000 psi) 

prestressed concrete, and reinforced with 1860 MPa (270 ksi) pre- or posttensioned steel tendons. 

900 mm to 1200 mm

(3' - 4')

Shear

Key

530 mm

(21" max.)

Typical Voided Slab

Post-tensioning tie rod

Figure 7.7.2 Cross Section of a Typical Voided Slab 

Monolithic Behavior Adjacent slab units may be post-tensioned together with tie rods having a tensile 

capacity of 1000 MPa (145 ksi) and grouted at the shear keys. Together these 

enable the slab units to act monolithically. Drain holes are placed strategically in 

the bottom of the slab to allow accumulated moisture to escape. 

Identifying Voided Slabs Physical dimensions alone are not enough to distinguish a slab unit from a box 

beam. Design or construction plans need to be reviewed. A box beam has one 

rectangular void, bounded by a top slab, bottom slab, and two webs. A typical box 

beam has a minimum depth of 305 mm (12"). A typical voided slab section has 

two or three circular voids through it. It is also possible to find precast solid slab 

units. 

Primary and Secondary 

Members 

The primary members of a precast voided slab bridge are the individual slab units. 

The slab units make up the superstructure and the deck and are commonly 

protected by an asphalt or concrete overlay. There are no secondary members. 

Steel Reinforcement Primary Reinforcement

The primary reinforcement consists of longitudinal tension steel and shear 

reinforcement or stirrups. 

Prestressing strands placed near the bottom of the slab make up the main tension 

steel. 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) diameter. Strands are normally spaced 50 mm (2 

inches) on center (see Figure 7.7.3). 

Shear reinforcement consists of U-shaped or closed loop stirrups located 

throughout the slab at various spacings required by design. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.3 

Secondary Reinforcement 

Secondary reinforcement is provided to control temperature and shrinkage 

cracking. This reinforcement is placed longitudinal in the beam. 

Temperature and

shrinkage steel

Stirrups

High strength

steel strands or 

reinforcement bars

Figure 7.7.3 Prestressed Slab Beam Bridge Reinforcement 

7.7.3 

Overview of 

Common Defects 

Common defects that occur on precast and prestressed slab 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 

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. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.4 

7.7.4 

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 concrete slabs for cracks, spalls, wear, and other defects is 

primarily a visual activity. 

Physical 

The physical examination of the top surface of the slab with a hammer can be a 

tedious operation. In most cases, a chain drag is used to determine delaminated 

areas. A chain drag is made of several sections of chain attached to a pipe that has 

a handle attached to it. The inspector drags this across a slab and makes note of 

the resonating sounds. 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 

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: 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.5 

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 the bearing areas for cracking, delamination or spalling where thermal 

movement and high bearing pressure could overstress the concrete. End spalling 

can eventually lead to the loss of bond in the prestressing tendons. Bearing areas 

should also be checked for defects or deterioration due to leaking joints. 

Check bearing areas for spalls or vertical cracks. Spalls and cracks may be caused 

by corrosion of steel due to water leakage or restriction of thermal movement due 

to a faulty bearing mechanism. 

 Shear Zones 

Inspect near the supports for diagonal or shear cracks.

Inspect the top surface for longitudinal reflective cracking and between the slab 

sections for leakage (see Figure 7.7.4). These problems indicate failed shear keys 

and that the slab units are no longer tied together or acting monolithically. 

Observe if there is differential slab deflection under live load. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.6 

Figure 7.7.4 Leaking Joint between Adjacent Slab Units 

 Tension Zones 

Check the bottom of the slab sections for flexure cracks due to positive moments. 

Since prestressed concrete is under high compressive forces, no cracks should be 

present. Cracks can be a serious problem since they indicate overloading or loss of 

prestress. Cracks that may be present will be difficult to detect with the naked eye. 

To improve detection, a common practice is to wet the slab surface with water 

using a spray bottle. Capillary action will draw water into a crack, thus producing 

a visible line when the surrounding surface water evaporates. All cracks should be 

measured with an optical crack gauge or crack comparator card. 

Examine the top of the slab sections (if exposed) near the ends for tensile cracks 

due to prestress eccentricity. This indicates excessive prestress force. If the top of 

the slab has a wearing surface applied, check for cracks in the wearing surface. 

Cracks in the wearing surface may be an indication that the slab is overstressed or 

that water is getting to the slab. 

Investigate for evidence of sagging, which indicates a loss of prestress. Use a 

string line or site down the bottom edge of the fascia slab. 

Inspect the slabs for exposed strands. Prestressed strands will corrode rapidly and 

fail abruptly. Therefore, any exposure is significant (see Figure 7.7.5). 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.7 

Check for longitudinal cracking in slab members. Water freezing in the voids can 

cause longitudinal cracks. Skewed slab units may exhibit longitudinal cracks due 

to uneven prestressing force in the strands. 

Figure 7.7.5 Exposed Strands in a Precast Slab Beam

 Areas Exposed to Drainage 

Inspect areas exposed to drainage for deteriorated and contaminated concrete. This 

includes the entire riding surface of the slab, particularly around scuppers or 

drains. Spalling or scaling may also be found along the curbline and fascias. 

Inspect longitudinal joints between the precast slabs. Drainage through the joints 

indicates a broken shear key and loss of monolithic action. 

 Areas Exposed to Traffic 

When precast voided slab superstructures are used for a grade crossing, check the 

areas over the traveling lanes for collision damage. This is generally not a 

problem due to the good vertical clearance afforded by the relatively shallow slab 

units. 

Check areas exposed to wear on the top 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. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.8 

 General 

Check the camber of the slab units. Loss of positive camber indicates loss of 

prestress in the tendons. 

Check the condition of the lateral post-tensioning grout pockets. Cracked grout or 

rust stains may indicate a failure of the post-tensioning tendon or loss of 

monolithic action. 

7.7.5 

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. For a 

precast or prestressed slab bridge, these guidelines must be applied for both the 

deck component and the superstructure component. 

The previous inspection data should be considered along with current inspection 

findings to determine the correct rating. 

Typically, for this type of structure, the deck and superstructure components will 

have the same rating. 

Element Level Condition 

State Assessment 

In an element level condition state assessment of a precast or prestressed slab 

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

riding surface: 

Element No. Description

Concrete Slab 

38 Concrete Slab – Bare 

39 Concrete Slab – Unprotected with AC Overlay 

40 Concrete Slab – Protected with AC Overlay 

44 Concrete Slab – Protected with Thin Overlay 

48 Concrete Slab – Protected with Rigid Overlay 

52 Concrete Slab – Protected with Coated Bars 

53 Concrete Slab – Protected with Cathodic System 

P/S Box Girder 

104 P/S Closed Web/Box Girder 

The unit quantity for the slab 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 slab 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 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.9 

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

inspector must know the total slab 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 

available condition states depending on the extent and severity of deterioration. 

Element 104 is the closest choice in the AASHTO element list for 

precast/prestressed slabs. Condition state 1 is the best possible rating. See the 

AASHTO Guide for Commonly Recognized (CoRe) Structural Elements for 

condition state descriptions. States may decide to choose their own element 

number for precast/prestressed slabs because AASHTO does not have a specific 

element number for prestressed slabs. 

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 slabs, 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 slab element, the “Soffit” Smart Flag, Element No. 359, can 

be used and one of five condition states assigned. 
SECTION 7: Inspection and Evaluation of Common Concrete Superstructures 

TOPIC 7.7: Precast and Prestressed Slabs 

7.7.10

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