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53239723 Box Culvert Design Manual
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CHAPTER 19: REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES (Limited Revisions)
Section 19.4.4 19.4.4
Changes Changed reference from Chapter 20 of the HDM to Chapter 9 of the HDM. Changed reference from Section 11.4 of the Bridge Manual to Section 11.5.3 of the Bridge Manual.
CHAPTER 19 REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES
Contents 19.1 19.2 19.3
INTRODUCTION .................................................................................................. 19-1 SELECTION CRITERIA ....................................................................................... 19-3 PROJECT DEVELOPMENT PROCEDURES FOR BRIDGE SIZE CULVERTS . 19-4 19.3.1 19.3.2 19.3.3 19.3.4 19.3.5 Structure Type Selection .......................................................................... 19-4 Precast Arch and Arch-Topped Unit Guidelines ....................................... 19-4 Precast Frame Unit (Three-Sided Structure) Guidelines .......................... 19-5 Details/Contract Plans .............................................................................. 19-6 Quality Assurance Reviews ...................................................................... 19-6
FOUNDATIONS ................................................................................................... 19-7 19.4.1 19.4.2 19.4.3 19.4.4 Rock ......................................................................................................... 19-7 Earth or Granular Soil ............................................................................... 19-7 Precast Frames, Arch-Topped Units and Arches ..................................... 19-8 Wingwalls ................................................................................................. 19-8
DESIGN GUIDELINES FOR BOX CULVERTS ................................................... 19-9 19.5.1 Design Method ......................................................................................... 19-9 19.5.2 Analysis Method ..................................................................................... 19-10 19.5.3 Load Factors........................................................................................... 19-10 19.5.4 Dead Load and Earth Pressure .............................................................. 19-10 19.5.5 Live Load ................................................................................................ 19-10 19.5.6 Live Load Impact Factor ......................................................................... 19-11 19.5.7 Wall Thickness Requirements ................................................................ 19-11 19.5.8 Concrete Strength .................................................................................. 19-11 19.5.9 Reinforcement Requirements ................................................................. 19-12 19.5.10 Skewed Precast Units ........................................................................... 19-12 19.5.11 Detailing Requirements ......................................................................... 19-13 19.5.12 Load Rating Requirements.................................................................... 19-13 19.5.13 Deflection Limitations ........................................................................... 19-13 19.5.14 Span-to-Rise Ratios .............................................................................. 19-13
COMPUTER DESIGN AND ANALYSIS PROGRAM ........................................ 19-14
DESIGN AND DETAILS OF CONCRETE CULVERTS ............................................. 19-14 19.7.1 19.7.2 19.7.3 19.7.4 Contract Plans ................................................................................................ 19-15 Design Procedure ........................................................................................... 19-17 Reinforcement ................................................................................................ 19-23 Headwalls/Edge Beams ................................................................................. 19-25
PRECAST CONCRETE CULVERTS......................................................................... 19-25 19.8.1 19.8.2 19.8.3 19.8.4 19.8.5 19.8.6 Contract Plans ................................................................................................ 19-26 Reinforcement ................................................................................................ 19-27 Design and Fabrication .................................................................................. 19-27 Precast Frames, Arch-Topped Units and Arches ........................................... 19-27 Designer Notes for Precast Culverts .............................................................. 19-28 Shop Drawing Approvals ................................................................................ 19-28
GUIDE RAILING ........................................................................................................ 19-28
19.10 CUT-OFF WALL ........................................................................................................ 19-30 19.11 LOW-FLOW DISH...................................................................................................... 19-30 19.12 APRONS .................................................................................................................... 19-31 19.13 SUBBASE DRAINAGE.............................................................................................. 19-32 19.14 REFERENCES ........................................................................................................... 19-34
LIST OF FIGURES 19-1 19-2 19-3 19-4 19-5 19-6 Typical Cross Sections, Cast-In-Place ....................................................................... 19-18 Wing Walls Plan and Elevation, Cast-In-Place .......................................................... 19-19 Contraction & Construction Joint, Cast-In-Place ....................................................... 19-20 Wing Wall Plan, Culvert on Skew, Cast-In-Place ....................................................... 19-21 Wing Wall Aprons, Cast-In-Place .............................................................................. 19-22 Reinforcement Diagram, Cast-in-Place ...................................................................... 19-24
Any questions on whom should design a specific-size structure should be discussed with the Regional Structures Engineer. scour. and details for cast-in-place culverts. all structures in this chapter will be referred to as culverts.1 INTRODUCTION
This chapter presents the requirements for designing reinforced concrete culverts.
§19.096 m) may be designed by highway engineers with minimal oversight of a bridge engineer. culvert-size structures (<6. The information in this chapter is intended to be used as guidelines and minimum recommendations. Each location will usually have some unique character (floods.) along the center line of the roadway are considered bridges. Engineering judgment will need to be used for most projects. The history of the project site must always be evaluated and must be factored into each design. Unique environments need to be thoroughly evaluated and all environmental requirements satisfied. etc. Structures spanning more than 6. The information in this chapter applies to both culvert and bridge size culverts. Bridge-size culverts (>6. It also provides guidance about the information to include in the contract documents. with an interior width of 6.096 m is technically not a culvert.1
. the procedures for designing culverts and bridges are significantly different due to the differing risks associated with the size of the structure.096 m) warrant more complex hydraulic and foundation treatments which require the expertise of a bridge engineer. Simpler. surroundings.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19. where to present the information.096 m (20 ft. salt water. A list of available references needed to complete a culvert design is also provided. While it is recognized that any structure with a span over 6. whether of single.or multiple-span construction. As with any structural engineering design.096 m (20 ft. for simplicity. However. alternate design methods are available. Safety and economic issues and technical complexity can vary significantly with differing site conditions which will dictate the size and type of the most appropriate structural solution. historic character.) or less when the measurement is made horizontally along the center line of the roadway from face-to-face of abutments or sidewalls. It is not possible to provide guidance for all conditions so guidance is provided for the typical design. safe design.). less complex. Definitions (explanations of the terminology used in this chapter) follow: A culvert is defined in the Standard Specifications as any structure. The designer has the ultimate responsibility to provide an efficient.
Any structure with a span greater than 6. The procedures for structures with a span greater than 6. equestrian/bicycle/pedestrian/golf cart paths. The maximum clear span recommended for a concrete box culvert is 7. Use of three-sided concrete culverts where rock is not at or near the streambed require pile support for the footings or some other form of positive scour protection.19-2
REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES
The procedure for the hydraulic analysis of culverts differs based on the span length. For smaller culverts.e. Three-sided concrete culverts on spread footings may be used for railroads.096 m may be obtained from the Structures Design and Construction Division or the Regional Hydraulics Engineer. cattle passes. The NYSDOT modifications for the AASHTO Model Drainage Manual and assistance in hydraulic design procedures for structures greater than 6. An arch or arch-topped culvert is considered a box culvert if the “sidewalls” are built monolithic with a bottom (invert) slab. It is recommended that for culverts with spans over 3. They have separate foundations with footings supported by rock or piles or an invert slab. i.5 m may prove to be uneconomical.65 m (12 ft. and other uses that do not convey water.) a HEC-RAS analysis or an equally sophisticated backwater analysis be used to determine the size and shape of the culvert. they do not have scour vulnerability. Concrete box culverts (four-sided) typically have rectangular cross sections. The clear span is the perpendicular distance between the inside face of the sidewalls. Three-sided concrete culverts may be rectangular in nature or a frame with varying wall and/or slab thicknesses or an arch or arch-topped structure.
§19.096 m will also require a more detailed analysis. There are two types of concrete culverts: four-sided (box) and three-sided. The largest culverts are typically not boxes.8.3 m.1
. an approximate analysis such as HY8 may be used with the criteria outlined in Chapter 8 of this manual..096 m is outlined in the AASHTO Model Drainage Manual with NYSDOT modifications.4. The design span for nonskewed culverts is the perpendicular distance between the centerlines of the sidewalls. A design span for a concrete box culvert in excess of 7. For culvert units with skewed ends. Concrete box culverts are typically used where the streambed is earth or granular soil and rock is not close enough to the streambed to directly support the structure. the design span is the distance between the centerlines of the sidewalls parallel to the skewed end. rather they are frames or arches and are discussed in Section 19.
concrete box culvert. an engineering and cost analysis should be done. The advantages of concrete culverts are superior durability for most environmental conditions. greater hydraulic efficiency. concrete culverts may be the least expensive option. and site constraints can be minimized when this option is chosen. and a short-span bridge.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19. Corrugated metal structures will also typically require taller structures to provide adequate waterway area below design high water than concrete culverts. For procedural steps on planning short-span bridges.e. and arches can have the least amount of cover by placing a minimum of 100 mm of asphalt pavement directly on the top slab. Acceptable crossing features are railroad tracks or bicycle and equestrian paths. and easier stage construction. Possible advantages of a bridge may be minimized work in the stream. Smaller corrugated metal structures typically require a minimum height of soil cover of 600 mm and for some structures the soil cover increases to 1. However. excessive water velocity. The basic choices are a corrugated metal structure. Corrugated metal structures may not fit the site conditions without appreciable changes to the roadway profile due to minimum height of soil cover requirements. While the site conditions are the primary deciding factor for structure selection.. concrete culverts should not be rejected as an alternative without making an engineering analysis that includes suitability to the site and life-cycle cost estimates. a precast option should be the first choice. Speed of erection. Concrete culverts.2 SELECTION CRITERIA
The most appropriate type of short-span structure must be determined by the designer. At sites with limited headroom. concrete frame or arch. Corrugated metal structures may be more cost efficient and should be considered when there will be no major risk of corrosion such as an arch on pedestal walls where there is infrequent water contact with the metal portion of the structure. frames. stream diversion problems. Information on corrugated metal structures (steel and aluminum) is available in Chapter 8 of this manual. Before a final determination is made to use a large concrete culvert. minimized interference with the existing structure foundation. potentially lower life-cycle costs). and typically longer service life (i.2
§19. aesthetics and economics are also very important. speed of erection. maintenance of traffic. see Section 3 of the NYSDOT Bridge Manual. When a concrete culvert is selected as the appropriate structure for the site. Hydraulics may dictate the need for a concrete culvert because of excessive back water. the use of a short-span bridge with laid-back slopes and integral abutments should be investigated. greater resistance to corrosion and damage due to debris. Precast and cast-in-place concrete culverts are usually more expensive in initial cost than corrugated metal structures. or ice and debris. If a corrugated metal structure is a viable option.2 m or more depending on size and shape.
• If site constraints do not eliminate the squaring of the ends.g. ONLY SKEWED-END UNITS ARE ACCEPTABLE. • When railing or barrier is attached to the skewed headwall and site constraints do not eliminate the squaring of the ends.. utilities.g.2
Sizes that are common to more than one manufacturer should be selected. Foundation requirements. Environmental concerns (e. Construction constraints (e. R. natural streambed).g.3. it must be clearly indicated on the contract plans as follows: DUE TO SITE RESTRICTIONS.1 Structure Type Selection Section 3 and Appendix 3D of the NYSDOT Bridge Manual identify the planning procedures to follow in determining appropriate structure type for short-span structures.g. 19. In cases where squaring of the unit ends would create a geometric conflict (proposed R. The amount of skew that can be fabricated varies.. stage construction).19-4
19.W. restrictions. Geometric limitations (e. skew angle.).3
PROJECT DEVELOPMENT PROCEDURES FOR BRIDGE-SIZE CULVERTS
19. utilities..O. include the following note on the contract plans:
§19.g. stage construction. Maintenance and protection of traffic requirements (e. Proper selection of the feasible structure alternatives is based on site. etc. including but not limited to: • • • • • • • • Vertical and horizontal clearance requirements. in an effort to obtain competitive bidding. The use of arch-shaped facade panels is not recommended.W. water diversion requirements).and project-specific parameters.3. it must be clearly indicated on the contract plans as follows: SQUARED-END UNITS MAY BE SUBSTITUTED FOR THE SKEWED-END UNITS SHOWN WITH NO CHANGE IN THE PAYMENT LIMITS SHOWN AND AT NO ADDITIONAL COST TO THE STATE.2 Precast Arch and Arch-Topped Unit Guidelines • Aesthetics concerns may make the use of arch-shaped units desirable. problems. Desired aesthetic treatments (e. whenever possible. arch appearance). Available “beam” (top slab) depth.. Some fabricators prefer to produce only 0° skew units. or site geometry)..3. especially for hydraulic openings due to ice and debris problems.O.
).3 Precast Frame Units (Three-Sided Structures) Guidelines • Many of the precast. no temporary spandrel walls are needed at the staging line to support the fill or pavement. This characteristic is useful when stage construction is proposed. The arch shape addresses any possible ponding problem of surface drainage that a flat unit cannot address without special fabrication or field adjustment needs.3.2 m. the unit can be slid into place. Arched units have been used as liners for old masonry or concrete arches.) or more.6 m (48 ft.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES
IF THE CONTRACTOR PROPOSES TO SUBSTITUTE SQUARE ENDS. If a larger rise is necessary.3.
19. Frame units provide a simpler bridge rail/headwall connection detail. Frame units provide a hydraulic opening greater than arches of equivalent clear span when flowing full. Large arch units may be shipped in 2 or 3 pieces and assembled on site. although typical span length increments are 600 mm. • An arch unit is preferable whenever units are to be placed on a pedestal-type wall to create a grade separation for motor vehicles or trains. Precast frame units can be fabricated by some manufacturers with any increment of span length up to 12.
§19. Arch units are preferred in cases where fills above the precast units are 3 m (10 ft. Maximum rise of the units is normally limited to 3. When used for staged construction with shallow highway pavements.1 m due to shipping and handling considerations.3
. After the construction of a pedestal wall at the base. the designer should investigate the need for a pedestal wall. and a dry environment is mandatory. The void between the existing arch and the liner is filled with grout installed through fittings cast into the liner units. DETAILS OF HOW THE RAILING/BARRIER ATTACHMENT IS TO BE ADDRESSED MUST BE PROVIDED BY THE CONTRACTOR AND APPROVED BY THE ENGINEER. frame-type units can be fabricated with skew angles up to 45°. Precast arch-topped units are currently available in spans up to 14.
5 12/16/05
. whether it is in a fill section or at grade.3. No fabricator shall be eliminated from consideration by NYSDOT for a given project. and other site limitations. the location within the R. specific project requirements that may exclude some fabricators must be identified (such as fabrication on a skew or a desired arched appearance). When a clear span-to-rise ratio greater than 4:1 is required at a specific site. The applicable details in Section 19. (Since some manufacturers only fabricate units at fixed increments of span length.
19. a multicell structure or a conventional bridge should be considered. Three-sided frames that have a clear span-to-rise ratio greater than 4:1 should have the structure modeled with a pin and roller support if any displacement at the support is anticipated. arch or arched-topped structure is determined to be the most appropriate solution. The policies and procedures for assuring quality in Section 20 of the Bridge Manual shall be followed.19-6
19. Any limitations on using a larger span must be shown..g. For four-sided culverts. stage construction details.1 shall be placed on the plans. The end treatment depends upon the skew.3. Limiting spans and heights must be shown for all alternatives. Skewed ends may require additional reinforcement and can lead to constructibility issues.O. the payment limits shall be identified as the area of the structure in plan view. the alignment of the feature crossed.4 Details/Contract Plans If a precast.3. Include a full elevation view in the contract plans showing the configuration of the most appropriate type unit (e. frame or arch). The two most typical options for culverts on a skew are ends parallel to the centerline of the roadway (skewed ends) or ends perpendicular to the centerline of the structural units (square ends). Show some of the other acceptable structure types in separate partial elevation views.5 Quality Assurance Reviews
The office of the design engineer responsible for the contract plans is also responsible for
the review of the design calculations for the units as well as any revisions to the foundation design. showing the limitations would allow the manufacturers to bid using special units or the next larger span length of their standard units). For three-sided structures.W. The maximum skew at which a precast unit should be fabricated is 45°. the payment limits shall be identified as the length of the total structure along a longitudinal centerline of the structural units. three-sided frame.. conflicts with utilities. the following procedures should be followed: • The plan view in the contract plans shall clearly show the orientation of the ends of the structure.7. However. The culvert orientation to the 6 of the highway may be at a skew greater than 45°. §19.
19. In some cases. Thus. The movement of cobbles and boulders will damage a concrete invert and reduce its life span. the wall height should be constant and the footing height varied.2
. 19.6 for information on design and shop drawing approvals.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES See Section 19.4. rip-rap lined invert. If rock is encountered in a limited area. The FDR is prepared by the Geotechnical Engineering Bureau in conjunction with Structures Design and Construction Division.4. In areas with a significant potential for cobbles and boulders to move with the bed load. in areas of compact soil and low stream velocities. a three-sided culvert with a strip footing on piles should be investigated. Concrete footings are either keyed or doweled into rock based on a consultation with an Engineering Geologist from the Geotechnical Engineering Bureau. For culverts with spans greater than 6. concrete box culverts should never be founded partially on rock and partially on earth.096 m.4
All structures discussed in this chapter.1 Rock When sound rock is at or near the surface of a streambed. Typical foundation treatment types can be found in the current Bridge Detail sheets (BDCBx). Foundation design questions should be directed to the Structures Design and Construction Division. foundation recommendations are provided to the designer in the Foundation Design Report (FDR). However. but this should be avoided. an invert slab is not required. If the elevation of the rock surface varies by 600 mm or less. an invert slab should be the first choice for the foundation treatment. If the variation in rock surface elevation exceeds 600 mm.096 m are provided by the Geotechnical Engineering Bureau. are considered buried structures in regard to foundation design.4. The Regional Geotechnical Engineer or the Geotechnical Engineering Bureau should be consulted to determine the proper foundation treatment. there is no requirement for seismic analysis. it should be removed to a minimum depth of 300 mm below the bottom of the bottom slab and backfilled with either 12/16/05 §19. Foundation design parameters for culverts with spans less than 6. This may change in the future as more research is completed.8. the height of the culvert wall may be varied at a construction joint or at a precast segment joint. articulated concrete mats. sheeting. regardless of span and height of cover.2 Earth or Granular Soil When a concrete culvert cannot be founded on rock. three-sided concrete culverts may be used if they have positive scour protection such as piles.
19. it may be required to use walls of unequal heights in the same segment. or spread footings founded below the calculated scour depth. To avoid differential settlement.
All precast concrete box culverts should have a designed undercut and backfill.19-8
select granular material or crushed stone. three-sided structure is selected for a site. The designer may contact known fabricators for design reactions. Wingwall design is not included in this Chapter. contact the Regional Structures Engineer or the Structures Design §19. Wingwalls may be cast-in-place or precast. If design assistance is required. and Arches When a bridge-size.4. The Regional Geotechnical Engineer or the Geotechnical Engineering Bureau should be consulted to determine the depth of the undercut and type of backfill material required. a concrete culvert should not be used.4. Wingwall/retaining wall design information is provided in Chapter 9 of this Manual and Section 11. The Geotechnical Engineering Bureau can provide an anticipated settlement amount. If the foundation material is extremely poor and it is desirable to limit settlement. there are several types that may meet the project specifications. If differential settlement cannot be avoided. a conservative estimate of the design reactions of all types should be used. The designer must decide which specific type of unit would best fit that particular application and use those vertical and horizontal reactions for design of the foundations. THE CONTRACTOR MUST SUBMIT A REVISED FOUNDATION DESIGN TO THE ENGINEER IN CHARGE IF THE ACTUAL LOADS OF THE SUPPLIED STRUCTURE EXCEED THESE ASSUMED VALUES.5. Arch-Topped Units. THE ASSUMED HORIZONTAL REACTION IS _____ kN/m. 19. Computer programs (C-WALL and BINWALL) are in the development stages for precast cantilever and bin type walls. The following note shall be included on the final contract plans: THE ASSUMED VERTICAL REACTION IS _____ kN/m.3 Precast Frames. 19. the problem should be referred to the Regional Geotechnical Engineer or the Geotechnical Engineering Bureau to determine the best course of action.3 of the Bridge Manual. However.4
A wingwall is a retaining wall placed adjacent to a culvert to retain fill and to a lesser extent direct water. A concrete box culvert can be considered if settlement is expected and the foundation material is fairly uniform.4 7/30/10
. THE REVISED DESIGN SHALL BE SUBMITTED AT THE SAME TIME THE DESIGN CALCULATIONS FOR THE THREE-SIDED STRUCTURE ARE SUBMITTED FOR APPROVAL. the culvert should be designed to accommodate additional dead load due to subsequent wearing surface(s) which may be needed to accommodate the settlement of the box. A typical remedy might be removal of unsuitable or unstable material and replacement with suitable material. If no specific type of unit is determined as most appropriate. Computer programs available for cast-inplace wall design are BRADD2 and WALLRUN. The current BD-CBx sheets show recommended foundation treatments.4. Concrete culverts are rigid frames and do not perform well when subjected to differential settlement due to a redistribution of moments.
can be extensive. A closure pour is not required if cast-in-place wingwalls are used.1
§19.14. Precast Precast Reinforced Concrete Three-Sided Structures
19.19. with NYSDOT modifications described in Sections 19.8 Distribution of Loads and Design of Concrete Slabs Culverts Reinforced Concrete Reinforced Concrete Box.2 . four-sided or three-sided) subjected to either earth fill and/or highway vehicle loading shall be designed in accordance with the guidelines in Sections 19.5 . utilities.24 Section 6 Section 8 Article 16.15 and 8. When precast wingwalls are allowed the designer should be aware of potential conflicts with ROW.1 Design Method The design method shall be either the Service Load Design Method (Allowable Stress Design) or the Strength Design Method (Load Factor Design) as described in Articles 8.
DESIGN GUIDELINES FOR BOX CULVERTS
Reinforced concrete box culverts (precast or cast-in-place.5. Cast-In-Place Reinforced Concrete Box.16 of the AASHTO Standard Specifications for Highway Bridges .19.Seventeenth Edition (AASHTO). The angle(s) of the wall(s) on the upstream end should direct the water into the culvert. Due to the skew and/or grade differences between the precast culvert unit and precast wingwalls it is necessary to do a cast-in-place closure pour between the culvert end unit and the wingwalls. The footprint of the footing and excavation. Note(s) should be placed on the plans alerting the Contractor to these requirements when they exist. etc.5. If assistance in the determination of appropriate type of wall is required contact the Geotechnical Engineering Bureau or Regional Geotechnical Engineer.6 Article 16. See the current BD-CBx sheets for details. especially for bin type walls.5.Seventeenth Edition have been used to develop these guidelines: Article 3. M&PT.14.7 Article 16. It is also desirable to have the top of the wall elevation at its end above the design high water elevation to prevent overtopping of the wall.5. The following sections and articles of the AASHTO Standard Specifications for Highway Bridges .REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES
and Construction Division. Wingwall alignment is highly dependent on site conditions and should be evaluated on a case-by-case basis.5.
If the culvert orientation is skewed relative to the over roadway and the design span exceeds 1. (120 pcf) = 24 kN/m3.2. (60 pcf max.4.5.6 and 6.1A Group X.B. soil. E.5.6.2. 19.3 for Dead and Earth Loads and 2. the computer program (Section 19.22. equal to 1..)
Maximum and minimum values of lateral earth pressure shall be investigated in accordance with AASHTO Articles 3.. The following criteria.4. shall be used in determining dead load and earth pressures for design: Soil Concrete Lateral earth pressure= = 19 kN/m3.2. E (measured in meters). 30 pcf min. where θ is the skew angle.2. Soil criteria shall be modified when using the Strength Design Method (Load Factor Design) in accordance with AASHTO Articles 16.3.2 and 16.83/sin θ. as given in AASHTO Articles 3.45 kPa min. In no instance shall the §19.22 and Table 3. Case B and modified as follows: Wheel loads shall be distributed over a distribution slab width. live load wheel loads shall be magnified by reducing the distribution slab width. by multiplying it by the cosine of the skew angle.19-10
19. For simplicity.2 and 6.22 + 0.5.5.3. 1. where S is the perpendicular distance in meters between wall centerlines.1.24.06S. (150 pcf) 2.17 for Live Loads in accordance with AASHTO Article 3. 19.9 kPa max. When the depth of fill is less than 600 mm.6) assumes the pavement as soil.3 Load Factors The product of the load factors [gamma (γ) x beta (β)] for the Strength Design Method (Load Factor Design) shall be equal to 1.7.2 Modification of Earth Loads for Soil Structure Interaction (Embankment Installations). wheel loads shall be distributed in accordance with AASHTO Article 3.5 Live Load Reinforced concrete box culverts shall be designed for MS-23 vehicle live load.5.5 12/16/05
.8. 19.2 Analysis Method The analysis of reinforced concrete box culverts shall be in accordance with AASHTO Article 8.20. and the concrete slab.4 Dead Load and Earth Pressure The dead load on the top slab shall consist of the pavement.
44 m & < 4.2. No live load surcharge need be applied when live load can be neglected in accordance with AASHTO Article 6.5E).2.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-11 distribution width exceed either 2. to 50 MPa. min.3.0 (0. Maximum wheel load magnification shall be limited to 2.4. 19.096 m $6. max. in multicell applications.44 m $2. shall be followed. For all fill heights where there is live load influence.2. as described in NYSDOT modifications of AASHTO Article 3.27 m $4.4. corner reinforcement as follows: CLEAR SPAN <2. wheel loads shall be distributed in accordance with AASHTO Articles 6.5. shall be controlled by design but shall not be less than 150 mm in any instance.8.7 Wall Thickness Requirements Exterior wall thickness requirements for reinforced concrete box culverts shall be controlled by design.5. 19.1 and 6. (increments of 5 MPa) f'c = 21 MPa
§19. except that minimum exterior wall thickness requirements have been established to allow for a better distribution of negative moment.4.8 Concrete Strength Reinforced concrete box culverts shall be designed for the following concrete strengths: Precast Cast-in-place f'c = 35 MPa. When the depth of fill is 600 mm or more. 19. Culverts with skews in excess of 60° shall be designed for a skew of 60°.5.13 m or the unit length of precast units. the lateral earth pressure shall have added to it a live load surcharge pressure equivalent to 600 mm of earth fill.8
.096 m MINIMUM EXTERIOR WALL THICKNESS 150 mm 200 mm 250 mm 300 mm
Interior wall thickness.5.6 Live Load Impact Factor The Live Load Impact Fraction I.27 m & < 6.
including the inside face of walls.2.8. welded wire fabric (plain). design reinforcement stresses at service loads shall be limited to satisfy the requirements for fatigue in accordance with AASHTO Article 8.10 shall be modified as follows: To provide for the lateral distribution of loads.16.2. Designs shall use a yield strength of 420 MPa for bar reinforcement and 450 MPa for welded wire fabric in accordance with AASHTO Articles 16.2.5 or 8.3.2. All faces of reinforced concrete box culverts not requiring design or distribution reinforcement shall be reinforced with the equivalent of #13 bar reinforcement at 300 mm centers in each direction. Minimum reinforcement shall be provided in accordance with AASHTO Article 8.7. and 16.6. 16. and 16.10. For skews > 60°. Shear reinforcement shall not be used in reinforced concrete box culverts. the amount of distribution reinforcement required shall be in accordance with AASHTO Article 3.6. the amount of distribution reinforcement required shall be in accordance with AASHTO Article 3.5.4.8.24. 16. all reinforcing steel in the top mat of the top slab shall be epoxy-coated or the concrete shall contain corrosion inhibitor. When the fill height over the box culvert is less than 600 mm.6. The maximum service load stress in the design reinforcing steel for crack control shall be in accordance with AASHTO Articles 16.7.16.10 Skewed Precast Units Skewed precast culvert sections shall be designed for the skewed end clear span. For skews # 60°.7.2.2.5.24.
§19.9 Reinforcement Requirements Reinforcement shall be either bar reinforcement.4. Distribution reinforcement as described in AASHTO Article 3.17.24.15. For culvert designs using the Strength Design Method (Load Factor Design). Under no circumstances shall any reinforcement be spaced greater than 300 mm. 19.1 at all cross sections subject to flexural tension.10.19-12
19. Slab and wall thicknesses shall be designed to have adequate shear capacity in accordance with AASHTO Articles 8. or welded wire fabric (deformed).5.7.7. distribution reinforcement shall be placed transverse to the main design steel in both the top and bottom slabs of reinforced concrete box culverts for fill heights less than 600 mm.10
.2 Equation (3-22).5.8.2 Equation (3-21).
5. where the ratio shall preferably not exceed 1/1000 of the design span.13 Deflection Limitations Top slab deflection due to service live load plus impact shall not exceed 1/800 of the design span. Level one load ratings shall be maintained in the Regional Office. and thrusts based on fully pinned support conditions that are able to resist horizontal forces and prevent horizontal displacements. unless spliced to top and bottom corner reinforcing steel.14 Span-to-Rise Ratios Three-sided box culverts and frames with clear span-to-rise ratios that exceed 4-to-1 are not recommended.23. the structure should be analyzed for midspan positive moment using pin-roller support 12/16/05 §19. If it is necessary to use a three-sided frame with a span-to-rise ratio in excess of 4-to-1. Calculations shall be certified and stamped by a professional engineer currently registered and authorized to practice in New York State and shall specify which method (Working Stress or Load Factor) was used in load rating computations. except on culverts located in urban areas used in part by pedestrians.5. Designers of these units typically compute moments.12 Load Rating Requirements Bridge-size culverts. Load rating calculations shall be based on the AASHTO HS or MS live-load vehicle. 19. Inventory and operating values shall be reported in either English or metric tons.5. shall require the submission of two (2) copies of detailed load rating calculations prepared in accordance with the current AASHTO Manual for Condition Evaluation of Bridges. as defined by the Uniform Code of Bridge Inspection. top and bottom slabs) shall be in accordance with AASHTO Article 8. outside-face. which are to be included in the record plans.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-13 19. shears.5.14
. As span-to-rise ratios approach 4-to-1. The minimum bending radius of negative moment reinforcing steel (outside corners. S. Precast box culverts shall be load rated by the fabricator’s licensed professional engineer and the load rating shall be shown on the approved fabrication drawings. Top and bottom slab. and positive moments at midspan can significantly exceed computed values even with relatively small horizontal displacement of frame leg supports. frame moment distribution is more sensitive to support conditions. 19.11 Detailing Requirements The minimum reinforcing bar cover requirements for cast-in-place and precast box culverts shall be as indicated in Section 15 of the Bridge Manual.2 Minimum Bend Diameters. transverse steel shall be full-length bars. 19.5. Cast-in-place box culverts shall be load rated by the licensed professional engineering designer and the load rating shall be shown on the contract plans.
Fully pinned support conditions could be used if site and construction conditions are able to prevent any horizontal displacement of frame leg supports. the designer must provide a complete design if the cast-in-place alternate is selected. Such a condition may exist if footings are on rock. the contactor/fabricator will be required to submit the design and fabrication details to the State for approval.6
COMPUTER DESIGN AND ANALYSIS PROGRAM
The Reinforced Concrete Box Culvert Design and Analysis Program. The program will design wall and slab thicknesses and required reinforcement. It has been distributed to NYSDOT Regional Structures personnel and the Precast Concrete Association of New York (PCANY). Standard details for precast concrete culverts are shown in the current Bridge Detail (BDCBx) sheets. the designer is required to provide a complete design for the contract plans.7
.5. precast) are proposed for a site. Culvert – Version 3. or as indicated in the contract documents. When a cast-in-place concrete culvert is proposed for a site. Using the span. This program will design and/or analyze a one-. This should be done within 45 days following the contract award date or as indicated in the contract documents. two-. If alternate designs (i. is used by the Structures Design and Construction Division. This should be done within 45 days following the contract award date.19-14
conditions. Questions regarding the use of this program or how to obtain a copy and/or a User’s Manual should be addressed to the NYSDOT Structures Design and Construction Division. or four-cell reinforced concrete box culvert with prismatic members (precast or cast-in-place).
19. and fill height.
19.e. All cells are assumed to be the same size for any one culvert and the clear opening dimensions remain constant. The bar schedule will be displayed for the entire length of a cast-in-place box culvert or one unit of a precast box culvert. the bar list table for the cast-in-place culvert unit may be omitted from the contract plans. rise. These standard details are available for use by designers in Microstation format.7
DESIGN AND DETAILS OF CONCRETE CULVERTS
Standard details for cast-in-place concrete culverts are shown in Figures 19-1 through 19-6. the program will design the box culvert by either Service Load Design or Load Factor Design. cast-in-place vs. three-. Once the contract has been awarded and an alternate is chosen. with or without bottom slab in accordance with the design criteria in Section 19. If a precast concrete culvert is proposed.0.
§19. and frame legs are keyed into footings with adequate details and construction methods..
♦ Any membrane waterproofing or top slab wash including any protective overlay for membrane protection (see Section 19. §19. ♦ Limit of stream work.7. measured from the top of the top slab to the top of pavement. and relation to new centerline. and type of acquisition.g.13). boring locations). ♦ New right of way line(s) including proposed ROW monuments. ♦ Stationing along the culvert centerline. ♦ Earth cover. ♦ Length of culvert. A longitudinal section (elevation) along the culvert centerline showing: ♦ Culvert or bridge identification number (BIN). ♦ Skew angle of the culvert relative to a line perpendicular to the centerline of roadway. if applicable. ♦ Limits of pavement work (e. ♦ Existing stream bottom or original ground. ♦ Culvert stationing including begin and end station. ♦ Typical highway section. ♦ Culvert or bridge identification number (BIN). ♦ Channel work. ♦ Scour protection. ♦ Stream flow direction.1
. ♦ Culvert end treatment (end unit or wing wall orientation). ♦ Slope protection.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-15 19. ♦ Invert elevations. ♦ Equality stations for the intersection stream alignment with the highway centerline. reconstruction. azimuths. ♦ Railing or barrier type. ♦ Limits of grading. ♦ Subsurface exploration locations (e. Refer to the Bridge Manual for information on plan standards for bridge-size culverts. shoulder widening). ♦ Scale bar.. map and parcel numbers. ♦ Culvert and highway alignment. ♦ Stream channel alignment. including beginning and ending station. • A plan view showing: ♦ Grid north arrow. ♦ Scour protection. ♦ Existing highway boundaries including existing ROW monuments. reputed owner. including any keyways or geotextile lining. four-sided box with cut-off walls). ♦ Culvert item number and description.g. resurfacing. ♦ Individual ROW parcels.7.1 Contract Plans The contract plans should include these minimum design details. ♦ Utility facilities (above ground and underground). ♦ Survey baseline: transit stations. including rail treatment. ♦ Foundation treatment (footing on rock or piles.. ties. ♦ All pertinent foundation details including bedding material.
longitudinal section. safety grate details. ♦ Slope and/or stream bank protection. in the embankment. ♦ Membrane waterproofing or top slab wash (see Section19. ♦ All pertinent foundation details including bedding material. and connection details.
A culvert section showing: ♦ Culvert clear span and rise.7.. Notes indicating: ♦ Live loading requirements: MS-23 unless another loading is required. A table of hydraulic data and the minimum hydraulic area perpendicular to flow below Design High Water shall be shown for culverts that are categorized by definition as bridges. ♦ Channel section detail. headwalls.1
. ♦ Excavation and backfill payment limits and items. or open end unit. or culvert section. ♦ Any utility facilities attached to the fascia. ♦ Chamfers. ♦ Temporary detour location including type. ♦ Wing wall sections showing excavation and backfill items and pay limits and appropriate excavation protection. ♦ Removal of existing culvert(s). and cutoff walls with elevations and dimensions. ♦ Erosion and sediment control and stormwater pollution prevention plan requirements 12/16/05
§19. barrier. ♦ Erosion and sediment control plan and/or stormwater pollution prevention plan. location on culvert. ♦ End unit treatment: Provide details for square.19-16
REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES ♦ Culvert end treatments.g. ♦ Low-flow dish. ♦ Hydraulic data: All culverts should show 50-year design flow (Q50) or the design flow used. reinforcement. apron slab and nosing information: Provide geometry. beveled. ♦ Culvert-end. ♦ End units or wing walls. ♦ Any other necessary information which cannot be clearly presented in the culvert plans. skewed. Miscellaneous details showing: ♦ Maintenance and protection of traffic including provisions for pedestrians ♦ Construction staging Information (determines lengths of segments and potential need for skewed segments) including appropriate excavation support and protection systems (e. sheeting). ♦ Cofferdams or water diversion. wing wall.9 and current BD-CBx sheets. and loading requirements for any necessary detour structures. ♦ Railing details: Locate the railing on the culvert and indicate how it is to be attached.13). keyway details. size. ♦ Headwall. See Section 19. cut-off wall. or sidewalk.
Note to designer: If a culvert has an identification number. If an extreme skew (e. Culvert Identification Number Plate.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-17 ♦ Restrictions for work in streams. The information in the tables should include:  Culvert or bridge identification number (BIN). This is based on an assumed top slab thickness.8. For a cast-in-place culvert..g. use the Culvert Program (Section 19.2 and 19. Cost of the plate shall be included in the various items in the contract.6) or manual calculations to determine the wall and slab thickness and required reinforcement. 19. staged construction. if draw connectors are to be left in place. ♦ Precast Culvert Requirements: See Designer Notes for Precast Culverts in Section 19. ROW issues. top slab.g. Precast design requirements are in Section 19.2
. ♦ Tables may be helpful for projects which involve multiple culverts. Cast-In-Place 12/16/05 §19. Under certain conditions (e. Squaring the ends will reduce the required top slab thickness.  Length. Include BIN special note in contract. Determine the minimum and maximum height of the fill. utility conflicts. the units may need to be skewed.5. the reinforcement.2 Design Procedure Determine the clear span and rise of the culvert using proper design procedures for the feature crossed (see Sections 19. See Chapter 8 of this manual for information on designing the opening of structures with spans of 6.. include a note stating: “Draw connectors are to be left in place and shall be galvanized in accordance with §719-01 of the Standard Specifications. ♦ Assumed wall.096 m or less crossing water features. a plate shall be placed or maintained in a similar fashion to a Bridge Identification Number (BIN) plate.  Item number and description. and bottom slab thicknesses.
Tables ♦ Tables as shown on current BD-CBx sheets.7.8. 60°) is necessary. which is the distance from the top of the roadway to the top of the top slab of the culvert. detour conflicts). squaring the ends should be considered if site conditions will allow.” ♦ Electrical safety requirements: See NYSDOT Bridge Manual. and edge beam requirements.3).  Mainline stationing.  Remarks.7. In addition.
Figure 19-1 Typical Cross Sections.
.19-18
Refer to §19.7.
.7. Cast-In-Place
Refer to §19.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-19 Figure 19-2 Wing Walls Plan and Elevation.
Figure 19-3 Contraction and Construction Joint.7. Cast-In-Place
Refer to §19.
.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-21 Figure 19-4 Wing Wall Plan.7. Culvert on Skew. Cast-In-Place
Figure 19-5 Wingwall Aprons.1
see Section 19. For reinforcement requirements of skewed precast culverts. This bar schedule is valid for cast-in-place and precast culverts. outside face vertical bars (design steel) Interior wall. When the fill height over the culvert is less than 600 mm. inside face vertical bars (design steel) Exterior wall. If the headwall or edge beam is a significant distance from the highway where it is not in danger from chlorides. In a cast-in-place concrete culvert with a skewed end unit.
§19. outside face transverse bars (design steel for multiple cells) Bottom Slab. All reinforcement contained within the headwall or edge beam including the reinforcement that extends into the top slab of the culvert shall be epoxy-coated and shall meet the requirements of §709-04 of the Standard Specifications or the concrete shall contain corrosion inhibitor.3
. inside face transverse bars (design steel) Bottom Slab. inside face transverse bars (design steel) Top Slab. all reinforcing steel in the top mat of the top slab shall be epoxy-coated or the concrete shall contain corrosion inhibitor. the top and bottom slab reinforcement will be "cut" to length to fit the skewed ends. The following bar label criteria shall be used for box culverts: Bar Identification Schedule (see Figure 19-1) A1 A2 A100 A200 A300 A400 B1 B2 B3 C1 C100 C200 Top Corner Bars (design steel) Bottom Corner Bars (design steel) Top Slab. the epoxy coating can be eliminated. bottom slab and wall longitudinal bars (temperature reinforcement) Top Slab.3 Reinforcement The main reinforcement in the top and bottom slabs shall be perpendicular to the sidewalls in cast-in-place culverts and nonskewed units of precast culverts. See Figure 19-6.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-23 19. vertical bars both faces (design steel) Top Slab.7.7. The "cut" transverse bars have the support of only one culvert sidewall and must be supported at the other end by the edge beam or cut-off wall. outside face transverse bars (design steel for multiple cells) Exterior wall.2. inside face longitudinal bars (design distribution steel) Bottom Slab. inside face longitudinal bars (design distribution steel)
See the Culvert Program User’s Manual for bars used less frequently.8.
Figure 19-6 Reinforcement Diagram. Cast-in-Place
§19.7.3
Headwalls 300 mm or less in height with no railing attachment may be either precast or cast-in.8
§19. Precasting permits efficient mass production of concrete units. The advantages usually more than offset the cost of handling and transporting the units to the site. is to stiffen the top slab of cast-in-place culverts that lose their rigid frame action as a result of having a skewed end. Headwalls that are over 300 mm in height or have a railing attachment should be cast-inplace. The typical maximum height of headwalls is 900 mm. Design and analysis of the headwall is required for heights above 1. When the edge beam is at shoulder elevation (anchoring guide rail). the headwall must be cast-in-place to allow for the tie-in of the curb's anchor bar. unless the curb is also placed at the precast plant.place.10). In shallow fills the headwall may retain the subbase and/or highway pavement and provide the anchorage area for the railing system.8
Precast concrete culverts are fabricated in a plant where the ability to control placement and curing conditions typically results in higher strength and more durable concrete.8 m. In deep fills a headwall helps retain the embankment. When additional strength is required in the concrete edge beam. An edge beam is very similar to a headwall in that it may be used to anchor guide railing posts or retain earth fill. Greater heights are attainable but are only used in special cases. The majority of concrete culverts installed are precast.7. it will be more economical to increase the depth of the edge beam in order to meet the required design. the edge beam height should be maintained and the width of the edge beam should be increased. Assistance in edge beam and cut-off wall design may be obtained from the Structures Design and Construction Division.4 Headwalls/Edge Beams Headwalls are normally used on all culverts. Cast-in-place culverts with skewed ends may require additional stiffening of the top and bottom slabs by what is most commonly called an "edge beam" in the top slab and a "cut-off wall" in the bottom slab.
19. A cut-off wall will stiffen the bottom slab as well as prevent water from undermining the culvert (see Section 19.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-25 19. Its main purpose. See the current BD-CBx sheets for the minimum required reinforcement for heights up to 1. If a curb must be placed on a culvert without a sidewalk. the following criteria shall be used: If there is a 1-on-2 slope to the edge beam.8 m.
In culvert installations with skewed end units. Skewed precast culvert units should be avoided. and reinforcement size and spacing should not be shown on the plans. unless necessary. If sidewall or top slab dimensions are dictated by site conditions. In the event they are necessary. The units that meet at the division of the stages may need to be skewed to provide adequate width for travel lane(s).1 12/16/05
. Skewed units are sometimes required to satisfy right-ofway constraints and/or staged construction requirements for skewed alignments. maximums. Precast fabricators should be contacted for the maximum grade that can be fabricated if the designer is proposing a grade larger than 2%. When the slope of the culvert exceeds 5%. The assumed top slab dimension used to determine fill limits should be shown in the table as indicated in the current BD-CBx sheets.4 should be limited to a maximum slope of 2%. Large skews may lead to units that require additional reinforcement and/or greater wall and slab thickness than typical square units with the same clear opening. Staged construction is an example of a special requirement which may require skewed interior units.8. Precast culverts may regularly need to be placed on moderate or steep grades. show only affected dimensions and indicate if they are minimums.19-26
Precast units are limited to certain sizes and skews due to transportation and handling concerns. When two or more single-cell.8. In culvert installations with square end units. the footings can be stepped and/or the length of the sidewall varied. No maximum slope is recommended for box culverts because of the need to match the slope of the streambed. Skewed units may need more reinforcement and thicker slabs and/or sidewalls. A note in the contract plans shall require the manufacturer. skewed precast culvert units shall be designed for the skewed-end design span. the top of the cut-off wall should be beveled to match the slope. each interior unit will routinely be square unless the designer has included special requirements in the contract documents. Fabricators should be contacted for information on maximum skews available. §19. whenever possible.8. This gap should be filled with any concrete item in the project or Class D concrete if no other concrete item is available. If matching a steep streambed slope is necessary for a three-sided culvert. larger three-sided box culverts and the frames and arches discussed in Section 19. It is reasonable to detail a 50 mm to 100 mm gap between the walls of adjacent cells. to provide all design details not included in the contract plans. precast concrete culverts are placed side-by-side. the interior units will routinely be square and the end unit skewed at each fascia. Precast concrete culverts should have square ends. or specifically required dimensions. The use of skewed units will increase the cost of the culvert due to increased fabrication costs.1 Contract Plans Dimensions of the sidewalls and top and bottom slab. if practical. through the contractor. This method should result in the most economical culvert design. this will usually be determined by the manufacturer of the precast units unless the designer has included special requirements in the contract documents. 19. However. However. it is usually not possible to place the walls of adjacent cells tightly together.
8. However.6) is used to design the culvert. When a precast end unit is skewed.4 Precast Frames. more importantly. there are various types of proprietary. large skews may require more reinforcement and can increase the design span to the point where increased slab thickness may be necessary.
§19. the Contractor shall be responsible for providing them. If the Culvert Program (Section 19. Fabrication requirements of precast concrete box culverts are contained in §706-17 of the Standard Specifications. and arches available. archtopped units. The drawings and the design calculations shall be stamped by a professional engineer licensed to practice in New York State. 19. the design span of the end unit. the splayed reinforcement is usually more than adequate. precast concrete frames. the program input and output sheets shall be submitted for the design calculations. and Arches In addition to box units.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-27 19. Precast concrete culverts with skewed ends cannot use edge beams as stiffening members because of forming restrictions.6 m) are possible.7. For small skews. Where appropriate. thereby leaving main reinforcement parallel to the centerline of the over roadway. or pile-supported footings.2 Reinforcement The main reinforcement in the top and bottom slabs shall be perpendicular to the sidewalls except in skewed units.3 Design and Fabrication When contract plans do not contain complete design details for the precast concrete culvert. 19.4
. If the sidewalls of a three-sided culvert are rotated to accommodate the skew angle. For this reason. to fit the skewed end unit. These units are typically used when larger culverts (spans ≥ 6 m ±) are required. They can be considered when hydraulics can be adequately provided and/or aesthetics are a consideration. All design submissions from the Contractor shall include a complete set of working drawings and a complete set of design calculations. the three-sided culvert shall be designed for the design span parallel to the main reinforcement. footings on rock.3 for bar identification schedule. See Section 19." as in cast-in-place culverts. the transverse reinforcement must be splayed to fit the geometry of the skew. Arch-Topped Units. This splaying of the reinforcement will increase the length of the transverse bars and.8. except that longer spans (up to 14. transverse reinforcement cannot be "cut.8. The advantages of the precast concrete arches and frames are the same as for the precast concrete box culverts.8. they may be placed on a combined invert footing/slab.
shall be designed for use with #16 and #19 reinforcing bars. See the NYSDOT Bridge Manual.5 Designer Notes for Precast Culverts 1. Concrete culverts may be “highway size” or “bridge size” by definition. when used in 35 MPa concrete. for more information. The drawings and the design calculations shall be stamped by a professional engineer licensed to practice in New York State. Inserts shall be noncorrosive and.
19.9 12/16/05
. §19. H is the height of the headwall above the top of the top slab.3 m#H#1. Any roadside protection placed at a culvert should be provided as highway guide rail or as bridge rail or barrier. The Structures Design and Construction Division will assist the Materials Bureau in this function by providing quality assurance reviews of the culvert designs. Section 6.
3. The female-threaded portion of the connector is cast into the box culvert.9
GUIDE RAILING
The Department has set policy that requires highway rail to meet NCHRP 350 Test Level-3 (TL-3) and requires bridge rail to meet AASHTO LRFD TL-4 in most situations. the guide rail requirements can theoretically vary by span of structure. where detailed. The Contractor shall be responsible for providing all design computations and details for these units.19-28
19. Threaded inserts. able to resist minimum pull out loads of 49 kN for #16 reinforcing bars and 71 kN for #19 reinforcing bars. Design calculations for all box culverts shall be submitted to the Department and retained in the project design folder.8 m are to be attached to the box culvert by use of mechanical connectors for reinforcing bar splices meeting the requirements of §709-10 (epoxy-coated) of the Standard Specifications.8. All shop drawings require a quality assurance review for general compliance of contract requirements and for suitability of the design for the given design conditions. and therefore. The use of culvert rail is no longer acceptable because it is not an approved. The Deputy Chief Engineer Structures has design and shop drawing approval authority for precast concrete arches and frames.8 m. See current BD-CBx sheets. Precast concrete box culvert designs are delegated to Contractors who are required to provide designs by a New York State licensed professional engineer as part of the box culvert pay item. specific design information must be provided in the contract documents.8.6 Design and Shop Drawing Approvals The Materials Bureau has design and shop drawing approval authority for precast concrete box culverts. Fabrication requirements of precast concrete arches and frames are contained in §562 of the Standard Specifications. crash-tested system. Headwalls where 0. For headwalls where H>1.
Culverts between 1. The transition of the concrete barrier shape to the transition rail will use up most of the length of barrier on the culvert. 3-. • Culverts with less than 1. large skews and/or large sidewall thickness) maintaining the required 600 mm between the first/last transition post and the first/last culvert post may require special details beyond those in the BD-CBx sheets. For bridge rail details. See Chapter 10 of this manual for guidance on the required length of posts. For railing anchorage to headwall details.8 m transition from the end of barrier to the full. or pedestal.0 m outside width (rail length) and less than 900 mm of fill may have posts attached to the top of the box or posts shortened. edge beam. edge beam.9
. 4-. single-slope barrier has a 4. Placement of anchor plates and bolts in the top slab should be avoided because it creates significant forming problems. If there is more than a minimum of 900 mm of fill and the standard 700 mm shoulder break area and a 1 on 2 or flatter slope. The anchor plate that goes under the top slab must be located so it does not encroach into the haunch.830 m and box beam guide rail. This assumes the use of standard post spacing of 1. see the current BD-RSx sheets.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES 19-29 The anchorage/support of the guide railing is determined by the amount of fill over the top of the unit..
Concrete barrier is generally not recommended due to the short length of culverts unless it is being connected to barrier along the highway. use of common highway guide rail with standard length posts is recommended. the preferred option for guide rail depends upon the amount of fill and the size of the culvert as described below. In these situations. See EI 04002 for guidance on the appropriate option.830 m. Designers should note that the location of the first and last posts is critical on culverts with headwalls < 300 mm high. the 1. the 900 mm criteria is no longer valid. If assistance is required contact the Regional Structures Engineer or the Structures Design and Construction Division.g. Highway guide rail should be used whenever it meets applicable safety standards since it is the most cost-efficient railing/barrier type. In some special circumstances (e.
§19. When the recommended offsets from the back of the posts to the shoulder break cannot be achieved or the embankment slopes away from the normal shoulder break steeper than a 1-on-2 slope. When the guide rail is anchored to a headwall. extra-long posts are required.5 m outside culvert width requirement should be adjusted accordingly. see the current BD-CBx sheets. For example. If post spacings are less than the standard post spacing of 1. either bridge rail (2-rail with curb. singleslope shape. or 5-rail) or concrete barrier shall be used.0 m outside widths (rail length) and less than 900 mm of fill should have guide railing anchored into a headwall. or individual concrete pedestals. Culverts with more than 3.5 m and 3. When there is less than 900 mm of fill.5 m outside widths (rail length) and less than 900 mm of fill should have the posts straddle the outside of the culvert.
The depth of the dish depends on the quantity of flow. to inspect the bottom slab. The cutoff wall should be a minimum of 1. For cast-in-place culverts with skewed ends. the cut-off wall should be cast-in-place.2 m below the invert elevation or to the top of sound rock if the rock is closer. When precast concrete cut-off walls are specified. if not impossible.12) is specified. material washed out during high flows will be replaced with new material as the water recedes. The depth of the concrete covering the reinforcing bars should be increased if this situation is anticipated. When cut-off walls are required.6) will design the bottom slab of a culvert with a low-flow dish. See Figures 19-2 or 19-5 or current BD-CBx sheets.
19.10 CUT-OFF WALL A minimum 450 mm wide cut-off wall is required in all culverts with invert slabs to prevent undermining. Midspan and end moments of the bottom slab are calculated assuming a prismatic section using the slab thickness at the thinnest location. they shall always be specified at each end of the barrel. Note that covering the bottom slab with native material will make it very difficult.
§19. but there may be times when the dish will be at or near the sidewall. Sometimes it may take several lesser flows for the material to be replaced. The Culvert Program (Section 19. If the apron is continuous with the barrel the cut-off wall is only required at the end of the apron. A typical dish is shown in the current BD-CBx sheets. The bottom of all wingwall footings should be at or below the bottom of the cut-off wall to prevent scour around the edges of the cut-off wall. The program will evaluate the additional shear capacity provided by the dish when requested by the designer. the cut-off wall may be precast or cast-in-place. One problem that may occur is the movement of the native material during high flows. Lower flows may require a deeper dish to provide adequate depth of flow. When a cast-in-place culvert is specified. This may happen when the stream is on a curved alignment and the low flow of the stream is on the outside of the curve.11
. This periodic movement of material may abrade the surface of the concrete culvert. their cost should be included in the cost of the culvert barrel or invert slab. Native streambed material is sometimes required by the DEC over the top of the bottom slab. an additional cut-off wall shall also be specified at the end of the apron. When a precast culvert is specified. The depth of the dish may be as small as 150 mm or as large as 300 mm. When a concrete apron (Section 19.19-30
19. No separate item is required. Typically.11 LOW-FLOW DISH Box culverts shall have a low-flow dish whenever the stream is classified as a fishing stream by the Department of Environmental Conservation (DEC) and a low-flow dish is requested. The dish is usually in the center of the invert slab. the cut-off wall also provides stiffening of the bottom slab. The typical depth requirement is 300 mm.
Some Regions prefer to use heavy stone filling for all structures and other Regions prefer to use heavy stone filling when lower velocities are reached. Baffles are concrete sections that extend 300 mm to 750 mm above the bottom slab. Concrete aprons may fail from frost heaves. a concrete apron may be used. The longer the culvert and the steeper the slope. bed load material abrading the apron. The Regional Hydraulics Engineer or the Structures Design and Construction Division Hydraulic Engineering Unit should be consulted to determine an appropriate length of apron for special situations such as locations where excessive scour has occurred. a stone apron shall be placed at the outlet of all culverts.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES
19. If the apron is continuous with the barrel the cut-off wall is only required at the end of the apron.12 APRONS Box culverts can significantly increase the stream flow velocity because the concrete has a roughness coefficient significantly lower (i.12
. a three-sided culvert on a strip footing on piles should be investigated. The stone apron should cover the full width of the streambed. The cut-off wall at the end of the culvert barrel is added protection if the apron fails or separates from the barrel. If a concrete apron is specified. medium stone filling may be used. This is acceptable practice since the integrity of the structure is not compromised. or where the existing soils are very poor.. The Regional Hydraulics Engineer or the Structures Design and Construction Division Hydraulic Engineering Unit should be consulted to determine the need for and the design of energy dissipators. heavy stone filling or larger should be specified. It should extend to the end of the wing walls (see Figure 19-5). In addition. a stone apron should be specified at the inlet of all culverts to prevent scour caused by the constriction of flow. 12/16/05 §19.2 m deep key of stone filling should be placed in the streambed at the end of the apron away from the culvert. the stone apron will begin at the end of the concrete apron. The recommended minimum length of the stone apron is 7. steep profiles.e. When stream velocities are very high (>5 m/s).5 m. A cut-off wall (Section 19. Stone apron and slope protection details can be found on BD-EE7. the more the velocity will be increased. Stone filling should also be used to stabilize all disturbed slopes to a minimum elevation of 300 mm above Design High Water. or other unique situations. where special site conditions exist. The size of the stone filling shall be determined by the design velocity or Regional preference. The movement of cobbles and boulders may damage a concrete invert. energy dissipators (baffles) may be required to reduce the velocity. A 1. In addition. For design velocities of 3 m/s or higher. whichever is larger. or special circumstances. To dissipate this increase in energy and to prevent scour. stone filling should be placed on the side slopes to a minimum elevation of 300 mm above Design High Water.10) is required at the end of the concrete apron and at the end of the culvert barrel.5 m wide by 1. The stone apron will begin at the end of the barrel if no concrete apron is specified. For design velocities less than 3 m/s. Where there is significant movement of cobbles and boulders in the bed load. smoother) than the streambed and banks. For some unique situations with very high-water velocities.
The slope is very important. the concrete apron and wing walls may be precast or cast-in-place. and become a continuous maintenance problem. Contact the Materials Bureau or the Regional Materials Engineer for guidance when considering the use of a concrete pavement section. The minimum depth of concrete required is 150 mm.
§19. The designer must understand that the purpose of the waterproofing membrane is to restrict seepage of water or migration of backfill material through the joints in the culverts and it is not intended to protect the concrete. centered on the joints. All flat-topped or nonarched culverts should have a minimum longitudinal slope of approximately 1%. or farm animals. the precast units may be posttensioned together. and then extending down the sidewalls to the footing. can be used. The wash can be from the centerline to each side or all in one direction. they may be included in the cost of the culvert barrel.13 SUBBASE DRAINAGE Draining surface and ground water away from the culvert through the subbase is just as important as the conveyance of water through the culvert. covering the top slab. their costs should be paid by separate item. In cases where it is desirable to have a dry environment. An acceptable option in low fill conditions is to place a concrete pavement on top of the culvert. to drain the water that permeates through the pavement and subbase.
19. a 1% slope (wash).3 m±) or asphalt directly on the culvert. If there is concern about movement of the units cracking the concrete pavement. Even though a joint sealer is always placed between individual precast concrete culvert units and the units are pulled tightly together. in situations where there is low fill (0. A waterproof membrane may be used to cover the joints of precast concrete culverts that convey water through the culvert. perpendicular to the centerline of the culvert. When a cast-in-place culvert is specified. Culverts will occasionally be used to allow the passage of things other than water. the wash can be added after the culvert is in place by placing a shim course of asphalt or concrete. to limit the likelihood that water will pond. When precast concrete aprons and/or wing walls are specified.19-32 REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES When a precast box culvert is specified. If a longitudinal slope is not possible. cause potholes.13
. trains. golf carts. including but not limited to pedestrians. if necessary. bicycles. water may seep through the joint. The minimum requirement for waterproofing these joints is to provide a membrane strip having a minimum width of 600 mm. The wash can be formed into a cast-in-place culvert but is difficult to form on precast culverts. On precast culverts. a waterproof membrane should be used to cover the joints between precast culvert units or to cover the construction joints in cast-in-place culverts. if possible. away from the top of the culvert. the concrete apron and wing walls should be cast-in-place. In some instances. The concrete pavement is less susceptible to potholes than asphalt but is more costly and should have a longer service life. freeze.
Section 11. See the Bridge Manual. cause damage to a waterproofing membrane. for location and spacing requirements.REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES
If the waterproof membrane is extended down the sidewall to the footing. When watertight joints are required. The joints between culvert segments can have inconsistencies that may. This item contains all the material and construction details necessary for the application of the system. over time. An asphalt wash/shim course can protect the membrane by providing a smoother surface on which to place the membrane. weep holes may be necessary. In these instances a sheet membrane should be used on top of the culvert.13
. contact the Materials Bureau for the proper waterproof membrane item to be included in the contract.
D. and all addendums. New York State Department of Transportation. 444 North Capital Street. New York State Department of Transportation. New York State Department of Transportation. 444 North Capital Street. Structures Design and Construction Division. Suite 225. W.
5. New York State Department of Transportation. Design Quality Assurance Bureau.
4. Structures Design and Construction Division. Structures Design and Construction Division. Model Drainage Manual. Reinforced Concrete Box Culvert Design and Analysis Program User Manual.14 REFERENCES 1. Albany. American Association of State Highway and Transportation Officials. Albany. Standard Specifications for Highway Bridges. January 2. NY 12232. NY 12232. N. American Association of State Highway and Transportation Officials. C. Albany.19-34 REINFORCED CONCRETE BOX CULVERTS AND SIMILAR STRUCTURES
19. Washington. Bridge Manual. Suite 249. 2002. 20001. NY 12232. April 2002. and all addendums.14
. March 2005. D. NY 12232. Albany. Washington.
3. 20001. W. Bridge Detail Sheets BD-CBx. 2005. 3rd Edition. 17th Edition 2002. Standard Specifications of Construction and Materials. N. C.
...............................................................4....7.................3................................................................... 19........................ 19.............................3............................................................................ 19....... 19...............................................................................1.............7............................................... 19......10...............1 Edge Beam ........................................CHAPTER 19 INDEX SUBJECT SECTION
Apron.......................... 19.......7.4..............7.........................12 Fabrication ...... 19..........2 Culvert Reinforcement ................ 19....... 19......................8................. 19.................6........................................................................................... 19......................................4...............1 ................................... 19...............1 Contract Plans................... 19...............5............ 19............... 19....... 19.................9............... 19......................... 19..9 Energy Dissipators ....13 Precast Culverts ......................13 Wingwalls ........................4 Headwall ............................................8.. 19.............7 Clear Span ........ 19............ 19..4............................ 19......1 Design Span.......... 19....7............... 19...................................19..............................................1 Corrugated Metal Structure ......8........................ 19...........9 Culvert ..............................12....7........... 19.7.................7.....5. 19............................................................................... 19...........10
.......7................ 19.........................................11 Load Rating .............................................................9 Low-Flow Dish...........................4.............................3................3..............................3 Foundations .. 19...................................................... 19..............................3.................... 19..............................12 Box Culvert Computer Design Program ........ 19................................... 19..............10...... 19.......2 Culvert Railing ........... 19...... 19.............. 19.........................................12 Membrane ....... 19........ 19....................................................3.......................................7....................................4...14 Cutoff Wall.....3...........3.......................................................................... 19..8.........................2....................................................................................4 Skewed Culverts ........................................ 19............................................................ 19...........8 Precast Arches and Frames.......................... 19...4........12 Two-Cell Culvert.......10 Cast-In-Place Culverts .......10....................7.......... 19.................................................................................8........ 19..2 Stone Filling ........................ 19..............................................8......................................3................................ 19.......... 19.....5... 19..........................................................2.............................12 Definitions ...............................................................................................8 Waterproof Membrane .................... 19.................................2...........................................
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