Post-tensioned Concrete Haunched Slab Bridge Standards

Complete Phase 1 Report

User's Manual for Standard Details

PT Slab sample details (Download a zipped set - 13 sheets; Microstation ".dgn" format)


The Kansas Department of Transportation has developed standards for the design  and construction of post-tensioned concrete haunched slab bridges. KDOT  currently has standards for reinforced concrete haunched slabs from 12 m (39  ft) to 22 m (72 ft) center span range. Post-tensioned concrete haunched slabs  standards will extend the span range capabilities of the shallow-depth slabs  from 20 m (66 ft) to 28 m (92 ft), in addition to providing a high performance  type bridge superstructure.

General Design

The slab bottom (soffit) has a parabolic profile with minimum depth at mid-span  and maximum depth at pier. Longitudinal post-tensioning tendons are draped in a  parabolic profile, which provide primary resistance to the loads. A nominal  prestressing is provided in the transverse direction using straight tendons for  distribution of loads and confinement. Nominal mild steel reinforcing is  provided in both directions, at the top and bottom of slab, for temperature and  shrinkage as well as to assist in the placement of the post-tension tendons.

Spans and Roadways

Four (4) span arrangements will be available in a continuous three (3) span  configuration.

Group A:15 - 20 - 15 m (50-65-50 ft.)
Group B:17 - 22 - 17 m (55-72-55 ft.)
Group C:19 - 25 - 19 m (62-82-62 ft.)
Group D:21.5 - 28 - 21.5 m ( 71-92-71 ft.)

            Six (6) roadways will be available for each span group:            


8.6 m (28 ft.)   9.8 m (32 ft.)   11.0 m (36 ft.)   12.2 m (40 ft.)   40 ft. OS    13.4 m (44 ft.)


Design Loads

Dead Loads:

Concrete Dead Load = 22.8 kN / m3 ( 145 pcf)

Traffic Barrier Load = 4.0 kN / m ( 275 plf ) per rail

Future Wearing Surface = 1.2 kPa ( 25 psf )


Live Loads:

Live load design is accompanied by a corresponding allowable concrete tensile  stress limitation.

3 * f'c^0.5 maximum tension for HL-93 Loads (LRFD).

The superstructure is designed to satisfy current AASHTO LFD (Load Factor  Design) and the future AASHTO LRFD (Load Resistance Factor Design) design  specifications.


Load Rating:

The goal of design load rating for the given span ranges, governed by the  standard HS-20 Truck among all seven (7) Kansas load rating trucks, is 1.10.

The design of "larger" span groups C and D spans results in a minimum  1.10 rating for the HS-20 truck.

The design of "smaller" span groups A and B spans results in a minimum  1.10 rating for the HS-20 Truck for maximum positive and negative moments, and  a minimum 1.05 rating for negative moment near mid-span of the exterior spans.


Load rating table shown on plans complies with HS-20 for Operating, Inventory and H.E.T. for operating.




An example of a 30 degrees skewed structure is available                for download as reference material. Below is a partial list of considerations for skewed post-tensioned haunched slab bridges.

  • Longitudinal post-tensioning details                  are expected to be substantially unchanged.
  • Transverse post-tensioning                  details will require modifications to accommodate skew and potential                  conflict with rail post reinforcement.
  • Anchor end recess will also                  require special details to accommodate the skew.


Multi-span Applications

The current standards for post-tensioned concrete haunched slabs are limited to  three (3) continuous span arrangement. Unlike the standards for the  conventional reinforced concrete haunched slabs, post-tensioned concrete slab  design cannot be extended to multi-span application in a straightforward  manner. The additional length of tendons results in increased loss of  prestress, which may require additional prestress. KDOT may, in the future,  develop standards for multi-span applications. In any event, the maximum total  length of post-tensioned concrete slab bridges, without introducing a strand  splice or interior span joints, is expected to be about 180 m ( 600' ).


The standards are available in three components:

  1. The user's Manual - PDF file format
  2. Plan standards - Microstation ".dgn" drawing file format
  3. Project Special Provisions ( Construction specifications for post-tensioned  concrete haunched slab bridges ) - Microsoft Word file format

Kansas Department of Transportation
Bureau of Structures and Geotechnical Services
Dwight D. Eisenhower State Office Building
700 SW Harrison Street
Topeka, KS 66603-3754
Phone: 785-296-3761
                                      Attention: Mr. Loren Risch, PE - Bureau Chief
or                                    Mr. Terry Fleck, PE - Assistant Bureau Chief

PB Booker Associates Inc. ( Consultant )
225 N. Market, Suite 350
Wichita, Kansas 67202
Phone: 316-263-6121
Attention: Mr. Raja Govindaswamy, P.E. - Engineering Manager