Short Span Steel Bridges 
Texas Public Works Uses Prefabricated Bridge for Replacement Project
Project Overview
When the County of Bexar (Texas) Public Works Department needed to replace the deteriorated Ira Lee Road box culverts over Salado Creek, they also needed to increase the flowable waterway area provided by the five box culverts. Due to the increased volume observed in recent years, a 104-foot-long, two-span bridge utilizing standard AASHTO Type IV prestressed concrete I-beams was specified. The county was approached by the award contractor with an alternative press-brake-formed steel tub girder superstructure that would not only increase the necessary waterway area beneath the bridge by 20 inches, but would also reduce the construction schedule by up to 45 days.
The County of Bexar (Texas) Public Works Department needed to replace a deteriorated box culverts bridge.
Project Details
For the bridge superstructure, a press-brake-formed steel tub girder superstructure system called Con-Struct™ Prefabricated Bridge was chosen by the contractor for its ease of construction and short lead time (less than 8 weeks). The Con-Struct™ Prefabricated Bridge System consists of a precast concrete deck cast compositely on a galvanized press-brake-formed steel tub girder. The press-brake-formed steel tub girders were formed at Willbanks Metals in Tulsa, Oklahoma. The entire superstructure was then assembled at Tricon Precast, Ltd. in Houston, Texas. Tricon Precast provided a quality, cost-effective final product.
Con-Struct™ was designed for the required AASHTO LRFD HL-93 live load and to meet all applicable Texas Department of Transportation (TxDOT) and AASHTO design criteria. The 8-inch-thick precast concrete deck was provided with a tined final driving surface. The 52-foot span galvanized steel tub girders were 18-inches- deep, providing a total superstructure thickness of 28 inches. This shallow superstructure depth allowed for an additional 20 inches of clearance below the bottom of the girder.
The 52-foot span galvanized steel tub girders were 18-inches deep.
Shipping
The superstructure was transported to the construction site on standard individual truck trailers. Each 52-foot-long by 7-foot-wide unit weighed only 21 tons and required only a single 150-ton crane for erection.
The superstructure was transported to the construction site on standard individual truck trailers.
Installation
The 16 Con-Struct™ bridge units started to arrive at the job site by 7:00 a.m. All units were set in place by 2:00 p.m. the following day. Once set in place, high-strength, non-shrink cementitious grout was placed in the keyways between the bridge units to create one continuous 56’-4”-wide concrete deck.
The bridge was set in less than 2 days.
Final Product
With the sidewalks and barriers formed and cast, over the next few weeks the bituminous approaches will be paved and the final riprap placed in all four quadrants. The County of Bexar Public Works Department was able to successfully replace the existing deteriorated box culverts and avoid costly rain delays by using innovative Con-Struct™ galvanized press-brake-formed steel bridge elements. With the use of the Con-Struct™ Prefabricated Bridge System, this project provided a new structure that is sustainable, cost-effective, aesthetically pleasing and environmentally friendly.
Press brake tub girders.
Completed bridge
Read the full case study from Valmont Structures.
Ira Lee Road Over Salado Creek Bridge Project Team:
Owner
Bexar County Public Works
Todd M. Putnam, P.E., C.F.M.
Civil Engineer
Tel: 210.335.6696
Email: tputnam@bexar.org
Website: http://www.bexar.org/1380/Public-Works-Department
Contractor
Tropical Contracting, LLC
Charlie Winters
Project Manager
Tel: 210.224.7920
Email: cwinters@tropicalcontracting.net
Website: https://www.tropicalcontracting.net/
Bridge Fabricators
Willbanks Metals
Gabriel Castillo
General Manager
Tel: 918.836.2929
Email: gabe.castillo@willbanksmetals.com
Website: http://www.willbanksmetals.com/
Tricon Precast Limited
Robert (Bobby) Lys, Jr., P.E. (TX)
Sales Engineer
Tel: 281.931.9832
Email: blys@triconprecast.com
Website: http://www.triconprecast.com/
Engineer
Valmont Structures
Guy C. Nelson, P.E., S.E.
Structural Engineer
Tel: 616.261.8630
Email: Guy.Nelson@valmont.com
Website: http://www.constructbridge.com/
What are Press Brake Tub Girders?
Press-brake-formed tub girder (PBTG) is a new technology for short span bridge applications. It consists of modular galvanized shallow trapezoidal boxes fabricated from cold-bent structural steel plate (watch fabrication video). A concrete deck is recommended to be precast on the girder and the modular unit can be shipped by truck to the bridge site.
The system utilizes standard plate widths (based on availability) and is optimized to achieve maximum structural capacity, with most of the steel in the bottom flange and increased torsional stiffness. It is a closed system, since the girder is closed at the bottom. It is versatile for multiple-deck options.
The system utilizes Accelerated Bridge Construction practices, since it:
- Can be installed in one or two days
- Is modular, allowing the use of a precast deck
- Is cost-effective―as much as 1/3 less than a standard concrete girder structure
- Is simple to fabricate, requiring very little welding.
The Short Span Steel Bridge Alliance has developed standardized plans using standard plate sizes (60”, 72” 84”, 96”, 108”, 120”). The designs were developed to achieve maximum structural capacity and are available to use in the free-to-use, web-based design tool eSPAN140.
The press-brake-formed tub girder system is open source.
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