A New Approach to the Accelerated Fabrication of Resilient Steel Bridges: Built-Up Press-Brake-Formed Tub Girders

This dissertation investigates a novel approach for the accelerated fabrication of resilient steel bridges: built-up press-brake-formed tub girders (PBTG). Built-up PBTG bridges are made up of cold bent webs (bent via a press brake) bolted to flat top and bottom flange plates with a cast-in-place concrete deck. In contrast to existing PBTGs that are cold bent from a single steel plate, this is a built-up system in which webs are cold bent and bolted to separate, flat bottom and top flange plates. It offers enhanced versatility, as this is a “kit-of-parts” where different sizes of components can be used to achieve required capacities or span lengths (e.g., thicker bottom flanges for negative moment regions, and deeper webs for longer spans). Specific objectives investigated include: (1) Numerically investigate the behavior of built-up PBTG bridges under service and fatigue design loads as well as during construction, (2) Experimentally and numerically investigate the behavior of built-up PBTG bridges under live loads, (3) Compare and contrast three methods of designing and analyzing built-up PBTG bridges, and (4) Perform an exhaustive study of discrete web and flanges sizes to develop a kit-of-parts that will facilitate the adoption of this approach. To comprehensively evaluate the performance of built-up PBTGs, two demonstration bridges were constructed in Indiana: an 86-ft simple span bridge with no skew and a 191-ft two-span continuous bridge with a 15-degree skew. Numerical and experimental analyses were conducted on these bridges. Numerical findings confirmed the feasibility of the approach, demonstrating minimal stresses under service loads, well below the yield strength of the steel. Live load testing on the constructed bridges involved measuring strains using BDI strain gauges. The collected data were instrumental in refining the numerical modeling approach for the built-up PBTG system. To facilitate the adoption of this innovative approach, an extensive study was conducted to identify readily available cross-section sizes. This led to the development of a standardized kit-of-parts catalog, enabling the system's application to various span arrangements and lengths. This dissertation addresses the limitations of traditional steel bridge construction, particularly long lead fabrication time and complicated shop drawings, while offering a competitive alternative to prestressed concrete girders.