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.

本论文探讨了一种加速制作耐久型钢桥的创新方法：由拼装式冷弯折弯管形梁（PBTG）组成。拼装式PBTG桥梁由冷弯的腹板（通过折弯机弯曲）与预制的混凝土桥面板连接而成的平面顶板和底板螺栓连接而成。与现有从单一钢板冷弯而成的PBTG相比，这是一种拼装系统，其中腹板通过冷弯并螺栓连接到独立的平面底板和顶板。它具有更高的通用性，因为这是一个“部件套件”，可以通过使用不同尺寸的部件来实现所需的承载能力或跨度长度（例如，对于负弯矩区域使用较厚的底板，对于较长的跨度使用较深的腹板）。研究的具体目标包括：（1）通过数值方法研究拼装式PBTG桥梁在服务、疲劳设计载荷以及施工过程中的行为；（2）通过实验和数值方法研究拼装式PBTG桥梁在活载作用下的行为；（3）比较和对比三种拼装式PBTG桥梁的设计和分析方法；（4）对离散的腹板和底板尺寸进行全面研究，以开发一个“部件套件”，从而促进该方法的采用。为了全面评估拼装式PBTG的性能，在印第安纳州建造了两座示范桥梁：一座86英尺的单跨无斜桥和一座191英尺的两跨连续桥梁，其斜度为15度。对这些桥梁进行了数值和实验分析。数值结果表明，该方法是可行的，在服务载荷下显示出最小的应力，远低于钢的屈服强度。对已建桥梁的活载测试涉及使用BDI应变计测量应变。收集到的数据对于完善拼装式PBTG系统的数值建模方法至关重要。为了促进这一创新方法的采用，进行了一项广泛的研究，以确定现成的截面尺寸。这导致了标准化“部件套件”目录的制定，使系统适用于各种跨度和长度配置。本论文针对传统钢桥建设的局限性，特别是较长的预制制造时间和复杂的工厂图纸，提供了一种具有竞争力的替代方案，即预应力混凝土梁。