Towards the Development of Efficient and Economical Short Span Modular Bridges
The Federal Highway Administration’s National Bridge Index consists of over 600,000 bridges. Of these bridges, over 25% are considered either structurally deficient or functionally obsolete. While several state bridge departments have standard designs for bridge components in order to speed up the design process in replacing these bridges, few have standard designs for the bridge superstructure.
This work investigates current practices and trends in the design of short span bridges through the use of a survey. The survey was presented to the bridge department of every state in the country and responses were collected from 86% of these states. Based on the responses to these surveys, two courses were pursued in this work: the research and grading of both existing and developing modular bridge technologies that have application in short span steel bridges and the development of standard short span steel bridge superstructures using conventional design approaches.
In collaboration with the American Iron and Steel Institute’s Short Span Steel Bridge Alliance and other professionals in the bridge industry, a collection of modular bridge systems and elements were compiled and researched. Based on the Federal Highway Administration’s Highways for LIFE initiative, which promotes the development of Long-lasting highway infrastructure using Innovations to accomplish Fast construction of Efficient and safe highways and bridges, a grading system was developed for professionals in the industry to grade the major modular bridge systems researched. Based on the grading of these systems, a system will be further developed into a set of standardized short span bridge designs.
Second, standard short span steel bridge designs were developed to create a design aid for bridge engineers. In these designs, bridges with spans ranging from 40 feet to 140 feet in 5 foot increments were developed for rolled steel sections, homogeneous steel plate girder sections and hybrid steel plate girder sections. The rolled sections were designed using two design approaches: the lightest weight possible and the lightest weight possible with a limited section depth. Based on these designs, a suite of rolled sections were selected to be efficient sections of larger span ranges. This limited suite provides the opportunity for stock piling common rolled steel girder sections. Without needing to order the fabrication of the rolled girder sections, a more efficient transition from design to construction can be achieved. The plate girder sections were designed with a limited depth and utilizing a set of limited plate sizes to allow for the stock piling of common steel plate sizes. These designs will also act as a framework for future design plans using a modular bridge system.