Investigation of superload effects on steel and prestressed concrete slab -on -girder bridges
Abstract
A permit truck which exceeds the predefined limit of 108 kips is defined as a superload in Indiana. These trucks can cause adverse long term effects on the performance of a bridge in addition to the possibility of causing immediate damage. Bridges with steel and prestressed concrete (PC) girders, selected from an extensive database, were analyzed and instrumented. Detailed finite element models were developed using the structural analysis programs SAP2000 and ANSYS. Furthermore, a prestressed concrete bridge and a steel bridge were instrumented using more than 50 sensors each. Strains and deflections were measured during a live load test, and each bridge was monitored for more than six months. Capacities of the investigated bridges were calculated and compared with the demands generated by the superload trucks. A simple and accurate structural analysis technique, called the spring analogy method, was developed to provide an effective evaluation tool to fill the gap between beam line analysis and complicated three-dimensional finite element analysis (FEA). Analysis of the steel and PC bridges showed that typical superload trucks up to a gross vehicle weight of 500 kips are not expected to cause any damage or impair long term performance of the investigated bridges. Serviceability limit states of the PC bridges controlled the rating, and the bridges had adequate strength to accommodate all superloads included in the database. However, strength limit states controlled the rating of steel bridges. Long term monitoring of a continuous and a simple span bridge indicated that strains comparable to those of a 366-kip superload truck can be generated by regular truck traffic. The field measurements also showed that the in-service behavior was different than the design assumptions. Fixity due to integral abutments, effectiveness of the continuity joint in the continuous PC bridge and contribution of the secondary members lead to a significant difference between the expected and the anticipated behavior. Furthermore, the AASHTO (2004) girder distribution factor equation was found to be conservative for the investigated bridges. Use of a more accurate method such as FEA or the spring analogy method is recommended for the evaluation of bridges traversed by superloads.
Degree
Ph.D.
Advisors
Liu, Purdue University.
Subject Area
Civil engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.