Comparison of historical in-service monitoring data for improved maintenance and management of bridges

Harry W. Shenton IIIThe In-Service Bridge Monitoring System (ISBMS) was deployed on fourteen bridges in Delaware, including eleven that had been previously monitored several years ago. Live load strains were recorded for approximately fourteen days on each bridge; the data from different monitoring periods for the same bridge were then compared. In order to determine whether a bridge had undergone significant structural changes or traffic pattern changes between the different monitoring periods, quantifiable measures of variation were developed. Depending on the magnitude of these parameters, a bridge’s response was determined to have sustained a change or have remained the same. When the parameters suggested a change in the response of a bridge, the analysis was compared to a subjective evaluation and it could be corroborated or dismissed. In cases where variations seemed likely, possible causes were investigated. After such analyses, the effectiveness of each parameter was reviewed and the preferred method of Square Root Sum of the Squares of Differences was recommended for future comparisons. Strain data was then used to project future strains and designate appropriate in-service bridge rating factors. The conservative nature of conventional rating methods was evidenced during comparison. It is hoped that the ISBMS can one day be implemented with the bridge inspection process and add objective, data-based insight into the evaluation of structural capacity.University of Delaware, Department of Civil and Environmental EngineeringM.C.E