Civil and Environmental Engineering


First Advisor

Dr. Richard L. Wood

Second Advisor

Dr. Christine E. Wittich

Third Advisor

Dr. Cody Stolle

Date of this Version

Fall 12-6-2019


Watson, D. (2019). Lidar assessment to monitor bridge response under live and dead loads.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Civil Engineering, Under the Supervision of Professor Richard L. Wood. Lincoln, Nebraska: December 6, 2019

Copyright 2019 Daniel Watson


Understanding how a bridge structure responds to various loads in a time and resource-efficient approach is vital in characterizing bridge health. Bridge health monitoring is an evaluation of the structural condition and performance, which optimizes limited transportation budgets by prioritizing the bridges that are in the most need for retrofit or replacement. Identifying and remedying issues will mitigate long-term problems and ensure that the bridge remains open to service for all legal loads. In contrast, health monitoring and load rating will determine if a bridge can only carry traffic up to a certain weight or speed, requiring a bridge load restriction. Bridge response monitored in the field can calibrate a finite element method model to produce more reliable load ratings and distribution factors for bridges. Conventional methods utilizing discrete sensors can be time-consuming and provide a limited view of the bridge response that varies throughout the structure. Full-field data provided by lidar proves to be a viable tool to display the entire bridge response using less time and resources than conventional methods. This thesis evaluates the use of lidar to characterize bridge deflection response under changing live and dead loads. Two bridge structures were monitored while a loaded triaxial truck was placed on the deck and the other two were monitored during a phased construction concrete deck pour. The four assessed bridges represent a wide variety of bridges, where in each case lidar was able to provide high-fidelity and full-field deflection shapes. For one of these bridge structures, an inverted tee girder bridge of 19.81-meter length, a numerical model was constructed using the known parameters. Using traditional finite element modeling techniques, the numerical model fell short of the physical bridge response under live loads. The numerical model demonstrated the lack of uniform displacement, which was highlighted and characterized in the lidar point clouds. The use of lidar for this bridge structure demonstrates the benefit of the full-field response as well as the simplicity in the load test procedure.

Advisor: Richard L. Wood