Investigation of Damage Detection in Bridge Piers using modal strain energy and modal flexibility methods: A Case Study

Abstract

Piers provide vertical support to the bridge deck and transfer loads to the foundation and ground. Ensuring their stability and structural integrity is critical to the overall safety of the bridge. The most common existing methods for damage detection, mainly used in bridge decks due to easier access and simpler modeling, are modal methods. The primary focus of this study is to explore the feasibility of utilizing these methods to detect damage in bridge piers, assuming that accurate mode shapes can be obtained. Therefore, one of the piers of Shahid Bakri Bridge in Tehran was selected as a case study. This pier was accurately modeled in Opensees. For sensitivity measurement, it was divided once into 10 parts and once into 100 parts, according to the number of sensor points. Also, 13 different scenarios with varying degrees of damage in concrete cover, rebar, and concrete core were investigated. In the two stages before and after the damage, mode shapes were extracted, and two methods, modal strain energy and modal flexibility, were used to detect the damage. The results demonstrated the good performance of both methods in detecting the presence of damage. Regarding locating the damage, the modal strain energy method was more successful. However, if there was damage in a small area of the cross-section, finding the exact location required additional sensor placements. These methods did not provide a suitable index to determine the extent of the damage.