Estimation of the Moment Capacity during Bridge Service Life for Structural Health Monitoring System

Abstract The load rating factor is a measurement used to describe the load carrying capacity of a bridge, issue permits to heavy trucks, and determine load postings on bridges. The Bridge Engineering Center (BEC) at Iowa State University (ISU) has developed a method to improve a nondestructive load rating method using continuous structural health monitoring (SHM) data coming from an actual bridge site that does not require traffic disruptions. In the current load rating factor calculation approach, the nominal moment capacity (Mn) is usually calculated utilizing the nominal section dimensions and material properties of the bridge and might not represent the actual capacity of the bridge or its elements. In this work, the rating factor calculation process is further improved by estimating an improved flexural strength for concrete slab on steel girder composite sections. To achieve the objective, a hypothesis to estimate the moment capacity is proposed. To validate the hypothesis, an experimental program was conducted on four steel–concrete composite sections to obtain the moment of inertia of each section and the flexural strength. The experimental results show that the moment of inertia and the flexural strength of a steel–concrete composite section calculated based on nominal material properties are significantly different from the actual moment of inertia and the flexural strength of the section. In the absence of actual material properties, a Monte Carlo simulation along with Iexp from the calibrated load rating model may significantly improve the rating factor of a bridge. Practical Applications This work further improves the rating factor calculation process by estimating an improved flexural strength for concrete slab on steel girder composite sections. This method improves a nondestructive load rating method using continuous structural health monitoring (SHM) data coming from an actual bridge site that does not require traffic disruptions. It overcomes existing approaches where reference is made to the design configuration of the bridge, e.g., the cross section, but not to the current or actual state of the bridge.