FBG Sensor Analysis of a Beam with Complex Geometry and Boundary Conditions

Abstract

This thesis presents an investigation into the structural behavior of a concrete beam with welded connections in an operational parking garage. Long-gauge fiber Bragg grating (FBG) sensors were installed at strategic locations to measure strain under various loading configurations. The research explores the discrepancies between numerical calculations and measured beam response to understand how the complex geometry and boundary conditions influence structural behavior. Finite element analysis (FEA) simulations were conducted using Abaqus software to establish boundary conditions representing two extreme cases: a simply supported beam and a beam with constrained points. These models served as limit states for interpreting the influence of welded connections on beam strain. Measured strain data was compared with FEA predictions, and the effect of welded connections was quantified using a percent effectiveness metric. Results demonstrate that welded connections exert diverse influences on beam deflection depending on both measurement location and load configuration. The connections' behavior generally falls between that of a simply supported beam and one with fixed constraint points, with the proximity to either extreme end condition varying throughout the beam. FEA models showed particular difficulty in accurately predicting lateral bending behavior. The study was constrained by limitations in sensor placement, load magnitude restrictions, and simplifications in the FEA models. Despite these constraints, the methodology demonstrates an effective approach for analyzing structures with complex geometries and boundary conditions. This research contributes to understanding CarbonCure concrete performance in operational structures and supports the ongoing development of structural health monitoring techniques that can enhance the safety and maintenance of built infrastructure.