Reliability Analysis of a System of CFRP Structures on the Piled Raft Foundation Subjected to Earthquakes

Abstract

AbstractDesign work for a high-rising building often includes calculating the structure to suffer a specific intensity of earthquakes. The analysis concerning the soil-structure interaction is too complicated to cover all the risks and uncertainties, both in aleatoric and epistemic aspects. A wide range of data relates soil properties (static and dynamic response), input data of quakes (intensity and the lasting time), loading and dynamic effects (inertia forces, damping, and elastic forces), and the uncertainties in the method of analysis and modeling. Piled raft is such a typical problem in which soil-structure interaction (SSI) plays an important role, and reliability analysis for the structure viewing the superstructure and foundation as a system is quite a challenging problem. This article studies an approach for estimating the reliability index of the building viewing the frame, the piled raft, and soil foundation as a system. A 10-story building strengthened by CFRP with nonlinear characteristics is modeled in SAP2000 in which the cross-sections of beams with reinforcement and CFRP layers are modeled by ACI 440.2R (2017) recommendation for crack structure and modification for cracked beam retrofitting with CFRP. By studying the structure subjected to an earthquake intensity of Taiwan’s Chi-Chi earthquake, a set of data is created in which five groups of factors with lognormal distribution are collected. Multi-criteria performance functions are developed to analyze the reliability for a time-invariant reliability index. Results indicate that the wider model boundary results in the larger deformation for structure, both in vertical deflection and lateral displacement; besides, the time history load case yields the lower RI as compared to that of the RS load case, and the lateral displacement dominates the reliability. The very low RI of the combined structures indicates the hazardous condition for the system, with a very high probability of failure. The findings of this study could illustrate a simplified and efficient way to create a database for assessing the performance of the existing buildings reinforced by CFRP under an earthquake, and the SSI is concerned.KeywordsCFRP buildingUncertaintiesSeismic risk analysisLimit state functionsReliability index