Safety assessment of structures for near-field blast-induced ground excitations using operational modal analysis

The safety assessment of structures subjected to near-field blast-induced ground excitations has been performed by using Operational Modal Analysis. A reinforced concrete building, a masonry building, a reinforced concrete highway bridge, and a masonry arch bridge have selected for the safety evaluation. The study consists of five phases: measurement of vibration characteristics of blasting, analytical modal analysis of inspected structures, determining experimental dynamic characteristics using Operational Modal Analyses, finite element model updating, and nonlinear dynamic analysis. The vibration characteristics and ground excitations of blasting have been measured around the inspected building on hard soil using geophone set. The initial analytical model of the structures has been constituted according to the project data and in-situ investigations on structures. Analytical frequencies and mode shapes have been attained using ANSYS finite element program. Operational Modal Analysis Method has been used to determine the dynamic characteristics experimentally and blast vibrations are taken into account as environmental vibrations. The dynamic characteristics have been extracted from the collected signals using Enhanced Frequency Domain Decomposition (EFDD) technique. The analytical and experimental results have been compared with each other and finite element models of the structures have been updated using some uncertain parameters (such as material properties and boundary conditions) to reduce the differences. Nonlinear dynamic analyses of structures under near-field blast-induced ground excitations have been carried out using the updated finite element models. The Drucker-Prager criterion has been considered in the nonlinear analyses. It can be said that the Operational Modal Analyses method can be safely used to determine experimental dynamic characteristics of structures under near-field blast-induced ground excitations. Also, it is recommended that finite element model updating procedure must be considered for the damage assessment of the engineering structures. (C) 2012 Elsevier Ltd. All rights reserved.