Damage Detection in Steel Lattice Panels

Abstract

In the field of Structural Engineering, the worsening problem of aging and defficient infras- tructure in our country and across the world has demonstrated the need for an improved system to monitor and maintain the structures. The field of Structural Health Monitor- ing(SHM) has been growing rapidly in recent past in order to address such problems. The goal of the field of SHM is to continually examine the condition of a structure to detect and mitigate the damage that may occur. The basic concept behind the SHM is that by continually tracking the strength and integrity of the structure, the damage can be de- tected, the life span can be assessed, and extended by proper maintenance and mitigation. Damage detection of structure may contains different procedure i.e. Assessment, Exis- tence, Location, type and quantification of damage. In the present study, damage assess- ment of Steel structure at component level and at sub structure level is carried out by using vibrational based damage assessment method. The beams of different boundary conditions and cross sections are considered. By inducing free vibration on two different state of beams i.e. undamaged and damaged beam, natural frequency response of the beams are determined using experimental acceleration response results. The damage is predicted in terms of percentage change in frequency of damaged beam vis-a-vis undam- aged beams. Experimental results obtained for beam of three different cross section when compared with numerical results, both are found in good agreement to each other. At sub-structure level, Steel Lattice Panel is fabricated and free vibration responses are measured on undamaged panel using Push Pull mechanism. An element level damage is introduce, i.e., members forming steel lattice panel is treated as an element and ele- ment/elements are physically removed from the panel in a particular pattern representing critical cases and element removal of the panel. The damage in a panel is identified by comparing the damaged natural frequency with the undamaged natural frequency for the panel. Experimental and numerical results obtained reveals that effect of removal of member carrying tensile force from the steel lattice panel is more critical as compared to members carrying compressive force. The present study also includes the application of the wavelet transform to detect the location of damage in structure. It has been observed that the wavelet analysis can detect the localization of the damage by using a response from static or dynamic loads. The simulation results shows that, if a suitable wavelet type is selected, the wavelet analysis is capable of extracting micro damage information from the response signal in a simple, robust and reliable way.