Please use this identifier to cite or link to this item: http://archive.nnl.gov.np:8080/handle/123456789/396
Title: Performanxe evaluation of cold-formed steel stud shear walls in seismic conditions
Authors: Shahi, Rojit
Keywords: Cold-formed steel-framed houses -- Australia
Issue Date: 23-Nov-2017
Abstract: This project is a part of a sustained research effort to make houses more affordable and safer. This project seeks to modernize the current prescriptive lateral bracing design of houses to a performance-based design. The aim of this project is to develop a rational holistic model for bracing of cold-formed steel-framed houses. It focuses on the development of the rational testing method and the evaluation procedur e for determining the bracing capacity of cold-formed steel-framed wall panels taking into account displacement controlled behaviour for a diverse range of seismic conditions. Lateral load resisting elements in support of buildings made of cold-formed steel has been of major concern in seismic conditions given the apparent non-ductile behaviour of this type of material. It has been revealed in the research that this form of construction can possess significant strength and ductility reserves. Most bracing elements tend to be made up of a large number of components including structural frames, bracing elements and sheetings. Thus, modelling their potential response behaviour is not straightforward, and there are no standard test methods for determining their capacity in seismic conditions. The various test procedures used by an Australian manufacturer are mainly based on TR440 (Experimental Building Station, 1978) which considers principally the conditions of cyclonic wind. There are no provisions for deter mining bracing capacity of these walls for seismic performance in Australia. A comprehensive testing methodology has been developed in this research which is aimed at providing a practical and reliable means of evaluating the seismic resistant capacity of this increasingly common form of construction for the domestic housing market. Whilst numerous loading protocols exist for the pseudo-static cyclic testing of structures, the loading protocol developed in this research was derived from analyses of accelerograms that had been simulated specifically for design earthquake scenarios appropriate for regions of low-moderate seismicity, like Australia. Analyses undertaken were based mainly on magnitude-distance combinations and site conditions that would impose onerous drift demand on low-rise buildings. Experimental studies have been conducted on full scale isolated wall panels measuring 2.4 m x 2.4 m and 0.9 m x 2.4 m braced with fibre cement boards. A cyclic loading protocol that had been developed based on seismic conditions of Australia was used in the cyclic testing to ensure the validity and practicability of the testing. Important wall parameters such as elastic stiffness, yield displacement, ultimate displacement and structural ductility factor were evaluated from the test results using various existing methods together with the method proposed by the author of the thesis. Detailed analytical investigations of tested wall panels have been carried out by formulating three different analytical models namely; numerical model, hand calculation method and simplified hand calculation method, , for predicting the load-deflection behaviour of wall panels sheathed with fibre cement board. These models were used to conduct extensive sensitivity analyses for investigating the influence of screw spacings, wall lengths and aspect ratios on lateral performance of wall panels. Analytical results showed that the aspect ratios of the sheathing board can greatly influence the displacement capacity of the wall panel against racking actions, whereas the load carrying capacity per unit length of the wall panel is largely influenced by the spacing of perimeter sheathing-to- framing screws. Rational methods have been proposed for determining the bracing capacity of wall panels against wind and earthquake loadings. A conventional force-based (FB) approach and a more rational direct displacement-based design (DDBD) approach has been implemented for evaluating the bracing capacity of wall panels, particularly for earthquake loading. Moreover, non-linear time histor y analyses (NLTHA) have been conducted for a suite of artificial and recorded accelerograms consistent with the design level earthquake to check the accuracy of the estimated values from the adopted rational approaches. It was found that the estimated results from the DDBD approach best corr elated with the NLTHA results. The effectiveness of DDBD has been checked against the performance sensitivity of the structure to changes in elastic stiffness, ultimate strength and ductility, and was found to provide satisfactory agreement with the NLTHA results.
Description: a thesis submitted in total fulfillment of the requirements of the Degree of Philosophy, Department of Infrastructure Engineering, University of Melbourne, 2015.
URI: http://103.69.125.248:8080/xmlui/handle/123456789/396
Appears in Collections:600 Technology (Applied sciences)

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