@article {bnh-7481, title = {In-plane response of perforated unreinforced masonry walls under cyclic loading}, journal = {Journal of Structural Engineering}, volume = {146}, year = {2020}, month = {06/2020}, abstract = {

This paper presents the results of an experimental study into the behavior of perforated (containing openings) unreinforced masonry (URM) walls subjected to cyclic in-plane lateral loading. Damage to perforated URM walls during previous earthquakes has revealed that the in-plane response is mainly influenced by the pier and spandrel geometry, as well as the level of axial compressive stress on the walls due to gravity loading. The study focused on masonry typologies representative of historical URM buildings in the Australian context. To investigate this behavior, eight full-scale URM walls with semicircular arched openings, double wythe thickness, and materials representing masonry construction from the mid-19th to mid-20th century were constructed for pseudostatic cyclic in-plane testing. The experimental program considered varying spandrel depths and pier widths and the imposed vertical loading on the piers was also varied to observe the lateral load capacity and the variation of pier-spandrel failure modes. The test results showed that the in-plane capacity and the failure modes were significantly affected by changes of wall geometry and the imposed vertical precompression loading. Predictions of wall strengths, in-plane stiffnesses, and failure modes according to ASCE guidelines show that the guidelines agree well with the test observations.

}, keywords = {earthquake, lateral loading, unreinforced masonry}, doi = {https://doi.org/10.1061/(ASCE)ST.1943-541X.0002657}, url = {https://ascelibrary.org/doi/full/10.1061/\%28ASCE\%29ST.1943-541X.0002657}, author = {Milon Howlader and Mark Masia and Michael Griffith} } @article {bnh-7482, title = {In-plane shear testing of unreinforced masonry walls and comparison with FEA and NZSEE predictions}, volume = {5}, year = {2020}, month = {01/2020}, abstract = {

The present study was conducted to investigate the global and local in-plane response of perforated URM walls under earthquake loading, based on observations of damage from previous earthquakes. To do so, full-scale cyclic in-plane testing of URM walls with an arched opening which were designed to represent walls in heritage URM structures in Australia was performed. The study investigated the behaviour of both pier and spandrel elements within the walls. Emphasis was also given to the position of walls within a multi-storey building by varying the pre-compression loads (representing gravity loads) on the walls. The tested walls were then simulated using nonlinear finite element analyses (FEA) where simplified micro-modelling (crack-shear-crush) approaches were used to analyse the wall behaviour. Finally, the shear capacities and the failure modes of the walls obtained from the experimental tests and FE analyses were compared to the proposed New Zealand Society for Earthquake Engineering (NZSEE) predictions.

}, keywords = {cyclic testing, FEA, finite element analyses, in-plane shear behaviour, NZSEE, unreinforced masonry, URM}, doi = {https://doi.org/10.1504/IJMRI.2020.104845}, url = {https://www.inderscienceonline.com/doi/abs/10.1504/IJMRI.2020.104845}, author = {Milon Howlader and Mark Masia and Michael Griffith} } @article {bnh-6808, title = {Simplified calculation of roof accelerations in existing low-rise symmetric unreinforced masonry buildings with flexible diaphragms}, journal = {Bulletin of Earthquake Engineering}, year = {2020}, month = {03/2020}, abstract = {

A formulation is presented for simplified evaluation of the roof acceleration response for the purpose of assessing non-structural components in unreinforced masonry buildings with flexible diaphragms excluding torsional effects. The method is based on modal calculations that are further studied through nonlinear time-history analysis (NLTHA) of four case study buildings. The NLTHA results for a relatively small level of ground shaking was used to validate the overall ability of the simplified modal method to predict the diaphragm flexibility effects. The NLTHA results were also used to discuss the effects of the building inelastic response in the conservatism of the simplified modal technique. It was found that, in lieu of a comprehensive modal analysis, it is possible to calculate roof accelerations in symmetric low-rise buildings with flexible diaphragms using a simplified two-mode modal method. Based on this study, a predictive method is proposed for conservative estimation of peak roof accelerations in these buildings.

}, keywords = {acceleration response, flexible diagrams, height amplification factor, unreinforced masonry}, doi = {https://doi.org/10.1007/s10518-020-00823-1}, url = {https://link.springer.com/article/10.1007/s10518-020-00823-1$\#$citeas}, author = {Hossein Derakhshan and Yasuto Nakamura and Michael Griffith and Manicka Dhanasekar} } @article {bnh-6698, title = {Suitability of Height Amplification Factors for Seismic Assessment of Existing Unreinforced Masonry Components}, journal = {Journal of Earthquake Engineering}, year = {2020}, month = {01/2020}, pages = {1-20}, abstract = {

The suitability of {\textquoteleft}design{\textquoteright} height amplification factors (HAF) for the purpose of seismic assessment of existing non-structural unreinforced masonry (URM) components with known strength was evaluated through a numerical study. Four building typologies were included that represented pre-1940 URM construction in Australia and New Zealand. Through pushover and incremental dynamic analyses, the effects of diaphragm flexibility and nonlinear building response on floor accelerations were studied. It was found that Australia/New Zealand code procedures include significant inelastic building behaviour that reduces HAF. An interpretation was made on the applicability of the assumptions in the context of assessing non-structural URM components.

}, keywords = {flexible diaphragms, height amplification factor, non-structural components, seismic input, unreinforced masonry}, doi = {https://doi.org/10.1080/13632469.2020.1716889}, url = {tandfonline.com/doi/full/10.1080/13632469.2020.1716889}, author = {Hossein Derakhshan and Yasuto Nakamura and Michael Griffith and Jason Ingham} } @conference {bnh-6386, title = {Out-of-plane fragility of URM parts and components based on time-history analysis-comparison to simplified force-based approaches}, booktitle = {Australian Earthquake Engineering Society 2019 Conference}, year = {2019}, month = {12/2019}, address = {Newcastle}, abstract = {

This paper presents a technique for constructing analytical fragility curves for generic URM components such as parapets and fa{\c c}ade walls subjected to out-of-plane actions. The technique implements a nonlinear time-history-analysis (THA) that computes the wall{\textquoteright}s displacement history under generic shaking input. The model defines the wall{\textquoteright}s capacity by a force-displacement model that neglects tensile bond strength and assumes that all resistance comes from rocking stability and, where applicable, friction. Synthetic accelerograms compatible with the AS 1170.4-2007 soil class D spectrum were used as the ground motion, and the acceleration input applied at the component level was computed by a precursor THA of the building to account for its motion-filtering influence and height amplification. Fragility curves were generated for several different wall configurations including parapets, one-way and two-way spanning walls. The generated curves are used to examine three alternate force-based approaches permitted by AS 1170.4. It is shown that the code techniques are unreliable in estimating the ground motion intensity to cause collapse, and that they are in some instances overly conservative (uneconomical) while being unconservative in others.

}, keywords = {force-based assessment, fragility curves, out-of-plane, time-history-analysis, unreinforced masonry}, url = {https://aees.org.au/wp-content/uploads/2019/12/62-Jaroslav-Vaculik.pdf}, author = {Jaroslav Vaculik and Michael Griffith} } @article {bnh-6336, title = {Seismic fragility assessment of nonstructural components in unreinforced clay brick masonry buildings}, journal = {Earthquake Engineering and Structural Dynamics}, year = {2019}, month = {12/2019}, abstract = {

The results of an investigation of the probability of earthquake damage to nonstructural unreinforced masonry (URM) components are presented. The components include parapets, chimneys, and out-of-plane loaded facades typical of low-rise pre-1940 construction in Australia and New Zealand. The study is based on a street survey of component geometry, in situ data on material strength, and simplified mechanical models. Uncertainties in capacity and demand were quantified based on, respectively, stochastic and deterministic approaches. The damage probabilities were compared with relevant guidelines and empirical damage data from three earthquakes. The study established a link between the qualitative damage states reported in existing guidelines and the quantitative URM component damage states. While some median damage state thresholds correlated well with the data from the guidelines, a larger dispersion value was found in the current study due to the large variations in component properties. Comparisons with empirical data suggest that the developed fragility data provide a realistic estimate of nonstructural component damage that occurred in similar buildings, with a reasonable level of conservatism. The outcome is useful in rapid assessment of the seismic risks due to nonstructural component collapse in URM precincts.

}, keywords = {Damage, earthquake, seismic risk, unreinforced masonry}, doi = { https://doi.org/10.1002/eqe.3238}, url = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/eqe.3238}, author = {Hossein Derakhshan and Kevin Walsh and Jason Ingham and Michael Griffith and David Thambiratnam} }