دانلود رایگان مقاله انگلیسی اثر استرس های عمودی و فلنج ها در رفتار لرزه ای ساختمان های آجری مسلح نشده - الزویر 2018

ABSTRACT

Lateral in-plane response plays crucial role in seismic behavior of masonry structures. The aim of this article is to experimentally investigate the effects of vertical stresses and flanges (transverse walls) on the lateral in-plane response of the unreinforced brick masonry (URBM) walls. The experimental work included lateral in-plane quasi-static cyclic tests on full-scale walls (both with & without flanges). The vertical stresses resulting from typical single and two story unreinforced masonry buildings were simulated on full scale URBM walls. Flanges were introduced at both ends of the in-plane wall in single direction. In essence, the lateral in-plane stiffness & strength, deformability and energy dissipation of the two classes of walls are compared and the differences are quantified to help understand the effects of flanges on the in-plane response of masonry walls. The resulting damage mechanism and failure modes for each case are critically analyzed. The experimental results indicate that both vertical stresses and flanges incorporation significantly improved seismic response of URBM walls. In addition, the participation of flanges is critical in both vertical stress conditions.

4. Conclusions and recommendations

The objective of this study was to determine the effects of vertical stresses and flanges on the seismic behavior of URBM. Four full-scale perforated wall specimens were fabricated for studying the effects of above mentioned variables. Quasi-static testing was carried out on each test specimen and the data was analyzed to determine seismic behavior parameters that included force-deformation behavior, energy dissipation, stiffness and displacement ductility factors. A comparative study was then carried out to study the effects of vertical stresses and flanges on the strength and deformability characteristics of unreinforced masonry.

It is concluded that increase in vertical stresses in URBM results in dominating shear failure mode. Furthermore, increase in vertical stresses results in increasing the crack density thereby decreasing the crack width. For the same level of vertical stresses, provision of flanges in URBM tend to change the failure mode from rocking to shear. For low vertical stress case, the inclusion of flanges resulted in 18% increase in displacement ductility whereas ultimate displacement and peak resistance increased by 20% and 15%, respectively. A more prominent increasing trend is observed in case of high vertical stress conditions. For higher level of vertical stress, flanged specimen exhibited an increase of 15% in displacement ductility whereas ultimate displacement increased by 28%. Increase in vertical stress level improved the lateral resistance of flanged specimen by 11%. However, for high stress conditions, the increase in peak resistance capacity is lower than the former case. Stiffness degradation is observed to be affected by increasing the magnitude of vertical stresses and also by incorporation of flanges. Stiffness degradation rate is observed to be the same for both with and without flange specimens during earlier phase of loading. However, in case of high vertical stresses, stiffness degradation rate is decreased in higher loading cycles for flanged specimen.