بررسی پارامترهای تاثیرگذار بر عملکرد دیوارهای برشی کوتاه بتن آرمه با درنظر گرفتن اندرکنش خاک و سازه

دیوارهای برشی کوتاه با نسبت عرض به طول کمتر از 2 در تقویت سازه‌های کم ارتفاع بکار گرفته می‌شوند. این دیوارها معمولاً مقاومت جانبی قابل‌توجه لیکن شکل‌پذیری کم دارند. به دلیل استفاده از دهانه‌های به طول متعارف (در فاصله محور به محور ستون‌ها)، اغلب به‌تمامی ظرفیت برشی این دیوارها نیازی نمی‌باشد و می‌توان با بسیج بخشی از ظرفیت برشی، به مقاومت‌های کافی برای چنین سازه‌هایی دست‌یافت. در این مقاله نشان داده می‌شود که می توان با استفاده از شکل و طول مناسبی از فونداسیون و به‌حساب آوردن اثر انعطاف پذیری بستر ، شکل‌پذیری و مقاومت این دیوارها را افزایش داد. همچنین تاثیر پارامترهای خاک بر شکل‌پذیری مطالعه شده است. بدین منظور ابتدا یک نمونه دیوار برشی کوتاه که به‌صورت تجربی آزمایش‌شده و در ادبیات فنی گزارش‌شده است، با نرم‌افزار تحلیل غیرخطی atena 3d صحت‌سنجی شده و نتایج برای مطالعه حساسیت رفتار به پارامترهای طول، شکل فونداسیون و سختی خاک بکار گرفته می‌شود.

Evaluation of the effective parameters on the behavior of shallow RC shear walls considering soilstructure interaction

Short reinforced concrete shear walls with aspect ratio less than 2 are commonly utilizes in strengthening of low rise structures. These walls demonstrate adequate lateral load strength while they have low ductility comparing with high rise walls with same lengths. Considering typical span length of such a walls– between adjacent column distances there are no need to motivate all of lateral bearing strength of them and only taking to account a portion of strength will be sufficient for the purpose of strengthening of the structure. In this paper it will be shown that tacking into account the shape and length of foundation and interaction of the soilstructure the ductility of the wall is increased. Furthermore, effect of the soil stiffness on the behavior of the wall is studied. The short shear wall which has been studied experimentally by the NUPEC of Japan is adopted for numerical simulation by the commercial nonlinear analysis software ATENA 3D. The wall has been subjected to the predefined level of axial load and the increasing cycling lateral deformations. Sensitivity of the behavior of wall to mesh dimensions and the affecting parameters of concrete models such as fracture energy, tension softening and tension stiffening coefficient, shear modulus reduction after cracking, fixed or rotating crack modeling among the other affecting parameters are investigated to verify the model. Because of symmetry only one half of the wall is modeled. Reinforcing bars are modeled discretely taking into account the bondslip between concrete and bars. The results of verified model are used to study the sensitivity of a proposed short shear wall by IIESE for strengthening of low rise masonry buildings, to the parameters of length and shape of the footing together with and foundation soil property. It is shown that with increasing the length of footing, base reaction coefficient and the embedment depth of footing the bearing capacity of shear walls showing rocking behavior is increased but the ductility is decreased. For structures which need a limited level of strength increase or a demanded ductility, the length or embedment length of the footing may choose intentionally to motivate the rocking behavior of foundation. Short reinforced concrete shear walls with aspect ratio less than 2 are commonly utilizes in strengthening of low rise structures. These walls demonstrate adequate lateral load strength while they have low ductility comparing with high rise walls with same lengths. Considering typical span length of such a walls– between adjacent column distances there are no need to motivate all of lateral bearing strength of them and only taking to account a portion of strength will be sufficient for the purpose of strengthening of the structure. In this paper it will be shown that tacking into account the shape and length of foundation and interaction of the soilstructure the ductility of the wall is increased. Furthermore, effect of the soil stiffness on the behavior of the wall is studied. The short shear wall which has been studied experimentally by the NUPEC of Japan is adopted for numerical simulation by the commercial nonlinear analysis software ATENA 3D. The wall has been subjected to the predefined level of axial load and the increasing cycling lateral deformations. Sensitivity of the behavior of wall to mesh dimensions and the affecting parameters of concrete models such as fracture energy, tension softening and tension stiffening coefficient, shear modulus reduction after cracking, fixed or rotating crack modeling among the other affecting parameters are investigated to verify the model. Because of symmetry only one half of the wall is modeled. Reinforcing bars are modeled discretely taking into account the bondslip between concrete and bars. The results of verified model are used to study the sensitivity of a proposed short shear wall by IIESE for strengthening of low rise masonry buildings, to the parameters of length and shape of the footing together with and foundation soil property.