ارزﯾﺎﺑﯽ اﺛﺮات ﺑﺮش ﺗﯿﺮﻫﺎ و ﺳﺘﻮنﻫﺎ ﺑﺮ ﻋﻤﻠﮑﺮد ﻟﺮزهاي ﺳﺎزهﻫﺎي ﺑﺘﻦ ﻣﺴﻠﺢ

Assessment of shear effects of RC beams and columns on seismic performance of RC structures

ﻧﻘﺶ ﺷﮑﺴﺖ ﺑﺮﺷﯽ در رﻓﺘﺎر ﻟﺮزهاي ﺳﺎزهﻫﺎي ﺑﺘﻦ ﻣﺴﻠﺢ از اﻫﻤﯿﺖ ﻓﺮاواﻧﯽ ﺑﺮﺧﻮردار ﻣﯽﺑﺎﺷﺪ. ﻣﻌﻤﻮﻻ، ﺗﺤﻠﯿﻞ ﻏﯿﺮﺧﻄﯽ ﺗﯿﺮﻫﺎ و ﺳﺘﻮنﻫﺎ در ﺳﺎزهﻫﺎي ﺑﺘﻨﯽ ﺑﺮ اﺳﺎس رﻓﺘﺎر ﺧﻤﺸﯽ اﻋﻀﺎ ﺑﻮده و اﺛﺮات ﺑﺮش در آﻧﻬﺎ ﻧﺎدﯾﺪه ﮔﺮﻓﺘﻪ ﻣﯽﺷﻮد. در ﭼﻨﯿﻦ ﺗﺤﻠﯿﻞﻫﺎﯾﯽ ﺗﻨﻬﺎ رﻓﺘﺎر ﺧﻤﺸﯽ ﻋﻀﻮ در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﺪه اﺳﺖ؛ درﺣﺎﻟﯿﮑﻪ ﻧﺘﺎﯾﺞ آزﻣﺎﯾﺸﮕﺎﻫﯽ اﺣﺘﻤﺎل ﺷﮑﺴﺖ اﻋﻀﺎي ﺑﺘﻦ ﻣﺴﻠﺢ در ﺣﺎﻟﺖﻫﺎي ﻗﺒﻞ از رﺳﯿﺪن ﺑﻪ ﻇﺮﻓﯿﺖ ﺧﻤﺸﯽ ﻧﻬﺎﯾﯽ را ﻧﺸﺎن ﻣﯽدﻫﺪ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ، ﻣﺪﻟﯽ ﻋﺪدي ﺷﺎﻣﻞ ﻣﻔﺎﺻﻞ ﭼﺮﺧﺸﯽ، ﺑﺮاي ﺷﺒﯿﻪﺳﺎزي اﺛﺮات ﻇﺮﻓﯿﺖ ﺑﺮﺷﯽ ﺗﯿﺮﻫﺎ و ﺳﺘﻮنﻫﺎ ﺑﺮ اﺳﺎس ﻣﮑﺎﻧﯿﺰم ﺷﮑﺴﺖ ﻣﻮاد ﭘﯿﺸﻨﻬﺎد ﺷﺪه اﺳﺖ. ﺑﻪ ﻣﻨﻈﻮر ﺑﺮرﺳﯽ دﻗﺖ ﻣﺪل ﭘﯿﺸﻨﻬﺎدي در ﺗﯿﺮﻫﺎ و ﺳﺘﻮنﻫﺎ، ﻧﺘﺎﯾﺞ ﺑﻪ دﺳﺖ آﻣﺪه از ﺗﺤﻠﯿﻞ ﻏﯿﺮﺧﻄﯽ ﺑﺎ ﻧﺘﺎﯾﺞ آزﻣﺎﯾﺸﮕﺎﻫﯽ ﻣﻘﺎﯾﺴﻪ ﺷﺪ؛ ﺑﻪ ﻃﻮرﯾﮑﻪ ﻧﺘﺎﯾﺞ ﭘﯿﺶﺑﯿﻨﯽ ﺷﺪه ﺗﻮﺳﻂ ﻣﺪل ﭘﯿﺸﻨﻬﺎدي ﺗﻄﺎﺑﻖ ﻣﻨﺎﺳﺒﯽ ﺑﺎ ﻧﺘﺎﯾﺞ آزﻣﺎﯾﺸﮕﺎﻫﯽ دارد. ﻋﻼوه ﺑﺮ اﯾﻦ، ﻣﺪل ﭘﯿﺸﻨﻬﺎدي در ﺳﻄﺢ ﺳﺎزه ﻣﻮرد ارزﯾﺎﺑﯽ ﻋﻤﻠﮑﺮدي ﻗﺮار ﮔﺮﻓﺖ و ﺑﻪ ﻫﻤﯿﻦ ﻣﻨﻈﻮر، ﻗﺎﺑﯽ ﺑﺘﻦ ﻣﺴﻠﺢ در دو ﺣﺎﻟﺖ ﻣﺨﺘﻠﻒ 1- ﺗﺤﻠﯿﻞ ﺑﺎ اﺳﺘﻔﺎده از ﻣﺪل ﭘﯿﺸﻨﻬﺎدي ﺑﺎ در ﻧﻈﺮ ﮔﺮﻓﺘﻦ اﺛﺮات ﺑﺮش و 2- ﺗﺤﻠﯿﻞ ﺑﺮ اﺳﺎس ﻣﺪل ﭘﯿﺸﻨﻬﺎدي ﺑﺎ ﺻﺮف ﻧﻈﺮ ﮐﺮدن از اﺛﺮات ﺑﺮش در اﻋﻀﺎ ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ، اﻫﻤﯿﺖ در ﻧﻈﺮ ﮔﺮﻓﺘﻦ اﺛﺮ ﺑﺮش در ﭘﯿﺶﺑﯿﻨﯽ رﻓﺘﺎر ﻏﯿﺮﺧﻄﯽ ﻗﺎبﻫﺎ ﺗﻮﺳﻂ ﻣﺪل ﭘﯿﺸﻨﻬﺎدي را ﻧﺸﺎن ﻣﯽدﻫﺪ؛ ﮐﻪ ﻣﯽﺗﻮاﻧﺪ روﺷﯽ ﺟﺎﯾﮕﺰﯾﻦ ﺑﺮاي روشﻫﺎي ﻣﺘﺪاول ﺑﺎﺷﺪ.

Shear failure plays a significant role in the seismic behavior of reinforced concrete (RC) structures. Generally, nonlinear analysis of the beams and columns in concrete structures is based on the flexural behavior of the members, and shear effects are generally ignored. Although in such an analysis, only the flexural behavior of members is considered, experimental results reveal the likelihood of the failure of RC members before reaching the ultimate flexural capacity. In this paper, a numerical model including rotational springs was developed to simulate the effects of the shear capacity of beams and columns based on material failure mechanisms. In order to evaluate the accuracy of the proposed model for beams and columns, the results gained by the nonlinear analysis were compared with the experimental results, which revealed a good agreement of the results predicted by the proposed model with those of experiments. Furthermore, the proposed model was assessed at the structural level in terms of performance, and to do so, an RC frame was investigated in two different modes: a) analysis using the proposed model considering shear effects and b) analysis based on the proposed model ignoring shear effects in the members. The obtained results suggest the importance of taking the effect of shear into account in predicting the nonlinear behavior of frames by the proposed model which may present an alternative to common methods.