اثر نشست تفاضلي فزاينده در زير ستونها بر رفتار يك قاب بتني با لحاظ نمودن شرايط تكيهگاهي متفاوت

Influence of Increasing Differential Settlement under Columns on a RC Frame Response Considering Different Support Conditions

ﻣﺨﺎﻃﺮات ﻃﺒﯿﻌﯽ و ﻓﻌﺎﻟﯿﺖﻫﺎي اﻧﺴﺎﻧﯽ زﻣﯿﻨﻪﺳﺎز وﻗﻮع ﻧﺸﺴﺖ ﮐﻠﯽ ﯾﺎ ﻣﻮﺿﻌﯽ زﻣﯿﻦ ﻫﺴﺘﻨﺪ. ﭘﯿﺶﺑﯿﻨﯽ اﺛﺮات ﻧﺸﺴﺖ ﻧﺎﻣﺘﻘﺎرن ﺑﺰرگ ﺑﺮ رﻓﺘﺎر ﻗﺎبﻫﺎي ﺳﺎزهاي ﺧﺼﻮﺻﺎ در ﻧﻮاﺣﯽ ﺷﻬﺮي ﺑﺎ ﺗﺮاﮐﻢ ﺟﻤﻌﯿﺘﯽ ﺑﺎﻻ، ﯾﮏ ﻣﺴﺌﻠﻪ ﻣﻬﻢ در ﻓﺮآﯾﻨﺪ ﻃﺮاﺣﯽ اﺳﺖ ﭼﺮا ﮐﻪ در ﺻﻮرت ﻋﺪم ﺗﻮﺟﻪ ﮐﺎﻓﯽ ﻣﯽﺗﻮاﻧﺪ ﻣﻨﺠﺮ ﺑﻪ ﺗﻠﻔﺎت ﺟﺎﻧﯽ و ﻣﺎﻟﯽ ﺟﺒﺮان ﻧﺎﭘﺬﯾﺮي ﺷﻮد. در اﯾﻦ ﻣﻘﺎﻟﻪ ﺑﻪ ﻣﻨﻈﻮر ﯾﺎﻓﺘﻦ درك ﺑﻬﺘﺮ از ﻧﺤﻮه ﺗﺎﺛﯿﺮ ﭘﺪﯾﺪه ﻣﺬﮐﻮر ﺑﺮ رﻓﺘﺎر روﺑﻨﺎي ﺳﺎزه، ﺑﺮ روي ﯾﮏ ﻗﺎب ﺧﻤﺸﯽ ﺑﺘﻨﯽ ﺳﻪ ﺑﻌﺪي داراي ﻃﺮح ﺳﺎزهاي ﻣﻄﺎﺑﻖ ﺑﺎ آﯾﯿﻦﻧﺎﻣﻪﻫﺎي اﯾﺮان در ﺷﺶ ﺣﺎﻟﺖ ﻣﺠﺰا، ﮐﻪ از در ﻧﻈﺮ ﮔﺮﻓﺘﻦ ﺳﻪ ﻣﻮﻗﻌﯿﺖ ﺑﺮاي ﻣﺤﻞ اﻋﻤﺎل ﻧﺸﺴﺖﻫﺎي ﺗﻔﺎﺿﻠﯽ ﻓﺰاﯾﻨﺪه )زﯾﺮ ﯾﮏ ﺳﺘﻮن ﻣﯿﺎﻧﯽ، ﮐﻨﺎري و ﯾﺎ ﮔﻮﺷﻪ( ﻫﻤﺮاه ﺑﺎ دو وﺿﻌﯿﺖ ﺗﮑﯿﻪﮔﺎﻫﯽ ﻣﺘﻔﺎوت )ﺻﻠﺐ و ﻏﯿﺮﺻﻠﺐ( ﺑﺮاي ﭘﺎي ﺳﺘﻮنﻫﺎ ﺣﺎﺻﻞ ﻣﯽﮔﺮدﻧﺪ، ﻣﺠﻤﻮﻋﻪاي از ﺗﺤﻠﯿﻞﻫﺎي اﺳﺘﺎﺗﯿﮑﯽ ﻏﯿﺮﺧﻄﯽ اﻧﺠﺎم ﺷﺪه و ﻣﻮاردي از ﻗﺒﯿﻞ ﺗﻐﯿﯿﺮات در اﻟﮕﻮي ﻟﻨﮕﺮ ﺧﻤﺸﯽ ﺗﯿﺮﻫﺎي ﭘﻞ زﻧﻨﺪه، ﺑﺎزﺗﻮزﯾﻊ ﻧﯿﺮوي ﻣﺤﻮري در ﺳﺘﻮنﻫﺎ و ﻫﻤﭽﻨﯿﻦ ﺣﺪاﮐﺜﺮ ﻧﺸﺴﺖ ارﺗﺠﺎﻋﯽ و ﻏﯿﺮارﺗﺠﺎﻋﯽ ﻗﺎﺑﻞ ﺗﺤﻤﻞ ﺳﺎزه ﻣﻮرد ارزﯾﺎﺑﯽ ﻗﺮار ﻣﯽﮔﯿﺮد. ﺑﺮ ﭘﺎﯾﻪ ﯾﺎﻓﺘﻪﻫﺎي ﻣﺪلﻫﺎي ﻋﺪدي اﮔﺮﭼﻪ ﻣﻮﻗﻌﯿﺖ اﻋﻤﺎل ﻧﺸﺴﺖ در ﻣﺤﻞ ﯾﮏ ﺳﺘﻮن ﻣﯿﺎﻧﯽ در ﻗﯿﺎس ﺑﺎ ﺳﺎﯾﺮ ﻣﻮﻗﻌﯿﺖﻫﺎي ﻣﻄﺎﻟﻌﻪ ﺷﺪه ﺑﻪ ﮐﻤﺘﺮﯾﻦ ﺗﻐﯿﯿﺮﻣﮑﺎن ﻗﺎﺋﻢ رو ﺑﻪ ﭘﺎﯾﯿﻦ ﺑﺮاي ﺗﺸﮑﯿﻞ اوﻟﯿﻦ ﻣﻔﺼﻞ ﭘﻼﺳﺘﯿﮏ در ﯾﮑﯽ از ﺗﯿﺮﻫﺎ ﻧﯿﺎز دارد اﻣﺎ ﺑﯿﺸﺘﺮﯾﻦ ﻧﺸﺴﺖﭘﺬﯾﺮي ﺳﺎزه در ﯾﮑﯽ از ﺣﺎﻻت ﻣﺮﺑﻮط ﺑﻪ وﻗﻮع ﻧﺸﺴﺖ در ﻣﻮﻗﻌﯿﺖ ﯾﮏ ﺳﺘﻮن ﮔﻮﺷﻪ رخ ﻣﯽدﻫﺪ. ﻫﻤﭽﻨﯿﻦ اﻟﮕﻮي ﺗﺸﮑﯿﻞ ﻣﻔﺎﺻﻞ ﭘﻼﺳﺘﯿﮏ و ﺑﺎزﺗﻮزﯾﻊ ﻧﯿﺮوﻫﺎي ﻣﺤﻮري در ﺑﯿﻦ ﺳﺘﻮنﻫﺎي ﻃﺒﻘﻪ اول ﺳﺎزه ﺗﺎ ﺣﺪ زﯾﺎدي ﺗﺤﺖ ﺗﺎﺛﯿﺮ ﺷﺮاﯾﻂ ﺗﮑﯿﻪﮔﺎﻫﯽ ﻣﺪل ﺷﺪه ﺑﺮاي ﭘﺎي ﺳﺘﻮنﻫﺎ ﻗﺮار ﻣﯽﮔﯿﺮد.

Natural hazards and human activities bring about overall or local ground subsidence. Predicting the effects of large differential settlement on response of structural frames, especially in congested urban areas, is a main issue in design process as inadvertence can lead to irrecoverable human and financial losses. In order to better understand the consequences of the subsidence phenomenon on the superstructure, a three dimensional reinforced concrete (RC) moment frame designed according to the current Iranian codes of practice is analyzed due to six separate nonlinear analysis cases considering three locations for the increasing differential settlements (under corner, exterior, and interior columns) as well as two support conditions (fixed and flexible); Various results including change in pattern of bridging beam bending moments, axial force redistribution in columns, and also maximum tolerable elastic and inelastic settlements are evaluated. Based on the findings of the numerical models, although cases with the settlement imposed under an interior column have the least vertical downward displacement at formation of first plastic hinge in a beam compared to corresponding cases, the highest capacity to bear differential settlement occurs due to one of the cases of a corner column location. Moreover, formation of plastic hinges and redistribution of axial forces in first-story columns are highly affected by the modeled support conditions.