ﺗﺎﺛﯿﺮ ﻣﻘﺎوﻣﺖ ﺑﺘﻦ و ﺿﺨﺎﻣﺖ دال ﺗﺨﺖ ﺑﺘﻨﯽ ﺑﺮ ﺟﻠﻮﮔﯿﺮي از ﺧﺮاﺑﯽ ﭘﯿﺸﺮوﻧﺪه ﻧﺎﺷﯽ از ﺣﺬف ﻧﺎﮔﻬﺎﻧﯽ ﯾﮏ ﺳﺘﻮن ﻣﯿﺎﻧﯽ

Effect of concrete strength and thickness of flat slab on preventing of progressive collapse caused by elimination of an internal column

ﻃﺮاﺣﯽ ﺳﺎﺧﺘﻤﺎنﻫﺎ ﺑﺮاي ﻣﻘﺎوﻣﺖ در ﺑﺮاﺑﺮ ﺧﺮاﺑﯽ ﭘﯿﺸﺮوﻧﺪه، اﻣﺮي ﻏﯿﺮ ﻗﺎﺑﻞ اﻧﮑﺎر اﺳﺖ. ﻫﺮﭼﻨﺪ ﺑﺮﺧﯽ دﺳﺘﻮراﻟﻌﻤﻞﻫﺎ ﻣﺜﻞ GSA و UFC اﻟﺰاﻣﺎﺗﯽ ﺑﺮاي ﮐﺎﻫﺶ اﺣﺘﻤﺎل ﺧﺮاﺑﯽ ﭘﯿﺸﺮوﻧﺪه در ﺳﺎزهﻫﺎ ﭘﯿﺸﻨﻬﺎد دادهاﻧﺪ، اﻣﺎ ﺑﻪ دﻟﯿﻞ اﯾﻦﮐﻪ ﻣﺎﻫﯿﺖ ﺑﺎرﻫﺎ ﯾﺎ وﻗﺎﯾﻊ ﻣﺴﺒﺐ ﻓﺮوﭘﺎﺷﯽ، ﺑﻪ ﺧﻮﺑﯽ ﺗﻌﺮﯾﻒ ﻧﺸﺪهاﻧﺪ و ﻋﻤﻠﮑﺮد اﺟﺰاي ﺳﺎﺧﺘﻤﺎن در ﻃﻮل ﺧﺮاﺑﯽ ﭘﯿﺸﺮوﻧﺪه ﺑﻪ ﺧﻮﺑﯽ ﻗﺎﺑﻞ درك ﻧﯿﺴﺖ، ﭘﯿﺶ ﺑﯿﻨﯽ اﻟﮕﻮي ﻣﺸﺨﺼﯽ ﮐﻪ ﺑﯿﺎنﮔﺮ ﺳﯿﺮ اﻓﺰاﯾﺶ ﺧﺮاﺑﯽ ﺑﺎﺷﺪ ﻣﺸﮑﻞ اﺳﺖ. در اﯾﻦ ﭘﮋوﻫﺶ، ﺑﺎ اﺳﺘﻔﺎده از رﻓﺘﺎر ﻏﺸﺎﯾﯽ دالﻫﺎ، اﺛﺮ ﻣﻘﺎوﻣﺖ ﺑﺘﻦ و ﺿﺨﺎﻣﺖ دال ﺑﺮ ﺟﻠﻮﮔﯿﺮي از ﺧﺮاﺑﯽ ﭘﯿﺸﺮوﻧﺪهي دالﻫﺎي ﺑﺘﻦ ﻣﺴﻠﺢ ﭘﺲ از ﺣﺬف ﻧﺎﮔﻬﺎﻧﯽ ﯾﮏ ﺳﺘﻮن ﻣﯿﺎﻧﯽ ﺑﺮرﺳﯽ ﻣﯽﺷﻮد. ﺧﺮاﺑﯽ ﭘﯿﺸﺮوﻧﺪه در دالﻫﺎي ﻃﺮاﺣﯽ ﺷﺪه ﺑﺎ ﺣﺬف ﻧﺎﮔﻬﺎﻧﯽ ﯾﮏ ﺳﺘﻮن داﺧﻠﯽ ﺷﺒﯿﻪﺳﺎزي و ﻇﺮﻓﯿﺖ دال در ﺣﻀﻮر ﻧﯿﺮوي ﻏﺸﺎﯾﯽ ﻓﺸﺎري ﺑﺮاي ﻣﻘﺎوﻣﺖﻫﺎي ﺑﺘﻦ ﻣﺨﺘﻠﻒ و ﺿﺨﺎﻣﺖﻫﺎي ﮔﻮﻧﺎﮔﻮن دال ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﻗﺎﺑﻠﯿﺖ ﺣﻤﻞ ﺑﺎر ﺑﺮاي دﻫﺎﻧﻪي اﻓﺰاﯾﺶﯾﺎﻓﺘﻪي دال ﺑﻪ ﻋﻠﺖ ﺣﺬف ﻧﺎﮔﻬﺎﻧﯽ ﺳﺘﻮن ﻣﯿﺎﻧﯽ، ﺑﺮاي ﻧﻤﻮﻧﻪﻫﺎي ﻣﺨﺘﻠﻒ ﺑﺮرﺳﯽ ﺷﺪ. ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از ﻣﻄﺎﻟﻌﻪ و ﺑﺮرﺳﯽ ﻧﺸﺎن داد ﮐﻪ اﺛﺮ ﻏﺸﺎﯾﯽ دال ﮐﻪ اﻏﻠﺐ در ﻃﺮاﺣﯽ در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﻧﻤﯽﺷﻮد، ﻣﯽﺗﻮاﻧﺪ ﺗﺎ ﺣﺪ زﯾﺎدي از ﺧﺮاﺑﯽ ﭘﯿﺸﺮوﻧﺪهي دال و ﺳﺎزه ﺟﻠﻮﮔﯿﺮي ﮐﻨﺪ. ﻫﻢﭼﻨﯿﻦ ﺑﺎ اﻓﺰاﯾﺶ ﻣﻘﺎوﻣﺖ ﺑﺘﻦ دال و اﻓﺰاﯾﺶ ﺿﺨﺎﻣﺖ دال ﻧﺴﺒﺖ ﺑﻪ ﺣﺪاﻗﻞ ﭘﯿﺸﻨﻬﺎدي آﯾﯿﻦ ﻧﺎﻣﻪ ﻣﯽﺗﻮان ﻇﺮﻓﯿﺖ دال را ﭘﺲ از ﺣﺬف ﻧﺎﮔﻬﺎﻧﯽ ﯾﮏ ﺳﺘﻮن ﻣﯿﺎﻧﯽ ﺑﻪ ﻣﻘﺪار ﻗﺎﺑﻞ ﻣﻼﺣﻈﻪاي اﻓﺰاﯾﺶ داد.

Designing structures against progressive collapse is an important part of the building design. However, some guidelines such as GSA and UFC holds implications for reducing the risk of progressive collapse of structures, but because the nature of the loads or events that cause damage are not well defined and the performance of building components during progressive collapse is not well understood, It is difficult to predict the trend of increasing damage. In this study, using the membrane action of the slabs, the effect of concrete strength and slab thickness on preventing the progressive failure of RC concrete slabs is investigated after the sudden removal of an internal column. Progressive collapse in the designed slabs was simulated by the sudden removal of an internal column and the slab capacity was calculated in the presence of compressive membrane force for different concrete strengths and slab thicknesses. Load carrying capacity for an enlarged span of the slab due to the sudden removal of the middle column has been investigated for various models. The results of this study showed that the membrane action of the slab, which is often not considered in design, can greatly prevent progressive failure of the slab and structure. By increasing the strength of the concrete and the thickness of the slab as well as the minimum recommendation of the regulation, the capacity of the slab can be considerably increased after the sudden removal of the middle column.