بررسي تاثير عملكرد تنش پوستهها با استفاده از تئوري فنر معادل در بهينه سازي سولههاي قوسي

Optimal Design of Curved Portal Frame with Consideration of Stressed Skin Action Using the Equivalent Spring Theory

در اﯾﻦ ﭘﮋوﻫﺶ ﺗﺎﺛﯿﺮ ورق ﭘﻮﺷﺶ ﺳﻘﻒ و ﻋﻤﻠﮑﺮد ﺗﻨﺶ ﭘﻮﺳﺘﻪﻫﺎ در ﻃﺮاﺣﯽ ﺑﻬﯿﻨﻪ ﺳﻮﻟﻪﻫﺎي ﻗﻮﺳﯽ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﻣﯽﮔﯿﺮد. ﻃﺒﻖ ﻋﻤﻠﮑﺮد ﺗﻨﺶ ﭘﻮﺳﺘﻪﻫﺎ، ﺑﺨﺸﯽ از ﻧﯿﺮوي اﻓﻘﯽ وارد ﺑﺮ ﺳﺎزه، ﺗﻮﺳﻂ دﯾﺎﻓﺮاﮔﻢ و ﺑﺨﺸﯽ ﺗﻮﺳﻂ ﻗﺎب ﺗﺤﻤﻞ ﻣﯽﺷﻮد و ﻗﺎبﻫﺎ ﺑﺮاي ﻧﯿﺮوي ﮐﻤﺘﺮ ﻃﺮاﺣﯽ ﻣﯽﮔﺮدﻧﺪ در ﻧﺘﯿﺠﻪ اﯾﻦ ﻋﻤﻠﮑﺮد ﻧﻘﺶ اﺳﺎﺳﯽ در ﻃﺮاﺣﯽ ﺑﻬﯿﻨﻪ ﺳﻮﻟﻪﻫﺎ ﺧﻮاﻫﺪ داﺷﺖ. ﺗﺌﻮري ﻓﻨﺮ ﻣﻌﺎدل، روش ﻣﻮرد اﺳﺘﻔﺎده ﺑﺮاي ﻃﺮاﺣﯽ اﯾﻦ ﻋﻤﻠﮑﺮد در اﯾﻦ ﭘﮋوﻫﺶ ﻣﯽﺑﺎﺷﺪ. ﺟﻬﺖ ﻃﺮاﺣﯽ ﺳﺮﯾﻊ و آﺳﺎن ﺳﻮﻟﻪﻫﺎ، ﺑﺎ ﺑﺮﻗﺮاري ارﺗﺒﺎط ﺑﯿﻦ ﻧﺮم اﻓﺰارﻫﺎي Sap2000 و Matlab و اﺳﺘﻔﺎده از اﻟﮕﻮرﯾﺘﻢ ژﻧﺘﯿﮏ، ﻧﺮم اﻓﺰار ﻃﺮاﺣﯽ ﺳﻮﻟﻪ ﻓﺮاﻫﻢ ﺷﺪه اﺳﺖ ﮐﻪ اﯾﻦ ﻧﺮم اﻓﺰار ﺑﺎ اﺳﺘﻔﺎده از اﺑﻌﺎد ﺳﻮﻟﻪ و ﺷﺮاﯾﻂ ﻣﺤﯿﻄﯽ ﻣﺤﻞ اﺳﺘﻘﺮار ﺳﻮﻟﻪ، ﺑﻪ ﻫﺮ دو روش ﺗﻨﺶ ﻣﺠﺎز و ﻋﻤﻠﮑﺮد ﺗﻨﺶ ﭘﻮﺳﺘﻪﻫﺎ ﺑﻪ ﻃﺮاﺣﯽ ﺳﺎزه ﺑﺎ ﺑﻬﺘﺮﯾﻦ ﻣﻘﺎﻃﻊ ﻣﯽﭘﺮدازد. ﺗﻮﺳﻂ اﯾﻦ ﻧﺮم اﻓﺰار ﻫﻔﺖ ﺳﻮﻟﻪ ﻗﻮﺳﯽ ﺑﺎ اﺑﻌﺎد دﻫﺎﻧﻪ، ﻃﻮل، ﺗﻌﺪاد ﻗﺎب و ارﺗﻔﺎع ﺳﺘﻮن ﻣﺘﻔﺎوت ﺑﺎ ﺿﺨﺎﻣﺖ ﭘﻮﺷﺶ ﺳﻘﻒ 0/5 و 0/7 ﻣﯿﻠﯽ ﻣﺘﺮ ﻃﺮاﺣﯽ و ﻋﻤﻠﮑﺮد ﺗﻨﺶ ﭘﻮﺳﺘﻪﻫﺎ در آنﻫﺎ ﺑﺮرﺳﯽ ﻣﯽﺷﻮد. ﺗﺎﺑﻊ ﻫﺪف وزن ﺳﺎزه اﺳﺖ و ﻣﺴﺌﻠﻪ ﺷﺎﻣﻞ 8 ﻣﺘﻐﯿﺮ ﻃﺮاﺣﯽ ﻣﯽﺑﺎﺷﺪ. ﺑﺮرﺳﯽ ﻧﺘﺎﯾﺞ اﯾﻦ ﻣﻘﺎﻟﻪ ﻧﺸﺎن ﻣﯽدﻫﺪ ﮐﻪ ﻋﻤﻠﮑﺮد ﺗﻨﺶ ﭘﻮﺳﺘﻪﻫﺎ ﺑﯿﺶ از 20 درﺻﺪ در ﮐﺎﻫﺶ وزن ﺗﺎﺛﯿﺮ دارد و ﻣﯿﺰان اﯾﻦ ﺗﺎﺛﯿﺮ ﺑﻪ اﺑﻌﺎد ﺳﺎزه واﺑﺴﺘﻪ اﺳﺖ ﺑﻪ ﻃﻮرﯾﮑﻪ اﻓﺰاﯾﺶ ارﺗﻔﺎع ﺳﺘﻮنﻫﺎ ﺣﺪود 10 درﺻﺪ ﺗﺎﺛﯿﺮ اﯾﻦ ﻋﻤﻠﮑﺮد را اﻓﺰاﯾﺶ ﻣﯽدﻫﺪ و اﻓﺰاﯾﺶ دﻫﺎﻧﻪ ﺳﻮﻟﻪ از ﺗﺎﺛﯿﺮ ﻋﻤﻠﮑﺮد ﺗﻨﺶ ﭘﻮﺳﺘﻪ-اي ﺑﯿﺶ از 5 درﺻﺪ ﻣﯽﮐﺎﻫﺪ. اﻓﺰاﯾﺶ ﺗﻌﺪاد ﻗﺎبﻫﺎ و ﺗﻐﯿﯿﺮ ﻃﻮل ﺳﺎزه ﺗﺎﺛﯿﺮي ﻧﺎﭼﯿﺰ و در ﺣﺪود 1 ﯾﺎ 2 درﺻﺪ دارد. ﺗﻐﯿﯿﺮ ﺿﺨﺎﻣﺖ ورق ﭘﻮﺷﺶ ﺑﻪ اﻧﺪازه 0/2 ﻣﯿﻠﯽﻣﺘﺮ، ﺣﺪود 3 درﺻﺪ در ﮐﺎﻫﺶ ﺑﯿﺸﺘﺮ وزن ﻣﻮﺛﺮ ﺧﻮاﻫﺪ ﺑﻮد.

This article investigates the effect of the roof cover and the stressed skin action on the optimal design of curved portal frames. According to stressed skin effect, diaphragm is carrying part of the horizontal force of structure and the remaining part is carried out by the frames. Therefore, interior frames are designed for lower forces which, in turn, results in a lighter structure. Stressed skin effect is modelled using the equivalent spring theory. A program which links Sap2000 and genetic algorithm was developed that provides the best sections which result in the minimum weight of structure. Designs are performed by using the allowable stress design and stress skin effect. Seven curved portal frames with different span dimensions, lengths, number of frames and column heights are considered and optimally designed for roof cover with thickness of 0.5 mm and 0.7mm. The objective function is defined as the weight of the structure and the problem consists of eight design variables. The results show that consideration of the stressed skin effect results in a reduction of weight by more than 20% and that increasing the height of column results in 10% reduction of the weight. Moreover, it was observed that increasing the length of the span results in a 5% reduction in weight. Effects of increasing the number of frames and changing the length of the structure are negligible and are only about 1 or 2 percent of reduction in weight. Increase in the thickness of the roof cover sheet about 0.2 mm results in a decrease of the weight by about 3%.