ﺑﺮرﺳﯽ ﺗﺎﺛﯿﺮ ﻣﻘﺎوﻣﺖ و ﻣﺸﺨﺼﺎت ﻧﺒﺸﯽ ﺑﺮ رﻓﺘﺎر اﺗﺼﺎل ﻓﻮﻻدي ﭘﺲﮐﺸﯿﺪه ﺑﺎ ﻧﺒﺸﯽ ﻓﻮﻗﺎﻧﯽ و ﺗﺤﺘﺎﻧﯽ

Evaluating the Effect of Strength and Geometry Parameters of Angle on Behavior of Post-Tensioned Steel Connection with Top and Bottom Angles

در اﺛﺮ زﻟﺰﻟﻪي ﺳﺎل 1994 ﻧﻮرﺗﺮﯾﺞ ﺗﻌﺪاد زﯾﺎدي از ﺳﺎﺧﺘﻤﺎنﻫﺎي ﻓﻮﻻدي ﺟﻮﺷﯽ ﺑﺎ ﺳﯿﺴﺘﻢ ﻗﺎب ﺧﻤﺸﯽ، در ﻧﺎﺣﯿﻪي اﺗﺼﺎﻻت ﺗﯿﺮ ﺑﻪ ﺳﺘﻮن دﭼﺎر ﺷﮑﺴﺖ ﺷﺪﻧﺪ. اﯾﻦ ﺧﺮاﺑﯽ در اﺗﺼﺎﻻت ﻗﺎبﻫﺎي ﺧﻤﺸﯽ ﮐﻪ ﺑﺮ ﺧﻼف اﻧﺘﻈﺎر ﻣﻬﻨﺪﺳﺎن ﺑﻮد، ﺑﺎﻋﺚ ﺷﺪ ﺗﺎ ﻧﻮع ﻧﮕﺎه ﺑﻪ اﺗﺼﺎﻻت اﯾﻦ ﻗﺎبﻫﺎ دﭼﺎر ﺗﻐﯿﯿﺮ ﺷﻮد. ﺑﻪ ﻫﻤﯿﻦ دﻟﯿﻞ ﻣﻬﻨﺪﺳﺎن ﺑﺮ آن ﺷﺪﻧﺪ ﺗﺎ اﺗﺼﺎﻻﺗﯽ ﺑﺎ ﺷﮑﻠﭙﺬﯾﺮي ﺑﯿﺸﺘﺮ و ﺟﺰﺋﯿﺎﺗﯽ ﺟﺪﯾﺪ ﻣﻌﺮﻓﯽ ﮐﻨﻨﺪ. اﺗﺼﺎل ﭘﺲ ﮐﺸﯿﺪه ﯾﮑﯽ از اﺗﺼﺎﻻت ﻧﻮﯾﻦ اﺳﺖ ﮐﻪ ﺗﻮﺳﻂ ﻣﺤﻘﻘﺎن ﭘﯿﺸﻨﻬﺎد ﺷﺪه اﺳﺖ. اﺗﺼﺎﻻت ﭘﺲ ﮐﺸﯿﺪه، ﺷﺎﻣﻞ ﮐﺎﺑﻞﻫﺎي ﭘﺲ ﮐﺸﯿﺪه ﺑﺎ ﻣﻘﺎوﻣﺖ ﺑﺎﻻ ﺑﺮاي اﯾﺠﺎد ﺧﺎﺻﯿﺖ ﺧﻮد ﻣﺮﮐﺰي و اﺗﻼف ﮐﻨﻨﺪهﻫﺎي اﻧﺮژي ﺑﺮاي ﮐﻨﺘﺮل ﺗﻐﯿﯿﺮﺷﮑﻞﻫﺎي ﭘﻼﺳﺘﯿﮏ ﻫﺴﺘﻨﺪ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ ﻣﺪﻟﺴﺎزي ﻋﺪدي اﺗﺼﺎل ﭘﺲ ﮐﺸﯿﺪه ﺑﺎ اﺳﺘﻔﺎده از ﻧﺮم اﻓﺰار اﺟﺰاي ﻣﺤﺪود آﺑﺎﮐﻮس اﻧﺠﺎم ﮔﺮﻓﺘﻪ و ﺿﻤﻦ ﮐﻨﺘﺮل ﺻﺤﺖ ﻣﺪﻟﺴﺎزي ﺑﺎ ﻧﺘﺎﯾﺞ آزﻣﺎﯾﺸﮕﺎﻫﯽ، 6 ﻧﻤﻮﻧﻪ از اﺗﺼﺎل ﻣﺪﻟﺴﺎزي ﺷﺪه و ﺗﺎﺛﯿﺮ ﺑﺮﺧﯽ ﭘﺎراﻣﺘﺮﻫﺎ ﺷﺎﻣﻞ اﺳﺘﻔﺎده از ﻓﻮﻻد ﭘﺮﻣﻘﺎوﻣﺖ ﺑﺮاي ﻧﺒﺸﯽ، اﺳﺘﻔﺎده از ﻧﺒﺸﯽ ﺑﺎ ﺳﺎق ﻧﺎﻣﺴﺎوي، اﺳﺘﻔﺎده از ﺳﺨﺖ ﮐﻨﻨﺪه ﺑﺮاي ﻧﺒﺸﯽ و اﺛﺮ ﻧﺴﺒﺖ ﻃﻮل آزﻣﻮن ﺑﻪ ﺿﺨﺎﻣﺖ ﻧﺒﺸﯽ)g/t ( ﺑﺮ رﻓﺘﺎر اﺗﺼﺎل ﺗﺤﺖ ﺑﺎرﮔﺬاري ﭼﺮﺧﻪ اي ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﻣﯽ ﮔﯿﺮد. در ﻣﺤﺪوده ﻣﺪلﻫﺎي اﯾﻦ ﻣﻘﺎﻟﻪ ﻧﺘﺎﯾﺞ ﻧﺸﺎن ﻣﯽ دﻫﺪ ﮐﻪ اﺳﺘﻔﺎده از ﻓﻮﻻد ﺑﺎ ﻣﻘﺎوﻣﺖ ﺗﺴﻠﯿﻢ ﺑﺎﻻﺗﺮ ﺑﺮاي ﻧﺒﺸﯽ ﺑﺎﻋﺚ اﻓﺰاﯾﺶ ﺟﺰﺋﯽ ﻇﺮﻓﯿﺖ ﺧﻤﺸﯽ و ﺗﻮان اﺗﺼﺎل در ﺗﺤﻤﻞ ﺑﺎر ﺟﺎﻧﺒﯽ ﻣﯽ ﺷﻮد. ﻫﻤﭽﻨﯿﻦ ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ اﺳﺘﻔﺎده از ﻧﺒﺸﯽ ﺑﺎ ﻃﻮل ﺳﺎق ﻧﺎﻣﺴﺎوي ﺗﺎﺛﯿﺮي ﺑﺮ رﻓﺘﺎر اﺗﺼﺎل ﻧﺪارد. اﺳﺘﻔﺎده از ﺳﺨﺖ ﮐﻨﻨﺪه ﺑﺮاي ﻧﺒﺸﯽ، ﺑﺎﻋﺚ اﻓﺰاﯾﺶ ﻇﺮﻓﯿﺖ ﺧﻤﺸﯽ، ﺗﻮان اﺗﺼﺎل در ﺗﺤﻤﻞ ﺑﺎر ﺟﺎﻧﺒﯽ، اﺗﻼف اﻧﺮژي، ﺳﺨﺘﯽ اوﻟﯿﻪ و ﺳﺨﺘﯽ ﻣﺎﻧﺪﮔﺎر اﺗﺼﺎل ﻣﯽ ﺷﻮد. ﻫﻤﭽﻨﯿﻦ ﮐﺎﻫﺶ ﻧﺴﺒﺖ ﻃﻮل آزﻣﻮن ﺑﻪ ﺿﺨﺎﻣﺖ ﻧﺒﺸﯽ )g/t ( از 4 ﺑﻪ 3/6، ﺑﺎﻋﺚ اﻓﺰاﯾﺶ اﺗﻼف اﻧﺮژي اﺗﺼﺎل ﻣﯽ ﺷﻮد، ﺑﮕﻮﻧﻪ اي ﮐﻪ اﺗﻼف اﻧﺮژي در اﺗﺼﺎل ﺑﺎ ﻧﺴﺒﺖ )g/t ( ﮐﻤﺘﺮ، 17% ﺑﯿﺸﺘﺮ اﺳﺖ.

Due to the 1994 Northridge earthquake, many of welded steel moment resisting frames (WSMRF) collapsed in the connection area of the beam to a column. The damage in WSMRF, which was contrary to the expectations of the engineers, changed the attitude of the WSMRF. Thus, engineers decided to introduce more ductile and detailed connections. Post-Tensioned Connection (PTC) is one of the new connections proposed by them. PTC includes high strength, pre-tensioned cables to create self-centering properties and energy dissipation to control plastic deformation. In this study, the numerical modeling of the PTC was performed using the ABAQUS finite element software. In addition to verify the model accuracy with the experimental results, 6 types of the connection were modeled and the effect of some parameters including the use of high strength steel (HSS) angle, the application of angle with unequal leg length, the use of stiffness for angle and the effect of the ratio of length to thickness on connection behavior under cyclic loading are investigated. In the range of models of this paper, the results show that the use of HSS for an angle causes a slight increase in flexural strength and capacity in lateral load bearing. Also, results demonstrated that the use of an angle with an unequal leg length does not affect the behavior of the connection. The use of stiffness for angle increases bending strength, capacity, energy dissipation, initial and inelastic stiffness and durability. Also, the reduction of the gage length to the thickness (g/t) from 4 to 3.6 would increase the energy dissipation of the connection, so that the energy dissipation in the connection with a lower g/t ratio is 17% higher.