ﺮرﺳﯽ آزﻣﺎﯾﺸﮕﺎﻫﯽ اﺗﺼﺎﻻت ﺧﺎرﺟﯽ ﺗﯿﺮ ﺑﻪ ﺳﺘﻮن ﺑﺘﻦ ﻣﺴﻠﺢ ﺑﺎ ﻣﯿﻠﮕﺮدﻫﺎي ﻓﻮﻻدي و آﻟﯿﺎژﻫﺎي ﻣﺤﺎﻓﻈﻪ دار ﺷﮑﻠﯽ ﺗﺤﺖ ﺗﺎﺛﯿﺮ ﺑﺎرﻫﺎي ﭼﺮﺧﻪ اي

Experimental Investigation on Exterior RC Beam-Column Connections Subjected to Cyclic Loading using Steel and Shape Memory Alloy (SMA) Reinforcing Bars

در اﯾﻦ ﭘﮋوﻫﺶ آزﻣﺎﯾﺸﮕﺎﻫﯽ، رﻓﺘﺎر اﺗﺼﺎل ﺧﺎرﺟﯽ ﺗﯿﺮ ﺑﻪ ﺳﺘﻮن ﺑﺘﻨﯽ ﺗﺤﺖ ﺗﺎﺛﯿﺮ ﺑﺎرﮔﺬاري ﭼﺮﺧﻪ اي ﺑﺎ ﻣﯿﻠﮕﺮدﻫﺎي آﻟﯿﺎژي ﺣﺎﻓﻈﻪ دار ﺷﮑﻠﯽ SMA)( ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﻣﯽ ﮔﯿﺮد .در اﯾﻦ ﭘﮋوﻫﺶ 8 ﻧﻤﻮﻧﻪ ﺑﺘﻨﯽ ﺳﺎﺧﺘﻪ و آزﻣﺎﯾﺶ ﺷﺪ. در 4 ﻧﻤﻮﻧﻪ از ﻣﯿﻠﮕﺮدﻫﺎي آﻟﯿﺎژي ﺣﺎﻓﻈﻪ دار ﺷﮑﻠﯽ و در 4 ﻧﻤﻮﻧﻪ دﯾﮕﺮ از ﻣﯿﻠﮕﺮدﻫﺎي ﻓﻮﻻدي، ﺑﺮاي اﺗﺼﺎل ﺗﯿﺮ ﺑﻪ ﺳﺘﻮن اﺳﺘﻔﺎده ﺷﺪه اﺳﺖ. ﻣﯿﺰان ﻣﺤﺼﻮر ﺷﺪﮔﯽ ﻣﯿﻠﮕﺮدﻫﺎي ﻃﻮﻟﯽ ﺗﯿﺮ در ﻣﺤﻞ اﺗﺼﺎل ﻧﻤﻮﻧﻪﻫﺎ ، ﻣﺘﻔﺎوت در ﻧﻈﺮ ﮔﺮﻓﺘﻪ ﺷﺪه اﺳﺖ. ﻫﻤﭽﻨﯿﻦ از دو ﻧﻮع ﺑﺘﻦ، ﺑﺎ ﻣﻘﺎوﻣﺖ ﻫﺎي 30 و 45 ﻣﮕﺎ ﭘﺎﺳﮑﺎل اﺳﺘﻔﺎده ﺷﺪه اﺳﺖ. ﻧﻤﻮﻧﻪﻫﺎ ﺗﺤﺖ ﺑﺎرﮔﺬاري ﭼﺮﺧﻪ اي آزﻣﺎﯾﺶ ﺷﺪﻧﺪ. ﻧﺘﺎﯾﺞ ﭘﮋوﻫﺶ ﻧﺸﺎن ﻣﯽ دﻫﺪ ﮐﻪ ﻣﯿﻠﮕﺮدﻫﺎي آﻟﯿﺎژي ﺣﺎﻓﻈﻪ دار ﺷﮑﻠﯽ، ﺗﻮاﻧﺎﯾﯽ ﺑﺎﻻﯾﯽ در ﺑﺎزﮔﺸﺖ ﺑﻪ ﺷﮑﻞ اوﻟﯿﻪ ﺧﻮد، ﺑﻌﺪ از ﺗﺤﻤﻞ ﺗﻐﯿﯿﺮ ﻣﮑﺎن ﻫﺎي ﺑﺰرگ را دارﻧﺪ. در اﯾﻦ ﻣﺼﺎﻟﺢ ﻣﻘﺪار ﺟﺬب اﻧﺮژي ﻣﻨﺎﺳﺐ ﺑﻮده و ﮐﺎﻫﺶ ﺗﻐﯿﯿﺮ ﺷﮑﻞ ﭘﺴﻤﺎﻧﺪ در اﺗﺼﺎل ﻗﺎﺑﻞ ﻣﻼﺣﻈﻪ ﻣﯽ ﺑﺎﺷﺪ. ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ رﻓﺘﺎر ﻓﻮق اﻻﺳﺘﯿﮏ ﻣﯿﻠﮕﺮدﻫﺎي آﻟﯿﺎژي ﺣﺎﻓﻈﻪ دار ﺷﮑﻠﯽ، در ﺑﺘﻦ ﻣﻌﻤﻮﻟﯽ و ﻣﻘﺎوﻣﺖ ﺑﺎﻻ ﺗﺮكﻫﺎ در ﻫﺴﺘﻪ اﺗﺼﺎل ﻗﺎﺑﻞ ﻣﻼﺣﻈﻪ ﻧﺒﻮده و ﺑﺎرﮔﺬاري ﭼﺮﺧﻪ اي، ﻣﻮﺟﺐ ﺑﺴﺘﻪ ﺷﺪن ﺗﺮكﻫﺎ در ﻫﺴﺘﻪ اﺗﺼﺎل ﮔﺮدﯾﺪ. ﺑﺎ اﻓﺰاﯾﺶ ﺑﺎرﮔﺬاري ﭼﺮﺧﻪ اي، ﺷﮑﺴﺖ ﺧﺎرج از ﻫﺴﺘﻪ اﺗﺼﺎل ﺑﻪ ﺻﻮرت ﺧﻤﺸﯽ و در ﺗﯿﺮ اﯾﺠﺎد ﮔﺮدﯾﺪ. اﻓﺰاﯾﺶ ﻣﺤﺼﻮر ﺷﺪﮔﯽ ﺗﯿﺮ ﺑﺎﻋﺚ دور ﺷﺪن ﻣﺤﻞ ﺷﮑﺴﺖ در ﺗﯿﺮ از ﻫﺴﺘﻪ اﺗﺼﺎل ﮔﺮدﯾﺪ. در اﺗﺼﺎل ﺗﯿﺮ ﺑﻪ ﺳﺘﻮن ﺑﺎ ﻣﯿﻠﮕﺮدﻫﺎي ﻓﻮﻻدي، ﺷﮑﺴﺖ ﺑﺮﺷﯽ در ﻫﺴﺘﻪ اﺗﺼﺎل اﯾﺠﺎد ﺷﺪ وﻟﯽ ﺑﺎ اﻓﺰاﯾﺶ ﻣﻘﺎوﻣﺖ ﺑﺘﻦ و ﻣﺤﺼﻮر ﺷﺪﮔﯽ، ﺷﮑﺴﺖ در ﺧﺎرج از ﻫﺴﺘﻪ اﺗﺼﺎل ﺑﻪ ﺻﻮرت ﺧﻤﺸﯽ در ﺗﯿﺮ ﺻﻮرت ﮔﺮﻓﺖ. ﻃﻮل ﻣﻔﺼﻞ ﭘﻼﺳﺘﯿﮏ در ﺗﯿﺮ اﺗﺼﺎل ﺑﺮاي ﻧﻤﻮﻧﻪﻫﺎي ﺑﺎ ﻣﯿﻠﮕﺮدﻫﺎي آﻟﯿﺎژي ﺣﺎﻓﻈﻪ دار ﺷﮑﻠﯽ و ﻣﯿﻠﮕﺮدﻫﺎي ﻓﻮﻻدي، ﺗﻮﺳﻂ رواﺑﻂ ﺗﺠﺮﺑﯽ و ﻧﺘﺎﯾﺞ آزﻣﺎﯾﺸﮕﺎﻫﯽ ﻣﺤﺎﺳﺒﻪ ﮔﺮدﯾﺪ و ﻣﺸﺨﺺ ﺷﺪ ﮐﻪ اﺳﺘﻔﺎده از ﻣﻌﺎدﻟﻪ ﭘﺎول و ﭘﺮﯾﺴﺘﻠﯽ ﺑﺮاي اﺗﺼﺎﻻت ﺑﺘﻨﯽ ﺑﺎ ﻫﺮ دو ﻧﻮع ﻣﯿﻠﮕﺮد ﻣﻨﺎﺳﺐ اﺳﺖ.

In the present Experimental research, the behavior of exterior RC beam-column connections subjected to cyclic loading is studied using steel and shape memory alloy (SMA) reinforcing bars. In this research, 8 specimens of exterior RC beam-column connections were tested in which four specimens included SMA reinforcing bars and the remaining four specimens included steel bars. The confinement of beam longitudinal bars was different in the connections. Also, two types of concretes were used with the strengths 30 and 45 MPa, respectively.The specimens were tested under cyclic loading. The results of the research show that the specimens with SMA reinforcing bars can return to their initial shape after tolerating large displacements. In these specimens, the energy dissipation is satisfactory and the decrease in the residual deformation is significant. According to the superelastic behavior of the SMA reinforcing bars, the width of cracks is not significant in the connection core and cyclic loading reduced the cracks in the connection core. As the cyclic loading increased, bending failure occurred in the beam outside of the connection core. As the concrete strength and confinement value increased, bending failure still occurred in the beam outside of the connection core. In the beam-column connection with steel bars, shear failure occurred in the connection core. However, as the concrete strength and confinement increased, bending failure occurred in the beam outside of the connection core. Plastic hinge length in the connecting beams were calculated in the specimens with SMA and steel bars by empirical equations and compared with the test results. It was shown that Paulay and Priestley equations were suitable to be used for concrete connections with different bars.