ارزيابي تأثير اعمال همزمان مؤلفه افقي و قائم زلزله بر رفتار لرزهاي سازههاي قاب خمشي فولادي با استفاده از تحليل ديناميكي افزايشي

Investigation of Ground Motion Vertical and Horizontal Component Effects on the IDA Curves for the Regular and Irregular Steel Moment Frames

در ﺗﺤﻠﯿﻞﻫﺎي دﯾﻨﺎﻣﯿﮑﯽ ﺳﺎزهﻫﺎ، ﻣﺆﻟﻔﻪ ﻗﺎﺋﻢ زﻟﺰﻟﻪ ﻣﯽﺗﻮاﻧﺪ ﺗﺄﺛﯿﺮ ﻗﺎﺑﻞﺗﻮﺟﻬﯽ ﺑﺮ رﻓﺘﺎر ﻟﺮزهاي اﻧﻮاع ﺳﯿﺴﺘﻢﻫﺎي ﺳﺎزهاي داﺷﺘﻪ ﺑﺎﺷﺪ. اﻋﻤﺎل ﻣﺆﻟﻔﻪ ﻗﺎﺋﻢ زﻟﺰﻟﻪ ﻣﯽﺗﻮاﻧﺪ ﺑﺎ اﻓﺰاﯾﺶ ﻧﯿﺮوي ﻣﺤﻮري در ﺳﺘﻮنﻫﺎ، ﺑﺎﻋﺚ ﺑﺮوز ﺧﺮاﺑﯽ در ﺳﺘﻮنﻫﺎ و ﻧﻬﺎﯾﺘﺎً ﺷﮑﺴﺖ ﮐﻠﯽ ﺳﺎزه ﺷﻮد. در زﻟﺰﻟﻪﻫﺎي ﻧﺰدﯾﮏ ﺑﻪ ﮔﺴﻞ ﮐﻪ ﻣﺆﻟﻔﻪ ﻗﺎﺋﻢ ﺑﺰرﮔﯽ دارﻧﺪ، ﺗﺄﺛﯿﺮ ﻣﺆﻟﻔﻪ ﻗﺎﺋﻢ ﺑﺎرزﺗﺮ اﺳﺖ. ﺑﺎ اﯾﻦوﺟﻮد، ﻫﻤﭽﻨﺎن در ﺑﺴﯿﺎري از ﺗﺤﻠﯿﻞﻫﺎي ﺗﺎرﯾﺨﭽﻪزﻣﺎﻧﯽ ﮐﻪ روي ﺳﯿﺴﺘﻢﻫﺎي ﺳﺎزهاي اﻧﺠﺎم ﻣﯽﺷﻮد، از ﺗﺄﺛﯿﺮات ﻣﺆﻟﻔﻪي ﻗﺎﺋﻢ زﻟﺰﻟﻪ ﺻﺮفﻧﻈﺮ ﻣﯽﺷﻮد. اﯾﻦ ﻣﻮﺿﻮع ﻣﯽﺗﻮاﻧﺪ ﻧﺘﺎﯾﺠﯽ را در ﺧﻼف ﺟﻬﺖ اﻃﻤﯿﻨﺎن ﺑﻪ ﻫﻤﺮاه داﺷﺘﻪ ﺑﺎﺷﺪ. در اﯾﻦ ﻣﻘﺎﻟﻪ، ﻣﯿﺰان ﺗﺄﺛﯿﺮ اﻋﻤﺎل ﻫﻢزﻣﺎن ﻣﺆﻟﻔﻪ ﻗﺎﺋﻢ و اﻓﻘﯽ زﻟﺰﻟﻪ ﺑﺮ ﻧﯿﺎز ﺗﻐﯿﯿﺮﻣﮑﺎن ﻏﯿﺮارﺗﺠﺎﻋﯽ و ﻧﯿﺰ ﻧﯿﺮوي ﻣﺤﻮري ﺳﺘﻮنﻫﺎ در ﺳﺎزهﻫﺎي ﻗﺎب ﺧﻤﺸﯽ ﻓﻮﻻدي از ﻃﺮﯾﻖ اﻧﺠﺎم ﺗﺤﻠﯿﻞﻫﺎي دﯾﻨﺎﻣﯿﮑﯽ اﻓﺰاﯾﺸﯽ روي 3 ﻗﺎب ﻧﻤﻮﻧﻪ ﺑﺎ ﭘﯿﮑﺮﺑﻨﺪيﻫﺎي ﻣﻨﻈﻢ و ﻧﺎﻣﻨﻈﻢ در ارﺗﻔﺎع، ﻣﻮرد ارزﯾﺎﺑﯽ ﻗﺮار ﻣﯽﮔﯿﺮد. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر، ﺗﺤﻠﯿﻞﻫﺎي دﯾﻨﺎﻣﯿﮑﯽ اﻓﺰاﯾﺸﯽ ﺑﺎ اﺳﺘﻔﺎده از ﯾﮏ ﻣﺠﻤﻮﻋﻪ دهﺗﺎﯾﯽ از رﮐﻮردﻫﺎي ﻧﺰدﯾﮏ ﺑﻪ ﮔﺴﻞ، ﯾﮏ ﺑﺎر ﺑﺪون ﻟﺤﺎظ ﻣﺆﻟﻔﻪ ﻗﺎﺋﻢ و ﺑﺎر دﯾﮕﺮ ﺑﻪ ﺻﻮرت اﻋﻤﺎل ﻫﻢزﻣﺎن ﻫﺮ دو ﻣﺆﻟﻔﻪ اﻓﻘﯽ و ﻗﺎﺋﻢ اﻧﺠﺎم ﺷﺪه و ﻧﺘﺎﯾﺞ ﺑﻪ دﺳﺖ آﻣﺪه ﺑﺮاي اﯾﻦ دو ﺣﺎﻟﺖ، ﻣﻮرد ﻣﻘﺎﯾﺴﻪ ﻗﺮار ﻣﯽﮔﯿﺮﻧﺪ. ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از ﺗﺤﻠﯿﻞﻫﺎ ﻧﺸﺎن ﻣﯽدﻫﺪ ﮐﻪ اﻋﻤﺎل ﻣﺆﻟﻔﻪ ﻗﺎﺋﻢ زﻟﺰﻟﻪ ﺑﻪ ﻃﻮر ﻣﯿﺎﻧﮕﯿﻦ ﻧﯿﺎز ﺗﻐﯿﯿﺮﻣﮑﺎﻧﯽ ﻗﺎبﻫﺎي ﺧﻤﺸﯽ ﻧﺎﻣﻨﻈﻢ را در ﺣﺪود 10درﺻﺪ اﻓﺰاﯾﺶ ﻣﯽدﻫﺪ. اﯾﻦ ﻣﯿﺰان اﻓﺰاﯾﺶ ﺑﺮاي ﻗﺎب ﻣﻨﻈﻢ ﺣﺪود 3درﺻﺪ اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﻣﺸﺨﺺ ﺷﺪ ﮐﻪ اﻋﻤﺎل ﻣﺆﻟﻔﻪ ﻗﺎﺋﻢ زﻟﺰﻟﻪﻫﺎي ﻧﺰدﯾﮏ ﺑﻪ ﮔﺴﻞ ﺑﺎﻋﺚ اﻓﺰاﯾﺶ دوﺑﺮاﺑﺮي ﻧﯿﺮوي ﻣﺤﻮري ﺳﺘﻮنﻫﺎ ﻣﯽﮔﺮدد.

The effect of seismic vertical components on the seismic behavior of structural systems can be considerable. The vertical component of ground motion records can cause the brittle collapse of columns resulting in global collapse of structures. This effect is more crucial for near fault ground motions with larger vertical accelerations. Nevertheless, the effect of seismic vertical excitations is neglected in time-history analysis procedures on common structural systems. This may results in unconservative results in dynamic analyses. Therefore, it is very important to evaluate the damaging effects of vertical component of seismic excitations. In this paper, the effect of vertical excitations on the seismic response of steel moment frames with regular and irregular configurations along the height. Incremental dynamic analysis is employed to consider the effect of seismic excitations with various intensities. In IDA analysis, the seismic loads are applied to the structures with increasing intensities. In this paper, the seismic loads are applied to the structures in two manners, once considering only the horizontal component and secondly considering vertical and horizontal components simultaneously. The IDA curves are compared for two cases to find the effect of vertical excitations on global seismic demands. Also, the evaluations are made separately for regular and irregular frames to find the effect of vertical irregularity. The observed results revealed that the vertical components may increase the nonlinear displacements, especially for large intensities. The investigations demonstrate that the increase of column axial forces causes brittle buckling of columns and expedites the formation of plastic hinges leading to global collapse of structure. In irregular frames with soft stories, the buckling of slender columns is more crucial than regular structures. Therefore, it is suggested that the vertical components are considered for analyzing steel moment frame structures against near fault ground motions.