مهارﺑﻨﺪﻫﺎی ﮐﻤﺎﻧﺶ ﺗﺎب ﻃﻮل ﮐﻮﺗﺎه: روش ﻃﺮاﺣﯽ و ﺑﺮرﺳﯽ رﻓﺘﺎر ﻟﺮزه ای

مهاربندﻫﺎی ﮐﻤﺎﻧﺶﺗﺎب ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﺷﮑﻞ ﭘﺬﯾﺮی ﺑﺎﻻ و رﻓﺘﺎر ﺗﻘﺮﯾﺒﺎً ﯾﮑﺴﺎن در ﮐﺸﺶ و ﻓﺸﺎر، ﻣﺪتﻫﺎ اﺳﺖ ﮐﻪ در ﮐﺸﻮرﻫﺎی ﭘﯿﺸﺮﻓﺘﻪ دﻧﯿﺎ ﺑﻪ ﮐﺎر ﮔﺮﻓﺘﻪ ﻣﯽﺷﻮد. ﯾﮑﯽ از ﺑﻬﺒﻮدﻫﺎ ﺑﺮ روی اﯾﻦ ﺳﯿﺴﺘﻢ، اﺳﺘﻔﺎده از ﻣﻬﺎرﺑﻨﺪﻫﺎی ﮐﻤﺎﻧﺶﺗﺎب ﺑﺎ ﻃﻮل ﮐﻤﺘﺮ ﻧﺴﺒﺖ ﺑه نوع ﻣﺘﻌﺎرفِ اﯾﻦ ﺳﯿﺴﺘﻢ ﻣﯽﺑﺎﺷﺪ. ﻣﻬﺎرﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎبِ ﻃﻮل ﮐﻮﺗﺎه دارای ﻣﺰﯾﺖﻫﺎﯾﯽ ﻧﻈﯿﺮ اﻣﮑﺎن اﻧﺘﺨﺎب ﻣﺴﺘﻘﻞ دو ﭘﺎراﻣﺘﺮ ﺳﺨﺘﯽ ﻣﻘﺎوﻣﺖ، ﮐﺎﻫﺶ ﻫﺰﯾﻨﻪ ﺳﺎﺧﺖ، اﻧﻌﻄﺎف در ﻣﻮﻗﻌﯿﺖ ﻧﺼﺐ و اﻓﺰاﯾﺶ ﺳﺨﺘﯽ ﭘﺲ از ﺗﺴﻠﯿﻢ ﻣﯽﺑﺎﺷﺪ. در اﯾﻦ ﻣﻘﺎﻟﻪ اﺑﺘﺪا ﺑﻪ ﻣﻌﺮﻓﯽ ﻃﺮح ﭘﯿﺸﻨﻬﺎدی و ﻣﺰﯾﺖﻫﺎی ﮐﺎﻫﺶ ﻃﻮل در ﻣﻬﺎرﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎب ﭘﺮداﺧﺘﻪ و ﺳﭙﺲ ﻣﺒﺎﻧﯽ ﻃﺮاﺣﯽ ﻟﺮزه ای اﯾﻦ روش ﺑﯿﺎن ﻣﯽ ﺷﻮد. در اداﻣﻪ دو ﺳﺎﺧﺘﻤﺎن 7 ﻃﺒﻘﻪ ﺑﺎ ﯾﮏ ﭘﻼن ﻣﺘﻌﺎرف ﺑﺎ ﻣﻬﺎرﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎب ﻣﺘﻌﺎرف و ﻃﻮل ﮐﻮﺗﺎه ﻣﻮرد ﻃﺮاﺣﯽ ﻗﺮار ﻣﯽﮔﯿﺮد و ﻧﺘﺎﯾﺞ ﻃﺮاﺣﯽ اراﺋﻪ ﻣﯽ ﺷﻮد. ﺑﻪ ﻣﻨﻈﻮر درک ﺑﻬﺘﺮ و ﻣﻘﺎﯾﺴﻪ اﯾﻦ ﻧﻮع ﻣﻬﺎرﺑﻨﺪ، ﻧﺘﺎﯾﺞ ﻣﻘﺎﯾﺴﻪای ﻃﺮاﺣﯽ ﻟﺮزه ای و ﺗﺤﻠﯿﻞ ﺗﺎرﯾﺨﭽﻪ زﻣﺎﻧﯽ ﺑﺮای مهارﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎب و ﻣﻬﺎرﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎب ﻃﻮل ﮐﻮﺗﺎه ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﻣﯽﮔﯿﺮد. از ﻧﻘﻄﻪ ﻧﻈﺮ وزن ﻣﺼﺎﻟﺢ ﻣﺼﺮﻓﯽ، وزن ﺳﺎزه ﺑﺎ ﻣهارﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎب ﻃﻮل ﮐﻮﺗﺎه در ﺣﺪود 6 درﺻﺪ از ﺳﺎزه ﺑﺎ ﻣﻬﺎرﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎب ﻃﻮل ﺑﻠﻨﺪ ﺳﺒﮏﺗﺮ اﺳﺖ. ﻧﺘﺎﯾﺞ ﺗﺤﻠﯿﻞ ﺗﺎرﯾﺨچه زﻣﺎﻧﯽ ﻏﯿﺮﺧﻄﯽ ﻧﺸﺎن ﻣﯽدﻫﺪ ﻣﯿﺎﻧﮕﯿﻦ ﺣﺪاﮐﺜﺮ ﺗﻐﯿﯿﺮﻣﮑﺎن در ﺳﺎزه ﺑﺎ ﻣﻬﺎرﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎب ﻃﻮل ﮐﻮﺗﺎه، ﻧﺴﺒﺖ ﺑﻪ ﺳﺎزه ﺑﺎ ﻣﻬﺎرﺑﻨﺪ ﮐﻤﺎﻧﺶﺗﺎب ﻣﺘﺪاول در زﻟﺰﻟﻪ dbe و mce ﺑﻪ ﺗﺮﺗﯿﺐ 23% و %26 ﮐﺎﻫﺶ دارد. ﺑﻪ ﻃﻮر ﮐﻠﯽ ﻧﺘﺎﯾﺞ ﺗﺤﻠﯿﻞ ﺣﺎﮐﯽ از ﻋﻤﻠﮑﺮد ﻟﺮزه ای مناﺳﺐﺗﺮ ﺳﯿﺴﺘﻢﻫﺎی ﻣﻬﺎرﺑﻨﺪی ﮐﻤﺎﻧﺶﺗﺎب ﺑﺎ ﻃﻮل ﮐﻮﺗﺎه ﻣﯽﺑﺎﺷﺪ.

design of reduced length buckling restrained brace (rlbrb)

the bracing elements experience both tensile and compressive forces during an earthquake; however buckling is critical in bracing members. buckling-restrained brace (brb) - in which the buckling is prohibited - have long been used in developed countries due to their high ductility and similar behavior in tension and compression. one of the improvements on this system is the use of brb with reduced length rather than the whole brace as in conventional brbs. reduced length brb systems have advantages such as independent selection of two parameters of stiffness and strength, reduced construction cost, flexibility in installation position, and increasing stiffness after yielding. in this study the proposed reduced length brb system is presented. the basics of seismic design of reduced length brb frames are expressed. afterwards a benchmark structure once equipped with conventional and another one with reduced-length brb is designed and the result of design is presented. the comparative results of seismic design and time history analysis for brb structure and reduced length buckling-restrained brace (rlbrb) structure are discusses. the weight of elements of structure with reduced length brb (rlbrb) is 6% lighter than the structure with brb. the mean maximum drifts of the rlbrb structure in dbe and mce earthquake are 23% and 26% lesser than the brb structure. generally the results of the nonlinear analysis show better seismic performance of rlbrb in comparison to conventional brb.