底部框架—抗震墙房屋的抗震性能及层刚度比的影响规律分析
|
摘要
底部框架-抗震墙房屋能够满足底部大空间的需要,且建设成本相对较低,在中小城市的临街建筑、村镇建筑中得到广泛的应用。底部框架-抗震墙房屋容易形成“底柔上刚,头重脚轻”的结构体系,当底部框架发生地震破坏时可能导致结构的连续倒塌。汶川地震中,底部框架-抗震墙房屋的破坏严重、甚至倒塌,也有部分底部框架-抗震墙房屋震害较轻;结构破坏位置也不同,震害分为上部结构破坏和下部结构破坏两大类。因此有必要从整体结构性能方面了解底部框架-抗震墙房屋抗震性能的优劣、分析抗震性能的主要影响因素、找出结构抗震不利位置、给出抗震加强措施,为底部框架-抗震墙房屋的抗震设计提供参考。
以汶川地震的震害资料为基础,全面系统分析了底部框架-抗震墙房屋的震害特征;采用空间结构弹性模型、平面结构弹性和弹塑性模型、汶川地震灾区实际建筑,对比分析了底部框架-抗震墙房屋和砌体结构的抗震性能;以底框上部砌体结构层与底框结构层的层刚度之比(简称层刚度比)为控制指标,建立空间结构弹性模型、平面结构弹性和弹塑性模型,系统分析了层刚度比对底部框架-抗震墙房屋的抗震性能的影响。
研究得到的主要结论有:
①经合理设计的底部框架-抗震墙房屋的抗震性能与砌体结构相当,底部框架-抗震墙房屋破坏模型(底部耗能减少上部结构地震效应)可控性更强。严格的底部框架-抗震墙房屋抗震设计十分必要,特别是结构底部层刚度比合理取值、过渡层墙肢抗震设计和上部结构整体性设计尤为重要。
②控制层刚度比和实现“多道抗震防线”的思想是保证底框结构抗震性能的关键。现行规范给出的层刚度比控制条件可以保证底部框架-抗震墙房屋抗震性能,但缺乏对结构过渡层墙肢的抗震防严重开裂设计。为了发挥底部框架-抗震墙房屋的底部耗能、减小上部砌体地震作用效应,可以适当提高层刚度比的下限值,建议由1.0提高到1.5。
③底部框架-抗震墙房屋的过渡层可能成为结构抗震不利位置。由于底层框架变形与过渡层砌体墙肢变形不协调,导致过渡层墙肢出现开裂破坏;层刚度比越大,开裂破坏越严重。建议在过渡层底部墙体中采用加筋砌体、增设构造柱或提高墙体材料强度等构造措施,提高过渡层墙肢的延性和抗剪强度,避免位移不协调引起墙肢的开裂破坏,新规范(征求意见稿)补充了过渡层砌体墙的相关要求。
④底部框架-抗震墙房屋底框部分的受力复杂。大震下过渡层砌体的破坏可能会改变底框部分的受力性能;“强柱弱梁”的破坏模式在底框部分难以实现。抗震设计时应采取措施实现底部框架-砌体结构底层合理破坏模式。
Shear-wall and bottom-frame masonry structure satisfies the requirement of large space at the bottom, and the cost is lower comparatively, this style of buildings is prevalent in small and middle cities. However, character of“upper’s stiffness is stronger than bottom, and upper’s weight is heavier than bottom”is one of characters of shear-wall and bottom-frame masonry structure, and when the bottom is damaged, progressive collapse maybe happen in the upper. During Wenchuan Earthquake, the bottom (shear-wall and bottom-frame) is severely damaged, even progressive collapse, and some of them are damaged lightly. Damaged location is also different, and is divided into two categories, such as upper structure and bottom structure. Therefore, as a whole, to understand the seismic performance of shear-wall and bottom-frame masonry structure, to analyze the main influential elements of seismic performance, to find the weak part of structure, to provide the fortification measures are significantly necessary, and the designer of shear-wall and bottom-framed masonry structure can infer from this paper.
Characteristic of seismic disaster for shear-wall and bottom-frame masonry structure is fully analyzed in this paper, based on the real damaged buildings. Using space structure elastic model, plane structure elastic and elastic-plastic model, and the real structure in Wenchuan, the contrasts between shear-wall and bottom-frame masonry structure and masonry structure are analyzed. Control index of stiffness ratio between the upper (masonry structure) and shear-wall and bottom-frame is called story stiffness ratio, the influencing extent of story stiffness ratio is systematically analyzed, by establishing space structure elastic model, plane structure elastic and elastic-plastic model.
The main conclusions of this paper are as follows:
①Seismic performance of the shear-wall and bottom-frame masonry structure after reasonable design is almost the same as that of masonry structure, and damage pattern of shear-wall and bottom-frame masonry structure (earthquake action of upper structure reduced by bottom dissipation) has a great controllability, therefore it’s significantly necessary to be strict with seismic design of shear-wall and bottom-frame masonry structure, especially in definition of stiffness ratio between bottom story and transition story, integration design of upper wall.
②It’s the key point to guarantee the seismic performance of bottom-frame masonry structure, by controlling the stiffness ratio between different story and carrying out the thought of multiple seismic-proof. The present regulations about the stiffness ratio between different story can make the seismic performance of shear-wall and bottom-frame masonry structure safe, however, crack prevention is lack; therefore, the lower limit of stiffness ratio should be modified form 1.0 to 1.5, in order to fully play the dissipation of shear-wall and bottom-frame, and to decrease the seismic effect of masonry structure on the shear-wall and bottom-frame.
③Transition story of shear-wall and bottom-frame masonry structure may be easily damaged during earthquake, because of inconsistent deformation between bottom-frame and transition story. The more stiffness ratio of the shear-wall and bottom-frame masonry structure, the worse transition story is damaged. Therefore, adopting the reinforced masonry, adding tie-column or increasing the strength of material and so on, are advised, in order to improve the ductility and shear strength of transition story, to prevent walls of transition story damaged caused by the inconsistent deformation, requirement on transition story of masonry structure is added to new code (a draft for discussing).
④Mechanical behavior of shear-wall and bottom-frame masonry structure is complex. Mechanical behavior of shear-wall and bottom-frame will be changed, after transition story damaged during great earthquake. The pattern of“strong column and weak beam”is difficultly accomplished. The reasonable damage pattern of shear-wall and bottom-frame masonry structure should be adopted during seismic design.
以汶川地震的震害资料为基础,全面系统分析了底部框架-抗震墙房屋的震害特征;采用空间结构弹性模型、平面结构弹性和弹塑性模型、汶川地震灾区实际建筑,对比分析了底部框架-抗震墙房屋和砌体结构的抗震性能;以底框上部砌体结构层与底框结构层的层刚度之比(简称层刚度比)为控制指标,建立空间结构弹性模型、平面结构弹性和弹塑性模型,系统分析了层刚度比对底部框架-抗震墙房屋的抗震性能的影响。
研究得到的主要结论有:
①经合理设计的底部框架-抗震墙房屋的抗震性能与砌体结构相当,底部框架-抗震墙房屋破坏模型(底部耗能减少上部结构地震效应)可控性更强。严格的底部框架-抗震墙房屋抗震设计十分必要,特别是结构底部层刚度比合理取值、过渡层墙肢抗震设计和上部结构整体性设计尤为重要。
②控制层刚度比和实现“多道抗震防线”的思想是保证底框结构抗震性能的关键。现行规范给出的层刚度比控制条件可以保证底部框架-抗震墙房屋抗震性能,但缺乏对结构过渡层墙肢的抗震防严重开裂设计。为了发挥底部框架-抗震墙房屋的底部耗能、减小上部砌体地震作用效应,可以适当提高层刚度比的下限值,建议由1.0提高到1.5。
③底部框架-抗震墙房屋的过渡层可能成为结构抗震不利位置。由于底层框架变形与过渡层砌体墙肢变形不协调,导致过渡层墙肢出现开裂破坏;层刚度比越大,开裂破坏越严重。建议在过渡层底部墙体中采用加筋砌体、增设构造柱或提高墙体材料强度等构造措施,提高过渡层墙肢的延性和抗剪强度,避免位移不协调引起墙肢的开裂破坏,新规范(征求意见稿)补充了过渡层砌体墙的相关要求。
④底部框架-抗震墙房屋底框部分的受力复杂。大震下过渡层砌体的破坏可能会改变底框部分的受力性能;“强柱弱梁”的破坏模式在底框部分难以实现。抗震设计时应采取措施实现底部框架-砌体结构底层合理破坏模式。
Shear-wall and bottom-frame masonry structure satisfies the requirement of large space at the bottom, and the cost is lower comparatively, this style of buildings is prevalent in small and middle cities. However, character of“upper’s stiffness is stronger than bottom, and upper’s weight is heavier than bottom”is one of characters of shear-wall and bottom-frame masonry structure, and when the bottom is damaged, progressive collapse maybe happen in the upper. During Wenchuan Earthquake, the bottom (shear-wall and bottom-frame) is severely damaged, even progressive collapse, and some of them are damaged lightly. Damaged location is also different, and is divided into two categories, such as upper structure and bottom structure. Therefore, as a whole, to understand the seismic performance of shear-wall and bottom-frame masonry structure, to analyze the main influential elements of seismic performance, to find the weak part of structure, to provide the fortification measures are significantly necessary, and the designer of shear-wall and bottom-framed masonry structure can infer from this paper.
Characteristic of seismic disaster for shear-wall and bottom-frame masonry structure is fully analyzed in this paper, based on the real damaged buildings. Using space structure elastic model, plane structure elastic and elastic-plastic model, and the real structure in Wenchuan, the contrasts between shear-wall and bottom-frame masonry structure and masonry structure are analyzed. Control index of stiffness ratio between the upper (masonry structure) and shear-wall and bottom-frame is called story stiffness ratio, the influencing extent of story stiffness ratio is systematically analyzed, by establishing space structure elastic model, plane structure elastic and elastic-plastic model.
The main conclusions of this paper are as follows:
①Seismic performance of the shear-wall and bottom-frame masonry structure after reasonable design is almost the same as that of masonry structure, and damage pattern of shear-wall and bottom-frame masonry structure (earthquake action of upper structure reduced by bottom dissipation) has a great controllability, therefore it’s significantly necessary to be strict with seismic design of shear-wall and bottom-frame masonry structure, especially in definition of stiffness ratio between bottom story and transition story, integration design of upper wall.
②It’s the key point to guarantee the seismic performance of bottom-frame masonry structure, by controlling the stiffness ratio between different story and carrying out the thought of multiple seismic-proof. The present regulations about the stiffness ratio between different story can make the seismic performance of shear-wall and bottom-frame masonry structure safe, however, crack prevention is lack; therefore, the lower limit of stiffness ratio should be modified form 1.0 to 1.5, in order to fully play the dissipation of shear-wall and bottom-frame, and to decrease the seismic effect of masonry structure on the shear-wall and bottom-frame.
③Transition story of shear-wall and bottom-frame masonry structure may be easily damaged during earthquake, because of inconsistent deformation between bottom-frame and transition story. The more stiffness ratio of the shear-wall and bottom-frame masonry structure, the worse transition story is damaged. Therefore, adopting the reinforced masonry, adding tie-column or increasing the strength of material and so on, are advised, in order to improve the ductility and shear strength of transition story, to prevent walls of transition story damaged caused by the inconsistent deformation, requirement on transition story of masonry structure is added to new code (a draft for discussing).
④Mechanical behavior of shear-wall and bottom-frame masonry structure is complex. Mechanical behavior of shear-wall and bottom-frame will be changed, after transition story damaged during great earthquake. The pattern of“strong column and weak beam”is difficultly accomplished. The reasonable damage pattern of shear-wall and bottom-frame masonry structure should be adopted during seismic design.
引文
[1] GBJ50011—2001,建筑抗震设计规范[S].
[2]李英民,刘立平.汶川地震建筑震害与思考[M].重庆:重庆大学出版社, 2008.
[3]夏敬谦,底部框剪砌体房屋抗震性能研究[J].建筑科学, 1995(2): 19-26
[4]熊立红,高连军等.底框-砌体房屋抗震性能研究[J] .沈阳建筑大学学报(自然科学版), 2008(6): 24-4.
[5]高小旺,孟俊义,廖兴祥.七层底层框架抗震墙砖房1/2比例模型抗震试验研究[J].建筑科学, 1995,4:18-23.
[6]高小旺,薄庭辉,宗志恒.带边框开竖缝钢筋混凝土低矮墙的试验研究[J].建筑科学,1995,4:24-32.
[7]高小旺,王箐,王金妹等.底层框架抗震墙砖房抗震能力的分析方法[J].建筑科学1995,4: 33-37.
[8]高小旺,何江,肖伟等.底层框架抗震墙砖房抗震设计若干问题研究[J].建筑科学,1995, 4:38-43.
[9]郑山锁,薛建阳,王斌.砌体结构抗震[M].北京:中国建材工业出版社, 2008.
[10]骆万康,刘锡军.砖砌体剪压复合受力、静力特性与抗剪强度公式[J] .重庆建筑大学学报. 2000(4).
[11]施楚贤砌体结构理论与设计[M].北京:中国建筑工业出版社, 2003.
[12]清华大学、西南交通大学、重庆大学等.汶川地震建筑震害分析与设计对策. [M].北京:中国建筑工业出版社, 2009.
[13]胡聿贤.地震工程学[M].北京:地震出版社, 2003.
[14]骆万康,王天贤.预应力抗震砖墙抗裂与承载力及其计算方法的试验研究[J] .建筑结构1995, 4.
[15]骆万康,王天贤,廖春盛,朱希诚.预应力开洞砖墙抗震性能的实验研究[J] .建筑结构1998 4.
[16] Guowei Ma, HongHao, Membe, ASCE, and YongLu, Homogenization of Masonry Using Numerical Simulations[J]. ASCE Journal of Engineering Mechanics, 2001, Vol.127, No.5, 421- 431.
[17] Anthoine,A., Derivation of the In-plane Elastic Characteristics of Masonry through Homogenization Theory[J]. International Journal of Solids and Structures,1995,Vol.32,137 163.
[18] William, K.J.and Warnke, E.D., Constitutive Model for the Triaxial Behavior of Concrete, Proceedings, International Association for Bridge and Structural Engineering[J]. ISMES,Bergamo, Italy, 1975, Vol.19,174.
[19]王珊,武建华.砖砌体的非线性计算[J].重庆建筑大学学报2001 Vol.23 10-16.
[20]江见鲸.钢筋混凝土非线性有限元分析第1版[M].陕西西安陕西科学技术出版社1994.
[21]江见鲸,贺小岗.工程结构计算机仿真分析第1版[M].北京清华大学出版社1996.
[22] Ansys公司非线性分析指南[M].
[23] Ansys公司基本过程手册[M].
[24] Ansys公司建模及分网指南[M].
[25] GBJ50010—2002,混凝土结构设计规范[S].
[26]郑山锁等.底部两层框架砖房模型的振动台试验[J].西安建筑科技大学学报, 1997, 29(2): 183~187
[27]郑山锁等.底层框架砖房模型的振动台试验[J].西安建筑科技大学学报, 1998, 30(3): 327~331.
[28]庄一舟等.底部一层框架上部无洞组合墙体受力性能的试验研究[J].建筑结构, 1998(4): 7~11.
[29]吕西林,金国芳,吴晓涵,钢筋混凝土结构非线性有限元理论与应用第1版[M]上海同济大学出版社1997.
[30] GBJ50003—2001,砌体结构设计规范[S].
[31]高小旺等.底部两层框架上部六层砖房1/3比例模型的抗震实验研究[J].建筑科学, 1994,3;12-18.
[32]高向宇,方鄂华.组合墙结构非线性分析模型[J].工程力学. 1997, 14(2):36-42.
[33]李田,吴学敏.高层及复杂多维时程分析弹塑性动态分析[J],建筑结构学报, 1992 ,13 (6):26-34.
[34]梁兴文,王庆霖.底部框架抗震墙砖房的受力性能及侧向刚度分析[J],土木工程学报, 2000, 8.
[2]李英民,刘立平.汶川地震建筑震害与思考[M].重庆:重庆大学出版社, 2008.
[3]夏敬谦,底部框剪砌体房屋抗震性能研究[J].建筑科学, 1995(2): 19-26
[4]熊立红,高连军等.底框-砌体房屋抗震性能研究[J] .沈阳建筑大学学报(自然科学版), 2008(6): 24-4.
[5]高小旺,孟俊义,廖兴祥.七层底层框架抗震墙砖房1/2比例模型抗震试验研究[J].建筑科学, 1995,4:18-23.
[6]高小旺,薄庭辉,宗志恒.带边框开竖缝钢筋混凝土低矮墙的试验研究[J].建筑科学,1995,4:24-32.
[7]高小旺,王箐,王金妹等.底层框架抗震墙砖房抗震能力的分析方法[J].建筑科学1995,4: 33-37.
[8]高小旺,何江,肖伟等.底层框架抗震墙砖房抗震设计若干问题研究[J].建筑科学,1995, 4:38-43.
[9]郑山锁,薛建阳,王斌.砌体结构抗震[M].北京:中国建材工业出版社, 2008.
[10]骆万康,刘锡军.砖砌体剪压复合受力、静力特性与抗剪强度公式[J] .重庆建筑大学学报. 2000(4).
[11]施楚贤砌体结构理论与设计[M].北京:中国建筑工业出版社, 2003.
[12]清华大学、西南交通大学、重庆大学等.汶川地震建筑震害分析与设计对策. [M].北京:中国建筑工业出版社, 2009.
[13]胡聿贤.地震工程学[M].北京:地震出版社, 2003.
[14]骆万康,王天贤.预应力抗震砖墙抗裂与承载力及其计算方法的试验研究[J] .建筑结构1995, 4.
[15]骆万康,王天贤,廖春盛,朱希诚.预应力开洞砖墙抗震性能的实验研究[J] .建筑结构1998 4.
[16] Guowei Ma, HongHao, Membe, ASCE, and YongLu, Homogenization of Masonry Using Numerical Simulations[J]. ASCE Journal of Engineering Mechanics, 2001, Vol.127, No.5, 421- 431.
[17] Anthoine,A., Derivation of the In-plane Elastic Characteristics of Masonry through Homogenization Theory[J]. International Journal of Solids and Structures,1995,Vol.32,137 163.
[18] William, K.J.and Warnke, E.D., Constitutive Model for the Triaxial Behavior of Concrete, Proceedings, International Association for Bridge and Structural Engineering[J]. ISMES,Bergamo, Italy, 1975, Vol.19,174.
[19]王珊,武建华.砖砌体的非线性计算[J].重庆建筑大学学报2001 Vol.23 10-16.
[20]江见鲸.钢筋混凝土非线性有限元分析第1版[M].陕西西安陕西科学技术出版社1994.
[21]江见鲸,贺小岗.工程结构计算机仿真分析第1版[M].北京清华大学出版社1996.
[22] Ansys公司非线性分析指南[M].
[23] Ansys公司基本过程手册[M].
[24] Ansys公司建模及分网指南[M].
[25] GBJ50010—2002,混凝土结构设计规范[S].
[26]郑山锁等.底部两层框架砖房模型的振动台试验[J].西安建筑科技大学学报, 1997, 29(2): 183~187
[27]郑山锁等.底层框架砖房模型的振动台试验[J].西安建筑科技大学学报, 1998, 30(3): 327~331.
[28]庄一舟等.底部一层框架上部无洞组合墙体受力性能的试验研究[J].建筑结构, 1998(4): 7~11.
[29]吕西林,金国芳,吴晓涵,钢筋混凝土结构非线性有限元理论与应用第1版[M]上海同济大学出版社1997.
[30] GBJ50003—2001,砌体结构设计规范[S].
[31]高小旺等.底部两层框架上部六层砖房1/3比例模型的抗震实验研究[J].建筑科学, 1994,3;12-18.
[32]高向宇,方鄂华.组合墙结构非线性分析模型[J].工程力学. 1997, 14(2):36-42.
[33]李田,吴学敏.高层及复杂多维时程分析弹塑性动态分析[J],建筑结构学报, 1992 ,13 (6):26-34.
[34]梁兴文,王庆霖.底部框架抗震墙砖房的受力性能及侧向刚度分析[J],土木工程学报, 2000, 8.