L型RC框架结构抗震薄弱环节初步研究

发布时间：2018-08-11 10:31

【摘要】：RC框架结构在我国应用广泛。框架结构可通过对各榀框架的合理布置获取较大的建筑使用空间以及灵活的空间安排,故被广泛的应用于教学楼、医院、商场等建筑。其中,教学楼是教书育人的场所,其人员密集,且教学楼内绝大部分为自救自助能力较差的青少年学生;再者教学楼也常作为抗震救灾的应急避灾场所,一旦在地震中发生严重损坏,势必会造成大量的人员伤亡也会在一定程度上影响抗震救灾工作的有效进行,可能会造成更大的损失。矛盾的是,框架结构容易发生应力集中、侧向刚度小、承载力相对较低等缺点,又使框架结构成了在地震灾害中受损较为严重的建筑类型之一。由于人类对建筑物美观和艺术欣赏的需要,以及建筑场地条件的限制、建筑使用功能的要求等现实条件的限制,在实际使用中会出现一些平面布置不规则的建筑。而此类建筑不规则的特性,会使其刚度中心和质心偏离较大、受力情况更加复杂,在地震作用下,会出现更大的扭转效应和更多的应力集中效应,更容易造成局部或者整体倒塌等严重破坏。本文提出了使用有限元非线性时程分析来进行研究的方法来分析平面布置不规则框架结构教学楼的抗震性能和扭转效应以及找出此类结构的抗震薄弱环节,即:本文从实际出发,以芦山中学教学楼为原型,设置六栋不同的L型平面布置的框架结构教学楼,并通过最不利地震的方法和实际验算比较选取使结构扭转效应最大的地震动记录,最终选取于1949年,在Olympia Hwy Test Lab观测站点记录的Western Washington地震动作为输入地震动,且输入方式为356分量沿模型X轴方向输入,86分量沿模型Z轴方向输入。将该地震动调幅至多遇地震、设计地震、罕遇地震、超罕遇地震所对应的PGA输入6个工况模型进行时程分析,并以结构的层扭转角的大小表示结构的扭转效应的强弱,以结构的层间位移角表示结构整体变形的大小,以各框架柱混凝土的压损伤值表达各框架柱的破坏情况。通过使用本文中的研究方法进行计算和分析,得出以下结论:1.本文选取地震动时,通过将一条地震动水平两个分量交换输入结构的水平两个垂直方向,得到的结构的层扭转角各不相同,证明对同一条地震动记录,其水平分量的输入方式不同,对结构的影响也不同,故在抗震研究以及结构设计中使用时程分析法进行补充验算、抗震复核时,选取地震动过程中应当考虑地震动输入的方向性。2.证实了对于L型平面布置不规则的RC框架结构,其偏心程度越大,则结构的扭转效应越强,且整体的破坏也越严重。并且,本文得到了L型RC框架结构的整体变形与扭转效应的关系符合三次函数。3.在地震作用下,L型框架结构教学楼的薄弱部位是长边方向的边榀框架的柱和外侧拐角处及附近的柱;通过对比分析,得出了调整L型框架结构薄弱部位分布和降低此类结构扭转效应的方法,即:可以通过适当的改变某些柱的截面尺寸的方法来调整受损框架柱的分布。若是增大短边方向边榀框架柱的截面尺寸,则在超罕遇地震下结构的扭转效应会增大30%以上,最危险柱的损伤会增大10%左右。若是增大长边方向的边榀框架柱的截面尺寸,则在超罕遇地震下结构的扭转效应能降低18%左右,最危险柱的损伤会降低20%左右;且增大长边方向的边榀框架柱的截面尺寸可以使受损的框架柱分布更为均匀,即可证明此方法可以使整个结构的损伤分布更加均匀,也就是说能使整个结构的承载部位分布更加均匀,可以避免薄弱部位的出现,从而降低结构局部倒塌的风险。
[Abstract]:RC frame structure is widely used in our country. Frame structure can obtain large space for building and flexible space arrangement by reasonable arrangement of each frame, so it is widely used in teaching buildings, hospitals, shopping malls and other buildings. Young students with poor self-help ability; moreover, teaching buildings are often used as emergency shelters for earthquake relief. Once serious damage occurs in the earthquake, it is bound to cause a large number of casualties and to a certain extent affect the effective conduct of earthquake relief work, may cause greater losses. Because of stress concentration, small lateral stiffness and relatively low bearing capacity, the frame structure has become one of the most seriously damaged building types in earthquake disasters. Some buildings with irregular plane layout will appear in use. However, the irregular characteristics of such buildings will make their stiffness center and center of mass deviate greatly, and the stress situation is more complicated. Under the earthquake action, there will be greater torsion effect and more stress concentration effect, which is easier to cause local or overall collapse and other serious damage. In this paper, the method of finite element nonlinear time history analysis is proposed to analyze the seismic performance and torsion effect of irregular planar frame structure teaching building and find out the weak links of this kind of structure. Finally, the Western Washington ground motion recorded at the Olympia Hwy Test Lab observation station in 1949 was selected as the input ground motion, and the input mode was 356 components along the X-axis direction of the model, 86 points. The amplitude of the ground motion is modulated to the Z-axis direction of the model. The PGA corresponding to the most frequent earthquakes, the design earthquakes, the rare earthquakes and the ultra-rare earthquakes is input into six working conditions for time history analysis. The torsion effect of the structure is expressed by the magnitude of the torsion angle of the story, and the overall deformation of the structure is expressed by the displacement angle of the story. The damage of each frame column is expressed by the compressive damage value of the concrete of each frame column. Through the calculation and analysis of the research method in this paper, the following conclusions are drawn: 1. In this paper, the story torsion angles of the structure are obtained by exchanging the horizontal two components of a ground motion into the horizontal two vertical directions of the structure. It is proved that the input mode of the horizontal component of the same seismic record is different, and the influence on the structure is also different. Therefore, in seismic research and structural design, the time history analysis method is used to supplement the calculation. In seismic review, the directionality of the input of the ground motion should be considered. The greater the eccentricity of the irregular RC frame structure, the stronger the torsional effect and the more serious the overall failure of the structure. Furthermore, the relationship between the overall deformation and torsional effect of the L-shaped RC frame structure is found to be a cubic function. The column of the frame, the column at the corner of the frame and the nearby column are compared and analyzed, and the method of adjusting the distribution of the weak part and reducing the torsional effect of the structure is obtained. The torsional effect of the structure will increase by more than 30% and the damage of the most dangerous columns will increase by about 10% under rare earthquakes. The cross-sectional dimension of the damaged columns can make the damage distribution more uniform, which proves that this method can make the damage distribution of the whole structure more uniform, that is to say, can make the load-bearing parts of the whole structure more uniform, can avoid the occurrence of weak parts, and reduce the risk of local collapse of the structure.
【学位授予单位】：中国地震局工程力学研究所
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU352.11;TU375.4

【参考文献】