楼板对钢筋混凝土框架结构“强梁弱柱”式破坏的影响分析

发布时间：2018-05-15 05:22

本文选题：强梁弱柱 + 楼板　；参考：《中国地震局工程力学研究所》2015年硕士论文

【摘要】：在汶川地震和玉树地震中,很多按现行规范设计的钢筋混凝土框架结构出现了结构抗震设计中极力避免的“强梁弱柱”式破坏,而不是预期的“强柱弱梁”延性破坏机制。这种震害现象引起了研究人员的高度关注,并开展了相关研究。本文在系统总结国内外相关研究的基础上,主要从结构和构件耗能、构件利用率与层间位移角三个角度,就楼板对“强梁弱柱”式破坏的影响进行了研究,主要工作如下:1.对比评述了各国规范对“强柱弱梁”的相关规定。各国规范对于“强柱弱梁”的设计思想都是采用增大柱端弯矩的方法。区别在于计算梁端设计弯矩时,对楼板的考虑:一种是按梁原截面计算梁端设计弯矩,通过提高柱端弯矩增大系数的取值,间接考虑楼板影响;另一种是将楼板对梁的加强作用折算成一定范围内的板,参与梁受弯,按T型截面计算梁端设计弯矩。2.研究在不同强度水平地震动作用下,楼板对RC框架结构地震反应的影响。通过将梁和楼板的共同作用简化为不同有效翼缘宽度的T型梁,建立四个分析模型,并对其进行非线性地震反应分析。从结构和构件耗能、构件利用率和层间位移角三个角度的对比分析,发现:1)当地震动强度不大于原结构设防烈度的罕遇地震时,由于楼板对梁的加强作用,随着T型梁有效翼缘宽度的增加,梁中的非弹性耗能减少,而柱的非弹性耗能并未增加;框架结构中的主要受力构件(框架梁和框架柱)的利用率总体在降低;层间位移角减小。2)当地震动强度大于原结构设防烈度的罕遇地震时,由于楼板对梁的加强作用,随着T型梁有效翼缘宽度的增加,梁中的非弹性耗能减少,底层框架柱非弹性耗能增加;总体上梁的利用率降低,柱的利用率提高,特别是底层柱;底层层间位移角增大;结构发生“强梁弱柱”式破坏的可能性增大。3.以汶川地震中倒塌的漩口中学前教学楼作为原型,建立三个分析模型:裸框架模型,按美国ACI规范和新西兰NZS3101规范分别计算T型梁有效翼缘宽度的模型。进一步研究T梁有效翼缘宽度取值对钢筋混凝土框架结构“强梁弱柱”式破坏的影响。通过对比梁抗弯承载力,发现楼板能显著提高梁端负弯矩承载力并影响“强梁弱柱”机制的形成。通过对比结构和构件耗能、构件利用率和结构层间位移,得出楼板提高了梁的刚度和强度,降低了梁的耗能能力,而使底层柱在强地震动下的非弹性耗能、利用率增大,底层的层间最大位移角增大,使底层优先形成薄弱层,增大了结构倒塌的风险,提高了结构发生“强梁弱柱”式破坏的可能性。
[Abstract]:During the Wenchuan earthquake and the Yushu earthquake, many reinforced concrete frame structures designed according to the current codes have the "strong beam weak column" failure, which is avoided in the seismic design of the structure, rather than the expected ductile failure mechanism of "strong column weak beam". This kind of earthquake damage phenomenon has aroused the researchers' high attention, and has carried out the related research. On the basis of systematically summarizing the related research at home and abroad, this paper mainly studies the influence of floor slab on the failure of "strong beam and weak column" from three angles of structure and component energy dissipation, member utilization ratio and interstory displacement angle. The main work is as follows: 1. The relative regulations of national codes for strong columns and weak beams are compared and reviewed. The design idea of "strong column and weak beam" in national codes is to increase the bending moment at the end of column. The difference lies in the consideration of floor slab when calculating the design moment of beam end: one is to calculate the design moment of beam end according to the original section of beam, and indirectly consider the influence of floor slab by increasing the value of increasing coefficient of bending moment at the end of column; The other is to convert the strengthening effect of floor slab to the beam in a certain range, participate in the bending of the beam, and calculate the design moment of the beam end according to the T-section. The effect of floor slab on seismic response of RC frame structure under different intensity ground motion is studied. By simplifying the joint action of beam and floor into T-shaped beams with different effective flange widths, four analytical models are established and their nonlinear seismic responses are analyzed. From the comparative analysis of structure and component energy consumption, member utilization ratio and interstory displacement angle, it is found that when the local vibration intensity is not greater than that of the original structural fortification intensity, when the earthquake occurs, because of the strengthening effect of the floor on the beam, With the increase of the effective flange width of T-beam, the inelastic energy dissipation in the beam decreases, but the inelastic energy dissipation of the column does not increase. When the local vibration intensity is greater than the intensity of the original structure, the inelastic energy consumption in the beam decreases with the increase of the effective flange width of the T-beam due to the strengthening effect of the floor slab on the beam when the local vibration intensity is greater than that of the original structure. The inelastic energy dissipation of the bottom frame column increases; the utilization ratio of the overall upper beam decreases, the utilization ratio of the column increases, especially the bottom column; the displacement angle between the bottom layers increases; and the possibility of "strong beam weak column" failure of the structure increases. Taking the Waikou middle school front teaching building collapsed in Wenchuan earthquake as the prototype, three analysis models are established: the bare frame model, and the effective flange width model of T-beam calculated according to the ACI code of USA and the NZS3101 code of New Zealand. The influence of effective flange width of T beam on the failure of reinforced concrete frame structure with "strong beam and weak column" is further studied. By comparing the bending bearing capacity of beams, it is found that floor slab can significantly increase the bearing capacity of negative bending moment at the end of beam and influence the formation of "strong beam and weak column" mechanism. By comparing the energy consumption of the structure and the members, the utilization ratio of the members and the displacement between the structures, it is concluded that the floor slab improves the stiffness and strength of the beam, reduces the energy dissipation capacity of the beam, and makes the inelastic energy dissipation of the bottom column under strong ground motion increase. With the increase of the maximum displacement angle of the bottom layer, the weak layer is formed first, the risk of structural collapse is increased, and the possibility of "strong beam and weak column" failure of the structure is increased.
【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】：2015
【分类号】：TU375.4

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