扩展基础冲剪破坏特征和计算方法研究

发布时间：2018-05-16 15:13

本文选题：扩展基础 + 冲切　；参考：《中国建筑科学研究院》2013年博士论文

【摘要】：扩展基础的冲剪计算是建筑基础设计一个重要环节,本文总结了国内外关于冲剪问题的研究现状和设计方法,并针对ACI318、EN1992、GB50007的计算方法进行了算例对比分析,提出了需要进一步研究的问题。本课题研究的主要内容包括扩展基础的冲剪破坏特征；基础平面尺寸、基础配筋率以及偏心荷载对基础冲剪承载力的影响等。本次试验共设计了16个基础模型,得到了扩展基础的冲切剪切破坏特征,对各影响因素进行了分析,提出了基于计算截面在距柱边ho/2处的剪切计算方法的建议,为扩展基础的冲剪设计和规范修订提供依据和参考。论文工作的主要研究成果如下： (1)通过试验得到了扩展基础的冲剪破坏特征,验证了当基础宽度大于柱宽加两倍基础有效高度时,将发生冲切破坏；当基础宽度小于或等于柱宽加两倍基础有效高度时,若不配置抗剪钢筋,基础将发生剪切破坏；当配置抗剪钢筋时,基础将发生弯曲破坏。 (2)对于剪切破坏型的扩展基础,在中心荷载作用下其剪切破坏角约为55°,在偏心荷载作用下,偏心一侧的剪切破坏角约为60°,另一侧的破坏角约为50°；对于冲切破坏型的扩展基础,在中心荷载作用下冲切破坏角约为51°；在偏心荷载作用下,冲切破坏角分别为60°和48°左右。偏心荷载作用下,偏心方向一侧剪切破坏角大于中心荷载作用下的剪切破坏角。 (3)在本次试验条件下,剪切型基础混凝土发挥的抗剪强度在0.98MPa-1.45MPa范围内,即在0.59ft-0.8ft之间；冲切型基础混凝土发挥的抗剪强度在1.27MPa-2.09MPa范围内,即在0.75ft～1.31ft之间。剪切型基础混凝土抗剪强度的发挥程度低于冲切型基础混凝士抗剪强度的发挥程度。 (4)纵筋配筋率可以提高基础抗冲剪承载力,基于本次试验条件,平均提高约15%～20%左右。 (5)分析了基础板平面尺寸对基础抗冲剪承载力的影响,提出了考虑基础边长比影响的冲切承载力半经验公式；提出了计算截面在距柱边ho/2处的剪切验算建议方法。 (6)试验结果表明,将圆柱基础代换为方柱基础进行冲切验算时,若按等剪切面积换算,其冲切承载力基本接近；若按柱等面积换算,圆柱基础用方柱基础代替设计时偏于安全。综合上述研究成果,本文的主要创新点如下 (1)通过试验得到了扩展基础的冲剪破坏特征,验证J’当基础宽度小于或等于柱宽加两倍基础有效高度时,基础将发生剪切破坏,当基础宽度大于柱宽加两倍基础有效高度时,将发生冲切破坏。 (2)偏心荷载作用下,偏心方向一侧剪切破坏角大于中心荷载作用下的剪切破坏角。 (3)基于本次试验条件,剪切型基础的混凝土抗剪强度在0.98MPa～1.45MPa范围内,即在0.59ft～0.88ft之间；冲切型基础的混凝土抗冲切强度在1.27MPa～2.09MPa范围内,即在0.75ft1.31ft之间；剪切型基础混凝土抗剪强度的发挥程度低于冲切型基础混凝土抗剪强度的发挥程度。 (4)分析了基础板平面尺寸对基础抗冲剪承载力的影响,提出了考虑基础边长比影响的冲切计算半经验公式,提出了基于计算截面在距柱边h0/2处的剪切验算方法的建议。
[Abstract]:The expansion foundation punching shear calculation is an important link in the building foundation design. In this paper, the research status and design methods about the problem of punching shear at home and abroad are summarized, and the calculation methods of ACI318, EN1992 and GB50007 are compared and analyzed, and the further research problems are put forward. The main contents of this research include the extension base. The basic plane size, the foundation reinforcement ratio and the influence of the eccentric load on the bearing capacity of the basic punching shear, and so on. 16 basic models are designed in this test, and the characteristics of the punching shear failure are obtained. The influence factors are analyzed and the shear gauge based on the calculation section at the edge of the column at ho/2 is put forward. The proposed method provides a basis and reference for extending the design of foundation punching shear and regulating the revision.
The main research results of the paper work are as follows:
(1) the failure characteristics of the punching shear are obtained through the experiment. It is verified that when the base width is greater than the column width plus two times the base effective height, the punching shear failure will occur. When the base width is less than or equal to the column width plus two times the base effective height, the shear failure will occur if the shear reinforcement is not configured, and when the shear bar is configured, the base will be broken. The foundation will be bent and damaged.
(2) for the expansion foundation of shear failure type, the shear failure angle is about 55 degrees under the central load. Under eccentric load, the shear failure angle of the eccentric side is about 60 degrees and the other side is about 50 degrees. For the expansion foundation of the punching shear failure type, the punching cutting angle is about 51 degrees under the central load, and the eccentric load is in the eccentric load. Under the action of the eccentric load, the shear failure angle on the side of the eccentric load is greater than that under the central load.
(3) under the conditions of this test, the shear strength of the shear type foundation concrete is within the range of 0.98MPa-1.45MPa, that is, between 0.59ft-0.8ft, and the shear strength of the punching shear foundation concrete is within the range of 1.27MPa-2.09MPa, that is, between 0.75ft and 1.31ft. The shear strength of the shear base concrete is lower than that of the scissors foundation. The exertion of the shear strength of the basic coagulant.
(4) longitudinal reinforcement ratio can increase the resistance to punching shear capacity of the foundation. Based on the test conditions, the average increase is about 15% ~ 20%.
(5) the influence of the plane size of the base plate on the bearing capacity of the foundation resistance is analyzed, and the semi empirical formula of the punching shear bearing capacity considering the influence of the base length ratio is put forward, and a method for calculating the calculation of the shear calculation of the section at the ho/2 edge of the column is put forward.
(6) the experimental results show that when the cylindrical foundation is replaced by a square column foundation for punching and cutting checking, the bearing capacity of the punching shear is basically close to the equivalent shear area. If the column base area is converted, the cylindrical foundation is safer than the design of the square column foundation.
Based on the above research results, the main innovations of this paper are as follows.
(1) the failure characteristics of the punching shear are obtained through the experiment. It is proved that when the base width is less than or equal to the column width plus two times the base effective height, the shear failure will occur in the foundation. The punching failure will occur when the base width is greater than the column width plus two times the base effective height.
(2) under eccentric load, the shear failure angle of the eccentric direction is larger than that of the central load.
(3) based on the test conditions, the shear strength of the concrete shear foundation is within the range of 0.98MPa to 1.45MPa, that is between 0.59ft to 0.88ft, and the concrete punching shear strength of the punching shear foundation is within the range of 1.27MPa to 2.09MPa, that is, between 0.75ft1.31ft, and the shear strength of the shear type foundation is lower than that of the punching shear foundation. The exertion of the shear strength of concrete.
(4) the influence of the plane size of the base plate on the bearing capacity of the foundation resistance is analyzed, and a semi empirical formula for the calculation of the scouring and cutting calculation considering the influence of the base length ratio is put forward, and a proposal for the calculation of the shear calculation based on the calculation section at the edge of the column h0/2 is put forward.

【学位授予单位】：中国建筑科学研究院
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU470

【共引文献】