DBJ/T 15-92—2021《高层建筑混凝土结构技术规程》的修订依据及相关问题说明

Basis and background of revision of DBJ/T 15-92—2021 “Technical specification for concrete structures of tall buildings”

介绍了广东省标准DBJ/T 15-92—2021《高层建筑混凝土结构技术规程》的修订背景、原则和依据,并对相关概念予以说明。采用"二阶段、二水准"的性能设计方法,承载力计算式按抗力大于设防烈度地震效应组合表达,以可计算验证的方式保证"中震可修"目标的实现;采用改进后的抗震设计谱,避免了原《规程》抗震设计谱长周期段的缺陷;论证了结构最大层间位移角与混凝土构件是否开裂无关,指出控制层间位移角的主要目的在于避免非结构构件因主体结构过大的变形而损坏,合理放宽层间位移角限值;轴压比不应作为柱安全度的指标,将轴压比作为竖向荷载作用下的混凝土允许压应力比,可避免长期荷载作用下框架边柱的压应力小、中柱的压应力大而引起的徐变变形差,也可避免某些柱截面偏大成为短柱而又需构造配筋,延性反而变差;规定全框支剪力墙结构设计原则及构造要求,要求上部剪力墙先于下部框架屈服,不控制上下层刚度比;规定重力柱-核心筒结构的设计原则,要求核心筒有能力承担全部地震剪力、确保楼盖面内的弯、剪承载力;解释了美国规范UBC中区分规则和不规则结构的主要目的,指出扭转位移比不是衡量结构扭转效应大小的指标;有必要总结经验,清理不正确、过时的抗震设计概念,避免或减少不必要的超限审查,为结构设计及其创新营造更好的环境。

The background, principle and basis of the recently revised Guangdong provincial standard DBJ/T 15-92—2021 "Technical specification for concrete structures of tall buildings" were introduced. The performance design method of "two stages and two levels" was adopted. The bearing capacity calculation formula was expressed as the resistance greater than the combination of the actions under fortification intensity earthquake to ensure the realization of "moderate earthquake repairable". The improved seismic design spectrum was adopted to avoid the defects of the part of long period in the original code. It is proved that the maximum inter-story drift of the structure is not related to the cracking of concrete members. It is pointed out that the main purpose of controlling the drift is to avoid the damage of non-structural members due to excessive deformation of the main structure and the limit value of inter-story drift is reasonably relaxed. The axial compression ratio is not the index of column safety. Taking the axial compression ratio as the allowable compressive stress ratio of the concrete under the vertical load, which can aviod the difference of creep deformation caused by the small compressive stress of side column and the large compressive stress of middle column under long-term load. It can also avoid the ductility deterioration caused by the large section of some columns becoming short columns with few reinforcements. The design principles and structural requirements of the fully frame-supported shear wall structure were specified. The upper shear wall has to yield before the lower frame. There is no need to control the ratio of the upper floor stiffness to lower floor stiffness. The proposed design principles of gravity column-core tube structure require the core tube to be able to bear all seismic shear and ensure the floor to be able to bear in-plane bending and shear. The main purpose of UBC code to distinguish regular and irregular structures was explained. It is pointed out that the torsion displacement ratio is not an index to measure the torsion effect of structures. It is necessary to summarize experiences and clean up incorrect and outdated seismic design concepts to avoid or reduce unnecessary over limit review, and create a better environment for structural design and innovation.