混凝土框架梁简支弯矩算法研究

Research on simply supported bending moment of RC frame beams

根据《高层建筑混凝土结构技术规程》(JGJ 3—2010)第5.2.3条的规定,在竖向荷载作用下,可对梁端负弯矩乘以调幅系数进行调整,且框架梁跨中截面正弯矩设计值不应小于竖向荷载下按简支梁计算的跨中弯矩设计值的50%。从而高层建筑混凝土结构的框架梁简支弯矩成为截面设计的一项必要参数,由于结构整体计算时框架梁一般为两端刚接,如何计算其简支弯矩是一个值得研究的问题。按照传统方法,该弯矩由结构力学方法计算,忽略其与其他构件的连接关系,依据梁上荷载分布情况,通过简单计算即可获得其弯矩图,导致次梁上的荷载无法传递到框架梁,从而引起计算结果失真。本文提出了一种新的框架梁简支弯矩算法,该方法保持主次梁连接关系不变,采用有限元方法直接进行计算,可准确考虑构件连接关系的影响,确保框架梁简支弯矩的计算符合实际受力情况,并具有较高的计算效率。目前,该方法已集成到北京市建筑设计研究院有限公司自主研发的结构设计软件Paco中,取得了良好的应用效果。

According to Technical specification for concrete structures of tall building( JGJ 3—2010) Article 5. 2. 3,under vertical load,the negative moment of the beam can bereduced by the amplitude modulation coefficient,and the crosssection design bending moment of the frame beam shall not be less than 50% of the design bending moment calculated by the simply supported beam under the vertical load. Therefore,the simply supported moment of the frame beam of the highrise building has become a necessary parameter for the cross-section design. It is a question worthwhile to study how to calculate the simply-supported moment of the frame beam. In traditional,the bending moment is calculated by the structural mechanics method. This method assumes that both ends of the frame beam are simply supported and the connection with other components is ignored,which means sometimes the load on the secondary beam can not be transmitted to the frame beam,causing the calculation results to be distorted. A new algorithm of simply supported bending moment of frame beams was proposed,in which the finite element method is used to calculate directly. This method can accurately consider the influence of component connection relation,and ensure that the calculation of the simply supported moment of frame beam is in accordance with the actual force and has high computational efficiency. At present,the proposed method has been implemented completely in Paco,a software for structure design developed by Beijing Institute of Architectural Design independently,and satisfied effect has been achieved.