通常钢筋混凝土截面应力计算都考虑混凝土开裂,不计混凝土受拉区面积,使钢筋强度能充分发挥,仅对裂缝的宽度作一定限制,以免因裂缝过大,钢筋遭大气和水的影响而锈蚀。从理论上和规范的规定来看,钢筋混凝土构件的微细开裂应属正常现象,因此结构内力计算中考虑开裂的影响是必要的。由于裂缝的存在,必然影响杆件的刚度,杆件刚度的变化对静不 Usually, the stress calculation of reinforced concrete cross section should take into account the concrete cracking, regardless of the concrete tensile area, so that the strength of the steel can be fully exerted, only the width of the crack is limited, so as not to be too cracked, steel is corroded by the atmosphere and water. According to the theory and normative rules, the fine cracking of reinforced concrete members should be a normal phenomenon, so it is necessary to consider the influence of cracking in the calculation of internal forces of structures. Due to the existence of cracks, will inevitably affect the stiffness of the rod, rod stiffness changes on the static does not