预制钢筋混凝上楼面和屋面常出现裂缝.产生的原因是:一、设计方面1预制板厚度薄,预应力短短向板,跨度4.20米以内的,厚度过去多为120毫米,后,有的改为13 0毫米者,非预应力板过去、为130毫米,现有的改为150毫米,标准图一般均未注明变形限值,刚度小,弹性变形大。 Prefabricated reinforced concrete often appears cracks on floors and roofs. The reasons are: First, the design of a prefabricated panel thickness is thin, short-term prestressed board, span less than 4.20 meters, the thickness of the past more than 120 mm, after, Some were changed to 130 mm, non-prestressed plates used to be 130 mm, and existing ones were changed to 150 mm. Standard drawings generally do not indicate deformation limits, and have small stiffness and large elastic deformation.