根据重庆范太升同志提问:“井字梁如何设计?”现作以下答复:钢筋混凝土井字梁是从钢筋混凝土双向板演变而来的一种结构形式。双向板是受弯构件,当其跨度增加时,相应板厚也随之加大。但板的下部受拉区的混凝土一般都不考虑它起作用,受拉主要靠下部钢筋承担。因此,在双向板的跨度较大时,为了减轻板的自重,我们可以把板的下部受拉区的混凝土挖掉一部分(不能全挖掉,因为那样受拉钢筋没有混凝土保护了),让受拉钢筋适当集中在几条线 According to Chongqing Fan Taisheng’s question: “How do we design the well beam?” The following reply is given: The reinforced concrete box beam is a structural form evolved from the reinforced concrete two-way slab. The two-way board is a bent member. When its span increases, the corresponding board thickness also increases. However, the concrete of the lower tension zone of the slab generally does not consider it to work, and the tension is mainly borne by the lower steel bar. Therefore, when the span of the two-way board is large, in order to reduce the board’s own weight, we can dig out part of the concrete of the lower tension area of ​​the board (it cannot be completely excavated because the reinforced steel is not protected by the concrete). Pull rebar properly centered on a few lines