普通砼空心板在设计荷载作用下,总是带着裂缝工作的。裂缝的出现直接影响板的刚度,同时还会影响板的耐久性,这是普通砼空心板的最大弱点,预应力砼多孔板是在受拉区预先加一个压力,以推迟板因受力而开裂的时间,使板在使用阶段不出现裂缝,这就克服了普通砼空心板的弱点。因此,预应力砼多孔板的抗裂性能比普通砼空心板的抗裂性能好。预应力砼多孔板在受拉区加一个压力是通过预应力筋放张时实现的。由于多孔板在板底布置纵向主筋,在板面布置2根副筋,甚至不布置副筋。当钢筋放张时,板底砼压缩变形大,板面砼压缩变形。形成多孔板有向上拱起现象,叫做预应力砼多孔板的反拱。反拱值 Ordinary concrete hollow slabs always work with cracks under the design load. The appearance of cracks directly affects the stiffness of the board, and it also affects the durability of the board. This is the biggest weakness of ordinary hollow board. The prestressed diaphragm board is pre-stressed in the tension area to delay the board from being stressed. The time of cracking does not cause cracks in the board during use, which overcomes the weakness of ordinary hollow board. Therefore, the anti-crack performance of the pre-stressed crucible plate is better than that of the ordinary crucible hollow plate. The prestressed concrete multi-hole plate plus a pressure in the tension zone is achieved when the prestressed tendons are stretched. Since the perforated plate is provided with a longitudinal main bar at the bottom of the plate, two secondary reinforcements are arranged on the plate surface, and no secondary reinforcement is even arranged. When the rebar is stretched, the bottom sill compressively deforms and the plate sill compresses and deforms. The formation of a porous plate has a phenomenon of arching upwards, which is called pre-stressing and inversion of the porous plate. Inverted value