超低温下有黏结预应力混凝土梁受弯性能试验研究

Experimental study on flexural properties of bonded prestressed concrete beams under cryogenic temperatures

为确保预应力混凝土结构在超低温下的安全使用,借助超低温冷库和自制保温-加载装置,在不同温度点(20℃、-40℃、-70℃、-100℃)下对不同张拉控制应力(0fptk、0.75fptk)的12根有黏结预应力混凝土梁的受弯性能进行了试验研究。试验结果表明:有黏结预应力混凝土梁在超低温下仍能较好地符合平截面假定;在试件开裂前,梁的刚度受温度和预应力度的影响较小,而试件开裂后,梁的刚度随温度的降低而提高;低温下,预应力仍能有效提高构件的抗裂度和抗弯刚度;随着温度的降低,试件开裂荷载呈直线上升,试件的极限承载力呈加速上升,但其提高程度小于开裂荷载,试件开裂荷载与极限荷载的比值增大,变形性能降低;考虑材料低温效应后,代入规范公式得到的极限承载力是可靠的,而开裂荷载计算值较实测值大,仍需进行进一步研究。

To promote the safe application of prestressed concrete structures under cryogenic temperatures, experiments were carried out on 12 bonded prestressed concrete beams by cryogenic cold storage and homemade insulation-loading equipments, in which flexural properties with different tension control stresses （ 0fptk and 0.75fptk ） at 20℃, - 40℃, -70℃ and -100℃ were analyzed respectively. The results indicate that the plane-section assumption of bonded prestressed concrete beams can still be obeyed under cryogenic temperatures. Temperature and prestress have little effect on the stiffness of specimens before cracking, however the stiffness of the specimens increases as temperature drops after carcking. Prestressing can effectively delay the appearance of cracks, limit the crack width and decrease the deformation of specimens under cryogenic temperatures. When the temperature decreases, both the ultimate load and the cracking load increase, but the cracking load has a faster rate. The ratio of the cracking load to the ultimate load increases, which means that the deformation performance of specimens decrease. Considering the temperature effect of the materials, the theoretical value of ultimate bearing capacity calculated by Chinese code formula is reliable, whereas the theoretical value of cracking load is larger than the measured one, so further research should be conducted.