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本文探讨矩形和T形截面素混凝土梁受纯扭时,混凝土立方强度f_(cu)和开裂扭矩Tcr之间关系。并提出相应的计算开裂扭矩的公式。通过试验研究表明:在纯扭时,强度较低的素混凝土梁比强度较高的梁具有较好的塑性。 根据塑性理论,开裂扭矩系数为k=Tcr/f_tW_T。T形截面梁的k值比矩形截面梁高。在梁腹宽度b,梁高h和翼缘宽度b_f′相同条件下,T形截面的k值随着翼缘高度h_f′的减少而增加。矩形梁的开裂扭矩Tcr=1.1(1-f_(cu)/1370)f_tW_T; T形梁的Tcr=1.2(1-f_(cu)/1490)f_tW_T。其中f_t为混凝土的抗拉强度,W_T为截面抗扭塑性抵抗矩。
This paper discusses the relationship between concrete cubic strength f_(cu) and cracking torque Tcr when plain and T-section concrete beams are subjected to pure torsion. And formulate the corresponding formula for calculating the cracking torque. Through experimental research, it is shown that the plain concrete beam with lower strength has better plasticity than the beam with higher strength in pure torsion. According to plasticity theory, the cracking torque coefficient is k=Tcr/f_tW_T. The k-value of a T-section beam is higher than that of a rectangular section beam. Under the same conditions of beam width b, beam height h and flange width b_f′, the k-value of the T-section increases with decreasing flange height h_f′. Rectangular beam cracking torque Tcr = 1.1 (1-f_ (cu) / 1370) f_tW_T; T-beam beam Tcr = 1.2 (1-f_ (cu) / 1490) f_tW_T. Where f_t is the tensile strength of the concrete and W_T is the torque resistance of the section.