Flexural and Shear Properties of Prestressed Continuous Beams with Lightweight Concrete

对采用高性能轻质混凝土的两跨预应力混凝土连续梁的抗弯和抗剪性能进行了研究，并与普通混凝土梁进行了对比。在抗弯性能方面，(1)轻骨料混凝土梁(L梁)的刚度低于普通混凝土梁(N梁)；(2)L梁与普通混凝土梁(N梁)抗弯开裂后的弯矩重分布没有显著差异；(3)L梁的极限抗弯强度与同等混凝土抗压强度的N梁相当，可以通过极限分析进行较好的计算。(4)采用非线性分析方法可以较好地估计L梁和N梁的抗弯极限性能。对于预应力加固混凝土(PRC)梁的抗剪性能，(1)L梁的混凝土承载抗剪强度(V_C)比对照N梁平均降低约25%；(2)考虑预应力和抗剪强度折减系数的影响，可以较好地计算L梁的V_c。(3)L梁剪裂后箍筋应变实测值与JSCE规范方程中所有安全系数设定值的计算值接近，而N梁则接近安全系数1.0的计算值；(4)采用修正的压力场理论可以较好地估算L梁和N梁的抗剪性能；(5)基于非线性分析的钢筋应力和JSCE规范裂缝宽度方程可以较好地计算L梁和N梁的受弯裂缝宽度。

Flexural and shear behavior of two-span continuous prestressed concrete (PC) beams using high performance lightweight concrete was studied in comparison with that of normalweight concrete beams. Conclusions obtained from this study are summarized as follows.Regarding flexural properties, (1) rigidity of lightweight concrete beam (L beam) was lower than that of normalweight concrete beam (N beam), (2) no significant difference was found between L and N beams as to moment redistribution up to the ultimate state after flexural cracking, (3) ultimate flexural strength of L beam was almost equal to that of N beam with comparable concrete compressive strength, and those could be calculated well by the limit analysis. (4) flexural behavior of L and N beams up to the ultimate state could be estimated well by a nonlinear analysis adopted here.Regarding shear properties which were examined as to prestressed reinforces concrete (PRC) beams in this study, (1) shear strength (V_c) carried by concrete of L beam was lower by about 25% on the average than that of comparable N beam, (2) V_c of L beams could be calculated well by considering together with effect of prestress and strength reduction factor for shear, (3) measured stirrup strains after shear cracking of L beam were close to calculations obtained by setting all of safety factors in the JSCE Code equation to be specified values, while those in N beams were close to ones based on safety factors of 1.0, (4) shear behavior of both L and N beams could be estimated well by applying modified compression field theory, (5) flexural crack width of both L and N beams could be calculated well using steel stress based on nonlinear analysis and JSCE Code equation for crack width.