Flexural and Shear Properties of Prestressed Continuous Beams with Lightweight Concrete

研究了采用高性能轻集料混凝土的两跨预应力混凝土连续梁的抗弯和抗剪性能，并与普通混凝土梁进行了对比。本研究的主要结论如下：（1）轻质混凝土梁（L梁）的抗弯刚度低于普通混凝土梁（N梁）;（2）在受弯开裂后，直到极限状态的弯矩重分布方面，L梁和N梁没有显著差异;（3）在混凝土抗压强度相当的情况下，L形梁的极限抗弯强度与N形梁的极限抗弯强度基本相当，可以用极限分析法进行计算。(4)本文采用非线性分析方法对预应力混凝土梁的抗剪性能进行了研究，结果表明：（1）预应力混凝土梁的混凝土抗剪强度（Vc）比同类型的预应力混凝土梁平均低25%左右;（2）综合考虑预应力和强度折减系数的影响，可以较好地计算L梁的V_c;（3）L梁剪切开裂后的实测应变与JSCE规范公式中的安全系数均取规定值计算的结果接近，而N梁的抗剪性能与安全系数为1.0时的抗剪性能接近。（4）修正的压缩场理论可以很好地估计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规范的裂缝宽度计算公式，可以较好地计算L梁和N梁的弯曲裂缝宽度。

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.