钢筋混凝土短梁内藏“拉杆-拱”体系研究

Research on Hidden Tie-Bar Arch System of RC Short Beam

钢筋混凝土短梁属于深受弯构件,应力场复杂,当前的设计方法存在一定的局限性。本文通过有限元分析对钢筋混凝土短梁与相应的钢筋拉杆-混凝土拱进行了系列仿真试验,对比分析了短梁和拉杆-拱的极限承载力、应力分布、跨中挠度和裂缝形态等力学指标。结果表明:当两种构件尺寸、荷载及其他配筋条件基本相当时,拉杆-拱的极限承载力仅比短梁小8.2%,跨中挠度也仅比短梁大9.8%,且拉杆-拱拱圈中混凝土应力分布较短梁均匀,而它们底部主要纵筋的应力水平基本相当,短梁的裂缝以斜裂缝为主,分布范围较拉杆-拱大。这些结果反映出钢筋混凝土短梁中内藏"拉杆-拱"体系作为其核心受力骨架,是日后工程中钢筋混凝土短梁设计的重点关注部分。

As a type of deep flexural members,reinforced concrete(RC)short beams have a complex stress distribution,and the current design methods have some limitations. In this paper,a series of simulation experiments on RC short beams and corresponding RC tie-bar arch are carried out by finite element analysis.Their mechanical properties are compared and analyzed,such as bearing capacity,stress distribution,midspan deflection and crack forms.When the RC short beams and corresponding RC tie-bar arch were designed with basically equivalent dimensions,loads and other reinforcement conditions,the results show that the ultimate bearing capacity of tie-bar arch is only 9.8% lower than that of short beam,as well as its midspan deflection is only 8.2% larger than that of short beam.Besides,the stress distribution of concrete in tie-bar arch is more uniform than that of short beam,meanwhile,their stress of main reinforcements at beam bottom area are almost the same.In addition,the distribution range of cracks in short beam is larger than that of tie-bar arch and they are mainly inclined.All the above results show that the hidden tie-bar arch system in RC short beams is the core force skeleton,which should be focused in the future designs of RC short beams.