预应力腹板开洞组合梁受力性能及承载力研究

Steel-concrete composite beam has been more and more widely used in the multistory and high-rise buildings for the benefits of high stiffness and strength and seismic performance. Building costs can further be reduced through the introduction of web openings in composite beams, which result in reduced structure heights by allowing utilities to passed through, rather than below, the composite beams. However, the introduction of web openings can significantly affect beam behavior by decreasing the stiffness and strength,and increasing the deformability of composite beams.The bending and shear capacity decreases notably, deformation increases rapidly under Vierendeel internal force at opening region. Composite beams with web openings are prestressed by high-strength bars to control concrete cracks,extending the elastic range of structural behavior, decreasing the additional deformation,increasing the stiffness and ultimate bearing capacity. The research of this project is to solve the practical calculation methods of the bending and shear capacity of prestressed composite beams with web openings, to analyze the contribution of each part of the cross-section to the shear strength of the composite beam, to study the force transfer mechanism at the openings, mechanical model of prestressed composite beams with web openings would be established,and to derive the calculation formula of bearing capacity for engineering design to provide the practical calculation methods.These proposed questions and settlement are significant to improve the design theory of prestressed composite beams with web openings.

在组合梁腹板上开洞，让日常生活中的所有管道(给排水、煤气、通风与空调等管道)从洞口通过，便能减少这些管道对建筑空间的占用，达到降低层高、节约大量的建设资金。然而，腹板开洞后组合梁的受力性能(刚度、强度、变形、破坏模式)会受到较大的影响，洞口处在"Vierendeel"内力作用下截面的抗弯与抗剪承载力明显降低、洞口处的变形急剧增大。针对以上问题本项目提出将预应力技术应用于腹板开洞组合梁，通过施加预应力来控制洞口处的混凝土的裂缝，扩大弹性工作范围，减小由于开洞所引起的附加挠度，提高组合梁的刚度和承载力。项目研究内容是解决组合梁施加预应力后洞口处的抗弯与抗剪承载力，揭示洞口处各部分截面对抗剪承载力贡献的大小，阐明洞口处的传力机制，建立合理的力学模型，推导预应力腹板开洞组合梁承载力计算公式，为工程设计提供实用的计算方法。这些研究问题的提出及其解决对完善预应力腹板开洞组合梁的设计理论具有重要意义。

在组合梁腹板上开洞，让日常生活中的管道从洞口通过，便能减少这些管道对建筑空间的占用，达到降低层高、节约建设资金的目的。但是，腹板开洞后组合梁的受力性能会受到较大的影响，洞口处的抗弯与抗剪承载力明显降低。针对以上问题本项目提出将预应力技术应用于腹板开洞组合梁，通过施加预应力来控制洞口处的混凝土的裂缝，扩大弹性工作范围，提高组合梁的刚度和承载力。因此，本项目采用试验研究、理论分析和有限元数值计算相结合的研究方法，对预应力腹板开洞组合梁的受力性能进行了研究。项目研究内容包括洞口处的抗弯与抗剪承载力。实验方面共设计了10个预应力腹板开洞组合梁试件，其中5个试件洞口设置在纯弯段和5个试件洞口设置在纯剪段；理论方面基于简化的塑性理论分析方法推导了预应力腹板开洞组合梁的抗弯和抗剪承载力计算公式；有限元方面建立了预应力腹板开洞组合梁非线性全过程受力行为的精细有限元模型，并对预应力腹板开洞组合梁的承载力影响参数（预应力筋布置形式、预应力筋初始张拉力、混凝土板配筋率、混凝土板厚、栓钉布置等）进行了分析。研究结果表明：施加预应力能明显地提高腹板开洞组合梁的刚度和承载力，而且扩大了组合梁的弹性承载力；增加混凝土板的配筋率能有效的提高组合梁的变形能力并减少混凝土板的裂缝；增加混凝土板厚能有效的提高腹板开洞组合梁的抗剪承载力；增加栓钉的数量能减小组合梁的界面滑移，并能提高预应力腹板开洞组合梁的刚度和承载力。这些研究问题的解决对完善预应力腹板开洞组合梁的设计理论具有重要意义。