轻钢矩管桁架梁-OSB板组合楼盖的受力性能与设计方法研究

In the previous study, it was found that the flexural rigidities and ultimate capacities of Light Gauge Steel(LGS) square tube truss girders could be notably enhanced if full shear connection with Oriented Strand Board (OSB) was applied. Meanwhile, the stability of the upper cord girder could also be improved. Currently, limited research studies can be found about LGS-OSB composite floor, and no qualitative consideration about the positive effect of OSB is proposed. This project intends to investigate the bearing capacity and flexural rigidity of the LGS-OSB composite floor through experimental studies and theoretical analyses. First of all, the shear stiffness of the self-tapping screw will be determined by experimental test. And the accuracy of FEM models will be verified based on the experimental data. Then, Finite Element Method (FEM) will be used to analyze the influencing factors of the structural behavior of the LGS-OSB composite floor. Furthermore, the local buckling of the upper cord of the truss girder will be studied based on theoretical analyses of compression-flexural member, in order to verify the feasibility of applying the effective width method on calculating the strength and the stability of the upper cord of the truss girder of the composite floor. Also, the flexural rigidity of LGS-OSB composite floor will be studied considering the slide effect at the interface of OSB and truss girders. Finally, analytical methods to calculate the bearing capacity of the LGS truss girder and LGS-OSB composite floor and the flexural rigidity of the LGS-OSB composite girder will be proposed. This project can provide the theoretical basement for drafting the related structure design codes, and will be significant for promoting the development and application of LGS structure system.

申请者在前期研究中发现，当OSB板（定向刨花板）与轻钢矩管桁架梁完全抗剪连接时，能明显地增加其弯曲刚度和极限承载力，并影响上弦管的局部稳定，但目前对轻钢矩管桁架梁组合楼盖的研究较少，且未定量地考虑OSB板的有利作用。本项目拟采用试验和理论分析方法研究轻钢矩管桁架梁-OSB板组合楼盖的力学性能。首先由试验确定自攻螺钉连接的抗剪刚度，并通过桁架梁及其OSB板组合楼盖的受弯性能试验验证有限元模型的正确性，接着利用有限元分析轻钢矩管桁架梁及其组合楼盖受力性能的影响因素；然后基于压弯构件理论分析上弦管的局部屈曲，验证有效宽度法对于上弦管强度及稳定性验算的适用性，并通过考虑交界面上的滑移效应分析轻钢矩管桁架-OSB板组合梁的抗弯刚度；最终提出桁架梁及其组合楼盖承载力的计算方法，以及组合梁抗弯刚度的简化计算公式。研究成果可为编制相关规范提供理论依据，对推动轻钢结构体系的发展应用具有重要的科学意义。

前期研究发现，当OSB板（定向刨花板）与轻钢矩管桁架梁完全抗剪连接时，能明显地增加其弯曲刚度和极限承载力，并影响上弦管的局部稳定，但目前对轻钢矩管桁架梁组合楼盖的研究较少，且未定量地考虑OSB板的有利作用。本项目重点对轻钢矩管桁架梁及其OSB板组合楼盖的受力性能进行了试验研究和理论分析。.本项目通过轻钢矩管桁架梁及其OSB板组合楼盖的受力性能的试验研究以及有限元分析，系统研究了弦管截面尺寸和OSB板厚度、螺钉间距等因素对桁架梁及其组合楼盖抗弯刚度和极限承载力的影响以及上下弦管共同工作的机理、OSB板对上弦管稳定性的影响，并进行了轻钢矩管桁架梁的优化研究，分析了影响组合楼盖上弦管稳定性能的因素；通过借鉴钢-混凝土组合梁跨中挠度的分析方法，提出了确定桁架梁跨中挠度的简化计算方法；制定出了OSB板轻钢矩管桁梁组合楼盖的快速设计表。.研究表明：轻钢矩管桁架梁及其OSB板组合楼盖的破坏模式主要表现为跨中节间上弦管的局部屈曲破坏，少数构件出现整体垮塌。OSB板可以明显提高梁的平面外抗弯刚度，OSB板厚度对上弦管有效抗弯刚度提高显著；当OSB厚度不变，板的层数和布置方式对完全抗剪连接组合梁的承载力影响较小。上、下弦管壁厚对轻钢矩管桁架梁和组合楼盖的刚度及承载力都有较大影响；截面尺寸相同的情况下，下弦上开口梁的受力性能优于下开口梁，但下开口梁的下弦材料强度利用得更充分；下弦管截面面积相同时，下弦采用截面高度大的U形截面的桁架梁比矩形截面的抗弯刚度更大，极限承载力更高。中、美、澳三国规范对轻钢矩管桁架梁极限状态的验算公式比较准确且略偏安全，而对组合楼盖却均过于保守。《冷弯薄壁型钢结构技术规范》的有效宽度法和AISI S100的ASD法可以用来确定桁架单梁承载力和组合楼盖的初始屈曲承载力；计算组合楼盖的极限承载力时，应该考虑OSB板对有效面积及截面惯性矩的影响。建议常用跨度组合楼盖OSB板的厚度可采用9mm或12mm；上弦矩管厚度为0.8mm~1.2mm时，自攻螺钉间距可采用50mm~150mm。