胶合木T梁负弯曲性能试验研究

Experimental study of negative bending performance of glulam T beam

【目的】探讨胶合木T梁的负弯曲性能,观察极限状态下构件的破坏形式,解析极限状态下构件的破坏机理,推导极限承载能力计算模型,以期为工程实际应用提供理论参考依据。【方法】采用跨中荷载试验与理论计算对比方式进行研究,实测分析了两组试件的应变、挠度、抗弯刚度、极限承载力及延性结果,观察分析了胶合木梁的破坏形态与破坏机理,基于Rammer剪切强度公式将弯剪强度理论值和试验值进行了对比。用兴安落叶松作为原材料,以剪跨比、跨高比为参数,设计制作2组即A组3根(高跨比1/12,剪跨比5.2)、B组3根(高跨比1/14,剪跨比6.1),共计6根平行胶合木T梁试件。将T梁反转成倒T梁,在两端简支条件下跨中加载产生正弯矩,使肋板受压、翼板受拉,模拟连续T梁跨中支承截面的受力性能。【结果】1)两组构件整体工作性能良好,受弯时极限破坏形态均为中部顺纹剪切破坏。2)两组构件相比,B组较于A组试件,屈服荷载降低9.7%,跨中屈服位移提高27.5%,极限抗弯承载力降低10.4%,跨中极限位移提高42.7%,抗弯刚度降低36%,延性系数提高22.4%。3)两组构件的荷载应变曲线在达到屈服点之前呈比例关系,满足平截面假定。4)受剪力滞效应影响,两组构件的跨中截面翼缘板正应力横向分布不均匀,呈现随距离肋板中心位置越远而越小的关系,最大差值比率达30%。5)构建了弯剪承载力计算模型,理论值与试验值最大相差3.1%,匹配度较高。【结论】总结了胶合木连续T梁在跨中支承截面的受力变形规律,揭示了其破坏机理,构建了极限弯剪承载力计算模型,经验证,具有一定的可靠性。

【Objective】In order to provide theoretical reference for the practical application of engineering, to study the negative bending performance of glued timber T beam, observe the failure form of the member in the limit state, analyze the failure mechanism of the member in the limit state, and deduce the calculation model of the limit bearing capacity.【Method】the cross in the load test and theoretical calculation for comparison study, the experimental analysis of the two groups of specimens of strain, deflection, bending stiffness and ultimate bearing capacity and ductility as a result, observing and analyzing the failure pattern of the glulam beams and the failure mechanism, based on Rammer shear strength formula will bend shear strength compared with the theoretical value and experimental value. Using xing ‘an larch as the raw material, 3 members of group A(high span ratio 1/12, shear span ratio 5.2) and 3 members of group B(high span ratio 1/14, shear span ratio 6.1) were designed and made with shear span ratio and span ratio as parameters. The T beam is inverted into an inverted T beam, and the positive bending moment is generated in the mid-span loading under the condition of simple supports at both ends, so that the floor plate is pressed and the wing plate is pulled, and the mechanical performance of the mid-span support section of continuous T beam is simulated.【Result】1) the two groups of components performed well on the whole, and the ultimate failure modes under bending were the failure modes of the central longitudinal shear. 2) compared with the two groups of members, the yield load of group B is 9.7% lower, the mid-span yield displacement is 27.5% higher, the ultimate bending capacity is 10.4% lower, the mid-span ultimate displacement is 42.7% higher, the bending stiffness is 36% lower, and the ductility coefficient is 22.4% higher. 3) the load strain curves of the two groups of components show a proportional relation before reaching the yield point, and meet the assumption of flat section. 4) affected by the shear lag effect, the lateral distribution of the positive stress on the flange plate of the mid-span section of the two groups of members is not uniform, which shows a relationship of decreasing with the distance from the center of the floor, and the maximum difference ratio is up to 30%. 5) a calculation model of flexural shear capacity is constructed, with a maximum difference of 3.1% between the theoretical value and the experimental value, and a high degree of matching.【Conclusion】This paper summarizes the stress and deformation law of glue-wood continuous t-beam in the mid-span support section, reveals its failure mechanism, and constructs the calculation model of ultimate bending shear capacity.