小跨高比胶合木梁受弯性能及增强试验

Experiment on Flexural Behavior and Strengthening of Glued Timber Beams with Small Span to Height Ratio

为研究工程用胶合木梁的受力性能,对分别采用未增强及在底部粘贴钢板、在底部弯剪区拧入螺钉、在两侧中部粘贴钢板增强方式的4组共计9根跨高比为12的胶合木梁进行受弯承载力试验。通过试验得到各试件破坏形态、荷载-位移曲线,分析了增强后木梁的力学性能和跨中应变分布规律。提出了木梁在三分点受弯试验时发生受拉和受剪破坏的界限跨高比;在验证了受弯木梁的截面应变分布基本符合平截面假定后,提出了小跨高比胶合木梁及增强构件在三分点受弯试验时发生顺纹剪切破坏的极限承载力计算公式。结果表明:小跨高比胶合木梁的破坏形式为顺纹剪切破坏,破坏时无征兆,破坏面基本发生在木梁的中性轴及偏下位置;底部粘钢梁在受弯时受压区面积增大,中性轴下移,极限承载力和刚度都有所提高;梁底拧入螺钉和侧面贴钢板能很好地提高梁的抗剪能力和极限承载能力;所提出的承载力计算公式的计算值和实测值相对误差大都在20%以下,且计算值相比实测值偏于安全,可为此类构件的设计和工程应用提供参考。

In order to study the mechanical performance of the glued wood beam used in engineering,the flexural bearing capacity tests on 9 wood beams with the span to height ratio of 12 in 4 groups were carried by means of unreinforced,pasting steel at the bottom,screwing screws in the bottom bending shear area and pasting steel plates in the middle of both sides.The failure forms,load-displacement curves and other properties of the specimens were obtained through tests,and the mechanical properties and the distribution law of mid-span strain of the strengthened wood beam were analyzed.The limit span to height ratio of wood beam subjected to tensile and shear failure in three-point bending test was proposed.In the validation of cross section of bending beam strain distribution basic according with plane section assumption,the formula for calculating ultimate bearing capacity of glued timber beams with small span to height ratio and enhance member when shear failure along grain in the three-point bending test was proposed.The results show that the failure mode of the small span to height ratio glued wood beam is shear failure along the grain,and there is no sign of failure,and the failure surface basically occurs in the netural axis and the lower location of the wooden beam.The area of compression zone of bottom bonded steel beam increases,the neutral axis moves down,and the ultimate bearing capacity and stiffness both increase.The shear resistance and ultimate bearing capacity of the beam can be improved by screwing screws into the bottom of the beam and attaching steel plates to the side.The results show that the errors between the theoretical values and the measured values are mostly below 20%,and the theoretical values are safer than the measured values,which can provide reference for the design and engineering application of such components.