钢夹板-螺栓连接胶合木梁疲劳试验研究

Fatigue behaviors of glulam beams connected with steel splints and bolts

钢夹板-螺栓连接胶合木梁在实际工程运用中受到循环往复动荷载的作用,极易产生损伤累积而造成构件失效。为了研究钢夹板-螺栓连接胶合木梁的疲劳特性,通过不同应力水平下的等幅疲劳试验及静力对比试验,分析了钢夹板-螺栓连接胶合木梁的疲劳破坏形态与机理,研究了其刚度退化规律,探讨了疲劳极限荷载。试验结果表明,钢夹板-螺栓连接胶合木梁的疲劳破坏主要发生在加载点附近。随着疲劳循环次数的增多,钢夹板-螺栓连接胶合木梁的跨中挠度以及沿截面高度的拉、压应变均显著增大,压应变增幅大于拉应变,且应变分布情况基本符合平截面假定。试验梁的弯曲刚度随着疲劳循环次数的增加而呈现出线性退化,基于刚度退化的疲劳寿命预测与试验实测寿命基本吻合。钢夹板-螺栓连接胶合木梁的疲劳寿命随着应力水平的增大而降低,在应力比为0.2,应力水平不超过0.5倍静力极限荷载时,疲劳寿命均大于200万次,表明钢夹板-螺栓连接胶合木梁具有较好的疲劳特性。此外,还对疲劳载荷的振幅和疲劳寿命进行了线性回归分析,得到的疲劳极限载荷为0.5435 F_(u)。最后,利用ANSYS nCode软件对试验梁进行疲劳有限元分析,分析表明,该软件能较好地模拟钢夹板-螺栓连接胶合木梁在不同应力比下的疲劳响应。

The glulam beams connected with steel splints and bolts are usually subjected to cyclic reciprocating dynamic loads in practical engineering applications,which are prone to damage accumulation and component failure.In order to study the fatigue characteristics of the glulam beams connected with steel splints and bolts,the fatigue damage morphology and mechanism of the glulam beams were analyzed,the stiffness degradation was studied,and the fatigue limit load was explored through the constant amplitude fatigue tests at different stress levels and the static comparative tests.The test results show that the fatigue damage of the glulam beams connected with steel splints and bolts mainly occurs near the loading point.With the increase of the number of fatigue cycles,the mid-span deflection of the glulam beams,the tensile and compressive strains along the height of the section increase significantly,the compressive strain increases more than the tensile strain,and the strain distribution basically conforms to the assumption of plane section.The bending stiffness of the test beam decreases basically linearly with the increase of the number of fatigue cycles.The fatigue life of the glulam beams connected with steel splints and bolts decreases with the increase of the stress level.When the stress ratio is 0.2 and the stress level does not exceed 0.5 times the static ultimate load,the fatigue life is greater than 2 million times,indicating that the glulam beams connected with steel splints and bolts have good fatigue properties.In addition,a linear regression analysis on the amplitude of the fatigue load and the fatigue life was performed,and the fatigue ultimate load of 0.5435 F_(u) was obtained.Finally,the fatigue finite element analysis of the test beams was performed using ANSYS nCode software,and the analysis show that the software can better simulate the fatigue response of the glulam beams connected with steel splints and bolts under different stress ratios.