Experimental Study on Seismic Strengthening of Timber Beam-Column Joints by Lateral Confinement

木结构框架梁柱节点在地震作用下承受轴力、剪力和弯矩。在这项研究中，提出了两种方法来加强螺栓连接承受轴向拉力。一种方法是用GFRP（玻璃纤维增强塑料）制成的方箍横向约束节点，另一种方法是用带有两个大方垫圈的横向螺栓约束节点的劈裂。通过对91根截面为105 mm的杉木柱进行轴向拉伸试验，研究了螺栓连接节点（商品名为超级节点）的抗拉性能。试验变量为GFRP方箍的厚度和宽度，分别为5 ~ 7 mm和20 ~ 120 mm。此外，横向螺栓的方垫圈尺寸为20x20x3mm^3、40x40x5mm^3、60x60x8mm^3。试验结果表明，GFRP方箍和横向螺栓能提高节点的变形能力。对于GFRP箍筋，当箍筋宽度大于80 mm时，不仅节点的变形能力得到了显著提高，而且节点的强度也得到了显著提高。然而，从实际使用的角度来看，横向螺栓的有效性并不那么明显，因为它们只有在接头大变形后才有效。作为附加试验，建造了8个三层木框架，并在水平静荷载下进行了试验，这些水平静荷载施加到每个楼层，模拟地震力。在此基础上建立了节点模型，对框架进行了分析，预测了框架的受力性能，预测结果与试验结果吻合较好。

The beam column joints of a timber structural frame are subjected to axial force, shear force and flexural moment during earthquakes. In this study, two methods have been proposed to strengthen the bolt joints subjected to axial tension force. One method is to laterally confine the joints using a square hoop made of GFRP (glass fiber reinforcedplastics) and the other is to restrain the splitting of the joints using a transverse bolt with two large square washers. The effectiveness of those methods have been investigated by conducting axial tension tests on the joints.For the tests, 91 cedar columns with 105mm square section were prepared with the bolt connectors, which was called super-joints as the trade name. As the experimental variables, the thickness and width of the GFRP square hoops were varied from 5 to 7mm and 20 to 120 mm, respectively. Also, the sizes of the square washers for the transverse bolts were variedas 20x20x3mm^3, 40x40x5mm^3, 60x60x8mm^3. The test results indicated that those GFRP square hoops and the transverse bolts could improve the deformation capability of the joints. In case of the GFRP hoops, not only deformability but also strength of the joints were significantly improved when the width of the hoops were more than 80mm. However, the effectiveness of the transverse bolts were not so appreciable from the view point of a practical use because they became effective only after large deformation of the joints.As additional tests, 8 of three-story timber frames with full scale were constructed and tested under horizontal static loads which were applied to each floor level simulating seismic forces. The behaviors of the frames were predicted by frame analyses with the joint models which were established based on the above axial tension tests, The predicted behaviors were well agreed with the observation of the frame tests.