Ultimate Strength and Deformability of 780MPa-Grade High-Quality Steel Plates Jointed with High-Strength Bolts

780 MPa级优质钢（以下简称780 MPa钢）是新开发的低屈强比钢。为了将这种新型钢材用于与高强度螺栓连接的受拉构件，必须了解螺栓孔布置和边缘距离对连接板的极限强度和失效模式的影响，螺栓孔布置和边缘距离决定了板的几何特性。在780 MPa钢板的连接部分上进行了以下两个试验：试验1：通过拉伸试验的钢板的极限强度和破坏模式试验2：通过弯曲试验的H形梁的受拉翼缘的极限强度和破坏模式“试验1”的试样由12 mm厚的板制成。使用的螺栓孔排列为2x2（2行和2行）、2x3.2x4，3x 3和4x 3。“测试2”的梁样本由H-200 X 125 X 9 X 12截面制成。螺栓孔布置方式为2 × 2和2 × 3。钢节点板的破坏形式为净截面断裂、撕裂断裂和端部断裂。而梁翼缘的断裂形式为撕裂断裂和端部断裂。考虑以下内容：（1）对于每个距离的板和翼缘的极限拉伸强度的预测，（3）板的破坏模式和几何特性，（4）翼缘的极限强度和几何特性，（5）板和梁的变形能力。采用780 MPa级钢制成的受拉板与梁翼缘的螺栓连接，获得了高强度的螺栓连接接头。

780MPa-grade high-quality steel (hereafter 780MPa steel), which has a low yield ratio, has been developed newly. In order to use this new steel for tension members jointed with high-strength bolts, it is essential to understand the effects of bolt-hole arrangements and edge distances, which determine the geometric properties of plates, on the ultimate strength and the failure mode of the joint plates. The following two experiments were conducted on the joint part of the 780MPa steel plates :Test 1 : Ultimate strength and failure mode of steel plates by tension testsTest 2 : Ultimate strength and failure mode of tension flanges of H-shaped beams by bending testsTest specimens of "Test 1" were made of plates of 12mm thick. The bolt-hole arrangements used were 2x2 (2 rows and 2 lines), 2x3.2x4,3x3 and 4x3. The beam specimens of "Test 2" were fabricated from a H-200x125x9x12 section. The bolt-hole arrangement of the tension flanges used were 2x2 and 2x3.It was confirmed that the failure modes for the steel joint plates were net section fracture, tearing fracture and end fracture. While those for the flanges of the beams were tearing fracture and end fracture. The followings are concidered : (1) the prediction of the ultimate tensile strength of the plates and the flanges for each distance, (3) the failure mode and the geometric properties of the plates, (4) the ultimate strength and the geometric properties of the flanges, and (5) the deformation capacities of the plates and the beamsThe useful and practical design data on the high-strength bolted joints of the tension plate and the flange of the beams, which were made of 780MPa steel, were obtained.