The low-rise steel-framed buildings that make up a large space are expected to function as disaster prevention bases in the event of a disaster due to their high capacity and are required to ensure high seismic performance in order to demonstrate their functions as bases. H-shaped members are often used for columns in such a structure, and brace members generally connect the weak axis direction. The brace members that resist seismic load are essential structural members, and its connection strength has a significant influence on the frame's behavior and strength, including the brace members, so it does not break at the joint until the member is yielded. Currently, strength formulae for braced members constructed based on experimental results on specimens with a plate thickness of 6.0 mm or more are used. However, in recent steel structural buildings, thin members are used as structural members in order to improve the efficiency and weight of the cross-section of the members. Based on the above, in this paper, the shape factors that affect the joint strength of the braced members composed of thin plates (thickness of 6.0 mm or less) are clarified by joint tensile experiments and finite element numerical analysis. The purpose of this study is to propose unified evaluation formulae for bolted connection members, which can apply to the members composed from thin plate members to thick plate members.
From this research，the following are found．
1) From experimental and numerical analysis results, plate thickness, outstanding leg length, and cross-sectional shape affect joint efficiency. These parameters are shape variables related to the eccentric distance of the connection, and the joint efficiency decreased as the increment of the eccentric distance.
2) The strength of the connection is hardly affected by the thickness of the gusset plate and the length of the member.
3) Even if the number of bolts and the bolt pitch are different, if the joint length is the same, the strength of the connection is the same, and the joint efficiency increase as the joint length increases.
4) The strength formulas in Japan and overseas can conservatively evaluate the ultimate strength of the brace members in a relatively small range up to a width-thickness ratio of about 20 or less. On the other hand, thin plate members with a width-thickness ratio greater than 20 tend to be overestimated.
5) The ultimate strength evaluation formula is proposed using the combination variable of the eccentric distance of the cross-section and the joint length, and the ratio of the bolt hole diameter and the joint leg width. The proposed evaluation formula gives a reasonable evaluation to the brace members, which occur net section fracture, from thin plates to thick plates, and is more significant than the existing strength formulas. Also, a strength formula for yield strength is proposed. And the validity of the formula is shown by comparing it with the experimental results.
