## 1 Introduction  
Moment resisting beam-column connections for buildings typically consist of steel H-section members because of their stable structural performance and good workability during construction. The connections using hollow structural sections (HSSs) have been used rarely at construction sites due to their worse workability and complex details for connecting beams to columns, e.g., [1; 2; 3]. However, with development of construction technologies, including one-way bolts, a wide variety of studies to develop moment-resisting connections using the HSS or concrete-filled tubular (CFT) section have been performed, e.g., [3; 4; 5; 6; 7; 8; 9; 10]. The CFT section, comprising HSS and infilled concrete, is a composite structural system that makes good use of the merits of steel and concrete, namely, high tensile strength and ductility for steel and high compressive strength for concrete. This CFT section has been recently used in engineering applications including tall buildings, bridges, and plant facilities, e.g., [5; 11]. The interaction between the HSS and concrete enables the delay of the local buckling of the HSS by preventing the strength degradation of beam to column connection, and the increase of the concrete compressive strength by the confinement effect of the HSS. In addition, since the steel plate is positioned at the perimeter of the CFT section, the flexural performance of the HSS is maximized. This CFT construction requires no formwork, reducing the construction period and the corresponding cost, because the HSS serves as a form for concrete placement. Connection details with the CFT sections, used commonly on the construction site, are those reinforced with a through-diaphrag, internal diaphragm, and external diaphragm, as shown in Figure 1, e.g., [4; 12; 13; 14; 15; 16]. [PERSON] et al. [12] provided a design guide for structural HSS connections, where various HSS moment-resisting connections with a through-diaphrag, reduced beam section (RBS), internal diaphragm, external diaphragm, and end plate are available. More recently, [PERSON] et al. [6] proposed a CFT connection detail using a vertical diaphragm, but the gravity load tests showed that the structural performance of the connection was not obtained due to the welding failure on the beam flange. This welding problem has been one of the primary issues in the conventional HSS and CFT connection details. [PERSON] et al. [3] proposed a new seismic connection using a square HSS and H-beam. This connection was developed to resolve the issue of welding failure so that the beam and column in the proposed connection were connected only using one-way bolts, without welding. Although this connection was validated experimentally for their rotational capacity and the construction workability was dramatically improved, the problems of the integrity of the column whose upper, mid, and lower parts are connected by bolts have been raised continuously. Efforts need to be made to improve the details of the CFT connections. With rising heights of buildings, larger column sizes have been required, and sizes of HSS up to a width of 1000 mm and a thickness of 40 mm are currently available, e.g., [17]. However, there has been little information in the open literature to apply the large HSS to the beam-column connections of buildings. Furthermore, increasing terrorist threats since the 9/11 attacks have required an assessment of the blast resistance of connections for design of high-rise buildings and safety-related structures such as nuclear power plants, chemical facilities, bridges, banks, and government facilities. This paper presents a numerical study to investigate the blast performance of a pate-reinforced connection using a large square CFT column with dimensions of \(1000\times 40\) mm and a H-beam with dimensions of \(700\times 300\times 13\times 24\) mm. The reinforcing plate, used by [PERSON] et al. [18] for moment connections with steel H-section columns, is herein adopted to secure the structural performance of the proposed connection.