## 1 Introduction
The rotational stiffness and moment capacity of the joints have been studied in various parts [16; 17; 18]. In addition, many studies have been conducted on temporary structures, including support systems and scaffolds. [PERSON] et al. [19] derived the rotational stiffness of fastener-type joints of tubular steel formwork support (FTSF) systems to obtain data on the semi-rigid behavior of the joints and the initial geometric imperfections of FTSF systems. [PERSON] et al. [20] performed an experiment in which the joints for the main types of steel scaffolds used in China were classified into rigid and semi-rigid types. They found that the behavior of the semi-rigid joint type was similar to the actual behavior of the scaffold. [PERSON] and [PERSON] [13] studied the stiffness of the joints of cuplock-type with various joint configurations and loading directions (up, down, left, and right). The initial rotational stiffness of the joint was found to be the highest when the load was applied in the upward direction, and the stiffness increased as the number of horizontal members connected to the joint increased. [PERSON] et al. [15] compared rotational stiffness values from various analytical models for the rotational stiffness of clamp-type joints and suggested initial values of the rotational stiffness of clamp-type joints. [PERSON] et al. [21] studied the behavior of wedge-type support system joints by considering the presence of bracing, the height of the ground, and the number of floors in the support as variables. They also studied the critical load of the assembly and the rotational stiffness of the joint between members with respect to each variable. [PERSON] et al. [22] analyzed the moment-rotation curve for the orthogonal couplers of circular steel pipe scaffolds and found that the relationship between the moment and the rotational angle was nonlinear when the coupler connection rotated in the vertical plane, whereas it was linear in the horizontal plane. [PERSON] et al. [23] tested the rotational stiffness of wedge-type joints with plug-in connectors while other researches about the rotational stiffness studied wedge-type joints with disc (or rosette) connectors. By vision-based measurement, [PERSON] et al. studied the mechanical properties of wedge-type joints. [PERSON] and [PERSON] [24] studied the numerical model of wedge-type joints with the disc. By comparing experimental and numerical results, the friction coefficient between contact surfaces and wedge insertion depths were proposed to apply the numerical model. In South Korea, [PERSON] et al. [25] suggested an equivalent linear form for the rotational stiffness of the joint between vertical and horizontal members of a specimen through an overall shape comparison between experimental and analytical values for wedge-type joints commonly used in South Korea. [PERSON] et al. [26] suggested a trilinear model for the rotational stiffness of the wedge-type joint between vertical and horizontal members in a support system and conducted research on the moment capacity of such a system. Various probabilistic studies have been conducted on the rotational stiffness and moment capacity of the joints of temporary structures, but the valuable data for wedge joint in support systems considering reused members is insufficient to apply for design process. Moreover, as the boundary condition of the joint between vertical and horizontal members is generally assumed to be a simple hinge in design standards and the safety of a structure is considered to depend on its elastic behavior within the allowable stress range, there are limitations on accurately predicting the ultimate behavior of support systems. Therefore, in this study, experiments reflecting the characteristics of reused members were performed for wedge joints connecting vertical and horizontal members of assembled support systems, and the moment capacity and rotational stiffness of wedge joints were analyzed to predict the ultimate behavior of such support systems on actual sites.