Partially or fully restrained steel moment connections are essential constituents of lateral force resisting moment frames. The constituents of the moment connection system – bolts, welds, plates and angles – are sized using their individual force demands by a limit state element-based load and resistance factor design procedure. The system reliability of the connection as a whole, which must be commensurate with reliabilities of adjoining frame components, has not been adequately investigated in the literature. This paper presents a methodology to determine the system reliability of commonly used steel moment connections that have been designed according to current element based procedures. A general expression is derived for a system factor that modifies element resistance factors to meet a specified system reliability target, as a function of the element’s relative importance within the system, and associated uncertainties. Uncertainties in element capacities (including their mutual dependence) and system demands are considered. The approach can be used to rationalize element design equations to achieve system reliability targets for the connection system. A detailed numerical example and a set of parametric studies on a partially restrained moment connection with angle supports at top and bottom beam flanges are presented. The results suggest the existence of beneficial system effects in current AISC provisions for the design of partially restrained moment connections.

部分或完全约束钢弯矩连接是抗侧向力弯矩框架的重要组成部分。力矩连接系统的组成部分——螺栓、焊缝、板和角钢——通过基于极限状态元件的载荷和阻力系数设计程序，使用各自的力需求来确定尺寸。整个连接的系统可靠性必须与相邻框架部件的可靠性相称，但文献中尚未对此进行充分研究。本文提出了一种确定常用钢弯矩连接系统可靠性的方法，这些连接是根据当前基于单元的程序设计的。导出系统因子的一般表达式，该表达式修改元件电阻因子以满足指定的系统可靠性目标，作为系统内元件的相对重要性和相关不确定性的函数。考虑了元件能力（包括它们的相互依赖性）和系统需求的不确定性。该方法可用于合理化元件设计方程，以实现连接系统的系统可靠性目标。提出了关于顶部和底部梁翼缘角支撑的部分约束力矩连接的详细数值示例和一组参数研究。结果表明，当前 AISC 规定中对于部分约束力矩连接的设计存在有益的系统效应。