In building construction, steel beam assembly has been considered as one of the most dangerous manual operations. In this paper, applying robotic technologies to the steel beam assembly task is discussed. Employing the robotic systems to automate such construction tasks gives the following advantages: saving construction time and cost, enhancing operator's safety, and improving overall quality. The automated robotic assembly system presented in the paper consists of a robotic bolting device, a robotic mobile mechanism, and a bolting control system including human-machine interface. The robotic bolting device, which includes a bolting end-effector and a robotic manipulator, performs actual bolting operation. Utilizing the robotic mobile mechanism composed of a rail sliding boom mechanism and a scissors-jack type mobile manipulator, the robotic assembly system can be transported to a target position for bolting operation. The bolting control system plays a role of safely and efficiently operating the robotic assembly system employing a hole recognition system based on vision technology and a haptic based HMI (Human-Machine Interface) system. This paper includes the major components of the entire robot system that have been built and the future plans to integrate them.