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Gravity system energy dissipation contribution in seismic performance of special steel moment frames

Abstract:

The effect of the gravity framing system on the seismic performance of steel frame buildings is an essential, but currently challenging aspect of pbkp_redicting building performance and evaluating community resilience in earthquakes. Analytical studies and field observations have indicated that the gravity framing system, can have a profound effect on the lateral behavior of steel-framed buildings. The main factors that affect the influence of the gravity framing are the gravity columns and the beam-column connections. The gravity columns improve the performances of steel structures providing what is known as continuous stiffness. On the other hand, gravity connections provide strength and another source of energy dissipation. Even though different studies have concluded that the gravity system improves considerably the collapse performance of special steel frame structures, it is still neglected at the design and analysis stage. One of the main reasons why the gravity system is not considered is the difficulty of modeling the beam-column connections. The cyclic hysteretic behavior of commonly used gravity connections presents strength degradation and pinching behavior. Previous investigations have shown the importance of modeling accurately the cyclic behavior of the lateral resisting system, especially to capture dynamic instability. However, there are no studies regarding the effects of accuracy when modeling gravity connections. This paper investigates the effects of modeling the gravity connections on the seismic performance of special steel structures different approaches that vary in difficulty. The effectiveness of the approaches is illustrated through the analysis of an 8-Story building Nonlinear dynamic response history analyses are conducted and the effect of the approaches used is evaluated in terms of deformations, energy dissipation and the collapse performance. The results obtained in this investigation show that modeling in detail the gravity connection s hysteretic behavior is not relevant when the dissipation of energy is compared to the main lateral resisting system.