Drift and Ductility Estimates in Regular Steel MRF Subjected to Ordinary Ground Motions: A Design-Oriented Approach

Abstract

A simple procedure to estimate drift and ductility demands of regular steel frame buildings subjected to ordinary (i.e., without near fault effects) ground motions is described. Given the strength reduction (or behavior) factor, the procedure provides reliable estimates of the maximum roof displacement, the maximum interstorey drift ratio and the maximum rotation ductility along the height of the structure. The strength reduction factor refers to the point of the development of the first plastic hinge in the building and thus, pushover analysis and estimation of the overstrength factor are not required. This important feature enables both the rapid seismic assessment of existing structures and the direct deformation-controlled seismic design of new ones. The derivation of the proposed relations is based on regression analysis of the results of thousands of nonlinear time history analyses of steel frames. A comparison of the proposed method with the procedures adopted in current seismic design codes reveals the efficiency of the former.

Seismic response of plane steel MRF with setbacks: Estimation of inelastic deformation demands

“…The design process of the frames resulted in optimum cross-sections of the columns which satisfy both the requirements for strength/stiffness [16] and the capacity design rule [13]. For each of the frames, the column cross-sections were subsequently increased two times in order to obtain three different values of the column-to-beam strength ratio, a, defined as [19] Table 1 Data pertinent to the setback steel MRF considered in this investigation where M RC,1,av is the average of the plastic moments of resistance of the columns of the first storey and M R B,av is the average of the plastic moments of resistance of the beams of all the stories of the frame. For a given level of ductility and for given cross-sections of beams, an increase of a will delay the mechanism action (simultaneous appearance of plastic hinges at the end of beams and at the base of the columns of the first storey).…”

Estimation of peak displacements in steel structures through dimensional analysis and the efficiency of alternative ground-motion time and length scales

“…In this respect, many studies have focused on the prediction of maximum displacements in steel structures employing generic multi-storey frames [17,30] as well as equivalent single-degree-of-freedom (SDOF) systems [3,32,37]. Although the idealization of a multi degree of freedom structure as a SDOF system entails the neglection of a number of dynamic phenomena such as the contribution of higher modes, it has been recognised that equivalent SDOF models can provide a good basis for the estimation of global demands in building structures [27,31,35].…”

Simple Formulae for Damage Estimation of Composite Steel/Concrete Moment Resisting Frames

“…In the inelastic range of the response and especially at higher values of ductility, the influence of ρ is lost since the structure behaves in a mechanism type of mode. Furthermore, Karavasilis et al [24] have introduced during the investigation of the inelastic seismic response of steel MRFs the beam strength ratio, α, which indicates how much stronger are the beams in comparison with the base columns. According to that work [24], the parameter α adopted here is defined as…”