Seismic design and evaluation of steel moment-resisting frames with compressed elastomer dampers.

This paper evaluates the hysteretic behavior of an innovative compressed elastomer structural damper and its applicability to seismic-resistant design of steel moment-resisting frames (MRFs). The damper is constructed by precompressing a high-damping elastomeric material into steel tubes. This innovative construction results in viscous-like damping under small strains and friction-like damping under large strains. A rate-dependent hysteretic model for the compressed elastomer damper, formed from a parallel combination of a modified Bouc–Wen model and a non-linear dashpot is presented. The model is calibrated using test data obtained under sinusoidal loading at different amplitudes and frequencies. This model is incorporated in the OpenSees [17] computer program for use in seismic response analyses of steel MRF buildings with compressed elastomer dampers. A simplified design procedure was used to design seven different systems of steel MRFs combined with compressed elastomer dampers in which the properties of the MRFs and dampers were varied. The combined systems are designed to achieve performance, which is similar to or better than the performance of conventional steel MRFs designed according to current seismic codes. Based on the results of nonlinear seismic response analyses, under both the design basis earthquake and the maximum considered earthquake, target properties for a new generation of compressed elastomer dampers are defined. Copyright © 2011 John Wiley & Sons, Ltd

FE parametric study of RWS/WUF-B moment connections with elliptically-based beam web openings under monotonic and cyclic loading

This paper provides numerical results investigating the behaviour of steel web-perforated beams with different shaped single openings located close to beam-to-column connections under monotonic and cyclic loading. In particular, the beams considered feature circular and patented elliptically-based perforations. Non-standard elliptically-based perforations have been proposed previously and are optimally designed to maximise resistance against Vierendeel moments and web-post buckling under static loads at the ultimate limit state. Comprehensive parametric nonlinear finite element analyses using the commercial FE package ANSYS were conducted. Initially, a FE model of the beam-to-column WUF-B moment connection was developed and calibrated against pertinent experimental results found in the literature. Next, parametric analyses were undertaken to assess the RWS/WUF-B connection regarding strength (moment), deformation (rotation) and column web shear panel zone deformation for different shapes of beam web perforations, hole sizes, and their locations. The study concludes that larger web openings are capable of moving the plastic hinge away from the column face and the CJP weld. Also, interstory drifts can be controlled with the wise use of the beam web opening size, shape, and distance from the face of the column, as suggested in the paper. Following, a step-by-step design process for RWS/WUF-B connection is presented