Conventional Moment-resisting Frames Research Articles

Experimental evaluation of the seismic performance of steel MRFs with compressed elastomer dampers using large-scale real-time hybrid simulation

Real-time hybrid simulation combines experimental testing and numerical simulation, and thus is a viable experimental technique for evaluating the effectiveness of supplemental damping devices for seismic hazard mitigation. This paper presents an experimental program based on the use of the real-time hybrid simulation method to verify the performance-based seismic design of a two story, four-bay steel moment resisting frame (MRF) equipped with compressed elastomer dampers. The laboratory specimens, referred to as experimental substructures, are two individual compressed elastomer dampers with the remainder of the building modeled as an analytical substructure. The proposed experimental technique enables an ensemble of ground motions to be applied to the building, resulting in various levels of damage, without the need to repair the experimental substructures, since the damage will be within the analytical substructure. Statistical experimental response results incorporating the ground motion variability show that a steel MRF with compressed elastomer dampers can be designed to perform better than conventional steel special moment resisting frames (SMRFs), even when the MRF with dampers is significantly lighter in weight than the conventional MRF.

Seismic response of perforated lightweight aggregate concrete wall panels for low-rise modular classrooms

In this paper, details of precast concrete wall panels for construction of low-rise modular school buildings are described. These panels, designed to be the primary lateral force resisting system of the building, are relatively thin. Compared to the case for conventional moment-resisting frames or shear-wall buildings, where details have been extensively verified to be seismically effective, the seismic response of this type of building is less certain, in part due to the large window and door openings as well as the unusual detailing commonly adopted for their reinforcement and connections. Concerns for seismic performance of these panels were addressed by two full-scale tests of prototype panels. Test results, in particular with respect to the lateral strength, deformation capacity and hysteretic loops of the panels, are presented in the paper.

Fragility analysis of flat-slab structures

Flat-slab RC buildings exhibit several advantages over conventional moment-resisting frames. However, the structural effectiveness of flat-slab construction is hindered by its alleged inferior performance under earthquake loading. Although flat-slab systems are widely used in earthquake prone regions of the world, fragility curves for this type of construction are not available in the literature. This study focuses on the derivation of such fragility curves using medium-rise flat-slab buildings with masonry infill walls. The study employed a set of earthquake records compatible with the design spectrum selected to represent the variability in ground motion. Inelastic response-history analysis was used to analyze the random sample of structures subjected to the suite of records scaled in terms of displacement spectral ordinates, whilst monitoring four performance limit states. The fragility curves developed from this study were compared with the fragility curves derived for moment-resisting RC frames. The study concluded that earthquake losses for flat-slab structures are in the same range as for moment-resisting frames. Differences, however, exist. The study also showed that the differences were justifiable in terms of structural response characteristics of the two structural forms.

Ductile Steel Beam-to-Column Connections for Seismic Resistance

The strength and ductility of steel frames depend strongly on the behavior of their beam-to-column connections. The fracture of beam-to-column connections of steel buildings in the Northridge Earthquake generated concern about the reliability of current design and construction technology on steel connections. There is an urgent need to find a reliable method to retrofit these connections and to use it for the design of new buildings. A simple method is proposed here to enhance the ductility of beam-to-column connections. On trimming the beam flanges slightly, the ductility of the connection can be improved greatly. Experimental study of the newly designed connections under cyclic load shows that the ultimate strengths are almost unaltered, whereas the stiffness is decreased only slightly. However, the plastic rotational capacity can be increased several times. Moreover, the fracture proneness of connections due to welding sensitivity and stress concentration from abrupt geometry alternation can be minimized and the energy dissipation capacity can be improved. A shaking table test of a steel frame designed according to the proposed connection method also behaves better than that of a conventional moment-resisting frame.