Ahmed Mohamed Ahmed Elkady

EARTHQUAKE LOSS ASSESSMENT OF STEEL FRAME BUILDINGS DESIGNED IN HIGHLY SEISMIC REGIONS

In recent years, there is an increasing need to quantify earthquake-induced losses throughout the expected life of a building in order to evaluate alternative design options and to minimize repairs in the aftermath of an earthquake. For this reason, the next generation of performance-based earthquake engineering evaluation procedures has formalized procedures that assess several metrics of seismic performance including economic losses. This paper discusses an analytical study that quantifies the expected earthquake-induced losses in typical office steel buildings designed with perimeter special moment frames or perimeter concentrically braced frames at various ground motion intensities. These buildings are designed in urban California in accordance with today’s seismic design provisions in North America. The expected economic losses associated with repair are computed based on a refined performance-based earthquake engineering framework developed within the Pacific Earthquake Engineering Research (PEER) center. This framework integrates site-specific seismic hazard, state-of-the-art nonlinear models that incorporate complex deteriorating phenomena of the structural components of a steel frame building, fragility curves of structural and nonstructural components that express the probability of being or exceeding a specific damage level, and the resulting repair costs. The effect of residual deformations along the height of steel frame buildings on their earthquake losses is also examined. It is shown that repair costs in the aftermath of earthquakes vary significantly depending on the employed lateral load resisting system, as well as the analytical model representation of the steel frame building itself.

Effect of Composite Action on the Dynamic Stability of Special Steel Moment Resisting Frames Designed in Seismic Regions

Seismic assessment of steel frame structures is typically concerned with analytical modeling of the lateral load-resisting system only, ignoring the effect of composite action on its lateral stiffness and strength. Based on a recently developed database for deterioration modeling of steel beams with reduced beam sections (RBS), the effect of composite action on their bending strength and deterioration parameters (e.g. plastic rotation capacity, post capping rotation capacity, rate of cyclic deterioration) under cyclic loading can be quantified. These connections are widely used in United States in design of special steel moment resisting frames. A phenomenological model, which is able to simulate important deterioration modes when a steel component is subjected to cyclic loading, has been modified to incorporate slab effects on moment-rotation characteristics of composite steel beams. The effect of composite action on the collapse capacity of SMFs is demonstrated through a case study of an 8-story steel building..

Design Decision Support for Steel Frame Buildings through an Earthquake-Induced Loss Assessment

In recent years, there is an increasing need to quantify earthquake-induced losses throughout the expected life of a building in order to evaluate alternative design options such that we can minimize repairs in the aftermath of an earthquake. This paper discusses an analytical study that quantifies the expected economic losses in a portfolio of archetype steel frame buildings designed with perimeter special moment frames or special concentrically braced frames in urban California in accordance with current seismic provisions in the U.S. The expected economic losses associated with repair are computed based on an established loss estimation framework within the context of performance-based earthquake engineering. It is shown that repair costs in the aftermath of earthquakes vary significantly depending on the employed lateral load-resisting system, seismic design considerations as well as the analytical model representation of the archetype frame building itself.

Full-Scale Testing of Deep Wide-Flange Steel Columns under Multiaxis Cyclic Loading: Loading Sequence, Boundary Effects, and Lateral Stability Bracing Force Demands

AbstractThis paper discusses the findings from 10 full-scale steel column tests subjected to multiaxis cyclic loading. The columns use deep wide-flange cross sections typically seen in steel moment...

Improved Seismic Design and Nonlinear Modeling Recommendations for Wide-Flange Steel Columns

AbstractThis paper presents the findings of parametric finite-element (FE) simulations of more than 50 wide-flange steel columns under cyclic loading. The column sizes, which are mostly highly duct...

Fragility Curves for Wide-Flange Steel Columns and Implications on Building-Specific Earthquake-Induced Loss Assessment

Building-specific loss assessment methodologies use component fragility curves to compute expected losses in the aftermath of earthquakes. Such curves are not available for steel columns assuming they remain elastic because of capacity design considerations. Nonetheless, first-story steel columns in moment-resisting frames (MRFs) are expected to experience damage through flexural yielding and formation of geometric instabilities. This paper uses an experimental database that was recently assembled to develop two sets of univariate drift-based column fragility curves that consider the influence of loading history. Ordinal logistic regression is also employed to develop multivariate fragility curves that capture geometric and loading parameters that affect column performance. The implications of the proposed fragility curves for building-specific loss assessment are demonstrated using an eight-story office building with steel MRFs. It is shown that structural repair costs in this case may increase by 10%, regardless of seismic intensity, when column damage is considered. Similarly, the contribution of structural component repairs to expected annual losses may double over the buildings life span.