Robert Levy

Economic Feasibility Analysis of Pre-earthquake Strengthening of Buildings in a Moderate Seismicity / High Vulnerability Area

Abstract While regions with high seismicity have been widely investigated, areas with moderate seismic hazard has not been fully adequately studied as being exposed to high risk due to their vulnerable built environment. A standardized and straightforward risk assessment methodology is needed for public authorities in moderate seismic / high vulnerability areas to assess the potential seismic risks and to make corresponding structural strengthening plans for protecting properties and peoples lives. Adopting the standardized seismic loss assessment tool HAZUS, this study aims to present the methodology for investigating the economic feasibility of the pre-earthquake structural strengthening of buildings by means of benefit-cost analysis. Therefore, the specific objectives of this study are to: (1) to assess the seismic risks with building and demography parameters which can fully represent the characteristic of local built environment, (2) to conduct benefit-cost analysis of the seismic mitigation activities, and (3) to verify the applicability of the present methodology by a case study. To assess risk from earthquake hazards, both deterministic and probabilistic earthquake scenarios were simulated, combined with micro-zoning studies, geological characteristics, building inventories, population distribution, and adaptation of the building fragility curves and casualty matrix to the local conditions. This study intends to provide public decision makers a standardized methodology for justifying the economic feasibility of seismic risk mitigation alternatives so that a cost-efficient public earthquake mitigation strategy can be achieved.

Multi-Modal Control of Pedestrian Bridges Using Tuned-Mass-Dampers

This paper deals with the allocation and sizing of multiple tuned-mass-dampers (MTMDs) in an attempt to retrofit footbridges with multiple critical modes resulting from the excitation of pedestrian traffic. The simple and practical methodology proposed herein includes the use of an iterative analysis/redesign type procedure that converges to a given allowable level of acceleration. An example that uses this methodology to retrofit an existing footbridge is presented.

Blast Waves Caused by Internal Explosion in Ammunition and Explosive Facility: Vulnerability and Protection Alternatives

Internal explosion in an ammunition and explosive (A&E) facility might cause the most dangerous consequences. The blast can spread to all parts of the facility harming personnel in different levels. High pressure can cause lethality due to lung damage. It might also cause building collapse mainly of the structure’s elements right aside the explosion that might turn into debris and rubbels. The secondary fragments of nearby equipment (connected or unconnected) might fly with high velocity. Shock wave moving through the structure and the ground might cause people to be overturned or to fall down with possible injuries or fatalities.

A Simple Methodology for the Seismic Passive Control of Irregular 3D Frames Using Friction Dampers

This chapter presents a simple performance-based design methodology of an analysis/redesign type for sizing and allocating friction dampers within existing 3D irregular framed structures in order to control seismic performance. The methodology allows the determination of brace stiffness of all added damping devices, under a constant predetermined slip displacement, using analysis tools only. The methodology allows the design of an irregular framed structure of any type and is nondependent of the type of irregularity. Using this methodology, fully stressed design solutions are obtained in an example of a linear 3D setback frame undergoing an ensemble of ground motions.

Review of Structural Optimization

It is sad to state that today, after more than half a century since it has been formally introduced, structural optimization does not have a leading influential role in the daily activities of a busy design office, as does the finite element (FE) method for example. It is a discipline involving the synthesis and solution of design problems with defined objectives and constraints, through the implementation of a variety of iterative search techniques. Appealing as it might seem, it has not and cannot replace the designer’s creativity or his efficient conceptual designs. In structural engineering practice, where the designer is faced with endless sub-designs and alternatives, a fast and friendly tool that fits into the overall design philosophy of the office is essential. This is what the authors attempt to in their book: a design tool that does not overwhelm the designer but assists at critical stages of the design. Problems addressed by structural engineers are performance based, where the buildings are required to withstand severe and diverse loading conditions, such as earthquake, high wind and blast with imposed overall, inter-storey and elemental level constraints. These constraints may include limits on drift, acceleration, roof displacement, vibration, overall stability, etc. as well as ductility demands, stress and local buckling. Topology and geometry are side issues that are tackled at the architectural level and engineering conceptual design. The ultimate design tool that integrates all levels is yet to emerge.