Quincy T. Ma

Comparative Life Cycle Analysis of Conventional and Base-Isolated Buildings

This paper presents a case study life cycle analysis of a conventional and base isolated steel braced frame office building. The case study focuses particularly on the effects of moat wall pounding and business interruption using the FEMA P-58 methodology. Analytical results suggest that the overall performance of the base isolated building is far superior to the conventional building but that expected financial losses in the isolated building become significant if structural pounding occurs. The cost-effectiveness of the isolation is found to be particularly sensitive to the ability of businesses to relocate quickly and effectively after a large earthquake.

Cyclic Testing of Reinforced Concrete Walls with Distributed Minimum Vertical Reinforcement

AbstractDuring the 2010/2011 Canterbury earthquakes in New Zealand, several reinforced concrete (RC) walls in multistory buildings formed only a limited number of cracks at the wall base with a fra...

Experimental Identification of the Dynamic Characteristics of a Flexible Rocking Structure

This article presents the results of free vibration and earthquake excitation tests to investigate the dynamic behavior of freely rocking flexible structures with different geometric and vibration characteristics. The primary objective of these tests was to identify the complex interaction of elasticity and rocking and discuss its salient effects on the rocking and vibration mode frequencies, shapes and excitation mechanisms. The variability of response is discussed, including critical investigation of the repeatability of the tests. It was found that the variability in energy dissipation and energy transfer to vibrations at impact may lead to significantly different responses to almost identical excitations.

Shake Table Testing of a Low Damage Steel Building with 2-4 Displacement Dependent (D3) Viscous Damper

To improve seismic structural performance, supplemental damping devices can be incorporated to absorb seismic response energy. The viscous fluid damper is a well-known solution. However, while they reduce displacement demand, they can increase overall base shear demand in nonlinear structures as they provide resistive forces in all four quadrants of force-displacement response. In contrast, Direction and Displacement Dependent (D3) viscous fluid dampers offer the opportunity to simultaneously reduce structural displacements and the total base-shear force as they only produce resistive forces in the second and fourth quadrants of a structural hysteresis plot. The research experimentally examines the response of a half-scale, 2-storey moment frame steel structure fitted with a 2-4 configuration D3 viscous fluid damper. The structure is also tested with conventional viscous dampers to establish a baseline response and enable comparison of results. Dynamic experimental tests are used to assesses the base shear, maximum drift and residual deformation under 5 different earthquakes (Northridge, Kobe, Christchurch (CCCC), Christchurch (CHHC), and Bam ground motion). Response metrics including base shear, the maximum structural displacement, and peak structural accelerations are used to quantify performance and to assess the response reductions achieved through the addition of dampers. It is concluded that only the 2-4 device is capable of providing concurrent reductions in all three of these structural response metrics.

Solution Strategies for Three Problems in Empirical Fragility Curve Derivation Using the Maximum Likelihood Method

Solution strategies are presented to address three potential problems in the empirical derivation of fragility functions from empirical data using the maximum likelihood method. The first strategy addresses the case of fragility curves that cross, the second strategy incorporates demand uncertainty in fragility derivation from post-earthquake reconnaissance data, and the third strategy provides a framework for the resolution of conflict between empirical data and expert opinions. The advantages and disadvantages of the proposed solution strategies are discussed and their use is demonstrated by way of suitable illustrative examples.

Solution to the PEER framing equations accounting for dependence of earthquake repair costs on the number of damaged components

Abstract An analytical framework is presented to account for repair cost dependence on the number of damaged components in assembly-based seismic performance assessments. The analytical framework is investigated specifically in comparison to prevailing methodologies, which are based on Monte Carlo simulation, in order to highlight their relative advantages and disadvantages. An illustrative example considering exterior glazing in a three-storey building is set out to demonstrate an application of the proposed method. Implementation of a fully analytical framework is found to be hindered by the correlation of demand parameters, for which Monte Carlo simulation remains an attractive solution. Adoption of first-order second-moment assumptions within the proposed framework increase computational speed but decrease accuracy in the assessment of building-level decision variables. A full first-order second-moment framework is set out with application to error propagation and parameter studies accounting for dependence on the number of damaged components.

REAL-TIME ERROR CORRECTION IN FAST PSEUDODYNAMIC TESTING: A NUMERICAL STUDY

Undershooting error is a common error in fast pseudodynamic (PSD) tests as a result of inherent actuator lag. This type of systematic error introduces energy into a system, which if not monitored or controlled, can result in test instability and causes the response to grow exponentially. This leads to premature termination of a test and unreliable result. By considering the systematic error as negative damping in a structure, this paper proposes an intuitive error-correction scheme to compensate for the error. The key to this scheme is the introduction of a variable amount of viscous damping at every integration time step during the pseudodynamic test. The amount of time-varying viscous damping is derived by equating the magnitude of the energy error with that dissipated by the introduced damping at every integration time step. The accuracy and simplicity of the proposed error-correction scheme is demonstrated through numerical simulations of a linear-elastic SDOF structure and a two DOF structure subjected to sinusoidal ground motions.