Alfredo H. Ang
Professor Emeritus, Civil & Environmental Engineering
The Henry Samueli School of Engineering
The Henry Samueli School of Engineering
PH.D., University of Illinois
University of California, Irvine
Mail Code: 2175
Irvine, CA 92697
Mail Code: 2175
Irvine, CA 92697
Research Interests
Structural and Earthquake Engineering, Risk and Reliability Analysis
Research Abstract
Methods for Reliability Analysis of Structural Systems
Investigator: A.H-S. Ang
Research Assistants: J-C. Lee and G. Wang
Support: National Science Foundation
The reliability of structural systems is formulated with the failure mode approach (FMA) and the stable configuration approach (SCA). Both methods are being investigated for respective effectiveness depending on the type of systems. Analytical and Monte Carlo simulation methods are being developed to evaluate the reliability of various types of structural systems. This includes the available variance-reduction sampling techniques, such as importance sampling and response surface methods. An adaptive Kernel method of importance sampling has been examined, including applications to random systems subjected to random process excitations.
Optimal Risk for Earthquake-Resistant Design
Investigator: A.H-S. Ang
Research Assistant: D. de Leon
Support: Mexican National Council for Research and Technology National Science Foundation
Safety or reliability of a structure against potential damage and collapse are of paramount concern in earthquake-resistant design. However, because it is prohibitive economically to design for absolute safety, some measure of risk has to be accepted. Moreover, since the occurrence of earthquakes is unpredictable in time and space, and the magnitude is random, the proper measure of risk has to be in terms of probability. Properly, therefore, the acceptable risk should take into account the seismic hazard of the site or region and the importance of a given structure or system. Moreover, the level of safety/reliability has to be considered with the life-cycle cost involved; that is, the determination of the acceptable risk for design requires a trade-off between safety and cost. The acceptable risk for aseismic design is being examined in the context of minimum life-cycle cost.
Safety and Performance Enhancement of Structures through Response Control
Investigator: A.H-S. Ang
Research Assistants: D. de Leon and P. Li
Support: National Science Foundation
Structural control technology, with either passive or active control system, can be a viable and effective alternative to conventional earthquake-resistant design for protection against seismic forces. The application of this technology, however, requires much more careful design of the complete system, and evaluations of its effectiveness and limitations. In particular, these evaluations should include the assessments of reliabilities against excessive damage and collapse under all possible earthquake intensities. In order to show its viability as an alternative to conventional design, the cost-effectiveness of structural control may be presented in terms of the potential reduction in life-cycle damage cost. These concerns apply to the design of new structures, as well as to the retrofitting of existing structures, for increased seismic protection. The effectiveness of structural control is being investigated in terms of possible enhancement of structural safety and increased reliability for damage prevention through appropriate control designs.
Seismic Reliability of Electric Power Transmission Systems
Investigators: A.H-S. Ang, J.A. Pires, R. Villaverde, and R. Schinzinger
Research Assistants: I. Yoshida and L. Nyirenda
Support: National Science Foundation
Electrical transmission equipment and facilities are vulnerable to seismic damage, particularly those in high-voltage transmission systems. Failure of a high-voltage facility, such as a substation, may cause major power blackout to a large area. Although it is not feasible economically to totally prevent damage to a transmission system in the event of a major earthquake, quantitative (probabilistic) information on the likelihood of different levels of damage and extent of affected areas under different intensities of earthquake would be valuable for determining needed upgrading of an existing system, for emergency planning and disaster reduction preparedness, or for designing future systems. A comprehensive method for evaluating the seismic reliability of electric power transmission systems is under development. The model provides probabilistic assessments of structural damage and abnormal power flow that can lead to power interruption in a transmission system under a given earthquake. Seismic capacities of electrical equipment are determined on the basis of available test data and simple modeling from which fragility curves of specific substations are developed. Earthquake ground motions are defined as stochastic processes. Probabilities of network disconnectivity and abnormal power flow are assessed through Monte Carlo simulations. The proposed model has been applied to the electric power network in San Francisco and its vicinity under the 1989 Loma Prieta earthquake, and the probabilities of power interruption have been examined in light of the actual power failures observed during that earthquake.
Investigator: A.H-S. Ang
Research Assistants: J-C. Lee and G. Wang
Support: National Science Foundation
The reliability of structural systems is formulated with the failure mode approach (FMA) and the stable configuration approach (SCA). Both methods are being investigated for respective effectiveness depending on the type of systems. Analytical and Monte Carlo simulation methods are being developed to evaluate the reliability of various types of structural systems. This includes the available variance-reduction sampling techniques, such as importance sampling and response surface methods. An adaptive Kernel method of importance sampling has been examined, including applications to random systems subjected to random process excitations.
Optimal Risk for Earthquake-Resistant Design
Investigator: A.H-S. Ang
Research Assistant: D. de Leon
Support: Mexican National Council for Research and Technology National Science Foundation
Safety or reliability of a structure against potential damage and collapse are of paramount concern in earthquake-resistant design. However, because it is prohibitive economically to design for absolute safety, some measure of risk has to be accepted. Moreover, since the occurrence of earthquakes is unpredictable in time and space, and the magnitude is random, the proper measure of risk has to be in terms of probability. Properly, therefore, the acceptable risk should take into account the seismic hazard of the site or region and the importance of a given structure or system. Moreover, the level of safety/reliability has to be considered with the life-cycle cost involved; that is, the determination of the acceptable risk for design requires a trade-off between safety and cost. The acceptable risk for aseismic design is being examined in the context of minimum life-cycle cost.
Safety and Performance Enhancement of Structures through Response Control
Investigator: A.H-S. Ang
Research Assistants: D. de Leon and P. Li
Support: National Science Foundation
Structural control technology, with either passive or active control system, can be a viable and effective alternative to conventional earthquake-resistant design for protection against seismic forces. The application of this technology, however, requires much more careful design of the complete system, and evaluations of its effectiveness and limitations. In particular, these evaluations should include the assessments of reliabilities against excessive damage and collapse under all possible earthquake intensities. In order to show its viability as an alternative to conventional design, the cost-effectiveness of structural control may be presented in terms of the potential reduction in life-cycle damage cost. These concerns apply to the design of new structures, as well as to the retrofitting of existing structures, for increased seismic protection. The effectiveness of structural control is being investigated in terms of possible enhancement of structural safety and increased reliability for damage prevention through appropriate control designs.
Seismic Reliability of Electric Power Transmission Systems
Investigators: A.H-S. Ang, J.A. Pires, R. Villaverde, and R. Schinzinger
Research Assistants: I. Yoshida and L. Nyirenda
Support: National Science Foundation
Electrical transmission equipment and facilities are vulnerable to seismic damage, particularly those in high-voltage transmission systems. Failure of a high-voltage facility, such as a substation, may cause major power blackout to a large area. Although it is not feasible economically to totally prevent damage to a transmission system in the event of a major earthquake, quantitative (probabilistic) information on the likelihood of different levels of damage and extent of affected areas under different intensities of earthquake would be valuable for determining needed upgrading of an existing system, for emergency planning and disaster reduction preparedness, or for designing future systems. A comprehensive method for evaluating the seismic reliability of electric power transmission systems is under development. The model provides probabilistic assessments of structural damage and abnormal power flow that can lead to power interruption in a transmission system under a given earthquake. Seismic capacities of electrical equipment are determined on the basis of available test data and simple modeling from which fragility curves of specific substations are developed. Earthquake ground motions are defined as stochastic processes. Probabilities of network disconnectivity and abnormal power flow are assessed through Monte Carlo simulations. The proposed model has been applied to the electric power network in San Francisco and its vicinity under the 1989 Loma Prieta earthquake, and the probabilities of power interruption have been examined in light of the actual power failures observed during that earthquake.
Publications
"Basis for Cost-Effective Decisions on Upgrading Existing Structures for Earthquake Protection", Ang, A.H-S., US-China Sym. on Post-Earthquake Rehabilitation and Reconstruction, Kunming, China, May 1995
"Seismic Probabilistic Safety Assessment of Electrical Power Transmission Networks", Ang, A.H-S., Pires, J.A. and Villaverde, R., Int'l. Workshop on Risk & Reliability Analysis of Electrical Transmission Systems subjected to Seismic Events and Other Extreme Loads, Bergamo, Italy, June 1995
"Determination of Acceptable Limit-State Probabilities for Aseismic Design of R/C Buildings", Ang, A.H-S. and de Leon, D., 7th Int'l. Conf. on Applications of Statistics and Probability, Paris, France, July 1995
"Seismic Reliability of Slope Stability Considering Spatial Variability of Soil Properties", Seshimo, Y., Kubo, Y., Nishimura, Y., Annaka, T., Katayama, I. and Ang, A.H-S., 13th Int'l. Conf. on Structural Mechanics in Reactor Technology, Porto Alegre, Brazil, August 1995
"Systematic Approach for Determining Optimal Risks for Performance and Safety of Structures", Ang, A.H-S. and de Leon, D., 13th Int'l. Conf. on Structural Mechanics in Reactor Technology, Porto Alegre, Brazil, August, 1995
"Optimal Acceptable Risks for Aseismic Design of R/C Buildings", Ang, A.H-S. and de Leon, D., 13th Int'l. Conf. on Structural Mechanics in Reactor Technology, Porto Alegre, Brazil, August, 1995
Link to this profile
https://faculty.uci.edu/profile/?facultyId=2326
https://faculty.uci.edu/profile/?facultyId=2326
Last updated
01/08/2016
01/08/2016