Reliability Seminars are once-a-week gathering of students, visitors and faculty interested in probabilistic methods. Usually, a presentation is made by one of the participants, evoking comments and discussion during and after the presentation. Often the presentation is tentative and on a topic of ongoing research, rather than a finished and polished work. As a result, participants become acquainted with each others' current work and the presenter benefits from the discussion of his/her on-going research. Announcements for these seminars are posted here and sent to an e-mail listing. If you wish to be included in the e-mail listing, please send a message to adk@ce.berkeley.edu.

Date: Thursday, October 9, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: An Alternative Response Surface Methodology
Speaker: Umberto Alibrandi
Abstract: In order to reduce the computational costs in structural reliability analysis of complex systems it has been suggested to use Response Surface Methods (RSM). The basic idea is to replace the original performance function by a simple and approximate explicit function, named Response Surface (RS), whose function values can be computed more easily. However, it has been shown that the usually adopted Quadratic RS (QRS) may give results which are very sensitive to the experimental plan. This drawback is overcome by the Support Vector Method (SVM), which guarantees good robustness properties, but not fast convergence towards the exact limit state surface. An alternative RSM, called Kernel Response Surface (KRS), is proposed in this talk. KRS provides a trade-off solution between the QRS and the SVM. Some simple numerical examples show the accuracy and effectiveness of the proposed procedure.

Date: Thursday, October 2, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Estimating the response of long period structures with closely spaced modes to near-field ground motion
Speaker: Jyothi Krishnan
Abstract: Response of long period structures very close to earthquake faults is currently estimated using the CQC modal combination rule. Near-fault motions are highly non-stationary (of shorter duration compared to structure period and containing pulses of particular frequencies). This violates the basic assumptions behind the CQC rule. In this seminar a procedure to estimate response to near-field ground motion as a combination of response to an extracted pulse and to the residual broad-band motion is presented. The method will then be applied to two structures designed such that their response is not modeled well by the CQC rule.

Date: Thursday, September 25, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Modeling the quality of inspections for spatially distributed defects
Speaker: Daniel Straub
Abstract: A quantitative inspection model describes the ability of an inspection method to identify and characterize defects. Available inspection models, such as Probability of Detection (PoD), assume that the potential location of the defect is known. For many deterioration mechanisms in engineering systems, notably localized corrosion in pressure vessels and pipelines, the assumption does not hold. This presentation introduces a model of inspection quality that relaxes this assumption, based on a simplified spatial model of defect distribution. The model is validated numerically, using simulated defects. To facilitate reliability updating following an inspection, a generic limit state function for inspection outcomes is introduced. Finally, application of the model in reliability updating is demonstrated, considering inspections of deteriorating pipelines.

Date: Thursday, September 11, 2008
Time: 3:30-4:30 PM
Place: 542 Davis Hall
Title: Development of Future Aircraft Structural Engineers: Today's Cutting Edge, Tomorrow's Old School
Speaker: Michael Mohaghegh
Abstract: Advanced materials, designs, and computational methods used on development of future aircraft require structural engineers that have the latest competencie in these areas. Be prepared to stay ahead of the curve in your career. Come to hear about the multiple programs offered at Boeing to develop world class aircraft structural engineers working in a cntinuous learning environment.

Date: Thursday, September 4, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Seismic Response Analysis of a Bridge Crossing a Fault
Speaker: Katerina Konakli
Abstract: My study of structural response to spatially varying ground motions, in this seminar, is specialized on bridges crossing fault rupture zones. After a brief discussion of the characteristics of near-fault seismic motions, we will look into the response of an existing bridge designed by Caltrans. The ability of the Multiple Support Response Spectrum (MSRS) method to predict the structural response for the specific case of spatial variability is assessed. The analysis method proposed by Chopra and Goel (2008) for bridges crossing faults is also discussed.

Date: Thursday, August 28, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Likelihood estimation of parameters using simultaneously monitored processes
Speaker: Peter Friis-Hansen
Abstract: The topic of my talk in the reliability seminar is on maximum likelihood inference from several simultaneously monitored response processes of a structure to obtain knowledge about the parameters of other not monitored but important response processes when the structure is subject to some Gaussian load field in space and time. The considered example is a ship sailing with a given speed through a Gaussian wave field.

Date: Thursday, August 14, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Application of the Bucket Elimination algorithm to a BN for seismic infrastructure risk management
Speaker: Michelle Bensi
Abstract: In previous seminars, the application of Bayesian networks to seismic infrastructure risk management and the associated challenges were discussed. One of these challenges involved the lack of computational efficiency and tractability associated with many of the available inference algorithms. Without an efficient inference algorithm, the proposed model would be rendered useless. In this seminar, the Bucket Elimination algorithm, and the associated computational complexity, will be presented. In addition to providing an explanation of the algorithm, time will be spent discussing why and how this algorithm can be applied to the proposed BN.

Date: Tuesday, July 29, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Generating artificial ground motions for use in PBEE
Speaker: Sanaz Rezaeian
Abstract: A nonstationary stochastic model of strong ground motions, discussed in previous seminars, is used to simulate accelerograms, given only a set of earthquake and site characteristics (i.e. type of faulting, magnitude, distance from fault, and soil conditions), without any need for a previously recorded earthquake in the region. Such a model facilitates generating a suit of artificial ground motions that is appropriate for use in performance-based earthquake engineering (PBEE). The focus of this seminar is to investigate relations that will help us to predict the model parameters for a given set of earthquake and site characteristics. To develop such predictive relations, model parameters are identified for a data-set of strong ground motion recordings, statistical data analysis is performed, and some preliminary results, including fitted distributions of the model parameters and the correlations between parameters are presented.

Date: Tuesday, June 24, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Berkeley revisited
Speaker: Daniel Straub
Abstract: I will look back at my last two years spent at Berkeley and review my main findings and some trivia. To end my postdoc time on a sweet note, for once this presentation will contain more pictures than equations and I will also provide some dessert.

Date: Tuesday, June 10, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Multiple support response spectrum analysis of bridges III
Speaker: Katerina Konakli
Abstract: In this seminar we will look into the effect of ground motion spatial variability on an existing bridge structure designed by Caltrans. The efficiency of the improved MSRS method that accounts for high-frequency modes will be discussed. Finally, we will focus on the site-response effect of the coherency function and compare two different models for the frequency-response function of a soil column.

Date: Tuesday, June 3, 2008
Time: 3:30-4:30 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: TELM at sea: an application to an offshore structure - part II
Speaker: Luca Garre
Abstract: In this talk I will address the derivation of an alternative TELM model defined in the frequency domain. The new Tail Equivalent Linearized System (TELS) is defined through a Frequency Response Function (FRF), which is directly computed in terms of the gradient of the limit state function. An analytical derivation of the FRF will be presented, together with a more intuitive geometrical approach. I will present some first results with attention to invariance of the FRF with respect to the scaling and, to a lesser extent, the spectral shape of the excitation.

Date: Tuesday, May 27, 2008
Time: 4-5 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Enhancing Seismic Hazard Assessment with Machine Learning: Applications of Bayesian Networks and Support Vector Machines
Speaker: Michelle Bensi
Abstract: Machine learning is concerned with the development and use of algorithms that allow computers to “learn.” That is, the algorithms improve automatically (based on computational and statistical methods) through experience. Machine learning encompasses a wide range of topics and this seminar will focus on two of these topics: Bayesian Networks and Support Vector Machines (SVMs). This will be a two part seminar. The first portion will focus on the application of Bayesian Networks to the spatial modeling of earthquake hazard and infrastructure system performance (recently presented at: Inaugural International Conference of the Engineering Mechanics Institute). The second portion will focus on prediction of ground motion intensity (specifically whether intensity exceeds a specified threshold) using SVMs and logistic regression. In addition to providing a brief background on SVMs, results from SVMs and logistic regression will be compared with predictions from two attenuation relations.

Date: Tuesday, May 13, 2008
Time: 4-5 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Stochastic modeling of deterioration processes through dynamic Bayesian networks
Speaker: Daniel Straub
Abstract: A generic framework for stochastic modeling of deterioration processes is proposed, based on dynamic Bayesian networks (DBN), which can be interpreted as a generalization of Markov chain models. The framework facilitates computationally efficient and robust reliability analysis and, in particular, Bayesian updating of the deterioration models with measurements, monitoring and inspection results. These properties make it ideally suited for near-real time applications in asset integrity management and deterioration control. The framework is demonstrated and investigated through two examples considering fatigue crack growth.

Date: Tuesday, May 6, 2008
Time: 4-5 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Statistical approach for evaluation of identified vibration properties of a long-span bridge using a wireless sensor network
Speaker: Shamim Pakzad
Abstract: A wireless sensor network for structural monitoring applications is designed and developed with the goal of deployment of a scalable network with high data quality on a large infrastructure. The scalability of the network in terms of the number of nodes is provided by implementation of a novel pipelining technique for reliable dissemination of commands and data collection. The scalability in terms of the quality of the vibration data is provided by achieving time synchronization for sampling rates of up to 5 kHz, and sensitivity for a broad range of accelerations from low-level ambient vibrations to high-level earthquake motions. During the three months test deployment of the network on the Golden Gate Bridge, independent of the number of the nodes, a steady communication bandwidth of 550 bytes per second was maintained. Using the ambient vibration data collected by the network, the vibration modes of the bridge, including higher modes of up to 5 Hz frequency, with a high degree of confidence were identified. Distribution properties of the modes were estimated and a statistical platform for evaluating the accuracy of the identified parameters was used. This integrated approach to hardware architecture, system software, and statistical system identification is required for achieving wireless sensor networks with high spatial density and data quality that can be effectively utilized for health monitoring of infrastructures.

Date: Tuesday, April 29, 2008
Time: 4-5 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: FORM in high dimensions
Speaker: Armen Der Kiureghian
Abstract: Some researchers have recently criticized applications of the first-order reliability method to problems with large numbers of random variables. One such application area is nonlinear stochastic dynamic analysis by FORM, which requires discrete representation of the excitation by a large number of random variables. This issue will be revisited in this presentation with special focus on nonlinear stochastic dynamic analysis by the Tail-Equivalent Linearization Method, TELM.

Date: Tuesday, April 22, 2008
Time: 4-5 PM
Place: PEER Center Conference Room (325 Davis Hall)
Title: Attenuation of Inelastic Response Spectra
Speaker: Yousef Bozorgnia
Abstract: Practical seismic hazard analysis is almost universally carried out for peak ground motion values and linear elastic response spectra. During a severe ground shaking, however, many structures behave inelastically. In order to carry out a direct hazard analysis on other intensity measures (IMs) such as inelastic response spectra, attenuation models for the new IM have to be developed. In this study:
-- Inelastic response spectra for thousands of recorded ground motions compiled in PEER NGA database are computed,
-- Attenuation models for inelastic response spectral ordinates are developed, and
-- The inelastic attenuation models are used to perform direct probabilistic seismic hazard analysis (PSHA) on inelastic response spectra.
An advantage of this process is that no assumption is made about estimating inelastic response from elastic response spectra, as the new attenuation models are directly developed based on inelastic spectral ordinates. Also, the new attenuation models are easily implemented into a standard PSHA package--in this case, open-source OpenSHA software developed by the USGS.

Date: Tuesday, April 15, 2008
Time: 4-5 PM
Place: PEER Center Conference Room
Title: TELM at sea: an application of the Tail Equivalent Linearization Method to an offshore structure
Speaker: Luca Garre
Abstract: The talk will deal with random vibrations analysis of offshore structures. Focusing on a given offshore platform I will present the following topics:
-- Linear Airy theory for sea waves kinematics;
-- Structural and loading (Morison's equation) models employed in the analysis;
-- FORM analysis for the most probable excitation leading to exceedance of a given treshold at a given time;
-- Computational problems arising with the TELM procedure in connection with excitations defined in the frequency domain;
-- A possible approach to overcome the problems and some preliminary considerations.

Date: Tuesday, April 8, 2008
Time: 4-5 PM
Place: PEER Center Conference Room
Title: New developments on a stochastic ground motion model & its application in Earthquake Engineering
Speaker: Sanaz Rezaeian
Abstract: Stochastic ground motion models are needed in the current practice of performance-based earthquake engineering (PBEE). These models enable engineers to generate artificial samples of ground motions, which can be used in the place of actually recorded accelerograms when the scarcity of recorded earthquakes in a region causes difficulty in selecting an appropriate suite of ground motions.

Many stochastic ground motion models have been proposed, but the task of selecting an appropriate set of model parameters for a site of interest remains unresolved. The goal of this seminar is to discuss constructing distribution models for the stochastic model parameters and formulating correlations between these parameters and the earthquake and site characteristics by performing statistical analysis on a large number of recorded ground motions.

Date: Tuesday, April 1, 2008
Time: 4-5 PM
Place: 721A Davis Hall
Title: Information Updating in Infrastructure Systems Subject to Multiple Hazards
Speaker: Daniel Straub
Abstract: A main difficulty in managing infrastructure subject to multiple hazards is the large uncertainty associated with engineering models of the hazards, infrastructure response and the societal demand on the infrastructure. Any attempt to optimize hazard mitigation and recovery must account for these uncertainties, ideally through a probabilistic assessment. On the other hand, with the developments and increased availability of IT and measurement technology (e.g., remote sensors or GPS), more and more information on the hazards, the infrastructure condition and the system demand are readily available. Information reduces uncertainty in our models and in doing so supports the identification of optimal decisions. Therefore, there is a huge potential for computationally efficient methods for updating of the probabilistic models under new evidence. This presentation will present examples of how this is done and it will outline how these methods can be integrated into a new generation of decision support systems.

The presentation will start by discussing challenges involved in safeguarding infrastructure from multiple hazards. The Bayesian network methodology as a tool for jointly representing and analyzing multiple hazards will be introduced, and it will be demonstrated how this methodology can efficiently perform information updating under new evidence. The use of the methodology for optimizing decisions regarding hazard prevention, protection systems, early warning, inspection and control, as well as recovery, will be outlined. The concepts and mathematical tools will be illustrated by examples considering avalanche, earthquake, rock-fall and deterioration of infrastructures from the academic and industrial experience of the speaker.

Date: Tuesday, March 11, 2008
Time: 4-5 PM
Place: 721A Davis Hall
Title: Reliability-based demand analysis of structures subjected to ground shaking
Speaker: Marcello Bianchini
Abstract: The correct assessment of different performance levels of nonlinear modeled structures represents one of the most significant goals in the field of earthquake engineering. Starting from the expression for the classical time-independent reliability formulation, and under a few established assumptions, the probability of exceeding a specified performance level can be written in a closed form. The method represents a specific application of the Probabilistic Seismic Demand Analysis (PSDA), defined in the PEER loss estimation framework. For a given structure in a known seismic environment, the definition of which Intensity Measure (IM) plays a leading role in the whole process. In fact, the ground motion IM defines the seismic hazard at the site and it can be used as scale factor of records in incremental dynamic analysis to assess the fragility functions. A generic IM must satisfy some desirable properties in order to obtain reliable results. An average of spectral accelerations over a certain range of periods is first studied as a statistical predictor of nonlinear structural response of buildings subjected to recorded ground motions, and second compared with traditional elastic and inelastic scalar IMs. Finally, for a set of RC frame structures, which have been designed according to Eurocode 8 and capacity design criteria, PSDA is carried out combining the failure mechanisms, and the effectiveness of a well-selected IM is shown.

Date: Tuesday, March 4, 2008
Time: 4-5 PM
Place: 721A Davis Hall
Title: TELM analysis by FERUM and implementation of degrading materials
Speaker: Salvatore Sessa
Abstract: A new package for performing TELM analysis by FERUM will be presented together with an example application of an SODF oscillator used for testing the package. Furthermore, the seminar will present a generalized Bouc-Wen degrading material model and a first attempt at using it in conjunction with TELM.

Date: Tuesday, February 26, 2008
Time: 4-5 PM
Place: 721A Davis Hall
Title: More on the Application of Bayesian Networks to Seismic Hazard Assessment
Speaker: Michelle Bensi
Abstract: In a previous seminar, the application of graphical models, specifically Bayesian Networks, to seismic hazard assessment was discussed. That presentation focused particularly on the inclusion of spatial error correlation and how the addition of this correlation can be modeled efficiently. This seminar will continue with the discussion of these issues and expand upon the application of aforementioned ideas for actual modeling. An example of a simple spatially distributed system will be presented.

Date: Tuesday, February 12, 2008
Time: 4-5 PM
Place: 721A Davis Hall
Title: Multiple support response spectrum analysis of bridges
Speaker: Katerina Konakli
Abstract: Continuing the study of structural response to differential support motions, we use a more refined model that accounts for three-dimensional ground excitation and includes the site response effect in the coherency function. Furthermore, we discuss the question of how many modes need to be used in the analysis. Finally, we investigate the specific case of a bridge crossing the fault: the coherency function and the structural response are evaluated for various orientations of the bridge model.

Date: Tuesday, February 5, 2008
Time: 4-5 PM
Place: 721A Davis Hall
Title: Modeling deterioration and optimizing inspection efforts in spatially distributed systems - the example of corrosion in large RC structures
Speaker: Daniel Straub
Abstract: I will present an overview on the probabilistic modeling of corrosion of the reinforcement in concrete structures, with emphasis on the aspects of spatial variability. A hierarchical model is introduced for representing these spatial aspects. The model is then applied for optimizing inspection and maintenance efforts in large concrete structures. This presentation is based on earlier work (http://www.informaworld.com/10.1080/15732470601017369) but here the methods and results are discussed in light of Bayesian network models that we are currently working on.

Date: Tuesday, January 29, 2008
Time: 4-5 PM
Place: 721A Davis Hall
Title: The Model Correction Factor Method: an efficient response surface technique
Speaker: Luca Garre
Abstract: Structural reliability analysis (SRA) makes use of so-called Response Surface Methods (RSMs) for the solution of the reliability problem in the case of difficult-to-solve structural analyses. One of such analyses could be the assessment of buckling or ultimate resistance of bi-axially loaded steel stiffened plates, as it is the case in ship engineering practice. In these nonlinear cases, the computation of the structural response might be difficult, and integration of the structural code into the SRA algorithm is uneasy or simply impossible. Therefore, RSMs aim at defining an alternative limit state surface to be introduced into the SRA procedure by a sequence of repetitive calls to the structural code, according to a somehow defined grid of points in the space of the random variables.
In this presentation I will discuss about a particular response surface technique, the so- called Model Correction Factor Method (MCFM). According to this method, a simplified and easy-to-solve formulation of the problem at hand is employed as the limit state function. Such a code is then calibrated to a more advanced and realistic one (such as FEM) in a probabilistic sense, as the calibration is performed around the design point resulting from application of the SRA algorithm with the simplified limit state function. After a limited number of such adaptive calibrations the series of design points converges.
After a brief introduction to the procedural background of the method, I will show an application of this procedure to a typical marine problem, defined by a stiffened bottom plate subjected to both lateral and axial loads.

Date: Wednesday, December 12, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Application of Bayesian Networks to Seismic Hazard Assessment
Speaker: Michelle Bensi
Abstract: The assessment of seismic risk has become increasingly common in the field of earthquake engineering where there is interest in determining the hazard associated with a future earthquake of random characteristics (e.g. magnitude and location) at a site. This presentation will discuss the application of graphical models to seismic hazard analysis. Graphical models, specifically Bayesian Networks, are a favorable way to model seismic hazard because they allow for ease in updating the model as additional information becomes available.

Specifically, this presentation will focus on examining the importance of including spatial correlation of attenuation relation error terms when predicting spectral acceleration at a site using a graphical model approach. Additionally, this report will consider the effect of approximating this correlation by clustering correlation into geographically discrete segments in the spatial domain to increase computational efficiency. The goal of this report is to understand the ‘trade-off’ between including spatial correlations versus the reduction in computational efficiency its inclusion creates.

Date: Wednesday, December 5, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Nonlinear Random Vibration Analysis by using TELM in OpenSees
Speaker: Sanaz Rezaeian, Salvatore Sessa
Abstract: In the previous seminar, we talked briefly about the reliability and TELM (tail equivalent linearization method) modules in OpenSees. In this seminar, we will use the results of the TELS (tail equivalent linear system) obtained from OpenSees to analyze the behavior of the system subjected to stationary and non-stationary excitations. Sample results for a SDOF system and a MDOF system (truss structure) will be presented.

Date: Wednesday, November 28, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: The effect of structural redundancy on the acceptability of deterioration
Speaker: Daniel Straub
Abstract: Criteria for the acceptability of deterioration in structures are required to determine and document the appropriateness of mitigation actions such as design provisions, maintenance, retrofit and inspections. Because deterioration is modeled at the level of structural elements, these criteria must also be formulated at the element level, and, therefore, should account for the structural importance of the elements. However, for redundant structural systems, the quantification and application of such criteria has been hindered in the past by the difficulties involved in the reliability analyses of such systems. I present a method for establishing reliability acceptance criteria for deterioration in elements of redundant structural systems based on overall acceptance criteria on the system level. The proposed method utilizes equivalent structural systems that facilitate reliability analysis. These equivalent structural systems are established by calibrating them to characteristics of the real structure, which include a) the reliability of the structure without deterioration, b) indicators for the redundancy of the structure with respect to deterioration failure of individual elements, and c) estimates of the statistical dependence among deterioration at different locations in the structure. I will conclude the presentation by numerical examples demonstrating the effect of structural redundancy on the target reliabilities of structural elements.

Date: Wednesday, November 14, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Modal combination rules for response spectrum analysis of bridges
Speaker: Armen Der Kiureghian
Abstract: Several response spectrum methods for seismic analysis of bridges will be reviewed. Consideration will be given to multi-component support motions, interacting vector responses, and spatial variability.

Date: Wednesday, November 7, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Seismic Damage and Loss Models for Reinforced Concrete Bridges
Speaker: John-Michael Wong
Abstract: Post-earthquake repair costs are important for evaluating the performance of new bridge design options and existing bridge configurations. A step-by-step probabilistic repair cost methodology is proposed to evaluate the cost of repairs for bridge components and the bridge as a system for varying degrees of damage. This seminar will demonstrate an application of this methodology for evaluating column design options and earthquake damage scenarios on a reinforced concrete bridge in California.

Date: Wednesday, October 31, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Multiple support response spectrum analysis of bridges
Speaker: Katerina Konakli
Abstract: In this seminar, first, we briefly review the response spectrum method for multi-support seismic excitations and the extended method that accounts for the quasi-static contribution of truncated modes. We continue by presenting a parametric study of the correlation coefficients introduced in the extended method. The improvement by accounting for quasi-static contributions is examined for an example bridge structure. Finally, we introduce a coherency function that accounts for near-field effects and examine the structural response of an example bridge crossing the fault.

Date: Wednesday, October 24, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Design of reinforced concrete buildings by seismic envelopes
Speaker: Salvatore Sessa
Abstract: It will be shown a brief review about rectangular and supreme envelopes after a FEM modal analysis. A line search Newton-Raphson algorithm is used for evaluating the capacity domain edge and the forces' critical multiplier. The methods has been implemented in a software and it will be presented a complete seismic analysis of a strategic building following the EC8 code. It is possible to make a comparison between the results of the methods and qualitative consideration about the convergence behavior. Future work directions' hypothesis will be presented.

Date: Wednesday, October 3, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Random Vibration and Reliability Analysis in OpenSees
Speaker: Sanaz Rezaeian, Salvatore Sessa
Abstract: The purpose of this seminar is to present a brief orientation to the reliability module in OpenSees, and particularly focus on a newly developed sub-module called TELM (tail equivalent linearization method) that facilitates nonlinear random vibration analysis. To achieve this goal, first we will discuss the modeling process, choosing the excitation, and analysis possibilities in OpenSees. For random vibration analysis, OpenSees is used to obtain the necessary data (e.g. design points, TELSs,...), then matlab programs are used to perform linear random vibration analysis using the corresponding data. Several examples, including SDOF and MDOF systems excited by stationary and non-stationary processes, are presented to demonstrate the capabilities of this software.

Date: Wednesday, September 19, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Reliability Analysis and Design of Transmission Line Towers
Speaker: Jyothi Krishnan
Abstract: The seminar presents an assessment of the reliability index of tangent transmission line towers designed in accordance with current practice. Target safety factors, based on location of the tower and its importance, are recommended and effective wind load factors proposed to achieve these targets.

Date: Wednesday, September 12, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Multiple-support response-spectrum analysis of bridges
Speaker: Katerina Konakli
Abstract: This seminar will present a response spectrum method for seismic analysis of linear structures subjected to differential support motions, which is based on fundamental principles of random vibration theory. The original method is extended to account for the quasi-static contribution of truncated modes. A simple bridge model is considered to demonstrate the influence of spatial variability of the ground motion on selected response quantities.

Date: Wednesday, September 5, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: Applicability of push-over analysis to plan irregular building structures
Speaker: Mario De Stefano
Abstract: As consequence of the increasing popularity of simplified non linear methods in seismic design, recently many procedures have been proposed aimed at extending push-over analysis to plan asymmetric structures. In particular, it appears very promising for practical purposes the approach based on combining pushover analysis of a 3D structural model with the results of a linear (modal) dynamic analysis. Nevertheless, a fundamental requirement for its effectiveness is that the elastic prediction of the envelope of lateral displacements be conservative with respect to the actual inelastic one. This reserch is aimed at verifying the above assumption with reference to both frame building structures and shear-wall ones. An extensive parametric analysis is conducted with simplified single-storey models by varying the main structural parameters that influence torsional response in the elastic and inelastic range of behaviour. It is found that the method is in general suitable for frame structures but it can not be recommended for shear-wall building structures, as their inelastic torsional response almost always exceeds the elastic one.

Date: Wednesday, August 29, 2007
Time: 12-1 PM
Place: 721A Davis Hall
Title: ICASP10 and Japan: a pictorial review
Speaker: Michelle Bensi and Sanaz Rezaeian
Abstract: The authors recently returned from Japan, where they attended the 10th International Conference on Applications of Statistics and Probability in Civil Engineering. In this seminar, they will make a review of their experiences in the conference and Japan by use of (a small fraction!) of their digital pictures.

Date: Thursday, July 26, 2007
Time: 11AM-12PM
Place: 721A Davis Hall
Title: Methods for reliability estimation and applications using FERUM: from FORM to MC-like simulation
Speaker: Jean-Marc Bourinet
Abstract: The presentation will provide an overview of a recent method developed at IFMA in France, improvements brought to existing methods and their implementations within FERUM. A snapshot of classical methods available within the FERUM version under development at IFMA will be given, including FORM and IS for multiple design points, subset simulation method, RBDO. A particular attention will also be paid to the calculation of FORM sensitivities, with respect to distribution parameters including correlation. A new method combining the subset simulation concept and a Support Vector Machines (SVM) learning method will also be detailed. This method addresses challenging problems, including system time invariant reliability problems and problems with a moderately large number of random variables (up to a few hundreds). Examples of applications will be presented, including recent FE based works on multiple crack propagation and buckling of imperfect shells. The presentation will also give a few details on FERUM capabilities for handling distributed computing on multi-processor computer platform and calling external FE codes.

Date: Monday, July 23, 2007
Time: 11AM-12PM
Place: 542 Davis Hall
Title: Application of Bayesian networks for seismic risk analysis
Speaker: Michelle Bensi & Daniel Straub
Abstract: The presentation shortly reviews a new framework for including structural reliability methods into Bayesian networks for modeling large and complex engineering systems. We will then focus on an example of seismic risk analysis of infrastructure systems, and in particular on the modeling of spatial and statistical dependences. The example will highlight the potential as well as the limitations of the new framework.

Date: Monday, July 16, 2007
Time: 11AM-12PM
Place: 721A Davis Hall
Title: New developments on a stochastic model for strong earthquake ground motion
Speaker: Sanaz Rezaeian
Abstract: Previously we discussed the development of a discrete and fully nonstationary model for strong earthquake ground motions. The model employs filtering of a discretized white-noise process and is fitted to target ground motions by matching a set of statistical characteristics. In this seminar we will look at the adequacy of ground motion models from a structural response point of view and will compare the response spectra computed from the simulated and target accelerograms.

Date: Monday July 9, 2007
Time: 11AM-12PM
Place: 721A Davis Hall
Title: Seismic critical response of polygonal reinforced-concrete sections
Speaker: Salvatore Sessa
Abstract: Seismic envelopes and iterative methods are combined to compute the ultimate strength of reinforced concrete sections. The results of preliminary testing are reported and investigation about the convergence of the algorithm is developed.

Date: Monday, July 2, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Enhancing Bayesian Networks using Structural Reliability Methods
Speaker: Daniel Straub
Abstract: An overview on ongoing research on combining Bayesian networks with Structural Reliability Methods is presented. The results of some preliminary investigations are reported and the potential as well as the limitations of such an approach for risk analysis of civil systems are discussed.

Date: Thursday, May 24, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Fire Risk Analysis by the Account Fire Model
Speaker: Kazuya Fujimura
Abstract: The Account Fire Model (AFM), which is being developed by Risk Management Solutions (RMS), will be discussed. The AFM provides the risk manager a view of risk that incorporates the probability of experiencing a range of losses from fire events, taking into consideration key characteristics that determine the extent of fire spread. The AFM uses a hybrid statistical and physical fire model designed to inform the primary insurance underwriting process, as well as facultative and treaty reinsurance management, and business continuity planning. With the AFM, Decision makers can be provided with risk metrics yielding an informed basis for pricing risk transfer, as well as evaluating the cost-benefit of capital investment to mitigate risk. Overview of physical fire modeling as well as statistical methods used in the AFM will be presented.

Date: Thursday, May 17, 2007
Time: 11AM-12PM
Place: 721A Davis Hall
Title: Bayesian methods in risk assessments for natural hazards
Speaker: Daniel Straub
Abstract: Bayesian methods are particularly useful in risk assessments when little information on the considered processes is available and when information changes with time, e.g., for weather-related events. These conditions are often encountered when modeling risks related to natural hazards. In this presentation, the fundamental principles of Bayesian methods and Bayesian networks will be reviewed and the possibilities of Bayesian networks as well as their limitations will be demonstrated by means of simple examples and illustrated by an overview on past and ongoing research and consulting projects that use Bayesian networks as a tool for natural hazard risk assessments.

Date: Thursday, May 10, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Probability Density Evolution Method for Stochastic Mechanics
Speaker: Jianbing Chen
Abstract: Stochastic mechanics, which deals with randomness involved in excitations and structural properties of engineering systems, has gained increasing interest in the past decades. While a variety of valuable contributions have been made in some important aspects, the approach applicable to multi-degree-of-freedom nonlinear structural or mechanical systems has not been available as yet. The presentation will deal with a newly developed probability density evolution method. The principle of preservation of probability is revisited from the standpoint of state space description and random event description. Based on the random event description (Lagrangian description), a partial differential equation governing evolution of the one- or any arbitrary- dimensional joint probability density function can be established. Numerically solving this equation combining deterministic dynamic analysis with the finite difference method will yield instantaneous probability density function of any arbitrary response of interest. The probability density evolution method can be applied to static and dynamic stochastic response analysis of linear and nonlinear structures, dynamic reliability evaluation and system reliability evaluation, etc. Some key problems needing further investigations are discussed.

Date: Thursday, April 26, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Airport Availability Modeling: A Different Perspective
Speaker: Jasenka Rakas
Abstract: This study proposes a systems-level approach to airport and runway availability assessments and prediction, and addresses the problem of the aging or continuously degrading aviation infrastructure.
Although the availability block diagrams are often used in the availability assessment of aerospace and electronic systems, their application to the airport availability problem on a system-level, developed in this study, is novel.  The proposed methodology is intended for short-term and long-term planning of the communication, navigation and surveillance (CNS) equipment acquisition, and investment and modernization decisions.
Improved understanding of the effects of equipment outages on airport availability is important in determining a required level of airport equipage and equipment reliability, particularly during critical operating conditions such as bad weather and increased traffic demand.  With proposed methodology an analyst can precisely quantify the additional level of airport availability achieved by upgrading or adding new pieces of CNS equipment.

Date: Thursday, April 12, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Aleatory or epistemic? Does it matter?
Speaker: Armen Der Kiureghian
Abstract: The sources and characterization of uncertainties in engineering modeling for risk and reliability analyses are discussed. While many sources of uncertainty may exist, they are generally categorized as either aleatory or epistemic. Uncertainties are characterized as epistemic, if the modeler sees a possibility to reduce them by gathering more data or by refining models. Uncertainties are categorized as aleatory if the modeler does not foresee the possibility of reducing them. From a pragmatic standpoint, it is useful to categorize the uncertainties within a model, since it then becomes clear as to which uncertainties have the potential of being reduced. More importantly, epistemic uncertainties may introduce dependence between events, which may not be properly noted if their character is not correctly modeled. Influences of the two types of uncertainties in reliability assessment, codified design, performance-based engineering and risk-based decision-making are discussed. In particular, the influence of the dependence arising from epistemic uncertainties on systems and time-variant reliability problems are demonstrated through two examples.

Date: Thursday, April 5, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Random sideway sliding of unlashed truck on a ro-ro vessel
Speaker: Peter Friis-Hansen, Technical University of Denmark
Abstract: Trucks on a ro-ro vessel are usually parked in parallel lanes very close to each other. To prevent movements of the truck wheels these are under severe weather conditions lashed to the deck. However, this lashing does not prevent that the top of the truck can be excited to vibrate, in particular in the side direction. If of some reason a truck is not lashed to the deck it may on top of its vibrations slide intermittently sideways in a random way. Thus this truck may bump into a neighbor truck and cause damage.
In the presentation the model will be described where the considered truck is idealized as a plane two degrees of freedom vibrating container carried by springs and dampers on a rigid undercarriage. The deck is assumed to move as a rigid body with two degrees of freedom, heave and roll, that together are modeled as a stationary Gaussian vector process. The problem is analyzed by use of crossing theory and the Slepian model process concept under the assumption that sideway sliding happens sufficiently rarely for the theory to be applicable.

Date: Thursday, March 22, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Redundancy - je ne sais quoi?
Speaker: Charles Scawthorn, Kyoto University, Japan
Abstract: After a brief summary of activities at Kyoto University, the issue of lifeline and structural redundancy will be explored. Redundancy is of great value in achieving high reliability for networks and structures, yet is resistant to satisfactory quantification or even an adequate definition. Past research and definitions of lifeline and structural redundancy will be reviewed, followed by a summary of a recent (yet essentially inconclusive) research project.

Date: Thursday, March 15, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Reliability-based acceptance criteria for deterioration limit states
Speaker: Daniel Straub
Abstract: The presentation will provide an overview on the issues involved in determining acceptability of deterioration in structural systems. Many owners of existing structures are confronted with the problem of determining whether their structure and their integrity management can be considered acceptable – however, to date, satisfying methods for demonstrating acceptability of the risks associated with deterioration in structural systems exist only for few special cases. Therefore, such methods have a huge potential and the aim of this talk is to present a proposal for such a simple yet consistent method to determine reliability-based acceptance criteria for deterioration in structural systems. First, it will be outlined what distinguishes deterioration limit states from ultimate limit states (i.e., failure of structural elements due to static or dynamic over-loading of the structure). In particular, the system and the uncertainty modeling required to account for deterioration is fundamentally different, as will be demonstrated by numerical examples investigating the influence of various factors related to deterioration. Thereafter, it will be demonstrated how reliability-based acceptance criteria, which were developed for ultimate limit states and which have been successfully implemented in several codes, can be adopted for deterioration limit states.

Date: Thursday, March 8, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: An introduction to support vector machines (SVM)
Speaker: Gang Li
Abstract: On the basis of a few available samples, to assign a new sample to classes (labeled numerically or symbolically) or to estimate the functional dependency of some variables with respect to others is the common problem in many areas. The former is the classification problem and the latter is the regression problem. Statistical learning theory (SLT) developed in the last decades is a powerful in solving these types of problems, in which support vector machines (SVM) is a popular tool since 1990s. This presentation introduces some related topics, including three parts: basic concepts of statistical learning, elements of support vector machines and discussion on reliability analysis.

Date: March 1, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Probability-based vulnerability and criticality assessment of transportation infrastructure
Speaker: Michelle Bensi
Abstract: Recent events around the world have brought into light the need to understand and assess the vulnerability of civil infrastructure systems, specifically transportation infrastructure, to terrorist threats. While it has been accepted that large signature structures may be highly vulnerable as symbolic targets, an attack on a non-redundant, less visible link in an inventory such as a railway bridge or tunnel has the potential to cause substantial casualties as well as economic and social disruptions. It is not feasible to fortify and protect an entire inventory, and infrastructure owners must make decisions regarding how to best allocate their limited resources. This presentation will discuss the development of a probability-based method for quantifying the vulnerability of a public structure to attack and for ranking the criticality of a structure relative to the inventory by examining the consequences of an attack. Several illustrative case studies will be presented to demonstrate the methodology.

Date: February 8 and 15, 2007
Time: 1-2PM
Place: 721A Davis Hall
Title: Improved seismic fragility modeling from empirical data
Speaker: Daniel Straub
Abstract: The seminar presents the finalized version of the improved fragility model. The key feature of this model is that it accounts for statistical dependences among observations of seismic performances of system components, which have been neglected in past fragility analyses. As will be demonstrated by numerical examples considering seismic fragility of electrical substation equipment, the effect of this statistical dependence can be very large and must be considered when deriving fragility models from empirical data. The presentation concludes with an investigation of the effect of the model assumptions on the computed system fragility. It will be shown that the probability of system failure can change by orders of magnitude depending on the assumptions related to statistical dependences.

Date: February 1, 2007.
Title: New developments on a site-based fully nonstationary stochastic model for strong earthquake ground motion
Speaker: Sanaz Rezaeian
Abstract: In a previous seminar we discussed the development of a new discrete and fully nonstationary model for strong earthquake ground motions. The model employed filtering of a discretized white-noise process and was fitted to target ground motions by matching a set of statistical characteristics. In this seminar we will continue our discussion and will focus on the improvements that were made since last time. In particular, the topics of interest will be:
-Changes made to the form of the model and their advantages
-Modifications in parameter estimation when using statistical characteristics
-Ongoing developments on the weight functions in order to obtain a better fit of the actual recorded ground motion

Date: January 25, 2007.
Title: Dynamic optimal design for ice-resistant jacket platforms
Speaker: Gang Li
Abstract: The ice load is normally the dominant environmental force for offshore platforms in cold regions, which have to resist extreme static ice force and dynamic ice force. However, current design codes of ice-resistant structures only consider static ice forces. In recent years observations in Bohai Gulf showed that dynamic ice can induce significant vibrations, resulting in serious consequences. This presentation focuses on dynamic optimal design for ice-resistant jacket platforms, including the following two parts:
1) Minimum weight design of jacket platforms in consideration of fatigue life, in which a hybrid finite element model is adopted to simulate the jacket platform and the tubular joints, and the pseudo excitation method (PEM) is used to calculate the power spectral density of the hot spot stress.
2) Minimum dynamic response design of jacket platforms, in which a method is proposed to determine the most dangerous dynamic ice case in consideration of the randomness of ice thickness and velocity.

Date: December 6, 2006.
Title: Optimization of maintenance and replacement policies for a system of heterogeneous infrastructure facilities
Speaker: Samer Madanat
Abstract: This research addresses the determination of optimal maintenance and replacement policies for a system of heterogeneous facilities. The problem of optimizing maintenance and replacement policies at the system level is formulated in a reliability-based framework, based on policies that are optimal at the facility level. The facility-level policies are determined using a finite-state, finite horizon Markov decision process in which the state of the Markov chain contains information on the history of maintenance and deterioration.
Optimality conditions for the continuous-case system-level problem are derived and explained intuitively. A numerical study shows that the results obtained in the discrete-case implementation of the solution are valid approximations of the continuous-case results. The computational efficiency of the system-level solution makes the formulation suitable for systems of realistic sizes.

Date: November 29, 2006.
Title: Protecting Wetland Ecology by Using a Reliability-Optimization Framework to Manage Multiple Water Resources
Speaker: Chin Man Mok
Abstract: Tampa Bay Water is the largest wholesale water supply utility in Florida servicing the Northern Tampa Bay Tri-county area. To protect the wetlands and to prevent seawater intrusion while meeting the water demand of approximately two million people in the area, a reliability-based optimization framework was formulated for managing the available water resources from over 160 groundwater production wells in 12 inter-connected wellfields, 3 stream flow withdrawal facilities, a regional reservoir, and a desalination plant. The formulated framework computes the weekly groundwater production rates, surface water withdrawal rates, and reservoir water inflow/outflow rates that maximize the reliability of achieving healthy wetlands. The framework involves (1) a supply-system simulation model to represent the routing of available water resources, (2) Monte Carlo simulation models to generate conditional realizations of water demand and available surface water quantity based on a stochastic climatic model that accounts for the spatial and temporal characteristics, and (3) a stochastic unit response matrix (URM) model derived from a coupled HSPF surface water model and MODFLOW groundwater model that relates groundwater level response to groundwater extraction, and (4) a water-production operator simulator that mimic the response of the operators to meet the actual water demand in all circumstances. The reliability optimization problem is solved using a differential evolutionary (DE) algorithm.

Date: November 15, 2006.
Title: Seismic Risk Analysis of Buildings - source-focused formulation and business implementation
Speaker: Yuji Takahashi
Abstract: This seminar presents a source-focused formulation of seismic risk of buildings. In analyzing seismic risk, this equation enables to incorporate any renewal model, e.g. Poisson model, Brownian Passage Time model etc., for fault rupture occurrences. In addition, we can directly perform the end-to-end analysis from fault rupture to loss generation, and utilize simulation models developed in the related academic fields such as seismology, geotechnical engineering, and structural engineering.
In order to apply the proposed methodology to business, I launched and directed a cooperative research project that consists of twelve corporations. We developed commercial software for the risk analysis, and conducted case studies dealing with actual buildings. The case studies were performed based on two levels of the practical end-to-end analyses: time-history analysis and Capacity-Spectrum analysis. Some of the case studies are discussed in this presentation.
At the end of the presentation, I will briefly talk about my ongoing project entitled "Financial Technology to Promote Earthquake Preparedness in Buildings".

Date: October 18 and 25, November 1 and 8, 2006.
Title: A series of four lectures on: Introduction to Bayesian Networks for Engineering Risk Analysis
Speaker: Daniel Straub
Abstract: Bayesian networks (BN) are a highly efficient and intuitive tool to represent systems and processes subject to uncertainty. Because of their flexibility and computational efficiency, BN are increasingly applied in various areas of civil and environmental engineering for reliability/risk assessment and decision making. Examples of applications include: Reliability analysis of infrastructure systems, natural hazards risk assessment, probabilistic modeling in hydrology, optimization of construction operations, and risk based planning of inspection and maintenance. The seminar will provide an introduction to the use of Bayesian networks. Topics to be covered include:
  -  An introduction to reasoning under uncertainty and Bayes’ theorem
  -  Modeling dependencies and identifying the network structure
  -  Decision optimization
  -  Computational aspects and limitations of the model
  -  Overview on available software for BN analysis
  -  Example applications
The content of the lectures may be adjusted according to specific interests.

Date: October 11, 2006.
Title: A stochastic model for earthquake ground motion with separable temporal and spectral nonstationarity
Speaker: Sanaz Rezaeian
Abstract: A discrete and fully nonstationary model for strong earthquake ground motions will be considered. In this model the discrete formulation and the ability of separating the temporal and spectral nonstationary characteristics allows flexibility and ease in modeling. The resulting nonstationary stochastic process can be fitted to a target ground motion in terms of a set of statistical data. The main purpose of this seminar is to focus on a discussion regarding the development of an optimization scheme that determines the parameters of the stochastic process using a set of target statistical characteristics which are obtained from previously recorded earthquakes in a region of interest.

Date: September 27, 2006.
Title: Hierarchical modelling and Bayesian inference of seismic fragility
Speaker: Daniel Straub
Abstract: Two different models for representing earthquake fragility from empirical data are presented and compared. One model is based on a limit state (engineering) approach, the second on a regression model (statistical approach). Both models are hierarchical, i.e. they differentiate between component-specific and site/system-specific factors, as opposed to traditional fragility models which neglect the system effects. Based on data of observed failures of equipement in electrical substations, it will be demonstrated how the appropriate model can be chosen. The Bayesian analysis of the data will be outlined and some of the difficulties involved will be discussed. The results obtained with different models will be compared. Finally, it will be demonstrated why the consideration of system effects (i.e. the use of hierarchical models) is crucial for system reliability assessments.

Date: August 16, 2006.
Title: Tail-equivalent linearization for nonlinear random vibration
Speaker: Kazuya Fujimura
Abstract: I will describe the main results of my doctoral dissertation.

Date: August 2, 2006.
Title: Effect of tuned mass damper on displacement demand of base-isolated structures
Speaker: Armen Der Kiureghian
Abstract: The effectiveness of a recently proposed scheme to reduce the displacement demand of a base-isolated structure by installing a tuned-mass damper underneath its isolation system is examined. Optimal parameters of the TMD for response to white noise are determined. It is found that, under such an excitation, a reduction of the order of 15% to 25% in the displacement demand can be achieved by adding the optimal TMD. Next, responses of an example base-isolated structure with and without an optimally designed TMD to selected suites of far- and near-field recorded accelerograms are compared. The study shows that for far-field ground motions the effectiveness of the TMD is more or less similar to that predicted by the white noise model, whereas for near-field ground motions the effectiveness of the TMD is far less, i.e., of the order of 10% or less. Reasons for this result are described.

Date: July 26, 2006.
Title: Uncertainty in failure rates of infrastructure systems
Speaker: Daniel Straub
Abstract: Reliability analysis of infrastructure systems (oil/gas, elctricity, transportation, water), often relies on failure rates which have been observed in the past. Unfortunately, the avilable data for estimating those failure rates is often sparse and the conditions under which these failures are observed are only partly known. For these reasons, the resulting failure rates are subject to large uncertainties. Based on the example of water distribution systems subject to earthquakes, a Bayesian model for representing the uncertainty on the failure rates will be presented, together with the tools for their evaluation. This is followed by a demonstration of the effect of the uncertainty on the overall system reliability and a discussion of how and when the presented models should be applied in practical risk management.

Date: July 6, 2006.
Title: A Nonstationary Stochastic Model for Strong Earthquake Ground Motion
Speaker: Sanaz Rezaeian
Abstract: In performance based earthquake engineering (PBEE), the use of actual accelerogram recordings have created questionable tasks about selecting and scaling recorded ground motions from different locations. Therefore, generating artificial ground acceleration time histories through a model that uniquely represents the characteristics of the subject site is of interest. This presentation focuses on developing a model that enables us to generate a target ground motion characterized by a finite number of parameters. The key to this method is the discrete format of the formulation that is achieved by filtering a discretized white-noise process. The advantage of this model over others is its ability to separately represent the temporal and spectral nonstationarity characters of the motion. This model can also be used for nonlinear random vibration analysis by the tail-equivalent linearization method.

Date: May 24, 2006.
Title: Some topics on life cycle cost evaluation
Speaker: Gang Li
Abstract: The evaluation of structural life-cycle cost is a key problem in performance based seismic design, which generally contains three major problems: modeling the evaluation formulation, calculating the occurrence probability of failure modes of interest, and determining the loss value of the failure mode when it occurs. This presentation focuses on the first two problems with the following topics:
-- expected loss evaluation in consideration of correlation between failure modes
-- expected loss evaluation based on fuzzy theory
-- approximate efficient reliability analysis of some specific types of structures

SPECIAL EVENT: Reliability Symposium: Presentations by students in CE229. See program
Date: May 19, 2006
Time: 9:45AM to 3:40PM
Place: 544 Davis Hall

Date: May 10, 2006.
Title: An overview on reliability and risk based inspection planning (RBI)
Speaker: Daniel Straub
Abstract: In RBI, Bayesian decision analysis is applied to optimize the inspection efforts on deteriorating structures, by explicitly addressing the uncertainties both in the deterioration processes and the inspection performance. The presentation will give a concise overview on RBI, including
    -   The general decision optimization problem
    -   The probabilistic modeling of the deterioration and the inspections
    -   Computational issues (structural reliability analysis vs simulation methods)
    -   Risk acceptance
    -   System aspects
An overview on practical applications of the methodology to the planning of inspections on offshore structures subject to fatigue concludes the talk.

Date: April 21, 2005.
Title: Structural-reliability-based analysis of large and/or complex systems
Speaker: Charles Menun
Abstract: The probability that a large and/or complex system of interconnected facilities (e.g., power and water distribution networks and transportation systems) fails to perform in a satisfactory manner during and after an extreme event such as an earthquake or hurricane is naturally of interest. Structural-reliability-based procedures are well suited for such analyses because, in addition to providing an estimate of the probability that a system will fail, they also provide sensitivity information that can be used to identify those components within the system that are most critical to its performance. However, there are a number of algorithmic problems that must be resolved before available system-reliability-based analysis procedures can be efficiently applied to large and/or complex systems of components. For example, if the inclusion-exclusion rule is used to compute the probability of failure of a series system, then the required number of probability calculations increases geometrically with the number of components present in the system, thereby limiting the applicability of such an approach. This paper describes the required modifications to conventional structural-reliability-based calculations for the performance assessment of large and/or complex systems of components. Numerical examples are provided to illustrate the application of the proposed procedure.

Date: April 14, 2005.
Title: PDF of maximum response by the TELM
Speaker: Kazuya Fujimura
Abstract: In the PBEE application, the PDF of maximum response (displacement, velocity, acceleration) is required for a given level of intensity measure. The simulation approach using actual earthquake records selected by the results of PSHA can be used for this purpose. However, this approach includes the subjectivity due to the selection of earthquake records, which might result in a large variability in the final output of the PBEE application. To avoid this subjectivity, a random vibration approach is proposed as an alternative. Under stationary excitation, the PDF can be obtained efficiently by using TELM. An example application to a 6dof shear-building model will be presented.

Date: April 7, 2005.
Title: Reliability Methods in Medical Decision Making
Speaker: Lilit Yeghiazarian, Department of Bioengineering, UCLA
Abstract: Most medical decisions are normally made without the benefit of complete information, the treatment entails incomplete efficacy along with costs and risks, and consequently the assurance of successful cure is never perfect. The uncertainty is associated not only with the validity of the diagnostic tools, but also with the inherent randomness and variability in the neuro-physiological organization of individual patients, and the probabilistic nature of physical and biological parameters associated with tumor development and invasion. We propose to extend reliability methods, in particular FORM/SORM, to cancer analysis and risk assessment to enhance medical decision making. Applications in multiscale cancer models are also considered.

Date: March 17, 2005.
Title: SORM and Simulation in the Tail Equivalent Linearization Method (TELM)
Speaker: Kazuya Fujimura
Abstract: The accuracy of the TELM depends on the accuracy of the FORM for the instantaneous failure probability. When the limit-state surface is far from being flat, FORM may not provide a good approximation, and consequently TELM may not provide a good approximation to the first passage probability. One possible solution is to apply SORM or Simulation to achieve a better approximation to the instantaneous failure probability. An example problem will be shown to discuss the property of the solution.

Date: March 3, 2005.
Title: Identification of Critical Components and Cut sets Using Linear Programming Bounds on System Reliability
Speaker: Junho Song

Date: February 24, 2005.
Title: Tail-equivalent linearization for nonlinear random vibration
Speaker: Kazuya Fujimura

Date: February 17, 2005.
Title: The inclusion-exclusion formula and its use in estimating system reliability
Speaker: Junho Song

Date: February 10, 2005.
Title: Risk analysis using Bayesian network
Speaker: Armen Der Kiureghian
Abstract: A brief introduction to the use of Bayesian networks (BN) for risk analysis will be presented. The Hugin program developed in Denmark for BN analysis will be demonstrated.