Michele Barbato | University of California, Davis (original) (raw)

Books by Michele Barbato

Computational Structural Dynamics and Earthquake Engineering: Vol.2

Earthquake engineering has a crucial need for efficient and accurate analytical tools to propagat... more Earthquake engineering has a crucial need for efficient and accurate analytical tools to propagate uncertainties from the seismic input and finite element (FE) model parameters to a probabilistic estimate of the seismic performance through advanced large-scale nonlinear simulations based on the same FE models as those used in deterministic analysis. Sensitivities of the FE response with respect to both model and loading parameters represent an essential ingredient in studying this complex propagation of uncertainties. This study presents recent developments in FE response sensitivity analysis based on the Direct Differentiation Method (DDM) for displacement-based, force-based, and three-field mixed finite elements. First-Order Second-Moment (FOSM) approximations of the first- and second-order statistics of the response of structural systems with random/uncertain parameters and subjected to deterministic quasi-static or dynamic loads are obtained using DDM-based FE response sensitivities and compared to Monte Carlo simulation results. First-Order Reliability Method (FORM) is applied to evaluate the prob-ability of a structural response quantity exceeding a specified threshold level in conjunction with the DDM-based FE response sensitivities in the search for the “design point(s)” (DPs). Both time-invariant and time-variant problems are considered. The geometry of limit-state surfaces near the DP(s) is explored in subspaces defined by planes of major principal curvatures. This geometry explains the lack of accuracy of FORM-based solutions in some cases and suggests the development of new improved solution strategies, e.g., the Design Point-Response Surface-Simulation (DP-RS-Sim) method. The examples presented in this study include both structural systems and soil-foundation-structure interaction systems and are based on two types of analysis which are used extensively in earthquake engineering, namely pushover analysis and time history analysis.

Papers by Michele Barbato

Earthquake Engineering & Structural Dynamics, 2016

Earthquake-induced pounding of adjacent structures can cause severe structural damage, and advanc... more Earthquake-induced pounding of adjacent structures can cause severe structural damage, and advanced probabilistic approaches are needed to obtain a reliable estimate of the risk of impact. This study aims to develop an efficient and accurate probabilistic seismic demand model (PSDM) for pounding risk assessment between adjacent buildings, which is suitable for use within modern performance-based engineering frameworks. In developing a PSDM, different choices can be made regarding the intensity measures (IMs) to be used, the record selection, the analysis technique applied for estimating the system response at increasing IM levels, and the model to be employed for describing the response statistics given the IM. In the present paper, some of these choices are analyzed and evaluated first by performing an extensive parametric study for the adjacent buildings modeled as linear single-degree-of-freedom systems, and successively by considering more complex nonlinear multi-degree-of-freedom building models. An efficient and accurate PSDM is defined using advanced intensity measures and a bilinear regression model for the response samples obtained by cloud analysis. The results of the study demonstrate that the proposed PSDM allows accurate estimates of the risk of pounding to be obtained while limiting the number of simulations required.

Computer Methods in Applied Mechanics and Engineering, 2005

The behavior of steel-concrete composite beams is strongly influenced by the type of shear connec... more The behavior of steel-concrete composite beams is strongly influenced by the type of shear connection between the steel beam and the concrete slab. For accurate analytical predictions, the structural model must account for the interlayer slip between these two components. In numerous engineering applications ͑e.g., in the fields of structural optimization, structural reliability analysis, and finite element model updating͒, accurate response sensitivity calculations are needed as much as the corresponding response simulation results. This paper focuses on a procedure for response sensitivity analysis of steel-concrete composite structures using displacement-based locking-free frame elements including deformable shear connection with fiber discretization of the cross section. Realistic cyclic uniaxial constitutive laws are adopted for the steel and concrete materials as well as for the shear connection. The finite element response sensitivity analysis is performed according to the direct differentiation method. The concrete and shear connection material models as well as the static condensation procedure at the element level are extended for response sensitivity computations. Two steel-concrete composite structures for which experimental test results are available in the literature are used as realistic testbeds for response and response sensitivity analysis. These benchmark structures consist of a nonsymmetric, two-span continuous beam subjected to monotonic loading and a frame subassemblage under cyclic loading. The new analytical derivations for response sensitivity calculations and their computer implementation are validated through forward finite difference analysis based on the two benchmark examples considered. Selected sensitivity analysis results are shown for validation purposes and for quantifying the effect and relative importance of the various material parameters in regards to the nonlinear monotonic and cyclic response of the testbed structures.

Probabilistic Push-Over Analysis of Structural and Soil-Structure Systems

Journal of Structural Engineering, 2010

In this paper, the mean-centered first-order second-moment (FOSM) method is employed to perform p... more In this paper, the mean-centered first-order second-moment (FOSM) method is employed to perform probabilistic push-over analysis (POA) of structural and/or soil-structure systems. Approximations of first and second statistical moments (FSSMs) of engineering demand parameters (EDPs) of structural and/or geotechnical systems with random material parameters are computed based on finite-element (FE) response and response sensitivity analysis (RSA) results. The FE RSA is performed accurately and efficiently by using the ...

Engineer, 2008

This paper presents recent advances in response sensitivity, probabilistic response and reliabili... more This paper presents recent advances in response sensitivity, probabilistic response and reliability analyses of structural and geotechnical systems. These developments are integrated into general-purpose nonlinear finite element (FE) software frameworks and provide the structural engineers with analytical and computational tools to propagate uncertainties through advanced large-scale nonlinear simulations and obtain probabilistic estimates of the predicted system response performance. The Direct Differentiation Method (DDM) for accurate and efficient computation of FE response sensitivities is extended and applied to large-scale nonlinear Soil-Foundation-Structure-Interaction (SFSI) systems. Extensions include numerical algorithms for response sensitivity analysis of FE models with multi-point constraints, force-based and three-field mixed elements, as well as various nonlinear material constitutive models, including a pressure independent multi-yield-surface J 2 plasticity material model used to simulate the clay soil nonlinear behavior. Response sensitivity analysis results are shown for structural and SFSI systems. Examples of probabilistic response as well as time-invariant and time-variant reliability analyses are provided. Importance sampling and orthogonal plane sampling techniques are adopted and implemented into the considered FE software frameworks for accurate computation of failure probabilities. A new visualization technique, the Multidimensional Visualization in the Principal Planes (MVPP), is developed to visualize limit state surfaces in a neighborhood of the design points, giving insight into inaccuracy of the First-Order Reliability Method (FORM) for highly nonlinear systems. Based on the MVPP technique results, a novel hybrid method, the Design Point -Response Surface -Simulation (DP-RS-Sim) method is developed for both time-invariant and time-variant reliability analysis. Application examples are provided to show that the DP-RS-Sim method can provide failure probability estimates more accurate than FORM at a small increment of the computational cost.

First European Conference on Earthquake Engineering and Seismology, 2006

This paper presents recent developments in response sensitivity, probabilistic response and relia... more This paper presents recent developments in response sensitivity, probabilistic response and reliability analyses of structural and geotechnical systems. These developments are integrated within general-purpose software frameworks for non-linear finite element response analysis and provide the structural engineers with analytical tools to propagate uncertainties through advanced large-scale non-linear simulations to obtain probabilistic estimates of the predicted system response performance. Necessary extensions of the Direct Differentiation Method (DDM) for accurate and efficient computation of finite element response sensitivities are presented. Examples of such response sensitivity computations are shown for structural and Soil-Foundation-Structure-Interaction (SFSI) systems. Uncertainty propagation is illustrated through examples of probabilistic response (First-Order Second-Moment approximation), time-invariant (First-and Second-Order Reliability Method) and time-variant (mean outcrossing rate computation) reliability analyses. These examples are based on two types of analysis, namely pushover analysis and time history analysis, which are used extensively in earthquake engineering.

Nonlinear Dynamic Analysis of Steel-Concrete Composite Frame Structures With Full and Partial Shear Connection Under Earthquake Excitation

Various finite element (FE) models can be used for the analysis of steel-concrete composite (SCC)... more Various finite element (FE) models can be used for the analysis of steel-concrete composite (SCC) structures. Among available FE models, frame elements permit obtaining significant information at reasonable computational cost compared to more sophisticated two-dimensional (plate/shell) and three-dimensional (solid) elements. As an extension of conventional monolithic beam models, beams with deformable shear connection were specifically introduced and adopted for the analysis of SCC beams. Flexible shear ...

Probabilistic Engineering Mechanics, 2008

The spectral characteristics are important quantities in describing random processes. Proper defi... more The spectral characteristics are important quantities in describing random processes. Proper definitions of these quantities are available for realvalued stationary and non-stationary processes. In this paper, the well-established definitions of spectral characteristics for real-valued stationary and non-stationary processes are extended to general complex-valued non-stationary random processes. This extension allows to derive the exact solution in closed-form for the classical problem of computing the time-variant central frequency and bandwidth parameter of the response processes of single-degree-of-freedom (SDOF) and both classically and non-classically damped multi-degree-of-freedom (MDOF) linear elastic systems subjected to white noise excitation from at rest initial conditions. These new exact closed-form solutions are also used to gain deeper insight into the time-variant and stationary behavior of the central frequency and bandwidth parameter of these linear response processes.

Journal of Engineering Mechanics, 2009

In this paper, the direct differentiation method ͑DDM͒ for finite-element ͑FE͒ response sensitivi... more In this paper, the direct differentiation method ͑DDM͒ for finite-element ͑FE͒ response sensitivity analysis is extended to linear and nonlinear FE models with multi-point constraints ͑MPCs͒. The analytical developments are provided for three different constraint handling methods, namely: ͑1͒ the transformation equation method; ͑2͒ the Lagrange multiplier method; and ͑3͒ the penalty function method. Two nonlinear benchmark applications are presented: ͑1͒ a two-dimensional soil-foundation-structure interaction system and ͑2͒ a three-dimensional, one-bay by one-bay, three-story reinforced concrete building with floor slabs modeled as rigid diaphragms, both subjected to seismic excitation. Time histories of response parameters and their sensitivities to material constitutive parameters are computed and discussed, with emphasis on the relative importance of these parameters in affecting the structural response. The DDMbased response sensitivity results are compared with corresponding forward finite difference analysis results, thus validating the formulation presented and its computer implementation. The developments presented in this paper close an important gap between FE responseonly analysis and FE response sensitivity analysis through the DDM, extending the latter to applications requiring response sensitivities of FE models with MPCs. These applications include structural optimization, structural reliability analysis, and finite-element model updating.

International Journal of Reliability and Safety, 2006

Conte, Finite element structural response sensitivity and reliability analyses using smooth versu... more Conte, Finite element structural response sensitivity and reliability analyses using smooth versus non-smooth material constitutive models

Journal of Structural Engineering, 2008

Structural Reliability Applications of Nonstationary Spectral Characteristics

Journal of Engineering Mechanics, 2011

This paper presents new closed-form analytical approximations to the first-passage problem in str... more This paper presents new closed-form analytical approximations to the first-passage problem in structural reliability by using the exact closed-form solutions for the spectral characteristics of nonstationary random processes. The first-passage problem applied to a structural system possibly with random parameters and subjected to stochastic loading consists of computing the probability of a response quantity exceeding a deterministic threshold in a given exposure time. This paper also investigates, on the basis of benchmark problems, the ...

Journal of Materials in Civil Engineering, 2014

Considerable interest has been directed in recent years toward the use of self-healing materials ... more Considerable interest has been directed in recent years toward the use of self-healing materials in concrete. The concept of microcapsule healing is based on a healing agent being encapsulated and embedded in the concrete. The objective of this study was to evaluate the effects of preparation parameters, namely, temperature, agitation rate, and pH on the shell thickness and size (diameter) of the microcapsules; as well as to evaluate the self-healing mechanism in concrete through experimental testing performed in laboratory. Two healing agents were evaluated in this study, i.e., dicyclopentadiene (DCPD) and sodium silicate. Based on the results of the experimental program, it was determined that, as the pH was increased from 3.0 to 3.7, the shell thickness increased for sodium silicate, while the shell thickness reached a minimum at a pH value of 3.4 for DCPD. Sodium silicate shell thickness was almost twice the shell thickness for DCPD. The most uniform and coherent microcapsules were produced at a temperature of 55°C for both sodium silicate and DCPD. For the DCPD microcapsules and up to 49°C, the J. Mater. Civ. Eng. Downloaded from ascelibrary.org by LOUISIANA STATE UNIV on 07/15/13. Copyright ASCE. For personal use only; all rights reserved. content of 5.0%. At other pH values, the effect of the sodium silicate microcapsules on the concrete performance was negligible. For DCPD microcapsules, the healing agent was effective in increasing the modulus of elasticity of concrete after cracking by as much as 30% for the microcapsules prepared at a pH value of 3.1 and at a content of 0.25%.

A probabilistic performance‐based approach for mitigating the seismic pounding risk between adjacent buildings

ABSTRACT Existing design procedures for determining the separation distance between adjacent buil... more ABSTRACT Existing design procedures for determining the separation distance between adjacent buildings subjected to seismic pounding risk are based on approximations of the buildings' peak relative displacement. These procedures are characterized by unknown safety levels and thus are not suitable for use within a performance-based earthquake engineering framework.

Influence of Model Parameter Uncertainty on Seismic Transverse Response and Vulnerability of Steel–Concrete Composite Bridges with Dual Load Path

This paper uses a fully probabilistic approach to investigate the seismic response of multispan c... more This paper uses a fully probabilistic approach to investigate the seismic response of multispan continuous bridges with dissipative piers and a steel–concrete composite (SCC) deck, the motion of which is transversally restrained at the abutments. This bridge typology is characterized by complex dual load path behavior in the transverse direction, with multiple failure modes involving both the deck and the piers.

Probabilistic push-over analysis of structural and soil-structure systems

Effects of Modeling Parameter Uncertainty on the Structural Response of Offshore Wind Turbines

ABSTRACT The design of complex structures like Offshore Wind Turbines (OWTs) is commonly based on... more ABSTRACT The design of complex structures like Offshore Wind Turbines (OWTs) is commonly based on the results of deterministic structural analyses, carried out on finite element models of the structural system. However, the assessment of the structural response is affected by significant uncertainties, due to the random variability of both the environmental actions and the geometric and mechanical properties of the structure.

Probabilistic Performance Based Risk Assessment Considering the Interaction of Wind and Windborne Debris Hazards

ABSTRACT This paper introduces a probabilistic Performance Based Hurricane Engineering (PBHE) fra... more ABSTRACT This paper introduces a probabilistic Performance Based Hurricane Engineering (PBHE) framework for risk assessment based on the total probability theorem. This methodology disaggregates the risk assessment analysis into independent elementary components, namely hazard analysis, structural characterization, interaction analysis, structural analysis, damage analysis, and loss analysis. The proposed PBHE framework accounts for the multi-hazard nature of hurricanes.

Stochastic Analysis of the Risk of Seismic Pounding Between Adjacent Buildings

Seismic pounding can induce severe damage and losses in buildings. The corresponding risk is part... more Seismic pounding can induce severe damage and losses in buildings. The corresponding risk is particularly relevant in densely inhabited metropolitan areas, due to the inadequate clearance between buildings. In order to mitigate the seismic pounding risk, building codes provide simplified procedures for determining the minimum separation distance between adjacent buildings. The level of safety corresponding to the use of these procedures is not known a priori and needs to be investigated.

Seismic Response and Vulnerability of Steel‐Concrete Composite Bridges Accounting for Model Parameter Uncertainties

ABSTRACT The performance of multi-span steel-concrete composite (SCC) bridges in recent seismic e... more ABSTRACT The performance of multi-span steel-concrete composite (SCC) bridges in recent seismic events has shown that these structures are very sensitive to earthquake loading. Extensive damage can occur not only in the substructures, which are expected to yield, but also in the components of the superstructure involved in transferring the seismic loads.