Performance-based Engineering Research Articles

DIN 18009-2 – a New German Standard on Evacuation Simulation

After more than eight years of intensive work, the second part of the German DIN 18009 standard on "Simulation of evacuation and personal safety" was published in August 2022. The DIN 18009 series offers a guideline for fire protection engineering for Germany. The first part "Principles and application rules" was published in 2016, with further parts describing standards for smoke simulation and safety concepts to follow. This marks a milestone in the application of simulation models in the safety context for Germany. This article discusses the advantages and disadvantages of prescriptive guidelines and performance-based engineering methods in the context of building evacuation. Furthermore, aspects of the application of the DIN 18009-2 are highlighted, and what challenges are still to be tackled and how. This includes in particular the choice and definition of scenarios and performance criteria.

GIS-Based Regional Seismic Risk Assessment for Dubai, UAE, Using NHERI SimCenter R2D Application

GIS-Based Regional Seismic Risk Assessment for Dubai, UAE, Using NHERI SimCenter R2D Application

Seismic Fragility Estimation Based on Machine Learning and Particle Swarm Optimization

In seismic performance assessment, the development of building fragility curves is critical for performance-based engineering. Traditional methods for time history analysis, reliant on detailed ground motion (GM) inputs, often suffer from inefficiency and a lack of automation. This study proposes an accurate fragility assessment methodology, which is assisted by machine learning (ML) and particle swarm optimization (PSO), adept at handling scenarios with both scarce and sufficient fragility data. Under scenarios of scarce data, the integrated algorithms of PSO and ML are utilized, focusing on selecting GMs that may induce maximum inter-story drifts. When the dataset is sufficient, an ML fusion model is utilized to predict engineering demand parameters (EDPs), facilitating the generation of more accurate fragility curves. The effectiveness of this method is demonstrated through a case study on a high-rise reinforced concrete (RC) building, revealing a marked improvement in the precision of GM selection and the estimated range of fragility curves over traditional approaches. The proposed methodology aids in advancing structural optimization and the development of early-warning systems for seismic events, thus holding the potential to enhance current seismic risk mitigation strategies.

Relaxation-based importance sampling for structural reliability analysis

This study presents an importance sampling formulation based on adaptively relaxing parameters from the indicator function and/or the probability density function. The formulation embodies the prevalent mathematical concept of relaxing a complex problem into a sequence of progressively easier sub-problems. Due to the flexibility in constructing relaxation parameters, relaxation-based importance sampling provides a unified framework for various existing variance reduction techniques, such as subset simulation, sequential importance sampling, and annealed importance sampling. More crucially, the framework lays the foundation for creating new importance sampling strategies, tailoring to specific applications. To demonstrate this potential, two importance sampling strategies are proposed. The first strategy couples annealed importance sampling with subset simulation, focusing on low-dimensional problems. The second strategy aims to solve high-dimensional problems by leveraging spherical sampling and scaling techniques. Both methods are desirable for fragility analysis in performance-based engineering, as they can produce the entire fragility surface in a single run of the sampling algorithm. Three numerical examples, including a 1000-dimensional stochastic dynamic problem, are studied to demonstrate the proposed methods.

Generalized Stratified Sampling for Efficient Reliability Assessment of Structures against Natural Hazards

Performance-based engineering for natural hazards facilitates the design and appraisal of structures with rigorous evaluation of their uncertain structural behavior under potentially extreme stochastic loads expressed in terms of failure probabilities against stated criteria. As a result, efficient stochastic simulation schemes are central to computational frameworks that aim to estimate failure probabilities associated with multiple limit states using limited sample sets. In this work, a generalized stratified sampling scheme is proposed in which two phases of sampling are involved: the first is devoted to the generation of strata-wise samples and the estimation of strata probabilities, whereas the second phase aims at the estimation of strata-wise failure probabilities. Phase-I sampling enables the selection of a generalized stratification variable (i.e., not necessarily belonging to the input set of random variables) for which the probability distribution is not known a priori. To improve the efficiency, Markov Chain Monte Carlo Phase-I sampling is proposed when Monte Carlo simulation is deemed infeasible, and optimal Phase-II sampling is implemented based on user-specified target coefficients of variation for the limit states of interest. The expressions for these coefficients are derived with due regard to the sample correlations induced by the Markov chains and the uncertainty in the estimated strata probabilities. The proposed stochastic simulation scheme reaps the benefits of near-optimal stratified sampling for a broader choice of stratification variables in high-dimensional reliability problems with a mechanism to approximately control the accuracy of the estimators of multiple failure probabilities. The practicality and efficiency of the scheme are demonstrated using two examples involving the estimation of failure probabilities associated with highly nonlinear responses induced by wind and seismic excitations.

Probabilistic Incremental Dynamic Analysis for Seismic Isolation Systems through Integration with the NHERI-SimCenter Performance-Based Engineering Application

In the wake of the 1994 Northridge and 1995 Kobe earthquakes, structural designers adopted performance-based engineering concepts instead of traditional deterministic design approaches. The primary change was to evaluate the design according to stakeholders’ interests instead of the engineering parameters. This evaluation process required a probabilistic estimation for the included variables at all design stages. The NHERI-SimCenter application framework provides generic solutions implemented in different hazard simulation problems. Seismic isolation is an efficient, proven technique for improving seismic performance by limiting drift ratios and reducing damage. During the design stage, seismic isolation-system parameters must be carefully calibrated to control different aspects of the response, and it is necessary to run multiple simulations and count for parameter uncertainties. This research introduced components for seismic isolation and incremental dynamic analysis procedures integrated with framework modules, such as uncertainty quantifications and damage and loss estimation. Furthermore, an illustrative case study was included to reflect the impacts of this development.

ASCE/SEI 41 assessment of reinforced concrete buildings: Benchmarking nonlinear dynamic procedures with empirical damage observations

ASCE/SEI 41 is the consensus US standard for the seismic evaluation and retrofit of existing buildings. Although the performance-based engineering standard is based on decades of research and has been significantly vetted by ASCE and other committees, it is unclear how well the evaluations capture the seismic response of real building systems. This article examines six, primarily nonductile, reinforced concrete buildings, including four damaged in earthquakes and two experimental structures tested and damaged on shake tables, to compare the measured response and observed damage to simulated outcomes produced following ASCE/SEI 41 nonlinear dynamic procedure. The results show that the simulations are generally able to capture the story mechanism and peak transient story drift demands at the critical story (predicted values are typically within ±20% of the measured values). However, drifts at non-critical stories and floor accelerations at all stories show greater error relative to the measured responses. At the component level, the simulations, in most cases, correctly identify the location(s) of the critical component(s) and the failure mode (e.g. flexure vs shear). However, the extent of the damage is overestimated in some cases. These results form the basis for recommendations for column, beam, and wall modeling procedures that can be used to improve ASCE/SEI 41.

Factors Affecting the Fire Safety Design of Photovoltaic Installations Under Performance-Based Regulations in Norway

The impact of Photovoltaic (PV) installations on the fire safety of buildings must be considered in all building projects where such energy systems are established. The holistic fire safety of the building largely depends on how the fire safety of the PV installation is considered by the different actors during the design and construction process. Research has therefore been undertaken to study how performance-based regulations in combination with the lack of national guidelines affect the overall fire safety considerations for PV installations in Norway. Four factors were found to govern to which extent PV installations are emphasised in the fire safety design phase: (1) whether the building was first of its kind as a pioneering building, (2) whether the building was built before or after the publication of the 2018 revision of the norm NEK 400, (3) The level of knowledge and experience of the fire safety consultant, which in turn affects the use of performance-based engineering tools and the level of detailing in the design and construction phases, and (4) The degree of integration in the building. The main goal of the study is to give an insight and a contribution to the development of in-depth knowledge on how fire safety design for PV installations on buildings is handled in Norway, which may also be relevant to other countries with similar performance-based regulations.

An efficient stratified sampling scheme for the simultaneous estimation of small failure probabilities in wind engineering applications

With the advent of performance-based engineering frameworks for extreme winds, greater efficiency in the estimation of failure probabilities associated with multiple limit states at ultimate load levels, including collapse, is required. To meet this demand, an optimal stratified sampling-based simulation scheme is proposed that shares several meritorious characteristics of standard Monte Carlo simulation (MCS), including the capability to deal with high-dimensional uncertain spaces and multiple limit state functions. The optimality of the scheme is governed by the allocation of MCS samples among the strata as well as the strata division itself. A constrained optimization problem is formulated to address efficient sample allocation which is an extension of the Neyman allocation. Details for the practical implementation of the scheme within wind engineering reliability assessment applications are discussed. It is observed that the proposed methodology can reduce the variance by several orders of magnitude compared to MCS, which is illustrated on a wind-excited steel structure for the limit states of member/system first yield and collapse. The applicability of Latin hypercube sampling within stratified sampling-based simulation and the resulting efficiency gains are also critically studied. The results show promise in the wider applicability of the proposed scheme in performance-based wind engineering.

Performance-Based Structural Fire Engineering of Steel Building Structures: Traveling Fires

Many studies and observations of large building fires show that in large compartments, fires do not burn uniformly. Rather, fires will burn locally and move across a floor plate as fuel is consumed. Currently fire engineering practice assumes uniformly burning fires within a compartment and the fire design methodologies are based upon small compartment fire scenarios. Traveling fire modeling that accounts for fire dynamics is essential for performance-based fire engineering. This paper reviews two traveling fire models presented in literature and implements both models on a steel-frame building. An advanced analysis of the building is performed and the fire performance of the building in these travel fire scenarios are compared to the fire performance of the building when subjected to conventional fire exposure scenarios (full story fires or compartment fires). The authors then illustrate the use of structural fire engineering methodologies to improve the fire resistance of the building.

Multi-objective reliability-based seismic performance design optimization of SMRFs considering various sources of uncertainty

The purpose of this paper is to present an approach for multi-objective reliability-based seismic design optimization of Steel Moment Resisting Frames (SMRFs), considering weight and drift uniformity ratio (DUR) as objective functions plus deterministic and probabilistic criteria as constraints, while taking into account the effects of aleatory and epistemic uncertainties. To this end, structural reliability and performance-based seismic design criteria were used to preserve desired levels of structural safety during its life-time. The aleatory uncertainties were applied using estimated incremental dynamic analysis fractile curves, and epistemic uncertainties were applied by realization of stochastic variables. The mean annual frequency was used as a limit-state parameter to check reliability criteria. The novel technique of “shifting displacement-control node” was used to fix drawbacks of previous studies in SMRFs optimization, for non-convergence of solving finite element (FE) equations of different failure mechanisms, especially in the inelastic region and high drifts of pushover curve, as well as reaching the gravitational instability point for more reliable assessment of non-linear structural behavior. The proposed method, applied to 3 cases, ultimately led to the design of cost-effective structures with a desirable seismic performance. In some generated structures, the snap-back phenomenon occurred for inter-story as well as the overall drift of structures. Identification of this phenomenon in SMRFs has received less attention due to the difficulty of solving related FE problems. The effects of considering uncertainties and DUR in high drifts were studied, whereby unexpected results were achieved, such as occurrence and effects of the snap-back phenomenon, relation between DUR and reliability constraints, differences of structures satisfying deterministic and reliability criteria, the importance of selection of control node in pushover analysis, etc. The tools and algorithms developed through this research could help implement performance-based engineering in the design process of SMRFs, in a cost-effective, consistent, and repetitive manner. These algorithms help designers provide project stakeholders with decision-making tools suitable for risk-based structural engineering design for seismic hazard and methods to compare as well as evaluate alternative designs. These algorithms and methods also allow designers to easily compare and contrast structural designs concerning the expected performance.

A performance-based approach to quantify atmospheric river flood risk

Abstract. Atmospheric rivers (ARs) are a class of meteorologic phenomena that cause significant precipitation and flooding on the US West Coast. This work presents a new Performance-based Atmospheric River Risk Analysis (PARRA) framework that adapts existing concepts from probabilistic risk analysis and performance-based engineering for application in the context of AR-driven fluvial flooding. The PARRA framework is a chain of physically based models that link the atmospheric forcings, hydrologic impacts, and economic consequences of AR-driven fluvial flood risk together at consistent “pinch points”. Organizing around these pinch points makes the framework modular, meaning that models between pinch points can be updated without affecting the rest of the model chain, and it produces a probabilistic result that quantifies the uncertainty in the underlying system states. The PARRA framework can produce results beyond analyses of individual scenario events and can look toward prospective assessment of events or system changes that have not been seen in the historic record. The utility of the PARRA framework is demonstrated through a series of analyses in Sonoma County, CA, USA. Individual component models are fitted and validated against a historic catalog of AR events occurring from 1987 to 2019. Comparing simulated results from these component model implementations against observed historic ARs highlights what we can learn about the drivers of extremeness in different flood events by taking a probabilistic perspective. The component models are then run in sequence to generate a first-of-its-kind AR flood loss exceedance curve for Sonoma County. The prospective capabilities of the PARRA framework are presented through the evaluation of a hypothetical mitigation action. Elevating 200 homes, selected based on their proximity to the Russian River, was sufficient to reduce the average annual loss by half. Although expected benefits were minimal for the smallest events in the stochastic record, the larger, more damaging ARs were expected to see loss reductions of approximately USD 50–75 million per event. These results indicate the potential of the PARRA framework to examine other changes to flood hazard, exposure, and vulnerability at the community level.

The CAED Framework for the Development of Performance-Based Design at the Wildland–Urban Interface

The hazard posed by wildland–urban-interface (WUI) fires is recognized by the international fire research community and features as one of nine research need priority threads in the Society of Fire Protection Engineers (SFPE) Research Roadmap. We posit that the first step in the journey to enhancing fire safety engineering at the WUI is to develop a common understanding between developers, engineers, planners, and regulators of the development scope, wildfire problem, technical design solutions, and verification methods to be used. In order to define a fire safety engineering consultation process appropriate for the wildfire context, this paper aims to translate well-established and evidence-based performance-based design (PBD) consultation frameworks and approaches from traditional fire safety engineering to the wildfire context. First, we review international English-language fire safety engineering frameworks that have been developed for the urban context. Next, we distil the results into a streamlined framework, which we call the “CAED Framework”. Finally, we apply and discuss the contextualization of the CAED Framework to the WUI context through a comparative case study of urban and WUI development. In doing so we seek to provide a structure for the development of standardized PBD within the WUI context across jurisdictions internationally, as well as to embed best practices into the emerging field of performance-based wildfire engineering.

On the ergodicity assumption in Performance-Based engineering

In the Performance-Based Engineering (PBE) framework, uncertainties in system parameters, or modelling uncertainties, have been shown to have significant effects on capacity fragilities and annual collapse rates of buildings. Yet, since modelling uncertainties are non-ergodic variables, their consideration in failure rate calculations offends the Poisson assumption of independent crossings. This problem has been addressed in the literature, and errors found negligible for small annual collapse failure rates. However, the errors could be significant for serviceability limit states, and when failure rates are integrated in time, to provide lifetime failure probabilities. Herein, we present a novel formulation to fully avoid the error in integration of non-ergodic variables. The proposed product-of-lognormals formulation is fully compatible with popular fragility modelling approaches in PBE context. Moreover, we address collapse limit states of realistic reinforced concrete buildings, and find errors of the order of 5 to 8% for 50-year lifetimes, up to 14% for 100 years. Computation of accurate lifetime failure probabilities in a PBE context is clearly important, as it allows comparison with lifetime target reliability values for other structural analysis formulations.

A framework for operationalizing the assessment of post-earthquake functional recovery of buildings

Building damage after an earthquake, or other hazard event, can interrupt businesses, displace households, and significantly disrupt a community for years. As a result, policymakers and engineers are working toward new design guidelines and policies that reduce the vulnerability of the built environment through improved building functional recovery performance. This study proposes a method for assessing post-earthquake building performance states of function and reoccupancy within the architecture of performance-based earthquake engineering, targeted at US construction, making use of Federal Emergency Management Agency (FEMA) P-58 fragility and consequence models. This is accomplished by mapping component damage states to systems-level operational performance, and then to building-level performance states, through a series of fault trees. The study also proposes a repair scheduling algorithm to estimate the time taken to restore building reoccupancy or function, considering impeding factors that delay the start of repairs. The result is a probabilistic approach that extends the performance-based engineering framework to explicitly quantify post-earthquake building function performance states, thus facilitating design and mitigation decisions for recovery-based performance objectives.

Structural Fire Risk for Heritage Buildings by the Performance-Based Engineering Format

ABSTRACT This paper discusses and presents an example of fire risk analysis for a case study of an existing heritage building: the Duomo of Modena Cathedral, located in Italy. The main issues related to the application of the fire risk analysis to heritage buildings are discussed in detail, and an ad-hoc procedure is proposed to manage them for the case study. In order to assess the performances of the building in probabilistic terms, the fire risk analysis is conducted by the event-tree method, the fire dynamics are analyzed by numerical thermo-fluid dynamics models, while the structural behavior is investigated by advanced nonlinear thermomechanical finite element models. Results are expressed in terms of risk curves related to a fixed return period, which quantify the occurrence probability of different damage levels induced by fire in the wooden roof of the case study building. This kind of result is fully compatible with probabilistic performance-based engineering frameworks commonly accepted for other hazards (i.e., earthquakes).

Developing the structural analysis considering fuzzy performance levels

The concept of performance-based engineering in the seismic design and performance evaluation of structures has gained a significant development over the past few decades. The sample performance levels in current building codes are categorized into two levels that represent incipient damage and incipient collapse. Therefore, the performance limits of buildings involve numerous uncertainties such as the lack of clarity in their definition and ambiguity in the individual judgments. The main objective of this paper is to properly address the uncertainties in the performance levels and loading conditions through the evaluation process. The limit state for each performance level is defined as fuzzy numbers to model the fuzziness inherent in their interpretation. Moreover, the fuzzy set theory is adopted to estimate the desired fuzzy structural responses, considering the uncertainty involved in loading conditions within the analysis process. In addition, a novel fuzzy decision-making approach, which includes a comparison of the developed fuzzy sets (i.e., fuzzy structural response and fuzzy performance levels), is proposed to ensure a comprehensive assessment of the building performance. Numerical examples are also given to establish the application of the proposed method. The results demonstrate that the new comparing approach can make a reliable judgment, particularly in questionable cases of decision-making that are in line with the embedded context.

Geotechnical fragility analysis of monopile foundations for offshore wind turbines in extreme storms

Offshore wind turbines (OWTs) must withstand harsh environmental loads over their 20- to 30-year design life. Fragility analysis investigates the probability of damage over a range of hazard intensities and is integral to a performance-based engineering approach. The focus of this paper is on monopiles, which are widely used to support OWTs in water depths up to around 40m. The paper presents a fragility analysis of monopiles in extreme storms in terms of geotechnical performance, measured by permanent rotation of the foundation. Geotechnical fragility has so far not been comprehensively addressed due to the challenge of predicting soil behaviour under cyclic loading and estimating the probability of extreme responses. On the latter, the paper develops efficient Karhunen-Loeve representations of wind and wave loading that can be combined with inexpensive probabilistic methods to compute fragility. The framework was demonstrated using a representative scenario of a 5 MW OWT installed in clay. Non-linear foundation response was captured by a dynamic 3D finite element model. Fragility curves were generated using subset simulation for storms with return periods (RPs) from 1 to 100 years. Fragility during extreme storms (with 50- and 100-year RPs) was significantly higher than storms with RPs of 10 years or less.

Material point method for large-deformation modeling of coseismic landslide and liquefaction-induced dam failure

In this study, Material Point Method (MPM) is improved to simulate coseismic slope stability and liquefaction-induced embankment failure under earthquake loading. First, by using elastic or elastoplastic models, topographic amplification and different slope failure modes are analyzed considering the effects of slope geometry, soil properties and excitation frequencies etc. The MPM model is then applied to predict a cascading slope failure process, including triggering, shear band formation, runoff and final deposition. Finally, a fully nonlinear bounding surface soil model is implemented in the two-phase soil-water coupled MPM framework to investigate the liquefaction mechanism and associated dam failure using two case histories. The numerical results are generally comparable with the post-failure profiles obtained from field investigation, which highlight the advantage of MPM in handling liquefaction-induced large deformation. The MPM shows great promise to quantitatively assess risk and consequence associated with seismic slope failure and soil liquefaction, thereby, advance the performance-based engineering design and analysis.

Seismic Effects on Different Structural Members

Civil engineers deal with constructing differing types of structures with guaranteeing safety, sturdiness and utility. Currently days “earthquake “is a natural tragedy that affects the structures with their safety and utility. The quantity of harm that earthquake will cause to structures is rely upon sort of building, sort of soil, Technology used for earthquake resistance, and last however not the smallest amount Location of building. Effects of earthquake area unit mostly counting on sort of soil within which foundation of building is finished as a result of earthquake changes the motion of ground that results the failure foundation. Therefore it's vital to check the behavior of various soils at the time of construction of structures. Earthquake will be resisted by varied technologies utilized in building, one amongst these area unit shear wall. It improves the structural performance of building subjected to lateral forces because of earthquake excitation. Much analysis comes area unit afoot worldwide for development of effective ways for estimating unstable demands for performance-based engineering of buildings.