Performance-based Engineering Framework Research Articles

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.

Performance-Based Coastal Engineering Framework

The changing dynamics of coastal regions and climate pose severe challenges to coastal communities around the world. Effective planning of engineering projects and resilience strategies in coastal regions must not only address current conditions but also take into consideration the expected changes in the exposure and multi-hazard risk in these areas. However, existing performance-based engineering frameworks generally neglect time-varying factors and miss the opportunity to leverage related evidence as it becomes available. This paper proposes a Performance-Based Coastal Engineering (PBCE) framework that is flexible enough to accommodate uncertain time-varying factors, multi-hazard conditions, and cascading-effects. Furthermore, using a dynamic Bayesian network approach, the framework can incorporate observed evidence into the model to update the prior conditional distribution of the analyzed variables. As a proof of concept, two case studies—a typical elevated residential structure and a two-frame system—are presented, considering the effects of cascading failure, the incorporation of time-varying factors, and the influence of emerging evidence. Results show that neglecting cascading effects significantly underestimates the losses and that the incorporation of evidence reduces the uncertainty under the assumed distribution of evidence. The resulting PBCE framework can support data collection efforts, optimization of retrofitting strategies, integration of experts and community interests by facilitating interactions and knowledge sharing, as well as the identification of vulnerable regions and critical components in coastal multi-hazard regions.

Performance-based decision-making of buildings under seismic hazard considering long-term loss, sustainability, and resilience

It is of vital importance to incorporate sustainability and resilience in the performance-based decision-making of civil infrastructure under seismic hazard. However, a performance-based engineering framework utilizing component-level approach, integrating seismic loss, sustainability, and resilience in a multi-criteria decision-making (MCDM) is not yet extensively developed particularly for retrofit selection in a long-term perspective. This paper introduces a framework utilizing performance-based approach to couple seismic loss, sustainability, and resilience in decision-making framework for selection of different retrofit alternatives. A component-based probabilistic approach is developed for the seismic loss, sustainability, and resilience assessment in a long-term perspective. The resulting social, economic, and environmental consequences are converted to expected annual consequences (EACs) by considering the full range of seismic hazards, and are utilized as a multi-criterion in the technique for order preference by similarity to ideal solution (TOPSIS). The proposed long-term performance-based multi-criteria decision-making (PB-MCDM) framework considers five consequences, which include cost, casualties, equivalent carbon emissions, embodied energy, and repair time. Based on the illustrative example, it may be concluded that incorporating seismic sustainability and resilience in PB-MCDM approach in a long-term perspective can provide ideal solutions and better decision-making against retrofit alternatives.

Life-Cycle Cost Analysis of a Point-Like Structure Subjected to Tornadic Wind Loads

To quantify the monetary losses associated with damages induced by tornado wind storms, a numerical performance-based engineering framework complete with dynamic simulation of tornado-like wind fields, calculation of probabilities of structural performance for a point-like (monopole) structure and life-cycle cost analysis is presented. Within a Monte Carlo sampling environment, digitally simulated loads generated from five distinct tornado wind field models replicate aleatory and epistemic uncertainties concentrated in the aerodynamic load coefficients and turbulent wind velocities. Using random maximum displacements and base-bending moments as engineering demand parameters, the convolution of fragility functions with hazard curves for three intensity measures (maximum tangential velocity, core radius of the simulated tornado, and starting location of the tornado) yield probabilities of structural failure for selected limit states. The shapes of the integrand probability surfaces and the subsequent estimations of relative costs exhibit significant differences among the five models despite the parametrically equivalent simulations. This initial study, though limited through its case analysis of a point-like (monopole) structure, sets the stage for future investigations of life-cycle costs for other vertical structures (e.g., tall buildings) subjected to tornadic wind loads.

Comparative study on acceptance criteria for non-ductile reinforced concrete columns

Poor seismic performance of older reinforced concrete buildings in past seismic events has frequently been attributed to failure of non-ductile columns not detailed for seismic demands. The Seismic Assessment of Existing Buildings Guidelines developed in New Zealand (NZ Guideline) provides a performance-based engineering framework for assessment of existing buildings, with concrete buildings covered in section C5. This study compares the probable failure mode and deformation capacity assessed based on NZ Guideline, ASCE/SEI 41-13, and ASCE/SEI 41-17 with the results from quasi-static cyclic tests conducted on 52 rectangular and 13 circular reinforced concrete columns with reinforcement details similar to those of non-ductile columns. Results indicate that the general curvature-based method of the NZ Guideline was not able to identify the observed failure mode but generally provides a conservative estimate of deformation capacity in comparison with ASCE/SEI 41-17. Based on the results of this study, a direct rotation-based acceptance criteria is proposed for NZ Guidelines. Also, slight modifications, to reduce conservatism, have been proposed for the curvature-based method.

Climate change and extreme wind effects on transmission towers

Climate change poses a major threat to electricity power infrastructure due to expected increases in the magnitude and frequency of extreme storm events. This paper uses a methodology for assessment of the vulnerability of UK transmission tower infrastructure to such events, within a framework of performance-based engineering. The challenge of estimating future storm magnitudes is addressed by applying a change factor methodology to present-day wind speeds using information provided by the 2009 UK climate change projections. A Weibull distribution is employed to obtain wind speeds for storm events at different recurrence intervals. Wind loading on the structure and cables is then determined using Eurocodes, and the structure is analysed using pseudo-static finite-element analysis, considering material and geometrical non-linearity as well as linear and non-linear buckling effects. The outcome of the research is that, despite a significant projected increase in wind velocities due to climate change, the typical tower analysed in the study continues to perform satisfactorily at all hazard levels. If this performance can be demonstrated more generally across the UK transmission tower infrastructure network, then it is likely that the cause can be traced back to the high factor of safety applied in the original design of the towers.

Experimental fragility curves for aluminum storm panels subject to windborne debris impact

This paper presents the derivation of experimental fragility curves for windborne debris (WBD) impact risk assessment of aluminum storm panels within a recently developed performance-based hurricane engineering (PBHE) framework. By using a pneumatic wind cannon, rod-type WBDs were fired at aluminum storm panels to evaluate the effects of WBD impact hazard. The experimental data from testing were used to derive the probability of failure relative to specific damage measures (DMs) versus its corresponding interaction parameter (IP). These experimentally derived probabilities were also compared with finite element-based results that were available in the literature.It was found that the impact kinetic energy of rod-type missiles is a sufficient IP for aluminum storm panels subjected to WBD impact, the probability of penetration of aluminum storm panels is strongly dependent on the details of the panels׳ installation, and the numerical results available in the literature regarding the fragility curves of storm panels are qualitatively representative of the behavior of aluminum storm panels subject to WBD impact. It is noteworthy that accurate fragility curves are essential in the development of a general probabilistic performance-based engineering framework for mitigation of WBD impact hazard.

Snow load damage to buildings: physical and economic impacts

This study examines the physical and economic impacts of snow-related building failures occurring in the USA between autumn 2008 and spring 2011. The study employed a web-based survey distributed to owners and operators of 332 buildings. These buildings were identified in newspaper archives or online news sources as having been damaged by snow loads. This paper describes the 40 responses received. Damage to these buildings ranged from minor to complete collapse; survey responses showed that the roof structure and non-structural roofing and ceiling materials were particularly impacted. Certain structural types (especially timber roofed) and older buildings tended to experience higher levels of damage. On average, the buildings incurred US$ 166 per gross m2 of costs associated with repairing or rebuilding, damaged US$ 25 per gross m2 of property and building contents, and interrupted business or other operations for 122 days. Collection of these data represents a first step towards the development of loss estimation models needed for a comprehensive performance-based engineering framework for the design and assessment of buildings under snow loads.

Fragility curves for building envelope components subject to windborne debris impact

This paper presents a methodology for developing windborne debris (WBD) impact fragility curves for building envelope components (BECs) by using stochastic finite element (FE) models. These fragility curves provide the probabilistic description of the impact resistance of BECs subject to an impact event described by an appropriate intensity measure (IM). Accurate fragility curves are essential in the development of a general probabilistic performance-based engineering framework for mitigation of WBD impact hazard.Monte Carlo simulation is used in combination with the FE method to propagate uncertainties in the BEC's model parameters and WBD impact location. As an application example, the fragility curves relative to different damage states are derived for aluminum storm shutters subjected to WBD impact. It is found that (1) the missile kinetic energy at impact is a sufficient IM for BECs with ductile behavior subjected to WBD impact, and (2) the performance of storm panels in terms of penetration of WBDs is critically dependent on the details of the panels’ installation.

Overview of the U.S. Program for Reduction of Earthquake Hazards in Steel Moment-Frame Structures

Considerable research has been conducted worldwide to assess the unexpected damage to welded steel moment-frame buildings during the 1989 Loma Prieta, 1994 Northridge, and 1995 Hyogo-ken Nanbu earthquakes, as well as to find effective and economical remedies that can be incorporated into analysis, design, and construction practices. A major six-year program has been undertaken with the sponsorship of the U.S. Federal Emergency Management Agency (FEMA) to synthesize and interpret the results of this research, and to conduct additional investigations to develop reliable, practical, and cost-effective guidelines for the design and construction of new steel moment-frame structures, as well as for the inspection, evaluation and repair or upgrading of existing ones. Topics investigated as part of this program include (1) performance of steel buildings in past earthquakes; (2) material properties and fracture issues; (3) joining and inspection; (4) connection performance; (5) system performance; (6) performance prediction and evaluation; and (7) social, economic, and political impacts. The project utilizes a performance-based engineering framework and addresses issues pertaining to various types of steel moment-resisting frames including those utilizing welded, bolted, and partially restrained connections. The guidelines are applicable to regions of low, medium, and high seismicity throughout the United States. This paper reviews the overall organization and management of this program of research, guideline development, training and peer evaluation, the scope of the investigations undertaken, and the general organization and contents of the guidelines developed.

Overview of the FEMA/SAC program for reduction of earthquake hazards in steel moment frame structures

Considerable research has been conducted worldwide to assess the unexpected damage to welded steel moment-frame buildings during the 1989 Loma Prieta, 1994 Northridge and 1995 Hyogo-ken Nanbu earthquakes, as well as to find effective and economical remedies that can be incorporated into analysis, design, and construction practices. A major 6-year program was undertaken sponsored by the US Federal Emergency Management Agency (FEMA) synthesized and interpreted the results of this research, and conducted additional investigations to develop reliable, practical and cost-effective guidelines for the design and construction of new steel moment-frame structures, as well as for the inspection, evaluation and repair or upgrading of existing ones. Topics investigated as part of this program included: (1) performance of steel buildings in past earthquakes; (2) material properties and fracture issues; (3) joining and inspection; (4) connection performance; (5) system performance; (6) performance prediction and evaluation; and (7) social, economic and political impacts. The project utilized a performance-based engineering framework and addresses issues pertaining to various types of steel moment-resisting frames including those utilizing welded, bolted, and partially restrained connections. Published late in 2000 by FEMA, the guidelines are applicable to regions of low, medium and high seismicity throughout the US. This paper reviews the overall organization and management of this program of research, guideline development, training and peer evaluation, the scope of the investigations undertaken, and the general organization and contents of the guidelines developed.