Consideration of Post-Repair Performance in Seismic Loss Assessment of Structures

Performance-based earthquake engineering is a methodology that allows for seismic assessment of structures in terms of decision variables that are most important to stakeholders. However, currently, this approach does not facilitate consideration of changes in structural behavior if the structure is repaired, and, hence, cannot be used to compare service life performance differences between the different repair strategies. This study develops and illustrates a probabilistic seismic loss assessment framework that explicitly considers structural post-repair performance and examines the implications of the selected repair strategies over remaining service life of the structure after an earthquake. The proposed framework uses the Monte Carlo method to simulate many service life scenarios of a structure that are consistent with site-specific seismic hazard. For each of these scenarios, expected losses are calculated, considering changes in the performance of the structure if previous earthquake in the scenario warrants extensive repair that changes structural behavior. The framework is applied to two reinforced concrete bridges to illustrate its application.This research was supported by National Science Foundation (NSF) under Award No. CMMI 1538585/1748031

Multi-Hazard Housing Safety Perceptions of Those Involved with Housing Construction in Puerto Rico

&nbsp; Globally, hazards are increasingly threatening housing each year, and housing constructed outside the formal sector may be particularly vulnerable. Yet, limited studies have investigated the perceptions of those responsible for designing and building this housing. These safety perceptions motivate the informal housing construction practices that ultimately determine housing safety. Thus, this study investigates the multi-hazard housing safety perceptions of individuals involved with housing construction in Puerto Rico. We surveyed 345 builders and hardware store employees across Puerto Rico to understand their perceptions of expected housing damage in hurricanes and earthquakes, important mitigation measures, and barriers to safer housing construction. Our results reveal that prior hazard experience did not influence perceptions of expected housing damage, but previous housing construction experience did. Respondents viewed wood and concrete housing as less safe in hurricanes and earthquakes, respectively. Yet, respondents appeared uncertain about the importance of mitigation measures for concrete houses in earthquakes, likely due to a combination of limited earthquake experience and &ldquo;hidden&rdquo; reinforcement detailing in a reinforced concrete house. Interestingly, our results also show that respondents perceive technical construction capacity as a major barrier to safer informal housing construction rather than resource constraints alone. These findings suggest areas for technical construction capacity development for Puerto Rico&rsquo;s informal construction sector.</div

Preliminary Magnitude and Distance Damage Thresholds for Light-Frame Wood Buildings in Induced Earthquakes

Since 2009, the frequency of (moment) magnitude (Mw) 3.0 earthquakes and larger in the Central United States, and especially Oklahoma (OK), has risen from an average of 2 per year, to 200-700 per year. This increase in seismicity is a result of injection of large quantities of wastewater generated from oil and gas activities deep underground. In this study, damage to built infrastructure from induced earthquakes is investigated through nonlinear dynamic analysis and probabilistic damage assessment for a light-frame wood structure. Specifically, we focus here on investigating the smallest Mw injectioninduced earthquake that may cause damage to the building of interest at various distances from the hypocenter (R). The simulations are based on a two-story multifamily dwelling, which is designed with lateral strength and detailing consistent with modern code requirements in Pawnee, OK. For a Mw 4.5 earthquake, damage is observed at R = 15 km or closer. While for an earthquake R = 3 km from the site, damage is observed 56% of the time at Mw 4.5 and occurs 100% of the time when Mw 5.5 and above.This research was supported by the National Science Foundation under award number 1520846 and by the Civil, Architectural, and Environmental Engineering at the University of Colorado, Boulder

A Framework for the Evaluation of Liquefaction Consequences for Shallow-Founded Structures

Performance-based earthquake engineering is increasingly being used to inform decision-making regarding seismic design. Recent research has provided a number of procedures that yield information needed for the development of a performance-based framework for liquefaction engineering. This study proposes a structure for such a framework for application to shallow-founded structures and identifies procedures that are key to its use. Procedures used in such performance-based engineering frameworks must offer a probabilistic estimate of hazard, demand, and/or damage, rather than a simple deterministic estimate. The framework includes analysis of both foundation and structural performance. The foundation may be subject to settlement and residual tilt if subsurface layers of soil liquefy. Although liquefaction generally reduces the acceleration demand on the superstructure, it may still cause significant damage to nonstructural components or lead to casualties. Further, the framework is organized with mitigation decision-making in mind. Mitigation may reduce the impact of foundation damage, but is expected to simultaneously increase the demand on the superstructure. Decisions about whether to mitigate, and how, must consider this tradeoff.This research was supported by the United States Department of Education under award number P200A150042 and by the Civil, Architectural, and Environmental Engineering department at the University of Colorado, Boulder

Modelación y análisis no lineal de muros estructurales de hormigón armado

The severe damage and collapse of many reinforced concrete (RC) wall buildings observed in recent earthquakes in Chile (2010) and New Zealand (2011) showed that RC walls did not perform as required by the building codes of both countries. In this context, it is necessary to intensify the research efforts towards more precise simulations of damage indicators, particularly of local engineering demand parameters, such as material strains, which are fundamental for the application of the Performance-Based Earthquake Engineering (PBEE) methodology. The main goal of this study is to propose an analytical nonlinear model capable of simulating the response of isolated reinforced concrete walls at a global and local level. This work compared different response parameters obtained from nonlinear analysis of RC walls subjected to cyclic loads, using finite element models developed with DIANA software. The modeling approach was validated with experimental data from two RC walls. A sensitivity analysis of the seismic response parameters to uncertain modeling variables such as the compressive fracture energy of unconfined and confined concrete, among others, was also performed. The analytical models adequately captured the lateral force-displacement relationship, stiffness degradation, and the profile of vertical strains at the base of the walls for different levels of demand. The sensitivity analysis showed that the dispersion of the local response is greater than the dispersion in the global response when considering different modeling parameters. Dispersion increases as the level of demand increases. Manuscript received: October 7, 2021Manuscript accepted: November 18, 2021El daño severo y el colapso de edificios de muros de hormigón armado (HA) observado en terremotos recientes en Chile (2010) y Nueva Zelanda (2011) mostraron que los muros de HA no se desempeñaron acorde a la exigencia de los códigos de ambos países.&nbsp; En este contexto es necesario intensificar los esfuerzos de investigación hacia simulaciones más precisas de los indicadores de daños, particularmente de los parámetros de demanda ingenieril local, como deformaciones del material, que son fundamentales para la aplicación del método de ingeniería sísmica basada en desempeño. El objetivo principal de este estudio es proponer un modelo analítico no lineal capaz de simular la respuesta de muros aislados de hormigón armado a nivel global y local. Este trabajo comparó diferentes parámetros de respuesta obtenidos del análisis no lineal de muros de HA sometidos a cargas cíclicas, mediante modelos de elementos finitos desarrollados en el programa DIANA. El enfoque de modelado se validó con datos experimentales de dos muros de HA. Se realizó también un análisis de sensibilidad de los parámetros de respuesta sísmica a las variables de modelado inciertas como la energía de fractura en compresión del hormigón no confinado y confinado, entre otras. Los modelos analíticos capturaron adecuadamente la relación fuerza lateral-desplazamiento, la degradación de la rigidez y el perfil de deformaciones verticales en la base de los muros para diferentes niveles de demanda. El análisis de sensibilidad indicó que la dispersión de la respuesta local es mayor que la dispersión en la respuesta global, al considerar diferentes parámetros de modelado. La dispersión aumenta a medida que aumenta el nivel de demanda. Artículo recibido: 7 de octubre de 2021 Artículo aceptado: 18 de noviembre de 202

Hazard Implications of the 2016 Mw 5.0 Cushing, OK Earthquake from a Joint Analysis of Damage and InSAR Data

The Cushing Hub in Oklahoma, one of the largest oil storage facilities in the world, is federally designated as critical national infrastructure. In 2014, the formerly aseismic city of Cushing experienced a Mw 4.0 and 4.3 induced earthquake sequence due to wastewater injection. Since then, an M4+ earthquake sequence has occurred annually (October 2014, September 2015, November 2016). Thus far, damage to critical infrastructure has been minimal; however, a larger earthquake could pose significant risk to the Cushing Hub. In addition to inducing earthquakes, wastewater injection also threatens the Cushing Hub through gradual surface uplift. To characterize the impact of wastewater injection on critical infrastructure, we use Differential Interferometric Synthetic Aperture Radar (DInSAR), a satellite radar technique, to observe ground surface displacement in Cushing before and during the induced Mw 5.0 event. Here, we process interferograms of Single Look Complex (SLC) radar data from the European Space Agency (ESA) Sentinel-1A satellite. The preearthquake interferograms are used to create a time series of cumulative surface displacement, while the coseismic interferograms are used to invert for earthquake source characteristics. The time series of surface displacement reveals 4⁻5.5 cm of uplift across Cushing over 17 months. The coseismic interferogram inversion suggests that the 2016 Mw 5.0 earthquake is shallower than estimated from seismic inversions alone. This shallower source depth should be taken into account in future hazard assessments for regional infrastructure. In addition, monitoring of surface deformation near wastewater injection wells can be used to characterize the subsurface dynamics and implement measures to mitigate damage to critical installations

A Call to Refocus Research Goals for the Development of Seismic Optimization Methods

4 páginasAt present, there exist a significant number of optimization methods that are veryeffective for determining the properties of structures that satisfy a given seismic designor performance objective. This advancement has been possible thanks to a steady paceof development carried out by researchers. Yet these methods have not been widely adoptedby practicing engineers, most of whom still use a traditional iterative procedure for structuraldesign.This situation has motivated us to ask ourselves if those of us who conduct research inthis area are focusing our efforts in the most strategic direction. This document is an openinvitation to discuss this issue, with the aim to promote a collective reflection of our presentwork, in order to set the best directions for future research efforts in this important are

Multi-Hazard Housing Safety Perceptions of Those Involved with Housing Construction in Puerto Rico

Globally, hazards are increasingly threatening housing each year, and housing constructed outside the formal sector may be particularly vulnerable. Yet, limited studies have investigated the perceptions of those responsible for designing and building this housing. These safety perceptions motivate the informal housing construction practices that ultimately determine housing safety. Thus, this study investigates the multi-hazard housing safety perceptions of individuals involved with housing construction in Puerto Rico. We surveyed 345 builders and hardware store employees across Puerto Rico to understand their perceptions of expected housing damage in hurricanes and earthquakes, important mitigation measures, and barriers to safer housing construction. Our results reveal that prior hazard experience did not influence perceptions of expected housing damage, but previous housing construction experience did. Respondents viewed wood and concrete housing as less safe in hurricanes and earthquakes, respectively. Yet, respondents appeared uncertain about the importance of mitigation measures for concrete houses in earthquakes, likely due to a combination of limited earthquake experience and &ldquo;hidden&rdquo; reinforcement detailing in a reinforced concrete house. Interestingly, our results also show that respondents perceive technical construction capacity as a major barrier to safer informal housing construction rather than resource constraints alone. These findings suggest areas for technical construction capacity development for Puerto Rico&rsquo;s informal construction sector