Structural performance of buildings during the 30 November 2018 M7.1 Anchorage, Alaska earthquake

Southcentral Alaska, the most populous region in Alaska, was violently shaken by a Mw 7.1 earthquake on 30 November 2018 at 8:29 am Alaska Standard Time. This was the largest magnitude earthquake in the United States close to a population center in over 50 years. The earthquake was 46 km deep, and the epicenter was 12 km north of Anchorage and 19 km west of Eagle River. The event affected some 400,000 residents, causing widespread damage in highways, nonstructural components, non-engineered and older buildings, and structures on poorly compacted fills. A few isolated serious injuries and partial collapses took place. Minor structural damage to code-conforming buildings was observed. A significant percentage of the structural damage was due to geotechnical failures. Building stock diversity allows use of the region as a large test bed to observe how local building practices affected earthquake damage levels. The prevailing peak ground acceleration (PGA) was 0.2–0.32 g, causing shaking intensity at most sites of 50%–60% of the ASCE 7-16 design basis earthquake acceleration. Thus, the seismic vulnerability of building stock in the region was not truly tested. Reinforced concrete buildings had minor structural damage, except in a few cases of shear wall and transfer girder shear cracking. Fiber-reinforced polymer (FRP)-retrofitted buildings performed satisfactorily. Concrete-masonry-unit (CMU) masonry buildings experienced serious structural damage in many cases, including relatively newer buildings. The earthquake caused widespread structural damage in non-engineered buildings (primarily wood and CMU masonry) that exist widely in the region, especially in Eagle River. Of these, non-engineered single-family wood buildings had the heaviest structural damage. No structural damage could be observed in steel buildings. The aftershock sequence, which included 7 M5+ and 50 M4+ events, exacerbated structural damage in all types of buildings. The present study is based on the EERI field reconnaissance mission conducted by the authors following the earthquake. Based on the observed damage and structural performance, seismic risk mitigation recommendations are suggested.

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Fragility curves for Italian URM buildings based on a hybrid method

Bulletin of Earthquake Engineering ◽

10.1007/s10518-021-01155-4 ◽

2021 ◽

Author(s):

A. Sandoli ◽

G. P. Lignola ◽

B. Calderoni ◽

A. Prota

Keyword(s):

Seismic Vulnerability ◽

Fragility Curves ◽

Limit State ◽

Ultimate Limit State ◽

Masonry Building ◽

Masonry Buildings ◽

Seismic Behaviour ◽

Building Stock ◽

Ground Acceleration ◽

Damage Scenario

AbstractA hybrid seismic fragility model for territorial-scale seismic vulnerability assessment of masonry buildings is developed and presented in this paper. The method combines expert-judgment and mechanical approaches to derive typological fragility curves for Italian residential masonry building stock. The first classifies Italian masonry buildings in five different typological classes as function of age of construction, structural typology, and seismic behaviour and damaging of buildings observed following the most severe earthquakes occurred in Italy. The second, based on numerical analyses results conducted on building prototypes, provides all the parameters necessary for developing fragility functions. Peak-Ground Acceleration (PGA) at Ultimate Limit State attainable by each building’s class has been chosen as an Intensity Measure to represent fragility curves: three types of curve have been developed, each referred to mean, maximum and minimum value of PGAs defined for each building class. To represent the expected damage scenario for increasing earthquake intensities, a correlation between PGAs and Mercalli-Cancani-Sieber macroseismic intensity scale has been used and the corresponding fragility curves developed. Results show that the proposed building’s classes are representative of the Italian masonry building stock and that fragility curves are effective for predicting both seismic vulnerability and expected damage scenarios for seismic-prone areas. Finally, the fragility curves have been compared with empirical curves obtained through a macroseismic approach on Italian masonry buildings available in literature, underlining the differences between the methods.

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Damage to Steel Buildings Observed after the 2011 Tohoku-Oki Earthquake

Earthquake Spectra ◽

10.1193/1.4000124 ◽

2013 ◽

Vol 29 (1_suppl) ◽

pp. 219-243 ◽

Cited By ~ 20

Author(s):

Taichiro Okazaki ◽

Dimitrios G. Lignos ◽

Mitsumasa Midorikawa ◽

James M. Ricles ◽

Jay Love

Keyword(s):

Seismic Design ◽

Tsunami Wave ◽

Structural Performance ◽

Building Structures ◽

Braced Frames ◽

Steel Buildings ◽

Ground Acceleration ◽

The City ◽

Insight Into ◽

Foundation Failure

A joint U.S.–Japan reconnaissance team examined the damage to steel building structures caused by the 2011 Tohoku-oki earthquake. In the city of Sendai, where the peak horizontal ground acceleration exceeded 1 g, the majority of steel buildings performed well. Buildings that used older cladding systems for external finish sustained damage to their claddings even if their structural performance was excellent. Damage to a few braced frames offer insight into the seismic design of bracing connections. In areas attacked by the violent tsunami, many steel buildings stood upright after the tsunami subsided, although these buildings lost much of their external and internal finishes along with their contents. These steel buildings did not provide safe shelter for tsunami evacuation when the building submerged under the tsunami wave. A number of buildings suffered foundation failure, which was likely caused by scouring or liquefaction or a combination of multiple effects.

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Fragility Curves for Italian Urm Buildings Based on a Hybrid Method

10.21203/rs.3.rs-341542/v1 ◽

2021 ◽

Author(s):

Antonio Sandoli ◽

Gian Piero Lignola ◽

Bruno Calderoni ◽

Andrea Prota

Keyword(s):

Seismic Vulnerability ◽

Fragility Curves ◽

Limit State ◽

Ultimate Limit State ◽

Masonry Building ◽

Masonry Buildings ◽

Seismic Behaviour ◽

Building Stock ◽

Ground Acceleration ◽

Damage Scenario

Abstract A hybrid seismic fragility model for territorial-scale seismic vulnerability assessment of masonry buildings is developed and presented in this paper. The method combines expert-judgment and mechanical approaches to derive typological fragility curves for Italian residential masonry building stock. The first classifies Italian masonry buildings in five different typological classes as function of age of construction, structural typology, and seismic behaviour and damaging of buildings observed following the most severe earthquakes occurred in Italy. The second, based on numerical analyses results conducted on building prototypes, provides all the parameters necessary for developing fragility functions.Peak-Ground Acceleration (PGA) at Ultimate Limit State attainable by each building’s class has been chosen as an Intensity Measure (IM) to represent fragility curves: three types of curve have been developed, each referred to mean, maximum and minim value of PGAs defined for each buildings class.To represent the expected damage scenario for increasing earthquake intensities, a correlation between PGAs and Mercalli-Cancani-Sieber (MCS) macroseismic intensity scale has been used and the corresponding fragility curves developed.Results show that the proposed building’s classes are representative of the Italian masonry building stock and that fragility curves are effective for predicting both seismic vulnerability and expected damage scenarios for seismic-prone areas. Finally, the fragility curves have been compared with empirical curves obtained through a macroseismic approach on Italian masonry buildings available in literature, underlining the differences between the methods.

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The Seismic Provisions of the 1997 Uniform Building Code

Earthquake Spectra ◽

10.1193/1.1586084 ◽

2000 ◽

Vol 16 (1) ◽

pp. 85-100 ◽

Cited By ~ 3

Author(s):

Robert E. Bachman ◽

David R. Bonneville

Keyword(s):

The United States ◽

Site Amplification ◽

Major Elements ◽

Building Code ◽

Ground Acceleration ◽

Reliability Factor ◽

Nonstructural Components ◽

Source Effects ◽

Story Drift ◽

Soil Site

Currently the most widely accepted code regulations in the United States for seismic design of structures and nonstructural components are those found in the Uniform Building Code ( UBC). The UBC seismic requirements were significantly revised in the 1997 edition. Among the issues addressed in the UBC revisions are near-source effects and ground acceleration dependent soil site amplification factors for both short- and long-period structures. Also, the design force levels in the 1997 UBC are based on strength design rather than allowable stress design, as had been used previously. Other significant changes include introduction of a redundancy/reliability factor, a more realistic consideration of story drift and deformation compatibility, and new equations for equivalent static forces for both structural and nonstructural components. This paper traces the recent history of the code development and describes the major elements of the 1997 UBC seismic provisions.

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Systematic Seismic Design for Manageable Loss in Wood-Framed Buildings

Earthquake Spectra ◽

10.1193/1.3240412 ◽

2009 ◽

Vol 25 (4) ◽

pp. 851-868 ◽

Cited By ~ 5

Author(s):

Shiling Pei ◽

John W. van de Lindt

Keyword(s):

Seismic Design ◽

Design Procedure ◽

Residential Building ◽

The United States ◽

Single Family ◽

Financial Loss ◽

End User ◽

Building Stock ◽

Framed Structures ◽

Performance Based Seismic Design

Light frame wood structures make up the vast majority of the residential building stock in the United States. Because of this, earthquake-induced losses for this category of building from a significant earthquake would have a substantial financial impact on the regional economy, as well as on the building owner. Current wood-framed structural design philosophy focuses only on life safety and only limits damage through implicit assumptions. The concept of loss-based seismic design is introduced in this paper with typical loss-based design statements explicitly formulated with the intent of addressing the concerns, e.g., financial loss, of the building end-user. The loss-based design procedure was established based on a loss estimation framework that relied on the existing concept of assembly-based vulnerability (ABV). With the help of an automated dynamic and loss analysis package developed for wood-framed structures (SAPWood™) at Colorado State University, loss-based seismic design for a typical North American single family residential building was conducted for several different explicitly stated loss targets. The results from the numerical examples showed that loss-based seismic design for wood-framed structures is a viable concept that can serve as an important step in the evolution of end-user oriented, performance-based seismic design (PBSD).

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Seismic Vulnerability Assessment of Portuguese Adobe Buildings

Buildings ◽

10.3390/buildings11050200 ◽

2021 ◽

Vol 11 (5) ◽

pp. 200

Author(s):

Samar Momin ◽

Holger Lovon ◽

Vitor Silva ◽

Tiago Miguel Ferreira ◽

Romeu Vicente

Keyword(s):

Structural Damage ◽

Seismic Vulnerability ◽

Linear Time ◽

Time History ◽

Building Stock ◽

Seismic Vulnerability Assessment ◽

Ground Shaking ◽

Brittle Behavior ◽

Historical Significance ◽

Ground Motion Records

Adobe construction represents 5.3% of the total Portuguese building stock according to the latest National Housing Census. The distribution of these adobe buildings is scattered across the country, with higher density in the central region and in Algarve in the south, where the seismic hazard is highest. A large proportion of these buildings are still in use for residential and commercial purposes and are of historical significance, contributing to the cultural heritage of the country. Adobe buildings are known to exhibit low seismic resistance due to their brittle behavior, thus making them vulnerable to ground shaking and more prone to structural damage that can potentially cause human fatalities. Three buildings with one-story, two-stories, and two-stories plus an attic were numerically modeled using solid and contact elements. Calibration and validation of material properties were carried out following experimental results. A set of 30 ground motion records with bi-directional components were selected, and non-linear time-history analyses were performed until complete collapse occurred. Two novel engineering demand parameters (EDPs) were used, and damage thresholds were proposed. Finally, fragility and fatality vulnerability functions were derived. These functions can be used directly in seismic risk assessment studies.

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A deterministic seismic risk macrozonation of Seville

Arabian Journal of Geosciences ◽

10.1007/s12517-021-08626-7 ◽

2021 ◽

Vol 14 (22) ◽

Author(s):

Luis Fazendeiro Sá ◽

Antonio Morales-Esteban ◽

Percy Durand Neyra

Keyword(s):

Seismic Hazard ◽

Seismic Risk ◽

Seismic Vulnerability ◽

Standard Penetration Test ◽

Mitigation Strategies ◽

Civil Protection ◽

Emergency Plan ◽

Seismic Behaviour ◽

Building Stock ◽

Ground Acceleration

The seismicity of the southwestern Iberian Peninsula is moderate but large events with long return periods occur (≈ 200 years). This exceeds the life of various generations, making the population unacquainted with the seismic hazard. On the one hand, this results in a low demanding seismic code which increases the seismic vulnerability and, therefore, the seismic risk. On the other hand, the local emergency services must be properly prepared to face a destructive seismic event, with emergency plans and mitigation strategies. This assumption enhances the need of assessing the seismic risk of Seville in a civil protection context. For all the aforementioned and for the lack of instrumental data of relevant earthquakes, the assessment of the seismic hazard in this area is challenging. To do this, seismogenic zones of the new seismic hazard map of Spain have been used as sources. The peak ground acceleration (PGA) for each scenario has been calculated by means of ground motion prediction equations (GMPE). To estimate the site effects, in a 1D model environment, a shear wave velocity (Vs) map of the top 5 m has been depicted based on the standard penetration test (SPT). Seville’s building stock has been classified in agreement with the previous works in Lorca and Barcelona to determine its vulnerability. The main goal of this work was to investigate the influence of the soil amplification on the seismic behaviour of different building typologies. Therefore, the final target was to plot the damage scenarios expected in Seville under a maximum credible earthquake by means of a deterministic seismic hazard assessment (DSHA). As outputs, the scenario modelled showed that around 27 000 buildings would experience a moderate damage and that 26 000 would suffer pre-collapse or even collapse. Thus, approximately 10% of the population would lose their dwellings. Regarding the human loses, around 22 000 people would suffer serious injuries and approximately 5 000 people would die. Owing to these conclusions, this research evidences the crucial need by civil protection services to implement a local emergency plan as a tool to mitigate the probable consequences that arise from this threat.

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Seismic Vulnerability Assessment of Historical Masonry Buildings in Croatian Coastal Area

Applied Sciences ◽

10.3390/app11135997 ◽

2021 ◽

Vol 11 (13) ◽

pp. 5997

Author(s):

Željana Nikolić ◽

Luka Runjić ◽

Nives Ostojić Škomrlj ◽

Elena Benvenuti

Keyword(s):

Seismic Vulnerability ◽

Pushover Analysis ◽

Damage Index ◽

Stone Masonry ◽

Masonry Buildings ◽

Building Stock ◽

Ground Acceleration ◽

Index Method ◽

Vulnerability Index Method ◽

Non Linear

(1) Background: The protection of built heritage in historic cities located in seismically active areas is of great importance for the safety of inhabitants. Systematic care and planning are necessary to detect the seismic vulnerability of buildings, in order to determine priorities in rehabilitation projects and to continuously provide funds for the reconstruction of the buildings. (2) Methods: In this study, the seismic vulnerability of the buildings in the historic center of Kaštel Kambelovac, a Croatian settlement located along the Adriatic coast, has been assessed through an approach based on the calculation of vulnerability indexes. The center consists of stone masonry buildings built between the 15th and 19th centuries. The seismic vulnerability method was derived from the Italian GNDT approach, with some modifications resulting from the specificity of the buildings in the investigated area. A new damage–vulnerability–peak ground acceleration relation was developed using the vulnerability indexes and the yield and collapse accelerations of buildings obtained through non-linear static analysis. (3) Results: A seismic vulnerability map, critical peak ground accelerations for early damage and collapse states, and damage index maps for two return periods have been predicted using the developed damage curves. (4) Conclusions: The combination of the vulnerability index method with non-linear pushover analysis is an effective tool for assessing the damage of a building stock on a territorial scale.

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Evaluation of Seismic Vulnerability of Hospitals in the Tehran Metropolitan Area

Buildings ◽

10.3390/buildings11020054 ◽

2021 ◽

Vol 11 (2) ◽

pp. 54

Author(s):

Setareh Ghaychi Afrouz ◽

Alireza Farzampour ◽

Zahra Hejazi ◽

Masoud Mojarab

Keyword(s):

Metropolitan Area ◽

Structural Damage ◽

Seismic Vulnerability ◽

Fragility Curves ◽

Health Care Systems ◽

Ground Motions ◽

Active Faults ◽

The United States ◽

Damage And Failure ◽

Proactive Management

The Tehran metropolitan area is extremely vulnerable to earthquakes due to the location of its active faults and its dense population. Assessing the probable damage of a high magnitude earthquake on buildings and facilities relies on a precise structural survey, which has an empirical basis depending on historic ground motions. The probability of damage and failure in discrete limits based on different ground motions is estimated by fragility curves. Using the most matching fragility curves for buildings in Tehran, the vulnerability of the hospitals in the capital, as one of the most critical structures in crisis management of disasters, was investigated in this study. Subsequently, the existing fragility curves, developed for Tehran and the other seismic prone countries such as Japan and the United States, were compared considering the typology of Tehran’s hospitals. Finally, the possible damages for each hospital were calculated based on the most conservative fragility curve and the most pessimistic scenario, which were used to evaluate the seismic vulnerability of hospitals and health care systems for different damage states. After zoning the damage of therapeutic areas of Tehran, it was observed that at least 2% to 10% damage occurred in all hospitals of Tehran, and none of the healthcare centers would remain structurally undamaged after a strong earthquake with the moment magnitude of 7 or more. In addition, the healthcare buildings could be prone to significant structural damage, especially in southern parts, which necessitates proactive management plans for Tehran metropolitan area.

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Evaluation of floor acceleration demands from the 2017 Mexico City code seismic provisions using a continuous elastic model and records of instrumented buildings

Earthquake Spectra ◽

10.1177/8755293020974692 ◽

2020 ◽

Vol 36 (2_suppl) ◽

pp. 213-237

Author(s):

Miguel A Jaimes ◽

Adrián D García-Soto

Keyword(s):

Mexico City ◽

Seismic Design ◽

Soft Soil ◽

Response Spectra ◽

Elastic Model ◽

Ground Acceleration ◽

Nonstructural Components ◽

Floor Response Spectra ◽

Instrumented Buildings ◽

Floor Acceleration

This study presents an evaluation of floor acceleration demands for the design of rigid and flexible acceleration-sensitive nonstructural components in buildings, calculated using the most recent Mexico City seismic design provisions, released in 2017. This evaluation includes two approaches: (1) a simplified continuous elastic model and (2) using recordings from 10 instrumented buildings located in Mexico City. The study found that peak floor elastic acceleration demands imposed on rigid nonstructural components into buildings situated in Mexico City might reach values of 4.8 and 6.4 times the peak ground acceleration at rock and soft sites, respectively. The peak elastic acceleration demands imposed on flexible nonstructural components in all floors, estimated using floor response spectra, might be four times larger than the maximum acceleration of the floor at the point of support of the component for buildings located in rock and soft soil. Comparison of results from the two approaches with the current seismic design provisions revealed that the peak acceleration demands and floor response spectra computed with the current 2017 Mexico City seismic design provisions are, in general, adequate.

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