Urban vulnerability assessment: Advances from the strategic planning outlook

The seismic damage of various structures has a significant impact on human production and life, to understand the seismic performance of typical structures and analyze their vulnerability characteristics, and achieve the objective of improving the seismic capacity of structures, and data from 18,480 empirical seismic damage samples from 33 cities and towns for the May 12, 2008, Wenchuan earthquake (China) are summarized and statistically analyzed. The reconnaissance results of the empirical seismic damage show that the structures of masonry structure, multistory reinforced concrete structure, bottom frame-seismic wall masonry and brick-timber and brick-masonry building have the characteristics of widespread application, a myriad of samples and typical failure, sample data for the categories of abovementioned structures are analyzed by statistics and numerical methods, and the empirical seismic damage probability matrix models are established. A nonlinear regression model for calculating the vulnerability grade and the number of samples damaged is proposed. Combined with the empirical sample data, the vulnerability regression function and the curve model of multiple structural types in the VI–X region are established. A mean vulnerability seismic index probability matrix model considering the empirical seismic vulnerability probability in the multiseismic region is proposed. The model is validated by using the above sample database, and the mean damage index matrix in the multiseismic zone is obtained. The analysis results can effectively evaluate the vulnerability characteristics of typical structures in multiseismic regions and provide a necessary reference for a view to a future revision of the building codes and seismic intensity scales currently in force.

Analysis of the probability matrix model for the seismic damage vulnerability of empirical structures

The experimental and shear strength analytical investigations carried out on seismic-damaged steel reinforced concrete (SRC) columns strengthened with enveloped steel jacket subjected to cyclic loading are presented in this paper. Four 1/2-scale SRC columns were designed and manufactured and the postearthquake damage, enveloped steel jacket-confined, and destructive tests were carried out under lateral cyclic loading. The effects of postearthquake damage degree and enveloped steel jacket-confined on shear capacity and ductility capacity were all well examined. Test results indicate that the ductility of seismic-damaged SRC columns strengthened with enveloped steel jacket increases with the reduction of the postearthquake damage degree. The results indicate that the calculation formula of shear bearing capacity of SRC columns is feasible. Based on GB50010-2010, ACI318-08, and CSA-04, three different shear models were established, and the calculated values of shear capacity are quite different, and the analysis of the shear strength of RC in the strengthened seismic-damaged SRC column cannot be ignored. The formula is verified, and the calculated results are consistent well with the experimental results.

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Experimental and Theoretical Research on Shear Strength of Seismic-Damaged SRC Frame Columns Strengthened with Enveloped Steel Jackets

The latest Italian seismic events have highlighted a high discrepancy between the potential destructiveness of an earthquake and the consequent economic losses due to damage to buildings. The main reason for this mismatch is the high number of vulnerable residential buildings or the low-to-medium vulnerability of buildings that are reaching the ends of their service lives. Awareness of the economic impact of seismic vulnerability should be a matter of primary interest for public administrations, private and insurance companies, banks, owners, and professionals, despite operating at different territorial levels and with different objectives. Quantification of the expected monetary consequence of seismic vulnerability, in terms of the probable cost of repairing earthquake damage, plays a key role in defining new and more effective seismic risk mitigation strategies. Retrofitting strategies based on intervention priority defined only according to the structural seismic risk level of buildings are incorrect. These strategies neglect several important issues, such as the financial losses caused by building damage. A new procedure for estimating the expected seismic direct economic losses resulting from building damage (repair/replacement measures) is proposed and applied. The fundamental roles of analytical fragility curves and cost ratio functions in the new procedure are highlighted.

An Optimized Procedure to Estimate the Economic Seismic Losses of Existing Reinforced Concrete Buildings due to Seismic Damage

Seismic vulnerability assessment of RC buildings with setback irregularity

The main objective of this present work is to estimate the seismic fragility of typical existing buildings in the north part of Algeria, in which we evaluate the performance, the seismic vulnerability and the damage of reinforced concrete frame structures and URM masonry buildings, existing in dominant way in the city of Algiers (Algeria). An analytical procedure for the derivation of fragility curves is proposed. The capacity spectrum method and seismic damage potential for the city, starting from capacity and fragility curves, are then discussed. Different tools regarding the determination of capacity curves of different existing structural systems by using a non-linear structural analysis are implemented and explained. Four damage states are defined for both structural systems. The earthquake action is expressed in terms of spectral values and the seismic quality of the buildings; the probabilities of the damage states are obtained considering a lognormal probability distribution. An ADRS format has been used for the studied area where a significant damage is obtained for mid-rise and high-rise masonry buildings.

Seismic Fragility Evaluation of Existing RC Frame and URM Buildings in Algeria

This study evaluates the seismic vulnerability of an existing URM building which is currently used as a city hall of one of the biggest cities in the east part of Algeria called Constantine. In order to avoid serious damages, in the future, a seismic vulnerability and damage investigation of this kind of buildings are must. A seismic vulnerability study has been considered. Structural analysis is performed based on the site investigation (including inspection of the building and materials characteristics). An analytical procedure for the derivation of fragility curves is proposed. Different tools regarding the determination of capacity curves of the structural system by using a nonlinear analysis are implemented and four damage states are defined. The earthquake action is expressed in terms of spectral values; the probabilities of the damage states are obtained considering a lognormal probability distribution.

Seismic Vulnerability and Damage Assessment of an Existing URM Building

The estimation of losses resulting from an earthquake requires that for each building class, the relationship between the intensity of ground shaking and damage degree must be known or developed Potential earthquake damage to structures, human beings and personal property have been the scope of numerous studies Different approaches have been employed so far to estimate earthquake casualties and damage This paper describe the basic concept for development of analytical vulnerability functions based essentially on so called damage model which was performed from probabilistic studies on seismic capacity of existing buildings in the city of Algiers (Algeria) Regarding the developed model for assessing the seismic damage, vulnerability functions of specific losses (potential losses for a specific urban area in terms of meter square area of building slabs which may involve causalities) were developed in order to predict the expected seismic risk for a given ground motion scenario

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Damage potential and vulnerability functions of strategic buildings in the city of Algiers

The latest earthquake disasters have highlighted, once again, poor functioning of the existing masonry structures, and the need to intervene all these structures which have been designed with old regulatory criteria, inadequate or those that have been built before the emergence of design codes. The significant progress made in new criteria of earthquake resistant design, should be extended to all the existing structures, it is therefore essential to identify the degree of seismic performance. Unreinforced masonry (URM) buildings represent a significant portion of the residential structures in Algeria, accounting for more than 60% of existing buildings. In addition to significant population, the brittle nature of URM buildings further supports a thorough consideration of seismic response given the susceptibility to severe failure modes. Currently, there is a pressing need for analytically based fragility curves for URM buildings. In order to improve the estimation of damage state probabilities through the development of simulation-based masonry fragilities, an extensive literature survey is conducted on pushover analysis of URM structures. Structural response is evaluated using an advanced capacity spectrum method. Capacity, demand, and response are thus derived analytically and response data is used to generate an improved and uniform set of fragility curves for use in risk assessment. Seismic fragility curves are expressed in multiple forms for wide range of use in loss-assessment applications. Results are discussed and compared with other relationships developed in the literature.

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Analytically Derived Fragility Curves and Damage Assessment of Masonrybuildings

During the last decades, many destructive earthquakes occurred in Algeria, particularly in the northern part of the country (Chlef (1980), Constantine (1985), Tipaza (1989), Mascara (1994), Ain-Benian (1996), Ain Temouchent (1999), Beni Ourtilane (2000), and recently Boumerdes (2003), causing enormous losses in human lives, buildings and equipments. In order to reduce this risk and avoid serious damages to the strategic existing buildings, the authorities of the country, aware of this risk and in order to have the necessary elements that let them to know and estimate the potential losses in advance, with an acceptable error, and to take the necessary countermeasures, decided to invest into seismic upgrade, strengthening and retrofitting of those buildings. To do so, seismic vulnerability study of this category of buildings has been considered. Structural analysis is performed based on the site investigation (inspection of the building, collecting data, materials characteristics, general conditions of the building, etc.), and existing drawings (architectural plans, structural design, etc.). The aim of these seismic vulnerability studies is to develop guidelines and a methodology for rehabilitation of existing buildings.
This paper presents the methodology, based on non linear and seismic analysis of existing buildings, followed in this study and summarizes the vulnerability assessment and strengthening of one of the strategic buildings according to the new Algerian code RPA 99/version 2003. As a direct application of this methodology, both, static equivalent method and non linear dynamic analysis, of composite concrete masonry existing building in the city of "CONSTANTINE", located in the east side of ALGERIA, are presented in this paper.

Mustapha Remki

Papers

Seismic Fragility Evaluation of Existing RC Frame and URM Buildings in Algeria

Seismic Vulnerability and Damage Assessment of an Existing URM Building

Damage potential and vulnerability functions of strategic buildings in the city of Algiers

Analytically Derived Fragility Curves and Damage Assessment of Masonrybuildings

Seismic vulnerability assessment of composite reinforced concrete-masonry building