Seismic assessment of a R/C strategic existing building

Mehani, Youcef,Kibboua, Abderrahmane Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.26 No.6

Algeria is a country with a high seismic activity. During the last decade, many destructive earthquakes occurred, particularly in the northern part, causing enormous losses in human lives, buildings and equipments. In order to reduce this risk in the capital and avoid serious damages to the strategic existing buildings, the government decided to invest into seismic upgrade, strengthening and retrofitting of these buildings. In doing so, seismic vulnerability study of this category of buildings has been considered. Structural analysis is performed on the basis of site investigation (inspection of the building, collecting data, materials, 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 will provide insight to the vulnerability assessment and strengthening of the telecommunication centre, according to the new code RPA 99/version 2003. Both, static equivalent method and non linear dynamic analysis are performed in this study.

Assessment of seismic fragility curves for existing RC buildings in Algiers after the 2003 Boumerdes earthquake

Mehani, Youcef,Bechtoula, Hakim,Kibboua, Abderrahmane,Naili, Mounir Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.6

The main purpose of this paper is to develop seismic fragility curves for existing reinforced concrete, RC, buildings based on the post earthquake field survey and the seismic performance using capacity design. Existing RC buildings constitute approximately 65% of the total stock in Algiers. This type of buildings, RC, was widely used in the past and chosen as the structural type for the future construction program of more than 2 millions apartments all over Algeria. These buildings, suffered moderate to extensive damage after the 2003 Boumerdes earthquake, on May 21st. The determination of analytical seismic fragility curves for low-rise and mid-rise existing RC buildings was carried out based on the consistent and complete post earthquake survey after that event. The information on the damaged existing RC buildings was investigated and evaluated by experts. Thirty four (34) communes (districts) of fifty seven (57), the most populated and affected by earthquake damage were considered in this study. Utilizing the field observed damage data and the Japanese Seismic Index Methodology, based on the capacity design method. Seismic fragility curves were developed for those buildings with a large number data in order to get a statistically significant sample size. According to the construction period and the code design, four types of existing RC buildings were considered. Buildings designed with pre-code (very poor structural behavior before 1955), Buildings designed with low code (poor structural behavior, between 1955-1981), buildings designed with medium code (moderate structural behavior, between 1981-1999) and buildings designed with high code (good structural behavior, after 1999).

Assessment of seismic fragility curves for existing RC buildings in Algiers after the 2003 Boumerdes earthquake

Youcef Mehani,Hakim Bechtoula,Abderrahmane Kibboua,Mounir Naili 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.6

The main purpose of this paper is to develop seismic fragility curves for existing reinforced concrete, RC, buildings based on the post earthquake field survey and the seismic performance using capacity design. Existing RC buildings constitute approximately 65% of the total stock in Algiers. This type of buildings, RC, was widely used in the past and chosen as the structural type for the future construction program of more than 2 millions apartments all over Algeria. These buildings, suffered moderate to extensive damage after the 2003 Boumerdes earthquake, on May 21st. The determination of analytical seismic fragility curves for low-rise and mid-rise existing RC buildings was carried out based on the consistent and complete post earthquake survey after that event. The information on the damaged existing RC buildings was investigated and evaluated by experts. Thirty four (34) communes (districts) of fifty seven (57), the most populated and affected by earthquake damage were considered in this study. Utilizing the field observed damage data and the Japanese Seismic Index Methodology, based on the capacity design method. Seismic fragility curves were developed for those buildings with a large number data in order to get a statistically significant sample size. According to the construction period and the code design, four types of existing RC buildings were considered. Buildings designed with pre-code (very poor structural behavior before 1955), Buildings designed with low code (poor structural behavior, between 1955-1981), buildings designed with medium code (moderate structural behavior, between 1981-1999) and buildings designed with high code (good structural behavior, after 1999).

Damage Quantification of Steel Moment Resisting Frames using Ductility Parameters

Youcef Mehani,Hakim Bechtoula,Abderrahmane Kibboua,Mounir Naili 대한토목학회 2013 KSCE Journal of Civil Engineering Vol.17 No.6

The aim of a well designed construction in a seismic area is to avoid the collapse of buildings during major earthquakes. Up to now, this damage is expressed by the absence of plastic collapse, which takes into account the notion of the cinematic ductility in terms of demand and capacity. The ductility capacity must satisfy a certain level imposed by codes, without considering the duration of the strong motion and thus, number of plastic incursions and the fatigue phenomenon effects in the dissipative zones of the structure. Analytical investigation was carried out for six steel moment resisting frames with different dynamic parameters, subjected to six earthquakes with various characteristics. In total, thirty six cases were studied with a non linear dynamic analysis to assess the factors that affect the damage distribution of structures. Hereafter, the main results of this analysis are presented.

Simplified procedure for seismic demands assessment of structures

Benazouz Chikh,Youcef Mehani,Moussa Leblouba 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.3

Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity- Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (η). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.

Higher modes contribution for estimating the inelastic deformation ratios and seismic demands of structures

Abdelmounaim Mechaala,Chikh Benazouz,Hamma Zedira,Youcef Mehani,Samy Guezouli 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2

In order to estimate the seismic demand by using the nonlinear static procedure, different approximate methods have been developed. One of the most useful methods is called displacement coefficient method (DCM), which is based on some modification factors. One of these coefficients denoted 1 C , concerns the inelastic deformation ratio and usually depends on either the yield-strength reduction factor or the ductility factor. In general the evaluation of the inelastic deformation ratio is based on the response of single degree of freedom (SDOF) systems, where the response of the structure is mainly controlled by the fundamental mode, knowing that the inelastic deformation ratio will not capture the contribution of higher modes in the overall structural response. A developed theoretical approach with the aim of estimating the inelastic deformation ratio for structures, considering contribution of higher modes of vibration, is introduced. In this assessment, the normalized yield strength coefficient (η) and the post-to-preyield stiffness ratio (α) are key factors. The results are compared to the uncoupled modal response history analysis (UMRHA) procedure and some existing formulations for a nine story building subjected to the El Centro 1940 ground motion. It appears that the new theoretical approach leads to enough accurate estimation of the inelastic deformation ratio compared to the UMRHA one.

Modal analysis and ambient vibration measurements on Mila-Algeria cable stayed bridge

Kibboua, Abderrahmane,Farsi, Mohamed Naboussi,Chatelain, Jean-Luc,Guillier, Bertrand,Bechtoula, Hakim,Mehani, Youcef Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.2

The seismic response analysis of an existing bridge needs a mathematical model that can be calibrated with measured dynamic characteristics. These characteristics are the periods and the associated mode shapes of vibration and the modal damping coefficients. This paper deals with the measurements and the interpretation of the results of ambient vibration tests done on a newly erected cable stayed bridge across the Oued Dib River at Mila city in Algeria. The signal analysis of ambient vibration records will permit to determine the dynamic characteristics of the bridge. On the other hand, a 3-D model of the bridge is developed in order to assess the frequencies and the associated modes of vibration. This information will be necessary in the planning of the test on the site (locations of the sensors, frequencies to be measured and the associated mode shapes of vibration). The frequencies predicted by the finite element model are compared with those measured during full-scale ambient vibration measurements of the bridge. In the same way, the modal damping coefficients obtained by the random decrement method are compared to those of similar bridges.

Modal analysis and ambient vibration measurements on Mila-Algeria cable stayed bridge

Abderrahmane Kibboua,Mohamed Naboussi Farsi,Jean-Luc Chatelain,Bertrand Guillier,Hakim Bechtoula,Youcef Mehani 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.2

The seismic response analysis of an existing bridge needs a mathematical model that can be calibrated with measured dynamic characteristics. These characteristics are the periods and the associated mode shapes of vibration and the modal damping coefficients. This paper deals with the measurements and the interpretation of the results of ambient vibration tests done on a newly erected cable stayed bridge across the Oued Dib River at Mila city in Algeria. The signal analysis of ambient vibration records will permit to determine the dynamic characteristics of the bridge. On the other hand, a 3-D model of the bridge is developed in order to assess the frequencies and the associated modes of vibration. This information will be necessary in the planning of the test on the site (locations of the sensors, frequencies to be measured and the associated mode shapes of vibration). The frequencies predicted by the finite element model are compared with those measured during full-scale ambient vibration measurements of the bridge. In the same way, the modal damping coefficients obtained by the random decrement method are compared to those of similar bridges.