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Abstract
This paper presents a study on a non-seismically designed reinforced concrete (RC) frame structure. The structure was a existing three-story office building constructed according to the 1990s practice in Vietnam. The 1/3 scaled down versions of structure was tested on a shake table to investigate the seismic performance of this type of construction. It was found that the inter-story drift and the overall behavior of structure meet the requirements of the actual seismic design codes. Then, nonlinear time history analyses are carried out using the fiber beam- column elements. The comparison between the experimental and simulation results shows the performance of the time history analysis models.

Key Words
seismic; reinforced concrete; non seismically designed; fiber beam; nonlinear; frame structure

Address
Xuan-Huy Nguyen and Huy Cuong Nguyen: Department of Civil Engineering, University of Transport and Communications, Vietnam Xuan-Huy Nguyen and Huy Cuong Nguyen: Research and Application Center for Technology in Civil Engineering, University of Transport and Communications, Vietnam

Abstract
A virtual parameter is introduced into the formulation of the previously published integration method to improve its stability properties. It seems that the numerical properties of this integration method are almost unaffected by this parameter except for the stability property. As a result, it can have second order accuracy, explicit formulation and controllable numerical dissipation in addition to the enhanced stability property. In fact, it can have unconditional stability for the system with the instantaneous degree of nonlinearity less than or equal to the specified value of the virtual parameter for the modes of interest for each time step.

Key Words
unconditional stability; conditional stability; nonlinear dynamic analysis; virtual parameter; structure-dependent integration method

Address
Shuenn-Yih Chang: Department of Civil Engineering National Taipei University of Technology NTUT Box 2653, Taipei 106, Taiwan, Republic of China

Abstract
This paper presents the results of cyclic loading tests on concrete beams reinforced with various reinforcement, including ordinary steel bars, CFRP bars and CFRP prestressed concrete prisms(PCP). The main variable in the test program was the level of prestress and the cross section of PCP. The seismic performance indexes including hysteretic loops, skeleton curve, ductility, energy dissipation capacity and stiffness degradation were analyzed. The results show that the CFRP prestressed concrete prisms as flexural reinforcement of concrete beams has good seismic performance. And the ductility and the energy dissipation capacity were good, the hysteresis loops were full and had large area.

Key Words
CFRP; prism; cyclic loading; beam; seismic performance

Address
Jiongfeng Liang: State Key Laboratory Breeding Base of Nuclear Resources and Environment, Fundamental Science on Radioactive Geology and Exploration Technology Laboratory, Nanchang, P.R. China Jiongfeng Liang, Jianbao Wang, Pinghua Yi: Faculty of Civil&Architecture Engineering, East China Institute of Technology, Nanchang, P.R. China Deng Yu: College of Civil and Architecture Engineering, Guangxi University of Science and Technology, Liuzhou, P.R. China

Abstract
The 2012 Emilia (Italy) earthquakes struck a highly industrialized area including several thousands of industrial prefabricated buildings. Due to the lack of specific design and detailing for earthquake resistance, precast reinforced concrete (RC) buildings suffered from severe damages and even partial or total collapses in many cases. The present study reports a data inventory of damages from field survey on prefabricated buildings. The damage database concerns more than 1400 buildings (about 30% of the total precast building stock in the struck region). Making use of the available shakemaps of the two mainshocks, damage distributions were related with distance from the nearest epicentre and corresponding Pseudo-Spectral Acceleration for a period of 1 second (PSA at 1 s) or Peak Ground Acceleration (PGA). It was found that about 90% of the severely damaged to collapsed buildings included into the database stay within 16 km from the epicentre and experienced a PSA larger than 0.12 g. Moreover, 90% of slightly to moderately damaged buildings are located at less than 25 km from the epicentre and were affected by a PSA larger than 0.06 g. Nevertheless, the undamaged buildings examined are almost uniformly distributed over the struck region and 10% of them suffered a PSA not lower than 0.19g. The damage distributions in terms of the maximum experienced PGA show a sudden increase for PGA

Key Words
precast RC buildings; damages; Emilia earthquake; seismic retrofitting; peak ground acceleration; pseudo-spectral acceleration

Address
Fabio Minghini, Nerio Tullini: Engineering Department - ENDIF, University of Ferrara, Via G. Saragat 1, 44122, Ferrara, Italy Elena Ongaretto, Veronica Ligabue, Marco Savoia: Department of Civil, Chemical, Environmental, and Materials Engineering - DICAM, University of Bologna, Viale Risorgimento 2, 40136, Bologna, Italy

Abstract
The main objective of this paper is the robust multi-objective optimization design of semi-active tuned mass damper (STMD) system using genetic algorithms and fuzzy logic. For optimal design of this system, it is required that the uncertainties which may exist in the system be taken into account. This consideration is performed through the robust design optimization (RDO) procedure. To evaluate the optimal values of the design parameters, three non-commensurable objective functions namely: normalized values of the maximum displacement, velocity, and acceleration of each story level are considered to minimize simultaneously. For this purpose, a fast and elitist non-dominated sorting genetic algorithm (NSGA-II) approach is used to find a set of Pareto-optimal solutions. The torsional effects due to irregularities of the building and/or unsymmetrical placements of the dampers are taken into account through the 3-D modeling of the building. Finally, the comparison of the results shows that the probabilistic robust STMD system is capable of providing a reduction of about 52%, 42.5%, and 37.24% on the maximum displacement, velocity, and acceleration of the building top story, respectively.

Key Words
semi-active control system; multi-objective optimization; robust design; genetic algorithm; fuzzy logic controller; earthquake excitation

Address
Saeid Pourzeynali, Meysam Yousefisefat: Department of Civil Engineering, Faculty of Engineering, University of Guilan, Rasht, I. R. Iran Shide Salimi, Houshyar Eimani Kalesar: Department of Civil Engineering, Faculty of Engineering, University of Mohaghegh-Ardebili, Ardebil, I. R. Iran

Abstract
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.

Key Words
vulnerability; masonry; strategic building; capacity design; non linear dynamic analysis; strengthening

Address
Mustapha Remki, Fouad kehila, Hakim Bechtoula: Department of Civil Engineering, National Earthquake Engineering Research Center, CGS, Rue Kaddour Rahim, BP 252 Hussein Dey, Algiers, Algeria Abdelkrim Bourzam: Faculty of Civil Engineering, University of Sce & Technology USTHB, Algiers, Algeria

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Abstract
The main purpose of this paper is to determine the dynamic characteristics and the structural stability of the two approach viaducts of the Bosphorus Suspension Bridge under the expected stresses that would be caused during earthquake conditions. The Ortakoy and the Beylerbeyi approach viaducts constitute the side spans of the bridge at two locations. The bridge´s main span over the Bosphorus is suspended, whereas they are supported at the base at either end. For the numerical investigation of the viaducts, 3-D computational structural finite element-FE models were developed. Their natural frequencies and the corresponding mode shapes were obtained, analyzed, presented and compared. The performances of the viaducts, under earthquake conditions, were studied considering the P-Delta effects implementing the push-over (POA) and the non-linear time-history analyses (NTHA). For the NTHA, three earthquake ground motions were generated depending on the location of the bridge. Seismic performances of the viaducts were determined in accordance with the requirements of the Turkish Seismic Code for the Earthquake Design of Railways Bridges (TSC-R/2008) and those of Caltrans (CALTRANS-2001) given for Seismic Design of Steel Bridges, separately. Furthermore, the investigation was extended for evaluating the possible need for retrofitting in the future. After the analysis of the resultant data, a retrofit recommendation for the viaducts was presented.

Key Words
suspension bridge; approach viaducts; seismic performance; non-linear time-history; pushover; seismic retrofit

Address
Selcuk Bas: Department of Civil Engineering, Engineering Faculty, Bartin University, 74100 Bartin, Turkey Selcuk Bas: Graduate School of Science, Engineering and Technology, Istanbul Technical University, 34496 Istanbul, Turkey Nurdan Memisoglu Apaydin: Director, Department of Structures, General Directorate of Turkish State Highways, 06100 Ankara, Turkey Zekai Celep: Department of Structural and Earthquake Engineering, Faculty of Civil Engineering, Istanbul Technical University, 34469 Istanbul, Turkey

Abstract
The aim of this study is to investigate the effect of vertical ground motion (VGM) on seismic behavior of reinforced concrete (RC) regular frame with construction joints, and determine more proper modeling method for cast-in-situ RC frame. The four-story RC frames in the regions of 7, 8 and 9 earthquake intensity were analyzed with nonlinear dynamic time-history method. Two different methods of ground motion input, horizontal ground motion (HGM) input only, VGM and HGM input simultaneously were performed. Seismic responses in terms of the maximum vertex displacement, the maximum inter-story drift distribution and the plastic hinge distribution were analyzed. The results show that VGM might increase or decrease the horizontal maximum vertex displacement depending on the value of axial load ratio of column. And it will increase the maximum inter-story drift and change its distribution. Finally, proper modeling method is proposed according to the distribution of plastic hinges, which is in well agreement with the actual earthquake damage.

Key Words
seismic behavior; vertical ground motion (VGM); RC frame; construction joint; nonlinear time-history analysis; numerical model

Address
Jing Yu and Xiaojun Liu: College of Civil Engineering, Xi

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