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Abstract
Existing reinforced concrete frame buildings designed for vertical loads could only suffer severe damage during earthquakes. In recent years, many research activities were undertaken to develop a reliable and practical analysis procedure to identify the safety level of existing structures. The Incremental Dynamic Analysis (IDA) is considered to be one of the most accurate methods to estimate the seismic demand and capacity of structures. However, the executions of many nonlinear response history analyses (NL_RHA) are required to describe the entire range of structural response. The research discussed in this paper deals with the proposal of an efficient Incremental Modal Pushover Analysis (IMPA) to obtain capacity curves by replacing the nonlinear response history analysis of the IDA procedure with Modal Pushover Analysis (MPA). Firstly, In this work, the MPA is examined and extended to three-dimensional asymmetric structures and then it is incorporated into the proposed procedure (IMPA) to estimate the structure‟s seismic response and capacity for given seismic actions. This new procedure, which accounts for higher mode effects, does not require the execution of complex NL-RHA, but only a series of nonlinear static analysis. Finally, the extended MPA and IMPA were applied to an existing irregular framed building.

Key Words
modal pushover analysis; existing building; capacity curve, incremental dynamic analysis

Address
A.V. Bergami, A. Forte and D. Lavorato : Department of Architecture, University of Roma Tre, Rome, Italy C. Nuti : Department of Architecture, University of Roma Tre, Rome, Italy /College of Civil Engineering, University of Fuzhou, Fuzhou, China

Abstract
A large number of isolation systems are designed without considering the non-uniform friction distribution in space. In order to analyze the effects of non-uniform friction distribution on the structural response of isolation system, this paper presented a simplified rolling-damper-spring isolation system and analyzed the structural responses under earthquakes. The numerical results indicate that the calculation errors related to the peak values of structural acceleration, relative displacement and residual displacement are sequentially growing because of the ignorance of non-uniform friction distribution. However, the influence rule may be weakened by the spring and damper actions, and the unreasonable spring constant may lead to the sympathetic vibration of isolation system. In the case when the friction variability is large and the damper action is little, the nonuniform friction distribution should be taken into consideration during the calculation process of the peak values of structural acceleration and relative displacement. The non-uniform friction distribution should be taken into full consideration regardless of friction variability degree in calculating the residual displacement of isolation system.

Key Words
seismic isolation; friction variability; rolling friction; spring; viscous damper

Address
Biao Wei, Peng Wang, Xuhui He and Zhen Zhang : School of Civil Engineering, Central South University, 22 Shaoshan South Road, Changsha, China /National Engineering Laboratory for High Speed Railway Construction, 22 Shaoshan South Road, Changsha, China Liang Chen : School of Civil Engineering, Hefei University of Technology, 193 Dunxi Road, Hefei, China

Abstract
Seismic base isolation has been accepted as one of the most popular design procedures to protect important structures against earthquakes. However, due to lack of information and experimental data the application of base isolation is quite limited to nuclear power plant (NPP) industry. Moreover, the effects of inelastic behavior of soil beneath base-isolated NPP have raised questions to the effectiveness of isolation device. This study applies the wavelet analysis to investigate the effects of soil-structure interaction (SSI) on the seismic response of a base-isolated NPP structure. To evaluate the SSI effects, the NPP structure is modelled as a lumped mass stick model and combined with a soil model using the concept of cone models. The lead rubber bearing (LRB) base isolator is used to adopt the base isolation system. The shear wave velocity of soil is varied to reflect the real rock site conditions of structure. The comparison between seismic performance of isolated structure and non-isolated structure has drawn. The results show that the wavelet analysis proves to be an efficient tool to evaluate the SSI effects on the seismic response of base-isolated structure and the seismic performance of base-isolated NPP is not sensitive to the effects in this case.

Key Words
nuclear power plant; base isolation; seismic behavior; soil-structure interaction; wavelet analysis

Address
Shafayat Bin Ali : Institute of Earthquake Engineering Research (IEER), Chittagong University of Engineering & Technology, Chittagong-4349, Bangladesh Dookie Kim : Department of Civil and Environmental Engineering, Kunsan National University, South Korea

Abstract
The earthquake input is required when the soil-structure interaction (SSI) analysis is performed by the direct finite element method. In this paper, the earthquake is considered as the obliquely incident plane body wave arising from the truncated linearly elastic layered half space. An earthquake input method is developed for the time-domain three-dimensional SSI analysis. It consists of a new site response analysis method for free field and the viscous-spring artificial boundary condition for scattered field. The proposed earthquake input method can be implemented in the process of building finite element model of commercial software. It can result in the highly accurate solution by using a relatively small SSI model. The initial condition is considered for the nonlinear SSI analysis. The Daikai subway station is analyzed as an example. The effectiveness of the proposed earthquake input method is verified. The effect of the obliquely incident earthquake is studied.

Key Words
seismic soil-structure interaction; layered half space; oblique incidence; artificial boundary condition; site response analysis

Address
Mi Zhao, Zhidong Gao, Litao Wang, Xiuli Du, Jingqi Huang and Yang Li : Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China /Beijing Collaborative Innovation Center for Metropolitan Transportation, Beijing University of Technology, Beijing 100124, China

Abstract
In this paper, dynamic response of the horizontal concrete beam subjected to seismic ground excitation is investigated. The structure is reinforced by Fe2O3 nanoparticles which have the magnetic properties. The hyperbolic shear deformation beam theory (HSDBT) is used for mathematical modeling of the structure. Based on the Mori-Tanaka model, the effective material properties of concrete beam is calculated considering the agglomeration of Fe2O3 nanoparticles. Applying energy method and Hamilton\'s principle, the motion equations are derived. Harmonic differential quadrature method (HDQM) along with Newmark method is utilized for numerical solution of the motion equations. The effects of different parameters such as volume fraction and agglomeration of Fe2O3 nanoparticles, magnetic field, boundary conditions and geometrical parameters of concrete beam are studied on the dynamic response of the structure. In order to validation of this work, an exact solution is used for comparing the numerical and analytical results. The results indicated that applying magnetic field decreases the of the structure up to 54 percent. In addition, increase too much the magnetic field (Hx>5e8 A/m) does not considerable effect on the reduction of the maximum dynamic displacement.

Key Words
dynamic response; Fe2O3 nanoparticles; seismic ground excitation; HDQM; magnetic field

Address
Hossein Mohammadian, Reza Kolahchi and Mahmood Rabani Bidgoli : Department of Civil Engineering, Jasb Branch, Islamic Azad University, Jasb, Iran

Abstract
This paper improves seismic fragility of a typical steel-concrete composite bridge with the deck-to-pier connection joint configuration at the concrete crossbeam (CCB). Based on the quasi-static test on a typical steel-concrete composite bridge model under the SEQBRI project, the damage states for both of the critical components, the CCB and the pier, are identified. The finite element model is developed, and calibrated using the experimental data to model the damage states of the CCB and the bridge pier as observed from the experiment of the test specimen. Then the component fragility curves for both of the CCB and the pier are derived and combined to develop the system fragility curves of the bridge. The uncertainty associated with the mean system fragility has been discussed and quantified. The study reveals that the CCB is more vulnerable than the pier for certain damage states and the typical steel-concrete composite bridge with CCB exhibits desirable seismic performance.

Key Words
seismic fragility; steel-concrete composite bridge; quasi-static test; concrete crossbeam; damage state

Address
Yang Liu and Da-Gang Lu : School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, P.R. China Fabrizio Paolacci : Department of Engineering, Roma Tre University, Rome, Italy

Abstract
Seismic retrofitting of existing buildings and design of earth-quake resistant buildings are important issues associated with earthquake-prone zones. Use of metallic-yielding dampers as an energy dissipation system is an acceptable method for controlling damages in structures and improving their seismic performance. In this study, the optimal distribution of dampers for reducing the seismic response of steel frames with multi-degrees freedom is presented utilizing the uniform distribution of deformations. This has been done in a way that, the final configuration of dampers in the frames lead to minimum weight while satisfying the performance criteria. It is shown that such a structure has an optimum seismic performance, in which the maximum structure capacity is used. Then the genetic algorithm which is an evolutionary optimization method is used for optimal arrangement of the steel dampers in the structure. In continuation for specifying the optimal accurate response, the local search algorithm based on the gradient concept has been selected. In this research the introduced optimization methods are used for optimal retrofitting in the moment-resisting frame with inelastic behavior and initial weakness in design. Ultimately the optimal configuration of dampers over the height of building specified and by comparing the results of the uniform deformation method with those of the genetic algorithm, the validity of the uniform deformation method in terms of accuracy, Time Speed Optimization and the simplicity of the theory have been proven.

Key Words
metallic-yielding damper; optimal outline configuration of dampers; optimal retrofitting; uniform deformation method; Genetic Algorithm

Address
Reza Karami Mohammadi, Maryam Mirjalaly, Masoud Mirtaheri: Department of Civil Engineering, K.N. Toosi University of Technology, 470 Mirdamad Ave.West, Tehran, Iran Meissam Nazeryan: Department of Civil Engineering, Sharif University of Technology, Azadi Ave., Tehran, Iran

Abstract
Three-dimensional panels are one of the modern construction systems which can be placed in the category of industrial buildings. There have always been a lot of studies and efforts to identify the behavior of these panels and improve their capacity due to their earthquake resistance and high speed of performance. This study will provide a comparative evaluation of behavior of updated three-dimensional panel\'s structural components under lateral load in both independent and dependent modes. In fact, this study tries to simultaneously evaluate strengthening effect of three-dimensional panels and the effects of system state (independent, L-shaped and BOX shaped Walls) with reinforcement armatures with different angles on the three-dimensional panels. Overall, six independent wall model, L-shaped, roofed L-shaped, BOX-shaped walls with symmetric loading, BOX -shaped wall with asymmetrical loading and roofed BOX-shaped wall were built. Then the models are strengthened without strengthened reinforcement and with strengthened reinforcements with an angle of 30, 45 and 60 degrees. The applied lateral loading, is exerted by changing the location on the end wall. In BOX-shaped wall, in symmetric and asymmetric loading, the load bearing capacity will be increased about 200 and 50% respectively. Now, if strengthened, the load bearing capacity in symmetric and asymmetric loading will be increased 3.5 and 2 times respectively. The effective angle of placement of strengthened reinforcement in the independent wall is 45 and 60 degrees. But in BOX-shaped and L-shaped walls, the use of strengthened reinforcement 45 degrees is recommended.

Key Words
three-dimensional panels; independent mode and system; improvement of lateral load capacity; strengthening panel

Address
Omid Rezaifar, Majid Ghohaki: Department of Civil Engineering, Semnan University, Across from Sokan Park, Semnan, Iran Hamun Adeli Nik: Faculty of Civil Engineering, Semnan University, 18, 28 Street, Gisha, Tehran, Iran

Abstract
Prefabricated structures are constructed by bolted connections of separated members. The design and analysis of these structures are generally performed by defining fully hinges for the connection of separated members at the joint of junction. In practice, these connections are not fully hinged. Therefore, the assumption of semi-rigid connections (restrained or partially fixity) instead of fully hinge connections is a more realistic approach for bolted connections used in the prefabricated elements. The aim of this study is to investigate the effects of semi-rigid connections on seismic performance of prefabricated structures. Nonlinear static analysis (pushover analysis) of a selected RC prefabricated structure is performed with SAP2000 structural analysis program by considering various partially fixity percentages for bolted connections. The target values of roof displacements obtained from the analyses according to ATC-40, FEMA-356, FEMA-440, and TEC-2007 codes are compared each other. The numerical results are given in tables and figures comparatively and discussed. The results show that the effects of semi-rigid connections should be considered in design and analysis of the prefabricated structures.

Key Words
prefabricated structures; semi-rigid connections; nonlinear static pushover analysis

Address
Mehmet Akkose: Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey Fezayil Sunca and Alperen Turkay: Department of Civil Engineering, Cumhuriyet University, Sivas, Turkey

Abstract
Base-isolated nuclear power plant (BI-NPP) structures are founded on expanded basemat as a flexible floating nuclear island, are still lacking the recommendation of the consideration of incoherent motion effect. The effect of incoherent earthquake motion on the seismic response of BI-NPP structure has been investigated herein. The incoherency of the ground motions is applied by using an isotropic frequency-dependent spatial correlation function to perform the conditional simulation of the reference design spectrum compatible ground motion in time domain. Time history analysis of two structural models with 486 and 5 equivalent lead plug rubber bearing (LRB) base-isolators have been done under uniform excitation and multiple point excitation. two different cases have been considered: 1) Incoherent motion generated for soft soil and 2) Incoherent motion generated for hard rock soil. The results show that the incoherent motions reduce acceleration and the lateral displacement responses and the reduction is noticeable at soft soil site and higher frequencies.

Key Words
incoherent earthquake motion; base-isolated nuclear power plant; seismic response

Address
Kaiser Ahmed, Dookie Kim: Department of Civil Engineering, Kunsan National University, Gunsan-si, 54150, Republic of Korea Sang H. Lee: Power Engineering Research Institute, KEPCO E&C, Gimcheon, Republic of Korea

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