Techno Press
Tp_Editing System.E (TES.E)
Login Search


eas
 
CONTENTS
Volume 13, Number 4, October 2017
 

Abstract
In the present study a capacity spectrum method based on constant ductility inelastic spectra to estimate the seismic performance of structures equipped with elastic viscous dampers is presented. As the definition of the structures\' effective damping, due to the damping system, is necessary, an alternative method to specify the effective damping ratio eff is presented. Moreover, damping reduction factors (B) are introduced to generate high damping elastic demand spectra. Given the elastic spectra for damping ratio eff, the performance point of the structure can be obtained by relationships that relate the strength demand reduction factor (R) with the ductility demand factor (u). As such expressions that link the above quantities, known as R – u – T relationships, for different damping levels are presented. Moreover, corrective factors (Bv) for the pseudo-velocity spectra calculation are reported for different levels of damping and ductility in order to calculate with accuracy the values of the viscous dampers velocities. Finally, to evaluate the results of the proposed method, the whole process is applied to a four-storey reinforced concrete frame structure and to a six-storey steel structure, both equipped with elastic viscous dampers.

Key Words
simplified analysis method; capacity spectrum method; passive energy dissipation systems; high damping spectra; inelastic spectra; linear viscous damping

Address
Kosmas E. Bantilas, Ioannis E. Kavvadias and Lazaros K. Vasiliadis: Department of Civil Engineering, Democritus University of Thrace, Campus of Kimmeria, 67100, Xanthi, Greece

Abstract
The present study considers a multi-span continuous bridge, isolated by lead rubber bearing (LRB). Dynamic soil-structure interaction (SSI) is modelled with the help of a simplified, sway-rocking model for different types of soil. It is well understood from the literature that SSI influences the structural responses and the isolator performance. However, the above-mentioned effect of SSI also depends on the earthquake ground motion properties. It is very important to understand how the interaction between soil and structure varies with the earthquake ground motion characteristics but, as far as the knowledge of the authors go, no study has been carried out to investigate this effect. Therefore, the objectives of the present study are to investigate the influence of earthquake ground motion characteristics on: (a) the responses of a multi span bridge (isolated and non-isolated), (b) the performance of the isolator and, most importantly, (c) the soil-structure interaction. Statistical analyses are conducted by considering 14 earthquakes which are selected in such a way that they can be categorized into three frequency content groups according to their peak ground acceleration to peak ground velocity (PGA/PGV) ratio. Lumped mass model of the bridge is developed and time history analyses are carried out by solving the governing equations of motion in the state space form. The performance of the isolator is studied by comparing the responses of the bridge with those of the corresponding uncontrolled bridge (i.e., non-isolated bridge). On studying the effect of earthquake motions, it is observed that the earthquake ground motion characteristics affect the interaction between soil and structure in such a way that the responses decrease with increase in frequency content of the earthquake for all the types of soil considered. The reverse phenomenon is observed in case of the isolator performance where the control efficiencies increase with frequency content of earthquake.

Key Words
bridge; elastomeric bearings; dynamic soil structure interaction; earthquake; frequency content

Address
B Neethu, Diptesh Das and Siddharth Garia: Department of Civil Engineering, National Institute of Technology Durgapur, West Bengal, India

Abstract
Seismic risk management has two main technical aspects: to recommend the construction of high-performance buildings and other structures using earthquake-resistant designs or evaluate existing ones, and to prepare emergency plans using realistic seismic scenarios. An overview of seismic risk assessment methodologies in Croatia is provided with details regarding the components of the assessment procedures: hazard, vulnerability and exposure. For Croatia, hazard is presented with two maps and it is expressed in terms of the peak horizontal ground acceleration during an earthquake, with the return period of 95 or 475 years. A standard building typology catalogue for Croatia has not been prepared yet, but a database for the fourth largest city in Croatia is currently in its initial stage. Two methods for earthquake vulnerability assessment are applied and compared. The first is a relatively simple and fast analysis of potential seismic vulnerability proposed by Croatian researchers using damage index (DI) as a numerical value indicating the level of structural damage, while the second is the Macroseismic method.

Key Words
seismic risk; seismic hazard; vulnerability assessment; economic and social loss estimation

Address
Marijana Hadzima-Nyarko and Tanja Kalman Sipos: Faculty of Civil Engineering, University of J.J. Strossmayer, 31000 Osijek, Vladimira Preloga 3, Croatia

Abstract
Earthquake-induced pounding damages to building structures were repeatedly observed in many previous major earthquakes. Extensive researches have been carried out in this field. Previous studies mainly focused on the regular shaped buildings and each building was normally simplified as a single-degree-of-freedom (SDOF) system or a multi-degree-of-freedom (MDOF) system by assuming the masses of the building lumped at the floor levels. The researches on the pounding responses between irregular asymmetric buildings are rare. For the asymmetric buildings subjected to earthquake loading, torsional vibration modes of the structures are excited, which in turn may significantly change the structural responses. Moreover, contact element was normally used to consider the pounding phenomenon in previous studies, which may result in inaccurate estimations of the structural responses since this method is based on the point-to-point pounding assumption with the predetermined pounding locations. In reality, poundings may take place between any locations. In other words, the pounding locations cannot be predefined. To more realistically consider the arbitrary poundings between asymmetric structures, detailed three-dimensional (3D) finite element models (FEM) and arbitrary pounding algorithm are necessary. This paper carries out numerical simulations on the pounding responses between a symmetric rectangular-shaped building and an asymmetric L-shaped building by using the explicit finite element code LS-DYNA. The detailed 3D FEMs are developed and arbitrary 3D pounding locations between these two buildings under bi-directional earthquake ground motions are investigated. Special attention is paid to the relative locations of two adjacent buildings. The influences of the left-and-right, fore-and-aft relative locations and separation gap between the two buildings on the pounding responses are systematically investigated.

Key Words
irregular asymmetric building; arbitrary pounding; 3D FEM; torsional responses; relative location

Address
Kaiming Bi and Hong Hao: Center for Infrastructure Monitoring and Protection, School of Civil and Mechanical Engineering
Zhiguo Sun: Department of Disaster Prevention Engineering, Institute of Disaster Prevention, Beijing 101601, China

Abstract
The first determination and assessment of the damages to structures after the earthquake is important for preventing increase in loss of life and property that may occur in later times. When rapid damage assessment is performed after an earthquake, damage assessment forms are generally used. The forms that are filled in the field are assessed in the office environment later. In this study, while the process of earthquake damage assessment was being carried out, the ready-made form was moved to web base and the data to be obtained in the field was transferred to the database by means of tablets and smart phones. Keeping earthquake damages in a database will contribute to the studies to be conducted on earthquake and the earthquake regulations to be prepared. Furthermore, emergency damage assessment will be performed faster and more reliably after the earthquake through this study. As the data transferred to the web base is accessible to different people, savings will be provided for both time and personnel. Furthermore, the assessment will have a healthier and scientific basis. In this study, exemplification was conducted for six different reinforced concrete buildings that were damaged during Van earthquake in October 23. With this study, damage assessment procedures can be completed as soon as possible.

Key Words
earthquake; damage assessment; reinforced-concrete; web based; database

Address
Ercan Işik: Department of Civil Engineering, Faculty of Engineering and Architecture, Bitlis Eren University, TR13100, Turkey
Mehmet F. Işik: Department of Electric-Electronics Engineering, Faculty of Engineering, Hitit University, TR19030, Turkey
Mehmet A. Bulbul: Department of Computer, Vocational School of Technical Sciences, Hitit University, TR19030, Turkey

Abstract
With the growing demand for metallic dampers in engineering practice, it is urgent to establish a reasonable approach to evaluating the mechanical performance of metallic dampers under seismic excitations. This paper introduces an effective method for parameter identification of the modified Bouc-Wen model and its application to evaluating the fatigue performance of metallic dampers (MDs). The modified Bouc-Wen model which eliminates the redundant parameter is used to describe the hysteresis behavior of MDs. Relations between the parameters of the modified Bouc-Wen model and the mechanical performance parameters of MDs are studied first. A modified Genetic Algorithm using real-integer hybrid coding with relative fitness as well as adaptive crossover and mutation rates (called RFAGA) is then proposed to identify the parameters of the modified Bouc-Wen model. A reliable approach to evaluating the fatigue performance of the MDs with respect to the Chinese Code for Seismic Design of Buildings (GB 50011-2010) is finally proposed based on the research results. Experimental data are employed to demonstrate the process and verify the effectiveness of the proposed approach. It is shown that the RFAGA is able to converge quickly in the identification process, and the simulation curves based on the identification results fit well with the experimental hysteresis curves. Furthermore, the proposed approach is shown to be a useful tool for evaluating the fatigue performance of MDs with respect to the Chinese Code for Seismic Design of Buildings (GB 50011-2010).

Key Words
parameter identification; metallic dampers; Bouc-Wen model; genetic algorithm

Address
Ganping Shu and Zongjing Li: School of Civil Engineering, Southeast University, Nanjing 210096, China

Abstract
In order to analyze the vibration control effect of viscous damper in the concrete archaized buildings with lintel-column joints under seismic action, 3 specimens were tested under dynamic excitation. Two specimens with viscous damper were defined as the controlled component and one specimen without viscous damper was specified as the non-controlled component. The loading process and failure patterns were obtained from the test results. The failure characteristics, skeleton curves and mechanical behavior such as the load-displacement hysteretic loops, load carrying capacity, degradation of strength and rigidity, ductility and energy dissipation of the joints were analyzed. The results indicate that the load-bearing capacity of the controlled component is significantly higher than that of the non-controlled component. The former component has an average increase of 27.4% in yield load and 22.4% in ultimate load, respectively. Meanwhile, the performance of displacement ductility and the ability of energy dissipation for the controlled component are superior to those of the non-controlled component as well. Compared with non-controlled component, equivalent viscous damping coefficients are improved by 27.3%-30.8%, the average increase is 29.0% at ultimate load for controlled component. All these results reflect that the seismic performance of the controlled component is significantly better than that of the non-controlled component. These researches are helpful for practical application of viscous damper in the concrete archaizing buildings with lintel-column joints.

Key Words
archaized buildings; dynamic test; seismic behavior; viscous damper

Address
Jianyang Xue and Jinshuang Dong: School of Civil Engineering, Xi\' an University of Architecture and Technology, Xi\' an, Shaanxi, China
Yan Sui: State Key Laboratory of Architecture Science and Technology in West China, Xi\' an, Shaanxi, China

Abstract
Seismic safety evaluation of weir structure is significant considering the catastrophic economical consequence of operational disruption. In recent years, the seismic probabilistic risk assessment (SPRA) has been issued as a key area of research for the hydraulic system to mitigate and manage the risk. The aim of this paper is to assess the seismic probabilistic risk of weir structures employing the seismic hazard and the structural fragility in Korea. At the first stage, probabilistic seismic hazard analysis (PSHA) approach is performed to extract the hazard curve at the weir site using the seismic and geological data. Thereafter, the seismic fragility that defines the probability of structural collapse is evaluated by using the incremental dynamic analysis (IDA) method in accordance with the four different design limit states as failure identification criteria. Consequently, by combining the seismic hazard and fragility results, the seismic risk curves are developed that contain helpful information for risk management of hydraulic structures. The tensile stress of the mass concrete is found to be more vulnerable than other design criteria. The hazard deaggregation illustrates that moderate size and far source earthquakes are the most likely scenario for the site. In addition, the annual loss curves for two different hazard source models corresponding to design limit states are extracted.

Key Words
seismic risk assessment; weir structure; seismic fragility; seismic hazard analysis; annual loss

Address
Jahangir Alam and Dookie Kim: Civil and Environmental Engineering, Kunsan National University, 558 Daehak-ro, Gunsan-si 54150, Republic of Korea
Byounghan Choi: Rural Research Institute, 870, Haean-ro Sangnok-gu, Ansan-si Gyeonggi-do, 15634, Republic of Korea


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2018 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: subs@techno-press.com