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CONTENTS
Volume 16, Number 4, April 2019
 

Abstract
During earthquakes, the performance of structures needs to be evaluated, which provides guidance for selecting suitable retrofitting schemes. The purpose of this paper is to accomplish seismic assessment of a simple steel residential building. Once the responses of the system are determined, the scope of the study extends to evaluate selected retrofitting strategies that are intended to rehabilitate the flaws of the structure under prescribed ground motions with high probability of occurrence at the site. After implementing the retrofits, seismic assessment of the upgraded structure is carried out to check if the remediation at various seismic performance levels is acquired or not. Outcomes obtained from retrofitted scenarios are compared to the results obtained from the initial un-retrofitted configuration of the structure. This paper presents the process for optimal selection of rehabilitation solutions considering the cost of implementation, downtime and disruption to property owners while improving the seismic performance level of the structure.

Key Words
seismic assessment; retrofitting; passive damper; base isolation; structural weakening

Address
Mengqi Yang: School of Geographical Sciences, Gangzhou University, Guangzhou, Guangdong, 510006, China
Chi Zhang: School of Geography, South China Normal University, Guangzhou, Guangdong, 510631, China

Abstract
Residual deformation of high-speed railway bridge piers is cumulative under repeated earthquakes, and influences the safety and ride comfort of high-speed trains. This paper investigates the effects of the peak ground acceleration, longitudinal reinforcement ratio, and axial compression ratio on the cumulative deformation through finite element analysis. A simply-supported beam bridge pier model is established using nonlinear beam-column elements in OpenSees, and validated against a shaking table test. Repeated earthquakes were input in the model. The results show that the cumulative deformation of the bridge piers under repeated earthquakes increases with the peak ground acceleration and the axial compression ratio, and decreases with the longitudinal reinforcement ratio.

Key Words
cumulative residual deformation; high-speed railway bridge piers; repeated earthquakes; nonlinear numerical model; parametric studies

Address
Hongye Gou: Department of Bridge Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China; Key Laboratory of High-Speed Railway Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
Dan Leng: Department of Bridge Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China
Yi Bao: Department of Civil, Environmental and Ocean Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA
Qianhui Pu: Department of Bridge Engineering, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China

Abstract
The concept of base isolation for equipment is well known. Its application in buildings and structures is rather challenging. Introduction of horizontal flexibility at the base helps in proper energy dissipation at the base level thus reducing the seismic demand of the super structure to be considered during design. The present study shows the results of a series of numerical simulation studies on seismic responses of secondary system (SS) housed in non-isolated and base-isolated primary structures (PS) including equipment-structure interactions. For this study the primary structure consists of two similar single bay three-store reinforced cement concrete (RCC) Frame building, one non-isolated with conventional foundation and another base isolated with Lead plug bearings (LPB) constructed at IIT Guwahati, while the secondary system is modeled as a steel frame. Time period of the base isolated building is higher than the fixed building. Due to the presence of isolator, Acceleration response is significantly reduced in both (X and Y) direction of Building. It have been found that when compared to fixed base building, the base isolated building gives better performance in high seismic prone areas.

Key Words
base isolation; equipment; primary structure; secondary structure; lead plug bearing; response spectra

Address
Pardeep Kumar and Sandeep Petwal: Civil Engineering Department, National Institute of Technology, Hamirpur, Himachal Pradesh India

Abstract
Near-fault ground motions can impose particularly high seismic demands on structures due to the pulses that are typically observed in the velocity time-histories. In this study it is empirically found that the critical response can be estimated from the directions corresponding to the maximum (max) or minimum (min) pulse-energy. Determination of the pulse-energy requires removing of the high-frequency content. For achieving this, the wavelet analysis and the least-square-fitting (LSF) algorithm are adopted. Results obtained by the two strategies are compared and differences between them are analyzed. Finally, the relationship between the critical response and the response derived from directions having the max or min pulse-energy confirms that using the pulse-energy for deriving the critical response of the building structures is reasonable.

Key Words
near-fault; pulse-like; ground motions; pulse-energy; critical response

Address
Zhiwang Chang, Zhanhui Liu, Zhenhua Chen: School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, P.R. China
Changhai Zhai: School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, P.R. China

Abstract
Successive ground motions having short time intervals have occurred in many earthquakes so far. It is necessary to investigate the effects of this phenomenon on different types of structures and to take these effects into consideration while designing or retrofitting structures. The effects of seismic sequences on the structures with combined reinforced concrete shear wall and moment resisting frame system have not been investigated in details yet. This paper has tried to analyse the seismic performance of structures with such structural systems subjected to mainshock-aftershock sequences. The effects of the seismic sequences on the investigated models are evaluated by strong measures such as IDA capacity and fragility and vulnerability curves. The results of this study show that the seismic sequences have a significant effect on the investigated models, which necessitates considering this effect on designing, retrofitting, decision making, and taking precautions.

Key Words
safety; aftershock; shear wall; reinforced concrete; vulnerability

Address
Hosein Naderpour and Khadijeh Vakili: Faculty of Civil Engineering, Semnan University, Semnan, Iran

Abstract
This study investigates a new optimal placement method for viscous dampers between structures in order to prevent pounding of adjacent structures with different dynamic characteristics under earthquake effects. A relative displacement spectrum is developed in two single degree of freedom system to reveal the critical period ratios for the most risky scenario of collision using El Centro earthquake record (NS). Three different types of viscous damper design, which are classical, stair and X-diagonal model, are considered to prevent pounding on two adjacent building models. The objective function is minimized under the upper and lower limits of the damping coefficient of the damper and a target modal damping ratio. A new algorithm including time history analyses and numerical optimization methods is proposed to find the optimal dampers placement. The proposed design method is tested on two 12-storey adjacent building models. The effects of the type of damper placement on structural models, the critical period ratios of adjacent structures, the permissible relative displacement limit, the mode behavior and the upper limit of damper are investigated in detail. The results of the analyzes show that the proposed method can be used as an effective means of finding the optimum amount and location of the dampers and eliminating the risk of pounding.

Key Words
pounding, collision; relative displacement spectrum; viscous dampers; adjacent structures; earthquake resistant structures

Address
Turan Karabork: Aksaray University, Engineering Faculty, Department of Civil Engineering, Aksaray, Turkey
Ersin Aydin: Nigde Ömer Halisdemir University, Engineering Faculty, Department of Civil Engineering, Nigde, Turkey

Abstract
The behavior of pile-deck connections of pile-supported marginal wharfs subjected to earthquake loading is of key importance to ensure a good performance of this type of structures. Two precast-pretensioned pile-deck connections used in the construction of pile-supported marginal wharfs were tested under cyclic loading. The first is a connection with simple reinforcement details and light steel ratio developed for use where moderate pile-deck rotation demands are expected in the wharf. The second is specifically developed to sustain the large rotation, shear force and bending moment demands, as required for the shortest piles in a marginal wharf. Data obtained from the test program is used in the paper to calibrate an equivalent plastic hinge length that can be incorporated into nonlinear analysis models of these structures when prestressed pile-deck connections with duct embedded dowels are used.

Key Words
marine structures; performance-based seismic design; prestressed piles; pile-deck connection; seismic design; testing; wharves

Address
Carlos A. Blandon: Department of Civil Engineering, EIA University, Km 2 +200 Variante Aeropuerto. JMC, Envigado, Colombia
Christopher J. Krier: NV5, 2650 18th Street, Suite 202, Denver, Colorado 80211, USA
Jose I. Restrepo: Department of Civil Engineering, University of California San Diego, 9500 Gilman Dr, La Jolla, CA 92093, USA

Abstract
A numerical investigation regarding local (uL) and story (uS) ductility demand evaluation of steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF), is conducted in this study. The interior connections are modeled, firstly as perfectly pinned (PP), and then as semi-rigid (SR). Three models used in the SAC steel project, representing steel buildings of low-, mid-, and high-rise, are considered. The story ductility reduction factor (RuS) as well as the ratio (QGL) of RuS to uL are calculated. uL and uS, and consequently structural damage, at the PMRF are significant reduced when the usually neglected effect of SR connections is considered; average reductions larger than 40% are observed implying that the behavior of the models with SR connections is superior and that the ductility detailing of the PMRF doesn\'t need to be so stringent when SR connections are considered. RuS is approximately constant through height for low-rise buildings, but for the others it tends to increase with the story number contradicting the same proportion reduction assumed in the Equivalent Static Lateral Method (ESLM). It is implicitly assumed in IBC Code that the overall ductility reduction factor for ductile moment resisting frames is about 4; the results of this study show that this value is non-conservative for low-rise buildings but conservative for mid- and high-rise buildings implying that the ESLM fails evaluating the inelastic interstory demands. If local ductility capacity is stated as the basis for design, a value of 0.4 for QGL seems to be reasonable for low- and medium-rise buildings.

Key Words
steel building; moment resisting frames; local and story ductility; ductility and force reduction factors; pinned and semi-rigid connections; 3D models; nonlinear analysis

Address
Mario D. Llanes-Tizoc, Alfredo Reyes-Salazar, Eden Bojorquez, Juan Bojorquez and Jesus M. Leal Graciano: Facultad de Ingenieria, Universidad Autonoma de Sinaloa, Culiacan, Sinaloa, 80040, Mexico
Sonia E. Ruiz: Instituto de Ingenieria, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Coyoacan, Ciudad de Mexico, Mexico

Abstract
Energy-based seismic design of structures has gradually become prominent in today

Key Words
energy-based approach; ground motion record; the maximum earthquake input energy; response time history analysis; pseudo-spectral velocity

Address
Onur Merter: Department of Civil Engineering, Usak University, 64100, Usak, Turkey

Abstract
In this study, seismic vulnerability assessment and seismic isolation retrofit of Bayburt Yakutiye Mosque is investigated. Bayburt Yakutiye Mosque was built in the early 19th century at about 30-meter distance to Coruh river in the center of Bayburt in Turkey. The walls of historical masonry structure were built with regional white and yellow stones and the domes of the mosque was built with masonry bricks. This study is completed in four basic phases. In first phase, experimental determination of the regional white stone used in the historical structure are investigated to determine mechanical properties as modulus of elasticity, poison ratio and compression strengths etc. The required information of the other materials such as masonry brick and the regional yellow stone are obtained from literature studies. In the second phase, three dimensional finite element model (FEM) of the historical masonry structure is prepared with 4738 shell elements and 24789 solid elements in SAP2000 software. In third phase, the vulnerability assessment of the historical mosque is researched under seismic loading such as Erzincan (13 March 1992), Kocaeli (17 August 1999) and Van (23 November 2011) earthquakes. In this phase, the locations where damage can occur are determined. In the final phase, rubber base isolators for seismic isolation retrofit is used in the macro model of historical masonry mosque to prevent the damage risk. The results of all analyses are comparatively evaluated in details and presented in tables and graphs. The results show that the application of rubber base isolators can prevent to occur the destructive effect of earthquakes.

Key Words
seismic vulnerability assessment; experimental tests; historical masonry structure; FEM model; seismic isolation retrofit

Address
Musa Artar, Muhammet Yurdakul, Omer Canb, Fatih Yilmaz: Department of Civil Engineering, Bayburt University, Bayburt 69000, Turkey
Keziban Coban, Mehmet B. Yildiz: Institute of Science and Technology, Bayburt University, Bayburt 69000, Turkey

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