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CONTENTS
Volume 10, Number 4, April 2016
 

Abstract
This article presents a proposed analytical methodology to determine seismic force-resisting system R-values for steel diagrid framed systems. As current model building codes do not explicitly address the seismic design performance factors for this new and emerging structural system, the purpose of this study is to provide a sound and reliable basis for defining such seismic design parameters. An approach and methodology for the reliable determination of seismic performance factors for use in the design of steel diagrid framed structural systems is proposed. The recommended methodology is based on current state-of-the-art and state-of-the practice methods including structural nonlinear dynamic analysis techniques, testing data requirements, building code design procedures and earthquake ground motion characterization. In determining appropriate seismic performance factors (R, ΩO, Cd) for new archetypical building structural systems, the methodology defines acceptably low values of probability against collapse under maximum considered earthquake ground shaking.

Key Words
diagrid; seismic performance factor; structural system; analytical methodology

Address
Dongkyu Lee: Department of Architectural Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul, 143-747, Korea

Soomi Shin: Research Institute of Industrial Technology, Pusan National University, Busan, 609-735, Korea

Youngkyu Ju: School of Civil, Environmental and Architectural Engineering, Korea University, Anam-ro 145, Seongbuk-gu,
Seoul, 136-713, Korea

Abstract
In the past decades, effect of near field earthquake on the historical monuments has attracted the attention of researchers. So, many analyses in this regard have been presented. Tunnels as vital arteries play an important role in management after the earthquake crisis. However, digging tunnels and seismic effects of earthquake on the historical monuments have always been a challenge between engineers and historical supporters. So, in a case study, effect of near field earthquake on the historical monument was investigated. For this research, Finite Element Analysis (FEM) in soil environment and soil-structure interaction was used. In Plaxis 2D software, different accelerograms of near field earthquake were applied to the geometric definition. Analysis validations were performed based on the previous numerical studies. Creating a nonlinear relationship with space parameter, time, angular and numerical model outputs was of practical and critical importance. Hence, artificial Neural Network (ANN) was used and two linear layers and Tansig function were considered. Accuracy of the results was approved by the appropriate statistical test. Results of the study showed that buildings near and far from the tunnel had a special seismic behavior. Scattering of seismic waves on the underground tunnels on the adjacent buildings was influenced by their distance from the tunnel. Finally, a static test expressed optimal convergence of neural network and Plaxis.

Key Words
soil-structure interaction; tunnel; historical monuments; artificial neural network (ANN); near field earthquake

Address
Mohsen Jafarnia: Faculty of Engineering, Central Tehran Branch - Islamic Azad University, No. 49 Mofatteh Ave. Tehran, Iran

Mehdi Imani Varzaghani: Faculty of Engineering, Kharazmi University, No. 1 orag Ave., Tehran, Iran

Abstract
The present study aimed at investigating the effect of a special plaster on the out-of-plane behavior of masonry walls. A reference specimen, plastered with conventional plaster, and a specimen plastered with a special plastered were tested under reversed cyclic lateral loading. The specimens were identical in dimensions and material properties. The special plaster contained an additive, which increased the adherence strength of the plaster to the wall. The amount of the additive in the mortar was adjusted based on the preliminary material tests. The influence of the plaster on the wall behavior was evaluated according to the initial cracking load, type of failure, energy absorption capacity (modulus of toughness), and crack pattern of the wall. Despite having limited contribution to the ductility, the special plaster increased the ultimate load capacity of the wall about 25%. The failure mode of the wall with special plaster resembled the plastic failure mechanism of a reinforced concrete slab in the formation of yielding lines along the wall. The deflection at failure and the modulus of toughness of the wall with special plaster were measured to be in order of 60% and 75% of the corresponding values of the reference wall.

Key Words
composite plaster; earthquake loading; plastered infill wall; out-of-plane behavior

Address
Mahmut Sami Donduren: Department of Civil Engineering, Faculty of Engineering, Selcuk University, 42075 Konya, Turkey

Recep Kanit: Department of Civil Engineering, Faculty of Technology, Gazi University, 06500 Ankara,Turkey

Ilker Kalkan: Department of Civil Engineering, Faculty of Engineering, Kirikkale University, 71450 Kirikkale, Turkey

Osman Gencel: Department of Civil Engineering, Faculty of Engineering, Bartin University, 74100 Bartin, Turkey

Abstract
Reinforced concrete (RC) bridges with both skew and curvature are pretty common in areas with complex terrains. Existing studies have shown skewed and/or curved bridges exhibit more complicated seismic performance than straight bridges, and yet related seismic risk studies are still rare. These bridges deserve more studies in low-to-moderate seismic regions than those in seismic-prone areas. This is because for bridges with irregular and complex geometric designs, comprehensive seismic analysis is not always required and little knowledge about actual seismic risks for these bridges in low-to-moderate regions is available. To provide more insightful understanding of the seismic risks and the impact from the geometric configurations, analytical fragility studies are carried out on four typical bridge designs with different geometric configurations (i.e., straight, curved, skewed, skewed and curved) in the mountain west region of the United States. The results show the curved and skewed geometries can considerably affect the bridge seismic fragility in a complex manner, underscoring the importance of conducting detailed seismic risk assessment of skewed and curved bridges in low-to-moderate seismic regions.

Key Words
seismic; curved and skewed bridge; fragility; risk; FEM analysis

Address
Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, USA

Abstract
This study aims to present nonlinear time history analysis results of double leaf cavity wall (DLCW) reinforced concrete structure exposed to shake table tests. Simulation of the model was done by a Finite Element (FE) program. Shake table experiment was performed at the National Civil Engineering Laboratory in Lisbon, Portugal. The results of the experiment were compared with numeric DLCW model and numeric model of reinforced concrete structure with unreinforced masonry wall (URM). Both DLCW and URM models have two bays and two stories. Dimensions of the tested structure and finite element models are 1:1.5 scaled according to Cauchy Froude similitude law. The URM model has no experimental results but the purpose is to compare their performance level with the DLCW model. Results of the analysis were compared with experimental response and were evaluated according to ASCE/SEI 41-06 code.

Key Words
infill wall; nonlinear time history analysis; finite element; shake table

Address
Onur Onat: Department of Civil Engineering, Tunceli University, Tunceli, Turkey

Paulo B. Lourenco: ISISE, Department of Civil Engineering, University of Minho, Guimaraes, Portugal

Ali Kocak: Department of Civil Engineering, Yildiz Technical University, İstanbul, Turkey

Abstract
Generally seismic isolation is achieved by supporting the structure on laminated rubber bearings, friction pendulum bearings, roller bearings etc. Very little work has been performed using soil as a base isolation media. Experiments and analytical work has been performed on a structural model with isolated footing and found encouraging results. Details of this work are presented in this paper.

Key Words
isolated footings; natural seismic base isolation; modulus reduction; IS 1893

Address
S.J. Patil: Heavy Water Board, Mumbai, India

G.R. Reddy, Binu Kumar: BARC & HBNI, Mumbai, India

R. Shivshankar, B.R. Jayalekshmi: NITK, Suratkal, India

Ramesh Babu: CPRI, Banglore, India

Abstract
Beside the invaluable advancements in constructing more secure buildings, the post-earthquake inspections have reported considerable damages. In other words, the modern buildings satisfactorily decrease fatalities but the monetary impacts still mostly remain an unsolved concern of the stakeholders, the insurance companies and society together. Therefore, the fundamental target of the researches shifted from current force-based seismic design regulations to the Performance-Based earthquake engineering (PBEE). At the moment, some probabilistic approaches, such as PEER framework have been developed to predict the performance of building at any desired hazard levels. These procedures are so time-consuming, to which many details are needed to be assigned. It causes their usage to be limited. On that account, developing more straightforward methods seems indispensable. The main objective of the present paper is to adapt an equivalent static method in different damage states. Consequently, constant damage spectrums corresponding to different limit states, soil types, ductility and fundamental periods are plotted and tri-linear formulas are proposed for further applications. Moreover, the sensitivity of outcomes to the employed hysteresis model, ductility, viscous damping and site soil type is investigated. Finally, a case study building with moment-resisting R.C. frame is evaluated based on the both of new and current methods to ensure applicability of the proposed method.

Key Words
performance-based seismic design; equivalent static analysis; damage index; constant damage spectrum; dynamic analysis

Address
Reza Allahvirdizadeh and Mohammad Ali Mohammadi: School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran

Reza Allahvirdizadeh: Engineering Optimization Research Group (EORG), College of Engineering,
University of Tehran, Tehran, Iran

Abstract
This paper addresses numerically the behavior of steel structures under Fire-after-Earthquake (FAE) loading. The study is focused on a four-storey library building and takes into account the damage that is induced in structural members due to earthquake. The basic objective is the assessment of both the firebehavior and the fire-resistance of the structure in the case where the structure is damaged due to earthquake. The combined FAE scenarios involve two different stages: during the first stage, the structure is subjected to the ground motion record, while in the second stage the fire occurs. Different time-acceleration records are examined, each scaled to multiple levels of the Peak Ground Acceleration (PGA) in order to represent more severe earthquakes with lower probability of occurrence. In order to study in a systematic manner the behavior of the structure for the various FAE scenarios, a two-dimensional beam finite element model is developed, using the non-linear finite element analysis code MSC-MARC. The fire resistance of the structure is determined using rotational limits based on the ductility of structural members that are subjected to fire. These limits are temperature dependent and take into account the level of the structural damage at the end of the earthquake and the effect of geometric initial imperfections of structural members.

Key Words
Fire-After-Earthquake loading; frame structures; rotational capacity; fire-resistance

Address
Laboratory of Structural Analysis and Design, Department of Civil Engineering, University of Thessaly, Pedion Areos, Volos, Greece

Abstract
There are some modifications in the usage purpose of historical structures due to varying needs and changing conditions. However, those modifications can damage the structural system and the system stability. This study focuses on the investigation of the functional effects and usage modifications on the system stability. In this study, three different finite element models of the Hayati Teknecioglu Mansion in Turkey are developed and the seismic responses of the models are investigated. Results of the analyses show that usage modifications might be considered as risky in terms of creating problems for seismic performance.

Key Words
himis structures; the modification of intended usage; seismic analyses; Finite Element Method (FEM)

Address
Ferit Cakir: Department of Architecture, Faculty of Architecture, Yildiz Technical University, Istanbul, Turkey

Ferit Cakir: Visiting Scholar at Pacific Earthquake Engineering Research Center (PEER), UC Berkeley, CA, USA

Yasar B. Ergen: Department of Urban Planning, Faculty of Architecture, Amasya University, Amasya, Turkey

Habib Uysal: Department of Civil Engineering, Faculty of Engineering, Ataturk University, Erzurum, Turkey

Adem Dogangun: Department of Civil Engineering, Faculty of Engineering and Architecture, Uludag University, Bursa, Turkey

Abstract
´Stepped building´ frames, with vertical geometric irregularity, are now increasingly encountered in modern urban constructions. This paper proposes a new approach to determine the lateral load pattern, considering the contributions from the higher modes, suitable for pushover analysis of stepped buildings. Also, a modification to the displacement coefficient method of ASCE/SEI 41-13 is proposed, based on nonlinear time history analysis of 78 stepped frames. When the newly proposed load pattern is combined with the modified displacement coefficient method, the target displacement for the stepped building frame is found to match consistently the displacement demand given by the time history analysis.

Key Words
stepped building; pushover analysis; lateral load pattern; displacement coefficient method; target displacement

Address
Pradip Sarkar: Department of Civil Engineering, National Institute of Technology Rourkela, Odisha - 769 008, India

A. Meher Prasad and Devdas Menon: Department of Civil Engineering, Indian Institute of Technology Madras, Chennai - 600 036, India

Abstract
According to the new directives about the rational and efficient use of energy, thermal bridges in buildings have to be avoided, and the thermal insulation (TI) layer should run without interruptions all around the building - even under its foundations. The paper deals with the seismic response of multistoreyed reinforced concrete (RC) frame building structures founded on an extruded polystyrene (XPS) layer placed beneath the foundation slab. The purpose of the paper is to elucidate the problem of buildings founded on a TI layer from the seismic resistance point of view, to assess the seismic behaviour of such buildings, and to search for the critical parameters which can affect the structural and XPS layer response. Nonlinear dynamic and static analyses were performed, and the seismic response of fixed-base (FB) and thermally insulated (TI) variants of nonlinear RC building models were compared. Soil-structure interaction was also taken into account for different types of soil. The results showed that the use of a TI layer beneath the foundation slab of a superstructure generally induces a higher peak response compared to that of a corresponding system without TI beneath the foundation slab. In the case of stiff structures located on firm soil, amplification of the response might be substantial and could result in exceedance of the superstructure´s moment-rotation plastic hinge capacities or allowable lateral roof and interstorey drift displacements. In the case of heavier, slenderer, and higher buildings subjected to stronger seismic excitations, the overall response is governed by the rocking mode of oscillation, and as a consequence the compressive strength of the XPS could be insufficient. On the other hand, in the case of low-rise and light-weight buildings, the friction capacity between the layers of the applied TI foundation set might be exceeded so that sliding could occur.

Key Words
foundation on thermal insulation; extruded polystyrene (XPS); seismic response; RC structure; soil-structure interaction; nonlinear seismic analysis

Address
Faculty of Architecture, University of Ljubljana, Zoisova 12, SI-1000 Ljubljana, Slovenia

Abstract
This paper investigates the seismic behavior of reinforced concrete shear wall buildings with multiple underground stories. A base-case where the buildings are modeled with a fixed condition at ground level is adopted, and then the number of basements is incrementally increased to evaluate changes in performance. Two subsurface site conditions, corresponding to very dense sands and medium dense sands, are used for the analysis. In addition, three ground shaking levels are used in the study. Results of the study indicated that while the common design practice of cropping the structure at the ground surface leads to conservative estimation of the base shear for taller and less rigid structures; it results in unpredicted and nonconservative trends for shorter and stiffer structures.

Key Words
soil structure interaction; shear wall buildings; underground stories; nonlinear time history analysis

Address
Department of Civil and Environmental Engineering, American University of Beirut, Beirut, Lebanon


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