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CONTENTS
Volume 14, Number 6, June 2018
 

Abstract
With the further increase of span length, the cable-stayed bridge tends to be more slender, and becomes more susceptible to the seismic action. By taking a super long-span cable-stayed bridge with main span of 1400m as example, structural response of the bridge under the E1 horizontal and vertical seismic excitations is investigated numerically by the multimode seismic response spectrum and time-history analysis respectively, the seismic behavior and also the effect of structural nonlinearity on the seismic response of super long-span cable-stayed bridge are revealed. Furthermore, the effect of structural parameters including the girder depth and width, the tower structural style, the tower height-to-span ratio, the side-tomain span ratio, the auxiliary piers in side spans and the anchorage system of stay cables etc on the seismic performance of super long-span cable-stayed bridge is investigated numerically by the multimode seismic response spectrum analysis, and the favorable earthquake-resistant structural system of super long-span cable-stayed bridge is proposed.

Key Words
super long-span cable-stayed bridge; seismic performance; multimode seismic response spectrum analysis; time-history analysis; structural parameters

Address
Xin-Jun Zhang, Chen-Yang Zhao and Jian Guo: College of Civil Engineering & Architecture, Zhejiang University of Technology, Hangzhou 310023, P.R. China

Abstract
Static pushover analyses of typical existing reinforced concrete frames, designed according to the previous generations of design codes in Greece, have established these structures\' inelastic characteristics, namely overstrength, global ductility capacity and available behaviour factor q, under planar response. These were compared with the corresponding demands at the collapse limit state target performance point. The building stock considered accounted for the typical variability, among different generations of constructed buildings in Greece, in the form, the seismic design code in effect and the material characteristics. These static pushover analyses are extended, in the present study, in the time history domain. Consequently, the static analysis predictions are compared with Incremental Dynamic Analysis results herein, using a large number of spectrum compatible recorded base excitations of recent destructive earthquakes in Greece and abroad, following, for comparison, similar conventional limiting failure criteria as before. It is shown that the buildings constructed in the 70s exhibit the least desirable behaviour, followed by the buildings constructed in the 60s. As the seismic codes evolved, there is a notable improvement for buildings of the 80s, when the seismic code introduced end member confinement and the requirement for a joint capacity criterion. Finally, buildings of the 90s, designed to modern codes exhibit an exceptionally good performance, as expected by the compliance of this code to currently enforced seismic provisions worldwide.

Key Words
existing RC buildings; seismic design code; comparative analysis; nonlinear dynamic analysis; performance evaluation; ductility; behaviour factor

Address
Christos A. Zeris: Department of Civil Engineering, National Technical University of Athens, University Campus, Zografou 15780, Greece
Constantinos C. Repapis: Department of Civil Engineering, University of West Attica, 250 Thivon and Petrou Ralli Str., Egaleo 12244, Greece

Abstract
This study presents a new beam-column model comprising material nonlinearity and joint flexibility to predict the nonlinear response of reinforced concrete structures. The nonlinear behavior of connections has an outstanding role on the nonlinear response of reinforced concrete structures. In presented research, the joint flexibility is considered applying a rotational spring at each end of the member. To derive the moment-rotation behavior of beam-column connections, the relative rotations produced by the relative slip of flexural reinforcement in the joint and the flexural cracking of the beam end are taken into consideration. Furthermore, the considered spread plasticity model, unlike the previous models that have been developed based on the linear moment distribution subjected to lateral loads includes both lateral and gravity load effects, simultaneously. To confirm the accuracy of the proposed methodology, a simply-supported test beam and three reinforced concrete frames are considered. Pushover and nonlinear dynamic analysis of three numerical examples are performed. In these examples the nonlinear behavior of connections and the material nonlinearity using the proposed methodology and also linear flexibility model with different number of elements for each member and fiber based distributed plasticity model with different number of integration points are simulated. Comparing the results of the proposed methodology with those of the aforementioned models describes that suggested model that only uses one element for each member can appropriately estimate the nonlinear behavior of reinforced concrete structures.

Key Words
material nonlinearity; joint flexibility; spread plasticity; lateral load; gravity load

Address
Mehdi Izadpanah: Department of Civil Engineering, Kangavar Branch, Islamic Azad University, Kangavar, Iran
AliReza Habibi: Department of Civil Engineering, Shahed University, Tehran, Iran

Abstract
Using vertical links in eccentric braced frames is one of the best passive structural control approaches due to its effectiveness and practicality advantages. However, in spite of the subject importance there are limited studies which evaluate the seismic reliability and response reduction factor (R-factor) in this system. Therefore, the present study has been conducted to improve the current understanding about failure mechanism in the structural systems equipped with vertical links. For this purpose, following definition of demand and capacity response reduction factors, these parameters are computed for three different buildings (4, 8 and 12 stories) equipped with this system. In this regards, pushover and incremental dynamic analysis have been employed, and seismic reliability as well as multi-level response reduction factor according to the seismic demand and capacity of the frames have been derived. Based on the results, this system demonstrates high ductility and seismic energy dissipation capacity, and using the response reduction factor as high as 8 also provides acceptable reliability for the frame in the moderate and high earthquake intensities. This system can be used in original buildings as lateral load resisting system in addition to seismic rehabilitation of the existing buildings.

Key Words
vertical links; eccentric braced frame; response reduction factor; seismic reliability

Address
Vahid Mohsenian and Alireza Mortezaei: Seismic Geotechnical and High Performance Concrete Research Centre, Civil Engineering Department, Semnan Branch, Islamic Azad University, Semnan, Iran

Abstract
Experimental testing is considered the most realistic approach to obtain a detailed representation of the nonlinear behaviour of masonry-infilled reinforced concrete (RC) structures. Among other applications, these tests can be used to calibrate the properties of numerical models such as simplified macro-models (e.g., strut-type models) representing the masonry infill behaviour. Since the significant cost of experimental tests limits their widespread use, alternative approaches need to be established to obtain adequate data to validate the referred simplified models. The proposed paper introduces a detailed finite element modelling strategy that can be used as an alternative to experimental tests to represent the behaviour of masonry-infilled RC frames under earthquake loading. Several examples of RC infilled frames with different infill configurations and properties subjected to cyclic loading are analysed using the proposed modelling approach. The comparison between numerical and experimental results shows that the numerical models capture the overall nonlinear behaviour of the physical specimens with adequate accuracy, predicting their monotonic stiffness, strength and several failure mechanisms.

Key Words
masonry infill; reinforced concrete structure; finite element model; ANSYS; cyclic loading

Address
Hossameldeen M. Mohamed: CONSTRUCT-LESE, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal; Department of Civil Engineering, Faculty of Engineering, Aswan University, Abo El-Reesh Mail Box NO.: 81542, Aswan, Egypt
Xavier Romao: University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal

Abstract
This manuscript introduces a new damping device which is composed of a water tank and a pendulum. The new damping device can be tuned to multiple frequencies. In addition, it has a higher energy dissipation capacity when compared with the conventional Tuned Liquid Dampers (TLDs). In order to evaluate the efficiency of this new damping device a series of free vibration and forced vibration tests were conducted on a scaled down single-story one-bay steel frame. Two different configurations were studied for the mass of the pendulum that included a completely and a partially submerged mass. It was observed that the completely submerged configuration led to 44% higher damping ratio when compared with the conventional TLD. In addition, the completely submerged configuration reduced the peak displacement response of the structure 1.6 times more than the conventional TLD. The peak acceleration response of the structure equipped with the new damping device was reduced twice more than the conventional TLD. It was also found that, when the excitation frequency is lower than the resonance frequency, the conventional TLD performs better than the partially submerged configuration of the new damping device.

Key Words
tuned liquid damper; free vibration; forced vibration; structural control; dynamic responses

Address
Sophia C. Alih: Inistitute of Noise and Vibration, Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor, Malaysia
Mohammadreza Vafaei, Nufail Ismail: Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor, Malaysia
Ali Pabarja: Department of Civil and Structural Engineering, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia

Abstract
The quantitative assessment of the seismic collapse risk of a structure requires the usage of an optimal intensity measure (IM) which can adequately characterise the severity of the ground motion. Research suggests that the average spectral acceleration (Saavg) may be an efficient and sufficient alternate IM as compared to the more traditional first mode spectral acceleration, Sa(T1), particularly during seismic collapse risk estimation. This study primarily presents a comparative evaluation of the sufficiency of the average spectral acceleration with respect to ground motion duration, and secondarily assesses the impact of ground motion duration on collapse risk estimation. By assembling a suite of 100 historical ground motions, incremental dynamic analysis of 60 different inelastic single-degree-of-freedom (SDF) oscillators with varying periods and ductility capacities were analysed, and collapse risk estimates obtained. Linear regression models are used to comparatively quantify the sufficiency of Saavg and Sa(T1) using four significant duration metrics. Results suggests that an improved sufficiency may exist for Saavg when the period of the SDF system increases, particularly beyond 0.5, as compare to Sa(T1). In reference to the ground motion duration measures, results indicated that the sufficiency of Saavg is more sensitive to significant duration definitions that consider almost the full wave train of an accelerogram (SDa5-95 and SDv5-95). In order to obtain a reduced variability of the collapse risk estimate, the 5-95% significant duration metric defined using the Arias integral (SDa5-95) should be used for seismic collapse risk estimation in conjunction with Saavg.

Key Words
average spectral acceleration; sufficiency; significant duration; earthquake-induce ground motion

Address
Jack Banahene Osei and Mark Adom-Asamoah: Department of Civil Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

Abstract
An attempt is conducted to explore the relationship between the macroscopic global damage and the local damage of shear-type RC frames. A story damage index, which can be expressed as multi-variate functions of modal parameters, is deduced based on the tridiagonal matrix of the shear-type frame. The global damage model is also originated from structural modal parameters. Due to the connection of modal damage indexes, the relationship between the macroscopic global damage and the local story damage is reasonably established. In order to validate the derivation, a case study is carried out via an 8-story shear-type frame. The sensitivities of modal damage indexes to the location and severity of local story damages are studied. The evolution of the global damage is investigated as well. Results show that the global damage is sensitive to the degree of story damage, but it\'s not sensitive to its location. As the number of the damaged stories increases, more and more modes will be involved. Meanwhile, the global damage evolution curve changes from the concave shape to the S-type and then finally transforms into the convex shape. Through the proposed story damage, modal damage and global damage model, a multi-level damage assessment method is established.

Key Words
vibration mode; story damage; modal damage; global damage; frame

Address
Xiang Guo: School of Civil Engineering, Dalian University of Technology, Dalian 116024, China
Zheng He: School of Civil Engineering, Dalian University of Technology, Dalian 116024, China; State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

Abstract
This study focuses on the earthquake performance of two URM buildings having typical architectural configurations common for residential use constructed per pre-modern code in Albania. Both buildings are unreinforced clay brick masonry structures constructed in 1960 and 1984, respectively. The first building is a three-storey unreinforced one with masonry walls. The second one is confined masonry rising on five floors. Mechanical characteristics of masonry walls were determined based on experimental tests conducted according to ASTM C67-09 regulations. A global numerical model of the buildings was built, and masonry material was simulated as nonlinear. Pushover analyses are carried out to obtain capacity curves. Displacement demands were calculated according to Eurocode 8 and FEMA440 guidelines. Causes of building failures in recent earthquakes were examined using the results of this study. The results of the study showed that the URM building displays higher displacement and shear force demands that can be directly related to damage or collapse. On the other hand, the confined one exhibits relatively higher seismic resistance by indicating moderate damage. Moreover, effects of demand estimation approaches on performance assessment of URM buildings were compared. Deficiencies and possible solutions to improve the capacity of such buildings were discussed.

Key Words
capacity assessment; capacity spectrum; confined masonry; seismic performance; unreinforced masonry structures

Address
Huseyin Bilgin: Department of Civil Engineering, EPOKA University, Rruga Tirane, Km 12, 1032, Tirana, Albania
Ergys Huta: Albania Draht, Mucaj, Vore, Tirana, Albania

Abstract
The seismic vulnerability of Turkey is relatively high due to its active fault systems with potential to create destructive earthquakes. Thus, reducing the loss of life and property, the number of the earthquake-prone buildings and their retrofit requirements are considerably significant key issues under the scenario earthquakes. The street survey based rapid assessment (SSRA) method can be considered as a powerful tool to determine the seismic vulnerability of building stock of an earthquake-prone city/state. In this study, the seismic vulnerability of the building stock of the Kirikkale province in Turkey is aimed to be estimated adopting the street survey based rapid assessment method (SSRA). For this purpose, central 2074 existing reinforced concrete (R/C) buildings were structurally surveyed with rapid visual site screening and disadvantages such as, the existence of short-column, soft-story, heavy overhangs, pounding effect and local soil conditions were determined for obtaining the structural performance score of each. The results obtained from the study demonstrate that 11-25% of the surveyed buildings in the study region needs to be investigated through more advanced assessment methods. Besides, higher correlation between increasing story number and unsafe/safe building ratio is obtained for the buildings with soft-story parameter than that for those with heavy overhangs and short-column parameters. The conformity of the results of the current study with the previous documented cases of rapid assessment efforts in the recent earthquakes in Turkey shows that the SSRA method for the Kirikkale province performed well, and thus this methodology can be reliably used for similar settlement areas.

Key Words
rapid assessment, seismic vulnerability, building stock, reinforced concrete structures, structural performance score

Address
Yetis Bulent Sonmezer: Department of Civil Engineering, Faculty of Engineering, Kirikkale University, 71450 Kirikkale, Turkey
Selcuk Bas: Department of Civil Engineering, Faculty of Engineering, Bartin University, 74100 Bartin, Turkey
Sami Oguzhan Akbas: Department of Civil Engineering, Faculty of Engineering, Gazi University, 06500 Ankara, Turkey


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