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CONTENTS
Volume 17, Number 4, October 2019
 

Abstract
This paper presents the results of experimental and numerical studies conducted to investigate the behavior of exterior reinforced concrete beam column joints (BCJ) strengthened by using carbon fiber reinforced polymer (CFRP) sheets. Twelve reinforced concrete beam-column joints (BCJ) were tested in an experimental program by simulating the joints in seismically deficient old buildings. One group of BCJs was designed to fail in flexure at the BCJ interface, and the second group was designed to ensure joint shear failure. One specimen in each set was -retrofitted with CFRP sheet wrapped diagonally around the joint. The specimens were subjected to both monotonic and cyclic loading up to failure. 3D finite element simulation of the BCJs tested in the experimental program was carried out using the software ABAQUS, adopting the damage plasticity model (CDP) for concrete. The experimental results showed that retrofitting of the shear deficient, BCJs by CFRP sheets enhanced the strength and ductility and the failure mode changed from shear failure in the joints to the desired flexural failure in the beam segment. The FE simulation of BCJs showed a good agreement with the experimental results, which indicated that the CDP model could be used to model the problems of the monotonic and cyclic loading of beam-column reinforced concrete joints.

Key Words
exterior beam-column joint; retrofitting; monotonic test; cyclic test; CFRP; finite element model; damage plasticity model

Address
Abdulsamee M. Halahla: Civil Engineering Department, Fahad Bin Sultan University, Tabuk, 71454, Saudi Arabia
Muhammad K. Rahman: Center for Engineering Research, Research Institute, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia
Ali H. Al-Gadhib, Mohammed A. Al-Osta and Mohammed H. Baluch: Civil & Environmental Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia

Abstract
Masonry structures in the rural areas of Turkey often damaged due to moderate and big earthquakes. After every earthquake many scientists made field investigations on the earthquake performance of these structures and gave many useful information on construction techniques. However, the newly constructed masonry buildings are still not suitable for the suggested techniques, and they are still in danger against future earthquakes. Five moderate earthquakes of moment magnitude Mw 5.3, 5.3, 5.2, 5.0, and 5.3 struck the Ayvacik-Çanakkale District of Turkey between 6 and 12 February, 2017. More than a thousand of aftershocks were occurred and most of the masonry buildings in the villages nearby main shock epicenter were affected. The author went to the earthquake field and investigated the earthquake performances of masonry structures. This paper presents the recorded acceleration data, acceleration response spectra, and the seismological aspects of these earthquakes. Besides, case studies of damaged stone masonry buildings, and failure mechanisms are discussed with illustrated photos which were taken during the field investigations. It is concluded that the damaged masonry buildings were not designed and constructed properly in accordance with the Turkish building codes or similar specifications.

Key Words
Ayvacik-Çanakkale earthquake; field investigations; structural damage; stone masonry buildings, strong ground motions

Address
Ali Ural: Department of Civil Engineering, Aksaray University, 68100, Aksaray, Turkey

Abstract
Post-earthquake crisis management is a key capability for a country to be able to recover after a major seismic event. Instrumental seismic data transmitted and processed in a very short time can contribute to better management of the emergency and can give insights on the earthquake`s impact on a specific area. Romania is a country with a high seismic hazard, mostly due to the Vrancea intermediate-depth earthquakes. The elastic acceleration response spectrum of a seismic motion provides important information on the level of maximum acceleration the buildings were subjected to. Based on new data analysis and knowledge advancements, the acceleration elastic response spectrum for horizontal ground components recommended by the Romanian seismic codes has been evolving over the last six decades. This study aims to propose a framework for post-earthquake warning based on code spectrum exceedances. A comprehensive background analysis was undertaken using strong motion data from previous earthquakes corroborated with observational damage, to prove the method`s applicability. Moreover, a case-study for two densely populated Romanian cities (Focsani and Bucharest) is presented, using data from a 5.5 MW earthquake (October 28, 2018) and considering the evolution of the three generations of code-based spectral levels for the two cities. Data recorded in free-field and in buildings were analyzed and has confirmed that no structural damage occurred within the two cities. For future strong seismic events, this tool can provide useful information on the effect of the earthquake on structures in the most exposed areas.

Key Words
post-earthquake warning; design codes; spectral acceleration; Vrancea earthquakes

Address
Stefan F. Balan, Bogdan F. Apostol and Anton Danet: National Institute for Earth Physics, 12 Calugareni Street, Magurele, Romania
Alexandru Tiganescu: National Institute for Earth Physics, 12 Calugareni Street, Magurele, Romania; Technical University of Civil Engineering, 122-124 Lacul Tei Avenue, Bucharest, Romania

Abstract
In this article, different frequently adopted modeling aspects of linear and nonlinear dynamic soil-structure interaction (SSI) are studied on a pile-supported integral abutment bridge structure using the open-source platform OpenSees (McKenna et al. 2000, Mazzoni et al. 2007, McKenna and Fenves 2008) for a 2D domain. Analyzed approaches are as follows: (i) free field input at the base of fixed base bridge; (ii) SSI input at the base of fixed base bridge; (iii) SSI model with two dimensional quadrilateral soil elements interacting with bridge and incident input motion propagating upwards at model bottom boundary (with and without considering the effect of abutment backfill response); (iv) simplified SSI model by idealizing the interaction between structural and soil elements through nonlinear springs (with and without considering the effect of abutment backfill response). Salient conclusions of this paper include: (i) free-field motions may differ significantly from those computed at the base of the bridge foundations, thus put a significant bias on the inertial component of SSI; (ii) conventional modeling of SSI through series of soil springs and dashpot system seems to stay on the safer side under dynamic conditions when one considers the seismic actions on the structure by considering a fully coupled SSI model; (iii) consideration of abutment-backfill in the SSI model positively affects the general response of the bridge, as a result of large passive resistance that may develop behind the abutments.

Key Words
soil-structure interaction; numerical seismic analysis; integral bridge

Address
Sreya Dhar: Department of Civil Engineering, Indian Institute of Technology, Guwahati, 781039, India
Ali Güney Ozcebe: Department of Civil and Environmental Engineering, Politecnico di Milano, Milano, 20133, Italy; Department of Civil Engineering and Architecture, Università di Pavia, Pavia, 27100, Italy
Kaustubh Dasgupta: Department of Civil Engineering, Indian Institute of Technology, Guwahati, 781039, India
Lorenza Petrini: Department of Civil and Environmental Engineering, Politecnico di Milano, Milano, 20133, Italy
Roberto Paolucci: Department of Civil and Environmental Engineering, Politecnico di Milano, Milano, 20133, Italy

Abstract
On the basis that ground motions may arrive at a structure from any horizontal direction and that different directions of seismic incidence would result in different structural dynamic responses, this paper focuses on orienting the crucial seismic incidence of transmission tower-line systems based on the wavelet energy method. A typical transmission tower-line system is chosen as the case study, and two finite element (FE) models are established in ABAQUS, with and without consideration of the interaction between the transmission towers and the transmission lines. The mode combination frequency is defined by considering the influence of the higher-order modes of the structure. Subsequently, wavelet transformation is performed to obtain the total effective energy input and the effective energy input rate corresponding to the mode combination frequency to further judge the critical angle of seismic incidence by comparing these two performance indexes under different seismic incidence angles. To validate this approach, finite element history analysis (FEHA) is imposed on both FE models to generate comparative data, and good agreement is found. The results demonstrate that the wavelet energy method can forecast the critical angle of seismic incidence of a transmission tower-line system with adequate accuracy, avoiding time-consuming and cumbersome computer analysis. The proposed approach can be used in future seismic design of transmission tower-line systems.

Key Words
critical incidence angle; transmission tower-line system; wavelet transformation; effective energy input; effective energy input rate

Address
Li Tian, Xu Dong, Haiyang Pan: School of Civil Engineering, Shandong University, Jinan, Shandong Province 250061, China
Xiaoyu He: Zhejiang Provincial Institute of Communication Planning, Design and Research, Hangzhou, Zhejiang Province 310006, China

Abstract
This paper presents the experimental investigations on the seismic performance of a peculiar steel-concrete vertical hybrid structural system referred to as steel truss-RC tubular column hybrid structure. It is typically applied as the supporting structural system to house air-cooled condensers in thermal power plants (TPPs). Firstly, pseudo-dynamic tests (PDTs) are performed on a scaled substructure to investigate the seismic performance of this hybrid structure under different hazard levels. The deformation performance, deterioration behavior and energy dissipation characteristics are analyzed. Then, a cyclic loading test is conducted after the final loading case of PDTs to verify the ultimate seismic resistant capacity of this hybrid structure. Finally, the failure mechanism is discussed through mechanical analysis based on the test results. The research results indicate that the steel truss-RC tubular column hybrid structure is an anti-seismic structural system with single-fortification line. RC tubular columns are the main energy dissipated components. The truss-to-column connections are the structural weak parts. In general, it has good ductile performance to satisfy the seismic design requirements in high-intensity earthquake regions.

Key Words
steel-concrete hybrid structure; seismic performance; failure mechanism; pseudo-dynamic test; cyclic loading test

Address
Bo Wang, Tao Wu: School of Civil Engineering, Chang\'an University, Xi\'an 710061, China
Huijuan Dai: School of Civil Engineering, Xi\'an University of Science and Technology, Xi\'an 710054, China
Guoliang Bai: School of Civil Engineering, Xi\'an University of Architecture and Technology, Xi\'an 710055, China
Jian Wu: Shaanxi Key Laboratory of Safety and Durability of Concrete Structures, Xijing University, Xi\'an, 710123, China

Abstract
In this study, a numerical model of a shield tunnel with an assembled segmental lining was built. The seismic response of the segmental lining of the section of the shield tunnel in Line 1 of the Chengdu Metro is analyzed as it passes through the interface of sand-cobble and mudstone layers. To do so, the node-stress seismic-motion input method was used to input the seismic motion measured during the 2008 Wenchuan earthquake, and the joint openings and dislocations associated with the earthquake action were obtained. With reference to the Ethylene-Propylene-Diene Monomer (EPDM) sealing gaskets used in the shield tunnels in the Chengdu Metro, numerical simulation was applied to analyze the contact pressure along the seepage paths and the waterproof property under different joint openings and dislocations. A laboratory test on the elastic sealing gasket was also conducted to study its waterproof property. The test results accord well with the numerical results and the occurrence of water seepage in the section of the shield tunnel in Line 1 of the Chengdu Metro during the 2008 Wenchuan earthquake was verified. These research results demonstrate the deformation of segmental joint under earthquake, also demonstrate the relationship between segmental joint deformation and waterproof property.

Key Words
segmental lining; node-stress seismic-motion input method; joint deformation; elastic sealing gasket; waterproof property

Address
Qixiang Yan: Key Laboratory of Transportation Tunnel Engineering, Southwest Jiaotong University, Ministry of Education, Chengdu 610031, China
Rui Bao: Beijing Urban Construction Design & Development Group Co., Ltd., Beijing 100037, China
Hang Chen: Sichuan Highway Planning, Survey, Design and Research Institute Co., Ltd., Chengdu 610041, China
Binjia Li: Key Laboratory of Transportation Tunnel Engineering, Southwest Jiaotong University, Ministry of Education, Chengdu 610031, China
Wenyu Chen: Key Laboratory of Transportation Tunnel Engineering, Southwest Jiaotong University, Ministry of Education, Chengdu 610031, China
Yongwen Dai: China Water Conservancy and Hydropower Seventh Engineering Bureau Co., Ltd., Chengdu 610213, China
Hongyuan Zhou: China Water Conservancy and Hydropower Seventh Engineering Bureau Co., Ltd., Chengdu 610213, China

Abstract
The most effective passive vibration control and seismic resistance options in a reinforced concrete (RC) high-rise building (HRB) are the base isolation and the tuned mass damper (TMD) system. Many options, which may be suitable or not for different soil types, with different types of bearing systems, like rubber isolator, friction pendulum isolator and tension/compression isolator, are investigated to resist the base straining actions under five different earthquakes. TMD resists the seismic response, as a control system, by reducing top displacement or the total movement of the structure. Base isolation and TMDs work under seismic load in a different way, so the combination between base isolation and TMDs will reduce the harmful effect of the earthquakes in an effective and systematic way. In this paper, a comprehensive study of the combination of TMDs with three different base-isolator types for three different soil types and under five different earthquakes is conducted. The seismic response results under five different earthquakes of the studied nine RC HRB models (depicted by the top displacement, base shear force and base bending moment) are compared to show the most suitable hybrid passive vibration control system for three different soil types.

Key Words
base isolation; rubber isolator; friction pendulum isolator; tension/compression isolator; tuned mass damper (TMD); high-rise building (HRB); soil-structure interaction (SSI); seismic response; vibration control

Address
Denise-Penelope N. Kontoni: Department of Civil Engineering, University of the Peloponnese, 1 M. Alexandrou Str., Koukouli, GR-26334 Patras, Greece
Ahmed Abdelraheem Farghaly: Department of Civil and Architectural Constructions, Faculty of Industrial Education, Sohag University, Sohag 82524, Egypt

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