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CONTENTS
Volume 18, Number 3, September 2016
 

Abstract
Current codes recommend large amounts of shear reinforcement for reinforced concrete beamcolumn joints that causes significant bar congestion. Increase in congestion of shear reinforcement in joint core (connection zone), leads to increase accomplishment problems. The congestion may also lead to diameter limitations on the beam bars relative to the joint dimensions. Using double headed studs instead of conventional closed hoops in reinforced concrete beam-column joints reduces congestion and ensures easier assembly of the reinforcing cage. The purpose of this research is evaluating the efficiency of the proposed reinforcement. In this way, 10 groups of exterior beam-column joints are modeled. Each group includes 7 specimens by different reinforcing details in their joint core. All specimens are modeled by using of ABAQUS and analyzed subjected to cyclic loading. After verification of analytical modeling with an experimental specimen, 3D nonlinear specimens are modeled and analyzed. Then, the effect of amount and arrangement of headed studs on ductility, performance, ultimate strength and energy absorption has been studied. Based on the results, all joints reinforced with double headed studs represent better performance compared with the joints without shear transverse reinforcement in joints core. The behavior of the former is close to joints reinforced with closed hoops and cross ties according to the seismic design codes. By adjusting the arrangement of double-headed studs, the decrease in ductility, performance, ultimate momentresistant and energy absorption reduce to 2.61%, 0.90%, 0.90% and 1.66% respectively compared with the joints reinforced by closed hoops on the average. Since the use of headed studs reduces accomplishment problems, these amounts are negligible. Therefore, use of double-headed studs has proved to be a viable option for reinforcing exterior beam-column joints.

Key Words
exterior RC beam-column joint; ductility; performance; ultimate resistant moment; energy absorption

Address
Gholamreza Abdollahzadeh: Faculty of Civil Engineering, Babol University of Technology, Babol, Iran

Saeed Eilbeigi Ghalani: Department of Civil Engineering, Shomal University, Amol, Iran

Abstract
In this study, both two- and three-dimensional (2D and 3D) finite-volume-based models were developed to analyze the heat transfer mechanisms through the porous structures of cellular concretes under steady-state heat transfer conditions and to investigate the differences between the 2D and 3D modeling results. The 2D and 3D reconstructed pore networks were generated from the microstructural information measured by 3D images captured by X-ray computerized tomography (X-CT). The computed effective thermal conductivities based on the 2D and 3D calculations performed on the reconstructed porous structures were found to be nearly identical to those evaluated from the 2D cross-sectional images and the 3D X-CT images, respectively. In addition, the 3D computed effective thermal conductivity was found to agree better with the measured values, in comparison with the 2D reconstruction and real cross-sectional images. Finally, the thermal conductivities computed for different reconstructed porous 3D structures of cellular concretes were compared with those obtained from 2D computations performed on 2D reconstructed structures. This comparison revealed the differences between 2D and 3D image-based modeling. A correlation was thus derived between the results of the 3D and 2D models.

Key Words
Finite volume method (FVM); Effective thermal conductivity (ETC); image-based modeling; cellular concrete; Guarded hot-plate method (GHP)

Address
Wei She, Jinyang Jiang, Xiaoyu Cao and Yi Du: Jiangsu Key laboratory for Construction Materials, Southeast University, Nanjing, 211189, P.R. China

Guotang Zhao and Guotao Yang: China Railway Corporation, Beijing 100844, China

Abstract
To study the influence on fracture properties of reinforced concrete wedge splitting test specimens by the addition of reinforcement, and the restriction of steel bars on crack propagation, 7 groups reinforced concrete specimens of different reinforcement position and 1 group plain concrete specimens with the same size factors were designed and constructed for the tests. Based on the double-K fracture criterion and tests, fracture toughness calculation model which was suitable for reinforced concrete wedge splitting tensile specimens has been obtained. The results show that: the value of initial craking load Pini and unstable fracture load Pun decreases gradually with the distance of reinforcement away from specimens

Key Words
reinforced concrete; reinforcement position; fracture parameters; crack propagation

Address
HU Shaowei and HU Xin: Materials & Structural Engineering Department, Nanjing Hydraulic Research Institute,
34 Hujuguan, Nanjing, China

XU Aiqing and YIN Yangyang: College of Mechanics and Materials, Hohai University, 1 Xikang Road, Nanjing, China

Abstract
This paper reports the testing of concrete slabs reinforced with CFRP prestressed concrete prisms(PCP) on the flexural behavior. Four concrete slabs were tested, a reference slab reinforced with steel bars, and three slabs reinforced with CFRP prestressed concrete prisms (PCP). All slabs were made with dimensions of 600mm in width, 2200mm in length and 150 in depth. All concrete slabs reinforced with CFRP prestressed concrete prisms(PCP) exhibited CFRP bar rupture failure mode. It was shown that the application of the CFRP prestressed prisms can limit service load deflections and crack width, the increased level of prestress in the CFRP prestressed prism positively affected the maximum crack width. The deflection of concrete slabs reinforced with CFRP prestressed prisms decreased as prestress in the CFRP prestressed prism increased.

Key Words
test; slabs; CFRP; deflection; crack width

Address
Jiongfeng Liang: State Key Laboratory Breeding Base of Nuclear Resources and Environment, Fundamental Science on
Radioactive Geology and Exploration Technology Laboratory, Nanchang, P.R.China

Zeping Yang and Xinjun Chai: Faculty of Civil&Architecture Engineering, East China Institute of Technology, Nanchang, P.R.China

Deng Yu: College of Civil and Architecture Engineering, Guangxi University of Science and Technology, Liuzhou, P.R.China

Abstract
In this paper, a simple practical method is introduced in which a simple weight measurement of concrete and finite element numerical analysis are used to determine the moisture transfer coefficient of concrete with a satisfactory accuracy. Six concrete mixtures with different water-to-cementitious material (w/cm) ratios and two pozzolanic materials including silica fume and zeolite were examined to validate the proposed method. The comparison between the distribution of the moisture content obtained from the model and the one from the experimental data during both the wetting and drying process properly validated the performance of the method.With the proposed method, it was also shown that the concrete moisture transfer coefficient considerably depends on the pore water saturation degree. The use of pozzolanic materials and also lowering w/cm ratio increased the moisture transfer coefficient during the initial sorption, and then, it significantly decreased with an increase in the water saturation degree.

Key Words
moisture transfer coefficient; numerical modeling; silica fume; wetting and drying; zeolite

Address
Mehdi Nemati Chari and Mohammad Shekarchi: School of Civil Engineering, University of Tehran, Tehran, Iran

Pouria Ghods: Giatec Scientific Inc., Ottawa, Ontario, Canada

Masoud Moradian: School of Civil and Environmental Engineering, Oklahoma State University, Stillwater, Oklahoma, USA

Abstract
In this study, effects of impact loads on reinforced concrete (RC) plates are examined analytically. During examination of RC plates, they were exposed to impact loading with two different support conditions in three different sizes. RC plates in different support conditions were analyzed with Concrete Damage Plasticity Model (CDP) and reinforcing steel was modeled with Classical Metal Plasticity Model (CMP) by ABAQUS finite element software. After the analysis it is found that impact loads, displacements, energy absorption capacities and damage patterns are changed due to support conditions and plate sizes. Results that are obtained from RC plate experiments in literature under impact loads are found to be similar with the results of numerical analysis with CDP material models.

Key Words
impact load; RC plates; CDP; CMP, energy absorption capacity; support conditions

Address
Metin Husem and Suleyman I. Cosguna: Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey

Abstract
Recently laser scanning technologies become widely used in many areas of the modern economy. In the following paper authors show a potential spectrum of use Terrestrial Laser Scanning (TLS) in diagnostics of reinforced concrete elements. Based on modes of failure analysis of reinforcement concrete beam authors describe downsides and advantages of adaptation of terrestrial laser scanning to this purpose, moreover reveal under which condition this technology might be used. Research studies were conducted by Faculty of Civil and Environmental Engineering at Gdansk University of Technology. An experiment involved bending of reinforced concrete beam, the process was registered by the terrestrial laser scanner.Reinforced concrete beam was deliberately overloaded and eventually failed by shear.Whole failure process was tracing and recording by scanner Leica ScanStation C10 and verified by synchronous photographic registration supported by digital photogrammetry methods. Obtained data were post-processed in Leica Cyclone (dedicated software) and MeshLab (program on GPL license). The main goal of this paper is to prove the effectiveness of TLS in diagnostics of reinforced concrete elements. Authors propose few methods and procedures to virtually reconstruct failure process, measure geometry and assess a condition of structure.

Key Words
beam; cracks; deformation measurement; modes of failure; reinforced concrete; terrestrial laser scanning

Address
Artur Janowski, Krystyna Nagrodzka-Godycka, Jakub Szulwic and Patryk Zió

Abstract
Corrosion of embedded reinforcing bars is recognized as being the major cause of deterioration of reinforced concrete structures. With regard to maintenance strategies of concrete nuclear structures, the monitoring of cracking remains of primary importance. Recently, authors have developed a post-treatment technique to extract crack features from continuous computations. In this paper, such technique is applied to carry out a numerical analysis of an accelerated corrosion test. Obtained results allow highlighting specific propagation and failure mechanisms that characterize corrosion-induced cracking.

Key Words
discrete elements; finite elements; damage mechanics; multi-scale modelling; corrosion

Address
Benjamin Richard: CEA, DEN, DANS, DM2S, SEMT, Laboratoire d\'Etudes Mécaniques et Sismiques, F-91191 Gif sur Yvette, France

Marc Quiertant, Véronique Bouteiller and Lucas Adelaide: Université Paris-Est, IFSTTAR, Département Matériaux et structures, 14-20 boulevard Newton, 77447 Marne-la-Vallée Cedex 2, France

Arnaud Delaplace: Lafarge Centre de Recherche - Mécanique et Modes Constructifs, 95 Rue du Montmurier, 38291 Saint Quentin Fallavier, France

Frédéric Ragueneau: LMT/ENS Cachan/CNRS/Univ. Paris 6/PRES UniverSud 61 Avenue du PresidentWilson, 94230 Cachan, France

Christian Cremona: Bouygues Construction, Guyancourt, Île-de-France, France


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