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CONTENTS
Volume 16, Number 1, July 2015
 

Abstract
The proposed techniques to strengthen concrete members such as steel plates, polymers or concrete have important deficiencies in adherence and durability. The use of UHPFC plates can overtake effectively these problems. In this paper, the possibility of using UHPFC to strengthen RC beams under torsion is investigated. Four specimens of concrete beams reinforced with longitudinal bars only were tested under pure torsion. One of the beams was considered as the baseline specimen, while the others were strengthened by ultra-high-performance fiber concrete (UHPFC) on two, three, and four sides.Finite element analysis was conducted in tandem with experimental work. Results showed that UHPFC enhances the strength, ductility, and toughness of concrete beams under torsional load, and that finite element analysis is in good agreement with the experimental data.

Key Words
reinforced concrete; torsion; finite element; strengthen; UHPFC

Address
Thaer Jasim Mohammed : School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus,14300 Nibong Tebal, Pulau Pinang, Malaysia
Thaer Jasim Mohammed, B.H. Abu Bakar, N. Muhamad Bunnori and Omer Farouk Ibraheem : Middle Technical University, Institute of Technology, Baghdad, Iraq


Abstract
In this study, linear and non-linear response of a masonry wall that includes an opening was presented. The masonry wall was modeled with two-dimensional finite elements. Smeared crack model that includes the strain softening behavior was selected to the masonry wall material. For the numerical application, linear and non-linear analyses of the masonry wall were carried out using east-west and vertical components of the 1992 Erzincan and 2003 Bingöl earthquake acceleration records. Linear and non-linear solutions were compared each other. The displacement and stress results at the selected points of the masonry wall and crack propagation in the masonry wall were presented for both earthquake acceleration records.

Key Words
masonry wall; non-linear analysis; smeared crack model

Address
Erkut Sayin and Yusuf Calayir : Department of Civil Engineering, Firat University, Elazig, Turkey

Abstract
Alkali aggregate reaction affects numerous civil engineering structures and causes irreversible expansion and cracking. This work aims at developing model to predict the potential expansion of concrete containing alkali-reactive aggregates. First, the paper presents the experimental results concerning the influence of particle size of an alkali-reactive aggregate on mortar expansion studied at 0.15–0.80 mm, 1.25–2.50 mm and 2.5–5.0 mm size fractions and gives data necessary for model development. Results show that no expansion was measured on the mortars using small particles(0.15-0.80 mm) while the particles (1.25–2.50 mm) gave the largest expansions. Finally, model is proposed to simulate the experimental results by studying correlations between the measured expansions and the size of aggregates and to calculate the thickness of the porous zone necessary to take again all the volume of the gel created by this chemical reaction.

Key Words
simulation; alkali aggregate reaction; expansion; model; particle size

Address
Sekrane Nawal Zahira and Asroun Aissa : Department of Civil Engineering, Djillali Liabes University, Civil Engineering and Environment Laboratory, Sidi Bel Abbés 22000, Algeria

Abstract
It is hard to guarantee the strict synchronization of all the jacking-up points in the integral jacking of a large-span continuous box girder bridge. This paper took the Hengliaojing Bridge as background, which need jacking up as an object with 295m length and more than 10,000tons weight, adopted 3D software to calculate the unsynchronized jacking-up working conditions, and studied the relationships between the unsynchronized vertical difference and the girder\'s deformation behaviour. The aim is to verify the maximum value of the unsynchronized vertical difference, and guide the construction and ensure safety. The monitoring system with its contents is introduced corresponding to the analysis. The results of the deck relative elevations prove that it is difficult to avoid the deck torsional deformation for jacking different; especially the side span shows more deformations for its smaller stiffness. The maximum difference is smaller than the limited value with acceptable stresses in the sections. The jacking heights of the pier in each construction step are controlled regularly according to the design. The shifting of the whole bridge in longitudinal direction is smaller than in transverse direction. The several beginning steps are the key to adjust their support reactions. This study is one parts of the fundamental research for the code \"Technical specification for bridge jacking-up and reposition of China\". The whole synchronous jacking project of the main bridge set a world record by the World Record Association for the whole bridge jacking project with the longest span of the world.

Key Words
continuous box girder bridge; integral jacking; synchronized jacking; jacking control; construction monitoring

Address
Fangyuan Li and Peifeng Wu : Department of Bridge Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China
Xinfei Yan : Shanghai Urban Construction Design & Research Institute, Shanghai 200125, China

Abstract
This article presents a computing procedure developed to predict the torsional strength of axially restrained reinforced concrete beams. This computing procedure is based on a modification of the Variable Angle Truss Model to accont for the influence of the longitudinal compressive stress state due to the axial restraint conditions provided by the connections of the beams to other structural elements. Theoretical predictions from the proposed model are compared with some experimental results available in the literature and also with some numerical results from a three-dimensional nonlinear finite element analysis. It is shown that the proposed computing procedure gives reliable predictions for the ultimate behaviour, namely the torsional strength, of axially restrained reinforced concrete beams under torsion.

Key Words
reinforced concrete; beams; torsion; axial restraint; truss-model; finite element analysis

Address
Luis F.A. Bernardo, Catia S.B. Taborda and Jorge M.A. Andrade : Department of Civil Engineering and Architecture, Centre of Materials and Building Technologies (C-made), University of Beira Interior, Covilha, Portugal

Abstract
In this study, structural vulnerability of reinforced concrete moment resisting frames(RC-MRFs) by considering the Iran–specific characteristics is investigated to manage the earthquake risk in terms of multicomponent seismic excitations. Low and medium rise RC-MRFs, which constitute approximately 80-90% of the total buildings stock in Iran, are focused in this fragility–based assessment. The seismic design of 3-12 story RC-MRFs are carried out according to the Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard No. 2800), and the analytical models are formed accordingly in open source nonlinear platforms. Frame structures are categorized in three subclasses according to the specific characteristics of construction practice and the observed seismic performance after major earthquakes in Iran. Both far and near fields\' ground motions have been considered in the fragility estimation. An optimal intensity measure (IM) called Sa, avg and beta probability distribution were used to obtain reliable fragility–based database for earthquake damage and loss estimation of RC buildings stock in urban areas of Iran. Nonlinear incremental dynamic analyses by means of lumped-parameter based structural models have been simulated and performed to extract the fragility curves. Approximate confidence bounds are developed to represent the epistemic uncertainties inherent in the fragility estimations. Consequently, it\'s shown that including vertical ground motion in the analysis is highly recommended for reliable seismic assessment of RC buildings.

Key Words
RC-MRFs; fragility curve; vertical seismic excitations; NL platforms; beta distribution

Address
Ehsan Noroozinejad Farsangi : SERC, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran
Abbas Ali Tasnimi : Department of Civil and Environmental Engineering, Tarbiat Modares University (TMU), Tehran, Iran
Babak Mansouri : ERMRC, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

Abstract
This paper describes the numerical calculation of elastic properties of a simulated microstructure of cement paste from very early age, when most previous models fail to give accurate results. The development of elastic properties of tricalcium silicate pastes was calculated by discretising a numerical resolution-free 3D vector microstructure to a regular cubic mesh. Due to the connections formed in the microstructure as an artefact of the meshing procedure, the simulated elastic moduli were found to be higher than expected. Furthermore, the percolation of the solids was found to occur even before hydration started. A procedure to remove these artefacts, on the basis of the information available in the vector microstructures was developed. After this correction, a better agreement of the experimental results with calculations was obtained between 20% and 40% hydration. However, percolation threshold was found to be delayed significantly. More realistic estimates of percolation threshold were obtained if either flocculation or a densification of calcium silicate hydrate with hydration was assumed.

Key Words
elastic properties; Ca3SiO5; microstructure; hydration; finite element analysis

Address
Huy Q. Do and Karen L. Scrivener : Laboratoire des Matériaux de Construction, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
Shashank Bishnoi : Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi, India

Abstract
A significant portion of residential areas of Turkey is located in active earthquake zones. In Turkey occurred major earthquakes in last twenty years, such as Erzincan (1992), Kocaeli and Düzce (1999), Bingöl (2003), Van (2011). These earthquakes have demonstrated that reinforced concrete (RC) buildings having horizontal and vertical irregularities are significantly damaged, which in turn most of them are collapsed. Architectural design and arrangement of load-bearing system have important effect on RC building since architectural design criteria in design process provide opportunity to make this type of buildings safer and economical under earthquake loads. This study aims to investigate comparatively the effects of weak story irregularity on earthquake behavior and rough construction costs of RC buildings by considering different soil-conditions given in the Turkish Earthquake Code. With this aim, Sta4-CAD program based on matrix displacement method is utilized. Considering that different story height and compressive strength of concrete, and infill walls or their locations are the variables, a set of structural models are developed to determine the effect of them on earthquake behavior and rough construction costs of RC buildings. In conclusion, some recommendations and results related to making RC buildings safer and more economical are presented by comparing results obtained from structural analyses.

Key Words
construction cost; weak story irregularity; soft story irregularity; earthquake behavior

Address
Şenol Gürsoy and Ramazan Öz : Department of Civil Engineering, Karabük University, 78050 Karabük, Turkey
Selçuk Baş : Department of Civil Engineering, Bartin University, 74100 Bartin, Turkey

Abstract
Due to the increase of the use of precast concrete structures in multistory buildings, this paper deals with the behavior of an specific type of beam-column connection used in this structural system. The connection is composed by concrete corbels, dowels and continuity bars passing through the column. The study was developed based on the experimental and numerical results. In the experimental analysis a full scale specimen was tested and for numerical study, a 3D computational model was created using a finite element analyze (FEA) software, called DIANA. The comparison of the results showed a satisfactory correlation between loading versus displacement curves.

Key Words
semi-rigid connection; beam-column connection; precast concrete structure; numerical analysis; finite element method

Address
Marcela N. Kataoka and Ana Lúcia H.C. El Debs : University of São Paulo, Engineering School of São Carlos, Structural Department, Av. Trabalhador Saocarlense, n.400, CEP:13566-580, Sao Carlos, SP, Brazil
Marceolo A. Ferreira : Federal University of São Carlos , Department of Civil Engineering, Rodovia Washington Luis, km 235, CEP: 13565-905, Monjolinho, São Carlos, SP, Brazil


Abstract
An experimental program has been carried out to investigate the effect of edge-slope on compressive strength of concrete specimens. In this study, effect of such slope was investigated by testing 100 standard cylinder specimens and 40 standard cubes. When molds are put on a slanted place, wet concrete starts to flow through the open end of mold. It keeps flowing until it reaches to a parallel surface with the place over which it was placed. That creates a sloped surface over the loading area. Experimental results revealed significant relationships between failure loads and slope of loading surface for cylinders. Angled cracks occurred in sloped cylinder specimens. Tension cracks occurred in cube specimens. Fracture mechanisms were also evaluated by using finite element analyses approach. Experiments yielded an exponential curve with bandwidth for cylinders. Average value of curve is between slope and compressive strength. Inclination is much effective parameter for cylinders than cubes.

Key Words
concrete; high strength concrete; compressive strength; slope; cylinder specimen

Address
Selçuk Emre Görkem : Erciyes University, Biosystems Engineering Department, 38038 Kayseri, Turkey


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