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CONTENTS
Volume 17, Number 1, January 2016
 

Abstract
Final construction project cost is significantly determined by construction rate. The Industrialized Building System (IBS) was promoted to enhance the importance of prefabrication technology rather than conventional methods in construction. Ensuring the stability of a building constructed by using IBS is a challenging issue. Accordingly, the connections in a prefabricated building have a basic, natural, and essential role in providing the best continuity among the members of the building. Deficiencies of conventional precast connections were observed when precast buildings experience a large induced load, such as earthquakes and other disasters. Thus, researchers aim to determine the behavior of precast concrete structure with a specific type of connection. To clarify this problem, this study investigates the capacity behavior of precast concrete panel connections for industrial buildings with a new type of precast wall-to-wall connection (i.e., U-shaped steel channel connection). This capacity behavior is compared with the capacity behavior of precast concrete panel connections for industrial buildings that used a common approach (i.e., loop connection), which is subjected to monotonic loading as in-plane and out-of-plane loading by developing a finite element model. The principal stress distribution, deformation of concrete panels and welded wire mesh (BRC) reinforcements, plastic strain trend in the concrete panels and connections, and crack propagations are investigated for the aforementioned connection. Pushover analysis revealed that loop connections have significant defects in terms of strength for in-plane and out-of-plane loads at three translational degrees of freedom compared with the U-shaped steel channel connection.

Key Words
industrial building systems; precast concrete structures; wall connection; monotonic loading; pushover analysis; finite element analysis

Address
Ramin Vaghei, Farzad Hejazi, Hafez Taheri, Mohd Saleh Jaafar: Department of Civil Engineering, Faculty of Engineering, University Putra Malaysia, Malaysia
Abang Abdullah Abang Ali: Housing Research Centre, Faculty of Engineering, University Putra Malaysia, Malaysia

Abstract
Tension-stiffening is the contribution of concrete between the cracks to carry tensile stresses after cracking in Reinforced Concrete (RC) members. In this paper, a tension-stiffening model has been proposed for computationally efficient nonlinear analysis of RC flexural members subjected to service load. The proposed model has been embedded in a typical cracked span length beam element. The element is visualized to consist of at the most five zones (cracked or uncracked). Closed form expressions for flexibility and stiffness coefficients and end displacements have been obtained for the cracked span length beam element. Further, for use in everyday design, a hybrid analytical-numerical procedure has been developed for nonlinear analysis of RC flexural members using the proposed tension-stiffening model. The procedure yields deflections as well as redistributed bending moments. The proposed model (and developed procedure) has been validated by the comparison with experimental results reported elsewhere and also by comparison with the Finite Element Method (FEM) results. The procedure would lead to drastic reduction in computational time in case of large RC structures.

Key Words
cracking; finite element method; reinforced concrete; service load; tension stiffening

Address
K.A. Patel and A.K. Nagpal: Civil Engineering Department, Indian Institute of Technology Delhi, New Delhi 110016, India
Sandeep Chaudhary: Civil Engineering Department, Malaviya National Institute of Technology Jaipur, Jaipur 302017, India

Abstract
Currently, most of the investigations on chloride diffusion were based on the experiments and simulations concerning single cation type chlorides. Chloride diffusion associated with dual or multi cation types was rarely studied. In this paper, several groups of diffusion experiments are conducted using chloride solutions containing single, dual and multi cation types. A multi-ionic model is also proposed to simulate the chloride diffusion behavior in the experimental tests. The MATLAB software is used to numerically solve the nonlinear PDEs in the multi-ionic model. The experimental and simulated results show that the chloride diffusion behavior associated with different cation types is significantly different. When the single cation type chlorides are adopted, it is found that the bound rates of chloride ions combined with divalent cations are greater than those combined with monovalent cations. When the dual/multi cation type chlorides are adopted, the chloride bound rates increase with the Ca2+/Mg2+ percentage in the source solutions. This evidence indicates that the divalent cations would markedly enhance the chloride binding capacity and reduce the chloride diffusivity. Moreover, on the basis of the analysis, it is also found that the complicated cation types in source solutions are beneficial to reducing the chloride diffusivity.

Key Words
chloride diffusion; cation type; multi-ionic model; durability; concrete

Address
Zijian Song, Linhua Jiang and Ziming Zhang:College of Mechanics and Materials, Hohai University, 1 Xikang road, Nanjing, China

Abstract
Strengthening as well as correcting unsightly deflections of reinforced concrete (RC) beam may be accomplished by retrofitting. An innovative way to do this retrofitting that is proposed in this study utilizes turnbuckle to apply external post-tensioning. This Turnbuckle External Post-Tensioning (T-EPT) was experimentally proven to improve the serviceability and load carrying capacity of reinforced concrete beams. The T-EPT system comprises a braced steel frame and a turnbuckle mechanism to provide the prestressing force. To further develop the T-EPT, this research aims to develop a numerical scheme to analyze the structural performance of reinforced concrete beams with this kind of retrofitting. The fiber method analysis was used as the numerical scheme. The fiber method is a simplified finite element method that is used in this study to predict the elastic and inelastic behavior of a reinforced concrete beam. With this, parametric study was conducted so that the effective setup of doing the T-EPT retrofitting may be determined. Different T-EPT configurations were investigated and their effectiveness evaluated. Overall, the T-EPT was effective in improving the serviceability condition and load carrying capacity of reinforced concrete beam.

Key Words
fiber method, retrofitting, external post-tensioning, reinforced concrete beam, turnbuckle

Address
Bernardo A. Lejano: Department of Civil Engineering, De La Salle University, 2401 Taft Avenue, Manila, Philippines

Abstract
This paper deals with the reliability analysis of design formulations derived for predicting the punching shear capacity of FRP-reinforced two-way slabs. Firstly, a new design code formulation was derived by means of gene expression programming. This formulation differs from the existing ones as the slab length (L) was introduced in the equation. Next, the proposed formulation was tested for its generalization capability by a parametric study. Then, the stochastic analyses of derived and existing formulations were performed by Monte Carlo simulation. Finally, the reliability analyses of these equations were carried out based on the results of stochastic analysis and the ultimate state function of ASCE-7 and ACI-318 (2011). The results indicate that the prediction performance of new formulation is significantly higher as compared to available design equations and its reliability index is within acceptable limits.

Key Words
reliability; fiber reinforced polymer; RC slab; punching shear; structural safety; Monte Carlo simulation

Address
Ahmet Emin Kurtoğlu and Mahmut Bilgehan: Department of Civil Engineering, Zirve University, Kizilhisar Campus, 27260, Gaziantep, Turkey
Abdulkadir Çevik: Department of Civil Engineering, University of Gaziantep, 27310, Gaziantep, Turkey
Hasan M. Albegmprli: Technical College of Mosul, Foundation of Technical Education, Iraq

Abstract
Concrete is a heterogeneous material containing many weaknesses such as micro-cracks, pores and grain boundaries. The crack growth mechanism and failure behavior of concrete structures depend on the plastic deformation created by these weaknesses. In this article the non-linear finite element method is used to analyze the effect of presence of micro pore near a crack tip on both of the characteristics of crack tip plastic zone (its shape and size) and crack growth properties (such as crack growth length and crack initiation angle) under pure shear loading. The FE Code Franc2D/L is used to carry out these objectives. The effects of the crack-pore configurations and the spacing between micro pore and pre-excising crack tip on the characteristics of crack tip plastic zone and crack growth properties is highlighted. Based on the obtained results, the relative distance between the crack tip and the micro pore affects in very significant way the shape and the size of the crack tip plastic zone. Furthermore, crack growth length and crack initiation angle are mostly influenced by size and shape of plastic zone ahead of crack tip. Also the effects of pore decreaseon the crack tip by variation of pore situation from linear to perpendicular configuration. The critical position for a micro pore is in front of the crack tip.

Key Words
crack; micro pore; crack tip plastic zone; crack growth properties; FEM

Address
Hadi Haeri: Department of Mining Engineering, Bafgh Branch, Islamic Azad University, Bafgh, Iran
V. Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran

Abstract
Basalt is a type of volcanic rocks, grey to black in colour, contains less than 20% quartz,10% feldspathoid, and at least 65% of the feldspar of its volume. Basalt is considered an igneous rock with fine grains due to the rapid cooling of lava. Basaltic rocks have been widely used as aggregate for various purposes. The study presented in this paper was carried out on basalts that are widespread in the Madeira Island of Portugal and that comprise the major source of local crushed rock aggregates. This paper discusses an experimental programme that was carried out to study the effects of basaltic aggregate on the compressive strength and modulus of elasticity of concrete. For this purpose, cylinder specimens with 150

Key Words
basaltic aggregates; modulus of elasticity; commercial concrete; Eurocode 2

Address
Lino Maia: 1CONSTRUCT-LABEST, Faculty of Engineering (FEUP), University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
Farhad Aslani: Centre for Infrastructure Engineering and Safety, The University of New SouthWales, Sydney NSW2052, Australia


Abstract
The search for new structural systems capable of associating performance and safety requires deeper knowledge regarding the mechanical behavior of structures subject to different loading conditions. The Strut-and-Tie Model is commonly used to structurally designing some reinforced concrete elements and for the regions where geometrical modifications and stress concentrations are observed, called

Key Words
reinforced concrete; strut-and-tie; Abaqus; FEM; topological optimization

Address
Marcela Bruna Braga França, Marcelo Greco, Ricardo Morais Lanes: PROPEEs–Programa de Pós-Graduação em Engenharia de Estruturas da UFMG,Departamento de Engenharia de Estruturas, Universidade Federal de Minas Gerais, Av. Presidente Antônio Carlos, 6627 – Escola de Engenharia, 31270-901, Belo Horizonte, MG, Brasil
Valério Silva Almeida: EPUSP, Departamento de Engenharia de Estruturas e Fundação da Escola Politécnica,Universidade de São Paulo, Av. Prof. Mello Moraes, 2373,Butantã, 05508-030, São Paulo, SP, Brasil



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