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CONTENTS
Volume 18, Number 1, July 2016
 

Abstract
In this study, an Artificial Neural Network (ANN) and Adaptive Network-based Fuzzy Inference Systems (ANFIS) prediction models for flexural strength of the cement mortars have been developed. For purpose of constructing this models, 12 different mixes with 144 specimens of the 2, 7, 28 and 90 days flexural strength experimental results of cement mortars containing pure Portland cement (PC), blast furnace slag (BFS), waste tire rubber powder (WTRP) and BFS+WTRP used in training and testing for ANN and ANFIS were gathered from the standard cement tests. The data used in the ANN and ANFIS models are arranged in a format of four input parameters that cover the Portland cement, BFS, WTRP and age of samples and an output parameter which is flexural strength of cement mortars. The ANN and ANFIS models have produced notable excellent outputs with higher coefficients of determination of R2, RMS and MAPE. For the testing of dataset, the R2, RMS and MAPE values for the ANN model were 0.9892, 0.1715 and 0.0212, respectively. Furthermore, the R2, RMS and MAPE values for the ANFIS model were 0.9831, 0.1947 and 0.0270, respectively. As a result, in the models, the training and testing results indicated that experimental data can be estimated to a superior close extent by the ANN and ANFIS models.

Key Words
ANN; ANFIS; blast furnace slag; waste tire rubber powder; flexural strength

Address
Eyyup Gulbandilar: Department of Computer Engineering, Faculty of Engineering and Architecture, Eskisehir Osmangazi University, Eskisehir, Turkeyand Yilmaz Kocak
Yilmaz Kocak: Department of Construction, Kutahya Vocational School of Technical Sciences, Dumlupinar University, Kutahya, Turkey

Abstract
This paper compares the arc-length and explicit dynamic solution methods for nonlinear finite element analysis of prestressed concrete members subjected to monotonically increasing loads. The investigations have been conducted using an L-shaped, prestressed concrete spandrel beam, selected as a highly nonlinear problem from the literature to give insight into the advantages and disadvantages of these two solution methods. Convergence problems, computational effort, and quality of the results were investigated using the commercial finite element package ABAQUS. The work in this paper demonstrates that a static analysis procedure, based on the arc-length method, provides more accurate results if it is able to converge on the solution. However, it experiences convergence problems depending upon the choice of mesh configuration and the selection of concrete post-cracking response parameters. The explicit dynamic solution procedure appears to be more robust than the arc-length method in the sense that it provides acceptable solutions in cases when the arc-length approach fails, however solution accuracy may be slightly lower and computational effort may be significantly larger. Furthermore, prestressing forces must be introduced into the finite element model in different ways for the explicit dynamic and arc-length solution procedures.

Key Words
finite element analysis; prestressed; concrete; cracking; tension stiffening; arc-length method; riks method; explicit dynamic method

Address
Bulent Mercan: 2H Offshore Inc., 15990 N Barkers Landing #200, Houston, TX 77079, USA
Henryk K. Stolarski and Arturo E. Schultz: Department of Civil, Environmental, and Geo-Engineering, Univ. of Minnesota, 500 Pillsbury Drive SE Minneapolis, MN 55455, USA

Abstract
This paper considers the tensile strength of concrete samples in direct, CTT, modified tension, splitting and ring tests using both of the experimental tests and numerical simulation (particle flow code 2D). It determined that which one of indirect tensile strength is close to direct tensile strength. Initially calibration of PFC was undertaken with respect to the data obtained from Brazilian laboratory tests to ensure the conformity of the simulated numerical models response. Furthermore, validation of the simulated models in four introduced tests was also cross checked with the results from experimental tests. By using numerical testing, the failure process was visually observed and failure patterns were watched to be reasonable in accordance with experimental results. Discrete element simulations demonstrated that the macro fractures in models are caused by microscopic tensile breakages on large numbers of bonded discs. Tensile strength of concrete in direct test was less than other tests results. Tensile strength resulted from modified tension test was close to direct test results. So modified tension test can be a proper test for determination of tensile strength of concrete in absence of direct test. Other advantages shown by modified tension tests are: (1) sample preparation is easy and (2) the use of a simple conventional compression press controlled by displacement compared with complicate device in other tests.

Key Words
tensile strength; direct test; CTT test; modified test; splitting test and ring test

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

Abstract
In this study, an investigation is made from the statics and economic aspects of the possibility of using the composite material ferrocement on the surfaces of squat cylindrical grain silos. For this purpose, the geometry of two model silos, each of height 5 m and diameter 5 m and 12.5 m, was designed. Five different reinforced plates of 10 and 20 mm thickness were produced to research the most suitable ferrocement plates to be used on the surface of these silos. Most durable reinforcement type for covering the silo surface was determined by pressure and bending tests. Grade 30 and Grade 55 steel plates were also considered for use in covering steel-coated silos. In the statics analysis performed with SAP2000, the least plate thicknesses needed for silos surfaced with Grade 30 and Grade 55 steel were found to be 6.20 mm and 4.70 mm respectively for silos of diameter 5 m, and 6.70 mm and 5.00 mm for silos of diameter 12.5 m. In the economic analysis, it was found that 20 mm thick Type 4 (with a wire diameter of 0.30 mm and a mesh aperture of 2 mm x 2 mm square type) reinforced ferrocement surfacing material was 5.6-6.1 times more economical than Grade 30 steel surfacing material and 4.4-4.7 times more economical than using Grade 55 steel. These results show that ferrocement can be used in place of steel from the point of view both of statics and economy.

Key Words
ferrocement; silo; structural analysis

Address
Kivanc Topcuoglu: Department of Construction, Mugla Vocational School Muglasitki Kocman University, Mugla, Turkey
Halil Baki Unal: Department of Agricultural Structures and Irrigation,Faculty of Agriculture, Ege University,İzmir,Turkey


Abstract
Performance-based remaining life assessment of reinforced concrete bridge girders, subject to chloride-induced corrosion of reinforcement, is addressed in this paper. Towards this, a methodology that takes into consideration the human judgmental aspects in expert decision making regarding condition state assessment is proposed. The condition of the bridge girder is specified by the assignment of a condition state from a set of predefined condition states, considering both serviceability- and ultimate- limit states, and, the performance of the bridge girder is described using performability measure. A non-homogeneous Markov chain is used for modelling the stochastic evolution of condition state of the bridge girder with time. The thinking process of the expert in condition state assessment is modelled within a probabilistic framework using Brunswikian theory and probabilistic mental models. The remaining life is determined as the time over which the performance of the girder is above the required performance level. The usefulness of the methodology is illustrated through the remaining life assessment of a reinforced concrete T-beam bridge girder.

Key Words
reinforced concrete; chloride-induced corrosion; remaining life; performability; nonhomogeneous Markov chain; Brunswikian theory

Address
M.B. Anoop and K. Balaji Rao: CSIR-Structural engineering research centre, CSIR Campus, Chennai 600113, India
B.K. Raghuprasad: Department of civil engineering, Indian institute of science, Bangalore 560012, India

Abstract
Since the preservation of monuments is very important to human societies, different methods are required to preserve historic structures. In this paper, 3D model of arch stone bridge at Pont Saint Martin, Aosta, Italy, was simulated by 1660 integrated separate stones using ABAQUS

Key Words
historical stone bridge; spandrel walls; finite element simulation; ABAQUS; modeling; dynamic loads; earthquake resistant structure

Address
Mahdi Mahdikhani: Civil Engineering Department, Imam Khomeini International University, Norouzian Boulevard, Qazvin, Iran
Melika Naderi: Dipartimento di Architettura Urbanistica Ingegneria delle Costruzioni, Politecnico di Milano,
Via Andrea Maria Ampère, 2, 20133 Milano, Italy
Mehdi Zekavati: Civil Engineering Department, Qazvin Branch, Islamic Azad University, Nokhbegan Boulevard, Qazvin, Iran

Abstract
Extensive experimental studies on remarkable mechanical properties Polypropylene Fibre Reinforced Self-compacting Concrete (PFRSCC) have been executed, including different fibre volume fractions of Polypropylene fibers (0.25%, 0.5%, 0.75%, and 1%) and different water to cement ratios (0.21, 0.34, 0.38, and 0.41). The experimental program was carried out by using two hundred and sixteen specimens to obtain the impact resistance and mechanical properties of PFRSCC materials, considering compressive strength, splitting tensile strength, and flexural strength. Statistical and analytical studies have been mainly focused on experimental data to correlate of mechanical properties of PFRSCC materials. Statistical results revealed that compressive, splitting tensile, and flexural strengths as well as impact resistance follow the normal distribution. Moreover, to correlate mechanical properties based on acquired test results, linear and nonlinear equations were developed among mechanical properties and impact resistance of PFRSCC materials.

Key Words
mechanical properties; Polypropylene Fibre Reinforced Self-compacting Concrete (PFRSCC); statistical data analysis; probability distribution; regression analysis

Address
M. Mastali: ISISE, Department of Civil Eng., School of Eng., University of Minho, Campus de Azurém, 4800-058
Guimarães, Portugal
A. Dalvand: Department of Eng., Lorestan University, Khorramabad, Iran
M. Fakharifar: Department of Civil, Architectural and Environmental Eng., Missouri University of Science and Technology, Rolla, MO 65409, United States

Abstract
Since the concrete strength around the reinforcement rebar affects the tension stiffening, the tension stiffening effect of ultra high performance concrete on the concrete members reinforced by steel rebar is examined by testing the specimens with circular cross section with the length 850 mm reinforced by a steel rebar at the center of a specimen\'s cross section in this research. Conducting a tensile test on the specimens, the cracking behavior is evaluated and a curve with an exponential descending branch is obtained to explain the post-cracking zone. In addition, this paper proposes an equation for this branch and parameters of equation is obtained based on the ratio of cover thickness to rebar diameter (c/d) and reinforcement percentage (

Key Words
Ultra High Performance Concrete (UHPC); reinforcement; tension stiffening; reinforced concrete member; crack

Address
H.A. Rahdar and M. Ghalehnovi: Civil Engineering Department, Faculty of Engineering, Ferdowsi University Of Mashhad, Mashhad, Iran


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