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CONTENTS
Volume 25, Number 1, January 2020
 

Abstract
This study presents applications of the multivariate adaptive regression splines (MARS) method for predicting the ultimate loading carrying capacity (Nu) of rectangular concrete-filled steel tubular (CFST) columns subjected to eccentric loading. A database containing 141 experimental data was collected from available literature to develop the MARS model with a total of seven variables that covered various geometrical and material properties including the width of rectangular steel tube (B), the depth of rectangular steel tube (H), the wall thickness of steel tube (t), the length of column (L), cylinder compressive strength of concrete (f\'c), yield strength of steel (fy), and the load eccentricity (e). The proposed model is a combination of the MARS algorithm and the grid search cross-validation technique (abbreviated here as GS-MARS) in order to determine MARS\' parameters. A new explicit formulation was derived from MARS for the mentioned input variables. The GS-MARS estimation accuracy was compared with four available mathematical methods presented in the current design codes, including AISC, ACI-318, AS, and Eurocode 4. The results in terms of criteria indices indicated that the MARS model was much better than the available formulae.

Key Words
concrete-filled steel tube; multivariate adaptive regression spline; eccentric loading; ultimate load-carrying capacity; CFST column; MARS

Address
Nguyen-Vu Luat, Jaehong Lee, Kihak Lee: Department of Architectural Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea
Do Hyung Lee: Department of Civil Environmental and Railroad Engineering, Paichai University, 155-40 Baejae-ro, Seo-Gu, Daejeon 35345, South Korea

Abstract
During the past decades, the application of acoustic emission techniques (AET) through the diagnosis and monitoring of the fracture process in materials has been attracting considerable attention. AET proved to be operative among the other non-destructive testing methods for various reasons including their practicality and cost-effectiveness. Concrete and rock structures often demand thorough and real-time assessment to predict and prevent their damage nucleation and evolution. This paper presents an overview of the work carried out on the use of AE as a monitoring technique to form a comprehensive insight into its potential application in brittle materials. Reported properties in this study are crack growth behavior, localization, damage evolution, dynamic character and structures monitoring. This literature review provides practicing engineers and researchers with the main AE procedures to follow when examining the possibility of failure in civil/resource structures that rely on brittle materials.

Key Words
fracture process; acoustic emission; brittleness; damage evolution; failure modes

Address
Hamid Reza Nejati, Amin Nazerigivi, Mehrdad Imani: Rock Mechanics Division, School of Engineering, Tarbiat Modares University, Tehran, Iran
Ali Karrech: School of Civil, Environmental and Mining Engineering, Faculty of Engineering, Computing and Mathematics, The University of Western Australia, Australia

Abstract
This work presents a numerical modeling procedure to simulate the refractory concrete lining in fluid catalytic cracking units of oil refineries. The model includes the simulation of the anchors that reinforce the contact between the refractory concrete and the steel casing. For this purpose, the constitutive relations of an interface finite element are set to values that represent the homogenized behavior of the anchored interface. The parameters of this constitutive relation can be obtained by experimental tests. The model includes also multi-surface plasticity, in order to represent the behavior of the refractory concrete lining. Since the complexity of real case applications leads to high computational costs, the models presented here were implemented in a high-performance parallelized finite element platform. A case study representing a riser similar to the ones used by the refinery industry demonstrates the potential of the model.

Key Words
numerical modeling; refractory concrete; concrete-steel interfaces

Address
Ana B.C.G. Silva, Henrique C.C. Andrade, Eduardo M.R. Fairbairn, Jose C.F. Telles, Fernando L.B. Ribeiro, Romildo D. Toledo-Filho: Civil Engineering Department, Federal University of Rio de Janeiro, Centro de Tecnologia, Cidade Universitária, CEP 21945-970, Rio de Janeiro, RJ, Brazil
Jorivaldo Medeiros: Engineering Department, PETROBRAS, Centro, CEP 20231-030, Rio de Janeiro, RJ, Brazil

Abstract
This work investigates a new type of quasi-3D hyperbolic shear deformation theory is proposed in this study to discuss the statics and free vibration of functionally graded porous plates resting on elastic foundations. Material properties of porous FG plate are defined by rule of the mixture with an additional term of porosity in the through-thickness direction. By including indeterminate integral variables, the number of unknowns and governing equations of the present theory is reduced, and therefore, it is easy to use. The present approach to plate theory takes into account both transverse shear and normal deformations and satisfies the boundary conditions of zero tensile stress on the plate surfaces. The equations of motion are derived from the Hamilton principle. Analytical solutions are obtained for a simply supported plate. Contrary to any other theory, the number of unknown functions involved in the displacement field is only five, as compared to six or more in the case of other shear and normal deformation theories. A comparison with the corresponding results is made to verify the accuracy and efficiency of the present theory. The influences of the porosity parameter, power-law index, aspect ratio, thickness ratio and the foundation parameters on bending and vibration of porous FG plate.

Key Words
static; free vibration; novel Quasi-3D plate theory; normal stress; porous FG; Kerr foundation

Address
Miloud Kaddari: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Abdelhakim Kaci: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Department of Civil Engineering and Hydraulics, University Dr. Taher Moulay of Saida, Algeria
Abdelmoumen Anis Bousahla: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Fouad Bourada: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Departement des Sciences et de la Technologie, Centre Universitaire de Tissemsilt, BP 38004 Ben Hamouda, Algeria
AbdeldjebbarTounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
E.A. Adda Bedia: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia
Mohammed A. Al-Osta: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
The premise for the study reflected in this article is the need to dispose of industrial waste, which is increasingly being used in the construction materials industry. Also, dynamically developing building industry demands attention of scientists and a direction of their works on improvement of the technology of carrying out construction works. Thus, the article is devoted to studying the influence of various chemical additives and fine fillers (industrial wastes) available in Kazakhstan on selfcompacting concrete (SCC) mixtures and its rheological, physical, and technical properties. According to the studies, revealed the most efficient type of fine-dispersed filler and the most optimal type of chemical additive to enable obtaining a high-quality SCC mixture based on local raw materials. As a result, the use of microsilica in comparison with other industrial wastes resulted in a conglomerate with high compressive strength of SCC at early terms of curing. In terms of economic efficiency and quality improvement, the results of study are of practical value for the manufacturers of ready-mixed concrete operating in Kazakhstan.

Key Words
self-compacting concrete; placeability; persistence; chemical additives; fine fillers from wastes

Address
Yelbek Utepov: Department of Civil Engineering, L.N. Gumilyov Eurasian National University, 2 Satpayev, Nur-Sultan 010000, Kazakhstan; NIISTROMPROJECT (LLP), 152/6 Radostovsia, office 109, 050000 Almaty, Kazakhstan
Daniyar Akhmetov, Ilnur Akhmatshaeva: NIISTROMPROJECT (LLP), 152/6 Radostovsia, office 109, 050000 Almaty, Kazakhstan

Abstract
Traditionally used analytical approach to predict the fatigue failure of reinforced concrete (RC) structure is generally conservative and has certain limitations. The nonlinear finite element method (FEM) offers less expensive solution for fatigue analysis with sufficient accuracy. However, the conventional implicit dynamic analysis is very expensive for high level computation. Whereas, an explicit dynamic analysis approach offers a computationally operative modelling to predict true responses of a structural element under periodic loading and might be perfectly matched to accomplish long life fatigue computations. Hence, this study simulates the fatigue behaviour of RC beams with finite element (FE) assemblage presenting a simplified explicit dynamic numerical solution to show computer aided fatigue behaviour of RC beam. A commercial FEM package, ABAQUS has been chosen for this complex modelling. The concrete has been modelled as a 8-node solid element providing competent compression hardening and tension stiffening. The steel reinforcements are simulated as two-node truss elements comprising elasto-plastic stress-strain behaviour. All the possible nonlinearities are duly incorporated. Time domain analysis has been adopted through an automatic Newmark-

Key Words
computer aided modelling; failure prediction; fatigue; cyclic loading; explicit dynamic; cracks; damage; reinforced concrete beam

Address
A.B.M. Saiful Islam: Department of Civil & Construction Engineering, Imam Abdulrahman Bin Faisal University, 31451, Dammam, Saudi Arabia

Abstract
The purpose of this paper is to provide an experimental and analytical study on the reinforced large diameter pretensioned high strength concrete (R-LDPHC) pile. R-LDPHC pile was reinforced with infilled concrete, longitudinal, and transverse rebar to increase the flexural and shear strength of conventional large diameter PHC (LDPHC) pile without changing dimension of the pile. To evaluate the shear and flexural strength enhancement effects of R-LDPHC piles compared with conventional LDPHC pile, a two-point loading tests were conducted under simple supported conditions. Nonlinear analysis on the basis of the conventional layered sectional approach was also performed to evaluate effects of infilled concrete and longitudinal rebar on the flexural strength of conventional LDPHC pile. Moreover, ultimate strength design method was adopted to estimate the effect of transverse rebar and infilled concrete on the shear strength of a pile. The analytical results were compared with the results of the bending and shear test. Test results showed that the flexural strength and shear strength of RLDPHC pile were increased by 2.3 times and 3.3 times compared to those of the conventional LDPHC pile, respectively. From the analytical study, it was found that the flexural strength and shear strength of R-LDPHC pile can be predicted by the analytical method by considering rebar and infilled concrete effects, and the average difference of flexural strength between experimental results and calculated result was 10.5% at the ultimate state.

Key Words
LDPHC pile; flexural strength; shear strength; ultimate strength design method

Address
Jin-Wook Bang: TongYang Construction Materials R&D Center, 2822-1, Gimpo-daero, Gyeonggi-do 10024, Republic of Korea
Bang-Yeon Lee: School of Architecture, Chonnam National University, 77, Yongbong-ro, Buk-gu, Gwangju 61186, Republic of Korea
Yun-Yong Kim: Department of Civil Engineering, Chungnam National University, 99, Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea

Abstract
The use of fly ash in modern-day concrete technology aiming sustainable constructions is on rapid rise. Fly ash, a spinoff from coal calcined thermal power plants with pozzolanic properties is used for cement replacement in concrete. Fly ash concrete is cost effective, which modifies and improves the fresh and hardened properties of concrete and additionally addresses the disposal and storage issues of fly ash. Soft computing techniques have gained attention in the civil engineering field which addresses the drawbacks of classical experimental and computational methods of determining the concrete compressive strength with varying percentages of fly ash. In this study, models based on soft computing techniques employed for the prediction of the compressive strengths of fly ash concrete are collected from literature. They are classified in a categorical way of concrete strengths such as control concrete, high strength concrete, high performance concrete, self-compacting concrete, and other concretes pertaining to the soft computing techniques usage. The performance of models in terms of statistical measures such as mean square error, root mean square error, coefficient of correlation, etc. has shown that soft computing techniques have potential applications for predicting the fly ash concrete compressive strengths.

Key Words
concrete; fly ash; compressive strength; soft computing techniques

Address
Rajeshwari Ramachandra: Department of Civil Engineering, PES University, 100 feet Ring Road, Bengaluru-560040, India
Sukomal Mandal: Department of Civil Engineering, PES University, 100 feet Ring Road, Bengaluru-560040, India; CSIR-NIO, Dona Paula, Goa- 403004, India

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