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CONTENTS
Volume 58, Number 1, April10 2016
 

Abstract
Recently, the high-strength concrete is increasingly used in the construction of reinforced concrete structures due to its benefits, but this use is influenced negatively on the local ductility of structural elements. The objective of this study is the prediction of a new approach to evaluate the curvature ductility factor of high strength concrete beams according to Eurocode 2. After the presentation of the Constitutive laws of materials and the evaluation method of curvature ductility according to the Eurocode 2, we conduct a parametric study on the factors influencing the curvature ductility of inflected sections. The calibrating of the obtained results allows predicting a very simple approach for estimating the curvature ductility factor. The proposed formula allows to calculate the curvature ductility factor of high strength concrete beams directly according to the concrete strength fck, the yield strength of steel fyk and the ratio of tension and compression reinforcements p and p\' respectively, this proposed formula is validated by theoretical and experimental results of different researchers.

Key Words
Eurocode 2; beam; reinforcement; curvature ductility; high strength concrete

Address
Haytham Bouzid and Amar Kassoul: Department of Civil Engineering, Laboratory of Structures, Geotechnics and Risks (LSGR), Universite of Hassiba Benbouali of Chlef, Algeria BP 151, Hay Essalam, UHB Chlef, 02000, Algeria

Abstract
Many studies have been carried out to investigate the important factors in calculating the realistic entropy amount of water distribution networks, but none of them have considered both mechanical and hydraulic characteristics of the networks. Also, the entropy difference in various networks has not been calculated exactly. Therefore, this study suggested a modified entropy function to calculate the informational entropy of water distribution networks so that the order of demand nodes and entropy difference among various networks could be calculated by taking into account both mechanical and hydraulic characteristics of the network. This modification was performed through defining a coefficient in the entropy function as the amount of outflow at each node to all dissipated power in the network. Hence, a more realistic method for calculating entropy was presented by considering both mechanical and hydraulic characteristics of network while keeping simplicity. The efficiency of the suggested method was evaluated by calculating the entropy of some sample water networks using the modified function.

Key Words
network reliability; water distribution network; mechanical characteristics; informational entropy; energy dissipation

Address
Mostafa Ghanbari Kashani: Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
Mahmood Hosseini: International Institute of Earthquake Engineering and Seismology, (IIEES), Tehran, Iran
Armin Aziminejad: Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran

Abstract
Since the publication of ACI 318-02, the concrete capacity design (CCD) method has been used to determine the resistance of unreinforced concrete anchors. The regulation of steel-reinforced anchors was proposed in ACI 318-08. Until ACI 318-08, the shear resistance of concrete breakout for an unreinforced anchor during an earthquake was reduced to 75% of the static shear strength, but this reduction has been eliminated since ACI 318-11. In addition, the resistance of a hairpin-reinforced anchor was calculated using only the strength of the steel, and a regulation on the dynamic strength was not given for reinforced anchors. In this study, shaking table tests were performed to evaluate the dynamic shear strength of unreinforced and hairpin-reinforced cast-in-place (CIP) anchors during earthquakes. The anchors used in this study were 30 mm in diameter, with edge distances of 150 mm and embedment depths of 240 mm. The diameter of the hairpin steel was 10 mm. Shaking table tests were carried out on two specimens using the artificial earthquake, based on the United States Nuclear Regulatory Commission (US NRC)\'s Regulatory Guide 1.60, and the Northridge earthquake. The experimental results were compared to the current ACI 318 and ETAG 001 design codes.

Key Words
cast-in-place anchor; unreinforced anchor; hairpin-reinforced anchor; dynamic shear strength; shaking table tests

Address
Dong Hyun Kim and Yong Myung Park: Department of Civil Engineering, Pusan National University, Busan, 46241, Republic of Korea
Choong Hyun Kang: Seismic Simulation Test Center, Pusan National University, Busan, 46241, Republic of Korea
Jong Han Lee: Department of Civil Engineering, Daegu University, Gyeongbuk, 38453, Republic of Korea

Abstract
Laminated composite shells are commonly used in various engineering applications including aerospace and marine structures. In this paper, using semi-analytical finite strip method, the buckling behavior of laminated composite deep as well as thick shells of revolution under follower forces which remain normal to the shell is investigated. The stiffness caused by pressure is calculated for the follower forces subjected to external fibers in thick shells. The shell is divided into several closed strips with alignment of their nodal lines in the circumferential direction. The governing equations are derived based on first-order shear deformation theory which accounts for through thickness-shear flexibility. Displacements and rotations in the middle surface of shell are approximated by combining polynomial functions in the meridional direction as well as truncated Fourier series with an appropriate number of harmonic terms in the circumferential direction. The load stiffness matrix which accounts for variation of loads direction will be derived for each strip of the shell. Assembling of these matrices results in global load stiffness matrix which may be un-symmetric. Upon forming linear elastic stiffness matrix called constitutive stiffness matrix, geometric stiffness matrix and load stiffness matrix, the required elements for the second step analysis which is an eigenvalue problem are provided. In this study, different parameter effects are investigated including shell geometry, material properties, and different boundary conditions. Afterwards, the outcomes are compared with other researches. By considering the results of this article, it can be concluded that the deformation-dependent pressure assumption can entail to decrease the calculated buckling load in shells. This characteristic is studied for different examples.

Key Words
thick deep shell; laminated composite; follower force; finite strip method; buckling

Address
Majid Khayat, Davood Poorveis and Mona Hemmati: Department of Civil Engineering, Shahid Chamran University, Golestan Blvd., 61357831351, Ahvaz, Iran
Shapour Moradi: Department of Mechanical Engineering, Shahid Chamran University, Golestan Blvd., 61357831351, Ahvaz, Iran

Abstract
This article presents an experimental study on the effect of temperature and solid volume fraction of nanoparticles on the dynamic viscosity for the CuO/EG-water nanofluid. Nanoparticles with diameter of 40 nm are used in the present study to prepare nanofluid by two-step method. A \"Brookfield viscometer\" has been used to measure the dynamic viscosity of nanofluid with solid volume fraction up to 2% at the temperature range between 20 to 60oC. The findings have shown that dynamic viscosity of nanofluid increases with increasing particle volume fraction and decreasing temperature. Nine different correlations are developed on experimental data point to predict the relative dynamic viscosity of nanofluid at different temperatures. To make sure of accuracy of the proposed correlations, margin of deviation is presented at the end of this study. The results show excellent agreement between experimental data and those obtained through the correlations.

Key Words
dynamic viscosity; Ethylene glycol-water based nanofluid; newtonian fluid

Address
Mahmood Rabani Bidgoli and Reza Kolahchi: Department of Civil Engineering, Jasb Branch, Islamic Azad University, Jasb, Iran
Mohammad Saeed Karimi: Faculty of Civil Engineering, Semnan University, Semnan, Iran

Abstract
Multi-storey frame structures are frequently exposed to static and dynamic forces. Therefore analyses of static (buckling) and dynamic stability come into prominence for these structures. In this study, the effects of number of storey, static and dynamic load parameters, crack depth and crack location on the in-plane static and dynamic stability of cracked multi-storey frame structures subjected to periodic loading have been investigated numerically by using the Finite Element Method. A crack element based on the Euler beam theory is developed by using the principles of fracture mechanics. The equation of motion for the cracked multi-storey frame subjected to periodic loading is achieved by Lagrange\'s equation. The results obtained from the stability analysis are presented in three dimensional graphs and tables.

Key Words
dynamic stability; storey frame; crack; buckling; finite element

Address
Mustafa Sabuncu and Hasan Ozturk: Department of Mechanical Engineering, Dokuz Eylul University, Tinaztepe, Buca, Izmir, Turkey
Ahmed Yashar: The Graduate School of Natural and Applied Sciences, Dokuz Eylul University, Tinaztepe, Buca, Izmir, Turkey

Abstract
The national standard being used in Turkey for suspended ceiling systems (SCS) regulates material and dimensional properties but does not contain regulations regarding installation instructions which cause substandard applications of SCSs in practice. The lack of installation instructions would potentially affect the dynamic performance of these systems. Also, the vast majority of these systems are manufactured using substandard low-quality materials, and this will inevitably increase SCS related damages during earthquakes. The experimental work presented here focuses on the issue of dynamic performance of SCSs with different types of carrier systems (lay-on and clip-in systems), different weight conditions, and material-workmanship qualities. Moreover, the effects of auxiliary fastening elements, so called seismic perimeter clips, in improving the dynamic performance of SCSs were experimentally investigated. Results show that clip-in ceiling system performs better than lay-on system regardless of material and workmanship qualities. On the other hand, the quality aspect becomes the most important parameter in affecting the dynamic performance of lay-on type systems as opposed to tile weights and usage of perimeter clips. When high quality system is used, tile weight does not change the performance of lay-on system, however in poor quality system, tile weight becomes an important factor where heavier tiles considerably decrease the performance level. Perimeter clips marginally increase the dynamic performance of lay-on ceiling system, but it has no effect on the clip-in ceiling system under the shaking levels considered.

Key Words
suspended ceiling systems; shake table tests; performance characterization; non-structural elements; seismic perimeter clips

Address
Ozgur Ozcelik and Ibrahim S. Misir: Department of Civil Engineering, Dokuz Eylul University, Kaynaklar Campus, 35160, Izmir, Turkey
Serhan Saridogan: General Directorate of State Hydraulic Works, Izmir, Turkey

Abstract
Utilization of mineral and chemical admixtures in concrete technology has led to changes in the formulation and mix design in recent decades, which has, in turn, made the concrete stronger and more durable. Lightweight concrete is an excellent solution in terms of decreasing the dead load of the structure, while self-compacting concrete eases the pouring and removes the construction problems. Combining the advantages of lightweight concrete and self-compacting concrete is a new and interesting research topic. Considering its light weight of structure and ease of placement, self-compacting lightweight concrete may be the answer to the increasing construction requirements of slender and more heavily reinforced structural elements. Twenty one laboratory experimental investigations published on the mix proportion, density and mechanical properties of lightweight self-compacting concrete from the last 12 years are analyzed in this study. The collected information is used to investigate the mix proportions including the chemical and mineral admixtures, light weight and normal weight aggregates, fillers, cement and water. Analyzed results are presented in terms of statistical expressions. It is very helpful for future research to choose the proper components with different ratios and curing conditions to attain the desired concrete grade according to the planned application.

Key Words
self-compacting light weight concrete; compressive strength; mix proportion; admixtures; fillers; aggregates

Address
Behnam Vakhshouri and Shami Nejadi: Centre for Built Infrastructure Research (CBIR), Faculty of Engineering and Information Technology (FEIT), University of Technology Sydney (UTS), Sydney, Australia

Abstract
The Cuckoo search (CS) algorithm is a simple and efficient global optimization algorithm and it has been applied to figure out large range of real-world optimization problem. In this paper, a new formula is introduced to the discovering probability process to improve the convergence rate and the Tournament Selection Strategy is adopted to enhance global search ability of the certain algorithm. Then an approach for structural damage identification based on modified Cuckoo search (MCS) is presented. Meanwhile, we take frequency residual error and the modal assurance criterion (MAC) as indexes of damage detection in view of the crack damage, and the MCS algorithm is utilized to identifying the structural damage. A simply supported beam and a 31-bar truss are studied as numerical example to illustrate the correctness and efficiency of the propose method. Besides, a laboratory work is also conducted to further verification. Studies show that, the proposed method can judge the damage location and degree of structures more accurately than its counterpart even under measurement noise, which demonstrates the MCS algorithm has a higher damage diagnosis precision.

Key Words
damage detection; Cuckoo search algorithm; modal assurance criteria; tournament selection strategy; discovering probability

Address
H.J. Xu, J.K. Liu and Z.R. Lv: Department of Applied Mechanics and Engineering, Sun Yat-sen University, Guangzhou, Guangdong, P.R. China

Abstract
In this paper, we investigated the propagation of surface waves in a nonhomogeneous rotating fibre-reinforced viscoelastic anisotropic media of higher order of nth order including time rate of strain. The general surface wave speed is derived to study the effect of rotation on surface waves. Particular cases for Stoneley, Love and Rayleigh waves are discussed. The results obtained in this investigation are more general in the sense that some earlier published results are obtained from our result as special cases. Also results for homogeneous media can be deduced from this investigation. For order zero our results are well agreed to fibre-reinforced materials. Also by neglecting the reinforced elastic parameters, the results reduce to well known isotropic medium. It is also observed that, surface waves cannot propagate in a fast rotating medium. Comparison was made with the results obtained in the presence and absence of rotation and parameters for fibre-reinforced of the material medium Numerical results are given and illustrated graphically. The results indicate that the effect of rotation and parameters for fibre-reinforced of the material are very pronounced.

Key Words
fibre-reinforced; viscoelastic; surface waves; rotation; anisotropic; nonhomogeneous

Address
S.M. Abo-Dahab: Mathematics Department, Faculty of Science, Taif University 888, Saudi Arabia; Mathematics Department, Faculty of Science, SVU, Qena 83523, Egypt
A.M. Abd-Alla: Mathematics Department, Faculty of Science, Taif University 888, Saudi Arabia; Mathematics Department, Faculty of Science, Sohag University, Egypt
Aftab Khan: Department of Mathematics, COMSATS, Institute of Information, Park Road, Chakshahzad, Islamabad, Pakistan


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