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CONTENTS
Volume 24, Number 1, May20 2017
 

Abstract
In order to improve the deformation capacity of the high-strength concrete shear wall, five high-strength concrete shear wall specimens confined with high-strength rectangular spiral reinforcement (HRSR) possessing different parameters, were designed in this paper. One specimen was only adopted high-strength rectangular spiral hoops in embedded columns, the rest of the four specimens were used high-strength rectangular spiral hoops in embedded columns, and high-strength spiral horizontal distribution reinforcement were used in the wall body. Pseudo-static test were carried out on high-strength concrete shear wall specimens confined with HRSR, to study the influence of the factors of longitudinal reinforcement ratio, hoop reinforcement form and the spiral stirrups outer the wall on the failure modes, failure mechanism, ductility, hysteresis characteristics, stiffness degradation and energy dissipation capacity of the shear wall. Results showed that using HRSR as hoops and transverse reinforcements could restrain concrete, slow load carrying capacity degeneration, improve the load carrying capacity and ductility of shear walls; under the vertical force, seismic performance of the RC shear wall with high axial compression ratio can be significantly improved through plastic hinge area or the whole body of the shear wall equipped with outer HRSR.

Key Words
high-strength rectangular spiral reinforcement; shear walls; pseudo-static test; seismic performance

Address
Xi'an University of Architecture and Technology, 710055, Xi'an, China.

Abstract
A green biosynthesis method is described for the preparation of Polyaniline (PANI)-cerium dioxide (CeO2) nanocomposites in different media via in-situ oxidative polymerization procedure. The effect of various media including use of HCl, Lemon Juice, Beverage, White Vinegar, Verjuice and Apple vinegar extracts on the particles size, morphology as well as the conductivity of PANI-CeO2 nanocomposites was investigated. The electron-withdrawing feature of CeO2 increases doping level of PANI and enhances electron delocalization. These cause a significantly blue shift of C = C stretching band of quinoid from 1570 cm-1 to 1585 cm-1. The optical properties of the pure material and polymeric nanocomposites as well as their interfacial interaction in nanocomposite structures analyzed by UV-visible spectroscopy. The DC electrical conductivity (

Key Words
natural solution; PANI-CeO2; nanocomposite; in situ oxidative

Address
Department of Chemistry, Faculty of Sciences, Najafabad Branch, Islamic Azad University, P.O. Box 517, Najafabad, Iran.

Abstract
Current form of Corrugated-strip connectors are not popular due to the fact that the two ends of this form need to be welded to steel face plates. To overcome this difficulty, a new system is proposed in this work. In this system, bi-directional corrugated-strip connectors are used in pairs, and only one of their ends is welded to the steel face plates on each side. The other end is embedded in the concrete core. To assemble the system, common welding devices are required, and welding process can be performed in the construction sites. By performing the Push-out test under static loading, the authors experimentally assess the effects of geometric parameters on ductility, failure modes and the ultimate shear strength of the aforesaid connectors. For this purpose, sixteen experimental samples are prepared and investigated. For fifteen of these samples, one end of the shear connectors is welded to steel face plates, and the other end is embedded in the concrete. Another experimental sample is prepared in which both ends are welded to the steel face plates. According to the achieved results, several relations are proposed for predicting the ultimate shear strength and load vs. interlayer slip (load-slip) behavior of corrugated-strip connectors. Moreover, these formulas are compared with those of the well-known codes and standards. Accordingly, it is concluded that the authors' relations are more reliable.

Key Words
steel-concrete-steel sandwich; corrugated-strip connectors; push-out test; maximum shear strength; load-slip

Address
Civil Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.

Abstract
To quantitatively assess the safety against seismic collapse of eccentrically braced steel frame (EBSF) system, 24 typical EBSFs with K-shape and V-shape braces with seismic precautionary intensities 8 and 9 were designed complying with China seismic design code and relative codes to constitute archetype space of this structure system. In the archetype space, the collapse probability of the structural system under maximum considered earthquakes (MCE) was researched. The results show that the structures possess necessary safety against seismic collapse when they respectively encounter the maximum considered earthquakes corresponding to their seismic precautionary levels, and their collapse probabilities increase with increasing seismic precautionary intensities. Moreover, the EBSFs with V-shape braces have smaller collapse probability, thus greater capacity against seismic collapse than those with K-shape braces.

Key Words
seismic collapse; collapse probability; EBSF; IDA; rare earthquake

Address
Changzhou Key Lab of Construction Engineering Structure and Material Properties, Changzhou Institute of Technology, No. 666, Liaohe Road, Changzhou City, Jiangsu Province, China.

Abstract
The paper presents the simplified matrix stiffness method for analysis of composite and prestressed beams. The method is based on the previously developed "exact" analysis method that uses the mathematical theory of linear integral operators to derive all relations without any mathematical simplifications besides inevitable idealizations related to the material rheological properties. However, the method is limited since the closed-form solution can be found only for specific forms of the concrete creep function. In this paper, the authors proposed the simplified analysis method by introducing the assumption that the unknown deformations change linearly with the concrete creep function. Adopting this assumption, the nonhomogeneous integral system of equations of the "exact" method simplifies to the system of algebraic equations that can be easily solved. Therefore, the proposed method is more suitable for practical applications. Its high level of accuracy in comparison to the "exact" method is preserved, which is illustrated on the numerical example. Also, it is more accurate than the well-known EM method.

Key Words
composite beam; viscoelastic analysis; creep; shrinkage; matrix stiffness method; linear integral operators

Address
Faculty of Civil Engineering, University of Belgrade, Bul Kralja Aleksandra 73, Belgrade, Serbia.

Abstract
The purpose of this research is to study the nonlinear free vibration and post-buckling analysis of functionally graded carbon nanotube reinforced composite (FG-CNTRC) beams resting on a nonlinear elastic foundation. Uniformly and functionally graded distributions of single walled carbon nanotubes as reinforcing phase are considered in the polymeric matrix. The modified form of rule of mixture is used to estimate the material properties of CNTRC beams. The governing equations are derived employing Euler-Bernoulli beam theory along with energy method and Hamilton\'s principle. Applying von Kárman\'s strain-displacement assumptions, the geometric nonlinearity is taken into consideration. The developed governing equations with quadratic and cubic nonlinearities are solved using variational iteration method (VIM) and the analytical expressions and numerical results are obtained for vibration and stability analysis of nanocomposite beams. The presented comparative results are indicative for the reliability, accuracy and fast convergence rate of the solution. Eventually, the effects of different parameters, such as foundation stiffness, volume fraction and distributions of carbon nanotubes, slenderness ratio, vibration amplitude, coefficients of elastic foundation and boundary conditions on the nonlinear frequencies, vibration response and post-buckling loads of FG-CNTRC beams are examined. The developed analytical solution provides direct insight into parametric studies of particular parameters of the problem.

Key Words
nanocomposites; functionally graded beams; nonlinear vibration; post-buckling loads; nonlinear elastic foundation

Address
Department of Mechanical and Aerospace Engineering, Shiraz University of Technology, Shiraz 71555, Iran.

Abstract
Free vibrations of steel-concrete composite beams are analyzed by using the dynamic stiffness approach. The coupled equations of motion of the composite beams are derived with help of the Hamilton's principle. The effects of the shear deformation and rotary inertia of the two beams as well as the transverse and axial deformations of the stud connectors are included in the formulation. The dynamic stiffness matrix is developed on the basis of the exact general solutions of the homogeneous governing differential equations of the composite beams. The use of the dynamic stiffness method to determine the natural frequencies and mode shapes of a particular steel-concrete composite beam with various boundary conditions is demonstrated. The accuracy and effectiveness of the present model and formulation are validated by comparison of the present results with the available solutions in literature.

Key Words
steel-concrete composite beams; shear deformation; rotary inertia; free vibration; dynamic stiffness approach

Address
Departments of Naval Architecture, Ocean and Structural Engineering, School of Transportation, Wuhan University of Technology, Wuhan, China.

Abstract
Metaheuristic algorithms in general make use of uniform random numbers in their search for optimum designs. Levy Flight (LF) is a random walk consisting of a series of consecutive random steps. The use of LF instead of uniform random numbers improves the performance of metaheuristic algorithms. In this study, three discrete optimum design algorithms are developed for steel skeletal structures each of which is based on one of the recent metaheuristic algorithms. These are biogeography-based optimization (BBO), brain storm optimization (BSO), and artificial bee colony optimization (ABC) algorithms. The optimum design problem of steel skeletal structures is formulated considering LRFD-AISC code provisions and W-sections for frames members and pipe sections for truss members are selected from available section lists. The minimum weight of steel structures is taken as the objective function. The number of steel skeletal structures is designed by using the algorithms developed and effect of LF is investigated. It is noticed that use of LF results in up to 14% lighter optimum structures.

Key Words
metaheuristic algorithms; levy flight; steel skeleton structures; artificial bee colony; biogeography-based optimization; brain storm optimization

Address
(1) Ibrahim Aydogdu:
Department of Civil Engineering, Akdeniz University, Dumlupinar Bvld., 07058, Antalya, Turkey;
(2) Serdar Carbas:
2Department of Civil Engineering, Karamanoglu Mehmetbey University, Karaman, Turkey;
(3) Alper Akin:
Trinity Meyer Utility Structures, Memphis, TN, USA.

Abstract
This paper highlights a study undertaken on the free vibration of a precast steel-concrete composite slab panel for track support. The steel-concrete composite slab track is an evolvement from the slab track, a form of ballastless track which is becoming increasingly attractive to asset owners as they seek to reduce lifecycle costs and deal with increasing rail traffic speeds. The slender nature of the slab panel due to its reduced depth of construction makes it susceptible to vibration problems. The aim of the study is driven by the need to address the limited research available to date on the dynamic behaviour of steel-concrete composite slab panels for track support. Free vibration analysis of the track slab has been carried out using ABAQUS. Both eigenfrequencies and eigenmodes have been extracted using the Lanczos method. The fundamental natural frequencies of the slab panel have been identified together with corresponding mode shapes. To investigate the sensitivity of the natural frequencies and mode shapes, parametric studies have been established, considering concrete strength and mass and steel

Key Words
free vibration; steel-concrete composite; ballastless track; slab panel track; natural frequency; natural mode; mass; stiffness; crossover; veering

Address
(1) Stephen Kimindiri Kimani:
Department of Civil Engineering, School of Engineering, University of Birmingham, Birmingham B15 2TT, UK;
(2) Sakdirat Kaewunruen:
Birmingham Centre for Railway Research and Education, School of Engineering, University of Birmingham, Birmingham B15 2TT, UK.

Abstract
Structural optimization is one of the popular and active research areas in the field of structural engineering. In the present study, the newly developed moth-flame optimization (MFO) algorithm and its enhanced version termed as enhanced moth-flame optimization (EMFO) are employed to implement the optimization process of planar and 3D steel frame structures with discrete design variables. The main inspiration of this optimizer is the navigation method of moths in nature called transverse orientation. A number of benchmark steel frame optimization problems are solved by the MFO and EMFO algorithms and the results are compared with those of other meta-heuristics. The obtained numerical results indicate that the proposed EMFO algorithm possesses better computational performance compared with other existing meta-heuristics.

Key Words
steel structures; optimization; meta-heuristic; enhanced moth-flame algorithm

Address
Department of Civil Engineering, Urmia University, Urmia, West Azerbaijan Province, Iran.


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