Techno Press
Tp_Editing System.E (TES.E)
Login Search


sem
 
CONTENTS
Volume 44, Number 2, October25 2012
 

Abstract
The composite materials may be exposed to environmental (thermal or hygral or both) condition during their service life. The effect of environmental condition is usually adverse from the point of view of design of composite structures. In the present research study the effect of hygrothermal condition on the design of laminated composite structures is investigated. The active fiber composite (AFC) which may be utilized as actuator or sensor is considered in the present analysis. The sensor layer is used to sense the level of response of the composite structures. The sensed voltage is fed back to the actuator through the controller. In this study both displacement and velocity feedback controllers are employed to reduce the response of the composite laminate within acceptable limit. The Newmark direct time integration scheme is employed along with modal superposition method to improve the computational efficiency. It is observed from the numerical study that the laminated composite structures become weak in the presence of hygrothermal load. The response of the structure can be brought to the acceptable level once the AFC layer is activated through the feedback loop.

Key Words
AFC; hygrothermal; sensor; actuator; active vibration control; preload

Address
P.K. Mahato: Mechanical Engineering and MME, Indian School of Mines, Dhanbad-826004, India
D.K. Maiti: Aerospace Engineering, Indian Institute of Technology, Kharagpur-721302, India

Abstract
In this paper, the static behavior of bi-directional functionally graded (FG) non-uniform thickness circular plate resting on quadratically gradient elastic foundations (Winkler-Pasternak type) subjected to axisymmetric transverse and in-plane shear loads is carried out by using state-space and differential quadrature methods. The governing state equations are derived based on 3D theory of elasticity, and assuming the material properties of the plate except the Poisson\'s ratio varies continuously throughout the thickness and radius directions in accordance with the exponential and power law distributions. The stresses and displacements distribution are obtained by solving state equations. The effects of foundation stiffnesses, material heterogeneity indices, geometric parameters and loads ratio on the deformation and stress distributions of the FG circular plate are investigated in numerical examples. The results are reported for the first time and the new results can be used as a benchmark solution for future researches.

Key Words
FG circular plate; gradient elastic foundation; elasticity; state - space; DQ method

Address
A. Behravan Rad: Department of Mechanical Engineering, Karaj Branch, Islamic Azad University, Karaj, Iran

Abstract
A strut-and-tie model is introduced in this paper to predict the ultimate shear strength of nonseismically detailed columns. The validity and applicability of the proposed strut-and-tie model are evaluated by comparison with available experimental data. The model was developed based on visible crack patterns observed on the test specimens. The concrete contribution is integrated into the strut-and-tie model through a concept of equivalent transverse reinforcement. To further validate the model a full-scale non-seismically detailed reinforced concrete column was tested to investigate its seismic behavior. The specimen was tested under the combination of a constant axial load, 0.30fc\'Ag and quasi-static cyclic loadings simulating earthquake actions. Quasi-static cyclic loadings simulating earthquake actions were applied to the specimen until it could not sustain the applied axial load. The analytical results reveal that the strut-and-tie method is capable of modeling to a satisfactory accuracy the ultimate shear strength of non-seismically detailed columns subjected to reserved cyclic loadings.

Key Words
reinforced concrete columns; strut-and-tie; seismic; shear strength

Address
Cao Thanh Ngoc Tran: Department of Civil Engineering, International University, Vietnam National University,
Ho Chi Minh City, Vietnam

Abstract
An eigenspace projection clustering method is proposed for structural damage detection by combining projection algorithm and fuzzy clustering technique. The integrated procedure includes data selection, data normalization, projection, damage feature extraction, and clustering algorithm to structural damage assessment. The frequency response functions (FRFs) of the healthy and the damaged structure are used as initial data, median values of the projections are considered as damage features, and the fuzzy c-means (FCM) algorithm are used to categorize these features. The performance of the proposed method has been validated using a three-story frame structure built and tested by Los Alamos National Laboratory, USA. Two projection algorithms, namely principal component analysis (PCA) and kernel principal component analysis (KPCA), are compared for better extraction of damage features, further six kinds of distances adopted in FCM process are studied and discussed. The illustrated results reveal that the distance selection depends on the distribution of features. For the optimal choice of projections, it is recommended that the Cosine distance is used for the PCA while the Seuclidean distance and the Cityblock distance suitably used for the KPCA. The PCA method is recommended when a large amount of data need to be processed due to its higher correct decisions and less computational costs.

Key Words
structural damage detection; eigenspace projections; fuzzy clustering; principal component analysis; kernel principal component analysis

Address
Jun-hua Zhu: MOE Key Lab of Disaster Forecast and Control in Engineering, Jinan University, Guangzhou, 510632, P. R. China; China Electronic Product Reliability and Environmental Testing Research Institute, Guangzhou, 510610, P. R. China
Ling Yu: MOE Key Lab of Disaster Forecast and Control in Engineering, Jinan University, Guangzhou, 510632, P. R. China; Department of Mechanics and Civil Engineering, Jinan University, Guangzhou, 510632, P. R. China
Li-li Yu: MOE Key Lab of Disaster Forecast and Control in Engineering, Jinan University, Guangzhou, 510632, P. R. China; School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, P. R. China

Abstract
Detailed analysis of internal forces of exterior beam-column joints of RC frames under seismic action is reported in this paper. A formula is derived for calculating the average joint shear from the column shears, and a formula is proposed to estimate torque in eccentric joints induced by seismic action. Average joint shear stress and strain are defined consistently for exterior joints, which can be used to establish joint shear constitutive relationship. Numerical results of shear, bending moment and torque in joints induced by seismic action are presented for a pair of concentric and eccentric exterior connections extracted from a seismically designed RC frame, and two sections located at the levels of beam bottom and top reinforcement, respectively, are identified as the critical joint sections for evaluating seismic joint behavior. A simplified analysis of the effects of joint shear and torque on the flexural strengths of the critical joint sections is made for the two connections extracted from the frame, and the results indicate that joint shear and torque induced by a strong earthquake may lead to \"joint-hinging\" mechanism of seismically designed RC frames.

Key Words
axial strength; beam columns; flexural strength; joints; reinforced concrete; seismic behavior; shear strain; shear stress; torsion

Address
Hua Zhou and Zhisheng Zhang: Department of Civil Engineering, Hainan University, 58 Renming Dadao, Haikou, Hainan, 570228 People\'s Republic of China

Abstract
Objective of this paper is to compare linear buckling analysis formulations, available in commercial finite element programs. Modern steel design codes, including Eurocode 3, make abundant use of linear buckling loads for calculation of slenderness, and of linear buckling modes, used as shapes of imperfections for nonlinear analyses. Experience has shown that the buckling mode shapes and the magnitude of buckling loads may differ, sometimes significantly, from one algorithm to another. Thus, three characteristic examples have been used in order to assess the linear buckling formulations available in the finite element programs ADINA and ABAQUS. Useful conclusions are drawn for selecting the appropriate algorithm and the proper reference load in order to obtain either the classical linear buckling load or a good approximation of the actual geometrically nonlinear buckling load.

Key Words
buckling analysis; steel structures; column; arch; shell; nonlinear behaviour

Address
C.A. Dimopoulos and C.J. Gantes: Institute of Steel Structures, School of Civil Engineering, National Technical University of Athens, Greece

Abstract
This work presents a contribution to understand the inverted trussed beams behavior. The system has a main beam and struts with rectangular cross section associated to a wire rope enlaced to the main beam. It is an unpublished system with the advantage of easy positioning of the wire rope, once it is a continuous and connected by turnbuckles. It is a system that can be used as support for concrete formworks or for rehabilitation wooden beams proposal. The enlacement of the cable demands a small notch at the top of the cross section and a cross pin at the bottom. Six inverted trussed beams were tested, with spans of 180 cm with cables diameter of 1/4\". Additionally, four simple beams without any external steel cable were also tested with material from the same lot of wood, allowing a comparison in rupture. The results showed capacity gain of around 60% compared to a simple beam. Once the wire rope characteristics and anchoring are very important for structure response, some improvement suggestions for the efficiency of the cables are also presented.

Key Words
inverted trussed beam; wire rope; rectangular section; notch

Address
F.A.R. Gesualdo and M.C.V. Lima: School of Civil Engineering, Federal University of Uberlandia, 38400-902 Uberlandia, Brazil

Abstract
Walls are the most important vertical load-carrying elements of masonry structures. Their bond designs are different from one country to another. This paper presents the shear effects of some structural bond designs commonly used for masonry walls. Six different bond designs are considered and modeled using finite element procedures under lateral loading to examine the shear behavior of masonry walls. To obtain accurate results, finite element models are assumed in the inelastic region. Crack development patterns for each wall are illustrated on deformed meshes, and the numerical results are compared.

Key Words
masonry; bonding design; inelastic behavior; crack development

Address
A. Ural: Faculty of Engineering (Civil), Aksaray University, Aksaray, Turkey
A. Dogangun: Faculty of Engineering (Civil), Uludag University, Bursa, Turkey


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com