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CONTENTS
Volume 46, Number 4, May25 2013
 

Abstract
Splitting tensile strength (STS) is a respectable mechanical property reflecting ability of the concrete. The STS of concrete is mainly related to compressive strength (CS), water/binder (W/B) ratio and concrete age. In this study, the assessment of STS is made by a novel uncertainty-oriented method which uses least square optimization and then predicts STS of concrete by uncertain (fuzzy) numbers. The approximation method addresses a novel integration of fuzzy set theory and multivariate statistics. The numerical examples showed that the method is applicable with relatively limited data. In addition, the prediction of uncertainty at various levels of possibility can be described. In conclusion, the uncertaintyoriented interval analysis can be suggested an effective tool for appraising the uncertainties in concrete technology.

Key Words
tensile strength; concrete; uncertainty; fuzzy number; interval analysis

Address
Bulent Tutmez, Didem Eren Sarici : School of Engineering, Inonu University, 44280 Malatya, Turkey
A. Kemal Cengiz : School of Engineering, Hacettepe University 06532 Ankara, Turkey

Abstract
A novel damage classification method based on wavelet packet transform and statistical analysis is developed in this study for structural health monitoring. The response signal of a structure under an impact load is normalized and then decomposed into wavelet packet components. Energies of these wavelet packet components are then calculated to obtain the energy distribution. Statistical similarity comparison based on an F-test is used to classify the structure from changes in the wavelet packet energy distribution. A statistical indicator is developed to describe the damage extent of the structure. This approach is applied to the test results from simply supported reinforced concrete beams in the laboratory. Cases with single and two damages are created from static loading, and accelerations of the structure from under impact loads are analyzed. Results show that the method can be used with no reference baseline measurement and model for the damage monitoring and assessment of the structure with alarms at a specified significance level.

Key Words
time domain; damage; inverse problem; wavelet packet; F-test; reinforced concrete; statistics; variance; skewness; kurtosis

Address
S.S. Law : 1Department of Civil and Environmental Engineering, Hong Kong Polytechnic University,Hunghom, Kowloon, Hong Kong, P.R. China
X.Q. Zhu : School of Computing, Engineering and Mathematics, University of Western Sydney, NSW 2751, Australia
Y.J. Tian : School of Civil Engineering, Beijing Jiaotong University, P.R. China
X.Y. Li : Department of Mechanics and Civil Engineering, Jinan University, P.R. China
S.Q. Wu : Department of Engineering Mechanics, Southeast University,P.R. China

Abstract
In the present work a new friction device, with a set of single or double rotational friction flanges and a link element, is described and tested. The mechanism may be applied for the strengthening of existing r/c or steel buildings as well as in new constructed buildings. The device has selectable variable behavior in different levels of displacement and an interlock me a hanism that is provided by the link element. The link element may be designed to lock at preselected level of displacement, offering in this way an extra safety reserve against strong earthquakes. A summary of the existing literature about other similar mechanisms is initially presented in this paper. The proposed mechanism is presented and described in details. Laboratory experiments are presented in detail and the resulted response that proves the efficiency of the mechanism at selectable levels of strength capacity is discussed. Drawings of the mechanism attached to a r/c frame with connection details are also included. Finally a dynamic analysis of two r/c frames, with and without the proposed mechanism attached, is performed and the resulted response is given. The main conclusion is that the proposed mechanism is a cheap and efficient devise for the improvement of the performance of new or existing framed buildings to seismic loads.

Key Words
multi-storey frames; bracing; variable strengthening; metal friction device; experimental tests; cyclic loading; link element; numerical approach

Address
Panikos K. Papadopoulos, Stergios A. Dimitrakis and Alkis P. Papadopoulos : Aristotle University of Thessaloniki, Department of Civil Engineering, University Campus,
Thessaloniki, Greece
Thomas N. Salonikios : Earthquake Planning and Protection Organization, Research Division, Agiou Georgiou 5,
Thessaloniki, Greece

Abstract
In this study, the seismic performance of a residential building which was damaged in the 1992 Erzincan (Turkey) Earthquake (Ms = 6.8) is performed. Damages on columns due to short columns are estimated analytically implementing the shear hinges and results are compared with the observed damages on the building after the earthquake. In seismic performance evaluation, a deformation based approach is adopted, whereby the structural behavior under external and seismic loads is evaluated. Furthermore, the effects of short columns formed by band windows in basement floors are investigated analytically. The sizes of band windows are parametrically changed in order to understand the effects of short columns on overall building behavior.

Key Words
short columns; seismic performance analysis; pushover analysis; non-linear time history analysis

Address
Ali Kocak : Department of Civil Engineering, Yildiz Technical University, 34210, Istanbul, Turkey

Abstract
To have a better understanding of the torsional mechanism and influencing factors of PC composite box-girder with corrugated steel webs, ultimate torsional strength of four specimens under pure torsion were analyzed with Model Test Method. Monotonic pure torsion acts on specimens by eccentric concentrated loading. The experimental results show that cracks form at an angle of 45o to the member\'s longitudinal axis in the top and bottom concrete slabs. Longitudinal reinforcement located in the center of cross section contributes little to torsional capacity of the specimens. Torsional rigidity is proportional to shape parameter n of corrugation and there is an increase in yielding torque and ultimate torque of specimens as the thickness of corrugated steel webs increases.

Key Words
corrugated steel webs; composite box girder; ultimate torsional strength; cracks; space truss

Address
Yong Ding, Kebin Jiang, Fei Shao : Department of Bridge and Tunnel Engineering, PLA University of Science and Technology, No.1 Haifu Lane, Baixia District, Nanjing City, China
Anzhong Deng : Department of Civil Engineering, Institute of Logistics Engineering of PLA, Chongqing Municipality, China

Abstract
\"Reciprocal Frame\" refers to a self-supporting grid structure used both for floor and roof. Using Finite Element Methods for non-linear solid mechanics and frictional-contact, this paper intends to analytically and numerically investigate the collapse behaviour of a reciprocal frame structure made of fibrereinforced concrete. Considering a simple 3-beam structure, it has been investigated using a solid finite element model. Once defined the collapse behaviour of the simple structure, the analysis has been generalized using a concentrated plasticity finite element method. Results provided will be useful for studying generic reciprocal frame structures with several beams.

Key Words
reciprocal frame; nexorades; space structures; finite elements; collapse behaviour; temporary structures

Address
Elsa Garavaglia, Luca Sgambi and Noemi Basso : Department of Civil and Environmental Engineering, Politecnico di Milano, Milan, Italy
Attilio Pizzigoni : Department of Design and Technology, Universita degli Studi di Bergamo, Bergamo, Italy

Abstract
A passive control using flaps will be an alternative solution for flutter stability and buffeting response of a long suspension bridge. This method not only enables a lightweight economic stiffening girder without an additional stiffness for aerodynamic stability but also avoid the problems from the malfunctions of control systems and energy supply system of an active control by winglets and flaps. A time domain approach for predicting the coupled flutter and buffeting response of bridge deck with flaps is investigated. First, the flutter derivatives of bridge deck and flaps are found by experiment. Next, the derivation of time domain model of self-excited forces and control forces of sectional model is reported by using the rational function approximation. Finally, the effectiveness of passive flap control is investigated by the numerical simulation. The results show that the passive control by using flaps can increase the flutter speed and decrease the buffeting response. The experiment results are matched with numerical ones.

Key Words
flutter, buffeting, suspension bridge, passive control, flaps, rational function approximation

Address
Duc - Huynh Phan : Department of Civil Engineering, the University of Education and Technology, VietNam
Hiroshi Kobayshi : Ritsumeikan University, Japan

Abstract
Railway truss bridges are amongst the essential structures in railway transportation. Minimization of the construction and maintenance costs of these trusses can effectively reduce investments in railway industries. In case of railway bridges, due to high ratio of the live load to the dead load, the moving load has considerable influence on the bridge dynamics. In this paper, optimization of the railway truss bridges under moving load is taken into consideration. The appropriate algorithm namely Hyper-sphere algorithm is used for this multifaceted problem. Through optimization the efficiency of the method successfully raised about 5 percent, compared with similar algorithms. The proposed optimization carried out on several typical railway trusses. The influences of buckling, deformation constraints, and the optimum height of each type of truss, assessed using a simple approximation method.

Key Words
railway truss bridge; moving load; numerical optimization; modified hyper-sphere algorithm; three-level technique

Address
Saeed Mohammadzadeh and Mehrdad Nouri : School of Railway Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran, 16846-13114


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