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CONTENTS
Volume 9, Number 4, April 2000
 

Abstract
An analytical approach for the prediction of the behaviour of steel-fiber reinforced concrete beams subjected to torsion is described. The analysis method employs a special stress-strain model with a non-linear post cracking branch for the material behaviour in tension. Predictions of this model for the behaviour of steel-fiber concrete in direct tension are also presented and compared with results from tests conducted for this reason. Further in this work, the validation of the proposed torsional analysis by providing comparisons between experimental curves and analytical predictions, is attempted. For this purpose a series of 10 steel-fiber concrete beams with various cross-sections and steel-fiber volume fractions tested in pure torsion, are reported here. Furthermore, experimental information compiled from works around the world are also used in an attempt to establish the validity of the described approach based on test results of a broad range of studies. From these comparisons it is demonstrated that the proposed analysis describes well the behaviour of steel-fiber concrete in pure torsion even in the case of elements with non-rectangular cross-sections.

Key Words
steel-fiber concrete, torsion, nonlinear analysis, tensional model, torsional tests, L and T-beams

Address
Karayannis CG, Democritus Univ Thrace, Dept Civil Engn, GR-67100 Xanthi, Greece
Democritus Univ Thrace, Dept Civil Engn, GR-67100 Xanthi, Greece

Abstract
The creep deformation of pure bending (hold constant moment for a period of time) tests were conducted in this paper. Thin-walled tubes of 304 stainless steel were used in this investigation. The curvature-ovalization measurement apparatus, designed by Pan rt nl. (1998), was used for conducting the present experiments. It has been found that as soon as the creep deformation is started, the magnitudes of the tube curvature and ovalization of tube cross-section quickly increase. The magnitudes of the creep curvature and ovalization of tube cross-section increase fast with a higher hold moment than that with a lower one. Owing to the continuously increasing curvature during the creep deformation, the tube specimen buckles eventually.

Key Words
thin-walled tube, pure bending, creep deformation

Address
Natl Cheng Kung Univ, Dept Engn Sci, Tainan 70101, Taiwan

Abstract
This paper aims to make a contribution to understanding which methods apply for structural analysis of beams prestressed with FRP cables. A parametric non-linear numerical analysis of simply supported beams has been performed. In this analysis the shape of the cross-section, the strength of concrete, the material adopted for the cables (steel, GFRP, CFRP), the prestressing system (bonded or unbonded prestressing) and the degree of prestressing were changed to collect a broad range of data which, the author contends, should cover the most frequent types of common practice. The output data themselves and their comparison allow us to suggest some rules that could be adopted when dealing with beams prestressed with these innovatory materials that have an elastic-brittle behaviour.

Key Words
fibre reinforced plastic cables, unbonded prestressing, bonded prestressing, structural analysis, load-carrying capacity

Address
Pisani MA, Politecn Milan, Dept Struct Engn, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy
Politecn Milan, Dept Struct Engn, I-20133 Milan, Italy

Abstract
The structural behavior of connections between concrete-filled rectangular tubular column (CFRT column) and steel beam has been studied in this paper through sub-assemblage loading tests. It is found that the sub-assemblages exhibit ductile restoring force characteristics under seismic loading. A formula for the prediction of the yield strength of each member in the connection is proposed by using the yield line theory under the assumption of a simple stress transfer mechanism. It is shown that the proposed formula can produce a reasonable prediction while providing a basis for further investigation.

Key Words
experiment, seismic behavior, connection, concrete-filled rectangular tubular column, steel beam

Address
Lu XL, Tongji Univ, Shanghai 200092, Peoples R China
Tongji Univ, Shanghai 200092, Peoples R China

Abstract
Experimental investigation into the cyclic behaviour of sand plast brick masonry was performed on forty two square panels. The panels were subjected to cyclic uniaxial compression for two cases of loading: normal to bed joint and parallel to bed joint. Experimental data were used to plot the unloading-reloading curves for the entire range of the stress-strain curve. Mathematical expressions to predict the reloading and unloading stress-strain curves at various values of residual strain are proposed. A simple parabola and an exponential type formula are found adequate to model the unloading and reloading curves respectively. The models account for the potential effects of residual strain on these curves. Comparison of test results with the proposed mathematical expression shows good correspondence.

Key Words
cyclic loading, unloading, reloading, plastic strain, envelope curve

Address
AlShebani MM, Indian Inst Technol, Dept Civil Engn, New Delhi 110016, India
Indian Inst Technol, Dept Civil Engn, New Delhi 110016, India

Abstract
A new structure-vibration-control approach is proposed which uses a passive coupling element between two parallel structures to reduce the seismic response of a system due to earthquake excitation. Dynamic characteristics of the two coupled single-degree-freedom systems subject to stationary white-noise excitation are examined by means of statistical energy analysis (SEA) techniques. Optimal parameters of the passive coupling element such as damping and stiffness under different circumstances are determined with an emphasis on the influence of the structural parameters of the system on the optimal parameters and control effectiveness. Numerical results including the root mean square values of the response due to the filtered white-noise excitation and the time-histories of response to El Centro 1940 NS excitation are presented.

Key Words
parallel structure, optimal passive control, seismic response, statistical energy analysis

Address
Zhu HP, Huazhong Univ Sci & Technol, Sch Civil Engn, Wuhan 430074, Peoples R China
Huazhong Univ Sci & Technol, Sch Civil Engn, Wuhan 430074, Peoples R China
Kyoto Univ, Grad Sch Civil Engn, Sakyo Ku, Kyoto 60601, Japan

Abstract
The present study deals with the nonlinear dynamics and stability of autonomous dissipative either imperfect potential (limit point) systems or perfect (bifurcational) non-potential ones. Through a fully nonlinear dynamic analysis, performed on two simple 2-DOF models corresponding to the classes of systems mentioned above, and with the aid of basic definitions of the theory of nonlinear dynamical systems, new important phenomena are revealed. For the first class of systems a third possibility of postbuckling dynamic response is offered, associated with a point attractor on the prebuckling primary path, while for the second one the new findings are chaos-like (most likely chaotic) motions, consecutive regions of point and periodic attractors, series of global bifurcations and point attractor response of always existing complementary equilibrium configurations, regardless of the value of the nonconservativeness parameter.

Key Words
autonomous systems, dynamic buckling, point attractors, static and dynamic bifurcations, chaotic transients

Address
Sophianopoulos DS, Natl Tech Univ Athens, Dept Civil Engn, Met Struct Lab, 42 Patis Str, GR-10682 Athens, Greece
Natl Tech Univ Athens, Dept Civil Engn, Met Struct Lab, GR-10682 Athens, Greece


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