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CONTENTS
Volume 9, Number 1, January 2000
 

Abstract
To study the dynamic response of a rigid block standing unrestrained on a rigid foundation which shakes horizontally, four modes of motion can be identified, i.e., rest, slide, rock, and slide and rock. The occurrence of each of these four modes and the transition between any two modes depend on the parametric values specified, the initial conditions, and the magnitude of ground acceleration. In this paper, a general two-dimensional theory is presented for dealing with the various modes of a free-standing rigid block, considering in particular the impact occurring during the rocking motion. Through selection of proper values for the system parameters, the occurrence of each of the four modes and the transition between different modes are demonstrated in the numerical examples.

Key Words
friction, impact, overturning, rocking, sliding

Address
Yang YB, Natl Taiwan Univ, Dept Civil Engn, Taipei 10764, Taiwan
Natl Taiwan Univ, Dept Civil Engn, Taipei 10764, Taiwan

Abstract
Dynamic response of a three span continuous bridge has been determined by full scale experiments on the bridge. In the experiments, a heavy vehicle was driven across the bridge at different speeds and along different lanes of travel and the strains were recorded at different locations. The bridge was made of reinforced concrete and was asymmetric in plan and in elevation. Frequencies and modes of vibration excited by the vehicle were determined. The dependence of the dynamic amplification on bridge location and vehicle speed was investigated and dynamic amplifications up to 1.5 were recorded, which was higher than values predicted by bridge design codes. It was evident that when this asymmetric bridge was loaded by an asymmetric forcing function, higher modes, which are lateral and/or torsional in nature, were excited. Dynamic modulus of elasticity and the support stiffness influenced the natural frequencies of the bridge, which in turn influenced the dynamic amplifications. Larger than anticipated dynamic amplification factors and the excitation of lateral and/or torsional modes should be of interest and concern to bridge engineers.

Key Words
bridge, dynamic response, strains, dynamic amplification, experimental testing, vibration, frequency, mode, asymmetry, torsion, bridge code

Address
Thambiratnam DP, Queensland Univ Technol, Sch Civil Engn, Phys Infrastruct Ctr, GPO Box 2434, Brisbane, Qld 4001, Australia
Queensland Univ Technol, Sch Civil Engn, Phys Infrastruct Ctr, Brisbane, Qld 4001, Australia
Madsen & Giersing, Consulting Engineers, Brisbane, Qld 4001, Australia

Abstract
Very few studies on orthotropic circular disks or rings under diametrical loadings are conducted because of difficulties in treatment. This paper shows analytical solutions and gives the distributions of stresses and displacements by using Lekhnitskii\'s complex variable method. Several numerical results are shown by graphical representation.

Key Words
orthotropy, elasticity, circular disk, circular ring, concentrated force

Address
Tsutsumi T, Fukushima Natl Coll Technol, Dept Civil Engn, Fukushima 9708034, Japan
Fukushima Natl Coll Technol, Dept Civil Engn, Fukushima 9708034, Japan
Univ Yamanashi, Dept Civil & Environm Engn, Yamanashi 4008511, Japan

Abstract
The paper presents theoretical and experimental investigations on three varying thickness circular cylinders, which were tested to destruction under external hydrostatic pressure. The five buckling theories that were presented were based on inelastic shell instability. Three of these inelastic buckling theories adopted the finite element method and the other two theories were based on a modified version of the much simpler von Mises theory. Comparison between experiment and theory showed that one of the inelastic buckling theories that was based on the von Mises buckling pressure gave very good results while the two finite element solutions, obtained by dividing the theoretical elastic instability pressures by experimentally determined plastic knockdown factors gave poor results. The third finite element solution which was based on material and geometrical non-linearity gave excellent results. Electrical resistance strain gauges were used to monitor the collapse mechanisms and these revealed that collapse occurred in the regions of the highest values of hoop stress, where considerable deformation took place.


Key Words
cylinders, varying thicknesses, buckling, external pressure, plasticity

Address
Ross CTF, Univ Portsmouth, Dept Mech & Mfg Engn, Portsmouth PO1 3DJ, Hants, England
Univ Portsmouth, Dept Mech & Mfg Engn, Portsmouth PO1 3DJ, Hants, England

Abstract
A relatively simple model of a buried structure response to a surface loading that can simulate a possible opening and closure of a gap between the soil and the structure is presented. Analysis of the response of small and medium scale buried roof slabs under surface impulsive loading shows that the model\'s predictions are in fairly good agreement with the experimental results. Application of the model to a study case shows the relative influence of system parameters such as, the depth of burial, the arching coefficient, and the roof thickness, on the interface pressure and on the roof displacement. This model demonstrates the effect of a gap between the structure and the soil. The relative importance of including a gap opening and closure in the analysis is examined by the application of the model to a study case. This study results show that the deeper the depth of burial, the longer the gap duration, and the shorter the duration of the initial interface impact, while the higher the soil\'s shear resistance, the higher the gap duration, and the shorter the initial interface impact duration.

Key Words
arching, buried structures, dynamic arching, gap, impact, soil-structure interaction

Address
Dancygier AN, Technion Israel Inst Technol, Dept Civil Engn, Natl Bldg Res Inst, IL-32000 Haifa, Israel
Technion Israel Inst Technol, Dept Civil Engn, Natl Bldg Res Inst, IL-32000 Haifa, Israel

Abstract
A modified constitutive model has been developed for nonlinear finite element analysis of axisymmetric reinforced concrete structures, and then implemented into an existing finite element program. By comparing with the experimental results available, the present model has been validated.

Key Words
nonlinear analysis, finite element method, axisymmetric structure, reinforced concrete

Address
Wang B, Univ Sydney, Dept Aeronaut Engn, Sydney, NSW 2006, Australia
Univ Sydney, Dept Aeronaut Engn, Sydney, NSW 2006, Australia

Abstract
The objective of this paper is to extend the use of the improved degenerated shell element to the linear and the large displacement analysis of plates and shells with laminated composites. In the formulation of the element stiffness, the combined use of three different techniques was made. This element is free of serious shear/membrane locking problems and undesirable compatible/commutable spurious kinematic deformation modes. The total Lagrangian approach has been utilized for the definition of the deformation and the solution to the nonlinear equilibrium equations is obtained by the Newton-Raphson method. The applicability and accuracy of this improved degenerated shell element in the analysis of laminated composite plates and shells are demonstrated by solving several numerical examples.

Key Words
geometrically nonlinear, laminated composite, nonconforming mode, shell element

Address
Yoo SW, Kwandong Univ, Dept Civil Engn, Kangwon 215800, South Korea
Kwandong Univ, Dept Civil Engn, Kangwon 215800, South Korea
Korea Adv Inst Sci & Technol, Dept Civil Engn, Taejon 305701, South Korea


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