Techno Press


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CONTENTS
Volume 14, Number 5, November 2002
 

Abstract
Based on the modal coordinates of the structure, a finite-element and CQC (complete quadratic combination) method for analyzing the coupled buffeting response of long-span bridges is presented. The formulation of nodal equivalent aerodynamic buffeting forces is derived based on a reasonable assumption. The power spectral density and variance of nodal displacements and elemental internal forces of the bridge structure are computed using the finite-element method and the random vibration theory. The method presented is very efficient and can consider the arbitrary spectrum and spatial coherence of natural winds and the multimode and intermode effects on the buffeting responses of bridge structures. A coupled buffeting analysis of the Jiangyin Yangtse River Suspension Bridge with 1385 in main span is performed as an example. The results analyzed show that the multimode and intermode effects on the buffeting response of the bridge deck are quite remarkable.

Key Words
long-span bridges, aerodynamic coupling, buffeting analysis, finite-element and CQC method, multimode and intermode, Jiangyin Yangtse River Suspension Bridge

Address
Ding QS, Tongji Univ, State Key Lab Disaster Reduct Civil Engn, Shanghai 200092, Peoples R China
Tongji Univ, State Key Lab Disaster Reduct Civil Engn, Shanghai 200092, Peoples R China

Abstract
Application of piezoceramic materials in actuation and sensing of vibration is of current interest. Potential and more popular applications of piezoceramics are probably in the field of active vibration control. However, the objective of this work is to investigate the effect of shunted piezoceramics as passive vibration control devices when bonded to a host structure. Resistive shunting of a piezoceramic bonded to a cantilevered duralumin beam has been investigated. The piezoceramic is connected in parallel to an electrical network comprising of resistors and inductors. The piezoceramic is a capacitor that stores and discharges electrical energy that is transformed from the mechanical motion of the structure to which it is bonded. A resistor across the piezoceramic would be termed as a resistively shunted piezoceramic. Similarly, an inductor across the piezoceramic is termed as a resonantly shunted piezoceramic. In this study, the effect of resistive shunting on the nature of damping enhancement to the host structure has been investigated. Analytical studies are presented along with experimental results.

Key Words
vibration control, piezoceramic, resistive shunting

Address
Kandagal SB, Indian Inst Sci, Dept Aerosp Engn, Aeroservoelast Lab, Bangalore 560012, Karnataka, India
Indian Inst Sci, Dept Aerosp Engn, Aeroservoelast Lab, Bangalore 560012, Karnataka, India

Abstract
The use of the epoxy pressure injection technique to rehabilitate reinforced concrete beam-column joints damaged by strong earthquakes is investigated experimentally and analytically. Two one-half-scale exterior beam-column joint specimens were exposed to reverse cyclic loading similar to that generated from strong earthquake ground motion, resulting in damage. Both specimens were typical of new structures and incorporated full seismic details in current building codes. Thus the first specimen was designed according to Eurocode 2 and Eurocode 8 and the second specimen was designed according to ACI-318 (1995) and ACI-ASCE Committee 352 (1985). The specimens were then repaired with an epoxy pressure injection technique. The repaired specimens were subjected to the same displacement history as that imposed on the original specimens. The results indicate that the epoxy pressure injection technique was effective in restoring the strength, stiffness and energy dissipation capacity of specimens representing a modem design.

Key Words
beams (supports), columns (supports), earthquakes, epoxy resins, joints (functions), reinforced concrete, repairs

Address
Aristotle Univ Thessaloniki, Sch Engn, Dept Civil Engn, Div Struct Engn, POB 482, GR-54006 Thessaloniki, Greece

Abstract
This paper presents a method for predicting premature separation of carbon fiber reinforced plastic (CFR-P) plates from strengthened steel beams. The fracture criterion based on material-induced singularity is formulated in terms of a singular intensity factor. Static test on double strap joints was selected to provide the critical stress intensity factor in the criterion because good degree of accuracy and consistency of experimental data can be expected compared with the unsymmetrically loaded single lap joints. The debond/separation loads of steel beams with different CFRP lengths were measured and compared with those predicted from the criterion. Good agreement between the test results and the prediction was found.

Key Words
fracture, stress singularity, strengthening, CFRP, steel beams, bridges, bi-material wedges, double strap joints

Address
Lenwari A, Chulalongkorn Univ, Dept Civil Engn, Bangkok 10330, Thailand
Chulalongkorn Univ, Dept Civil Engn, Bangkok 10330, Thailand
Kyoto Univ, Dept Civil Engn, Kyoto 6068501, Japan

Abstract
Based on the Mindlin plate theory, a refined discrete 15-DOF triangular laminated composite plate finite element RDTMLC with the re-constitution of the shear strain is proposed. For constituting the element displacement function, the exact displacement function of the Timoshenko\'s laminated composite beam as the displacement on the element boundary is used to derive the element displacements. The proposed element can be used for the analysis of both moderately thick and thin laminated composite plate, and the convergence for the very thin situation can be ensured theoretically. Numerical examples presented show that the present model indeed possesses the properties of higher accuracy for anisotropic laminated composite plates and is free of locking even for extremely thin laminated plates.

Key Words
laminated composite plate, displacement function of Timoshenko\'s laminated beam, shear locking

Address
Ge ZJ, Dalian Univ Technol, Key Labs State Struct Anal Ind Equipment, Dalian, Peoples R China
Dalian Univ Technol, Key Labs State Struct Anal Ind Equipment, Dalian, Peoples R China

Abstract
This paper presents an efficiency of various non-conforming (NC) modes in development of a series of new finite elements with the special emphasis on 4-node quadrilateral elements. The NC modes have been used as a key scheme to improve the behaviors of various types of new finite elements, i.e., Mindlin plate bending elements, membrane elements with drilling degrees of freedom, flat shell elements. The NC modes are classified into three groups according to the \'correction constants\' of \'Direct Modification Method\'. The first group is \'basic NC modes\', which have been widely used by a number of researchers in the finite element communities. The basic NC modes are effective to improve the behaviors of regular shaped elements. The second group is \'hierarchical NC modes\' which improve the behaviors of distorted elements effectively. The last group is \'higher order NC modes\' which improve the behaviors of plate-bending elements. When the basic NC modes are combined with hierarchical or higher order NC modes, the elements become insensitive to mesh distortions. When the membrane component of a flat shell has \'hierarchical NC modes\', the membrane locking can be suppressed. A number of numerical tests are carried out to show the positive effect of aforementioned various NC modes incorporated into various types of finite elements.

Key Words
basic non-conforming modes, Direct Modification Method, hierarchical non-conforming modes, higher order non-conforming modes, membrane locking

Address
Choi CK, Korea Adv Inst Sci & Technol, Dept Civil & Environm Engn, Taejon 305701, South Korea
Korea Adv Inst Sci & Technol, Dept Civil & Environm Engn, Taejon 305701, South Korea

Abstract
In this paper, a complete solution is presented for dynamic plastic response of a rigid, perfectly plastic hinged-free beam, of which one end is simply supported or hinged and the other end free, subjected to a transverse strike by a travelling mass at an arbitrary location along its span. The governing differential equations are expressed in non-dimensional forms and solved numerically to obtain the instantaneous deflection of the beam and the plastic dissipated energy in the beam. The dynamic behavior for a hinged-free beam is more complicated than that of a free-free beam. It transpires that the mass ratio and impact position have significant influence on the final deformation. In the aspect of energy dissipation, unlike simply supported or clamped beams for which the plastic deformation consumes almost the total input energy, a considerable portion of the input energy would be transferred as rigid-body motion of hinged-free beam, and the energy dissipated in its plastic deformation is greatly reduced.

Key Words
hinged-free beam, dynamic plastic response, impact, plastic dissipated energy

Address
Zhang Y, Beijing Univ Aeronaut & Astronaut, Solid Mech Res Ctr, Beijing 100083, Peoples R China
Beijing Univ Aeronaut & Astronaut, Solid Mech Res Ctr, Beijing 100083, Peoples R China
China Agr Univ, Mech Mat Grp, Beijing 100083, Peoples R China


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