Abstract
This paper reports the result of an investigation into wave propagation in orthotropic laminated piezoelectric cylindrical shells in hydrothermal environment. A dynamic model of laminated piezoelectric cylindrical shell is derived based on Cooper-Naghdi shell theory considering the effects of transverse shear and rotary inertia. The wave characteristics curves are obtained by solving an eigenvalue problem. The effects of layer numbers, thickness of piezoelectric layers, thermal loads and humid loads on the wave characteristics curves are discussed through numerical results. The solving method presented in the paper is validated by the solution of a classical elastic shell non-containing the effects of transverse shear and rotary inertia. The new features of the wave propagation in laminated piezoelectric cylindrical shells with various laminated material, layer numbers and thickness in hydrothermal environment and some meaningful and interesting results in this paper are helpful for the application and the design of the ultrasonic inspection techniques and structural health monitoring.
Key Words
laminated piezoelectric cylindrical shells; wave characteristics curves; transverse shear and rotary inertia; thermal/humid loads.
Address
Department of Engineering Mechanics, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200030, P. R. China
Abstract
The Discrete Element Method, DEM, is increasingly used in fracture studies of non-homogeneous continuous media, such as rock and concrete. A 2D circular rigid DEM formulation, developed to model concrete, has been adopted. A procedure developed to generate aggregate particles with a given aspect ratio and shape is presented. The aggregate particles are modelled with macro-particles formed by a group of circular particles that behave as a rigid body. Uniaxial tensile and compression tests performed with circular and non-circular aggregates, with a given aspect ratio, have shown similar values of fracture toughness when adopting uniform strength and elastic properties for all the contacts. Non-circular aggregate assemblies are shown to have higher fracture toughness when different strength and elastic properties are set for the matrix and for the aggregate/matrix contacts.
Key Words
particle methods; discrete element; aggregate shape; concrete fracture.
Address
N. Monteiro Azevedo; Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, Portugal J. V. Lemos; LNEC, Av. Brasil 101, 1700-066 Lisboa, Portugal
Abstract
Experimental investigation was conducted to evaluate the seismic ductility of earthquake-experienced concrete columns with an aspect ratio of 2.5. Eight circular concrete columns with a diameter of 600 mm were constructed with three test parameters: confinement ratio, lap-splice of longitudinal bars, and retrofitting with Fiber Reinforced Polymer (FRP) materials. The objective of this research is to examine the seismic performance of RC bridge piers subjected to a Quasi static test (QST), which were preliminary tested under a series of artificial earthquake motions referred to as a Pseudo dynamic test (PDT). The seismic enhancement effect of FRP wrap was also investigated on these RC bridge piers. Six specimens were loaded to induce probable damage by four series of artificial earthquakes, which were developed to be compatible with earthquakes in the Korean peninsula by the Korea Highway Corporation (KHC). Directly after the PDT, six earthquake-experienced columns were subjected to inelastic cyclic loading under a constant axial load of 0.1fc\'Ag. Two other reference specimens without the PDT were also subjected to similar quasi-static loads. Test results showed that specimens pre-damaged by moderate artificial earthquakes generally demonstrated good residual seismic performance, which was similar to the corresponding reference specimen. Moreover, RC bridge specimens retrofitted with wrapping fiber composites in the potential plastic hinge region exhibited enhanced flexural ductility.
Key Words
RC bridge pier; seismic damage; lap splice; retrofit; transverse confinement.
Address
Young Soo Chung and Chang Kyu Park; Department of Civil Engineering, Chung-Ang University, San 40-1, Naeri, Daedeogmyeon, Anseong Gyeonggi-Do, 456-756, Korea Dae Hyoung Lee; Department of Civil Engineering, Gyeong-Do Provincial College, 947-1, Chongbokri, Yechonup, Yechongun, Gyeongsangbukdo, 757-807, Korea
Abstract
Here, the axisymmetric free flexural vibrations and thermal stability behaviors of functionally graded spherical caps are investigated employing a three-noded axisymmetric curved shell element based on field consistency approach. The formulation is based on first-order shear deformation theory and it includes the in-plane and rotary inertia effects. The material properties are graded in the thickness direction according to the power-law distribution in terms of volume fractions of the constituents of the material. The effective material properties are evaluated using homogenization method. A detailed numerical study is carried out to bring out the effects of shell geometries, power law index of functionally graded material and base radius-to-thickness on the vibrations and buckling characteristics of spherical shells.
Key Words
functionally graded; vibration; spherical shell; thermal buckling; power law index.
Address
T. Prakash and M. K. Singh; Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi - 110 016, India M. Ganapathi; Institute of Armament Technology, Girinagar, Pune - 411 025, India
Abstract
The design of structural frameworks for buildings is constantly evolving and is dependent on regional issues such as loading and constructability. One of the most promising recent developments for low to medium rise construction in terms of efficiency of construction, robustness and aesthetic appearance utilises concrete-filled steel tubular sections as the columns in a moment-resisting frame. These are coupled to rigid or semi-rigid connections to composite steel-concrete beams. This paper includes the results of a pilot experimental programme leading towards the development of economical, reliable connections that are easily constructed for this type of frame. The connections must provide the requisite strength, stiffness and ductility to suit gravity loading conditions as well as gravity combined with the governing lateral wind or earthquake loading. The aim is to develop connections that are stiffer, less expensive and easier to construct than those in current use. A proposed fabricated T-stub connection is to be used to connect the beam flanges and the column. These T-stubs are connected to the column using
Key Words
concrete-filled steel tubes; blind bolts with extensions; moment-resisting composite connection.
Address
Department of Civil and Environmental Engineering, University of Melbourne, Parkville, 3010, Australia
Abstract
This paper deals with optimal fibre orientations of symmetrically laminated fibre reinforced composite structures for maximising the fundamental frequency of small-amplitude. A set of fiber orientation angles in the layers are considered as design variable. The Modified Feasible Direction method is used in order to obtain the optimal designs. The effects of number of layers, boundary conditions, laminate thicknesses, aspect ratios and in-plane loads on the optimal designs are studied.
Key Words
laminated plates; Modified Feasible Direction method; maximization; fundamental frequency; optimal designs.
Address
Karadeniz Technical University, Department of Civil Engineering, 61080, Trabzon, Turkey
Abstract
Vibration mode localization and frequency loci veering in disordered coupled beam system are studied in this paper using finite element analysis. Two beams coupled with transverse and rotational springs are examined. Small disorders in the physical parameters such as Young
