Athol J. Carr

FINITE ELEMENT ANALYSIS OF LAMINATED SHELLS OF REVOLUTION WITH LAMINATED STIFFENERS

Abstract A finite element analysis of orthogonally stiffened shells of revolution has been presented by combining a recently proposed shell of revolution element and a curved beam element. These two elements are isoparametric elements in which the effects of shear deformation and rotary inertia have been taken into account. They are meant to be used for arbitrarily laminated structures and are based on the higher-order theories presented recently by Bhimaraddi for plates, shells and beams.

Shake-Table Tests of Confined-Masonry Rocking Walls with Supplementary Hysteretic Damping

A shake-table investigation is conducted on a 40% scale model frame-wall system to validate the concept of rocking walls as primary seismic systems. The rocking wall concept was implemented on confined masonry walls, but the findings can be extended to any rocking wall system. As the inherent damping of this system is low, a pair of supplemental steel hysteretic energy dissipating dampers is used at the base of the wall. It is concluded that with careful detailing, damage is not only eliminated but the structure re-centers itself following a large earthquake.

Generalized finite element analysis of laminated curved beams with constant curvature

Abstract A 24-dofisoparametric finite element has been presented for the analysis of generally laminated curved beams. The effects of shear deformation and rotary inertia have been accounted for using the shear deformation theory which employs nonlinear shear strain variation across the section. Thus it is not necessary to specify the shear correction factors in the present element. The torsional response has been incorporated according to the elementary theory of torsion. It is shown that for certain unsymmetrically laminated curved beams the in-plane and out-of-plane motions are coupled. The numerical results presented illustrate the performance of the element and the effect of coupling.

A shear deformable finite element for the analysis of general shells of revolution

A 64-dof isoparametric quadrilateral finite element is presented for the analysis of generally laminated shells of revolution. The effects of shear deformation and rotary inertia are accounted for by using shear deformation theory that employs the parabolic shear strain variation across the thickness. The classical thin shell theory is the special case of shear deformation theory used in the present study. Thus, the thin shell element also can be obtained from the present thick shell element by simply having the displacement parameters (u1 and v1,) associated with the shear rotations as zeros. The numerical results presented illustrate the performance of the element and the effects of shear deformation.

The Behavior of Bearings Used for Seismic Isolation under Shear and Axial Load

The investigation described in this paper looked at both laminated elastomeric bearings and lead-rubber bearings in order to obtain a better understanding of the real bearing behavior under the combined action of shear and axial loads when used in a seismic-isolation system. In particular, the investigation focused on the distributions of vertical pressure on the bearing faces and the degree of lift-off of the edges of the bearings as the shearing displacement and the angle of rotation increased.

Compression behaviour of bridge bearings used for seismic isolation

A large number of seismic isolation systems have been developed since the early 1970s. They are basically a combination of elastomeric bearings and energy dissipators. Elastomeric bearings can lengthen the period of free vibration of a structure and play an important part in seismic isolation systems. As bridge bearings they have been investigated since 1940, but now they are being used in conjunction with lead plugs that can provide hysteretic damping and energy dissipation. The investigation described in this paper looked at both laminated elastomeric bearings and lead-rubber bearings in order to obtain a better understanding of the real bearing behaviour under compression load when used in a seismic-isolation system. In particular, the investigation focused on the vertical pressure distributions on the bearing faces and the prediction of compressive stiffness according to current design codes.

DEVELOPMENT OF A DESIGN PROCEDURE FOR BRIDGES ON LEAD-RUBBER BEARINGS

Abstract This paper presents a design method that is based on a parametric study of the response of bridge superstructures supported on lead-rubber bearings and subjected to El Centro 1940 N/S component and the 1966 Parkfield earthquakes. The effect of parameters such as lead plug sizes and aspect ratio, bearing thickness and yield strength, pier, abutment and superstructure stiffnesses, and different earthquake records, were investigated. Questions addressed included ‘when should lead-rubber bearings be used?’ and ‘can they be used to redistribute seismic forces between piers and abutments?’. The results of the time-history analyses answered these questions and showed clear trends. These are used in the design procedure, which the authors believe to be more straight-forward and conceptually clearer than the present design procedures.

ELASTICAS AND BUCKLING LOADS OF SHEAR DEFORMABLE TAPERED COLUMNS

This paper deals with the geometrical nonlinear analyses of buckled columns. Differential equations governing the elasticas of buckled columns are derived, in which both the effects of taper type and shear deformation are included. Three kinds of taper types are considered, i.e. breadth, depth and square tapers. Differential equations are solved numerically to obtain the deflection of elasticas and the buckling loads of such columns. Both clamped ends and hinged ends are considered. The effects of shear deformation on the deflection of elasticas of buckled columns and on the buckling loads of columns are investigated extensively. The buckling load equations for uniform columns are expressed as a function of the implicit shear effect. Experimental studies are presented that complement the theoretical results of nonlinear responses of the elasticas.

SOME TEXTILE APPLICATIONS OF FINITE-ELEMENT ANALYSIS. PART II: FINITE ELEMENTS FOR YARN MECHANICS

The concepts of modal decomposition developed in an earlier paper are used to produce a three-dimensional element for aligned fibre assemblies. The element degrees of freedom are introduced and the chosen mode shapes of the element demonstrated. The finite element is tested by using simple material-property assumptions, and the element is verified against a theoretical model of the twisting of a single fibre about a solid core. The element is then verified qualitatively by modelling realistic yarn situations, and the resultant deformation plots are presented.

Elemental damping formulation: an alternative modelling of inherent damping in nonlinear dynamic analysis

To date, nonlinear dynamic analysis for seismic engineering predominantly employs the classical Rayleigh damping model and its variations. Though earlier studies have identified issues with the use of this model in nonlinear seismic analysis, it still remains the popular choice for engineers as well as for software providers. In this paper a new approach to modelling damping is initiated by formulating the damping matrix at an elemental level. To this regard, two new elemental level discrete damping models adapted from their global counterparts are proposed for its application in nonlinear dynamic analysis. Implementation schemes for these newly proposed models using Newmark incremental method and revised Newmark total equilibrium method is outlined. The performance of these proposed models, compared to existing models, is illustrated by conducting nonlinear dynamic analyses on a four story RC frame designed to Eurocodes. The incremental dynamic analysis study presented in the paper illustrates the fact that both the proposed models seem to produce more reliable results from an engineering perspective in comparison to the global models. It is also shown that the proposed elemental damping models lead to smaller and more realistic damping moments in the plastic hinges. Furthermore, these models could be easily included in existing software frameworks without adding noticeably to the computational effort. The computation time required for these models is approximately equivalent to the one required when using the tangent Rayleigh damping matrix with constant coefficients.