Eliseu Lucena Neto

Equivalent post-buckling models for the flexural behaviour of steel connections

Abstract Analytical solutions for the evaluation of the behaviour of steel connections are presented which are able to reproduce their full non-linear behaviour. Because usual models for the analysis of steel connections consist of translational springs and rigid links whereby the springs exhibit a non-linear force–deformation response, usually taken as a bi-linear approximation, they require an incremental non-linear analysis. Using a substitute elastic post-buckling model where each bi-linear spring is replaced by two equivalent elastic springs in the context of a post-buckling stability analysis using an energy formulation, closed-form solutions are obtained for a connection loaded in bending. Application to a beam-to-column welded connection using the component (spring) characterisation of code regulations yields the same results in terms of moment resistance and initial stiffness, being additionally able to trace the full unstiffening response.

Vibration of thin shells of revolution based on a mixed finite element formulation

Abstract A modified Hellinger-Reissner functional for thin shells of revolution is presented. A mixed finite element formulation is developed from this functional which is free from line integrals and relaxed continuity terms. This formulation is applied to the problem of free vibration of spherical and conical shells. Bilinear trial functions are used for all field variables. The quadrilateral curved elements here presented satisfy the C0 continuity requirement of the functional. In all the results obtained the accuracy is quite good even for a reasonable

Stability of annular sectors and plates subjected to follower loads based on a mixed finite element formulation

Abstract A compatible mixed finite element is developed utilizing a weak variational formulation and applied to vibration and stability analysis of annular sectors and plates subjected to follower loads. The relaxed continuity requirement of the normal rotation is taken into account in this formulation. The transverse displacement and moments are interpolated by bilinear polynomials. The nodal unknowns are the field variable values at each vertex of the trapezoidal curved element. Examples are presented and their results are discussed.

Static Limit Analysis of Reinforced Soil Structures by a Simple Finite Element and Second-Order Cone Programming

TO DISCRETIZE REINFORCED SOIL STRUCTURES IN PLANE STRAIN AND PREDICT LOWER BOUNDS ON THEIR COLLAPSE LOAD, A SIMPLE THREE-NODE TRIANGULAR FINITE ELEMENT IS FORMULATED. THE ELEMENT SATISFIES THE EQUILIBRIUM EQUATIONS AND THE MECHANICAL BOUNDARY CONDITIONS IN A WEAK SENSE. A MODIFIED MOHR-COULOMB YIELD SURFACE IS ADOPTED TO DESCRIBE THE REINFORCED SOIL BEHAVIOR FROM A MACROMECHANICS POINT OF VIEW. IT IS ALSO TAKEN INTO ACCOUNT THE POSSIBILITY OF TENSION FAILURE OF THE REINFORCEMENT AND FAILURE OF THE REINFORCEMENT INTERFACE. THE STATED NONLINEAR CONVEX OPTIMIZATION PROBLEM IS CAST AS SECOND-ORDER CONE PROGRAMMING. NUMERICAL EXAMPLES ILLUSTRATE THE PREDICTIVE ACCURACY OF THE ABOVE SCHEME AS WELL AS THE EFFICIENCY AND SPEED OF AN INTERIOR-POINT METHOD TO REACH OPTIMAL SOLUTIONS.

AN EXPLICIT CONSISTENT GEOMETRIC STIFFNESS MATRIX FOR THE DKT ELEMENT

A LARGE NUMBER OF REFERENCES DEALING WITH THE GEOMETRIC STIFFNESS MATRIX OF THE DKT FINITE ELEMENT EXIST IN THE LITERATURE, WHERE NEARLY ALL OF THEM ADOPT AN INCONSISTENT FORM. WHILE SUCH A MATRIX MAY BE PART OF THE ELEMENT TO TREAT NONLINEAR PROBLEMS IN GENERAL, IT IS OF CRUCIAL IMPORTANCE FOR LINEARIZED BUCKLING ANALYSIS. THE PRESENT WORK SEEMS TO BE THE FIRST TO OBTAIN AN EXPLICIT EXPRESSION FOR THIS MATRIX IN A CONSISTENT WAY. NUMERICAL RESULTS ON LINEAR BUCKLING OF PLATES ASSESS THE ELEMENT PERFORMANCE EITHER WITH THE PROPOSED EXPLICIT CONSISTENT MATRIX, OR WITH THE MOST COMMONLY USED INCONSISTENT MATRIX.