Markku Tuomala

Testing and design of gravity-loaded steel purlins restrained by sheeting

Abstract This paper is prepared on the basis of a study, the aim of which was to determine experimentally the design parameters for a set of thin-walled steel purlins with C, Z, Zeta and Hat-cross-sections. In our study, special attention was paid to the structural behaviour of the purlin at the internal support, when the free flange was compressed and when the upper flange of the purlin was torsionally restrained by sheeting. Also, the numerical modelling of continuous purlins is considered. An example of the normalized design ( M / M C,Rd θ )-relation and test results for combined action bending moment and support reaction are given. The utilization of a softening moment resistance and a corresponding ideally plastic calculation method are briefly described.

Numerical and Experimental Studies on Impact Loaded Concrete Structures

An experimental set-up has been constructed for medium scale impact tests. The main objective of this effort is to provide data for the calibration and verification of numerical models of a loading scenario where an aircraft impacts against a nuclear power plant. One goal is to develop and take in use numerical methods for predicting response of reinforced concrete structures to impacts of deformable projectiles that may contain combustible liquid (“fuel”). Loading, structural behaviour, like collapsing mechanism and the damage grade, will be predicted by simple analytical methods and using non-linear FE-method. In the so-called Riera method the behavior of the missile material is assumed to be rigid plastic or rigid visco-plastic. Using elastic plastic and elastic visco-plastic material models calculations are carried out by ABAQUS/Explicit finite element code, assuming axisymmetric deformation mode for the missile. With both methods, typically, the impact force time history, the velocity of the missile rear end and the missile shortening during the impact were recorded for comparisons.Copyright

Modified Rosenbrock Method for Computing the Transient Response of Nonlinear Structures

A desirable feature of implicit integration methods for structural dynamics problems is the numerical damping of spurious high-frequency oscillations in the solution. For example, the method of Hilber et al.[1] used in some commercial finite element packages offers the user a parameter α to control the tradeoff between numerical damping and accuracy.

Branch switching from coincident bifurcation points

The definition of the solution set of a general non-linear structural problem depending on one external parameter is considered. Path-following techniques and singular point locating and identifying methods are reviewed, followed by so-called branch-switching methods used to detect secondary equilibrium paths associated with m-fold bifurcation points. Two methods introduced by Keller [[1]] and Kearfott [[2]] are considered, and their performance when used together with the non-linear finite element method is verified.