Strut-tie method of design and possible serviceability problems: an exploration by NLFE

The strut and tie method presents a rational and consistent approach to the design of all parts in a reinforced concrete structure. With this approach, the load carrying mechanism of the structure is represented by approximating the compressive stress fields as struts, and tensile stress fields as ties. The stress in the struts and ties should not exceed the allowable compressive strength of the concrete or yield strength of the steel respectively. In the design of structures by this method there are two important issues to be addressed. The first issue is that of the visualization of an appropriate strut-tie model for a given structural system. In many structures there may be various load paths available and hence no unique strut-tie model exists. The second issue is that of validity of chosen models in relation to the serviceability and ultimate load characteristics of the resulting structure. It is important that the ductility of the structure should be maintained by insuring that crushing of concrete prior to yielding of steel is avoided at design loads. Since the strut and tie method involves a redistribution of the stresses from the elastic pattern, it is necessary to determine the extent to which that re-distribution can be allowed for, while preserving the required performance from the structure. In this work, visualization of strut-tie models was carried out using elastic finite element analysis. The resulting stress fields were used to design structures which were analysed using an in-house non-linear finite element program and also physically tested in the laboratory

Torus elements used in effective shock absorber

Energy absorbing device forces torus elements to revolve annularly between two concentric tubes when a load is applied to one tube. Interference forces can be varied by using torus elements of different thicknesses. The device operates repeatedly in compression or tension, and under problems of large onset rate tolerance or structural overload

The effect of three practice conditions on the consistency of chronic dysarthric speech

This study investigated whether it is possible for people with chronic dysarthria to adjust their articulation in three practice conditions. A speaker dependent, speech recognition system was used to compare participants' practice attempts with a model of a word made from previous recordings to give a recognition score. This score was used to indicate changes in production of practice words with different conditions. The three conditions were reading of written target words, visual feedback, and an auditory model followed by visual feedback. For eight participants with dysarthria, the ability to alter speech production was shown, together with a differential effect of the three conditions. Copying an auditory target gave significantly better recognition scores than just repeating the word. Visual feedback was no more effective than repetition alone. For four control participants, visual feedback did produce significantly better recognition scores than just repetition of written words, and the presence of an auditory model was Significantly more effective than visual feedback. Possible reasons for differences between conditions are discussed