In addition to and often as a complement to RMA's commercial activities, the company is also involved in a number of long terms R&D projects some of which are in collaboration with commercial or academic partners.
Limit analysis is a direct approach to finding the plastic limit load for a structure or member. It adopts a rigid-perfectly plastic material model with a yield criterion appropriate for the material. There are two main approaches which appeal to the plasticity theorems. The upper bound approach seeks to find a collapse mechanism for which the plastic limit load is a minimum whereas the lower bound approach seeks to find a field of stress resultants for which the plastic limit load is a maximum. The upper bound method therefore converges from above the true value and is therefore potentially unsafe whilst the lower bound approach always provides a safe solution. RMA have developed software, Equilibrium Finite Elements (EFE) to provide lower bound solutions for plate bending problems in reinforced concrete (RC slabs) and metallic plates.
This project aims to improve the understanding of calculation of the burst speed of rotating discs and to provide updated guidance to engineers working in the field of, amongst others, turbomachinery design. The current approach is based on a 1944 study which found a correlation between the burst speed and the average hoop stress reaching the UTS of the material. Whilst it is fairly easy to demonstrate the error of this approach, it remains in use today albeit with knock-down factors to hopefully ensure that use of the formula remains safe.
RMA is acting as an Independent Technical Editor in a new NAFEMS initiative to increase the interaction between Benchmark Magazine and its readership. This initiative is called The NAFEMS Benchmark Challenge with the first challenge being published in October 2014. A Response to the Challenge will appear in the following issue of Benchmark and during the period between issues readers may collaborate and seek clarification through the Challenge Blog at NAFEMS. The challenges are going to be published in booklets by NAFEMS covering the complete challenges, responses and additional useful information for each year that the challenge continues to run.
Stress trajectories or more accurately principal stress resultant trajectories are of great value to engineers practicing in the field of reinforced concrete. For plate membrane problems the trajectories assist the engineer in finding a strut and tie model whereas for plate bending problems the principal moment trajectories give direct design information regarding the reinforcement layout.
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