Design, construction and capabilities of the Large Universal Shell Element Tester
For the safe design of new concrete structures, models based on the plasticity theory are perfectly suitable. Hence, these models have been adopted by many design codes worldwide in the last decades. However, the application of plasticity theory methods is hardly ever possible in structures built following older design codes, especially if ageing infrastructure objects need to be reassessed today in order to ensure their structural safety, usually for increased traffic intensity compared to the time of construction. The investigation of the performance of the ageing infrastructure in the context of structural safety, particularly for shear and combined loading, was the starting point to build a new testing facility in the structural laboratory at ETH Zurich, the Large Universal Shell Element Tester (LUSET).
The LUSET enables the possibility to investigate the load-deformation behaviour of large reinforced concrete plate elements under arbitrary loading conditions. This means, that the LUSET allows applying all eight independent stress resultants in any combination and independent of the loading path. Thus, the conducted experiments on shell elements allow for (i) the investigation of the deformation capacity of structural concrete subjected to in-plane loading, (ii) the exploration of the limits of applicability of the theory of plasticity to structural concrete also with low amounts of reinforcement and (iii) the critical review of current design provisions and available models.
The development of the LUSET took place over a period of more than a year and the designers tried to fulfil all the set goals for its construction. However, compromises regarding the complexity (as universal as possible), capacities (to be maximised), costs (to be minimised) and geometrical boundary conditions (as big as possible) had to be made and were weighed up against each other. This paper presents the design and construction process of the LUSET and describes its testing possibilities and capacities.