Dynamic sensitivity of multi-block stacks subjected to pulse base excitation - experimental evidence and non smooth contact dynamics simulations

Experimental and computational dynamic sensitivity study of Multi-Block Stacks subjected to Pulse Base Excitation is considered. Advanced non contact optical measuring technique based on the GOM Aramis and Pontos systems, as well as the corresponding processing software (displacement history of control sensor points, with a high resolution high speed cameras) have been applied to replace conventional displacement measuring systems and accelerometers. The Non Smooth Contact Dynamics (NSCD) time integration simulation framework SOLFEC http://code.google.com/p/solfec/ is adopted here for comparative NSCD analyses, including a sensitivity study on interface characteristics, as a validation process. Series of test experiments were conducted and recorded on a bespoke platform with and without lateral constraints in the Oxford Impact Engineering Laboratory and Rijeka University Structural Dynamics Laboratory for an extensive series of controlled pulse base excitation tests of multi block stacks configurations. Impact is generated by a pin-ball mechanism with spring and a wooden projectile, attached to an optical bench. For the NSCD simulations the base was subjected to a constant acceleration over a finite time, thereby facilitating the characterisation of multi block stacks tumbling modes of failures (global or partial), as a function of stop gap distance. Creation of well documented benchmarks for the validation of simulation paradigms for discontinuous media will be extremely valuable for researchers and code developers (non smooth contact dynamics, discrete elements, discontinuous deformation analysis), as well as for safety case engineers and industry regulators

Dynamic sensitivity of multi-block stacks subjected to pulse base excitation - experimental evidence and non smooth contact dynamics simulations

Experimental and computational dynamic sensitivity study of Multi-Block Stacks subjected to Pulse Base Excitation is considered. Advanced non contact optical measuring technique based on the GOM Aramis and Pontos systems, as well as the corresponding processing software (displacement history of control sensor points, with a high resolution high speed cameras) have been applied to replace conventional displacement measuring systems and accelerometers. The Non Smooth Contact Dynamics (NSCD) time integration simulation framework SOLFEC http://code.google.com/p/solfec/ is adopted here for comparative NSCD analyses, including a sensitivity study on interface characteristics, as a validation process. Series of test experiments were conducted and recorded on a bespoke platform with and without lateral constraints in the Oxford Impact Engineering Laboratory and Rijeka University Structural Dynamics Laboratory for an extensive series of controlled pulse base excitation tests of multi block stacks configurations. Impact is generated by a pin-ball mechanism with spring and a wooden projectile, attached to an optical bench. For the NSCD simulations the base was subjected to a constant acceleration over a finite time, thereby facilitating the characterisation of multi block stacks tumbling modes of failures (global or partial), as a function of stop gap distance. Creation of well documented benchmarks for the validation of simulation paradigms for discontinuous media will be extremely valuable for researchers and code developers (non smooth contact dynamics, discrete elements, discontinuous deformation analysis), as well as for safety case engineers and industry regulators

A fully generalised, coupled, multi-phase, hygro-thermo-mechanical model for concrete

A detailed and fully generalised (3D) hygro-thermo-mechanical model for concrete is presented. The model captures the complex behaviour of this composite material through the adoption of a multi-phase material description which captures the strong coupling between the separately considered solid, liquid and gas fields. Heat and mass transport of the fluid phases are modelled in a coupled manner such that an accurate description of the fluid transport processes in concrete is possible, illustrating in particular the redistribution of liquid and the increases in vapour content and pore pressure associated with the application of elevated temperatures. The mechanical behaviour of the solid skeleton is modelled by way of an isotropic thermo-mechanical damage model in which the degradation of the material due to both mechanical and thermal loading is taken into account. Coupling with the hygro-thermal components of the model allows for the effects of material degradation on mass transport to be captured. The model is validated over a wide range of capability through the reproduction of two sets of separate and differing experimental results concerning isothermal drying and high temperature problems. For these two problems, the model is shown to reproduce accurately values for total moisture mass losses, moisture distributions, temperatures and pore pressures developed in both time and space in various types of both ordinary and high performance concrete materials. A further parametric study is then presented where the model is used to investigate the roles of various mechanical behaviours in the overall hygro-thermo-mechanical response of the concrete under high temperature conditions. The implications of the results are discussed in detail