Numerical Model For Dynamic Analysis Research Articles

Dynamic analysis of rock mass deformation in large underground caverns considering microseismic data

The underground powerhouse of a hydropower project is one of the most significant structures that will be permanently in use. Large scale excavation induced rock mass damage may pose a threat to the stability of the underground powerhouse. In the present study, a microseismic (MS) monitoring system was established to capture microcracks induced by excavation of the underground powerhouse caverns at the Houziyan hydropower station. Based on tempo-spatial characteristics of the MS events, the relation between MS activities and field construction was analyzed and the main damage regions were revealed. A damage-driven model considering the effect of MS source sizes is adopted for dynamic analysis of rock mass deformation of the underground caverns. The rock mass damage is simulated by a micro-mechanics-based constitutive model described by the fracture density determined by the MS source radius. A numerical model of a typical profile of the underground powerhouse was established. The MS data monitored in each bench excavation period of the underground powerhouse caverns was imported to the numerical model for dynamic analysis of deformation. The results showed that the effect of rock damage played a significant role in the rock mass deformation of the underground powerhouse during each bench excavation. The displacements of rock mass considering MS data obtained from the numerical analysis can provide better predictions for real conditions on site.

Numerical model for dynamic analysis of masonry‐infilled steel and concrete frames

AbstractA numerical model for nonlinear dynamic analysis of planar masonry‐infilled concrete and steel frames strengthened with composites is briefly presented. The model is quite simple and it can simulate main nonlinear effects of these structures. Besides modelling of nonlinear behavior of concrete, steel, masonry, plaster and soil, it can simulate nonlinearities at contact surfaces, changes in structural geometry and construction of a structure over different time phases. The model is based on a relatively small number of material parameters and intended for practical application primarily. The model is verified by using the data of the performed shake‐table tests on masonry‐infilled steel and concrete frames. Numerical results show fairly good agreement with the experimental results. This shows the potential reliability of the developed numerical model for the analysis of planar masonry structures. However, further verifications of the model and corresponding computational software are most welcome.

Numerical modelling of reinforced‐concrete structures under seismic loading based on the finite element method with discrete inter‐element cracks

SummaryThe behaviour of the earthquake excitated reinforced concrete (RC) structures up to the collapse, previously designed according to the prescriptions of Eurocode 8 cannot be fully predetermined because of the diversity of the nature of the earthquake. Thus, one needs to make a judicious choice between the two ductility classes balancing between the desired response of the structure, dimension of structural elements, costs and complexity of the design and construction. Powerful numerical models stand as significant tools to obtain more insight into the peculiarity of each structure. This paper presents a numerical model for dynamic analysis and prediction of the collapse of RC structures under the seismic loading based on finite discrete element method. The model includes several numerical algorithms which are essential for realistic description of highly non‐linear effects of these structures: cyclic crack opening‐closing mechanism based on discrete cracks, interaction between the reinforcement and concrete taken by steel strain‐slip relation, the influence of adjacent cracks to the slip of reinforcing bar, local slip of reinforcing bar because of a high plastic deformation under reversed cyclic loading, the influence of the curvature of reinforcing bar to yield stress reduction of the steel and cyclic behaviour of concrete and steel. Performance of the model was demonstrated through incremental dynamic analysis of RC wall, previously designed according to the Eurocode 8 for medium and high ductility classes. The presented results demonstrated the ability of the model for simulation of the crack patterns and collapse of these structures. Copyright © 2016 John Wiley & Sons, Ltd.

Multibody rigid models and 3D FE models in numerical analysis of transport aircraft main landing gear

Abstract Dynamic analyses of a transport aircraft landing gear are conducted to determine the effort of such a complex system and provide capabilities to predict their behaviour under hazardous conditions. This kind of investigation with the use of numerical methods implementation is much easier and less expensive than stand tests. Various 3D models of the landing gear part are defined for the multistage static FE analysis. A complete system of the main landing gear was mapped as a deformable 3D numerical model for dynamic analysis with the use of LS-Dyna code. In this 3D deformable FE model, developed in a drop test simulation, the following matters were taken into consideration: contact problems between collaborating elements, the phenomena of energy absorption by a gas-liquid damper placed in the landing gear and the response of the landing gear during the touchdown of a flexible wheel with the ground. The results of numerical analyses for the selected drop tests and the results from the experiments carried out on a real landing gear were used for verification of FE models and a methodology of the landing gear dynamics analysis. The results obtained from the various simulations of the touchdown have proved the effectiveness of the 3D numerical model and how many problems can be solved in the course of only one numerical run, e.g. geometric and material nonlinearities, a question of contact between the mating components, investigation of the landing gear kinematics, investigation of the energy dissipation problem in the whole system and the stresses influence on the structure behaviour, which can appear in some elements due to overload.