Design and seismic performance evaluation of 3D frame structures using advanced nonlinear static analysis method (granted by CNCSIS)
In recent years, non-linear inelastic analysis methods of steel and reinforced concrete frame structures has become the focus of intense research efforts because of rapid development of computer technology and the need of implementation in the new design codes, the more rational advanced analysis techniques and performance-based seismic design procedures.
With the rapid advancement of computer technology, research works are currently in full swing to develop the advanced inelastic analysis methods. In spite of the availability of some fem algorithms and powerful computer programs, the non-linear inelastic analysis of real large-scale frame structures still posses huge demands on the most powerful of available computers and still represents unpractical tasks to most designers. On the other hand, structural response to strong earthquake ground motions cannot be accurately predicted due to large uncertainities and the randomness of structural properties and ground motion parameters.
Consequently, excessive sophistication in structural analysis is not waranted.
The need for accurate yet computational efficient tools for the non-linear analysis of 3d frame structures forms the main motivation behind of this work. The research project is intended to overcome the existing inconveniences and develop an integrated system for advanced structural analysis and seismic performance evaluation of 3d steel and reinforced building frameworks with rigid or flexible connections.
Chiorean,C.G.A fast incremental-iterative procedure for ultimate strength analysis and design of composite steel-concrete cross-seections, Proceedings of International Conference STESSA 2012, Chile.
Chiorean C.G., Tarta G., Barsan G.M., Gobesz ZS, Nedelcu M., Computer based nonlinear analsysis method for seismic performance assesment of 3D frameworks, Proceedings ofInternational Conference STESSA 2012, Chile.
Chiorean, C.G., Barsan, G.M., Ciplea C, A fast iterative procedure for ultimate strength analysis and design of composite cross-seections, Proceedings of International Symposium IABSE-IASS, Taller, Longer, Lighter, London, UK.
Chiorean, C.G., Barsan G.M., Nedelcu, M., Varga S., Ciplea, C, Large deflection distributed plasticity analysis pf 3D composite steel-concrete frameworks, Proceedings of International Symposium IABSE-IASS, Taller, Longer, Lighter, London, UK.
GFAS-A finite element system for geotechnical applications (granted by
GEOSTRU SOFTWARE); Application of finite element method in Geotechnical Engineering
GFAS is a finite element package that has been developed specifically for the analysis of deformation and stability analysis in geotechnical engineering problems.
The basic program features include:
Graphical input of geometry models: The input of soil layers, structures, loads and boundary conditions is based on convenient CAD drawing procedures, which allows for a detailed modeling of the geometry contour. From this geometry model, a 2D finite element mesh is easily generated.
Automatic mesh generation: GFAS allows for automatic generation of structured and unstructured 2D finite element meshes with options for global mesh refinement. The program
contains a built-in automatic mesh generator that considerably simplifies construction of the finite element model. Both triangular (3-noded or 6-noded) and quadrilateral (4-noded or 8-noded) elements are available.
Higher-order elements: Quadratic 8-node and 6-node triangular elements are available to model the deformations and stresses in the soil.
Optimization of the matrix bandwidth to reduce the computer storage and calculation time can be performed by the program using internal re-numbering of the system equations.
Staged constructions: Complex multi-stage models can be created and analyzed such as: tunnels, excavations, embankments, soil reinforcement, etc.
Beam-column elements: The program offers a wide range of support modelling options such as liners, anchors and geotextile. The beam -column elements in either Bernoulli or Timoshenko theory are incorporated in the code and enabled the user to create complex finite element models in which both plane and line elements interact each other. Liner elements can be used in the modelling of tunnel lining or sheeting structures. Bolt types include end anchored or fully bonded. These elements can be assigned anywhere in the mesh.
Steady state flow analysis: The program includes the steady state flow analysis built right into the general program. Water pore pressures are determined as well as flow and gradient based on user defined hydraulic boundary conditions and material permeability. The water pore pressures are automatically incorporated into the finite element stress analysis.
Dynamic and seismic analysis: The program allows the users to carry out a dynamic analysis for determining the eigen values and eigen mode for construction and consequently to determine the seismic forces according with Eurocode 8.
Elasto-plastic material models: The present release offers the following models: Mohr- Coulomb and Von-Misses models for elasto-plastic behavior of plane elements. Both models are robust and simple non-linear models and are based on soil parameters that are well known in engineering practice. Both anchored and geotextile elements could have either a linear elastic or elasto-plastic behaviour.
Ballistic impact in composite materials
Research developed at DEC, Faculdade de Ciencias e Tecnologia, supported by contract 43228/EME/2001 with Fundacao para a Ciencia e Tecnologia. (Silva MA, Cismasiu C, Chiorean C.G) Cooperation with colleagues from INEGI, Porto and Comd. F. Neto from Navy School of Lisbon is gratefully acknowledged)
A combined numerical and experimental study for the analysis of Ceramic/Kevlar 29 composite armour system against 4.0g NATO 5.56 mm calibre bullet has been invetigated.
Ballistic impact was imparted with simulated fragments designed in accordance with STANAG-2920 on plates of different thickness. In all cases the projectiles impacted orthogonal to the target and the ceramic tile is not bonded to the aramidic plate.
The ballistic performance of the lightweight armour systems was examined to obtain an estimate for the V50 and the global damage of the composite plates. All estimates were performed by varying the thickness of ceramic tiles, while maintaining equal areal density of the system. Simulation predictions and trial results is demonstrated both in terms of deformation and damage of the laminates and ballistic performance. Numerical modelling was developed and used to obtain an estimate for the limit perforation velocity V50 and simulate failure modes and damage. Computations were carried out using a commercial code based on finite differences and values obtained are compared with the experimental data to evaluate the performance of the simulation. Good correlation between computational simulation and experimental results was achieved, both in terms of deformation and damage of the laminates.
Silva, M.A.G., Cismasiu, C., Chiorean, C.G., Low velocity impact on laminates reinforced with Polyethylene and Aramidic fibres. In V.P. Iu, L.N. Lamas, Y.-P. Li, and K.M. Mok, editors, Computational Methods in Engineering and Science. Proceedings of the 9th International Conference EPMESC IX, pp. 843-849, Macao, China, 25-28 November 2003. A.A.Balkema Publishers.