Finite Element Modeling of Cyclic Behavior of a Reinforced Concrete Chimney Section Sami
In this study, a numerical model was presented to simulate the experimental behavior obtained for a reinforced concrete chimney section. The purpose of the previous experimental investigation conducted for the chimney section was to evaluate the effect of large openings on the cyclic response in order to reveal the performance of such structures under seismic loads. A detailed finite element model of the chimney section was constructed and all of the reinforcements of the chimney were directly taken into account by line element representations. The volume of the concrete chimney shell was modeled with hexahedral elements. A bi-linear material model was used for the reinforcements. A crucial step in the finite element approach was to employ a constitutive material model that took the multi-axial state of stress and confinement effects in concrete into account. The Winfrith concrete material model of the commercial LS-Dyna structural code was chosen for the shell of the chimney section. Comparisons of the results of the finite element study with the experimental measurements showed a good agreement for the base moment-displacement response and crack formations around the opening regions of the chimney section.
The Cyclic Behaviour of Reinforced Concrete Chimney Sections with and without Openings
The most vulnerable feature of most existing tall reinforced concrete chimneys when subject to severe earthquake excitation is the relative weakness of the sections around the openings near the chimney base. This paper documents an experimental study undertaken to investigate the cyclic behaviour of typical chimney sections with openings orientated to be bending critical and shear critical and the results are compared with previous tests with no openings. Significantly, no such cyclic tests have been previously been completed. The experimental results presented include; failure mode, over-strength factor, ultimate curvature, available ductility, hysteretic behaviour and strain distribution and the results are compared with some predictive analytical section models and design guidelines. The research indicated that chimney sections with openings were not brittle, but were significantly less ductile than sections without openings. The paper is relevant for both assessing existing chimney stacks and for the design of new chimneys in the vicinity of openings.
Simulation and control of hybrid renewable energy system connected to the grid
This paper presents a control and simulation of hybrid renewable energy system connected to the grid. The studied system includes a photovoltaic panel, synchronous permanent magnet generator based wind turbine, and a battery for storage energy. The PV array and wind systems are connected to the common DC bus by a boost converter. The battery is connected by a bi-directional DC/DC converter, and then integrated into the AC utility grid via a common DC/AC inverter. In order to extract the maximum energy, a simulation study has been carried out according to the meteorological conditions (wind speed and variable solar irradiance) while maintaining power quality at a satisfactory level. In order to capture the maximum power, a MPPT algorithm is applied for both wind turbine and photovoltaic panel. The modeling and simulation of the whole system has been performed under Matlab/Simulink environment. The obtained results show that the current and the voltage of grid side are sinusoidal and alternative forms, and the power injected to the grid is around the power produced by the hybrid system.