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Issue 3, Volume 2, July 2007
Print ISSN: 1790-5044
E-ISSN: 2224-3461







Title of the Paper: Experimental research and finite element analysis on Behavior of Steel Frame with Semi-rigid Connections


Authors: Wang Xinwu

Abstract: Most steel beam-column connections actually show semi-rigid deformation behavior that can contribute substantially to overall displacements of the structure and to the distribution of member forces. Steel frame structure with semi-rigid connections are becoming more and more popular due to their many advantages such as the better satisfaction with the flexible architectural design, low inclusive cost and environmental protect as well. So it is very necessary that studying the behavior of those steel frame under cyclic reversal loading. Three full-scale specimens of angles steel using H-section members had been conducted. The specimens were subjected to cyclic reversal loading simulating earthquake effects on a steel moment-resisting force. Rotational stiffness, the carrying capacity and ductility of top-seat and web angles connections are analyzed. It is concluded that angles connections can possess the relative high stiffness, strength and excellent ductility as moment-resisting components in the seismic design of frames. At the same timem, on the basics of connections experiments the expreiment research on the lateral restistance system of steel frame structure has been completed. Two one-second scale, one-bay, two-story steel frames with semi-rigid connections under cyclic reversal loading. The seismic behavior of the steel frames with semi-rigid connections, including the failure pattern, occurrence order of plastic hinge, hysteretic property and energy dissipation, etc, was investigated in this paper. Some conclusions were obtained that by employing top –seat and two web angles connections, the higher distortion occurred in the frames, and the internal force distributing of beams and columns was changed, and the ductility and the absorbs seismic energy capability of steel frames can be improved effectively.

Keywords: semi-rigid connection, cyclic reversal loading, hysteretic property, finite element analysis, steel frame.

Title of the Paper: Heat transfer correlations for free convection from upward-facing horizontal rectangular surfaces


Authors: Massimo Corcione

Abstract: A critical review of the heat transfer data available in the literature for free convection from upwardfacing heated rectangular plates is conducted. The review is organized in the form of a table, so as to give the reader the opportunity to compare the dimensionless correlating equations presented, and the conditions under which the heat transfer data were obtained. A comparative survey of the results that may be derived at different Rayleigh numbers from these correlations is also reported. It is shown that the discrepancy among the results, which on the whole may also amount to ±50%, decreases significantly when the data are grouped according to the working fluid and the plate geometry. The following four mean heat transfer correlating equations are porposed: Nu = 1.05Ra0.215 for square plates in air, Nu = 0.9Ra0.23 for rectangular plates in air, Nu = 0.96Ra0.19 for two-dimensional infinite strips in air, and Nu = 0.175Ra0.33 for rectangular plates in water.

Keywords: Free convection; Upward-facing horizontal plates; Heat transfer correlations; Comparative survey.

Title of the Paper: Response Functions and Thermal Influence for Various Multiple Borehole Configurations in Ground Coupled Heat Pump Systems


Authors: Metka Pesl, Darko Goricanec, Jurij Krope

Abstract: Ground coupled heat pump (GCHP) utilizes the immense renewable storage capacity of the ground as a heat source or sink to provide space heating, cooling, and domestic hot water. GCHP systems are generally comprised of water source heat pumps and ground heat exchangers (GHEs). Consisting of closedloop of pipes buried in boreholes, ground heat exchangers (GHEs) are devised for extraction or injection of thermal energy from/into the ground. Despite the low energy and lower maintenance benefits of ground-source heat pump systems, little work has been undertaken in detailed analysis. Many models, either numerical or analytical, have been proposed to analyze the thermal response of vertical heat exchangers that are used in ground coupled heat pump systems (GCHP). In both approaches, most of the models are valid after few hours of operation since they neglect the heat capacity of the borehole. In this paper, we present for three various multiple borehole configurations a comparison between g-functions, which will be calculated after an analytical model of final line source and g-functions, obtain with numerical model derived from the work of Eskilson. A case study is presented to show how the ground temperature changes with time for various multiple borehole configurations.

Keywords: Geothermal Heat Exchanger; Heat Transfer, Heat Conduction, Non-dimensional Temperature Response Factors, Thermal Influence.

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