سال:1388 | دوره: | شماره: |تعداد مقالات:9

Large spans always fascinated architects and engineers. Domes provide an easy and economic method of roofing large areas with minimum material in all forms of space structures. Wind loads have significant proportion of the total load to act on such structures that’s why the magnitude and distribution of the resultant pressures must be considered. To overcome this problem, the concept of Artificial Neural Network is adopted to find wind induced pressure coefficients for spherical domes of different span/height ratio. This paper aims to use this neural network application in steel space structures. Here, pressure measurements had been made on a large dome roof model with Computational Fluid Dynamics (CFD) technique and the data generated were used as the training sets to develop artificial neural network models to recognize the input–output patterns.

In this paper, a new methodology is presented to study the corrosion of RC structures in chloride laden environments under concerned uncertainties. To deal with the involved uncertainties, fuzzy random variables are exploited. An effective computational procedure named as a-level optimization is also introduced and utilized to analysis the FR fundamental equations of corrosion process. The proposed system is applied to predict the various life cycles of corrosion affected RC structures. Moreover, an illustrative example is presented to demonstrate the applicability of proposed method in service life assessment of the RC beams.

An analytical method is presented based on the kinematic theorem of limit analysis applied to the stability of reinforced slopes under the seismic loading condition. The rate of external work is due to soil weight and inertia force induced by the earthquake and the only contribution to energy dissipation is that provided by the reinforcement. In the present analysis a rotational failure mechanism is considered. The proposed method considered a log-spiral failure surface. In order to verify the proposed method of analysis; two published case studies Clouterre Test Wall No. 1 and the 4.5 m high wall known as Eparris Wall, built to retain a little cut in plastic clay are utilized. The probable failure surface and the factor of safety obtained by the proposed method are found to be in good agreement with the published test results. Finite element numerical modeling by FLAC is done for these test walls. Numerical analysis is found to be good agreement with the published results and also with field observations.

A storey element, which can simulate one storey of the frame-shear wall structure, is established by simply summing the rigidity matrixes of the frame and wall. The internal forces and displacements of the frame-shear wall structures for various rigidity characteristics with the constant stiffness under various kinds of loads are calculated by the beam element method, storey element method and analytical formulas. The internal forces and displacements with the variable stiffness along the height under uniformly distributed load are calculated by the beam element method and storey element method. In comparison with the beam element method, the storey element method can remarkably reduce the volume of input, output data and calculation, the error is less than 8.3%.

Fragility function of structures is the major requirement of seismic loss estimation which is widely used in the seismic risk management. In this paper, firstly, a comprehensive and simplifies stochastic methods are presented for development of analytical fragility functions. Secondly, the effect of damage threshold uncertainty on fragility functions is estimated. It is shown that the results of the method are almost comparable with the result of previous studies and the effect of uncertainty of damage state on the deviation of fragility function in the lower intensity of ground motion is high which gradually decreases.

Relationship between thermal conductivity (lt) and density (r) of mineral wool insulations has a wide band of measured data, follows some form of median curve which is called reference curve. Departures from this curve are mainly due to the fact that manufacturing conditions change. But the deviation from the curve should be in a limited range because it will affect the quality conformity. With finding lt= f(r) as a reference curve and using routine test results it is possible to note the changes in quality of the products. On the other hand lt may be evaluated indirectly using r measurements and the established reference curve for a specific production line. For finding the suitable model for lt = f(r), a large amount of data was studied in this article. Different semi-empirical models were presented and statistically compared with the experimental results to evaluate the best one.

The structures subjected to earthquake, nuclear blast forces etc., demand more ductility to absorb strain energy. The limited ductility of concrete also affects the performance of structure under static loads. Almost all codes of practice around the world stipulate only the ductile failure of structural components, which is the major drawback of the over reinforced concrete beams. It is well known that the confinement of concrete increases the compressive strength and ductility, the latter to a larger degree. Such concrete is called ductile concrete. The limitations on the spacing of stirrups will restrict the improvement in the ductility of concrete confined by the stirrups. The use of Steel Fiber Reinforced Concrete along with the stirrup confinement in the possible plastic hinging regions may enhance the overall ductility of concrete structures. Such engineered application of SFRC may be termed as Engineered Steel Fiber Reinforced Concrete (ESFRC).This paper presents an experimental investigation to study the behaviour of ESFRC by varying the volume percentage content of steel fiber. Four rectangular reinforced concrete beams, with the steel fiber reinforced concrete in critical sections along with the stirrup confinement, have been tested. The findings of the investigation indicate that up to about 80 percent of ultimate strength, the behaviour of ESFRC beams was similar to that of beams with rectangular tie confinement. The effect of the steel fiber was felt prominently beyond the post ultimate stage. The ductility is increased due to increase in percentage of fiber content.

The main objective of the present work is to study the effect of mixing of hair fiber on mechanical properties of fly ash. The hair fiber was mixed in fractions of 0.00, 1.00, 1.50, 2.00 & 2.50% respectively. Portland cement production is under critical review due to high amount of carbon dioxide gas released to the atmosphere. Kumar [1] reported that in recent years, an attempt to increase the utilization of Fly ash to partially replace the use of Portland cement in concrete has been gathering momentum. Most of this by product material is currently dumped in landfills, thus creating a threat to the environment. About 82 utility thermal power plants (TPPs) in the country contribute nearly 70% of total power generation, which in turn, produced 108 million tonne of fly ash during 2004. The annual generation of fly ash is projected to exceed 175 million tonne per annum by 2012 AD.In this struggle scientists and engineers, especially civil engineers, are playing a remarkable role. A number of studies have been carried out to determine the effect on the physical properties of soil and fly ash with and without Lime. However, very few studies have been done to investigate the effect of randomly oriented hair fiber on fly ash based Hollow block. In this paper, results of an experimental study have been presented to determine the effect of randomly oriented hair fiber on mechanical properties of fly ash based hollow block.

Iran Strong Motion Network started its activities in 1973 and running by Building and Housing Research Center since 1981. At the date of this study ISMN consisted of more than 1103 digital (SSA-2) and 15 analog (SMA-1) accelerographs. The accelerograms of different earthquake, are downloaded, controlled, processed, and then added to the comprehensive data bank, which is very useful for scientists and engineers in the field of engineering seismology and earthquake engineering.Here, the most important earthquakes are briefly described. More information is presented in Appendix I and also available on http://www.bhrc.ac.ir.