سال:1391 | دوره: | شماره: |تعداد مقالات:9

In the first part of the present paper, a numerical method called spectral finite element method (SFEM) is presented, which is able to simulate wave scattering phenomena in plates. Combining excellent characteristics of classical finite element method (FEM) and spectral elements, SFEM not only exhibits flexibility and ease of formulation, which is a FEM character, but also exploiting high order spectral elements leads to a significant superiority over FEM from the viewpoints of solution precision and computation costs. The excellent characteristic of SFEM is its diagonal mass matrix because of the choice of the Lagrange interpolation function supported on Legendre-Gauss-Lobatto (LGL) points in conjunction with LGL integration rule. Therefore numerical calculations can be significantly efficient in comparison with the classical FEM. In this paper, a SFEM-based code is represented and verified, and then some wave propagation problems in elastic solid domains are solved using this code to show the capabilities of SFEM in solving elastodynamic problems. The problems are solved using different spectral elements, and then solution accuracy and computational costs in different solutions are compared to analytical and/or numerical solutions available in the literature. In the second part of this paper, the result of this part as forward solution is used for detection of through-thickness crack in plates.

In harsh climates, utilizing thermal insulation in the building envelope can substantially reduce the building thermal load and consequently its energy consumption. The performance of the thermal insulation material is mainly determined by its effective thermal conductivity, which is dependent on the material’s density, porosity, moisture content, and mean temperature difference. The effective thermal conductivity of insulation materials increases with increasing temperature and moisture content. Hence, thermal losses may become higher than the design values. The availability of measured data of the thermal conductivity of insulations at higher temperatures and at elevated moisture contents is poor. In this article the Artificial Neural Networks (ANN) is utilized in order to predict the effective thermal conductivity of expanded polystyrene with specific temperature and moisture content. The experimental data was used for training and testing ANN. Obtained results from the ANN method give a good agreement with experimental data.

Estimation of earthquake parameters using probabilistic method has become very common in recent years. In Iran and especially for Tehran several studies have been performed to analyze the seismic hazard. Regarding the rapid development of lifeline facilities and the construction of few tall buildings in Tehran as well as the good correlation that exists between Peak Ground Velocity (PGV) and Peak Ground Displacement (PGD) with seismic behavior of such structures, seismic velocity and displacement hazard analyses for the region can be very useful. In this study probabilistic seismic hazard analyses of PGV and PGD, for a network of 31×31 points within Tehran are conducted. For each element incorporated in analysis (e.g. seismicity parameters, attenuation relationships, etc.) various alternatives are employed. Results of hazard analysis using any combination of these alternatives are obtained using SEISRISK III program, for 4 hazard levels including site effects and combined subsequently using logic-tree approach.According to the results, for the probability of exceedence of 2, 10, 20 and 50 percent in 50 years, the maximum values of PGV are 105, 51.5, 35.4 and 18.7 cm/s, respectively. For the aforementioned hazard levels, the corresponding PGDs are 56, 20, 11.7 and 4.5 cm, respectively.

This experimental study is intended to identify the mix ratios for different grades of Geopolymer Concrete by trial and error method. A new Design procedure was formulated for Geopolymer Concrete which was relevant to Indian standard (IS 10262-2009). The applicability of existing Mix Design was examined with the Geopolymer Concrete. Two kinds of systems were considered in this study using 100% replacement of cement by ASTM class F flyash and 100% replacement of sand by M-sand. It was analyzed from the test result that the Indian standard mix design itself can be used for the Geopolymer Concrete with some modification.

In recent decades, disposal of dry sludge have been an important problem of sewage treatment plants due to environmental restrictions. The material is not usually permitted to be buried in soil or used as agricultural fertilizer because of high heavy metal contents. Some investigations performed on application of these materials in construction materials especially concrete mix designs. In this research, application of dry sludge produced in the Alborz (Qazvin) industrial/domestic sewage treatment plant in mass concrete at water to cement (w/c) ratios of 0.55 and 0.45 was investigated. The dry sludge was characterized for chemical composition (XRF analysis), crystalline phases (XRD analysis) and pozzolanic activity (Thermal gravimetery). Thereafter, it was used at 0, 5, 10, 20 and 30% of cement content in concretes. Effect of the dry sludge on compressive strength at different ages of curing 3, 7, 28 and 90 days was investigated. Besides, flexural strength, water absorption and porosity of concretes containing 20% dry sludge were measured after 28 and 90 days of curing. It was found that using dry sludge at 5, 10 and 20% caused decrease in compressive strength about 9, 14.5 and 29% in 28 days cured and 3.5, 8 and 20% in 90 days cured specimens in comparison to control specimens, respectively.

This paper presents the results of an experimental investigation on the mechanical properties of Geopolymer Concrete Composites (GPCC) containing 90% Fly ash (FA), 10% Ordinary Portland Cement (OPC), alkaline liquids and steel fibers. The study analyses the impact of steel fibres on the mechanical properties such as density, Compressive Strength, Split Tensile strength and Flexural strength of hardened GPCC. Mixtures were prepared with alkaline liquid to fly ash ratio of 0.4 with 10% of fly ash replaced by OPC in mass basis.Steel fibers were added to the mix in the volume fractions of 0.25%, 0.5% and 0.75% volume of the concrete. The influence of fiber content in terms of volume fraction on the compressive, split tensile strength and flexural strengths of GPCC is presented. Based on the test results, empirical expressions were developed to predict 28-day compressive strength, split tensile strength and flexural strength of Steel fiber reinforced GPCC in terms of volume fraction of steel fiber.

A structure is regular if its model can be represented as a product graph. Regular structures have certain properties that facilitate their optimal static and free vibration analysis. In this paper the concepts of rotational regular and translational regular structures are introduced, and using the well-known dynamic sub-structuring technique a method is proposed to relate the behavior of a translational regular structure to its rotational regular counterpart. It is shown that using the proposed method the analysis of a translational regular structure can be significantly accelerated compared to a direct method of solution.The efficiency of the proposed method in approximating the requested number of natural periods and mode shapes of a translational regular structure is demonstrated through numerical examples. The accuracy of the obtained results is compared to other approximation methods.

Construction safety management has always been a big issue in india. Though much improvement in construction safety has been achieved, india still continues to lag behind most other countries with regard to safety. The safety in construction of any organization consists of employee’s attitudes towards and perceptions of health and safety behavior. Construction safety are influenced by perceptions of risk, management, safety rules and procedures of the workers. A measure of safety management could be used to identify those areas of safety that need more attention and improvement. The dynamic nature of safety management, which has the ability to change on daily basis, means there is a great need for reliable tools that can measure safety climate. Safety management is a leading performance indicator that can provide insight into safety performance before accidents have occurred. In this paper, several construction safety techniques were used for the safety of major construction organizations across India involved in construction of Thermal power plants, Hydro power plants, Highway projects, Bridge works, Refinery works, High rise works, Pipe line works and Dam woks and its content validity was verified. These techniques are very much useful for the safety construction. Moreover, Total Construction Safety Management (TCSM) is proposed for the effective construction safety in india. Safety climate is used for the evaluation of the TCSM.

Effect of openings’ dimensions on the relative flexural behavior of adjacent piers (independent or conjugate) in perforated shear walls is addressed. 384 designed models were made and exposed to lateral loads. For middle openings, in addition to the alpha parameter in the literature, the relative flexural behavior of piers in medium-rise buildings can be predicted as function of thickness-to-length ratio of the coupling beam and the ratio of the coupling beam length to the pier length; but in high-rise buildings, it is always conjugate. For corner openings, the alpha parameter must be modified with respect to the number of stories.