AMIRKABIR JOURNAL OF CIVIL ENGINEERING (AMIRKABIR)
Year:2012 | Volume:43 | Issue:2|Papers Count:8

In this article, a new finite volume solver which uses a matrix free Galerkin approach for explicit solution of weak form of two dimensional Cauchy equilibrium equations is introduced. This method is suitable for linear structural problems for which two-dimensional assumption can be applied. In this work, the two dimensional equations of motion governing the plane stress problems are solved on unstructured triangular meshes. In order to present the accuracy of computed results of introduced method, a plate test case under distributed load with available computed results from other numerical methods are utilized. The results presented in terms of stress and strain contours and compared with the available analytical solution.

Pseudo-static analysis is a common and simple method for the evaluation of seismic stability in embankment dams. Selection of the horizontal Pseudo-static coefficient is a primary step for evaluation of seismic behavior of embankment. Previous researchers and design manuals of embankment dams often suggest constant values for selecting the seismic coefficient regardless of site seismicity and the dynamic characteristics of the structures. In order to evaluate geometric effect, pseudo-static, static and dynamic analyses of the Masjed Soleiman dam With Finite Element Method performed and then precise a new equation to determine the pseudo-static coefficient of earth dams. In this equation, variations in acceleration for height of the dam, considered linear and the gradient of this line related to the geometrical characteristics of the dam body, soil stiffness and damping values. Result of this research imply that with increasing height of dam, decrease gradient of acceleration and with increasing slope of dam, increase gradient of acceleration.

Sulfate attack is one of the most important problems concerning the durability of concrete structures. In this paper, the sulfate resistance of concrete and mortar specimens made from ordinary Portland cement containing limestone powder was studied. Strength reductions and mass changes of concrete specimens immersed in 10% Na2SO4 and MgSO4 solutions and Expansion of mortar prisms immersed in 5% and 10% Na2SO4 and MgSO4 solutions were monitored.It was observed that compressive strength decreases with the limestone replacement percent and also, deterioration is severer, the higher the concentration content sulfate.

In this paper, a numerical investigation on behavior of concrete in filled columns using nonlinear finite element method is done. Numerical results are verified using experimental results. Behavior of rolled steel tubes witch are filled with concrete of different strength on the axial applied loads is present. Effect of steel tubes thickness and confining stress are considered and the results are compared with concrete columns. The results showed that with increasing thickness of steel tubes, axial load capacity and confinement stress and ductility is increased and with increasing the concrete strength, confining stress and ductility is reduced. Specimens with different concrete strength of 30, 60, 80 MPa and different D t ratio are analyzed and all the specimens have the same length of 300 mm. The main objects are: 1) to investigate effect of prominence on axial load capacity.2) to investigate the effect of different parameters like thickness of steel tubes, friction coefficient and the ratio of prominence area over total perimeter area. 3) to investigate effect of loading (i.e. loading concrete only or loading concrete and steel tubes simultaneous.4) to investigate the ductility of columns.

Seepage analysis in the upper reservoir of the Kurdistan Azad pumped storage dam with a volume of 3800000 cubic meter is an important and effective parameter for selecting of the optimized sealing method. More than 60% of the Lugeon test results show very permeable behavior. In order to calculate seepage discharge from the reservoir with no sealing element, analytical and numerical methods are used. Results of the analytical method and finite element numerical method (SEEP/W software) shown the amount of the seepage discharge in steady state flow is equal to 112600 and 11500 m3/day, respectively. Unsteady state numerical method (UDEC software) showed initial seepage discharge about 1700000 m3/day, decreasing to 112400m3/day while approaching to steady state conditions.3D seepage modeling using Seep3D software shows about 118000 m3/day seepage discharge, means 3% of the total reservoir volume. Analysis show the necessity of sealing in the reservoir. After feasibility study, the geomembrane method was suggested as the best sealing method with the implementation cost of 20 billion Rls.

Nowadays formaldehyde is used in many industrial activities such as adhesives, resins and paper producing, pharmaceutics, and also a number of general and commercial activities like some hospital services, dead burial and providing the sanitation of some public places like garrisons. In this research aerobic treatment of formaldehyde in MBBR compared with SBR in the influent COD range between 0 to 2500 mg/L. According to the results, SBR under serial operation was better than MBBR. These results showed the removal efficiency of influent CODs less than 200 mg/L was 100% and for CODs between 200 to 450 mg/L was 90% after 48 hours. In this study, it took 4 days in CODs less than 1500 mg/L and 4 to 6 days in CODs between 1500 to 2500 mg/L for reactors to reach steady state condition. In kinetic study, related coefficients followed Stover-Kincannon second order model.13C-NMR spectroscopy showed that formaldehyde and urea was converted to N- {[(amino-carbonyl) amino] methyl} urea. It was determined formaldehyde was polymerized in ordinary temperature and all molecules including carbons were degraded.

Despite today's huge improvements in construction engineering and management methods, construction projects are considered as the riskiest workplaces. The work cure at this projects sites more than others are at risk. Hence, special attention to safety in these workplaces is needed to reduce the rate of accidents.However, the project stakeholders' commitments to safety requirements are not evident at the regular arrangements. The aim of this study is to analyze the most common type of accidents and their consequences identified based on statistical and surveys in Iran construction projects and especially in Isfahan. Results shows that in building workplaces, human and organizational factors are the main sources of accidents. It also shows that project parties including owner, consultant and contractor are not familiar with safety rules and regulations and the lack of dedication, conviction and adequate supervision make this conditions worst.

A large amount of rubbers are produced in the world, and the disposal of these waste materials is not feasible, as the rate of decomposition for tyre is very slow. These waste material produce big environmental pollution, therefore optimum use of them has become a necessity. These kinds of trashes can be used for improving some mechanical properties of concrete. In this regard compressive strength of concrete specimens containing crumb rubber, rubber powder, along with nanosilica have been discussed at the ages of 7 and 28 days in the current research. A fixed water – cement ratio has been considered in the mixes. Crumb rubber particles ranging in size from 4.75 to 9.50 mm, and rubber powder of size 0.6 mm have been used. In this paper 5%, 10%, 15% (by weight of cement) of rubber have been used, and also 2% and 3% nanosilica were added to the mixes containing rubber. The results showed an improvement in the failure behavior, and compressive strength growth of concrete containing rubber and nanosilica.