AMIRKABIR
Year:2004 | Volume:15 | Issue:59-C|Papers Count:13

This paper presents the results of testing and analysis of reinforced concrete floor slab panels using Long form steel decking. The purpose of the study is to assess the contribution of steel decking to the stiffness of the slab system and its influence on the short-term and long-term deflections. The tests were carried out under sustained loads for a period of 260 days. The study indicated that the decking steel can be included in the geometric properties of the slab section for the purpose of satisfying serviceability requirements on deflections. A set of conclusions and recommendations drawn from this investigation are presented.

concrete and reinforced concrete are used as durable materials in the construction of many structures but the durability and long term performance of this material has shown that its physical structure and structural behavior is a function of environmental conditions. Unless all environmental and geographical parameters are met in concrete design and construction, its service life and durability are reduced considerably and its need for repair increases. The concrete structures on the southern coasts and ports of the Persian Gulf region are continually exposed to extremely aggressive environmental conditions, namely a highly humid, hot atmosphere charged with corrosive ions (such as chloride and sulfate ions). The premature deterioration of concrete structures in the severe environmental conditions of the Persian Gulf region increases the importance and need for a comprehensive maintenance and repair system regarding these structures. Correct selection of the appropriate repair materials and techniques is necessary to ensure a durable repair. Performance of repair materials should be evaluated at the specific environmental conditions in order to select the most durable materials for the condition at hand This paper investigates the physical and durability characteristics of three repair mortars, assessed under normal laboratory and simulated hot weather conditions. A cement-based mortar was used as control, a polymer modified mortar, and a mortar containing silicafume were tested in the two conditions stated. Mechanical properties such as compressive and flexural strengths of mortars were compared. Capillary water absorption of mortars was measured and durability of specimens was evaluated in chloride solution.The test results obtained in this study show that some mortars are not durable in conditions where they are exposed to salt solutions and high temperatures and humidities. Mortars containing polymer or silica fume exhibit better performance when compared with other mortars. The use and application of appropriate polymers can enhance the durability of repair mortars.

The goal of this research is to measure the interface properties between a geogrid and a soil (i.e. the friction angle and dilatancy angle) as well as the strength parameters of materials used in the tests in order to be able to use the parameters in numerical analysis. A comprehensive set of large shear box tests were conducted on the geogrid. Apart from the main findings, some interesting results concerning the mechanisms behind the behaviour of reinforcement in direct shear tests were obtained.

Prismatic steel beam-column of double symmetrical cross section with semi rigid end connections was analyzed using second order analysis theory. For this purpose, the stability functions are utilized to form the stiffness matrix in which the effect of axial force on the flexural stiffness as well as the effect of flexural deformations on axial stiffness are involved. Since, in forming the stiffness matrix, the interaction between the axial and flexural forces on the corresponding stiff nesses are taken into account, performance of slender members can be properly evaluated. The effect of semi rigid connections is included in the stiffness matrix by a power model. Finally, three examples are included in order to: (1) verify the validity of formulations, (2) compare the results obtained from the proposed second order analysis with those resulted from AISCILRFD method, and (3) investigate the effect of semi rigid connections on frame behaviour. The results are in an acceptable accordance with those obtained by others.

the fukuoka method municipal solid waste landfil in kahrizak of perhaps the first engineered landfill project which was constructed in 1998 by Municipal Solid Waste Management Organization of Tehran, with cooperation of Habitat in Japan. Fukuoka is a semi-aerobic method for expediting the organic degradation of municipal solid waste, reduction of volume and improvement of leach ate quality which is used in over 80% of Japanese cities. Some unexpected problems during construction such as leachate circulation breakdown, leakage of leachate through surrounding embankments, several local slope failure on exterior side of landfill, and hence fears of a general shear failure caused some concerns during operation. A finite element nonlinear model by PLAXIS 7.2 was used to study the performance of the landfill during operation and after closure. The strength and deformation parameters of clean soil, partially polluted soil and polluted soil as well as the solid waste were obtained in an earlier study at Amirkabir University of Technology both by field and lab tests. The parametric studies by the numerical model indicated that the inadequate construction such as lack of necessary compaction of the surrounding embankments, using nonpermeable soil layers as the daily and intermediate covers, and breakdown of the air circulation and leach ate injection chimneys caused both the leakage of leach ate and reduction in factor of safety of the whole landfill.

In this paper an explicit mathematical model is developed to solve shallow water equations and it is applied to flows with complex geometry. Control volume method is used to solve unsteady equations with a staggered grid arrangement. Turbulent stresses are calculated based on a constant eddy viscosity. The model is verified in different flow conditions such as a flow in a canal with a wavy bed, propagation of wave in a reservoir, sudden expansion in a rectangular channel, uniform flow in a rectangular channel, which is inclined with respect to the coordinates, and flow in a meandering channel The results are compared with experimental and analytical data. Complex boundaries are introduced to the model by steps. The effect of steps on the accuracy of model is investigated. It is shown that steps introduce additional resistance to the flow. This additional resistance is however negligible if flow velocity is low and the width to depth ratio is large.

in this paper a finite volume scheme is used to discretize flow in prous media. A numerical method for treating advection-dominated contaminant transport for flow of groundwater is described. This method combines the advantages of numerical discretization and finite volume method. The equations are discretized using a finite volume approach. The resulting nonlinear differential system is integrated in time using a solver. The conservation of energy equation is solved using a special method for reducing the oscillations induced by the standard finite volume method. Consequently, a mathematical model for multi-component flow transport in an anisotropic media is presented which couples the equations for multi-component diffusion and Darcys law for flow in aporous medium. Furthermore application of an integrated matlab system in several studies has been provided. The integrated matlab is based on open data formats and standards and may be used for many other application areas, especially where modeling in 2D and 3D is involved. Numerical simulations are performed to validate the model and investigate the effect. The final purpose of this paper is to discuss and compare the differences between the finite volume scheme for uniform and unstructured grids, which is shown to be less than 0.2 percent.

Earth slopes and high vertical cuts are frequently observed to be stable for long period in the coarse-grained soils of Tehran. Their stability is often attributed to cementation effects that produce improved shear strength parameters. These soils are heterogeneous not only in gradation and density but also in cementation. Due to this heterogeneity and the extreme difficulty in obtaining undisturbed samples, artificially cemented specimens using lime as the cementing agent are used to understand the effects of cementation on the shear strength parameters. A base soil with 45% gravel, 49% sand and 6% fine material was used, based on gradation curves of the coarse-grained soils of Tehran. Specimens with 100mm diameter and 200mm height are prepared by mixing of the soil with 1.5, 3, and 4.5 percent by weight lime and after curing weretested using drained triaxial compression tests. Samples were also tested in uncemented and destructured conditions. The results of the tests indicate that the cementation increases peak shear strength, suggesting an increase in cohesion. Cemented samples show a brittle failure mode at low confining pressure with a transition to a ductile failure mode at higher confining pressures. The stress-strain curves for cemented samples show a clear peak stress followed by a sudden drop in stress and strain softening. There is no clear peak in shear stress for uncemented and destructured samples. The failure envelope is curved for cemented samples. The influence of cementation on the friction angle of the tested samples is a function of confining pressure, and degree of cementation. The results show that the peak friction angle at low confining pressure increases with increase in cementation. The residualfriction angle is almost equal for cemented, destructured and uncemented samples.

In this paper, optimal signal setting problem is studied as a bilevel optimization problem. Optimization techniques suggested for solving this problem usually result in local solutions and are inefficient in solving large-scale problems. In this paper, two heuristics are proposed for solving this problem. In the first one, an alternative model is used which represents an equilibrium flow problem with multi-variable cost functions. In the second one, essentially a two phase algorithm, in the first phase signal timings are calculated by solving the system optimum problem. Later, in the second phase, user equilibrium flows are determined by solving traffic assignment problem. Performance of these two heuristics are investigated solving a small-scale and a medium-scale examples.

Teleworking, as a transportation demand management strategy, can have significant transportation impacts. This strategy can cause a reduction in number of trips at the traffic peak period, and thus, is equivalent to large investments for constructing and increasing the transportation network capacity. In this study, feasibility of teleworking for different jobs is modeled based on job tasks. This study aims to demonstrate the application of these ideas in order to estimate the number of feasible teleworking days for different jobs. This is done using discrete choice models such as multinomial and nested logit. Based on the results of this modeling, job tasks regarding suitability and feasibility for teleworking can be identified. A small sample is used to demonstrate how the method works

in this paper, application of adaptive network based fuzzy inference system (ANFIS) in estimation of compressive strength of high strength concrete (HSC) was investigated. ANFIS is a hybrid structure that is based on fuzzy If-Then Rules that are represented in a network. To predict the compressive strength of HSC with ANFIS. totally 429 records collected from four different resources. Records were randomly divided into two sets. One set is called training set that is used to train the ANFIS models and another set called testing pairs was used for evaluation of , the models. Totally 56 different ANFIS models with various membership functions were used to predict the compressive strength of HSC. These models were evaluated with root means square. and correlation factors. Finally with comparison of the capabilities of the models. some models were proposed as optimum models. It was found that model with triangular membership function (trimf) and "St334333" structure (4 membership function for super plasticizer and three membership function for other concrete mix components) is the best model to predict the HSC's compressive strength regarding its components.

Imprecise construction work might cause imperfection in the shell of RC. hyperbolic cooling towers. By considering the three directions concrete fracture model and by using elements in Finite Element analysis which could crack in three directions, it could be shown that in imperfect shell, the thickness cracks occur at the end of the weight and thermal loads. In the other words, the inside and outside of the concrete shell separate. The number of such cracks rises up by increasing the imperfection in the cooling tower shell. This increase in number of cracks could multiple when two concavity and convexity imperfections happen consecutively. Since there is not any reinforce bar for preventing of such cracks, so it must be avoided by precise construction work and by modifying the participating thermal load factor in combining loads.

For the analysing purpose of the High Strength Concrete (HSC) box columns first, by two methods (i); by solving the governing differential equations of a thin-wall concrete section which act similar to an orthotropical plate and (ii), by the strain energy method the critical load of orthotropical plate was calculated. Then, by investigation, it was concluded that the local buckling is not an important aspect for the ratios of h/a> 0.06 ( the ratio of thickness to , the larger dimensions, of the section) and therefore the sections failure will be occurred while the load is reached io its ultimate capacity i.e.,prior to the local buckling.a simple and easy method was adapted to analyse and design the HSC box columns then, by use of this method and a computer program written (MATLAB Package)the interaction diagrams of such sections were plotted. Now, with availability of the setype of diagrams, the non-dimensional diagrams were plotted too. Based on the nondimentional diagrams it was concluded that, by availability of only one type of these diagrams, for example, the interaction diagrams for solid sections having HSC and applying the ratio of Ah/a (the ratio of area of box section to that of the solid section) to its interaction diagrams, the axial load and bending capacity of box sections can be determined quite easily.