JOURNAL OF CIVIL AND ENVIRONMENTAL ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2016 | Volume:45 | Issue:4 (81)|Papers Count:10

1. Introduction:Wind erosion is a major environmental problem in anywhere the soil is loose, dry, and finely granulated. That is because winds can easily lift and move sands and soil particles. Wind erosion occurs when the force of wind exceeds the threshold level of soil, because the force of wind is stronger than the gravitational force holding the soil down. Wind erosion is the result of complex interactions among wind velocity, precipitation, surface roughness, soil texture. Definitely, rate of wind erosion is related to the threshold wind velocity. Threshold wind velocity is the velocity which cause the initiation of soil particle movement of soil particle. It depends on soil particles size, moisture, and features. In terms of soil surface, Blanco and Lal [1], and Chepil and Milne [2] found that soil particle size has a negative relationship with wind erosion. Fine and loose particles are entrained more easily than coarse particles under the same wind velocity and it is because of weight of particles. On the other hand, soil moisture is also an important factor influencing the erosion rate. There is a variety of ways to control wind erosion. Recently, chemical and polymeric stabilizers be used for reducing wind erosion. Various researchers got to control wind erosion by using polymers such as: Poly Vinyl Acetate (PVIN), Poly Acryl Amide (PAM) as a stabilizer in laboratory scale with wind tunnel [3]. …

1. Introduction:In the design process of geo-environmental engineering projects, the use of soil mechanics experiments and specially permeability results has a noticeable impact [1]. In other words, one of the main parameters in the design process of waste disposal sites and earth dam design is the soil permeability. However, in geotechnical and geo-environmental projects there is a lack of attention to the influence of clay mineral type and variation of properties of soil pore fluid on the error associated with soil mechanics experiments. For these reasons, in this research the influence of clay mineral type and properties of soil pore fluid on the errors of consolidation and permeability coefficients are investigated. …

One of the most important phenomena in the nature with many undesirable effects for the environment is density current. Density or gravity current is a flow with a density of ρt, which is higher than the ambient fluid with density of ρa. This density difference causes a reduction in gravity g in the form of a g′ = g (Δρ / ρa). A schematic figure of a density current is shown in Fig. 1. …

1. Introduction:This study introduces a new kind of steel slit damper which can be installed diagonally in steel frames as a brace-type vibration damper. This new damper consists of three standard cylindrical tubes which have been placed inside of each other. On the middle tube wall, several long slotted holes are created in a manner that under seismic excitation, axial forces are created in the braces and then by its transmission to the tubes, narrow strips between these long slotted holes are yielded and therefore energy is dissipated through shear/flexural yielding. The inner and the external tubes will prevent the out of plane deformation of the middle tube. For fixing these tubes to each other and limiting the forward and backward movement of the middle tube, two long slotted holes have been created on the tubes walls. In comparison to the other available brace-type dampers, such as buckling restrained brace, this damper is simpler and costs less. The yielding part of this modified damper can be easily inspected after an earthquake. …

1. Introduction:An adequate and economical design for a pavement structure is just as important as a design for any other engineering structure [1]. It is possible to improve the characteristics of the asphalt mixture, using its components, aggregates and bitumen. …

1. IntroductionSpace structures are mostly interested for their lightness. One of the recent branches of space structures are called tensegrity structures. These structures are composed of compression bars and prestressed cables. There are not sufficient works about dynamic characteristics and behavior of these structures. Sultan et al carried out some research on nonlinear dynamic behavior of these structures [1]. Ben Kahla and Moussa studied the dynamic effects of rupture of a cable in an expanded tetrahedron [2]. Ben Kahla also has carried out a numerical analysis study of seismic behavior of a tensegrity frame [3]. Following these studies, in this research a set of tensegrity barrel vaults are considered and their seismic behavior is studied.

1. Introduction:The experiences of past earthquakes show that if a gas system is affected by severe and sudden damages of earthquake, gas leakage may cause extensive fire, massive explosions and consequently significant human fatalities and casualties. The importance of this issue is so that Byerly has indicated that fires following major earthquakes are so common that it should be considered as the complementary part of earthquake [1]. Due to the long lifetime of gas pipelines in district No. 20 of Tehran, and, in some cases, the passing of gas pipes across the existing faults or in close proximity, this municipal district has a high damage potential in times of probable disasters, such as earthquakes and subsequent fires. Therefore, in this research a numerical analysis method for the estimation of ignition probability of gas pipelines following an earthquake in district No. 20 of Tehran is presented.

1. Introduction:Free forms are usually used to refer double curve surfaces which are independent from groups of geometrically or mechanically constrained forms. Geometrically constrained forms are only conditioned by a geometrical definition, like it could be done on basis of simple surfaces. When there is a close relationship between forms and forces, the forms are mechanically constrained [1]. In the present study, behavior of double domes free form single layer space structures as a group of free form structures are investigated. Gaussian curvature of double domes can be positive and negative, unlike regular domes. In single layer reticulated space structures, local instability with nodal snap-through phenomenon could result in propagation in whole structure [2], so stability behavior of double domes free form single layer space structures should be investigated. The parametric study is performed in order to evaluate the effects of different variables on the stability behavior of double domes free form space structures.

1. Introduction:One of the most important problems in civil engineering is constructing structures, protecting excavation and the building in their surrounding and stabilizing embankments. Non-observing proper methods for protecting deeps and also constructing slopes will lead to irreparable damage and the risks resulted from probable subsidence and reducing the bearing capacity and lateral displacements will cause cracks in neighbouring structures [1]. …

1. Introduction:Steel tanks designed in cylindrical forms are one of the shell structures which are widely used in industrial facilities. In geometric terms, these tanks have a very small thickness compared to the other dimensions and thus are categorized as thin walled structures which should consider the buckling failures. The buckling failure of tanks containing liquids is possible in various modes. In this paper instability of cylindrical shell wall which occurs under simultaneous loading of axial compression and high internal pressure, is considered.