نشریه مهندسی عمران
سال چهل و هشتم شماره 2 (تابستان 1395)

The construction industry is one of the most important industries in Iran that, unfortunately, In spite of its potentials to increase new business information and GDP, couldnt be worked out its domestic and international missions, so that it has only a little international market share. This share is not in proportion to its capabilities and potentials in existence, and the special geographic region. Therefore, it is necessary to identify all dimensions and sectors of the construction industry and analyze its performance in Iran. In this article, first, we identify the construction cluster in Iran by use of cluster approachand Delphi method, and then evaluate its competitiveness. At the end, expert's opinion and other countrie's experiences have been used to give recommendations for improving the level of construction industry in Iran.

The most important factor in soil preloading is the consolidation time. In any cases, if installation depth of the vertical drain is less than the design depth (which is equal to the thickness of the compressible layer), a delay of the consolidation process will occur. In this paper, effect of this parameter on consolidation time is determined by numerical modeling and then a case study (soil preloading project of Sarbandar decanter units in Khoozestan) is studied. In some areas in this project, the penetrating depth of vertical drains is less than the expected design depth. Comparison has been made between numerical modeling and data from field instrumentation could be done. It is concluded that if the penetrating depth of vertical drains is more than 80% of the compressible layer thickness, the delay in the consolidation process seems to be negligible.

Unreinforced masonry system was a conventional form of construction in rural areas in worldwide countries in last decades. The main advantage of using this system is that it is cheaper than other building systems such as reinforced concrete or steel. Iranian seismic code proposes masonry walls confined by reinforce concrete or wooden ties. This building type called confined masonry is very common in Iranian construction but code provisions regarding this have not improved during recent years and are very similar to the old provisions proposed for unconfined masonry buildings. In this study, the specifications of confined masonry buildings are described. Then some equations proposed by different codes to estimate the lateral resistance of masonry walls are reviewed. An equation is proposed to estimate the lateral strength of confined masonry walls designed and built according to the Iranian codes. The proposed equation then is validated with the results of the tests the authors conducted on seven confined masonry walls.

The effect of vertical earthquake component is studied here on the behavior of sliding foundations. Regarding complication of the problem and in order to focus well on the main subject, the superstructure is considered as a rigid block, which can be a representative of low masonry buildings. Recent researches show that coefficient of friction is not constant, but depends on instantaneous frequency and amplitude of the vertical vibration which normally change during the earthquakes. These instantaneous parameters can be calculated by WAVELET transforms. Both horizontal and vertical components of earthquake as well as the variation of frictional coefficient are considered in the analyses of this study. The results for five different earthquake records show that the applied acceleration of the block rises by considering the vertical earthquake, however variable frictional coefficient, compared with the constant one, decreases the acceleration. Both vertical earthquake and variation in frictional coefficient raise the sliding of the block in most cases.

One of the most important factors in the extraction of minerals obtains the maximum benefit. The extraction of minerals is benefit when the more minerals extracted with considering of the technical conditions. In this study, using Flac3D and strain plasticity model, the shape of pillars in Faryab Chromite mine is optimized. In this regard, the pillar of the cylindrical shape was modeled and then the diameter of the cylinder in the middle of the pillar was decreased. The most suitable shape of pillars was obtained with a diameter of the middle 8.6 m and the diameter of the upper and lower 8.8 m.

The coarser particles deposit gradually and form a delta at the upstream of the reservoir that extends further downstream towards the dam. In this research the effect of non-uniform sediment particles has been studied experimentally on the Delta progression in the reservoir. 10 types of grading curves were used. All of the curves were the same in mean diameter and they have normal distribution. In this research, the effect of non-uniform particles on delta progression was investigated using a physical model. In this model the river is connected to the reservoir by a gradual transition. Based on the experimental observations, in the range of this study velocity of Delta progression decreased with increasing of non-uniform particle and time of progression increased. In the range of geometric standard deviation 1 to 2 the effect of non-uniform particle was not tangible but with increasing of geometric standard deviation the effect of non-uniform particle on Delta progression observed. Based on the experimental observations, slope of foreset decreased with increasing of non-uniform particle.

Since the beginning of modeling physical events by computers, the finite element method has been firmly accepted as one of the most efficient general techniques the numerical solution of a variety of problems encountered in engineering. But no one has provided an answer to accurately determine the discretization error value in analyzing a structural problem using finite element method and there is almost no accessible tool to select suitable sizes for elements and proper types of solutions and the size of each element is selected based on experts’ judgments.
The present paper is an attempt to present a closed-form solution for three-node triangular elements in order to estimate the discretization error in continuous domains by using the rule of gradient recovery and h-refinement adaptivity. Computing the discretization error and diagnosing the suitability of the elements size are possible by the closed-form solution presented.

One of the most common connecting systems that is used for the manufacture of space structure, is MERO connecting system. So a perfect knowledge of the behavior of this connection is the most essential problem for the engineers and designers. The results has shown that different parameters including the degree of tightness of the bolts affect on the static and dynamic characteristics on these kinds of jointings. Distinctly in this research the effect of the bolts tightness degree and the magnitude of the vibration on the dynamic characteristics of the MERO connecting system has been experimentally evaluated. Therefore a member made by this system in the form of a cantilever beam at different degree of bolt tightness and by the free vibration method and by making initial displacement was experimented in order to determine the quantity of dynamic system parameters including the damping ratio, damping coefficient and the natural frequency. The results obtained showed that, the magnitude of bolt tightness is directly proportional to the structure vibration. Also the maximum damping ratio and damping coefficient occurs at 60 Nm bolt tightness, and if the tightness degree is more or less than this quantity, the magnitude of damping ratio and damping coefficient would be less than that. Also the results showed that there is a direct relation between the initial displacement with the damping, it means that by increasing the vibration amplitude the damping will increase and vice versa.

Stress analysis and stability control in tunnel intersections is a very complicated issue due to stress concentration and three-dimensional situation. During tunnel construction, increase in load on support, extra tunnel deformations and disordering in rock around of intersection zone is unique and instability may be occur in this sections. In order to control extra deformation and stress, these sections need stronger support system than other sections. Extra deformations and stress values in Y shaped intersections influenced by tunnel intersection angle. The effect of intersection angle on length of extra support has been studied in this paper by three-dimensional modeling of penstock tunnel intersection of Rudbar Dam in FLAC3D. Numerical analysis results for three intersection angles of 60, 75 and 90 show an increase in length of extra support by decreasing in intersection angle.

Underground structures like tunnels are important elements of transportation, network, and service, which due to being surrounded by the ground and withstanding in situ stresses show different seismic behavior in comparison of surface structures. This paper presents analytical solutions for seismic and static loads in circular tunnels, and then they have been used to evaluate internal forces of lining for a section of Bangkok’s urban tunnel. The problem is solved using numerical analysis of finite difference for both horizontal and vertical acceleration coefficients and the results compared with analytical solutions results. According to the results by increasing the horizontal seismic acceleration, the axial force and bending moment increases. And with increasing the depth of tunnel, the forces of lining increases but vertical acceleration of earth has small effect on stresses. For the in- situ stress coefficient it has been seen that as the ratio is further more away from the number one, the created stress increases in the lining.

Taking into account that the stability analysis of the earth slopes is a complicated geotechnical problem and conventional methods of analyses because of circular slip surface assumption, are incapable to estimate the location of the slip surface especially in non-homogeneous earth slopes.Therefore, the new methods for the study of these types of slopes are necessary. Nowadays, the methods based on optimization principles are developed and the main point in the application of these new methods is the evaluation of the capability of these methods. Therefore, optimizing these problems needs robust algorithms. In this research, three meta- heurestic algorithms were applied for the slope stability analyzing of three studied and selected cases from literature. For all three cases of study, a non-circular slip surface is considered. Factor of safety was computed and compared with the same cases analysed analytically. The obtained results indicated that ICA had the best performance and FA had the worst results for the cases studied in this research.