نشریه مهندسی عمران
سال پنجاه و دوم شماره 4 (تیر 1399)

Research indicates that the use of Emitters in more suitable for use with wastewater than other irrigation methods. In order to study the Emitters discharge variation by using refined wastewater in drip irrigation systems, two drip irrigation systems (a water well system as control treatment and the other with a Miandoab refinery refined wastewater as main treatment) was installed and implemented. Due to the difference and sensitivity of various emitters against physical clogs effected by water soluble, four emitters consists of 4-litr Euro-droplet emitter with 1 meter outlet distances, two 4-litr Iran drip emitter with 1 meter outlet distances and the 16mm type tube was used at 20 to 30 cm output distances. The systems were tasted in a 4-meter pressure mode and it was determined that the Euro-drip emitter has the best performance and with technical and appropriate management, the system has the ability to run with the refined wastewater. The results showed that the Euro-drip emitter indicates the lowest percentage of discharge decrease. The highest emitter absolute dispersion uniformity percentage during operation with a 4- meter pressure is related to the Euro-drip with 95.6% and the lowest value for the Iran-drip with 88.15%. Also, Iran-drip emitter the most discharge decrease by 29.4%.

A laboratory study was performed to determine the benefits of micro and macro fibers in roller-compacted concrete (RCC) for concrete pavements by measuring the RCCs mechanical and durability properties. To this aim three polymer fiber reinforced RCC mixtures with use of micro and macro polyolefin-based and polypropylene-based fibers in two volumetric content (1 and 2 kg/m3) were prepared and their mechanical properties including the compressive strength and flexural strengths (measured as modulus of rupture and toughness as energy dissipation and durability properties including salt scaling under freeze and thaw cycles and water permeability were evaluated. The results showed that, the macro fibers (as polyolefin-based fibers) could be efficiently enhanced the toughness in comparison with the micro fibers (polypropylene-based fibers). Moreover, the water permeability under pressure of both micro (polypropylene-based fibers) and macro fibers as (polyolefin-based fibers) reinforced concrete decreased up to 20% in comparison with the reference concrete. Furthermore, it was found that the application of micro fibers in comparison with macro fibers significantly improved the salt-scaling resistance of roller compacter concrete.

The research purpose is to evaluate and compare the seismic behavior of composite and steel shear-walls in construction frames with semi-enclosed composite columns. The numerical behavior of composite and steel shear-walls with semi-enclosed columns was investigated and then the parameters affecting the seismic behavior of the composite shear-walls under cyclic loading were analyzed with the Abaqus software. Software validation was performed with two laboratory samples. The results showed that the use of Semi-enclosed columns increased 48% and 56% in the ultimate strength of the composite shear-walls with unilateral and bilateral concrete. These columns improved the ductility and energy depletion. The semi-enclosed columns caused a 15% increase in the ultimate strength of the steel shear-walls and had a limited impact on the energy absorption. The increase in steel plate thickness of the composite shear-walls from 2 to 4 and 4 to 6 mm, resulted in 16% and 14% improvement in the ultimate strength and energy depletion, respectively. The gap of 11.3 mm between the steel frame and the concrete wall was optimum. By reducing the diameter of the gap to 6.5, the strength decreased by 1.5% and with increasing the diameter of the gap to 9.16 mm, strength dropped by 7%. By increasing the thickness of the cross section of the composite columns from 2 to 5 and from 5 to 8 mm, the strength increased 25.3% and 12.1%, respectively. With an increase in strength of concrete from 30 to 72.5 MPa (142% increase), the structural strength increased by only 15%.

Nano-structured materials are waterproof, they can be used for scouring reduction in alluvial beds. In this research impact of clay additive and nanomaterials and silicafume to sediment bed materials of stepped spillway on control of erosion and scouring in investigated as a nonstructural solution. First effects of steps count and flow regime on downstream scouring were studied. The results show that increasing the steps count on the same slop of chute and in a skimming flow regime on the steps the depth and length of the scouring on step spillway downstream increases. Then impact of some injected additives to the sediment bed with the same step count and skimming flow regime was investigated. The results proof the positive effect of clay and its mixture with nanoclay and silicafume on improvement of scouring length and depth reduction on the weir downstream. The best performance between three different compositions is related to the mixture of clay with nanoclay and silicafume in which they contributed in reduction profile of scoring by 48.74% and 46.38% respectively compared with the reference model. At the same time injection of clay to the sediment bed reduced the depth and length of scouring by 35.63% and 20.88% and injection of clay with nanoclay reduced the depth and length of scouring by 41.41% and 37.75% respectively. These results can state the success of clay, nanoclay and silicafume on scouring control mechanism at downstream of hydraulic structures especially in flood discharges.

The coastal waves caused by landslide in the lake of reservoir dams can threaten the safety of the dam. Therefore, the exact recognition of hydraulic flow due to coastal waves has always been of interest to researchers. So far, extensive laboratory and numerical research has been devoted to it. In this research, a completely lagrangian numerical method which is based on particle and non grid called the Smoothed Particle Hydrodynamic Method (SPH) is used to simulate coastal waves due to landslide. In the present study, a new three-step SPH algorithm based on the prediction and correction method is solved by governing equations. In order to validate the method, the laboratory datas of the dam break problem on dry bed has been used. The results of this study approximated the analytical solution well. Also, the correlation coefficient of 0.9998, the mean absolute error of 0.5426 and the efficiency coefficient of the Nash-Sutcliff model 0.974 for the calculated parameters indicate that the model is accurately. In addition, the results showed that the ability of the present model in the numerical simulation of sub-surface landslide wave in the production region and run-up region is high, and it simulates the propagation region very well with a accuracy of 95%. With the comparison of measured and laboratory results, the correlation coefficient and the root mean square error were 0.95 and 0.0071 respectively, which indicates the high accuracy of the model in calculating the surface water profile due to subsurface landslide.

In this study, two general circulation models (GCMs) (Can-ESM2, BNU-ESM) were used to simulate the future precipitation of Tabriz city. The weakness of GCMs is the coarse resolution of climate variables in which the different methods of downscaling is about to solve this deficiency. In this study, the Artificial Intelligence (AI) models i.e., Artificial Neural Network (ANN) and Adaptive neuro fuzzy inference system (ANFIS) were used to statistically downscale the climate variables of GCMs. Without any doubt, the most important step during the use of these models, is selecting of the dominant inputs among huge of large-scale GCM data. So in this study for the selection of dominant inputs, decision tree and mutual information (MI) feature extraction methods were used. Also, the ensemble techniques were used to evaluate the efficiency of downscaling models and to decrease the uncertainties. Comparison the result of downscaling models indicated that the ensemble technique (i.e., hybrid of ANN and ANFIS) with dominant inputs based on decision tree feature extraction method presents better performance. In both GCMs, the application of the ensemble downscaling couple with dominant predictors based on decision tree model in precipitation downscaling showed 10%-38% increase in DC in versus the individual ANN and ANFIS downscaling models. The projection precipitation of Tabriz synoptic station for future (2020-2060) by proposed ensemble AI- based model indicated 30%-40% precipitation decreases under RCP4.5 and RCP8.5 scenarios.

The SPSWs have been enthusiastically applied in some of the tall buildings across the world as a novel lateral load-bearing system and due to their proper stiffness, strength, ductility, and energy absorption, as well as remarkable reduction in buildings’, weigh compared to the concrete cases, they are deemed as an efficient alternative for the traditional load-resisting systems. fire-related hazards and their impacts on the structural systems have been of major concern for practitioners which is of utmost significance for special structures and tall buildings. Accordingly, in case of thin steel plate shear walls, fire is most likely to leave detrimental effects on the lateral stability and strength of them due to their small values of thickness. To better understand the behavior of such systems in the event of a fire, this paper aims to investigate the impact of heat caused by a fire on the stability, elastic stiffness and yield strength of a 3-storey frame equipped with SPSW system. Based on the results derived by connected stress-heat analyses, thickening the wall results in substantial reduction in the column’s deformations. Moreover, increase in thickness and yield strength of the steel plate plays an effective role in less reduction in yield strength and elastic stiffness of the system after fire events although, while the plate thickness is kept constant, the system’s elastic stiffness does not vary as the yield strength raises. In addition, simple relations were achieved to estimate the post-fire elastic stiffness and yield strength of the SPSW system.

Regarding the importance of optimized and economic design of structures, reducing the total weight of structures has been considered. This approach leads to decrease the cost of building projects. In other point of view, reducing the weight of structures will be associated with decreasing the dimension of different elements so it can increase the likelihood of strength failure in the structures. This paper intends to apply the soft computing technique, firstly, to bring a new algorithm for minimizing the weight of structures with respect to satisfying different technical constraints and secondly, to improve the speed of answer. To achieve the second goals, various methods including the modified genetic algorithm, the modified ant colony and artificial neural network were applied and tested. Some performance indicators such as speed of answer, accuracy and etc. were selected to compare the output of those mentioned approaches with traditional calculations. The obtained results showed that the modified ant colony algorithm has better performance in terms of speed of answer and accuracy. While several previous investigations have been looked at the problem of structure weight optimization in a two-dimensional perspective, this paper developed three-dimensional modeling by applying the spectrum dynamic analysis. Four types of structures were examined to bring comprehensive results.

In this research, Seismic behavior of concrete rectangular fluid tanks has been studied and the importance of the effect of the earthquake’s vertical component investigated. The structure of tank and medium of the water has been modeled using finite element and smoothed particle hydrodynamics methods respectively. The smooth particle hydrodynamics which is a meshfree method, has many advantages over other traditional grid-based methods. For verification purposes, the modeling accuracy compared with the available experimental and numerical results. The analysis ran under horizontal records with predominant periods in different ranges, once considering vertical component and another time without it. Afterwards, The parameters of sloshing height base shear, force in unit width and displacement of the wall has been obtained for comparison. The results show that consideration of vertical component in analysis has a negligible effect on sloshing response but it is significant on structure’s response. Meanwhile, the maximum sloshing occurs in analysis under horizontal record with high predominant period. Tanks with different thicknesses or in other words, different flexibilities of walls, show completely different sloshing and structure response. Also considering walls which are parallel to direction of earthquake as flexible, has significant effect on response of the structure. As a result, the effect of vertical component and flexibility of walls must be considered in seismic analysis of tanks.

Recently, the use of hollow-bar micropiles has increased rapidly. These micropiles reduce the time and cost and not only were used as a reinforcement element, but also used to improve the surrounding soils. Despite the increasing use, few studies have been conducted on the performance of this type of micropiles, in particular the determination of load capacity, failures criteria, and interpretation of loading tests. In this study, 22 hollow bar micropiles with simultaneous injection method in different lengths and soils were executed and full-scale tension and compression loading tests were performed on them. Then, by using the six common failure criteria for pile foundation, the performance and ultimate load of these tests were evaluated. Using mathematical relations and assumptions about load-displacement curves, also using numerical modeling of the observed load-displacement behavior, field test results have been developed to reach to the geotechnical failure. The results show that since the diameter and bond strength of hollow bar micropiles is more than theoretical ones, the existing failure criteria are not suitable for interpretation of their load-deformation behavior. The existing failure criteria do not take into account the increase in the bond strength and the reduction of the elastic length. Based on the information obtained from the existing failure criteria and considering the effect of elastic shortening on the loading test results, a failure criterion has been proposed to determine the failure load of hollow bar micropile based on the Davison method.

Considering the geotechnical problems caused by low strength clayey soils is important in construction projects. Chemical stabilization with additives such as cement is a common method to improve the engineering properties of clay soils. In spite of the acceptable effects of cement on strength of soils, the cost of this additive and its destructive effects on the environment should be of concern. This has led the researchers to use by-products and waste materials. Cement Kiln Dust (CKD) is a powdery by-product of the Portland cement manufacturing process. In this paper, the geotechnical parameters of cement and cement kiln dust stabilized kaolinite clay are compared. For this purpose, Atterberg limits, standard proctor, unconfined compressive strength, and California bearing ratio tests were conducted on specimens containing 5, 10 and 15% cement and CKD (by dry weight of the soil). The results show that the cement and cement kiln dust increase the soil strength. It was seen that the unconfined compressive strength of the specimen with 15% CKD is equal to the specimen with 10% cement after 28 days of curing. It is evident from the scanning electron microscopy analysis of specimens containing cement and CKD that calcium silicate and aluminate hydration products reduce the volume of the void spaces and join the soil particles, leading the strength to increase.

Due to the complexity of a three-dimensional (3-D) arrangement of multiple columns, a 3-D problem has been commonly converted into a two-dimensional (2-D) model which has equivalent properties and dimensions by the equivalent trench method and the equivalent area method. These methods are used extensively in analytical and numerical studies. However, no comparison of the results of the above methods and the laboratory studies has been done. Therefore, in this research the experiments performed on reinforced soil in a large direct shear device with dimensions of 305*305*152 mm. Experiments performed with individual stone columns (single, square and triangular arrangement), equivalent trench and equivalent area method.The effective parameters include the area replacement ratio, 8.4 ,12, 16.4 and 25 percent, and vertical loads ( 55, 75 and 100 kPa) Has been studied. Results showed that improvement the stiffness of composite soils and increase in shear strength of individual stone columns (single, square and triangular arrangement) and equivalent trench and stone column arrangement had an impact on improving the shear strength of stone columns. The most increase in shear strength and stiffness values was observed for square arrangement of stone columns and the least increase was for single stone columns. Comparing the results of individual stone columns and equivalent trench in any arrangement, showed that equivalent trench arrangement can be used in two-dimensional models instead of three-dimensional individual stone columns. In the equivalent area method, there is no increase in shear strength and shear strength parameters compared to sandy bed.

One of the main challenges of arid and desert regions is to control wind erosion that can cause significant economic and environmental damage. The present study aimed to stabilize erosion-prone soil using a vegetable mulch prepared from Eremurus spectabilis root powder. The effects of concentration and amount of mulch spraying on the soil erosion was investigated and the penetration and reduction of the thickness of the fixed layer against wind speeds of 6, 9, 12 and 15 m/s for 5 minutes was studied in the wind tunnel. Finally, EC, pH, salinity and other soil elements were tested to evaluate the environmental impact of mulching. The results showed that increasing the amount of mulch spraying results in more mulch penetration in the soil and increasing the mulch concentration, despite reducing the depth of its penetration into the soil due to increasing the amount of adhesion between the soil particles, its greater resistance to wind erosion. In addition, based on the results, mulches with concentrations of 0.2, 0.6 and 0.7% can stabilize the soil against the wind stream, up to maximum of 9, 12 and 15 m/s, respectively. Generally, the mulch is environmentally friendly and is an appropriate option for controlling the erosion of wind erosion-prone soil.

Accuracy of the Multiquadric method depends strongly on the choice of the shape parameter. This research proposes a new algorithm for determining the optimal shape parameter. It resolves some of the difficulties such as dependence on the number of computational nodes, existence of an analytical solution of the problem, high cost and low accuracy of calculations, convergence of classical optimization methods to local optimal points and so on. In this regard, the Genetic Algorithm (GA) has been used and, lower and upper bounds of the shape parameter are suggested as minimum (when the coefficient matrix is not singular) and maximum of Euclidean radius, for speeding up the solution process.The algorithm consists of four steps: 1) producing initial shape parameters by GA in the proposed range, 2) introducing the MQ function with a few numbers of computational points, 3) introducing the MQ function with a large number of computational points and 4) minimizing the difference of solutions of two functions obtained from the two preceding steps. In the meta-heuristic algorithm, distribution of points is uniform such that each three points are the vertices of equilateral triangles in the problem domain.For verification, examples of homogeneous, inhomogeneous and anisotropic types of the seepage phenomena were solved so that domain decomposition technique was used for inhomogeneous problems. The study shows the high capability and accuracy of the proposed algorithm. In this approach, the optimal shape parameter can be achieved independent of the number of computational points for arbitrary geometries.