مجله پژوهش های زیرساخت های عمرانی
سال نهم شماره 1 (پیاپی 16، بهار و تابستان 1402)

The downstream scour of the vertical drop can be one of the causes of instability and failure of this structure. In the present study, the downstream scour depth of this structure predicted using the support vector machine (SVM) method. For this purpose, 104 experimental data used to estimate the scour depth. hese data are a function of the two dimensionless parameters of dansimetric Froude number (Frj) and tailwater depth (yt / yj) that have been entered into the SVM in three different models. To evaluate the results, the evaluation criteria of R2, NRMSE, DC, and MARE used. The results showed that model number (1) with the input combination (Frj and yt / yj) with R2 = 0.9777, DC = 0.929, NRMSE = 0.0775, and MARE = 11.89% for the test stage leads to the best result. The SVM method also has appropriate accuracy, acceptable results, and desirable performance in estimating the scour depth. Also, it was found that the densimetric froude number has a greater effect on estimating the relative scour depth compared to the tailwater depth.

The focus on sustainable development is increasing and it is given great importance. Sustainability be able to meet the needs of future generations and mitigate serious risks such as global warming. Cement is one of the building materials which no construction on the ground is possible to build. Cement production increases energy consumption and increases the production of greenhouse gases, especially carbon dioxide. In this experimental study, mechanical behaviour (compressive strength) and sustainable development indicators of cement mortar containing natural pozzolans consist of high silicate aluminate with different percentages (6, 13 and 20%) partially substitute with cement in mortars with 8 mix designs and variables were sand and water to cement ratio with strength of up to 13 MPa have been investigated. Findings showed that the use of 13% of natural pozzolans containing high silicate and aluminate as a cement substitute after 56-days of curing increased the compressive strength of mortar by 2.23% compared to the reference samples. In addition, the analysis and evaluation of sustainable development indicators of this mortar concludes that the optimal percentage of replacement with cement in the mortar, leads to a reduction in global warming potential and energy consumption by 13% in the production of one ton of cement in the conventional way. That plays a positive role to help climate change, reducing air pollution and reduce emission of greenhouse gases.

In this study, the improvement of a clay soil contaminated with MTBE (methyl tert-butyl ether) using magnesium oxide and hydrated lime was studied. Soil contaminated with MTBE was prepared in the laboratory, then mixed with different percentages of magnesium oxide and hydrated lime. Natural soil was also mixed with the same percentages used with the desired additives. Atterberg limits, compaction, Unconfined compressive strength, and SEM tests were performed on all samples. To determine the strength, the samples were prepared by static method and tested after 7, 14, and 28 days of curing time. The results showed that magnesium oxide and lime both increase the strength and E50 and thus improve natural and contaminated soil, which is a function of the percentage of used additives and curing time. The Comparison of improvement results showed that the final strength in natural soil is higher than in contaminated soil. In addition, the comparison of the results showed that lime has less effect on soil improvement compared to magnesium oxide. The SEM results also showed that the increase in strength is due to the cement materials produced during the carbonation process, which makes the particles paste to each other and make a rigid body.

Determining the pattern of lateral displacement distribution in the height of structures and the factors affecting it, has an important role in increasing the accuracy of optimal design and functional design against various seismic loads. In this paper, the pattern of lateral displacement distribution between floors at the height of flexural reinforced concrete frames is investigated and the effect of seismic intensity and pulse period on this issue is investigated. The studied frames are three structures of 3, 9 and 15 floors of RC Moment-resisting frames. the middle frames of the structures were non-linearly modeled in 2D in the SeismoStruct 2021 program, and nonlinear analysis was performed under the set of records and at different seismic intensities. the displacement response of the structures was compared. The results showed that in orderly short-term reinforced concrete bending frames without any irregularity under the set of selected accelerometers in this research, the effect of all records is almost equal and displacement occurs in the upper floors. As the height of the structures increases and the effect of higher modes increases, the effect of the pulse period of stagnation and seismic intensity is felt.

In this study, the critical state shear strength of a type of sand with different silt percentages in saturated and unsaturated states has been investigated. For this purpose, a number of undrained consolidated (CU) and drained consolidated (CD) triaxial tests were performed on saturated and unsaturated samples, respectively. The samples were sheared under confining pressures of 50, 100 and 150 kPa and suction levels of 50, 100, 150 and 250 kPa for unsaturated samples. In the saturated state, the results showed that if samples are remolded with the same eeq, for the different percentages of fines the critical state lines are converged. In the unsaturated state and net stress state, the critical state line is not only dependent on suction, but also changes with changes in the percentage of fines. However, in the effective stress state, by applying the appropriate effective stress relations and the concept of equivalent intergranular skeleton void ratio, these lines can be converged independently of suction and fine content and reach a single critical state line in the stresses space.

In this study, the effects of the cement stabilization on the interface of the soil and a geotextile, the thickness of the cement and geotextile layer, and the thickness of the geotextile layer on the interface shear strength have been investigated experimentally. In the experiments, a direct shear device with a cylindrical mold with a diameter of 6 cm was used. The geotextile was a woven type. The cement-treated reinforcements were papered by the application of a thin layer of cement with amounts of 0.016, 0.048, 0.08, and 0.112 gr/cm2 on the surface of saturated geotextiles. Geotextiles with different thicknesses were produced by joining several layers of geotextiles using a flexible glue. The interface shear tests have been performed under vertical stresses of 50, 100, and 150 kPa. The results show that adding 0.112 grams/cm2 of cement to the interface of the reinforcements can increase the shear strength of the interface of the samples by 50%, but the amount of cement added should not be less than a certain limit. By comparing the results of tests conducted with different thicknesses of reinforcement with different amounts of cement, it can be concluded that increasing both the cement content and the thickness of the reinforcement increases the shear strength of the interface. By increasing the thickness of the reinforcement, the soil grains are integrated into the reinforcing fabric, produce a rough surface, and increase the shear strength at the interface of the soil and the geotextile.

Natural rivers experience significant sediment transport rates during floods.The purpose of this study was to investigate the effects of flood hydrograph intensity parameter on the amount of bed sediment transport rate. For this purpose, a real unsteady flow hydrograph was created inside a 15 meters long tilting flume by installing an interface board between the computer and the pump inverter. Sediments with a d50 of 2.69 mm have been put uniformly on the bottom of the channel and the flood hydrograph has been applied on it after saturation. 20 cases of hydrographs with different intensity parameters were tested and the erosion rate was obtained during the hydrograph time. The results show that the maximum erosion rate always occurs near the peak of the flood hydrograph and the time delay between the peak of the flood hydrograph and the peak of the sediment hydrograph is mostly positive. The erosion rate in the rising limb of the hydrograph is higher than the falling limb, and the distance between them decreases in the hysteresis diagram as the flow intensity parameter decreases. The changes of bedload transport rate (qb) in terms of flow rate (Q) are clockwise hysteresis. By decreasing the hydrograph intensity parameter by 32, 57, 75 and 87%, the total volume of transferred sediments decreases by 27, 51, 78 and 90%, respectively. A 50% decrease in the base time of the hydrograph under the same conditions has caused a 46% decrease in the total volume of transported sediments.

Pollution of soils containing petroleum products is one of the most important environmental challenges. Therefore, it is necessary to take measures for the purification of petroleum products, including diesel, to clean these compounds from the soil, various solutions are used, including the use of electrokinetic process. The result of the electrokinetic process in the soil is the movement of water, ions and charged particles due to the difference in electrical potential. In this study, the purification of diesel-contaminated clay by electrokinetic method in the presence of ABTS and saponin surfactants is investigated and the effect of pH control on catolite and anolite on the electrokinetic modification process of clay is evaluated, The results show that in the absence of the surfactant, the electrokinetic method has a very low removal efficiency of 3% to 7%, but in the presence of the surfactant, the efficiency is significantly increased by 20% to 54%, with pH control in Velit. and anolyte and the amount of active substance increase the level of efficiency of diesel removal from soil. With the use of Saponin, the lowest amount of removal at a concentration of 0.05% equal to 20% has been obtained, while ABTS has been able to remove about 54% of diesel at the highest concentration of surfactant (0.15%), in the continuation of the research A uniaxial test has been conducted to determine the unconfined compressive strength of the soil sample, which shows that the cleaning process increases the compressive strength of the soil by 15%.

Today by increasing of earthquakes and population growth and development of building industry in city or country areas, building designing against applied loads especially earthquake load have regarded by engineers. Also for supplying of life and financial safety, buildings should have appropriate performance against applied loads. In this research work, influence of scaling of near-fault and far-fault records have been treated in 4 codes 2800 Iran, 4th edition, ASCE07, IBC 2006 and UBC 97 Simultaneously. In this study 3 buildings have been used in 4,7 and 10 stories as indicators of low-rise and mid-rise buildings. The results show that in low-rise and mid-rise buildings Iranian earthquake code scaling has stricter rules to other regulations. By increasing of stories in tall -building (10 story) every four regulations has their own performance and could be maximum according to the kind and characteristic of earthquake (PGA, Mw). In fact, regulation of 2800 Iran, 4th edition, requires separated scaling rules for low-rise and mid-rise buildings. Drift ratio in ASCE07-10 has decreased %94 to 2800 Iran. Also this value for IBC2006 %93 and for UBC %89 has decreased.

Reduction and management of risk of industrial plant especially energy is an important concern. Probabilistic and reliability method are used in risk and cost estimations. Oil, Gas and Petrochemical plant are the most energy producer plants that are in focus of cost, life and operation. These plants consist of several units, parts and equipment’s. In order to study the risk of plants, it is needed to study the equipment’s. The main goal of this research is probabilistic seismic assessment of fixed horizontal vessels. In this paper, finite element model of designed and constructed vessels in a real project is prepared and incremental dynamic analysis (IDA) is performed. Response of vessels components including the vessel body stress, piping stress, flange and elbow deformations, anchor bolt stress are extracted and their related limit state are defined. Finally the fragility curve of vessels components is prepared. The result shows that flange connection is the components that are potential for starting the damage of vessels.

The computational centers in the multiquadric radial basis functions meshless method have high adaptability considering the lack of geometric and physical connection between the centers. In this research, a new adaptive algorithm is proposed based on the gradients of the physical variables of the problem with the aim of creating an optimal distribution. The resulted adaptive distribution generated by this algorithm improves significantly the accuracy and speed of the multiquadric method compared to the uniform distribution in steady and unsteady problems. In this approach, firstly, the domains with low and high physical variations are identified in a known time step, then the number of computational centers decreases and increases in these areas, respectively. Thus, the centers will be distributed more compact where needed and will be eliminated where not. Facing another important challenge of the multiquadric method, i.e. determining the optimal shape parameter, a simple and efficient method is introduced in such a way that there is no need to optimize the shape parameter at each time step and the computational costs are controlled. Finally, the effectiveness of the proposed method is shown by solving examples of diffusion, convection and convection-diffusion equations. The results are compared to their uniform distributions by measuring their efficiency and to the exact solution by evaluating the accuracy.