نشریه مهندسی عمران
سال چهل و پنجم شماره 12 (اسفند 1401)

Broad-crested weirs can be used to make discharge measurements in irrigation canals; the entrance of stepped weirs or chutes is sometimes designed as a broad-crested weir structure. These structures are also sometimes used for the dam body. In this study, the Artificial Neural Network (ANN) and M5 model tree methods are used to predict discharge coefficients (Cd ) for broad-crested weirs. The results from these two models are compared with nonlinear regression equations. Four series of data obtained from different rectangular broad-crested weirs have been used and important dimensionless parameters have been defined. Results show that the ANN procedure is superior to the M5 model and regression approaches. The accuracy for ANN is quantified by R=0.966 and RMSE=0.038. All three methods are able to provide a reasonable prediction for Cd ; the M5 model tree provides four linear equations that can be used to estimate Cd . The shape of the Cd contours shows that the effect of weir height (P) exceeds that of the weir length (L).

The present study investigates the properties of cementitious mortars in which different portions of cement were replaced with mineral materials including electric arc furnace dust (EAFD), red mud (RM), marble powder (MP), and glass powder (GP). Compressive strength at ages of 7, 28, and 90 days, tensile strength at ages of 7 and 28 days, water absorption with durations of 30 minutes, 24 hours, and 72 hours after 90 days of curing, and chemical resistance against sulfuric acid tests were carried out on hardened specimens cured for 28 days. The results show that replacing 15% of cement with marble powder significantly increased the compressive strength of specimens cured for 7, 28, and 90 days. Furthermore, replacing cement with 5 and 15% glass powder or 5% of red mud increased the tensile strength. In order to investigate the performance of the repair mortars, one of them was chosen for strengthening RC beams. Three RC beams were manufactured and tested through 4-point bending scheme. The results indicate that the load-carrying capacity of the strengthened beam by CFRP sheet and repair mortar was the same as the specimen strengthened by CFRP sheet and epoxy resin, and was 60% higher than that of un-strengthened specimen.

Todays, due to the importance of the environment, the use of renewable energy generating structures has received more attention. Therefore, dynamic analysis of such structures under natural hazards, especially earthquakes, is important. One of these structures is wind turbine. In this article, its vibration is controlled by an active mass damper equipped with a magnetic fluid damper. The masses considered for this damper are equal to 10,20,40and60ton and two type of MR damper is considered. Performance of active mass dampers will be compared according to the evaluation indexes and the optimal active damper will be introduced. To model a wind turbine, a 5MW wind turbine constructed by the National Energy Laboratory Renewable is considered and the design of this wind turbine was linear and a multi-degree freedom model is used. this wind turbine is subjected to near and far field earthquakes in an out-of-plane direction then the vibration of this wind turbine is controlled by using these active mass dampers and the vibration of this wind turbine is controlled by active mass dampers. Finally, by using the optimal damper, which is located at the top of the wind turbine tower beside the nacelle, a significant reduction in the displacement and speed of the tower is observed.

Due to the particular topography of Kaleybar city, the water distribution network of this city has 7 pressure reducing valves that have been experimentally installed in different locations to manage the extra pressure in the network. In this research, the effect of the intelligent emplacement of pressure-reducing valves is investigated by using the valve selection index to reduce leakage and increase network reliability. The aim is to minimize hourly leakage by determining the optimal location and setting of valves, In addition to the minimization of leakage as the objective function, the minimum pressure restriction in three cases of no pressure restriction (minimum pressure restriction equal to 0 meters), water supply at the entrance of the building (minimum pressure restriction equal to 10 meters) and water supply for a four-story building ( minimum pressure constraint equal to 26 m) is considered as a penalty function next to the objective function. For this purpose, a combination of the ant colony optimization algorithm with the EPANET simulator in MATLAB has been used. The results show that with the intelligent emplacement of pressure-reducing valves in Kaleybar City, the leakage of the network has been decreased by 15.9 percent and the reliability of the network has been increased by 15. 5 percent, which shows the effect of intelligent operation planning on water distribution networks in improving their hydraulic performance.

Soils in nature can variably be in dry, saturated, or unsaturated conditions. In geotechnical projects, all three soil states must be considered, because soil states can be changed by environmental effects. The most elastoplastic models in soil mechanics were developed for saturated conditions. In this paper, a unified model, in a critical state framework is presented for describing the behavior of a large spectrum of soils under monotonic loading in drained and undrained conditions based on bounding surface theory and the nonassociated flow rule. To unified simulation of both clayey and sandy soils, among phase transformation behavior, in this model, a modified general dilatancy rule is used. In the current model, an effective stress approach is used that can easily consider both saturated and unsaturated states through effective stress parameter dependent on suction value. The proposed model considered the coupling effect of mechanical and water retention behaviors using soil water characteristic curve dependent on void ratio. To improve model accuracy and convergence, an implicit numerical integration scheme is used to implement the model. Using the experimental data available in the literature, numerical model predictions were shown to be in good agreement with the experimental results. The results showed that the proposed model was able to predict the characteristic features of the behavior of a wide range of soils, including smooth transition behavior from elastic to plastic state, stress softening and hardening, strain dilatancy, and also phase transformation behavior.

Composite special moment frames represent a novel type of special moment frames (SMFs) where a combination of concrete columns and steel beams is used. This paper evaluates the modeling of composite special moment frames and the behavior of the steel beam-concrete column connection. Due to the focus on hinge formation, the behavior of the connection with a hole drilled on the beam flange was analyzed. Numerical simulations were carried out in ABAQUS. The beam-column connection was subjected to one-five rows of holes. It was observed that the beam-column connection with three rows of holes had the optimal hinge formation behavior, stress distribution, and load. The connection with five rows of holes showed plastic strains in the first four rows, while the fifth row had no plastic strain. This suggests an increased drilling space since the fifth hole row did not contribute to the improvement of stress distribution uniformity. It was numerically found that the bending moment change varied from 8% to 46%; the model with three rows of holes had the lowest bending moment change, whereas the model with a single hole row showed the highest change in the bending moment. Moreover, energy absorption changed by 4-20%.

Based on a case study, the soil improvement operation under single foundations of a settled concrete structure has been presented using injected micropiles. Based on this, the effect of using micropiles in controlling the stress-deformation field created in the soil of the concrete structure has been studied. In order to evaluate the situation of the settlements, the necessary information was collected, including subsurface identification using geotechnical boreholes and settlement monitoring operations. The survey results before the soil improvement operations indicated the settlement of individual foundations and the continuity of the settlements. After the soil improvement operation, this trend reached zero. Using the Abaqus finite element software, a set of numerical analyses was performed on a concrete structure built on a loose foundation prone to destructive deformations in structural load-bearing members such as columns. In these simulations, in order to obtain the optimal performance of micropiles, the parameters of depth, diameter, and several micropiles were examined. The necessity of this research includes the decision to improve the soil of a settled concrete structure in the vicinity of the excavation based on the micropiles method or the destruction of the structure. The obtained results showed that the parameters of the length and number of micropiles have the greatest effect on the control of the deformation field and settlement of the structure. Also, the results show that the effect of the structure weight parameter on the interaction between the micropiles and the structure is significant.

Therefore, the effect of the freeze-thaw process on the physical and mechanical properties of materials should be taken into account in areas with the risk of this process. In this study, the effect of freezing-thawing process on the mode I and mode II fracture toughness and the strength parameters of travertine have been investigated. For this purpose, to investigate the effect of freeze-thaw process on the mode I and mode II fracture toughness, the specimens were affected by 0, 1, 4, 8, 16, 32 and 64 freeze-thaw cycles and the fracture toughness of the specimens using cracked chevron notched Brazilian disc was determined. To investigate the effect of freeze-thaw on the strength parameters of travertine, the samples were subjected to confining pressure of 0, 2.5 and 5 MPa. Also, microscopic studies were performed to more accurately evaluate and evaluate the structural changes of the samples due to the application of freeze-thaw cycles and their texture changes. The results show that with increasing the number of freeze-thaw cycles, the mode I and mode II fracture toughness decreases exponentially and also, cohesion and internal friction angle decrease. And microscopic studies show that the microcracks in the rock have expanded due to freeze-thaw and new cracks have formed.

The filling material of the columns is generally sand, gravel or crushed stone which are sometimes called stone columns or gravel columns. The implementation of this system is widely used in geotechnical engineering to increase bearing capacity, reduce settlement and accelerate integration. The use of industrial wastes such as steel slag in soil stabilization can be an environmentally friendly, sustainable and cost-effective technique for solid waste disposal. There are many studies which have been conducted on the bearing capacity and settlement of improved soils with stone columns with or without geosynthetic. However, a very limited number of studies on conventional stone columns and steel slag columns with or without confinement and geosynthetic under lateral loading have been investigated. In this paper, the lateral load capacity of steel slag granular column-sand environments has been investigated using a large-scale direct shear test device. The effects of column material type (steel slag and sand), column diameter and the type of geosynthetic on the shear strength parameters of column-sand composites have been investigated. The experimental results show the effectiveness of using steel slag columns to improve the lateral load performance of sand. The results indicate that the maximum stress increases by 20 to 70% and the internal friction angle increases by 200 to 800% compared to the sand without slag column with increasing the diameter of the column from 5 to 25 cm, respectively.

Due to its nature, mining operations are associated with many uncertainties. The effective factors in selecting the appropriate mining method in underground mines are also associated with uncertainties. The uncertainty associated with these parameters can cause various life-threatening/mortal and financial risks. Considering the risk and uncertainty related to these parameters, ranking and determining their importance, not only helps to choose the best (the safest and the most profitable) mining method before starting the mining process, but also to design a better and safer mine and reducing subsequent risks. Fuzzy parameters are generally estimated through expert knowledge, but the degree of confidence in the opinion of different experts is different and the uncertainty and difference in the reliability of their opinion cannot be ignored. In this research, Z-numbers Theory was used to solve the mentioned challenge. To conduct the present study, first the influencing factors in the selection of underground mining methods were studied and classified into 4 main groups of criteria, 13 sub-criteria 1 and 85 sub-criteria 2. Then, the Z-numbers theory was used to rank and determine their importance. After calculating the final weight of each parameter, in order to check the validity and accuracy of the findings, the results were compared with the parameters considered for choosing the underground mining method in Angouran mine. The results show that in each group of parameters, the more weighted factors (the results of the present research) correspond to the parameters related to choosing the mining method in Angouran mine.

High-resolution spatial and temporal precipitation data are essential for water engineering studies, hydrological modeling, and flood risk assessment, especially in tropical regions with complex rainfall patterns. Due to the lack of data, rainfall disaggregation is an important tool. In this study, the performance of multivariate rainfall disaggregation using MuDRain model and the effect of hourly correlation among stations on simulation accuracy in Hormozgan province were investigated. Comparison between observed and simulated hourly time series showed that the model evaluates the amount of daily precipitation accurately, but in most cases it simulated extreme amounts of precipitation less than the actual amounts. Furthermore, the enough number of heavy rainfall events has not been generated. Comparison of the results of selected dates with the highest rainfall showed that the Correlation Coefficient (R) and Nash–Sutcliffe (NSE) ranged from 0.1898 to 0.9319 and 0.0319 to 0.7251 respectively. Comparison of the hourly correlation impact showed that the accuracy of the model in simulating hourly precipitation was higher for time series having higher mean hourly correlation and the coefficients of R and NSE were 0.7816 and 0.5856, respectively, while these coefficients for time series with lower hourly correlation were 0.5155 and 0.2655 respectively. Generally, this model can be used with more confidence for areas with very high hourly correlations, in this case, the spatial correlation of the stations becomes an advantage, because utilizing the available hourly rainfall data in adjacent stations, it is possible to create series of realistic hourly rainfall at a desired station.

Earthquakes and damages caused by corrosive environmental conditions are two important factors that threaten the desirable performance of structures in the coastal cities of the Persian Gulf in southern Iran. Taking into account both of these risks in the analysis and design of structures can reduce the loss of life and can lead to significant economic savings. In recent years, studies on the probabilistic seismic vulnerability assessment of structures have been developed. In this paper, a risk-based approach is used for seismic evaluation of reinforced concrete moment frames with medium ductility that are exposed to damage due to base-chloride corrosion of longitudinal rebars in 4 important port cities of southern Iran (including Bushehr, Assaluyeh, Bandarabbas and Chabahar). A total of 18 reinforced concrete moment frames with different number of stories and in increments of 10 years after the initiation of corrosion, were subjected to increasing dynamic analysis (IDA). Then, using the risk integral, the annual probability of collapse for frames in the studied cities was obtained and evaluated. The results of this study show that over time after the initiation of corrosion, the probability of collapse of structures increases sharply, which indicates the high need for risk-based approach to evaluate and seismic design of structures that are exposed to damages due to aggressive environments.

Wind force is one of the lateral loads in the design of structures. One of the parameters for calculating wind force on structures is called pressure coefficient (CP), which is related to the geometry of the building. The design codes provide the pressure coefficient of conventional buildings. In the absence of these coefficients in the design codes, wind tunnel testing or numerical modeling should be used. Numerical method based on computational fluid dynamics (CFD) has been used in modeling to simulate wind flow.The model used in computational fluid dynamics in this research is the K-ε (Standard) model. The sphere is modeled with a diameter of 50 cm and the results of numerical modeling are compared with the results of the wind tunnel test presented in reference [2]. The dome is made with different height to span ratio, with increasing height to span ratio to maximum The negative pressure (suction) obtained at an angle of 90o increases as this value reaches –2.24 in dome 122, and it is also observed that at an angle of 150o to 180 o the pressure coefficient is constant for all domes. Finally, the equation the wind pressure coefficients of this type of domes is presented.

The selection of appropriate membership functions for fuzzy control systems has always been a topic of discussion among researchers and has been generally determined by trial and error based on the experience of the control system designer. In this study, the control performance of type-1 and type-2 fuzzy systems with different membership functions in semi-active fuzzy control of three- and nine-story structures under seismic excitation of the El centro, Kern County, Northridge, and Kobe earthquakes at different maximum accelerations Will be discussed. In this study, two fuzzy systems have been used considering the type of membership function as well as the number of defined membership functions for each input. The examined membership functions are defined symmetrically and at the same intervals for comparison. The results of the control systems used for the type-1 and type-2 fuzzy algorithms are examined and compared to the uncontrolled mode by considering the triangular, Gaussian, and trapezoidal membership functions. The results obtained from the defined evaluation criteria show that in general, type-2 fuzzy systems perform better than type-1 fuzzy systems, due to the consideration of uncertainties and the use of membership functions intermittently. is Fuzzy control systems with triangular membership functions have the best performance compared to other membership functions and the Gaussian membership function has shown close control function close to triangular function. Also, when more membership functions are used to determine the degree of membership of fuzzy language values, the fuzzy system becomes less sensitive to the type of membership function used.

Due to the increasing development of fiber-reinforced cementitious composites, studying their fracture behavior is necessary for the possibility of widespread use in the construction industry. In the present study, a new cementitious composite with strain hardening behavior has been fabricated. To reduce the adverse environmental problems, part of the cement has been replaced with pozzolanic materials such as blast furnace slag. Due to the fact that composites with high pozzolanic materials have lower strength at early ages than composites produced with ordinary cement, nano-silica has been used to solve this problem. Therefore, in this study, the effect of adding nano-silica on the fracture behavior of cementitious composites has been discovered. The double-k fracture method (DKFM) has been used to analyze the fracture behavior at different stages of specimen failure, i.e., crack initiation and stable and unstable crack propagation. In addition, the digital image correlation technique has been used to find the initial crack load and the crack opening displacement at different loading stages. The results show that the addition of 3% nano-silica positively affects compressive and flexural strength. In addition, it increases the toughness of the fiber bridging and reduces the brittleness of the composite.

One of the most critical environmental problems that human beings face is the subject of soil pollution, which occurs in various factors and affects different soil parameters. one way to tackle this phenomenon is the stabilization of soils. This study presents the result of using metakaolin geopolymer to stabilize contaminated clay. In this study, the basic and contaminated soil without stabilizing are subject to various tests; The results of the first phase of the experiments showed that increased contamination concentration had a negative effect on soil parameters. The results of these experiments also showed that the most critical concentration of soil contamination was among the concentrations of 10,000 ppm. Then the soil contaminated with the most critical concentration was stabilized by metakaolin geopolymer at 5, 10, and 15% weight and was tested with a stabilizer within seven days of curing time. The results showed that by increasing the percentage of metakaolin geopolymer, the soil strength parameters have significantly increased, and adding geopolymer to contaminated soil of 10,000 ppm has improved soil properties. In addition, the experiment results indicated that the 15% metakaolin geopolymer to the 10000ppm contaminated soil in the optimum value, in which the liquid limit increased by 39.47%, the plastic limit rose by 51.06%, and the plasticity index surged by 20.68%. Furthermore, the optimal moisture content increased by 19.84%, and dry Unit Weight decreased by 3.23% compared to the unstabilized 10000ppm contaminated soil.

Moisture damage is one of the main causes of many failures affecting the performance and durability of asphalt mixtures. This damage occurs with the entry of moisture (water) into the pavement layer and it intensifies other failures such as rutting and raveling in the asphalt mixture layers. Based on this, in this research, the impact of using different types of coal wastes (CW) as waste of its extraction process (Coal Jig and Coal Flotation Waste) on the performance of asphalt mixture, that's in facing the phenomenon of moisture damage has been investigated. After performing tests to identify the physical and chemical structure of CW, four different combinations of laboratory asphalt mixtures containing of CW were prepared. Coal Wastes in equal percentages were added to bitumen and surface free energy (SFE) and Fourier-transform infrared spectroscopy (FTIR) tests were performed on bitumen and the Indirect Tensile Strength (ITS) test was conducted on modified asphalt mixtures. The results of this study indicated that the use of Coal Jig Waste (CJW) compared to Coal Flotation Waste (CFW) increases the polar components of bitumen and increases adhesion as well. Also, the results obtained from the indirect tensile strength test indicated an improvement of resistance to moisture damage as a result of the using of Coal Jig Waste

Plastic concrete is a type of concrete that usually has high ductility and low permeability and it can be used in the construction of tangential piles in the excavations that have a high groundwater level. In many cases, the project conditions for using plastic concrete with proper mixing plan are not considered. The aim of this research is to present the optimal mixing plan in terms of mechanical and economic characteristics for plastic concrete piles. For this purpose, five different mix designs were considered for plastic concrete and the properties were evaluated. Finally, the group of tangential piles, including structural and plastic concrete piles with strut, was simulated in the vicinity of the deep excavation and the deformation and flow rate passing through the excavation wall were investigated. In two-dimensional simulation, it is not possible to consider the characteristics of the plastic concrete pile in the modeling plane and check the deformation of the pit wall between struts. For this reason, the simulation was done three-dimensionally. Results showed that if the groundwater level is kept constant, water infiltration into the project area is very low due to the very low permeability of plastic concrete piles and the subsidence and deformation created at the top of the piles as well as the swelling of the excavation bed is less than when the groundwater level is lowered. Also by increasing the permeability of plastic concrete piles and soil, the flow rate through the excavation wall increases.

Collapsible soil as an example of problematic soils can cause problems in structures. Collapsible soil may be stable before the presence of water, but after water enters, it experiences significant and sudden settlement. The most important issue in dealing with these soils is to predict their settlement. Up to now, various experiments have been designed in the laboratory or in-situ to determine the collapse potential, the most common of which is the oedometer test. The most important drawback of the existing experiments is the impossibility of simulating the pattern of water infiltration in the soil. In this study, an apparatus with a mold with a diameter of 14 cm and a height of 10 cm was built that has the ability to simulate water infiltration patterns and can measure the amount of collapse potential based on the source of water infiltration. This apparatus simulates water infiltration patterns into four categories based on the direction of water movement (from top to bottom or from bottom to top) and water distribution (point or expanding). The laboratory results of this apparatus on a sample of collapsible soil show that the collapse potential depends on the water infiltration pattern and it isn’t possible to use one collapse potential amount for all patterns. According to the laboratory results, the highest collapse potential is related to the pattern of water infiltration from top to bottom and expanding form, and the lowest is related to the pattern of water infiltration from bottom to top and point form.

Environmental, economic, technical issues and the limitation of energy resources and raw materials in the cement production process create the necessity of using cement substitutes, for this purpose three types of soil, namely sand with different ratios of silt or natural soil (Sx), soil cement stabilized (CSS), and geopolymer stabilized soil based on glass powder and calcium carbide (GSS) have been studied mechanically and dynamically. The strength, shear modulus and damping of the samples were studied under unconfined compressive strength (UCS) and cyclic triaxial tests under all-sided pressures and different shear strains and silt ratios of 10%, 25% and 50%. Different mixing plan of geopolymer materials for UCS test was prepared and the optimal proportion of mixing plan in which the resulting geopolymer includes the highest compressive strength of the soil was determined as the optimal geopolymer. Optimum geopolymer composite proportions in terms of maximum strength were obtained, consisting of 15% glass powder, 7% calcium carbide and 25% silt, which concentrations more/less than the optimum value reduce the compressive strength. The optimal compressive strength of soil-geopolymer was about 16% higher than that of cement-stabilized soil of 4%. Increasing the confining stress improves the shear modulus at small strains, while having little effect on the damping ratio. The compressive strength, hardness and shear modulus of geopolymeric soil was higher than that of cement soil. Shear resistance and damping of soils with different ratios of fine grain increases up to a certain level of threshold fine grain (50% silt).