نشریه مهندسی عمران
سال پنجاه و پنجم شماره 10 (دی 1402)

Weirs are one of the types of hydraulic structures in water projects that with different cross section have been widely used as flow measuring, controlling and regulating of upstream water surface for turnouts devices, in conveyance water canals or body of dams. In this study, the hydraulic characteristics of flow over broad-crested weirs including the effects of different configurations of sloping crest and upstream and downstream ramps using of finite volume method (FVM) by the ANSYS FLUENT software was investigated. Numerical simulations were validated by experimental results. The results showed that discharge coefficient (Cd) for the BCW-UR-PSC and BCW-UDR-NSC weirs are higher than the BCW-UDR-HC weir. The average increase of Cd in BCW-UDR-NSC respect to BCW-UDR-HC in such a way that θ=-4.76° and- 9.46° is 18% and 25%, while the average increase of Cd in the BCW-UDR-PSC respect to the BCW-UDR-HC for same condition (θ=+4.76° and+9.46°) is 10% and 18%. It was found that both of the BCW-UDR-NSC and BCW-UDR-PSC, the Cd increases with steeper of the crest slope (or increasing θ). Also, the results showed that for BCW-UDR-PSC, value of Cd is 0.35≤Cd≤.47, however for the BCW-UDR-NSC, values of Cd are between 0.42≤Cd≤0.48. This shows that the Cd is affected by the sloping of the crest in such a way that negative slope respect positive slope has more impact in this increase. The average increase of the Cd in BCW-UDR-NSC respect to the BCW-UDR-PSC is approximately 8%.

After the process of holding tenders and concluding contracts and agreements and forming a project management team, the obligations, responsibilities and authorities of each of the effective factors or project stakeholders will be identified and separated thematically. Of course, it should be noted that the considerable amount of these obligations, responsibilities and authorities in each project is similar and the same. The uncertain and complex situation of claims in construction projects that will lead to financial issues and prolongation of work, requires all project stakeholders to have a clear approach in order to manage potential claims. In this study, after identifying the claims and rooting out the concepts related to the claim as well as how to manage it in contracts, the proposed model identifies and evaluates the project stakeholders and their ability to measure the claim using stakeholder social network analysis. On the other hand, by calculating the stakeholder centrality measure in each claim and summarizing them, the most important stakeholders and the relationship between them were identified that can be the basis of planning and management. Therefore, using social network analysis between project stakeholders and common claims, it is possible to identify the effective stakeholders and take the necessary actions to manage the claims.

In procedure for analysis, design and optimization of reinforced concrete buildings, for most or maybe all regular buildings, different parts of the procedure for different parts of the building, including main structure and its foundation, are usually carried out independently. This means that these structures are mainly analyzed and designed by supposing a fixed-base, and then, forces at the foot of columns are obtained and used to analyze and design the foundation. Thereby, no attention is paid to the effects of foundation settlements on the distribution of forces in structural elements. Interaction between the structure, the foundation and its subsoil (flexible-base), changes the actual behavior of the structure compared to the method in which the structure is investigated alone (fixed-base). In this paper, various RC buildings, including low-, mid- and high-rise types, with foundations and soil under their foundations in three different layers, with a depth of each layer equal to ten meters, are modeled using SAP2000. Also, all the frames are optimized using Artificial-Bee-Colony algorithm in MATLAB, subject to stress and drift constraints. The results show that, since in a structure with optimal design the values of stress in elements and drift of stories are usually very close to the maximum allowable limits, hence, a slight increase in structural response, induced by soil-structure interaction effects, may lead to the violation of optimal design constraints. Therefore, taking not into account such effects in design optimization of structure, may lead to not only a non-optimal but also an infeasible design.

The purpose of the present research is to investigate the damage analysis mechanisms of the Dam-Reservoir-Foundation system using the Finite Element Method (FEM). The study focuses on the Koyna dam-reservoir-foundation system, which is a two-dimensional model that has been subjected to the horizontal and vertical components of ground acceleration in the Koyna earthquake using ABAQUS software and the Concrete Damage Plasticity (CDP) model. The comparison of models in linear and linear analysis shows that considering the bottom of the foundation for applying the load increases the seismic damage compared to applying the bottom of the dam. The results indicate that applying foundation excitation at the contact surface of the dam-foundation in the condition of foundation without mass, as well as applying foundation excitation at the level of the rock foundation in the condition of massed foundation can lead to a more accurate prediction of the response of the structure during an earthquake. However, the level of seismic damage in the dam is greatly affected by how the base excitation is applied and the mechanism of the modeling Dam-Reservoir-Foundation system. Therefore, it is crucial to consider the correct application of base excitation and the modeling mechanism while analyzing the damage analysis of the Dam-Reservoir-Foundation system.

Nowadays, recycled concrete is used for the construction of many construction projects due to its low cost and environmental protection. In addition, self-compacting concrete is very important and useful due to the lack of vibration and the least possibility of creating large holes and voids. In this article, by combining these two types of concrete, its properties have been investigated. To obtain the compressive strength of concrete, non-destructive methods can be used, which can be much simpler, faster and without damage, however, there must be agreement between the destructive and non-destructive test results to be acceptable. In this article, the behavior of recycled and self-compacting concrete used in road concrete pavements has been investigated. For this purpose, the method of grinding and ultrasonic testing has been used and a comparison has been made between the results. The average compressive strength of 28 days in cement grade of 250 kg/m3 is equal to 25.2 MPa and in cement grade of 400 kg/m3 it is equal to 38.9 MPa, which has increased by 54%. Finally, it has been concluded that the results of sanding and ultrasonic testing in determining the compressive strength of concrete can have a difference between 7 and 17%, and usually the results of ultrasonic testing show lower values.

Annually, thousands of tons of rubber tires are producedconsumed, and disposed in Iran.In the past decade, researchers have conducted numerous investigations on the utilization of rubber fibers or rubber granules in concrete and their effects on its mechanical properties. Howeverthe concurrent use of these two materials in lieu of sand and gravel in concrete has not been thoroughly examined.This study explores the effects of simultaneously incorporating these two materials on the mechanical characteristics of rubberized concrete and investigates the environmental implications of rubber utilization in concrete.By examining the results of slump tests conducted on rubberized concrete specimens with water-to-cement ratios of 0.45, 0.50,and 0.55, and incorporating rubber granules and rubber fibers up to 25%, it was observed that the slump exhibited a decreasing trend from 31 to 82 millimeters. Test results indicated a reduction in compressive strength with increasing rubber content. Specifically,13% of the combination of rubber granules and fibers led to a reduction of around 50% in the compressive strength of rubberized concrete compared to the control sample. In the case of a water-to-cement ratio of 0.55, as the rubber granules and fibers were increased from 4 to 25%, compressive strength decreased from 15.78 to 3.19 MPa.Using different water-to-cement ratios and varying percentages of rubberized concrete in the software SimaPro, it was determined that the combination of rubber granules and fibers resulted in an approximate 40% reduction in carbon dioxide gas emissions in the environment.The optimum condition across all ratios was achieved by incorporating 4% rubber granules and fibers.

This paper examines the behavior of untreated and treated soil with cement and lime, as well as the relationship between the design parameters of the base layer such as uniaxial compressive strength (UCS), CBR with resilient modulus. The sample selection for the triaxial test was based on the results of UCS, Brazilian tensile, wetting-drying and freezing- thawing cycles tests. In general, the addition of lime along with cement causes the tensile strength to be halved compared to the addition of cement alone, but it eliminates the volume reduction problems caused by modification with cement. Also, a large-scale dynamic triaxial test was performed on the untreated base and C7L2 specimens. In all confining pressures, the values of elasticity modulus and damping ratio of C7L2 are higher and lower, respectively, compared to the untreated soil. The data points of ratio of modulus of elasticity-axial strain of sample C7L2 are above the corresponding curves for sand and even higher than the rock ones, and its damping ratio data points are above the corresponding curve for rock samples. The average values of the modulus of elasticity increase with the increase of confining pressure and initial axial stress. Increasing the loading frequency increases the Yang modulus, shear modulus, and damping ratio, but decreases the induced shear strain on the sample. The resilient modulus (in MPa) for dry untreated soil is equal to 10*CBR and for C7L2 is approximately equal to 20*UCS or 3*CBR in soaked state or 2.5*CBR in dry state for 1.25 mm penetration.

Collapsibility is the sudden volume change of the soil due to the increase degree of saturation. This phenomenon occurs in sands due to the grains sliding on each other and in clays due to the loss of electron bonds between particles. The percentage of soil collapsibility depends on various conditions such as soil type, mineral composition, moisture percentage, dry weight, stress applied during wetting, and the amount of initial soil moisture increase. This paper has been conducted to investigate the effect of nanomaterials on soil collapsibility potential. The soil was selected from the Allahabad region of Kerman in south east of Iran with a high loamy index. For this purpose, Nano-silica, Nano-clay, aluminum Nano-oxide, and Calcium-Nano-Carbonated additives with percentages of 0.5, 1, 1.5, and 2% were used to improve the soil. Double consolidation and direct shear tests were the two main criteria for evaluating the performance of nanomaterials. The results showed that the collapsibility index of the desired soil due to the addition of Nan- clay compared to the addition of calcium Nano-Carbonate, Nano silica, and aluminum oxide causes a greater decrease in the collapsibility index. Furthermore, the results obtained from the SEM images indicate that the collapsible soil has microscopic and macroscopic holes, which the addition of an additive destroys larger holes and creates a correlation between soil particles. This problem reduces the amount of collapsibility index.

Achieving perpetual pavements requires many factors, among which winter road maintenance is of great importance. In the past decades, the use of chemical deicers has been very common, but their use caused damage to many transportation infrastructures. In the present study, in order to investigate the effect of deicers on asphalt pavement, asphalt mastic samples were used due to their great influence on the viscoelastic characteristics of asphalt mixtures. The samples were conditioned for 96 hours at 60°C in solutions of distilled water, salt, Calcium magnesium acetate and Potassium acetate, and one sample was considered as a control, without conditioning. Then, all the samples were tested by frequency sweep test and the 2S2P1D viscoelastic model was fitted on the data. Analyzing the test results and model parameters showed that conditioning in brine solution softens the asphalt mastic samples. Calcium magnesium acetate increases the G* parameter at low loading frequencies (high temperatures). The effect of this deicer on the fatigue parameter is highly dependent on the loading frequency. The lower the loading frequency, the lower the mastic's resistance to fatigue failure. Potassium acetate increases the G* of mastic samples at medium and high temperatures. Also, all the deicers reduce the resistance of samples against rutting damage, and among them, Calcium magnesium acetate has the most damaging effect.

In the occurrence of geomechanical risks in underground mines, not only one factor, but a set of factors are closely related to each other. Therefore, choosing a suitable underground mining method and studying the relationship and interaction between the geomechanical and geological factors affecting it, before starting the mining process, can maximize profit and recovery, increase productivity, reduce production costs and ore losses, and finally create a safe environment for underground miners. Therefore, according to the importance of the subject, in this research, using the fuzzy DEMATEL method, the structure governing the factors was analyzed from the point of view of their influence and how they relate to each other, and also the importance of them. To implement this technique, first questionnaires were designed and distributed among experts, then 18 questionnaires were received to evaluate the factors. Finally, by implementing this method, the vectors of R, C, R+C, and R-C were calculated for each factor. The results show that the factors of discontinuity spacing and geological structures of the deposit have the highest (cause factors), and the criteria of Rock Mass Rating (RMR) and rock mass deformation modulus have the lowest impact (effect factors), respectively. The causal diagram drawn for the geomechanical factors influencing the underground mining method selection and the occurrence of geomechanical risks in underground mines, also shows that the Rock Mass Rating (RMR) factor has the highest prominence value and therefore has the most importance among all other parameters.