Year:2023 | Volume:53 | Issue:1|Papers Count:17

In this paper, a high-resolution version of the Godunov-type second-order Wave Propagation Algorithm (WPA) for one-dimensional macroscopic traffic flow modeling is presented. The method is a well-balanced model and is able to behave the source terms within the flux-differencing adjacent to the finite volume method. The defined numerical scheme utilizes the advantage of combination both approximate and exact Riemann speeds which enables the method to avoid non-negative velocities. To the best of authors’ knowledge, no development of WPA with high-resolution for the common macroscopic Payne- Whitham (PW) model and its extended versions has taken place so far.

Contractor selection for a construction project is among the most important factors in achieving the project’s success. In Iran, contractors for construction projects in public sector are mainly selected according to Tender’s Law. Despite the fact that a quality assessment is implemented through a prequalification phase, however, in the final phase of the tender process, “the lowest bid price” criterion reigns and the contractor with the lowest proposed price is considered as the eligible contractor to whom the contract of the project is awarded. The prequalification phase eliminates many incompetent contractors from the competition process, but this does not lead to a considerable improvement in the quality of construction because no responsibility is established for a better performance and the winner of the contract keeps meeting the minimum requirements. Contractor selection by the lowest tender is one of the main reasons for quality shortcomings, weak performance of the contractor, cost and time overruns, increasing in change orders and claims, conflicts, dissatisfaction of the client, increasing in life-cycle costs and other disorders and may finally lead to the project failure (Zavadskas et al., 2008, El-Sayegh et al., 2019, Hasnain and Thaheem, 2016, Scott, 2006). To overcome this, some multi-criteria decision-making methods have been proposed by many researchers. As a proposal for reforming the tenders’ process in the context of Iran, in this paper, VIKOR method is used for ranking of the alternatives in which “the proposed price” criterion is added to the assessment criteria which are commonly used in the prequalification phase. An illustrative example from water industries in East Azerbaijan province confirms the applicability of the proposed method.

Bucket foundation is a new foundation concept developed in the last decade for offshore wind turbines. Due to easy and faster installation with significantly lower expenses compared to the conventional foundations such as gravity bases and mono piles, suction caissons foundations are reliable and alternative foundation solutions. In this study push-over analysis was utilized to investigate the response of a typical monopod offshore wind turbine foundation under monotonic loading condition. Finite Element Method was used to define and analyze different scenarios.

The area of Lake Urmia, as the largest closed lake in the world, has significantly reduced in the last three decades, and this trend has had in-depth effects on environmental characteristics of the areas around the lake. During the last two decades, macro-climatic changes in northwestern Iran, and the involvement of anthropogenic factors such as dam construction caused extensive changes in the volume of water entering the lake and the area of water zone along with increasing salt concentration (Mardi et al., 2018; Sotoudeheian et al., 2016; Alkhayer et al., 2019; Boroughani et al., 2019; Mardi et al., 2018; Delfi et al., 2019). The changes in the area and volume of water of this lake on an annual and seasonal scale have had significant effects on the soil, climate and vegetation quality of the areas around this lake (Tourian et al., 2015; Eimanifar and Mohebbi, 2007). Therefore, the effects of dust due to drying of Lake Urmia can affect air quality around the lake up to a radius of hundreds of kilometers both directly by creating internal dust centers (usually dust from salt deposits) and indirectly by weakening vegetation. Also, emit a wave of salt dust in the air of some cities adjacent to the lake, which has a population of nearly six million persons who are directly and indirectly affected by the consequences of the drying of this lake.The main objective of this study was to identify the relationship between dust storms in the eastern part of Lake Urmia and the surrounding vegetation due to the annual and long-term variability of this water zone during the statistical period 1999-2019.

Tabriz marl soil are Lake Carbonated sediments. The percentage of organic matter in this soil is less than 6%; and does not fit into the classification of organic soils. The carbonate content of this soil is from 10 to 35%. The classification of this soil is mostly CH and in some cases MH (Mahouti and Katabi, 1397). Dredged soil is not much different from conventional fine-grained soil and can be used in a variety of applications with stabilization. Due to poor geotechnical properties; they are stabilized for use in dredging materials in engineering applications (Chan and Shahri, 2016). To stabilize the soil; Stable stabilizers (such as steel slag and industrial waste) have been proposed to replace cement. In the meantime, the environmental compatibility (safety in terms of pH and harmful substances, such as heavy metals and toxic substances) of BOF slag (as soil stabilizer and filler) has been confirmed. Therefore, the use of steel slag; In addition to reducing project costs and environmental problems caused by lime and cement production (reducing CO2 emissions and energy consumption), it does not pollute the environment and eliminates the problem of accumulation of by-products of the industry (Proctor et al., 2000; Motz and Geiseler, 2001; Kang et al., 2019).

In general, despite their seeming insignificance, there are some details in the ground that have significant effects on soil-foundation system behavior such as slip surfaces, shear bands, and thin layers (Valor et al. 2017). Terzaghi (1929) termed “these features minor geologic details and pointed out their enormous potential effects on the safety of dams”. In the literature review very little study has been performed on the effects of a thin layer (Valor et al. 2017, Ziccarelli et al. 2017, Oda and Win, 1990)In the present paper, the influences of the horizontal thin layer on the ultimate bearing capacity of the circular foundation resting on the sandy bed were studied by implicating a small-scale physical model for the soil-foundation system. The problem of the soil- circular footing system is schematically illustrated in Fig. 1. The problem is investigated under the axisymmetric condition, and the circular foundation is rigid. This foundation rests on the ground surface, on the other hand, the initial depth of embedment is nil. The studies were performed by the material type, thickness, and depth of the thin layer variation. For the bed sand, crushed uniform silica sand (SP) with medium density was used. For the thin layer, materials with different strength properties (strong and weak) in comparison with the sandy bed were used.For the weak layer, the clay powder with CL classification was used. Clay with a natural moisture content of 5.5% and a very low density of 12.1 kN/m3 was used consistently in all of the experiments.For the strong layer, a fine-grained asphalt mixture with an unconfined compressive strength of 1460 kPa and unit weight19.12 kN/m3 was used.

The high demand for more exploitation of coastal areas has increased the need for extensive and varied studies and research in these areas. The study of different parts of the coasts is not only important as an independent research (Alizadeh et al., 2012), but can also be used to advance other research on the hydraulic and hydrodynamic issues of the sea such as depth change, bed characteristics, wave breaking (Azarmsa and Yasuda, 1997), marine sedimentation pattern (Vaselali and Azarmsa, 2009), alongshore coastal sediment transport (Sadeghifar et al. 2013), and shoreline positioning (Azarmsa and Razmkhah, 2006; 2010) will be effective. The results of these studies are applicable even in practical and economic contexts. The purpose of this research is to study the slope of the swash zone of waves in the Noor beach in the cold season.

In this study, 6 mixing designs including 1 design of control concrete containing Portland cement, 3 designs of geopolymer concrete containing 0 to 8% nanosilica and 2 designs of slag geopolymer concrete containing nanosilica and 1 and 2% of polyolefin fibers were made (Mansourghanaei et. al., 2022; Mansourghanaei et. al., 2022; Mansourghanaei et al., 2022). In line with the prepared mixing plan, 54 concrete specimens were made for impact test (each test averaged the results of 3 concrete specimens) and 24 concrete specimens were made for compressive strength test (each test averaged the results of 4 concrete specimens) which at the age of 90 Fasts were tested and evaluated. It should be noted that for SEM and XRD tests, shredded tests were used. Concrete compressive strength test was performed at room temperature and impact weight test at room temperature and temperature of 300 and 600℃. In the drop weight test, parameters such as impact energy due to initial cracking and failure, adsorbed energy and flexibility index of concrete samples were calculated and evaluated. In order to study the microstructure and verification of the results of hammer impact test, XRD and SEM tests were used on concrete samples.

Climate change has caused changes in the frequency and magnitude of heavy rainfall, which affects the design standards of some hydrological structures (Yousef and Taha, 2015). Rainfall intensity-duration-frequency (IDF) curves are a standard tool for hydrological risk analysis and design (Mohymont, 2004; Veneziano, 2002). IDF curves show useful information about the occurrence of floods in an area and that in the future a certain amount of rainfall or a certain volume of flow will return again (Basumatary and Sil, 2018). Because the trend of severe rainfall events is expected to change in the future, this affects IDF curves, so these curves need to be updated (Srivastav et al. 2014). The need for such an understanding stems from the fact that existing drainage systems are designed to deal with past rainfall events and may not be sufficient to compensate for future rainfall characteristics (Shrestha et al. 2017). In developing countries such as Iran, the large country area as well as the shortage of rain gauge stations and/or the statistical period of the recorded data, makes it difficult to estimate IDF curves (Zamani Nouri, 2011).

Groundwater recharge from rainfall and the return flow of irrigation is essential for sustainable water resources management, groundwater modeling. Quantification of the rate of ground water recharge is a basic prerequisite for efficient ground water resource management. The rate of aquifer recharge is one of the most difficult components to measure when evaluating ground water resources. Numerous techniques are used to quantify recharge rate. One of these techniques is the cumulative rainfall departure (CRD) method. This method is considered to be one of the most promising and attractive due to its ease of use and low cost of application in semiarid areas. Numerous studies have been carried out to estimate groundwater recharge from rainfall. The CRD is a water balance method which depends on groundwater level fluctuations in shallow aquifers as a function of rainfall. Xu and van Tonder (2001) and Rasoulzadeh and Moosavi (2007) used the revised CRD method and Ahmadi et al. (2014) applied the CRD method to assess groundwater recharge in arid and semi-arid region.

One of the purposes of this study is to investigate the effect of the FRP use in order to increase the ductility capacity and reduce the ductility demand under dynamic loads. In this order the maximum ductility demand in the circular columns used in the bridges in the cases of use and disuse of FRP under far field earthquake records has been investigated and the effect of this application on the ductility demands has been determined quantitatively. By using the results of this study, the effect of FRP using in increasing the lateral strength of these columns has been investigated quantitatively. In the following, the columns damages in the cases of use and disuse of this polymers has been investigated quantitatively using an appropriate damage index and the effect of their use in reducing seismic damages has been studied. Finally, using incremental non-linear dynamic analyses on these columns considering confinement due to the polymers, seismic performance level such as operational, Immediate Occupancy, life safety and Collapse Prevention limit states has been investigated and the effect of using FRP in bridges circular columns on the improvement of their seismic performance has been evaluated.

Self-compacting lightweight concrete (SCLC) is one type of concrete that its usage has widely increased. The use of some additives in the production of SCLC can both reduce its costs and improve its properties. The effects of different cement replacement materials have been studied by several researchers. Jalal et al. (2012) claimed that the use of silica fume could improve the electrical resistance and mechanical properties of self-compacting concrete, and reduce its water absorption. Moreover, the use of silica fume in normal concrete improves the bond between aggregate and paste surfaces, and it has positive effects on fracture toughness, compressive strength and tensile strength (Lam et al., 1998). To simulate the fracture behavior of concrete in numerical models of concrete, depending on the model, some parameters such as fracture energy, fracture toughness and critical effective crack-tip opening displacement ( or δc), which generally are known as fracture parameters, must be determined. In this regard, Peterson (1980) showed that the fracture parameters are significantly affected by water to cement ratio (w/c) and the quality of aggregate. In other words, by reducing w/c or using stronger aggregate, the fracture energy of concrete increases. In this study, the effect of w/c and silica fume on the fracture toughness and fracture energy of SCLC has been investigated. Therefore, by making six mix designs and 126 concrete specimens, fracture parameters, mechanical properties and the workability of fresh concrete were carefully studied. Initially, four mix designs with the w/c of 0.37, 0.42, 0.47 and 0.52 were made. Afterwards, by replacing 0, 5% and 10% of the weight of cement with silica fume, the effects of changing this parameter on the fracture parameters of SCLC were studied.

Today, Iranian employers and contractors using the EPC method in several large and small projects, need to analyze previous experiences to correct the problems of this method and develop it in future projects. In this research, first, by identifying the common lawsuits between the group of consulting engineers and contractors in the country's construction projects and ranking the existing lawsuits, it analyzes and examines it so that it can provide solutions for reforming the country's technical executive system by carefully examining the influential factors. The indicators obtained through library studies and face-to-face interviews with experts will be identified in the form of 4 general categories (level one) and 24 sub-indicators (level 2), after collecting information about all options. According to the determined indicators, in order to evaluate and select the most preferred index by the relevant subgroups and prioritize them, decision criteria with multiple indicators have been used. In this research, using AHP method, the indicators presented in this topic have been identified and then prioritized and weighted. The criterion of non-fulfillment of contractual obligations of employer and consultant with weight (0.523) is the most important criterion in analyzing and reviewing claims. Common among us consultants and. Contractors in EPC contracts are construction projects and the wrong factors in the tender documents with weight (0.089) are the least important criteria among the 4 main criteria available.

Probability density functions of the involved random variables are essential for the reliability-based design of offshore structures. The objective of present research was the derivation of probability density function (PDF) for the local joint flexibility (LJF) factor, fLJF, in two-planar tubular DK-joints commonly found in jacket-type offshore structures. A total of 162 finite element (FE) analyses were carried out on 81 FE models of DK-joints subjected to two types of axial loading. Generated FE models were validated using available experimental data, FE results, and design formulas. Based on the results of parametric FE study, a sample database was prepared for the fLJF values and density histograms were generated for respective samples based on the Freedman-Diaconis rule. Nine theoretical PDFs were fitted to the developed histograms and the maximum likelihood (ML) method was applied to evaluate the parameters of fitted PDFs. In each case, the Kolmogorov-Smirnov and chi-squared tests were used to evaluate the goodness of fit. Finally, the Inverse Gaussian model was proposed as the governing probability distribution function for the fLJF. After substituting the values of estimated parameters, two fully defined PDFs were presented for the fLJF in tubular DK-joints subjected to two types of axial loading.

One of the issues that has been considered in the construction and improvement of pavements in recent decades is the use of recycled materials in the pavements. In this regards using RAPs is widely interested by many agencies and policy makers to recycle the waste materials and reuse of this valuable aggregated coating by bitumen. According to previous studies, the generally accepted criteria for the design of pavement structures containing a stabilized foundation are based on the allowable values and limits of unconfined compressive strength (UCS), and generally control according to durability criteria. The point to be noted here is the limited number of studies that examine the issue of durability and its impact on the mixing design and determining the optimal amount of RAPs. The purpose of this study is to investigate different durability criteria for cement-stabilized mixtures containing RAPs and to determine the optimal values of RAP and cement in terms of durability of such mixtures.

Resource leveling is very important in projects and project managers always need a schedule based on the optimal use of resources needed to complete their projects. Most resource leveling research has been done in a single project, while in many organizations several projects are done simultaneously. For this purpose, a mathematical model is presented by all projects with the aim of minimizing changes in the level of different resources. Leveling and allocating resources is one of the most basic tasks of project management. Typically, project management uses specific methods such as GERT and PERT to plan and control the project (Boctor, 1990). Because the problem of resource leveling is an NP-complete problem and it is not possible to achieve the optimal solution in the general case (Guo et al., 2012), the cuckoo optimization algorithm has been used, which is one of the newest and most efficient evolutionary optimization methods.

Compacted soils, which are commonly used in geotechnical engineering projects, such as earth dams, highways, embankments, and airport runways, are mostly unsaturated. To achieve a safe design in all these projects, the stress state variable in soil plays a significant role. Any proposed model for the stress state variable should express its independence from the soil properties. In saturated soils, the e effective stress is taken into account as the stress state variable. Some researchers have attempted to find the stress state variable for unsaturated soils the same as that for saturated soils with only one variable; however, they have noticed that the soil properties have been involved in the proposed models (Bishop, 1959; Escario and Saez, 1986; Khalili and Khabbaz, 1998; Lu and Likos, 2004; Rahnema et al., 2019). The purpose of this paper is to apply new intelligent methods to accurately estimate the effective stress parameter, using two gray wolf optimization (GWO) and sine-cosine (SCA) optimization algorithms.