The Methodology of Using Value Engineering in Construction Projects Management

Construction projects are implemented in different countries with heavy costs and some of the projects have been relatively or absolutely unsuccessful and even faced with irreversible losses after construction. Maybe, it is due to complexities related to projects or other social-economic phenomenon. The present study revealed that value engineering can be used as a helpful tool from the beginning of studies to the end of designing, constructing, exploiting, and maintaining processes and overcome civil designs’ challenges and complexities. Value engineering is a method experienced in management that has an organized approach. Value engineering has a systematic and cooperative mechanism to analyze function and systems with the aim of achieving desirable function with the least costs. This study has attempted to briefly introduce concepts and executive process of value engineering in construction projects. Also, the study has attempted to investigate conventional methods of evaluating projects function and compare them convergence with value engineering to improve projects. Based on the research findings, it can be found that if we can expect to achieve projects objectives by spending the least cost and ensure the efficacy of investment in construction projects management sector as a main challenge of development plans in the third world countries through using engineering in appropriate time periods and in different phases.  

Copula Based Spatial Analysis of Drought Return Period in Southwest of Iran

In the past years, Khuzestan province which is located in the southwest of Iran has experienced severe droughts. Drought can be explained by its characteristics known as duration or severity. However, combination of the two features by probabilistic approach is appeared to be a well improved method to describe the phenomena. The aim of this study is to provide a more accurate statistical method of determining drought based on simultaneous analysis of two drought characteristics. Here, precipitation data from twenty stations were used to determine drought characteristics, by Standardized Precipitation Index (SPI). Joint probability function of two variables were built via copula functions. The drought return period was calculated in the form of two scenarios. The first scenario is, based on an assumption that drought is recognized by at least one of the two specific characteristics. Drought in the second scenario is distinguished by the two characteristics in a joint probabilistic form. According to research results, there was no significant difference between the north and south of Khuzestan in the study of single characteristics of drought. While analyzing two characteristics of the drought, the return period in the north was shorter than the south. The return period of droughts in the east was always shorter than in the west. The drought return period varies from 30 to 52 months and 50 to 87 months for the first and second scenarios, respectively

Performance Assessment of Shockwaves of Chute Spillways in Large Dams

Spillways are the most important structures of large dams that are responsible for releasing the excessive flood discharge from the reservoir. Although many studies have been performed to determine the flow characteristics over these structures, however, the available information on the shockwaves’ characteristics for spillways’ design is limited. The supercritical flow below the chute piers generates an aerated flow known as shockwaves. Due to the flow interaction with the chute piers, three kinds of standing waves just downstream of the pier, in the middle of the chute, and on the sidewalls are generated. This phenomenon affects the flow domain and its hydraulic characteristics along the chute spillway. The height of the waves increases downstream, where they hit the chute walls and reflect again into the flow to interact together again. The process repeated and intensified downstream in a lozenge shape. The height of these waves can be more than twice the depth flow and thus run over the sidewalls. This is important for the design of chute walls in chute spillways with control gates. In this study, the experimental formation of the shockwaves and their behavior along the chute and their reduction measures are presented. Experiments were conducted on a scaled physical model (1/50) of Kheirabad Dam, Water Research Institute, Iran. It was realized that apart from the geometry of piers and chute spillway, Froude number of flow and gate opening are the main effective parameters on the hydraulic performance of shockwaves’ formation and their development on gated spillways

Hydrodynamic Performance and Cavitation Analysis in Bottom Outlets of Dam Using CFD Modelling

Bottom outlets are significant structures of dams, which are responsible for controlling the flow rate, operation, or removal of reservoir sedimentation. The service gate controls the outlet flow rate, and whenever this gate is out of order, the emergency gate which is located at upstream is utilized. The cavitation phenomenon is one of the common bottom outlets’ problems due to the rapid flow transfer. The present research is a numerical study of the flow pattern in a dam’s bottom outlet for different gate openings by the use of Flow-3D software and RNG k-ε turbulence model. The investigation is carried out on the Sardab Dam, an earth dam in Isfahan (Iran). The maximum velocity for 100% opening of the gate and Howell Bunger valve is about 18 m/s in the section below the gate, and the maximum velocity for 40% opening of the gate is equal to 23.1 m/s. For 50% opening of the service and emergency gate in the valve’s upstream areas, the desired pressure values are reduced. Moreover, in the areas between the two emergency and service gates, the pressure values are reduced. The possibility of cavitation in this area can be reduced by installing aerators. The flow pattern in Sardab Dam’s bottom outlet has relatively stable and proper conditions, and there are no troublesome hydraulic phenomena such as local vortices, undesirable variations in pressure, and velocity in the tunnel, and there is no flow separation in the critical area of flow entering into the branch

Numerical Modeling of Failure Mechanisms in Articulated Concrete Block Mattress as a Sustainable Coastal Protection Structure

Shoreline protection remains a global priority. Typically, coastal areas are protected by armoring them with hard, non-native, and non-sustainable materials such as limestone. To increase the execution speed and environmental friendliness and reduce the weight of individual concrete blocks and reinforcements, concrete blocks can be designed and implemented as Articulated Concrete Block Mattress (ACB Mat). These structures act as an integral part and can be used as a revetment on the breakwater body or shoreline protection. Physical models are one of the key tools for estimating and investigating the phenomena in coastal structures. However, it does have limitations and obstacles; consequently, in this study, numerical modeling of waves on these structures has been utilized to simulate wave propagation on the breakwater, via Flow-3D software with VOF. Among the factors affecting the instability of ACB Mat are breaking waves as well as the shaking of the revetment and the displacement of the armor due to the uplift force resulting from the failure. The most important purpose of the present study is to investigate the ability of numerical Flow-3D model to simulate hydrodynamic parameters in coastal revetment. The run-up values of the waves on the concrete block armoring will multiply with increasing break parameter (0.5<ξm−1,0<3.3) due to the existence of plunging waves until it (Ru2%Hm0=1.6) reaches maximum. Hence, by increasing the breaker parameter and changing breaking waves (ξm−1,0>3.3) type to collapsing waves/surging waves, the trend of relative wave run-up changes on concrete block revetment increases gradually. By increasing the breaker index (surf similarity parameter) in the case of plunging waves (0.5<ξm−1,0<3.3), the low values on the relative wave run-down are greatly reduced. Additionally, in the transition region, the change of breaking waves from plunging waves to collapsing/surging (3.3<ξm−1,0<5.0), the relative run-down process occurs with less intensity

Hydraulic Performance of Seawater Intake System Using CFD Modeling

In recent years, tapping the sea for potable water has gained prominence as a potential source of water. Since seawater intake systems are often used in the infrastructure industry, ensuring proper efficiency in different operating conditions is very important. In this paper, CFD modeling is used to show general hydraulic design (flow patterns, stream flow, vortex severities, and pre-swirl) principles and performance acceptability criteria for pump intakes in different conditions. The authors explore scenarios for avoiding or resolving hydraulic problems that have arisen as a result of hydraulic model studies. The results show that the designer should make every effort to avoid small entrance and filtration areas from the basin to the intake forebay bottom, which could result in jet outlet and/or supercritical flow; too small logs at the basin outflow, which could result in high velocity flow jets; and sudden area contractions at the forebay to pump bay junction. There should be enough submergence at the pumps to reduce harmful vortex severities and pre-swirl. Curtain walls, baffles, fillets, and splitters, as well as flow redistributors, can all aid in improving approach flow patterns. Reduced flow separations and eddies will be greatly assisted by rounding corners and providing guide walls. Using a numerical model to figure out what is wrong and how to fix it will help the facility’s costs and maintenance decrease in the long run

Hydraulic Performance of Howell–Bunger and Butterfly Valves Used for Bottom Outlet in Large Dams under Flood Hazards

Floods control equipment in large dams is one of the most important requirements in hydraulic structures. Howell–Bunger valves and butterfly valves are two of these types of flow controls that are commonly used in bottom outlet dams. The optimal longitudinal distance (L) between the two Howell–Bunger and butterfly valves is such that the turbulence of the outlet flow from the butterfly valve should be dissipated before entering the outlet valve. Subsequently, the flow passing through the butterfly valves must have a fully developed flow state before reaching the Howell–Bunger valve. Therefore, the purpose of this study was to evaluate the optimal longitudinal distance between the Howell–Bunger and butterfly valves. For this purpose, different longitudinal distances were investigated using the Flow-3D numerical model. The ideal longitudinal distance obtained from the numerical model in the physical model was considered and tested. Based on the numerical study, the parameters of flow patterns, velocity profiles and vectors, turbulence kinetic energy, and formation of flow vorticity were investigated as criteria to determine the appropriate longitudinal distance. In addition, the most appropriate distance between the butterfly valve and the Howell–Bunger valve was determined, and the physical model was evaluated based on the optimal distance extracted from the numerical simulation. A comparison of the results from the numerical and the laboratory models showed that the minimum distance required in Howell–Bunger valves and butterfly valves should be equal to four times the diameter of the pipe (L=4D) so as not to adversely affect the performance of the bottom outlet system

Hydraulic Performance of Howell–Bunger and Butterfly Valves Used for Bottom Outlet in Large Dams under Flood Hazards

Floods control equipment in large dams is one of the most important requirements in hydraulic structures. Howell–Bunger valves and butterfly valves are two of these types of flow controls that are commonly used in bottom outlet dams. The optimal longitudinal distance (L) between the two Howell–Bunger and butterfly valves is such that the turbulence of the outlet flow from the butterfly valve should be dissipated before entering the outlet valve. Subsequently, the flow passing through the butterfly valves must have a fully developed flow state before reaching the Howell–Bunger valve. Therefore, the purpose of this study was to evaluate the optimal longitudinal distance between the Howell–Bunger and butterfly valves. For this purpose, different longitudinal distances were investigated using the Flow-3D numerical model. The ideal longitudinal distance obtained from the numerical model in the physical model was considered and tested. Based on the numerical study, the parameters of flow patterns, velocity profiles and vectors, turbulence kinetic energy, and formation of flow vorticity were investigated as criteria to determine the appropriate longitudinal distance. In addition, the most appropriate distance between the butterfly valve and the Howell–Bunger valve was determined, and the physical model was evaluated based on the optimal distance extracted from the numerical simulation. A comparison of the results from the numerical and the laboratory models showed that the minimum distance required in Howell–Bunger valves and butterfly valves should be equal to four times the diameter of the pipe (L=4D) so as not to adversely affect the performance of the bottom outlet system