میلاد همتیان

Road network is one of the main infrastructure developments and it is considered as the national capital. Maintaining this huge capital requires long-term planning and continuous activity of maintenance. In the past, traditional maintenance methods were focused on activities intrinsically or structures. Because preventative maintenance measures to increase pavement life-time service-systems and decrease the cost of long-term facilities, the theory carry out maintenance before the start of the collapse of the pavement is been considered by managers. Crowded intercity routes of Mazandaran province, especially in the tourist region studied in this research that was chosen because of high traffic and vehicle traffic. In order to solve this issue, after coding in MATLAB software, based on mathematical models and algorithms different states based on different period, the number of choosing the path of repairs category and a limited budget is defined, then desired results is obtained. The characteristics of solutions is defined in different states and changes in cost, utility and total number of selected routes as well as maintenance paths of selection from each category is analyzed.

Maintenances are necessary to ensure the safety and serviceability of existing bridges. With the increasing number of existing bridges, maintenances cost a large proportion of financial fund and have significant impact on environment. Bridges like any other structure and perhaps more than most of them are affected by environment. Because they belong to sensitive and high costly structures, failure to maintain them will have devastating effects. Bridges are needed continuous maintenance in order to service properly during its life cycle. Therefore, in this study, the issue of maintenance and repair of urban bridges in Mazandaran province has been studied with regard to life cycle cost and reliability of bridges. To do this end, a mathematical programming model which is include minimizing maintenance and user costs as well as maximizing system reliability. In order to solve the proposed model, a multi-objective particle swarm optimization algorithm is developed. Also, a sensitive analysis is done on failure rate. Results show that increasing in this parameter cause to increasing cost and decreasing reliability, This indicates that the proposed algorithm is working properly and the results of this research can be trusted.

The bridges as important links are connected all road networks and railways That a huge investment is needed to build them. In addition, bridges are considered as important points of vital arteries. If the bridges due to old age, exhaustion, overload, weather conditions, natural disasters and etc. destroyed, repair works are much more costly than the budget needed for the maintenance of them. Available budgets for reconstruction and maintenance, usually is not enough to maintain a constant state throughout the lifetime of the bridges. Due to the large number of bridges and high maintenance costs, it is not possible to repair and pay for maintenance of bridges simultaneously. In this study, the life cycle cost is calculated based on maintenance period of railway using multi-objective particle swarm optimization algorithm. Sensitivity analysis, furthermore, is done on deterioration rate and reduction of deterioration rate and effect of these parameters on system performance are analyzed.

One of the most important issues discussed in construction management companies is the prioritization of projects and the allocation of resources among the organization so that through this selection the profit of the organization will be maximized. Construction Projects due to the close relationship among the parameters of the project and the unknown exterior environment; they encounter uncertainties in complex environment. In as much as the issue of evaluating and prioritization of construction projects is a difficult problem, the network structure is a suitable approach to explain them. In other words, the assessment and prioritization of construction projects based on risk factors in the real world is a complicated problem with many quality and ambiguous characteristics. In this study, by investigating the criteria and indices of construction projects with optimal selection used in the literature of the subject and adapting them with the experts in the field with conditions and situation of the problem, six projects have been selected and investigated. The criteria used in the research include, the facility of the performance, time, finance, geographical location, the importance of structure and the employers popularity. In this project the Best-Worth approach was used to weigh the options, VIKOR method was used to solve the evaluation problem and to prioritize the construction projects. The presented model helps the decision makers to make more accurate decisions and to be able to prioritize the construction projects which are the important strategies of some organizations so that they can apply correct management.The results obtained by the Vikor method showed that the ten-storey building with one basement floor in Neka was the highest priority. Also, after solving the mathematical model developed in this research, it was found that the selection of the projects was performed in accordance with the scenarios considered and performed well.

In the last decade, various methods are created to optimize time, cost, and quality. Solving such a problem on large scale is too hard using traditional methods in logical time. Recently, researchers are focused on a meta-heuristic algorithm to solve time-cost-quality tradeoff problems. How to make a balance among time, cost, and quality parameters is so critical in construction project management. In this study, an invasive weed optimization algorithm is applied to solve the problem. In the proposed model, activity time is changed so that maximum usage of resources is obtained. In other words, it is possible to perform some activity simultaneously if their duration is increased which causes to decrease time, cost and increase project quality. Obtained results indicate the advantages of the proposed algorithm. Finally, to validate the proposed model a small size instance problem is created and solved by GAMS software optimally and compared with proposed algorithm results in MATLAB software. Results show that both Pareto solution obtained is almost identical, then it validates the algorithms for large scale problem.

Dynamic site layout is identifying the optimum location for temporary equipment, materials, and other available tools and offices at construction sites. The Site layout is classified as a dynamic problem because the necessary equipment is changed continuously during the project lifetime. Some research investigated this issue in recent years and tried to develop various algorithm to solve such problem due to its complexity. In this study, a linear programming model is proposed to minimize total transportation cost among different parts, relocation cost for moveable facility, and transportation cost between warehouse and other parts. An invasive weed optimization algorithm is developed to solve large scale problems. Computational results show that different layout is obtained based on priorities considered for each parts so that their layout can be changed if priority is varied. To validate the proposed algorithm, its results for small scale problem is compared with results obtained from solving it in GAMS software. Results obtained from proposed algorithm for small problem reveal that they are so close to obtained from exact method. Furthermore, scenarios analysis indicates that the proposed meta heuristic algorithm is outperformed, thus the proposed IWO algorithm can be applied for solving large scale problem in real world.

Considering that the mission of the project organization management is to create a commitment to the timetable, which prevents project delays and increases associated costs, and accept the fact that the delay in the completion time of the project results in the non-economization of the project, Therefore, the necessity of using proper planning and control methods seems necessary. One of the new methods used in project planning and control, which today focuses on many researchers, is the critical chain management method. In this research, multi-project scheduling with resource constraint in the critical-chain model has been investigated. In general, RCMPSP seeks to find the right sequence for project activities, so that the constraints of the priority of the project network and the various types of resource constraints in the project are met simultaneously. To this end, a multi-objective optimization model has been developed to solve this problem, with its stated objectives, the completion time of the entire project, the cost of the overall project implementation, and the quality of the implementation of the project activities. Also, the critical chain approach, as a new method of project management, has been used for project scheduling and particle swarm optimization algorithm for solving proposed model of this research.

The bridges with any form of structure that are designed and made with any kind of materials that are being manufactured, sooner or later, appear in their burnout effects, but in the type and extent of these exhaustions and their expansion, there are several factors such as conditions Atmospheric, flood or earthquake occurrence, increase in load over design, design quality, and type of materials affecting all of these factors, if not addressed, will lead to a reduction in the useful life of the structure. Therefore, handling bridges and timely maintenance of them will increase the useful life of the bridges. In this research, the evaluation bridges of Mazandaran province has been considered for the needs of maintenance. In order to carry out this research, firstly, the field visits of high importance bridges in Mazandaran province (more than 100 bridges have been investigated and evaluated in this research), and the failure and defect status of each of these bridges As well as the condition of these bridges against the factors such as traffic load and river bed, were studied. After conducting field visits and collecting the required results, we have studied the priority of each of the bridges in Mazandaran province regarding the need for maintenance. Also, in order to determine the amount of costs necessary for the maintenance of bridges, experts in this field were used and each bridge was evaluated separately and finally the amount of repair cost needed for each bridge was identified.

Nowadays traditional point of view is not able to meet the needs of construction project management. Therefore, the use of modern management approaches can be greatly helpful. The first step to reach this goal is to identify and verification variety of projects in terms of linear or network types, the difference in project and multi-project management, management and execute methods. In this research, critical chain management method is used instead of critical path method to provide more practical schedule. The proposed method solves a scheduling problem with time/resource tradeoff to provide a minimum-makespan deterministic schedule which will generally be a good starting point for project execution. Also to overcome the risk in the case, schedulers have a medium risk coefficient based on cognitive style. Anyway, the change of parameter β will give a little change in project duration. The proposed method is useful for both project planning and execution. The methods is simple, practical and can be easily computerized. It should be noted that although the advances in the field of computers and computing speed and information processing it is done, we still need to project manager and human using engineering vision, experience and knowledge can choose the best algorithm for each project to be felt.

Todays, transportation is one of the main elements of economic prosperity in the world and railway is one of the most important methods of transportation in Iran and in the world, which the main reason of its utilization is the appropriate cost against the capability of a great mass of goods and a large number of passenger’s transportation. Population growth and development of economic relations have led to increase utilization of transportation infrastructures, especially railways. Our country is not an exception and knowing that the railway system is one of the oldest transportation arteries, it is in danger of amortization and destruction. Bridges, as the most important road and railway infrastructure, have the most vulnerable in utilization increase phenomena that some signs of vulnerability are seen in parts of the railway system in recent years, and set the authorities thinking. The important point is that if regular maintenance and retrofitting programs in order to increase the capacity of these bridges are not arranged, it will lead to irreparable consequences. In order to help Iran bridge management system with considering all above issues, the present study prioritizes the need for maintenance and also optimization of corrective actions of the bridges of Zirab – Gorgan part in Garmsar – Gorgan line of north and north-east 2 Islamic Republic of Iran railway by the study on them. To do that, the multi – objective particle swarm optimization Meta-heuristic algorithm is used for the optimization of corrective actions. Also considering the four scenarios to select the number of bridges under repair and 16 conditions of problem to be solved by the defined algorithm, the proper and optimized conditions is introduced in different scenarios and budgets to use in maintenance strategies and the most effectiveness achievement.

Project planning and scheduling are one of the most important issues in construction engineering and management. It is being crucial to progress developed countries. One of the major challenges in construction project management is time and cost management. The traditional view lonely is not able to meet the needs of this field. Therefore, the use of modern management approaches can be greatly helpful. Time and cost are among the important objectives of each project. Cost and time trade-off is among the major important issues in projects planning and control and the main of solving this problem is actually analysis of interaction of different types of project costs and time of the project. In this paper, a time and cost trade off project scheduling problem under budget constraint is studied. For this purpose, a meta-heuristic genetic algorithm is developed to find the optimal solution in MATLAB. Completion time sensitivity analysis is done according to different budget level. In order to validate proposed algorithm, problem is solved by GAMS and the outputs between them are compared. The results show that proposed meta heuristic algorithm is able to solve problem optimally so that differences between samples solution were zero in different budget level.

All bridges designed by kind of structure and built by any type of materials, get burnt out sooner or later. These exhaustions are spread due to several factors such as atmospheric conditions, flood or earthquakes, increased over load more than expected in design phase, design and execution quality, and the type of materials affecting that causes to decrease bridge's useful life if these factors will be ignored. Therefore, bridge maintenance makes to increase its useful life if it happens on time. In this paper, Mazandaran province bridges are studied based on failure situation, faults of each bridges, their condition against traffic load and other effective variables.in order to solve the problem, first, required data have been collected by field study after bridges inspection and then bridges are prioritized based on fault evaluation criteria by Analytic Hierarchy Process (AHP) multi attribute decision making method. Finally, corrective actions are determined based on budget level for bridges. To achieve this goal, a linear mathematical programming model firstly presented and then to solve the large scale problem a genetic algorithm has been developed to find the optimal corrective actions. The proposed algorithm is implemented in MATLAB software and results show that the proposed genetic algorithm have suitable performance to solve the problem. Several budget levels have been considered to assess proposed genetic algorithm validation and changing trend of corrective actions number has been studied. It is seen that amount of effectiveness and total number of repairs are increased by soaring budget level

Today's traditional views alone can not meet the needs of managing civil engineering projects. Therefore, the use of modern managerial approaches can be largely controversial. The first step towards achieving this goal is to understand the types of projects in terms of line or network, the difference between managing a project with multi-project management and project management and implementation methods. In this research, the critical chain management approach has been used instead of the critical path method to provide a more practical timetable. In order to overcome uncertainty, the proposed method of fuzzy numbers in terms of the definite time of activity and knowledge of experts is used to model uncertainty over the duration of the activity. The proposed method, instead of replacing the initial deterministic scheduler with the fuzzy set time schedule, still holds the definite time schedule and simply arranges the project buffer to deal with uncertainty. The size of the project buffer is determined using calculations on fuzzy numbers. Also in order to overcome the risk in the case study, this study considers an average risk factor to meet the needs of the project buffer. However, changing the risk factor in different high, medium and low risk situations will have little effect on buffer size. In this study, in order to evaluate the model presented in this study, several linear-repeater construction projects were simultaneously studied and planned.