COMPARATIVE STUDY OF TIME-COST OPTIMIZATION

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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 4, April 2017, pp. 659 663, Article ID: IJCIET_08_04_076 Available online at http://www.iaeme.com/ijciet/issues.asp?

1 International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 4, April 2017, pp , Article ID: IJCIET_08_04_076 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed COMPARATIVE STUDY OF TIME-COST OPTIMIZATION Veludurthi Manoj Kumar PG Student, Department of Civil Engineering, Manipal Institute of Technology, Karnataka, India Anup Wilfred S Assistant Professor (Senior Scale), Department of Civil Engineering, Manipal Institute of Technology, Karnataka, India Sridevi H Assistant Professor, Department of Civil Engineering, Manipal Institute of Technology, Karnataka, India ABSTRACT Construction planning is the most important phase in project lifecycle. Manpower, Materials, Machinery etc., should be planned during planning phase. Ideal tool used by construction planners are CPM& PERT methods to analyze and reduce the project duration. As the duration is reduced the direct cost of the project increases, this leads to the trade-off between the time and cost wherein the indirect cost of the project will decrease as the duration of the project reduces. There will be a particular point at which the minimum total cost of the project can be obtained at an optimum duration. Construction managers can explore this point at the planning stage to reduce the time and cost of the project. In this paper two techniques are used to achieve the time-cost relationship. The two techniques used are CPM (Critical Path Method) and Linear Programming Method. The CPM is done manually by reducing the duration of the critical path. The Linear Programming Method is solved by using two software which are M.S excel solver and Linear Program Solver (LiPS). The comparative analysis between the CPM and Linear programming method is done by using an example. Key words: Time-Cost relationship, planning, CPM, Linear Programming method. Cite this Article: Veludurthi Manojkumar, Anup Wilfred S and Sridevi H, Comparative Study of Time-Cost Optimization. International Journal of Civil Engineering and Technology, 8(4), 2017, pp INTRODUCTION The major constraints in a construction projects are time, cost and resources of the project. Generally, the construction projects are complex in nature it will get affected by time-cost overruns. The major reasons for the delay are inaccurate estimation, design faults, land problems, poor bidding and delay in financial flow, payment delays, inexperience, lack of editor@iaeme.com

2 Veludurthi Manojkumar, Anup Wilfred S and Sridevi H coordination, change in scope of work [2,3]. So, the management will face time-cost tradeoff problems. The main reasons for reducing the duration of the project are imposed project duration, unforeseen delays and to avoid high over head cost. The time-cost tradeoff majorly focus on reducing critical path [1]. Before 1950 the concept of time-cost relationship was neglected. After the invention of CPM (critical path method) the time-cost relationship has so much influence on construction projects because of its simplicity and easy understanding[4,5]. But this traditional methods have serious limitations such as it will assume unlimited resources which is very difficult to optimize when the project is more complex [7]. So, need for invention of new methods has arises due to huge competition in the construction industry. Many attempts the researchers have done to solve time-cost tradeoff problems. There are three types of techniques (i) heuristic method, (ii) mathematical methods and (iii) evolutionary methods [7]. The heuristic methods are the thumb rule methods, these are easy to understand and implement but they are unable to find the global optima. The mathematical models include linear programming, integer programming, linear and integer programming and dynamic programming. These methods will find the exact optima but it is having complex formulae and inability to consider discrete time-cost relationship. The evolutionary methods include Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Ant-Colony Optimization (ACO) etc., [7]. 2. PROBLEM STATEMENT Many optimization techniques are used to find minimum cost and optimum duration. This leads to confusion in choosing the type of optimization technique to be used. Here an attempt is been made to get faster and reliable results. Hence this study will give an idea to adopt a simple and easier optimization technique and helps the planners to take decision for finding optimum time and minimum cost to increase the profit margin. 3. OBJECTIVES Finding minimum cost and optimum duration by using critical path method [CPM]. Applying time-cost tradeoff by using linear programming method. Comparing the results of CPM and linear programming method. 4. RESULTS AND DISCUSSION An example is shown in table 1 and the cost slope is found for every activity. The direct cost of the project includes the cost of material, labor and equipment etc., and the indirect cost is the cost of rent, supervision, administration etc., it is assumed as 2000/week. Figure 1 shows the network diagram and dotted line represents the critical path. Table 1 Sample Example Activity Time (weeks) cost( ) Normal Crash Normal Crash Cost slope (Cs) A B C D E F G H editor@iaeme.com

3 Comparative Study of Time-Cost Optimization Figure 1 Network Diagram 4.1. Project Crashing Method The crashing of the project is done manually along the critical path. The initial crashing stage of the project is shown in figure 2 and there are total six stages of crashing was done. Figure 2 Initial Stage of crashing Fig 3 shows the 1 st stage of crashing, in this stage activity E has least cost slope along the critical path hence this activity crashed by 1 week. Figure 3 1 st Stage of crashing In 2 nd stage of crashing, activity G has been crashed by 3 weeks. In 3 rd stage of crashing, activity E and D has been crashed by 1 week. In 4 th stage of crashing, activity A and B has been crashed by 1 week. In 5 th stage of crashing, activity C and B has been crashed by 1 week. Fig 4 shows the 6 th stage of crashing, in this activity H has been crashed by 1 week. Figure 4 6 th Stage of crashing The direct cost, indirect cost and total cost of the project in every stage of project is shown in table 2 and the time verses cost graph is shown in figure editor@iaeme.com

4 Veludurthi Manojkumar, Anup Wilfred S and Sridevi H Table 2 Total cost in every stage of crashing Stage Duration(weeks) Direct cost( ) Indirect cost( ) Total cost( ) Figure 5 Time Vs Cost graph 4.2. Linear Programming Method Linear Programming deals with the maximizing or minimizing the objective function which is subjected to some constraints. Mainly the LP method consists of objective function and constraints. In this paper the LP model are as follows: Min = 1000YA+2000YB+1000YC+1000YD+1000YE+500YF+2000YG+3000YH. Subjected to, YA<= 1;YB<=2;YC<=1;YD<=1;YE<=2;YF<=1;YG<=3;YH<=1. Yi>=0; Xi>=0; Xstart>=0; Xfinish>=0; i = Activity A to H. XA-Xstart+YA>=2;XB-Xstart+YB>=3;XC-XA+YC>=2;XD-XB+YD>=4; XE-XC+YE>=4;XF-XC+YF>=3;XG-XE+YG>=5;XG-XD+YG>=5; XH-XF+YH>=2;XH-XG+YH>=2;Xfinish-XH>=0. Here, X represents earliest finish time and Y represents number of weeks that each activity can be crashed. To analyze the LP model, the M.S Excel solver and Linear Program Solver was used and the objective function and constraints are fed into the software. Table 3 shows the results of CPM and LP method. Table 3 Optimum cost and Minimum time Software optimum time (weeks) minimum cost ( ) CPM LP Method M.S Excel solver LiPS editor@iaeme.com

5 Comparative Study of Time-Cost Optimization 5. CONCLUSION From this study we can conclude that the results obtained from the both methods are same but LP method is better compared to CPM as it requires less computation time to obtain results in any type of the network. The CPM method holds good for small networks and there is no software to solve. Hence software developers can think about it. There are many software to solve the LP Method. In this paper, we have considered MS Excel Solver and Linear Program Solver (LiPS). Among this two software LiPS is the best solver than MS Excel because there is no need of applying formulae in the Linear program solver. Further this study can be carried out to compare the other software to solve LP Method and also there are many optimization techniques like Genetic Algorithm (GA), Particle Swarm Optimization(PSO), Ant-Colony Optimization(ACO) etc., researchers can compare these techniques with the CPM and LP Method. REFERENCES [1] Huang, J. W., Wang, X. X., & Zhou, Y. H. (2008, October). Research on time-cost optimization model of construction projects. In Wireless Communications, Networking and Mobile Computing, WiCOM'08. 4th International Conference on (pp. 1-4). IEEE. [2] Agyei, W., Project Planning And Scheduling Using PERT and CPM Techniques With Linear Programming: Case Study. International Journal of Scientific & Technology Research, 4(8), pp [3] Khang, D.B. and Myint, Y.M., Time, cost and quality trade-off in project management: a case study. International journal of project management, 17(4), pp [4] Raj, M.K.J.B. and Elangovan, N.S., TIME AND COST OPTIMISATION IN CONSTRUCTION USING MS PROJECT. [5] Yang, I.T., Performing complex project crashing analysis with aid of particle swarm optimization algorithm. International Journal of Project Management, 25(6), pp [6] Zhang, H. and Li, H., Multi objective particle swarm optimization for construction time cost tradeoff problems. Construction Management and Economics, 28(1), pp [7] Gonsalves, T. and Itoh, K., Cost Minimization in Service Systems Using Particle Swarm Optimization. In Software Engineering, Artificial Intelligence, Networking and Parallel/Distributed Computing (pp ). Springer Berlin Heidelberg editor@iaeme.com

Time and Cost Optimization Techniques in Construction Project Management

Time and Cost Optimization Techniques in Construction Project Management Mr.Bhushan V 1. Tatar and Prof.Rahul S.Patil 2 1. INTRODUCTION In the field of Construction the term project refers as a temporary