The success of a project depends heavily on how effective scheduling is and how tightly the project can be controlled.  Poor scheduling can easily result in completion delays and cost overruns.  These in turn result in claims, counter claims, disagreements, and disputes.  The appropriate methods should be used in planning and scheduling a project; management decisions should not depend on experience and intuition alone.

 Highways, high-rise buildings, tunnels, and pipelines are good examples that exhibit repetitive characteristics where the same basic "unit" is repeated several times.  There is evidence that contractors avoid using Gantt charts and network schedules in highly repetitive projects because these projects are highly resource-constrained in addition to being time-constrained [Arditi, 1986].

 Gantt charts, the most commonly used method of scheduling and control in the construction industry, do not show interrelationships between the activities of a project.  This problem is exacerbated as the project size and complexity increase.  Construction managers who use Gantt charts have difficulties in changing or updating the data of a particular activity that may cause additional changes in other related activities.  The task of identifying which activities need to be modified or updated can accordingly be frustrating.  These shortcomings of Gantt charts are partially overcome if linked Gantt charts are used.  The outcome then is a network-like schedule that can partially solve this problem in complex one-off projects [Harrison, 1985].  The mechanics of generating and updating Gantt charts have also considerably improved in the last couple of decades as a result of recent developments in scheduling software.  Indeed the newest generation of commercially available scheduling software routinely generate Gantt charts that have actually been formulated as a result of CPM calculations.  Some of these software packages may even let the scheduler update or adjust the schedule by making changes directly on the Gantt chart while the system interacts with the CPM module built into the system and makes sure that precedence relationships between activities are not overlooked in this process.  Even though this new generation of Gantt charts appears to provide all the advantages of regular CPM networks, they certainly are not of much help in projects of repetitive nature.

 Network methods are very popular in larger projects but present complications in projects of repetitive nature such as high-rise building construction.  CPM-based techniques have been criticized widely in the literature for their inability to model repetitive projects [Selinger, 1980; Reda, 1990; and Russell and Wong, 1993].  The first problem is the sheer size of the network.  In a repetitive projects of n units, the network prepared for one unit has to be repeated n times and linked to each other; this results in a huge network that is difficult to manage.  This may cause difficulties in communication among the members of the construction management team.  The second problem is that the CPM algorithm is designed primarily for optimizing project duration rather than adequately dealing with the special resource constraints of repetitive projects.  Indeed, the CPM algorithm has no capability to assure a smooth procession of crews from unit to unit with no conflict and no idle time for workers and equipment.  This leads to hiring and procurement problems in the flow of labor and material during construction.

 The line-of-balance method (LOB) is a powerful tool for scheduling and controlling a con­struction project that involves repetitive activities.  Many researchers have dealt with various aspects of repetitive scheduling in construction [e.g., Wang and Huang, 1998; Hegazy et al., 1993; Thabet and Beliveau, 1994; Moselhi and El-Rayes, 1993; Mattila and Abraham, 1998; Hamerlink and Rowings, 1998; Russell and Wong, 1993; Harris and Ioannou, 1998; Harmelink, 2001; and Ammar and Elbeltagi, 2001] but LOB has been found to be difficult to use on projects that require a large number of trades or operations.  When applying the LOB method to repetetive construction, it is difficult to show all activities on one chart, especially in cases where concurrent activities exist.  There is a need to modify the LOB technique to handle complicated activity rela­tionships as well as concurrent activities.  There is a need for a modified LOB approach that will allow the user to organize the activities in a manageable way and that will eliminate the pro­blems faced in recent attempts to computerize the process.

             An attempt to develop a computer application was made by Psarros (1987).  It was limited to solve the basic LOB problem and was not designed to deal with the many implementation-related problems.  This application called SYRUS: A System for Repetitive Unit Scheduling was a pioneering attempt to prove that computer program can be developed but was not free from flaws.

             The second generation of computer programs was developed by Suh in 1993 and is called RUSS. RUSS is a menu driven program that is based on the general concepts of resource optimization.  The system has an analysis program written in "C" language.  The input that consists of several types of initial information is obtained from the user.  The program analyzes a "unit network" that represents the logical relationship among activities performed in one of the many identical units and calculates the production rate of each activity taking maximum productivity and learning effect into consideration.           

            RUSS solved most of the implementation related problems of SYRUS, but with the advancements in Information Technology (IT) tools, it needed to be improved further.  Especially the advances in web based project management applications made it necessary for a new generation beyond RUSS.  There are also some issues that can be improved by using recent programming tools, such as Visual Basic.  For example Suh (1993) mentioned the following possible improvements to RUSS:

·        In RUSS, simulating different alternatives is allowed by accessing the relevant file and editing the data in question.  Editing on the line-of-balance diagram directly by graphically changing slopes could help users simulate different alternatives.

·        The program accepts only activity network notation (i-node, j-node) when inputting unit network data.  However, precedence notation may be more convenient for some users. 

·        The learning curve model used in this research could be enhanced to reflect better the realities of repetitive-unit construction.

·        One potential area where this program can be expanded in the future is in receiving and printing progress information. 

All these can be improved using recent Object Oriented programming languages such as Visual Basic or C++.

             The main objectives of this study include the following:

·        Improving the previous versions of LOB tools such as SYRUS and RUSS.

·        Creating a new tool that has a better learning model.

·        Considering the latest developments in the Information Technologies and modifying the existing algorithms to accommodate these developments. A tool that can be used by construction managers easily over the web and that can be linked to other project management tools and work with them concurrently.

·        Testing the system through a questionnaire and validating the system. Such a survey will clarify the reasons of the construction industry’s reluctance to use LOB techniques. It can also be ascertained if a tool like this can have a generalized use in repetitive construction projects.

             There is evidence that linear construction has a repetitive nature that does not allow the efficient use of bar charts and network methods, which sometimes generate inaccurate and misleading information in repetitive situations.  Hence there is a need for more powerful methods of scheduling that will allow the user to make optimum use of time and resources, run the project efficiently, and monitor progress effectively.