Assume you are the construction manager for a building company contracted to build the Boulevard Strathfield Apartments project.
You should use the Precedence Diagram for the project.
Review the overall target schedule for the project carefully, and answer the following questions:
Project Overview
Task 1: Ground works
This task entails bulk excavation (removal) of rocks or soil and other materials (OTR) on site, moving the excavated materials, trimming, leveling and backfilling as needed.
- Measured material quantities
The total measured material quantity of ground work in this project is 4,500 m2. This comprises of volumes of all materials that will be excavated on the site and either used as backfill or carted away for disposal from the site. Assuming that the average depth of excavation is 0.5m then the volume of this work becomes: 4500m2 x 1.5m = 6,750m3.
- Productivity constants
The productivity constant for ground works entails productivity constants for excavation over areas (and removal of the cut), excavation in trenches (and removal of cut) and filling, returning and ramming of excavated areas in layers. The total productivity constant for ground work in this project is as follows:
Productivity constant = productivity constant for excavation over area + productivity constant in trenches + productivity constant for filling, returning and ramming
= 0.62 + 0.50 + 0.25 = 1.37 labour days per unit (m3). It is important to note that his includes travel, transport, storage, delivery and disposal of excavated materials (The Constructor, 2017).
- Tradesman hours worked
From the productivity constant calculated above, the number of tradesman hours worked for this task is calculated as follows:
1m3 = 1.37 labour days
2250m3 = (6750 x 1.37) = 9,247.5 labour days
Assuming that one labour has 8 working hours, therefore 9247.5 labour days will have:
9,247.5 x 8 = 93,980 hours
- Suitable gang size
The suitable gang size for this task is 18. This includes 1 supervisor, 2 excavator operators, 5 tractor/dumper drivers and 10 unskilled labourers.
- Needed time
Based on the above gang size of 2 excavator operators, the required time to complete this task is as follows:
Assume that the excavator capacity is 100m3 per hour and the operator works for 4 hours per day (considering rest hours),
In 1 day, the two excavators will have excavated (2 x 100 x 4) = 800m3
800m3 = 1 day
6750m3 = (6750 x 1)/ 800 = 8.4375 ≈ 9 days
Besides excavation, there is backfilling some areas as required, moving excavated materials to disposal areas, trimming, leveling and ramming the ground. These tasks are estimated to take 10 days. Therefore total time required to complete this task is (9 + 10) = 19 days.
- Review of task
This being among the very first task on site, its sequence is very simple and clear. The only predecessor is preliminaries, which include preparing accommodation facilities for workers, site fencing, site clearing, installation or moving of temporary services and removal of rubbish. The sequence of the task is appropriate for successful completion of the task. From the calculations above this task can be completed within 19 days, as opposed to 20 days that have been allowed in the program activity schedule. Therefore if I had to make changes, I would recommend that the number of gang for this task be 18 (1 supervisor, 2 excavator operators, 5 tractor/dumper drivers and 10 unskilled labourers). If there was adequate resources, I would recommend to select an excavator with a greater capacity. Greater capacity increases productivity of the excavator (Kharrazi, 2017). This would help in reducing the number of days needed to complete the task thus reducing project delivery period.
- Measured material quantities
Ground Work
The total measured material quantity of cement rendering to internal walls in this project is 5,800 m2. This comprises of cement and sand materials that will be required to plaster the internal walls of the building. Assuming that the thickness of plaster is 0.015m then the volume of this work becomes: 5800m2 x 0.015m = 87m3.
- Productivity constants
The productivity constant for plastering work entails productivity constants for mortar preparation and application. The total productivity constant for plastering work in this project is as follows:
Productivity constant = productivity constant for mortar preparation + productivity constant for mortar application (including mason)
= 0.75 + 0.08 + 0.10 = 0.93 labour days per unit (m3)
- Tradesman hours worked
Based on productivity constant, the number of tradesman hours worked for this task is calculated as follows:
1m3 = 0.93 labour days
87m3 = (87 x 0.93) = 80.91 labour days
Assuming that one labour has 8 working hours, therefore 80.91 labour days will have:
80.91 x 8 = 648 hours
- Suitable gang size
The suitable gang size for this task is 21. This includes 1 supervisor, 10 masons and 10 unskilled labourers.
- Needed time
Based on the above gang size of 10 masons, the required time to complete this task is as follows:
1 mason = 33m2 per day
10 masons = 10 x 33 = 330m2 per day
330m2 = 1 day
5800m2 = (5800 x 1)/ 330 = 17.58 ≈ 18 days
- Review of task
The sequence of the task is okay because this is a task that has to be done after completing ground works, concrete works, masonry works, metal works, hydraulics, electrical and mechanical works, water proofing works, PC items works and roofing works. From the calculations above, this task can be completed within 18 days as opposed to 31 days that have been set allowed in the program activity schedule. Therefore if I had to make any changes, I would recommend that the number of gang for this task be 21 (1 supervisor or foreman, 10 masons and 10 unskilled labourers). Also, I would ensure that all the necessary materials and equipment/tools for plastering are available on time to avoid any delays. I would make these changes because they would help in completing the project faster, which has positive cost implications.
This program is generally apposite as it encompasses all tasks that have to be completed in this project. Additionally, the tasks have been arranged in the right order in which they have to be completed. This is very important as it helps in avoiding delays or demolitions as the project progresses. However, the project program is only linear. This is a major disadvantage to project delivery as it does not allow capitalizing on fast-tracking or completing tasks in a parallel way (Agrama, 2011). From this program, most tasks can only be started after their predecessors have been finished. This means that there is no room for faster construction processes such as prefabrication or starting a task earlier as long as it does not interfere with its predecessors or successors. Many construction companies nowadays use technology to reduce project delivery period. As such, they avoid linear programs because they do not allow performing activities concurrently. For instance, when the masonry subcontractors are doing the walling, the roofing subcontractor can be concurrently prefabricating the metal roof so that it gets installed immediately the wall is completed. Prefabrication has become a major technique of reducing time and cost in construction industry (Chiu, 2012). In general, linear programs are suitable for construction projects with repetitive tasks (Kannan & Senthil, 2014), which is not the case for this project.
Cement Rendering
The duration allowed for most of the tasks in this program also seems to be inaccurate i.e. it is either less or more. Inaccurate estimation of duration has significant impacts on the project including costs. If a task is allocated less time, it will affect completion *of succeeding tasks thus extending the project duration. If it is allocated more time, some workers or equipment may remain idle at some point due to lack of raw materials because delivery period has not yet reached. Therefore this program has to be changed so that estimation of duration for each task is computed more accurately. Researchers have developed numerous methods that can be used for accurate estimation of project schedule (Zha & Zhang, 2014); (Zhang & Sun, 2008). These methods include Monte Carlo simulation and Monroe method (Castro, et al., 2008); (Kirytopoulos, et al., 2008). One of the approaches that these techniques apply is creating simulation models of the project schedule so as to maximize every resource available (especially time, workers and equipment).
Last but not least, it would have been better if the program was supported by a Gantt chart. A Gantt chart is a better tool of representing a project schedule as it shows the logical order of all tasks, duration of these tasks, connection between tasks, and how tasks depend on each other. This also helps in identifying tasks that can be started at any time without causing an interference to others (MacDonald, 2016).
Scheduling is very important in project implementation and management as it can break or make a project (Katz, 2010). However, many stakeholders in the construction industry understate realistic and optimistic scheduling (Linman, 2013). The schedule provided for this project is both realistic and optimistic. It is realistic because it has been adequately planned. The schedule captures all tasks with their estimated duration. Looking at the duration allocated for each take, it seems not to have been done randomly but there were considerable efforts made to estimate the time each task will take to be completed.
It is optimistic because all task have been systematically organized in the order from the first to the last. This shows how the tasks will follow each other in the order of completion. Based on this, the project team is hopeful that the schedule will help them implement and complete the project successfully. But despite it being both realistic and optimistic, the project is still exposed to uncertainty, which is inevitable in construction projects (Liu, 2012).
Analysis of Program Activity Schedule
Nevertheless, the information provided in the schedule is not sufficient to determine if the schedule is applicable in real-life situations. In construction industry, uncertainties cannot be avoided. This requires scheduling to consider factors, such as bad weather, sickness of workers, public holidays, unexpected political tensions, etc., which may cause delays.
Yes, I would accept this program but I would do a few things before providing it to the client or architect. The reason why I would accept the program is because it shows the systematic procedure that has to be followed in completing each task of the project. It encompasses also tasks and their estimated duration for completion. The first thing would be to recalculate the duration allowed for each task. I would find a suitable project scheduling software, model or technique to do this task. Secondly, I would create a simulation model for this program to determine its applicability in real-life situation. I would then do any necessary changes to ensure that the program is practical in real life situation. Last but not least, I would create a Gantt chart for this program.
Task compression is always necessary especially when the project experiences stringent timelines (Moselhi & Roofigari-Esfahan, 2012); (Webb, et al., 2015). However, the compression has numerous time, cost, safety and quality implications.
- Time cost and compression impacts of working overtime each day
Depending on the number of overtime hours worked every day, the number of day to complete ground works would be less than 19 days. Also depending on compression technique applied, the cost of completing ground works would definitely be more than the estimated $112,500. Other possible impacts of compressing this task include: fatigue of workers, injuries, accidents, near misses of excavators, damage or wear & tear of machines and equipment, and quality defects.
- Time cost and compression impacts of working 6 days per week
This would have the same impacts as above. The task would be completed in less than 19 days and the cost of completing task would exceed the estimated $112,500.
- Other ways to compress the project schedule
Other ways of compressing the task include: crashing and fast-tracking. Crashing means adding resources to activities such as leasing more excavators and dumpers/tractors and employing more excavator operators, damper/tractor drivers and unskilled labourers. Fast-tracking means completing activities in a parallel order instead of linear. Other techniques include: using additional work shifts, avoiding mistakes by enhancing supervision, use of more specialized crew, pre-work staff briefing, participative management, avoiding interruptions, ensuring just-in-time delivery of materials, improving maintenance of tools and equipment, and providing workers with incentives (Mansur, et al., 2015). The main disadvantage of these techniques is that it increases cost of completing the task.
Recommendations for Accurate Estimation and Representation of Project Schedule
Task 2: Plastering
- Time cost and compression impacts of working overtime each day
Depending on the number of overtime hours worked every day, the number of days needed to complete plastering work would be less than 18 days. Also depending on compression technique applied, the cost of completing ground works would definitely be more than the estimated $144,100. Other possible impacts of compressing this task include: fatigue of workers, slips and falls especially when working at height and quality defects.
- Time cost and compression impacts of working 6 days per week
This would have the same impacts as above. The task would be completed in less than 18 days and the cost of completing task would exceed the estimated $114,100.
- Other ways to compress the project schedule
There are several other ways of compressing the task. One of them is crashing. This technique involves adding resources to activities such as employing more masons and unskilled labourers, ensuring perfection in the first place, adding more plastering tools. Another technique is fast-tracking. This means completing activities in a parallel order instead of linear. Other techniques include: using additional work shifts, use of more specialized crew, pre-work staff briefing, participative management, avoiding interruptions, ensuring just-in-time delivery of materials, providing workers with incentives and using alternative plastering methods. Just like for ground works, the main disadvantage of these techniques is that it increases cost of completing plastering task.
References
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Castro, J., Gomez, D. & Tejada, J., 2008. A rule for slack allocation proportional to the duration in a PERT network. European Journal of Operational Research, 187(2), pp. 556-570.
Chiu, S. T., 2012. An Alaysis On: The Potential of Prefabricated Construction Industry, Vancouver: University of British Columbia Library.
Kannan, S. & Senthil, R., 2014. Production based scheduling method for linear construction in road projects. KSCE Journal of Civil Engineering , 18(5), pp. 1292-1301.
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The Constructor, 2017. Labor Requirement for Various Construction Works. [Online] Available at: https://theconstructor.org/tips/labor-requirement-building-construction-works/6906/[Accessed 3 May 2018].
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