Construction delays chapter six delay analysis using bar chart schedules

Construction delays chapter six delay analysis using bar chart schedules Construction delays chapter six delay analysis using bar chart schedules Construction delays chapter six delay analysis using bar chart schedules Construction delays chapter six delay analysis using bar chart schedules Construction delays chapter six delay analysis using bar chart schedules Construction delays chapter six delay analysis using bar chart schedules Construction delays chapter six delay analysis using bar chart schedules

CHAPTER SIX Delay Analysis Using Bar Chart Schedules Later in this book, we will explain how to perform a delay analysis when a detailed Critical Path Method (CPM) schedule was created as the original as-planned schedule for the project However, many projects are scheduled using a bar chart schedule (bar chart) For projects with many interrelated activities, a bar chart is not as desirable as a CPM schedule, because a CPM schedule records and preserves the relationships among the activities However, a meaningful and accurate delay analysis can still be performed using a bar chart With any schedule, as the level of detail and the quality of information decrease, the delay analysis becomes more subjective Therefore, a delay analysis that is based on a bar chart requires the analyst to guard against assumptions that favor one outcome or another and to work to be as objective as possible This chapter describes how a delay analysis is performed when the project schedule is a bar chart There is nothing inherently wrong with scheduling a project with a bar chart Bar charts were in use long before the Critical Path Method was ever created As some professionals are quick to point out, the Empire State Building was scheduled with a bar chart and not a CPM In fact, a detailed bar chart can provide almost as much information as a CPM schedule Fig 6.1 is a simple bar chart for the construction of a bridge Though it does not contain a significant number of activities, it does show the general sequence of work for the construction of the bridge Using this simple bar chart as a starting point, the project manager could easily define each activity in more detail Fig 6.2 is a more detailed bar chart of the project depicted in Fig 6.1 This more detailed bar chart more clearly defines the contractor’s proposed work plan In this bar chart, each major activity is broken down into the work on the respective piers and spans, providing the contractor and owner with a more detailed illustration of the plan for construction With very little effort, the project manager or project scheduler can modify the bar chart in Fig 6.2 to show the interrelationships among the activities, as shown in Fig 6.3 Construction Delays DOI: http://dx.doi.org/10.1016/B978-0-12-811244-1.00006-9 Copyright © 2018 Trauner Consulting Services, Inc Published by Elsevier Inc All rights reserved 109 110 Construction Delays Figure 6.1 Simple bar chart example Using this schedule as a foundation, a CPM schedule for the project could be produced with little effort Unfortunately, most bar charts for projects not contain as much detail as that in Fig 6.3, and often not even as much as the bar chart in Fig 6.2 In general, most bar charts suffer from the following major shortcomings that diminish their usefulness as a management tool and their effectiveness in measuring delays: • Lack of detail—too few activities for the amount and complexity of the work • No indication of the interrelationships among the activities • No definition of the critical path of the project Obviously, these weaknesses hamper the ability of the analyst to perform a delay analysis, but they not make it impossible If nothing else, the bar chart is helpful in that it defines the plan for constructing the project, and it can be used as the basis for an analysis of delays DEFINING THE CRITICAL PATH The first step in analyzing a bar chart is to define the critical path Every project has a critical path, including a project that was scheduled with a bar chart The following definitions illustrate this point Delay Analysis Using Bar Chart Schedules 111 Figure 6.2 Example detailed bar chart example BASIC CRITICAL PATH METHOD In CPM scheduling, the drafter of the schedule prepares a logic or network diagram As presented in Chapter 2, Float and the Critical Path, once durations are assigned to the activities in the network logic diagram, the critical path can be calculated It is a purely arithmetic process 112 Construction Delays Figure 6.3 Example detailed bar chart example with logic relationships The definition of the critical path is the longest path of work activities through the network diagram that forecasts the date when the project will finish The project cannot finish until every path of work has been completed Whether the critical path is defined in a CPM schedule or a bar chart, every project has a series of interrelated activities that will control the project completion date Delay Analysis Using Bar Chart Schedules 113 Also, the only way to delay the project is to delay an activity on the critical path of the project In understanding this concept, it is essential to recognize that the critical path of a project is dynamic In this manner, delays to noncritical activities that persist will cause the critical path to shift to the path containing that activity and, thus, will then delay the project IDENTIFYING THE CRITICAL PATH ON A BAR CHART Because we know that a critical path exists in a bar chart schedule, the delay analyst should first identify this critical path The analyst must review the bar chart in detail for obvious conclusions about the sequence of work These conclusions may be based on project documentation that might clarify the thought process that went into creating the bar chart or defining the planned work sequence Documentation that can be helpful includes the contract, which may dictate staging or phasing, the pre-bid or preconstruction meeting minutes, internal contractor or subcontractor documentation, project correspondence exchanged before the bar chart was prepared, and any other documentation that might shed light on the how the project team approached the planning and scheduling of the project Practical knowledge of the type of project and the physical construction requirements is also necessary to reach a reasonable conclusion regarding the project’s critical path For example, to analyze a bar chart of a high-rise structure, the analyst may need to know that interior finishes usually are not planned to start until the building or a portion of the building is “dried-in” or “watertight,” that a common sequence of the progression of trades is from the bottom up, and that it is common for trades to follow behind one another as the building progresses upward, instead of waiting until the preceding trade has finished all of its work in the tower Given the variations in possible work sequences, analysts should resist the temptation to interpret the bar chart schedule based solely on their own experience Just because a contractor has performed work in a particular sequence in the past does not mean that the contractor on the project being analyzed has planned to perform the work the same way Unless the bar chart is extremely brief, analysts should be able to glean the best indication of the overall plan and sequence of activities to 114 Construction Delays Figure 6.4 Identification of initial critical path activity determine the critical path using the bar chart as the primary indicator of the project team’s plan for execution of the project, rather than analysts proposing their own version of a plan Referring to Fig 6.3, we can define the critical path for the sample bridge project The critical path starts with the mobilization activity, with a duration of weeks This is obvious, since no other activity is scheduled to occur during this period We show this first critical activity in Fig 6.4 Delay Analysis Using Bar Chart Schedules 115 The next two activities on the schedule are the clear and grub activity and the piles at Pier #1 In reviewing the sequence of activities, the clear and grub activity is related to the abutment and approach work The abutment and approach work is scheduled to finish well before the end of the project and does not appear to be related to the schedule of activities for bridge construction The analyst can determine from the contract that the approaches are to be constructed using asphalt paving, but the bridge deck is to be paved with concrete Consequently, there is no physical reason to coordinate the concrete placement for the bridge with the approach construction The only possible relationship might be the need to move the concrete placing equipment onto the bridge superstructure However, because the schedule reflects that the deck work is to start before workers complete either of the approaches, the analyst concludes that the equipment can be moved onto the bridge independently of the approach work Therefore, it appears that the abutment/approach path is not on the critical path for the project Therefore, the critical path must be through the piles and piers When viewing this bar chart, the analyst sees that the work is “stair-stepped” through the specific activities for each pier Thus, after the piles at Pier #1 are completed, the piles at Pier #2 can start While the piles at Pier #2 are being driven, the pile cap at Pier #1 is concurrently constructed Based on the graphic representation, the critical path appears to follow these activities (shown in Fig 6.5): • Piles, Pier #1 • Pile Cap #1 • Pier Column #1 • Pier Cap #1 At this point, the analyst recognizes that the pier columns and the pier caps each have 2-week durations, and the next activity—steel erection— does not begin until all pier caps are completed Therefore, all pier column and pier cap activities are most likely on the critical path, not just the first piles, piers, columns, and caps Using similar reasoning, the steel for Span #1 is critical, and then the path continues through deck placement for all spans Next are the curbs and sidewalks for Spans #3 and #4 and, finally, the punch list work Thus, the overall critical path from the bar chart (Fig 6.6) is: • Mobilization • Piles, Pier #1 • Pile Cap #1 116 Construction Delays Figure 6.5 Identification of initial critical path activities • • • • • • Pier Pier Pier Pier Pier Pier Column #1 Column #2 Cap #1 Column #3 Cap #2 Cap #3 Delay Analysis Using Bar Chart Schedules Figure 6.6 Identification of the critical path • • • • • Steel Span #1 F, R, & P, Span #1 F, R, & P, Span #2 F, R, & P, Span #3 F, R, & P, Span #4 117 118 Construction Delays • • • Curbs & Sidewalks, Span #3 Curbs & Sidewalks, Span #4 Punch list The analyst could reach a similar conclusion working with the less detailed bar chart alone (see Fig 6.1) This would, however, require that the analyst make more assumptions about the work on the separate piers As was noted in the preceding discussion, contemporaneous documentation can help the analyst define the contractor’s planned sequence in more detail The less detailed the bar chart, the more assumptions are required by the analyst to determine the project’s critical path QUANTIFYING DELAYS USING BAR CHART SCHEDULES The process of quantifying delays using a bar chart is similar to the process that is described later in this book when a CPM schedule is available To start the process, the analyst must prepare a detailed as-built diagram that shows as specifically as possible when the project work was actually performed Fig 6.7 is the as-built diagram for the West Street Bridge project Once the as-built has been prepared, the analysis can proceed As the as-built diagram (Fig 6.7) shows, the mobilization activity started on schedule (the first day of Week 1) and finished on schedule (by the end of Week 2) The remaining activities, however, did not proceed in the same manner as the as-planned schedule had predicted As the as-built diagram (Fig 6.7) shows, the pile driving at Piers #1, #2, and #3; the pile caps at Piers #1 and #2; and Pier Column #1 were accomplished as-planned in weeks immediately following the mobilization activity However, the clear and grub activity did not proceed as planned, but started weeks late and finished in the 1-week planned duration If the previous conclusions concerning the critical path were correct, the delay to the start of clearing and grubbing should not have resulted in a delay to the project To check this conclusion, the analyst can “update” the bar chart as of the end of Week 5, as shown in Fig 6.8 As can be seen in Fig 6.8, the project is still on schedule, but the abutment and approach work has been delayed, or “pushed out” in time, because of the delay to the clear and grub activity As expected, there is no delay to the critical path The adjusted schedule (Fig 6.8) shows the as-built condition for the first weeks of the project and the adjusted asplanned activities for the remainder of the work Delay Analysis Using Bar Chart Schedules 119 Figure 6.7 As-built diagram Based on the as-built information, the analyst decides to update the schedule as of the end of Week 11 The as-built diagram (Fig 6.7) shows that the abutment and approach work has not yet begun and that the pier cap work also has not yet begun Pier Columns #1 and #2 were completed on schedule Pier Column #3, however, took week longer to complete than planned The adjusted schedule for Week 11 is shown in Fig 6.9 120 Construction Delays Figure 6.8 Week update, no delay Based on the updated and adjusted schedule presented in Fig 6.9, the analyst concludes that the project is now weeks behind schedule The delay was caused by the late start of Pier Cap #1 work, which was planned to start at the beginning of Week 7, but actually started at the beginning of Week 12 Although Pier Column #3 was late in finishing and Delay Analysis Using Bar Chart Schedules 121 Figure 6.9 Week 11 update, 5-week project delay was on the original critical path, once the Pier Cap #1 activity did not start on time, the critical path shifted solely to the pier cap work Pier Column #3 activity was effectively given float by this shift in the critical path Next, the analyst decides to update the schedule at the end of Week 15 This point is chosen because the activities along the bridge pier and 122 Construction Delays deck path continued in accordance with the adjusted schedule, but the abutment and approach work did not By tracking the two activities that are precedent to punchlist, specifically the curbs and sidewalks of Span #4, which are currently driving the punchlist activity, and the paving of Approach #2, it appears that the critical path shifts in the middle of Week 15 The schedule updated for the end of Week 15 is shown in Fig 6.10 Figure 6.10 Week 15 update, no additional project delay Delay Analysis Using Bar Chart Schedules 123 As shown in Fig 6.10, from the end of Week 11 to the end of Week 15, there was no additional delay, despite the fact that the abutment and approach work continued to be delayed To test the previous observation that the critical path shifts in the middle of Week 15, the analyst updates the schedule at the end of Week 16 The schedule updated for the end of Week 16 is shown in Fig 6.11 As can be determined from Fig 6.11, for the first half of Week 16, the bridge pier and deck path continued to be the driving activity of the punchlist work, while the abutment and approach path continued to consume its last half-week of float Because the pier cap work was progressing as planned, there was no additional delay for the first half of the week Then, the abutment and approach work path became longer than the bridge pier and deck path and, as the longest path, the abutment and approach work became critical Because this path of work continued to be delayed for the remainder of Week 16, by the end of the week, the project had been delayed an additional half-week As a result, by the end of Week 16, the project had been delayed a total of 5.5 weeks Next, the analyst decides to update the schedule at the end of Week 18 This point is chosen because the as-built schedule indicates that the abutment and approach work actually started at this time The schedule updated for the end of Week 18 is shown in Fig 6.12 Because the project had been delayed 5.5 weeks as of the last update, the additional delay since that update is weeks The activities on the bridge pier and deck path were not delayed further since the last update Instead, the additional 2-week delay was the result of the continued lack of progress on the abutment and approach path Next, the analyst decides to update the schedule at the end of Week 31, which is the time that the as-built schedule shows that the project actually completed The schedule updated for the end of Week 31 is shown in Fig 6.13 As shown in Fig 6.13, no additional delay was experienced during the completion of the project At the completion of the analysis, all project delays have been identified As a final check, the analyst ensures that the total net delay identified during the analysis equals the number of days that the project was completed late This example follows the conceptual approach to analyzing delays outlined in Chapter 5, Measuring Delays—The Basics The exact method used to perform an analysis and the accuracy of the results depend on the level of detail of the as-planned schedule and of the available as-built information 124 Construction Delays Figure 6.11 Week 16 update, additional 5-week project delay EXAMPLE DELAY ANALYSIS OF POTENTIAL CHANGES WITH BAR CHARTS To further illustrate the process of determining delays with a bar chart, the following example of the construction of a simple, three-story Delay Analysis Using Bar Chart Schedules 125 Figure 6.12 Week 18 update, additional 2-week project delay building is used Fig 6.14 is a bar chart schedule for the project The critical path is indicated by the red (dark gray in print versions) bars During the project, there were four changes that occurred The analyst has been asked to analyze each of these and determine what delay, if any, each caused to the project completion date To perform the analysis, 126 Construction Delays Figure 6.13 Week 31 update, total project delay of 7.5 weeks the analyst prepared an as-built diagram based on the project daily reports and other contemporaneous information The as-built diagram, with the changed work highlighted in yellow (white in print versions), is shown in Fig 6.15 The analyst, having read this book, understands that the delay cannot be determined simply by comparing the as-planned schedule and Delay Analysis Using Bar Chart Schedules 127 Figure 6.14 Example as-planned schedule with critical path the as-built diagram Instead, to measure the potential delays caused by each change, the analyst must apply the changes as they occur Alternatively, the analyst could be performing the analysis contemporaneously as the project progresses In this case, the as-built diagram would be prepared up to the date of the change and any delays determined at that time Fig 6.16 shows the project through time period 4.5 The actual progress is plotted in green (light gray in print versions), the change in yellow (white in print versions), and the remaining work in red (dark gray in print versions) and blue (black in print versions) bars, similar to the as-planned schedule 128 Construction Delays Figure 6.15 Example as-built diagram with changed work As can be seen from a comparison of the as-planned schedule, Fig 6.14, and the updated schedule with the changed work, Fig 6.16, the project is still scheduled to finish at the end of time period 26 Therefore, no delay was caused by Change #1 The next change to the project occurs during time period The analyst has updated the bar chart through time period 6.5, as shown in Fig 6.17, with the actual progress in green (light gray in print versions), the changed work in yellow (white in print versions), and the future work in red (dark gray in print versions) and blue (black in print versions) bars As can be seen from a comparison of the first update of Delay Analysis Using Bar Chart Schedules 129 Figure 6.16 Time period 4.5 update the schedule, Fig 6.16, and the present update of the schedule, Fig 6.17, the project has been delayed one-half time period and will now finish in the middle of time period 27 It is also noted that Change #2 affected the critical work of the underground utilities As a result of these observations, the analyst can conclude that a delay has occurred because of Change #2 and that the delay is one-half time period in duration The next change to the project, Change #3, occurred during time period 14 The analyst has updated the bar chart through time period 14 to include the changed work This is shown in Fig 6.18, with the actual 130 Construction Delays Figure 6.17 Time period 6.5 update progress in green (light gray in print versions), the changed work in yellow (white in print versions), and the future work in red (dark gray in print versions) and blue (black in print versions) bars As can be seen from a comparison of the preceding update and this update, the end date of the project has not changed; therefore, Change #3 did not affect the critical path, and no project delay resulted The next change, Change #4, occurred during time periods 15 through 17 The analyst has updated the bar chart schedule through time period 17 to include the changed work This is shown in Fig 6.19, with the actual progress in green (light gray in print Delay Analysis Using Bar Chart Schedules 131 Figure 6.18 Time period 14 update versions), the changed work in yellow (white in print versions), and the future work in red (dark gray in print versions) and blue (black in print versions) bars Comparing this update with the preceding update shows that the project end date has moved to a later date The project will now complete at the end of time period 27 and has been delayed an additional one-half time period Note that the critical path has changed Because of the duration of the changed work, a path that previously had float is now the critical path and caused the delay that was measured 132 Construction Delays Figure 6.19 Time period 17 update This simple example demonstrates how a bar chart can be updated contemporaneously to determine the effect of changes while the project progresses or after the project work is complete  ... determining delays with a bar chart, the following example of the construction of a simple, three-story Delay Analysis Using Bar Chart Schedules 125 Figure 6.12 Week 18 update, additional 2-week project... the bar chart, the more assumptions are required by the analyst to determine the project’s critical path QUANTIFYING DELAYS USING BAR CHART SCHEDULES The process of quantifying delays using a bar. .. of the available as-built information 124 Construction Delays Figure 6.11 Week 16 update, additional 5-week project delay EXAMPLE DELAY ANALYSIS OF POTENTIAL CHANGES WITH BAR CHARTS To further