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Operating LOD400-based Daily Bill of Materials through the Plan-Do-Check-Act Cycle

Project Team

Martin Fischer, Min Song
 

Overview

Our study on 831 daily work orders collected from five construction sites showed that generating a daily BOM consisting of engineered-to-order (ETO) materials can be done quickly (e.g., 1 minute/daily BOM) by leveraging information resources at a site, whereas generating a daily BOM consisting of made-to-stock (MTS) materials can be time consuming (e.g., 12-68 mintues/daily BOM) (Song et al. 2017). To address this problem for daily BOMs consisting of MTS materials, we proposed in our last year's seed research (2017-18 seed research) (1) a prototype for foremen’s use that operates with level of development (LOD) 400 elements and a smallest workface boundary (SWFB), and (2) iterative improvement of the prototype with the goal of expediting the speed of generating a daily BOM consisting of MTS materials. This 2017-18 seed research, in the context of the plan-do-check-act (PDCA) cycle, fit into the stage of the planning where foremen prepared daily BOMs planned using the prototype. As a continuation of this research, we plan to improve the prototype and ask foremen to take the daily BOMs generated in the planning stage, operate them throughout the remaining stages of the PDCA cycle, and produce controls metrics that can be analyzed on a daily level and on LOD400. This research will take the form of iterative field experiments with the goal of improving the prototype and finding a methodology for quickly operating daily BOMs through the PDCA cycle and thereby generating controls metrics.
 

Project Background

          Research Motivation

By using the prototype delivered through the 2017-18 seed research, prototype v3, foremen were able to generate a daily BOM in 59 seconds on average. The information items available from these daily BOMs are the quantities of materials planned, date, relationship to LOD400 elements, and the number of workers assigned to fabricate the materials planned. These planned BOMs, if further utilized and operated throughout the PDCA cycle, can be used to formulate additional controls metrics that can be analyzed on a daily level as well as on LOD400. The controls metrics that can be formulated by going through the PDCA cycle include LOD400-based PPC (when the daily BOM planned is compared with the daily BOM completed) and production rate (when the daily BOM is tied with the manpower information of the day).
 

          Industry Example

Based on our sample tests done over the course of site visits for this research, the time it takes foremen to generate a daily BOM by using pre-existing information at a site (i.e., without using the prototype) ranged from 12 minutes to 68 minutes as shown in Figure 1. This deterred the foremen from preparing precise daily scopes of work and BOMs in the planning stage, let alone operating the daily BOMs through the remaining stages of the PDCA cycle. To address this problem and expedite the generation of the BOMs, we first built a prototype that functions with LOD400 and SWFB. And by carrying out three field experiments in UAE, Sweden, and Peru, and we were able to iteratively improve the prototype and reduce the time to generate a daily BOM down to 59 seconds per daily BOM on average. This outcome also motivated us to look at the potentials of taking the daily BOM planned and operating it throughout the remaining stages of the PDCA cycle and producing controls metrics that are enabled by going through the PDCA cycle.
 
 

Field Experiment 1

Field experiment 1 is in progress as of March 2019 on a research building project in California. The project is in the structural phase and the trades selected for the experiment are the plumbing and mechanical trades. The LOD400 objects relevant to this stage of the construction are slab inserts, i.e., the inserts that are installed before pouring the slab concrete, such as hanger anchors and sleeves (see Figure 2).
 
 
For this project, prototype v4 was developed which allows a user to create a completed version of a daily BOM (as opposed to a planned version) during the Check stage of the PDCA cycle. In the completed version of a daily BOM, the foreman can indicate the actual manpower used for the day as well. Prototype v4 also has a database that keeps a record of the planned and completed versions of daily BOMs with their corresponding LOD400 objects and number of workers. This database then supports a LOD400-based metrics dashboard, which allows a user to drill down to the daily level and check the quantities of LOD400 objects planned/installed and monitor the daily trend of performance metrics (e.g., PPC, productivity) as shown in Figure 3.
 
 

A set of methods that can be used with prototype v4 were also formulated based on the feedback from the foremen and the lessons learned throughout the field experiment (see Figure 4). These methods can be divided into monthly, weekly, and daily methods.

          Monthly

Import LOD400 objects to the prototype piecemeal:
The VDC engineer (i.e., the person in charge or setting up the prototype) imports the scope of LOD400 objects to be constructed in the next month to the prototype on a monthly basis. Shop (fabrication) details typically get approved two to four weeks before fabrication, which also means that LOD400 is typically not fully fixed, issued and approved until about a month before construction, so the VDC engineer should append the new scope to be constructed on a monthly basis.

          Weekly

Pre-plan next week's daily BOMs before weekly coordination meeting using LOD400 and SWFB:
Pre-planning is planning done by each trade individually. Checking the readiness of planned work is the responsibility of each trade. Pre-planning can be done on any day of the week but should be completed before a weekly subcontractor coordination meeting, where only conflicts between trades are checked. The pre-planning helps making the subcontractor coordination meeting shorter.

Crosscheck pre-planning and commit during a contractors coordination meeting:
Project teams meet once a week for crosschecking next week's plan that has been proposed (i.e., pre-planned). Participants are GC planner, GC general foreman (or site manager), VDC engineer, trades foremen. GC planner should check for any conflicts between trades and check the proposed planning against the milestones in the project's mid-term or long-term schedule. The planned quantities of materials for the next week can be provided to the supplier or warehouse at this stage.

          Daily

Update daily BOM:
Updating a daily BOM is done by each trade individually everyday. If needed, the foreman can use SWFBs to modify the scope of work planned to match the scope of work completed. The number of actual workers at the site on the day should be updated as well. When PPC/productivity dips below the running average, the foreman should also record the reason for the underperformance.

 

 
 
In addition to the research progress above, we are also in the process of collecting metrics that could hopefully show that operating LOD400-based daily BOMs through the PDCA cycle is feasible for a foreman in terms of speed and usability. The result of this from the current and next field experiments will be prepared and shared with the CIFE members by September 2019.
 
 

References

Song, M. H., Fischer, M., and Theis, P. (2017). “Field study on the connection between BIM and daily work orders.” J. Constr. Engrg. Mgmt
 

Original Research Proposal

Funding Year: 
2019
Stakeholder Categories: 
Builders