By Jose Luis Ponz-Tienda, Ph.D.
This project schedule consists of the construction process of the foundations, sub-structure, the super-structure and the facades of a tall building making use of the advanced features that Plexos Project offers as the automatic wizard generator, standard classification systems, federated model, Cype price generator, sub-activities, cycles, and takts.
We wish that this example will be useful for all the Plexos´ fanatics.
A general schema of the project and its WBS under the Uniformat classification system version 1998 is exposed in the following images.
One zip file is provided in this example, containing all the necessary files to follow this article and reproduce the process.
As can be seen, the zip file contains, additional to the Plexos project file [Uniformat Top-Down Tall Building], four IFC files, and three background images.
The IFC files are:
For a proper understanding, this article is organized starting with a description of the construction process, following with the use of the wizard process to build the structure of the project, finishing with the required steps to create the project schedule.
The construction process for the foundations, sub-structure, and super-structure consists of three phases::
In the first phase, the diaphragm walls and piles are drilled, and then, once the first stage of excavations are finished, the beams and floor slabs are cast, repeating the procedure for all the levels of the sub-structure till the desired depth is reached. To retain the diaphragm walls along the construction process could be used steel struts or CIP beams working as an arc, as is used in this example and could be seen in the following video and images of the step-by-step process.
The second phase is started once the first phase is finished, replacing the provisional piles used in the first phase for supporting the beams by columns, closing the internal space created by the CIP beams-in-arc, working from the foundations level to the street level.
The third and final phase is s traditional construction process, in which beams and slabs are supported by CIP columns and walls.
As is exposed previously, the project was organized under the Uniformat standard version 1998 with four BIM models, one for each one of the phases for foundations and structure, and another one for the facades, as was established in the BEP (Building Execution Plan).
Once the models were exported to IFC and located in the CDE (Common Data Environment), they were imported to Plexos Project as follows:
1. Open the Wizard dialog.
2. Select the desired Wizard process
With the [IFC File] choice, Plexos Project analyses the model and lets you select the desired classification system between all the system stored in the model, and builds the structure of the budget/schedule based on the selection.
With the other choices, [System Classification] and [Custom XML], Plexos project builds the structure of the schedule and later lets you import IFC BIM files assigning the activities and creating activities as in step 4.
The classification systems are stored in the [Classification Systems] folder of Plexos project, and the users can create new schemas adapted to its specific needs.
3. Select the desired Classification system
If the selected choice is IFC File, you must to select the desired IFC file, and then the following dialog will appear:
In this case, Plexos Project considers that three classifications systems are compatible, but that doesn't mean that under all the systems the results will be satisfactory because it depends on the level under which the BIM model was created. In this case, we must select the [Uniformat Levels 3-4-5 1998 English].
Note: Plexos Project reads the IfcClassificationReferences IFC field, editable from the "Assembly code" of your BIM software, for the BIM objects classification.
4. Automatically assign BIM objects to activities.
Once the structure of the budget/schedule is built, Plexos Project asks you for the automatic assignment of the BIM objects o the corresponding activities.
5. Automatically assign/create subactivities.
Once the objects have been assigned to the activities, Plexos Project asks you for the automatic creation of subactivities, and in case that some subactivities were created in a previous step, assign the objects to the current subactivities and create new ones in necessary case.
Under this option, Plexos Project scans the levels of IFC model and its correlation with the BIM objects, creating one subactivity for each of the levels found in the activity, producing the result of the following image.
Note that Plexos Project assigns zero units as the quantity for the BIM objects. You can modify this property selecting the desired objects in the IFC grid and, by the contextual menu [Change quantities for the selected objects], modify the property. Plexos Project will analyze the common properties letting you make the proper selection.
It is important to take into account, that Plexos project organizes the subactivities each time that a new model is loaded from its down-to-top levels, so it could be necessary to reorder the subactivities by the [Edit] subactivities option of the properties panel. Because of this, it is recommended to load all the IFC models before to edit/reorder the subactivities and schedule the project.
6. Repeat the process for all the IFC files of the project.
Repeat the process for all the IFC files of the project by clicking over the [Load IFC] of the [BIM workflow] tab in the Ribbon.
Each time that you load a new IFC file, the process restarts at step 4, and the procedure is just the same as previously exposed.
Remember that by default, Plexos Project establishes the IFC models as not [in federation], and [linked] instead of [embedded], for an easy and friendly BIM workflow with the CDE, but this property can be modified in the BIM objects panel by the [Admin] button:
The federation is a model that Plexos Project creates automatically to allow users to view several IFC model simultaneously, letting analyze the project in a holistic way, especially useful for viewing 4D simulation processes.
The federated model, compiles the desired models of the project in just one model through links, without increasing the Plexos project file size.
7. Remove the empty activities.
Now, only remains to remove the unnecessary activities, leaving only 18 activities instead of the 299 necessary activities by applying the traditional scheduling method.
Plexos Project project offers you the possibility of making this process automatically, but remember that only must be done when all the IFCs has been loaded (with the last IFC).
The scheduling process is the same that in the previous examples available in the gallery, with some special characteristics related to loops, due to the special organization of the sub-activities in the standard classification systems. For more information about this issue, please read the Exhibit A.
For an easy and productive scheduling process, it is recommended to follow the following steps:
If each of the steps is completed correctly, to adjust the schedule it will only be necessary to repeat steps 4 and 5 until it meets your requirements.
In our case, following the previously exposed steps:
1. Reorganized and named the activities A1010210 and A1020110.
A1010210. From one activity without sub-activities to 40 sub-activities, each one for a cycle of diaphragm walls execution, considering that one unit is executed in one day.
A1020110. From one activity without sub-activities to 40 sub-activities, each one for a cycle of CIP piles execution, considering three units by day as execution cycle.
2. Reorganized and named the activities B1010310 and B1010410
To solve the problem of Top-to-Down construction process, the first three sub-activities, in activities B1010310 and B1010410, has been reordered from top to down, and additionally, new three sub-activities has been added for the second phase of the construction process.
The only complexity in this step is that some objects assigned by the wizard to the first sub-activities must be reassigned to the new sub-activities.
3. Add costs, the resources and its consumptions to the activities.
4. Adjust the duration of the activities based on the resource availabilities.
This could be one of the most important tools that Plexos Project offer us to develop reliable and efficient schedules.
By clicking [CTRL + R] appears the [Adjust Activity Resources] dialog, to analyze the efficiency of the resources inside the activity, the over-consumption at activity or project level, the required resources for the current duration, and the proposed duration for the current consumptions and availabilities.
5. Add the proper relationships between activities and subactivities.
Now add the proper relationships between the activities and enjoy Plexos Project and its schedules.
García-Nieves, J. D., Ponz-Tienda, J. L., Ospina-Alvarado, A., & Bonilla-Palacios, M. (2019). Multipurpose linear programming optimization model for repetitive activities scheduling in construction projects. Automation in Construction, 105, 102799.
García-Nieves, J. D., Ponz-Tienda, J. L., Salcedo-Bernal, A., & Pellicer, E. (2018). The Multimode Resource-Constrained Project Scheduling Problem for Repetitive Activities in Construction Projects. Computer?Aided Civil and Infrastructure Engineering, 33(8), 655-671.
Ponz-Tienda, J. L., Salcedo-Bernal, A., & Pellicer, E. (2017). A parallel branch and bound algorithm for the resource leveling problem with minimal lags. Computer-Aided Civil and Infrastructure Engineering, 32(6), 474-498.
Ponz-Tienda, J. L., Salcedo-Bernal, A., Pellicer, E., & Benlloch-Marco, J. (2017). The improved adaptive harmony search algorithm for the resource leveling problem with minimal lags. Automation in Construction, 77, 82-92.
Ponz-Tienda, J. L., Pellicer, E., Alarcón, L. F., & Rojas-Quintero, J. S. (2015). Integrating task fragmentation and earned value method into the Last Planner System using spreadsheets. IGLC 23, 63.
Rojas, M. J., Herrera, R. F., Mourgues, C., Ponz-Tienda, J. L., Alarcón, L. F., & Pellicer, E. (2019). BIM Use Assessment (BUA) Tool for Characterizing the Application Levels of BIM Uses for the Planning and Design of Construction Projects. Advances in Civil Engineering, 2019.
For a better comprehension of the concept of continuity and controllable-loops at the activity level, an example of a three floors building structure with columns, beams, and slabs will be exposed.
The best practices for the scheduling of a multistory building in the Lean construction world, or other repetitive projects, is to organize the activities in sets of repetitive sub-activities of cycles or work-taks. With this schema, the work of each sub-activity is repeated in the other sub-activities of the activity, preserving the work-flow. However, standard classification systems organize the projects by concepts, instead of work-flows.
This work organization does not consider how the production flows across the project, and could be considered contrary to the Lean Construction principles, but is how the standard classification system organizes the projects, and we must adapt our principles to this fact.
This example consists of three activities organized by concepts. The first activity for the columns contains three sub-activities, one for each building floor, the second and third activities are Beams and Slabs, with three sub-activities each one as in the columns.
As can be seen, the production flows from one activity to the successor one, but there is a redundant flow inside the activities at the sub-activity level.
This organization, although being contrary to the lean principles, works well until we establish the continuity condition for the involved activities.
Establish the continuity condition to an activity, it is similar to add a new fictitious relationship from the ending sub-activity to the initial one, producing the following effect with an infinite but controllable loop by establishing the involved activities as non-continuous activities:
Plexos Project can detect these cases and will alert you of the possibility of a cycle with the following message:
Do not be afraid of clicking [Yes], if you see some unusual effect, press [Delete] in the relationships panel, and analyze the relationship behavior.