3D PLANNING. Visualization of construction schedules

Transcription

1 3D PLANNING Visualization of construction schedules using 3D models 1

2 TABLE OF CONTENTS s. 3 Introduction s. 3 New knowledge s. 3 Project description s. 3 Project objectives s. 3 Project participants s. 4 Background s. 4 What is 3D planning? s. 5 Applications of 4D models s. 5 Creating the model s. 6 The 3D planning process s. 6 Advantages of 3D planning s. 6 Improved project overview s. 6 Improved communications s. 6 Verification of constructibility s. 7 Barriers to using 3D planning s. 7 Training costs s. 7 Time-related costs s. 7 Financial cost s. 7 Difficult to represent certain tasks s. 8 Conclusions 2

3 Figure: Quay 16 of the Port of Beirut INTRODUCTION New knowledge From the year 2008 to 2010 the Implementation Network will manage the research and development research project New Knowledge for the construction industry. The purpose of the project is to create practical knowledge such as case examples and guidelines on how to work with the principles of Digital Construction. This is done by implementing a number of test projects, where the Digital Construction requirements package is used in practice in different construction projects with help from a task force of experts. The experience from the test projects is transferred to case studies and practical guides that should support the construction industry in adopting digital tools in work. This project is carried out between 1 September 2010 and 16 December 2010 with financial support by the Implementation Network of Digital Construction. The report is written by Hjörtur Sigurðsson, E. Pihl & Søn A.S (referred to as Pihl). For further information, please send inquiries to HSI@pihl-as.dk. Project Objectives The purpose of this project is to improve communication between stakeholders in construction projects regarding the construction schedule by visualizing the construction schedule using a 3D model. To achieve this a set of goals are proposed: Create a 3D model for the project. Create a 4D model (schedule + 3D model). Identify the benefits and drawbacks of 3D planning. Identify suitable software. Going through the process of creating a 3D model and a 4D model will shed light on the requirements for creating a schedule visualization and the processes behind 3D planning. To provide a frame for evaluation whether 3D planning should be implemented in other projects, the advantages and disadvantages of 3D planning will be identified. Since multiple software products exist, one will be selected for further use. It will also be attempted to identify any infrastructure specific aspects of 3D planning. Project Description The construction project that will be visualized in this initiative is an extension of Quay 16 at the Port of Beirut in Lebanon. The project includes a 500 metre long extension of an existing quay and a new container yard of 180,000 square meters. The project has a large earthworks part and a large structural part. The structural part is a 500 m long concrete structure, composed both of in-situ cast objects and precast elements. Project Participants The author wishes to thank everybody involved in this project. Below is a list of the people that have contributed to this project: Hjörtur Sigurðsson, Christian Lundhus Larsson, Peter Mortensen, Michael Schmidt, Bo Fusager, Alexander Poul Andreassen, Rolf Carlsen, Elsebeth Tingleff Larsen, Stefan Gregers Brandt Johansen. 3

4 Figure: Overview of Quay 16 of the Port of Beirut Background Project schedules are typically represented using Gantt charts. In larger projects Gantt charts tend to become long documents that often contain hundreds or thousands of individual activities and cover numerous pages. Gantt charts include little or no reference to the actual physical structure. To evaluate and communicate the time and construction sequences, project participants must mentally associate the schedule information with the description of the physical building. It can therefore be difficult to communicate and evaluate a project schedule both for participants who have a technical background as well as for those who do not. Regardless of the complexity of Gantt charts the schedule has to be communicated to the various project participants. In some cases a filtered version of the Gantt chart that only shows a fraction of the activities of the whole schedule is used so that it is easier to comprehend and in some cases a graphical illustration is prepared to explain certain parts of the project. Having access to a 3D model in a project has a number of advantages. 3D models are excellent for visualizing projects, they allow analyses to be carried out on the model such as collision detection. Exploring the model in 3D makes it easier to discover design errors than in 2D drawings. As a result, 3D models are becoming more and more common, and supplying a 3D model is in many projects a part of the project requirements. As the use of 3D models is spreading, the number of engineers with experience in 3D modelling is growing. Numerous software products now exist for creating visualizations of project schedules using 3D models. Using these it is possible to view and analyse the construction sequence in a different way than has been possible so far. It can be asserted that because 3D models are so much easier to understand, visualizing construction sequences using a 3D model can make it easier to understand and get an overview of schedules. WHAT IS 3D PLANNING? A 3D model may in itself be a useful tool for a construction manager or a planner. Details that are under discussion can be viewed plainly and do not require as much interpretation as when reading 2D drawings. Objects appear similar to what they would in the real world. This is reflected by increased use of 3D models on construction sites to help communicate and understand production drawings. Objects in 3D models can contain additional information. A wall object can for example contain information about its U value, it can contain information about its structural load conditions or information of its location in the construction schedule. This allows the object to function as more than a geometric representation of an object. Depending on the information included in the objects, different types of analyses can be carried out on the object, such as energy calculations, structural calculations or visualization of the construction sequence. When schedule information is added to a 3D model it becomes possible to show the planned status for a given date. A model that contains this sort of information is often called a 4D model 4

5 Figure: The colours of the 3d model indicate different types of tasks. as it has the three space dimensions and contains the additional fourth dimension, time. Further information such as cost and facility management information can be added making the model 5D, 6D nd. In this document the combination of the schedule and the 3D model will be referred to as a 4D model. The process of creating and using a 4D model will be referred to as 3D planning. The basis for a 4D model is a 3D model. 3D models are increasingly becoming available early in the project lifetime, although this is not always the case. In the Beirut project no 3D model was available so it was necessary to create a 3D model based on the existing 2D drawings. After the 3D model was created it was linked with a schedule that was already available. It is important to realize that 3D planning does not replace the scheduling methods of today, but it is rather a supplement to the toolbox available to the planner and construction manager when analyzing and communicating the schedule. Applications of 4d models Once the 4D model has been created it is possible to view the schedule in a live sequence. Objects appear when the tasks they are connected to are commenced and they change colour when the tasks are finished or change status. The 4D model can also be used to show various schedule information such as which contractor carries out a specific task, which work gang carries out a task, make a distinction between different kinds of tasks or how many resources are involved in a task, to name a few. The amount of information that can be visualized depends on how much information is included in the schedule. Some of the most important applications are: Verification of the feasibility of the schedule and construction sequence. A 4D model makes it possible to verify complex sequences visually. Errors in the schedule can be identified visually in a way that is not possible with Gantt charts. The schedule can be analyzed to minimize interference between different trades and work crews. Schedule delay analysis. Tasks affected by an external delay can be highlighted to show the extent of the delay. The 4D model can provide visual support for a time impact analysis. Site logistics and layout can be analyzed. Access routes, material storage and parking areas can be planned using the model. Figure: 4D model is a result of combining a 3D model with a schedule. Creating the 3D model The 3D model was created based on existing 2D drawings. Tekla Structures was used to model the structural part of the model. The earthworks part was modelled with AutoCAD Civil 3D as it makes it possible to present a more realistic representation of the earthworks model objects. The resulting model presents a realistic scenario as different discipline models are often created using different software. The models were then combined using Navisworks Manage. 5

6 Figure: Initially, the schedule visualization will be created by a person with experience in 3D modeling. The planner uses the 4D model to revise his schedule and resubmits the schedule to the 4D model creator who updates the 4D model. The 3D planning process Ideally the planner should be able to create the schedule visualization. Creating the schedule visualization may however require considerable 3D modelling skills which is not always part of the planner skillset. Creating the model can be time consuming and the planner s time may be better used by providing support to a person experienced in 3D modelling. Once the model has been created, no considerable technical skills are required to maintain and update the model. It is recommended that a person with adequate 3D modelling experience creates the model and that the planner takes over the daily maintenance and updating of the model once it has been completed. During the process where the schedule visualization is created the planner and the person that creates the schedule visualizations should cooperate as much as possible. Active communication between the model creator and the planner promotes better understanding of the project and will result in a better 4D model. The person that creates the model could also manage the day-to-day updating of the schedule visualization. He could manage multiple models from off site although this could result in a reduction of the exposure of the schedule visualization within the projects as the people using the schedule visualization will become less involved with the visualization. BENEFITS OF 3D PLANNING Improved project overview One of the largest advantages of 3D planning is the overview it gives the viewer when he navigates through the schedule. Immediately after viewing the sequence the viewer knows roughly what the project is about and in which sequence the main parts of the project are constructed. Specific parts of the project can be examined in order to get a better understanding of the project. The viewer does not have to mentally associate thousands of building parts and hundreds of tasks since the 4D model does that association for the viewer. The 4D model can be used to quickly get new project participants up to speed about what is going on in a project, what has happened in the project to the present day and what will happen in the near future. It is difficult to measure how long it takes to gain an understanding of a project. However, most of the people interviewed during this project agree that it is an efficient way to introduce people to schedules. Improved communications The content of a schedule frequently needs to be communicated. The 4D model can be used to view the schedule instead of using the Gantt chart or as a supplement to it. Many of the planners at Pihl already rely on illustrative methods to communicate the schedule in relation with the physical parts of the project. These methods are however based on 2D drawings and require more interpretation than the 4D model. Using a 4D model to visualize the schedule is quite similar to the methods already in use but more advanced. As mentioned earlier the 4D model gives a representation of the schedule that correlates the parts of the project and the tasks in the schedule. In the project in Beirut the communications have not been evaluated specifically but other studies suggest that using 4D models results in fewer mistakes while requiring less communication. Verification of Constructibility - fewer mistakes The schedule for the quay extension project was analysed using the 4d model. However, no scheduling issues were uncovered. This serves as a verification of the constructability of the project. Literature on 3d planning suggests that some types of scheduling issues can more easily be identified by using a 4D model rather than by using a Gantt chart. Logical errors in the schedule and oversights are more likely to surface if the schedule is analyzed using a 4D model. Logical failures or objects not included in the schedule should be easier to identify when using a 4D model. Objects that have been unintentionally left out of the schedule will not appear when the construction sequence is viewed. Tasks that have spatial constraints; that are constrained by work that is carried out above, below or around the location in which they are carried out, should be more easily analyzed in the 4D model than by viewing a Gantt chart and 2D drawings. Since the 4D model shows the locations in which tasks take place, by viewing the model, the planner can examine the surroundings of the tasks. If the surroundings contain conflicting tasks, the planner can revise his schedule. In effect, analysing the 4D model serves as a verification of the constructability of the project. 6

7 Figure: View from Tekla Structures Figure: View from AutoCAD Civil BARRIERS TO USING 3D PLANNING Based on the discussions that have taken place within Pihl during the execution of this project a number of barriers for using 3D planning have been identified. Training costs One of the obstacles presenting itself when introducing 3D planning is that only few people possess 3D planning experience. Furthermore, few planners and construction managers have experience with 3D modelling. People unfamiliar with the technology must be trained before they can begin creating and maintaining 4D models. Creating a 4D model requires more training than maintaining it. It is suggested that 2-3 months should be adequate for a person to learn how to create a 4D model efficiently. Two to three weeks should suffice for training a person in maintaining the model. As 3D planning becomes more common more and more people will become competent in working with the 3D planning process. No training is required to view and understand the schedule presented. In some cases people may tend to be sceptical towards new technologies and new working methods. It is therefore vital that managers support the use of 3D planning so that the new process is not ignored. Time-related costs Creating the 3D and 4D model requires time. In this project the 3D model was created in about 4 weeks and the 4D model was composed in about 3 weeks. Naturally, establishing a 4D model for the next project will take less time due to the accumulated experience. It is not unreasonable to assume that a 3D model of similar size could be established in 3 weeks and the 4D model in 1 to 2 weeks, given that all information is available at the start of the project. It should be noted that some of the time spent on creating the 4D model could be regained through fewer errors in the schedule and smoother communication on the building site and between stakeholders. In many projects changes to the design and schedule are frequent, especially in the early stages of the project. It still remains to be seen if a 4D model can be updated and maintained fast enough to be useful in practical work. Software cost It seems that using 3D planning can improve project overview, communications and can help verify the constructability of projects but some investment is required. A number of software products were required to carry out this project. Tekla Structures and AutoCAD Civil 3D were required for modeling the project. A 4D modeling software is also required to be connected to the schedule. In total the cost of software for a project is around DKK. This is however dramatically reduced if a 3d model exists for the project since only 4d modeling software is required. Adequate computer hardware is also required for 3d modeling so some hardware costs should be expected. Difficult to represent certain types of tasks Projects normally contain many tasks that do not take place on the construction site and which are not related to any specific object on the construction site. Since the 4D model uses objects that are on the construction site to show the project progress it is not possible to show the progress of tasks that take place elsewhere or that are not related to objects. Often these tasks are related to the procurement and management of the project. This may be a problem as it becomes difficult to show these tasks which are often of importance. 7

8 Overview: 4D models provide a better overview of project schedules. 4D models provide a frame for discussions about the schedule. 4D models can provide verification of constructibility as the model allows detection of certain logical errors in schedules. 4D models can be created in a relatively short timeframe if all information is available. It is suggested that a person experienced with 3D modeling initially create 4D models with input from planner. There are considerable costs involved with implementing 3D planning. Must be evaluated on a case-to-case basis. Figure: The Beirut Quay 16 extension project shown in 11 increments. CONCLUSIONS The project in Beirut was chosen as a test project because of its nature as an infrastructure project. Many of the projects carried out by Pihl are infrastructure projects which is why it has been of special interest to examine the use of 3D planning in such a project. The goals of the project were achieved, a 3D model was created and connected with the schedule for the project. A description of how a 4D model can be created by combining a 3D model and a schedule was made. Some alternative applications of 3D planning were identified and there were speculations in respect of the advantages and disadvantages of using 3D planning. A suitable software candidate was also selected. It has been shown feasible to create a 3D model for a project that has only been designed in 2D and combining the 3D model with a schedule to create a 4D model in a relatively short period of time. The processes and methods for maintaining and updating the 4D model with new drawing and schedule information have been identified. Infrastructure projects pose a challenge in visualizing construction schedules using 3D models compared to building construction projects. In building projects the objects are usually easily separated from each other but in civil works surfaces are not so easily separated. This means that from the outset the earthwork should ideally be modelled in the same fragments that the tasks in the schedule refer to. It is suggested that initially a person that is experienced in working with 3D models should create a 4D model based on input from a planner. Once finished, the model can be analyzed by the planner who can modify the schedule based on the analysis of the 4D model. It is important to realize that 3D planning is not a new scheduling method but rather a new option for presenting and analysing a schedule. Making a schedule visualization will not make a bad schedule good, although it may help shed light on some of the issues of the schedule. Multiple types of analyses can be made on the schedule visualization after it has been created. Areas where limited space may cause a problem can be identified and construction sequences can be verified. Schedule information such as the critical path, resource types and the consequences of a delay can be highlighted using the objects in the model. The schedule was analysed using the 4D model. The constructability of the schedule was verified by the schedule analysis. No errors were identified in the schedule. The 4D model furthermore provides a frame for presenting and discussing the schedule and for the project in general. Implementing 3D planning in new projects requires training of the staff that is supposed to use it. It is suggested that 2-3 months of training is required for a person to be able to create a 4D model and 2-3 weeks for training a person in maintaining a 4D model. The software that was required in this project required an investment of about DKK. In this test project we have focused on taking the first step towards the use of 3D planning, i.e. creating the 4D model and identifying the main advantages and disadvantages of using 4D models. Some questions worth investigating further were raised during the execution of this project. It would be interesting to investigate the use of 4D models with the focus on management of a project. This would shed light on the maintenance and updating processes of the model, which have not been fully covered in this project. Furthermore, it would be interesting to evaluate in more detail the financial cost of using 3D planning in a project so as to identify the types of projects in which 3D planning would be an advantage. 8

9 E. Pihl & Søn A.S. Hovedkontor: E. Pihl & Søn A.S. Nybrovej Kgs. Lyngby tlf: fax: Jylland: E. Pihl & Søn A.S. Skomagervej 3B 7100 Vejle tlf: fax: