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In this blog, we will explain how to utilize LOD to manage the BIM modeling process. LOD refers to the terms “Level of Detail” and “Level of Development.” When you describe “to detail the model”, it means practically “to add more detail elements on the elements each model has” in modeling procedure. This is the concept of “Level of Detail”. On the other hand, “Level of Development” is the concept that whether the shape of the model or the added information is reliable enough and indicate the progress of modeling.

Since the latter is necessary for the communication between the parties who share the model, identifying the “Level of Development” of each element (=LOD Specification) is positioned as the expression method necessary for information sharing, and Smart BIM Standard uses LOD specifications (LODs).

In the document released from BIM Forum organized by the American Institute of Architects (AIA), LODs is described as “facilitates the resolution of communication conflicts and the detailed definition of BIM milestones and deliverables.” In addition, the LODs Guide published by BIM Forum describes several important features of LODs. The following is an excerpt.

・LODs does not represent only the design phase, because the progress of elements varies according to the projects and the phases, and LOD is used in a mixed manner.
・As described above, LOD is used in a mixed manner, so LODs does not represent the entire model, such as the “LOD 300 model,” which represents the completion level based on the phase.
・The purpose of LODs is to share the required progress level and identify that the downstream process is reliable information, and it does not represent a timely requirement.
・Supplement to the BIM execution plan, not a substitute

The objective is to correctly understand the progress of the model at each stage of the work process. The original “LODs” defines the requirements for five of the six levels of LODs. For example, referring to the summary of LOD 200 and 300, LOD 200 defines “all information must be viewed as approximate” and LOD 300 defines “all can be measured directly from the model.” Basically, the settings are LOD 200, where all the data shapes are “decent,” and LOD 300, where all the data shapes are correct, including height.

As a practical matter, it seems to be very difficult to create a model with LOD 300 in the design phase. In other words, if it is true to the original theory, the differences between levels are large, and it is difficult to match the conventional workflows with phase management.
To solve this problem, Smart BIM Standard adds its own levels. For example, between LOD 200 and 300, LOD 250 is added for the requirement that “the plan information and properties are accurate”, and LOD 325 is added for the requirement that “the detail plan information is correct at the production drawing level. By adding these levels, we can set achievable target levels matching our conventional workflows. And the original “LODs” provide specific examples of requirements for each element. For example, in the case of wooden partition walls, LOD 200 requires the classification of objects, and LOD 300 requires a model capable of wall substrates planning.
When modeling based on these requirements, we need to think about “what to do when replacing them with Revit operations”. However, because LODs is not defined for Revit users only, the requirements do not match Revit operations.

If it is up to each modeler to determine what needs to be input, then the modeling result could be totally different according to the modelers. To avoid this situation, the LOD requirement must be converted to a Revit operation. As an example, let’s consider the wooden partition wall case shown above with LOD 200 requirements. Then we can break it down into instance location, instance type selection, and properties. In this way, the requirements in the original definition can be aligned with Revit operations, resulting in production LOD requirements.

Smart BIM Standard creates LOD management sheets that replace LOD level requirements with Revit modeling operations for each category unit. Since LODs are for the purpose of common recognition of model progress, the LOD requirements are not changed in text, and special notes are included in the remarks section or in the BIM execution plan.

As described above, if there is a LOD requirement that is redefined in an operational form, it becomes possible to establish a “target LOD” for each phase, and it becomes clear what needs to be done in modeling for this target. This saves the modeling instructors from having to worry about how far to input and reduces the amount of effort required to instruct. It also gives the modelers clarity about what to do, so they don’t get lost in modeling. This also limits what needs to be checked out of the vast amount of information the model has, so there will be no unnecessary checking. The biggest benefit of this is the increased accuracy of the model in each phase, and the ability to select reliable information.

It is very important to control what information should be input in which phase and to what extent in order to prevent all the modeling rework.

We have pointed out three difficulties in BIM : “there is no know-how in managing the BIM modeling process,” “we need to balance out between information and drawing representations using BIM software.” and “there is no systematic method to create BIM with the building information.” These are two solutions we found to these challenges. Since there is not one solid solution to each difficulty, so what we found is the methods to solve three problems in a combined manner.

● Hierarchical methods for sorting information
● LOD (Level of Development) management methods to manage the process (Level of Development)

Smart BIM Standard is a standard that is aware of the above solutions. The rules for the consistent use of BIM are not simply determined by considering ease of input and intelligibility. On “What’s SBS?” web site, “Modeling rules are required to coordinate/manage the types of data that BIM brings.” From this point of view, modeling rules should ideally be “easy to apply,” “easy to verify,” and “easy to update” in order to operate smoothly. We considered the conditions for this to be “easy for anyone to understand and remember” and “easy to obtain computer support.” As a way of fulfilling these conditions, we found that the solution is to be “hierarchized to sort information” and “utilizing LOD that can be described by data.”

As is known, in Obayashi corporation we use Autodesk Revit as a standard software. Revit has each user interface for architectural design, structural design, and MEP design so that we can create a single model for coordination among architectural information, structural information, and MEP information. This is one of the major reasons for us to have selected Revit as a standard software and also its ability to store information hierarchically is also one of the great features of Revit.

However, Revit may be said to be a difficult application to learn. There might be many areas where it is difficult to put into practice just by understanding the concept. However, this SBS release site is uploading the contents that incorporate the knowledge gained by us Obayashi corporation, and we hope our site contents will help many Revit users.

In the next blog, we will explain LOD utilization with Smart BIM Standard.

What information do we want to extract from BIM?
To put it in an extreme way, this answer will be nothing but a quantity. People might say that the consensus building and the crash detections with 3D view are also the purposes of using BIM. As a matter of course, three-dimensional drawing information is also one of the important information, but the consensus building and the crash detections are also means for producing confirmed information. What we want to achieve is “getting the confirmed information” of the results agreed upon by the concerned parties in the model.

For the usage of this “confirmed information”, there are cases where three-dimensional model information is required, but here we consider it as a one-dimensional “quantity”. From BIM, we can obtain the information such as cubic meters of concrete, square meters of gypsum boards, number of single-swing doors. We can obtain thousands of types of component data from a fully equipped BIM. We can obtain the “volume” from all model elements, the “area” from all surface elements, and the “number” from all components. However, in many cases, creating just a model does not achieve the goal. This is because thousands of numerical data input have no value unless they have the specific meaning in each.

Numerical data will have a value as an information only when it is combined with “what is” information. In the example above, the “subject” is necessary such as “cubic meters of concrete is,” “square meters of gypsum board is,” and “number of single-swing doors is”. Then how can you decide this “subject”? Is the “subject” “cubic meters of concrete” sufficiently representing a set of the meanings? Is it necessary to define with subdividing the concrete into “concrete of Fc21” and “concrete of Fc24” considering the designed strength? Or is it necessary to define with subdividing the concrete mix detail in consideration of the time when placing an order for the concrete mixture plant? The answer is “indefinite”. All the detail definitions might be necessary, but none might be necessary. The answer depends all on the project organizational form, the objectives of BIM in the project, and the phase of the project, etc.

Unfortunately, there is no systematic method to create this “what is” information.
The fact that there is no method for this creating data is the third aspect of the difficulty of BIM

There seem to be often the cases that although people start adopting BIM as means of achieving a certain goal, people end up in just creating BIM models as if it was a goal unintentionally. If we find BIM difficult, we need to re-consider what we are trying to solve by applying BIM.

One of the common complaints among BIM users is about drawing functions of BIM software, such as “drawing functions are weak compared to CAD” and ” it takes much larger efforts to generate drawings that can be created with CAD “.

CAD is the specialized software for creating two-dimensional drawings. On the other hand, BIM software is mainly used to create 3D models and integrate all building information, but it can also generate 2D drawings from 3D models as a part of its functionality.

It is natural that the drawing functions of BIM software are inferior to CAD in terms of whether it is easy to handle drawing representations such as adding information to the drawings by inputting text, line drawings and omitting detail descriptions with indications in the special specification.

This is because the “purpose” of each software is different. Since BIM software is not specifically designed for creating 2-D drawings, it is very clear that drawings by BIM software looks somewhat poor compared to drawings by CAD.

Nevertheless, even with these conditions what are the objectives of using BIM?

Many BIM users seem to be encouraged by the motivation that they want to use the available information in BIM after creating their models. The conventional construction process requires repeated transcribing and re-drawing in all the information transmissions.

This process not only causes huge waste of time, but also risks transmission and description errors. For example, there are a lots of drawings with inconsistencies due to different design disciplines, detailed shopdrawing and construction plan drawings generated based on mismatching design drawings such as plan, section, elevation drawings and sectional details etc.. BIM users seem to believe that BIM has some potentials to solve this critical issue in the process flow.

If this is your motivation to start using BIM software, you should be able to understand that a drawing (2D view) is just one aspect to confirm the accuracy of the modeling input, to diagram and convey the information the BIM model has.

In other words, the drawing should not have been the purpose. The purpose is to make it possible to utilize the information that BIM model has and to extract the useful information when needed. Focusing too much on how to create a BIM model to generate drawings exactly like CAD software can result in BIM models that are biased and contain only limited information.

As explained above, if you prioritize the generation of 2D drawings with BIM software, the possibility of successfully operating BIM will be is greatly reduced. However, at the same time drawings are a very good means of communicating information.

Therefore, BIM will not work well if the information by the drawings is not taken into account for sure.

The second critical difficulty with BIM is the need to balance out between information and drawing representations using BIM software.

Next blog will be about “How to define information” as the third topic from “Identification of BIM difficulties”. We will talk about what “information” of BIM is really needed, and how much subdivision is required to define information to obtain the confirmed information.

For this time, we will dig out the nature of the difficulties of BIM in three perspectives: “process control,” “intention of use,” and “definition of information.” The first is about the “process control”.

“The technology of use (使う技術)” of BIM data is a main subject of media in these days. From robotics, on-site management to data base construction for ongoing maintenance of a project using cloud system, numerous applications are now possible. But what about the “the technique of make (つくる技術)” of the BIM data? Unfortunately, “the technique of make” is not as pleasing as “the technology of use”. The modeling rules or templates that are slowly and steadily accumulated, the modeling methodology, and the organizational operations can be said the main techniques of creating the BIM data. But, there is no certain solution in the preparation of the BIM data, and it is those individual organizations or companies in the closed environment in which they need to devise the techniques by themselves, resulting in hard to achieve social contribution.

The greater the objective of the BIM is means the greater the impact of BIM modelling it implies. It is essential to have skilled technicians for model making that requires much workloads, and managing such works requires much skilled managers, and by all, much sophisticated discipline in all aspects of modeling is to be followed. This process control of BIM modelling will eventually involves many other technical solutions.

However, very little amount of information about this is available. Since the process control and its project is confidential, there is almost no information shared among companies but each organization is conducting their own methodology.

It is necessary to assign new rules on those items that has never had the concept of data, and to emphasize the importance of sharing information between different fields at an earlier stage. Yet, it seems that there are some people who think it is too difficult to remove the past convention and even refuse to change from the existing way.

There is a huge obstacle in having a shortage of information when trying to achieve “the technique of make” of the BIM data, so-called the “process control”. Lack of information lets the companies in a naive environment where a repetitive failure will be inevitable to be able to reach the certain level of technology and settling down. Moreover, as the failure is not allowed in each project, BIM is rejected even before experiencing the failure. There is no chance to benefit the advantage of BIM but to fail to accumulate the expertise leaving them to fall behind, and this will probably continue to happen over again.

The first point of the difficulties of BIM is the absence of knowledge of process control.

For the next, we will explain about the “intention of use” as the second point of the difficulties of BIM. There are two different approaches to BIM application, one is viewing BIM as a tool, and the other one is BIM as an intention. We will investigate in the intention of BIM use in detail again.

In the Architectural BIM Promotion conference held by the Ministry of Land, Infrastructure, Transport, it was agreed that the current status of BIM use is limited to “Individually use in each design and construction phase, and cross-phase use (in other words, “Integrated use throughout design to construction phase”) has not been performed very much (1).”
The greatest significance of promoting BIM use of the cross-phase type is that “by making appropriate use of the handed-over BIM in-between the respective phases, information-input and processing operations that were duplicated in each phase will be omitted (2).”

To create a BIM model for a single building, it takes a lot of time and money, so it is uneconomical to create a model both in the design and construction phases. Nevertheless, we believe that the purpose of the integrated use in design and construction phases is not just to reduce the amount of input work that had previously been duplicated.

Since BIM can represent three-dimensional shapes, this aspect was mostly noticed when it was introduced in the beginning. Then, it started to be used to present the buildings to the clients or to study very complicated shape of the structures, because BIM, compared with two-dimensional floor plans, sections or elevations which can provide people the only limited view of the building, makes it possible for people to get the view from any angle they want and to get the idea of the whole building easily. However, BIM use for such visualization purposes alone does not produce the biggest effect for improving productivity in building production work.

In order to make BIM a key to productivity improvement, it is essential to make the best use of the information that BIM modeling has. These days still in the most building projects, all the necessary information on-site are documented separately, all the design and spec information are written in design drawing documents, all the quantity information are written in estimation summary documents and all the cost information are written in project budget documents. By using BIM, any of these information can be extracted from BIM as consistent information. For example, the area of a fire compartment on a given floor can be instantly tabulated by specification from BIM.
What is important in this case is whether the extracted information is correct or reliable. This requires a BIM that correctly reflects all the design-information. Needless to say, there is no guarantee that everything is correct and finalized in the design phase, so we need to examine it later in the detail design phase and raise the degree of completion. However, if the model reflects all the information and is updated in the design phase, it will be very valuable to use it further.
It is also important to share not only BIM models but also project-specific BIM requirements and how detail BIM was developed at that point among involved parties in the appropriate timeline. All those correct and proper information transmissions will increase the value of BIM use in the projects.

We believe that the reliability and the smooth transmission of design information is the purpose of the integrated BIM use.

Next, we will talk about “process-control” in the title of “Identification of difficulties in BIM.” This is the first series of three. We will dig a bit deeper into the reasons why it is difficult to promote BIM.

※1 “Guidelines for Standardized Workflow of BIM in the Architectural Field and Its Utilization Measures”
(1st and 2nd editions) [Summary] p.1

※2 “Guidelines for Standardized Workflow of BIM in the Architectural Field and Its Utilization Measures”
(1st Edition) p.7 and (2nd Edition) p.12

(Reference) Architectural BIM Promotion Council-Architectural BIM Promotion Council-Ministry of Land, Infrastructure, Transport and Tourism (mlit.go.jp)