BUILDING INFORMATION MODELS
Building Information Models or BIMs need to be considered of as the building industry’s program of Product Information Modeling ideas in which the item is a building. Earlier implementations of BIM happen to be very “geometry centric”, however this is starting to broaden now to addition of properties for use in analysis software such as energy use simulation, quantity takeoff, cost estimating, construction planning and numerous forms of engineering analysis. Just like Product Models, a BIM could be considered of as a data bank of the building project. The information in this repository will sooner or later span the complete collection of data we now handle for building projects, yet as an integrated data set. Therefore, BIMs are multi-representational, multi-dimensional, and integrate the information developed by several business domains.
BIM Models include many forms of item. The most generally recognized are object symbolizing the real elements of the building.
• Wall
• Door
• Window
• Column
• Beam; and
• Floor slab.
But BIM models additionally consist of numerous other object types which define abstract principles and relationships like: relationships (connection and adjacency), object type definition (wall type and door type), hierarchies (containment), and grouping (zones and systems).
2D geometry
2D Plan drawings are produced as geometric views or information of the “plan” shape illustrations of the objects in the model. It is essential to observe that the “plan” rendering uses industry standard symbolic graphics (e.g. door swing) while the “3D” representation uses 3D physical geometry.
3D geometry
3D views are produced as geometric views of the “3D” shape illustration.
Properties
Properties are connected to BIM objects to determine or describe them in some approach. The range of alternatives for these properties is as broad as all the situations in which they will be regarded as in a project, from layout through construction and operation. Usually this kind of properties are primarily defined in a BIM authoring programs and can then be utilized by analysis and simulation applications to evaluate design efficiency.
Relationships
Record and administration of relationships is a crucial spot in which BIMs enhance upon procedures and software tools utilized in the history because they allow a higher level of model evaluation than attributes only.
Example includes all of the following relationships
Visible
1. Connection;
2. Voids (an opening in the wall); and
3. Supports.
Not Visible
1. Bounds (walls, floor bound space);
2. Contains (bldg. elements and space); and
3. Connects (space to door, window, and adjacent spaces).
BIM Execution Plan
The purpose of the BIM Execution Plan is to present a structure that will let all the parties involved use and take benefit of BIM technology, along with best practices and methods arranged with the client BIM Guidelines, to guarantee the project is complete on time and with minimum design and or coordination issues.
The BIM Execution Plan (BEP) is a comprehensive plan that defines how the project will be implemented, monitored and controlled with regard to BIM. It is necessary that a BEP be created to provide a master information and data management plan and assignment of role and responsibilities for model creation and data integration at project initiation. The Plan shall incorporate requirements specified for a project and will be created through a collaborative approach concerning all stakeholders .The BEP will outline the project purchase strategy and will align to suit the needs of clients Integrated Delivery Strategy . Factors of the BEP shall focus on Team Skills, Industry Capability, and improvements in technology. By means of this collaborative process the team shall agree on how, when, why, and to what Level of Development (LOD) BIM shall be used in assistance of project outcomes and objectives. Based upon on the procurement strategy, multiple BEP’s may be needed. For ex-ample, in the case of Design-Bid-Build, one shall be provided during design and one during construction. For an Integrated Project, one BEP may be sufficient for the entire duration of the project.
BIM and Integrated project delivery
I heard it said once that if you design through consensus, you start out to design a horse and end up with a camel. But working in a collaborative does not mean you have to operate without a vision. What it means is that input comes from the whole design team early on and is tested in the model, evaluated and then retooled if necessary, following a process of nonlinear thinking I like to refer to as a design loop, or “spiral”, whereas the project moves forward, issues that were addressed early on are revisited over and over again, refined each time from a higher plane of knowledge. BIM enables this process. Collaboration in a BIM -enabled integrated process is aimed at producing a better product, generally meaning of higher quality, in less time, consuming less resources and more sustainable than a project developed in a traditional process. The BIM process lets the entire project team share in the knowledge, risk and reward. Centers of higher education in the AEC have to recreate this collaborative experience in the academic world, not only within the school, but extending to other institutions around the world to reflect the presence of global economy and to cultivate human relationship globally. This new work environment free of time zones, regional and national boundaries, yet constrained by cultural differences, must be grappled with and understood by the design professionals of tomorrow.
Green design with regard to sustainability has grown to be a hot subject of the day. All-around the planet, community, public-private, private and advocacy groups have recognized a wide variety of objectives, specifications, courses and standards for green advancement (such as LEED, USGBC, Water Sense, Energy Star, Green Seal, Green-e, Green Globes, etc.).
Building Information Modeling (or BIM) is an crucial ally in the seek for durability. BIM is a technique of utilizing digital technology to set up a constant and built-in information flow regarding all factors of a model, advancement and/or construction project from beginning to conclusion. Generally including all the participants in a undertaking — owners, developers, financiers, architects, engineers, contractors, consultants, end users, regulators — BIM tracks, assembles, coordinates, evaluates and records all essential project info to supply more useful, expected and productive projects. BIM can supply a constant comments loop allowing greater project improvement and optimization.
BIM can work together a extensive range of variables. It can be focused to evaluate schedule, cost, alternatives, team responsibilities and interfaces. It can easily deal with such site and environmental concerns as layout, orientation, solar exposure, shading, grading, drainage, day lighting, airflow, climate exposure, and landscaping. It can cope with the architectural and engineering components of building massing, form, structure, materials, building systems (HVAC, plumbing, electrical, fire), assemblies, detailing, interiors, equipment, fixtures and furnishings. And it can address the human issues of building function and use, amenities, safety, ergonomics, indoor air quality, convenience and comfort. By offering total project information, more precisely and more rapidly, to more project team users, in a range of manipulable platforms, BIM encourages better judgment-making all over the project.
A simultaneous method to BIM, as well as one which is frequently used in combination with BIM, is Integrated Project Delivery (or IPD). IPD basically links owners, designers and contractors at an early stage of a project to ensure the mutuality of goals and objectives, and the steady and timely giving of information for improved decision-making. IPD is, in effect, a form of functioning relationship, whilst BIM is a data-manipulation tool that can assist that functioning relationship.
Bim standardization and interpolability
Standardization is a rational step in the advancement and usage of new technologies and procedures as it can and should permit a next level of performance and usage to sector. Standardization for BIM realistically adopted the route used for standardization of Product Information Models in STEP. The following initiated in 1994, when a then recently established AEC team at Autodesk started advancement of a common library of building model components as the foundation for interoperability between AEC add-ons to AutoCAD. Achievement in the preliminary prototyping ultimately guided to the creation of the Industry Alliance for Interoperability (IAI), which incorporated 12 industry major companies, brought by Autodesk, that developed the original Industry Foundation Classes (IFC). IFC was launched as the “common vocabulary for interoperability in the building industry” at the 1995 AEC Systems seminar in Atlanta. All 12 companies exhibited prototype programs that interoperated on a shared building model. Finding the industry enthusiasm earned by the first launch of IFC, the IAI member companies made the conclusion to open its membership to all companies in the building sector. By the end of 1995, there were a number of international chapters and hundreds of member companies in the called International Alliance for Interoperability (IAI). Several “Domain Teams” were also established, to define the end user functions to be served by a first public release of IFC specifications for a standardized BIM. Design and development of IFC by this greater, more international alliance was very much inspired by STEP and actually, IFC makes use of numerous elements of the STEP standard, such as: the EXPRESS modeling language, the STEP physical file format, and schemas for geometry and topology.
BIM Model Based Estimating
Quantities produced from a Building Information Model supply the standard data necessary to generate correct estimates. Structuring this data effectively is the next step, but when carried out and linked to the model, estimates can be created rapidly and modified as the design model changes.
This article gives a high level summary of the approach of model based estimating and illustrates the key advantages of implementing this strategy.
The practice
1. An accurate BOQ.
2. A clear system for the construction method, creating a sequence of work, structured to enable the allocation of quantities to those work. This is commonly known as a Work Breakdown Structure (WBS) or Standard Method of Measurement (SMM).
3. Estimating tools that can perform precise calculations based on the derived BOQ and WBS, reporting the resulting estimates in common or client defined formats.
Creating an Accurate BOQ
This step is crucial in any estimating practice. The BOQ is extracted from the project design blueprints, but conventional methods for take-off from these 2D designs, are vulnerable to miscalculation for the following causes:
1. The project drawings themselves are often erroneous.
2. The design is depicted by many drawings (plans and elevations) escalating the possibility of incomplete or double counting specific components of the design.
3. It is a gradual process and on a sizeable project, it is likely that layouts will have modified during any one take-off exercise, meaning that the BOQ is often out of date.
If the undertaking utilizes BIM process and technology the chance of all of these errors is lessened because:
1. The Building Information Model is an accurate representation of design.
2. The project is represented by a single model rather than numerous drawings.
3. The model has in-built intelligence and knows what each building element is, what it is made of and how much there is of it. In other words, the model can automatically and instantly create a BOQ.
4. As design changes are made in the model, the BOQ is automatically updated and therefore is always current.
Nevertheless, to obtain a meaningful BOQ, the model has to be produced in such a approach as to deliver a BOQ that is put together to construction methodology. It is not sufficient to just to count up the building elements, because in fact the construction method group’s activities together and the model must comprehend this. It is consequently required to have a system in place to specify the design practices for the model such a system is typically described as a Work Breakdown Structure.
Why adopt Model Based Estimating as the desired process?
In its own right, Model Based Estimating, as explained above, gives estimates that are more precise than those from conventional processes and it offers them more rapidly. The pace with which estimates can be created greatly helps the decision making process allowing what if situations to be run at all key stages of the project.
In addition, being a highly visual process, it enhances the possibilities of effective bidding and improves conversation throughout design and construction. The reason to follow Model Based Estimating is apparent, but it is only one of the benefits that BIM brings to the whole project lifecycle. Integrating Model Based Estimating is simple as it is structured on the BIM process – thus allowing broader BIM benefits to be noticed.
BIM Based Area Calculations
Area calculation is rightly considered by clients as a critical design output, informing decision- making from feasibility phase through to facilities management. Traditional processes are subject to human error both in spatial definition in the CAD environmental and in transferring that information to external spreadsheets. BIM affords a controlled process for spatial definition (as areas or volumes, and by preset definitions) and a reliable mechanism for outputting this data for direct usage in the project environment.
Owners should demand that space calculations on their projects be based on smart BIM space objects. Older methods based on hand drawn polygons are typically inaccurate and can lead to significant error. In this computer age, we should not accept practices that naturally involve errors and approximation.” BIM has brought the computer age to construction. The previous generation architectural CAD systems were able to compute the area of a polygon, even with columns and other interior occlusions. However, they were not able to represent building space explicitly as parametric objects. Space objects were approximated as user-defined polygons with an associated space name as attribute. The schedule of net space areas could be calculated from the named polygons and used in checking layouts in comparison to the project space program. Like other aspects of computer drafting, this did the calculations, but left to the operators all questions of accuracy and correctness.
This method was the best achievable in drafting systems, where all so-called “building components” were collections of graphic entities interpreted by the beholder. However, this computer representation of spaces carried with it all the baggage of traditional drafting systems:
1. Consistency of the design was the responsibility of the user; if a wall was moved, the effect on spaces on both sides of the wall were the responsibility of the draftsman. Inconsistency between wall layouts and space were highly likely in large projects with many spaces, such as hospitals. Consistency management is hard. A space polygon may be drawn to the wrong side of a wall or overlap with other spaces and these are hard to see by visual inspection.
2. Spatial definitions and standards may not always be followed when done manually, leading to further variation. Are columns and freestanding walls included or not?
3. Space boundaries were usually approximate. Unless the space polygon was carefully snapped to the proper vertices defining the corners of the polygon, the space polygon was only a visual approximation of the actual net space.
The process for area scheduling in the BIM environment is controlled and customizable. In the BIM environment spaces exist as unique entities. They are defined by dynamic association to building elements – floors, walls, ceilings. This means, on the one hand, that as these elements are modified in the model the area calculations are updated, and on the other hand, that if the spatial definition needs to be changed (eg Gross floor area is to be calculated by center line of a wall, rather than outer face) the spatial entities can be redefined. BIM spaces can more accurately represent complex spaces than traditional methods – particularly irregular and curvilinear volumes. Most significantly these spaces have direct links to schedules that update automatically as the design parameter change. The schedule data can be exported out of the model environment for broader usage across the project – linking directly into and cost estimation or facilities management software. The value of BIM space entities is being continuously redefined and expanded. In some cases bi- directional associations have been developed where, in a concept phase, the designer can make changes in the schedule that directly impact the building volume in the model. In other cases designers develop algorithms reflecting predefined design requirements (for example the relationship of circulation space to retail space) and allow these algorithms to generate preliminary massing objects. Downstream, space elements can contain huge amounts of design data – finishes schedules, FF&E inventories or HVAC design requirements. These parameters are not merely records of the design intent but form mechanisms for verifying and driving the development of the model.
Clash Detection
Navisworks software provides a Clash Detection module that checks your BIM and shows you any areas where items interfere, or “clash”, with each other. This BIM tool will allow you to set up the rules and options for your clash tests, view the results, sort them, and produce a report as a text file or in HTML or XML formats.
Managing a series of clash tests can get very complicated, especially if you have a set of different layers you want to clash detect separately. Clash Detection in Navisworks is designed to help you control these clash tests and maintain an audit trail of clashes throughout the life of the project.
Setting up and running a clash test requires the following steps:
1. Select Groups and create folders for each group. The Select tab of the Clash Detective control bar allows you to refine your clash test by only testing sets of items at a time, rather than the whole model against itself. This will produce faster and more sensible results. For example Mechanical Ducts with Fire Sprinkler Lines.
2. Set the rules for the test.
3. Select the required items to be included in the test and set the test type options.
4. View the Results.
5. Produce a clash report.
6. Managing/Status clash tests for future use. Navisworks will update this status automatically, informing the current state of the clashes in the model.
Advantage of Using Navisworks for Clash Detection:
1. Revit vs. Navisworks: Revit has its own clash detection process. Revit clash detection identifies the places where clashes occur. It does not create reports and does not have any tools to manage the clash detection process as design progresses. Navisworks provides greater flexibility for controlling the clash detection parameters and will identify clashes, generate reports which can help the design team to resolve the clashes, and track resolution with an automatic audit trail.
2. Managing the BIM Clash Detection Process: Managing clash tests for a big project can get complicated. One simple but timesaving way Navisworks does this is by remembering the names of clashes throughout the project’s life so you don’t have to go through each clash every time you run a test to figure out whether it’s a new clash or one you have already seen. Clash Detective also allows you to assign a status to a clash and can update this status automatically, informing you of the current state of the clashes in the model.
4D Construction Phasing
Construction planning is an continuous work to control the advance of a construction project and react as necessary- dynamically modifying the “situation on the ground.” Of course, a building’s design is at the center of its project plan, and by including schedule data to a 3D building information model (i.e., the building design) you can produce a 4D building information model, where time is the 4th dimension.
4D models consist of planning data such as the start and end date of a element and their criticality or slack. As a result, a 4D building information model offers an user-friendly interface for project team and other stakeholders to easily imagine the assembling of a building over time. It enables 4D construction simulation, a key planning tool during preconstruction to evaluate various options. 4D storyboards and animations make BIM a highly effective communication tool – giving architects, builders, and their clients a shared knowledge of project status, milestones, responsibilities, and construction plans.
Teams generally start out building 4D models by manually mapping the schedule dates from the project plan to the model parts. That effort helps them improve the plan and improve how they communicate the plan to the whole team. Later, as they advance their skills, they programmatically link the schedule to the model, to save time and increase their ability to evaluate various construction sequence options.
There are two representative approaches for linking a building information model to a project plan. First one is a direct link between Revit and Microsoft Project (MS Project). The second method is a tool from Innovaya that exports a Revit building information model and displays it in a specialized 3D/4D visualization environment linked to a project plan from either MS project or primavera technology.
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