Software Used for Prefabrication and DfMA Design

The construction industry in the last decade has started to innovate to improve efficiency, increase profits and achieve time frame certainty.  The increasing appearance of prefabricated components in construction is one such facet of innovation, and prefabrication services are becoming increasingly sought after for projects across the US, UK, Canada and Australia. The assembly of several components of a structure in a factory location and transporting those assemblies to the on-site location, or prefabricated construction, also known as modular construction or Design for Manufacture and Assembly (DfMA), has been considered an effective way to reduce costs, contribute towards timely project completion and also reduce health and safety incidents.

The prefabricated construction of components permits engineering and other work to continue more rapidly and with less resources on site because the site is starting to look more of a location for assembly, using elements that are pre-fabricated. Prefabricated components are designed using a selection of software that specifically enables the creation of MEP (M&E) prefabrication modules and plant skids as well as structural and architecturally designed buildings and building components. We look at some of the different types of prefabrication in construction and the software that enables it, in conjunction with BIM (Building Information Modelling) technology.

Prefabricated construction services or Design for Manufacture and Assembly (DfMA) or modular construction services as they are known, are generally perceived to apply to complete units for standard use. But modular construction involves more than that. It involves a broad range of sub-assemblies and prefabricated elements, such as fire stairs, elevators, plumbing, heating and cooling and ADA-compliant spaces, which can be manufactured off site and transported to the worksite. More complex elements of a building, such as a façade with panels, can be prefabricated. Even subcomponents which are repeated throughout a project, such as patient rooms in medical facilities, bathrooms, classrooms and science labs in educational institutions, lend themselves to the process of prefabrication. The diverse range of prefabricated components can be broadly classified into 3 types: structural, architectural and engineering-related.  Each of these DfMA elements are explored in more detail in this article.

Structural Prefabrication:

The options for DfMA are almost endless within the structural design space. Tall tower blocks or large halls, where even load-bearing walls, as well, as retaining walls of L shape, are components of a structure that can be prefabricated. Load-bearing walls are generally external walls of a building and can even be walls between apartments, which bolster the structure’s rigidity and these can now be manufactured off site and delivered to site. Cast in moulds for prefabrication are waffle units, placed in grid patterns, which are used for flooring/roofing. Other elements routinely prefabricated, either as whole units or several component pieces for assembly on site, include:

- Columns that carry beams and floor loadings to the foundation and beams
- Beams (simple ones over single openings or more complex ones seen in frames)
- Girders
- Concrete haunches (connects columns to beams)
- Stairs made from concrete
- Concrete wall panels
- Hollow core slabs
- Floor slabs
- Concrete racks
- Terrace blocks
- Channels
- Joists
- Steel frames

For structures that use steel frames, it is possible to fabricate multiple stories without pillars, beams and concrete. These steel frames are designed and manufactured from computer models directly linked to CNC (computer numerical control) machines, ensuring high levels of accuracy and speed of erection.

Suitable for residential structures, prefabricated box element technology involves a procedure where a structure is assembled with ready-to-assemble box units off site. Such box elements generally include a load-bearing frame, walls, floors and a roof, with windows, HVAC and electrical equipment and fittings.

Architectural Prefabrication:

Of course, many of the structural elements built are also considered to be architectural elements and the detail that is created for the same includes the architectural design and building code requirements for off-site manufacture. Prefabrication components generally used in architecture include:

- Building envelope and cladding
- Stairs
- Internal load bearing walls, lighter partitions
- Open, closed panel systems
- Bathroom, kitchen pods, with electrical and plumbing systems
- Wall elements
- Roof elements
- Ceiling elements
- Windows, doors, ventilators
- Plaster board assemblies
- Timber frame wall elements
- Panels made of wood, cement, gypsum and other materials for floors
- Acoustic panels

Engineering Prefabrication:

Prefabricated, reinforced and pre-stressed elements of advanced technological and sophisticated design are used in the engineering elements of projects too. Prefabricated components utilised in engineering involve several individual elements, such as the assemblies of:

• Uni-strut corridor modules containing HVAC, pipework, electrical tray/ladder/basket, sprinkler and drainage

• Uni-strut riser modules containing building services from plant areas to floors

• Plant skids containing mechanical plant for plant rooms and energy centres

A modular process skid, or plant skid, is a system within a frame that is easily transported. Individual skids contain process systems, and multiple process skids can be assembled to create entire portable plants, sometimes referred to as ‘a system in a box’. Multi-skid process systems may consist of coordinated raw materials skids, utilities skids and processing units. Multiple skids enable parallel construction.  

A plant room, mechanical room or a boiler room, is a room or area in a structure that is dedicated to mechanical equipment and associated electrical equipment, all of which can be prefabricated. The plant room usually contains the following:

• Air handlers
• Boilers
• Chillers
• Heat exchangers
• Water heaters and tanks
• Water pumps (for domestic, heating/cooling, and firefighting water)
• Main distribution piping and valves
• Sprinkler distribution piping and pumps
• Back-up electrical generators
• Elevator machinery
• HVAC (heating, ventilation and air-conditioning) equipment

Modular ceiling and riser systems consist of building components to store, process and plan. These systems make it faster and easier to assemble the building services solution on site.

Prefabricated components are useful as plant skids, in plant rooms and as ceiling and riser modules because they have already considered all hanging and attachments to a module and therefore hangars and fitting individual services on site are not required.  Typically, these modules are created during the 3D BIM coordination phase, where earlier planning will allow a more effective layout.

Software:

Prefabrication for architecture, structure and MEP (M&E) services is used for an efficient and effective prefabrication process. Some of the more popular software solutions used include:

AutoCAD, Revit, Inventor, FabricationMEP
The preferred software for prefabrication in construction are Revit, AutoCAD and Inventor. They deliver:

- Detailed 3D models, as well as accurate modules and spool drawings for use in risers, corridors and plant rooms for faster building services installation.

- Precise 3D models and associated drawings for pre-engineered steel structures.

- Comprehensive 3D models and detailed manufacturing drawings for specific areas, such as hotel bathroom pods or hospital bathroom pods, exterior panel walls, multi-trade racks, patient room headwalls, for reduced costs and faster installation

During construction, SDS/2, IDAT Precast and Autodesk Fabrication are relevant software options that support the generation of precise structural and MEP 3D models for prefabrication. Additionally, Autodesk’s Revit software works efficiently with the manufacturing features of Autodesk Inventor to deliver prefabrication modules.

The prefabrication model by Inventor communicates any changes with the architectural design and the Computer Numerical Control (CNC) components. For each type of prefabrication module, a single Revit group will define the discipline part. All discipline models must have elements so that modules are geometrically separated. This file can be used as a complete module for prefabrication. For every type of prefabrication module in a project, there exists one unique module model. Any module group/assembly can be updated, altered, replaced or deleted, while each deviation is audited, accepted or denied.
 
At this point, a BIM workflow for the drawing and analysis of prefabricated modules can be produced in Revit. It can then monitor alterations. With a record of the modules’ prefabrication parameters, data can be counted, analysed and translated. With the parameter values, filters and module-specific views can be created, facilitating coordination between the different project teams.

In AutoCAD, a schematic drawing of a prefabricated element type and dimension values of the concerned section are displayed. It can then generate 3D drawings of defined elements and element parameters are specified.

Autodesk’s Fabrication CADmep™, Fabrication ESTmep™ and Fabrication CAMduct™ software help detail and fabricate better buildings. BIM 360 Team, Revit, and Fabrication tools can communicate, view, mark up and review project design files from anywhere, and stay connected to the extended design team.

SEMA:

With sophisticated data and macro technologies, SEMA software can be adapted to the specific needs of a company. SEMA supports prefabricated construction with simple operations to place elements in roofs, ceilings or walls in a fast and efficient way.

SEMA features extensive editing functions and constant 3D image updates to double-check the construction. Layouts and drawings with customer inputs are quickly created. Flexible macros are provided, specifically for stairs.

SEMA also provides 3D visualisation from multiple angles. The ‘surroundings’ of objects, such as walls, windows, ceilings or furniture, can be viewed with photorealistic presentations, and a variety of useful 3D objects for visualisation are available. In addition, 3D objects can be imported. Light and shadow measurements contribute to the visual reality of the objects.

The dimensions of an object in its unfinished state can be used to calculate figures, in just a few minutes, for quotations in construction. Detailed assembly points, such as reference points for fixing bracket systems, can be calculated to the millimetre. SEMA offers extensive libraries of fasteners, brackets, end types, tenons, scarf joints, lamellar connectors, dowels and steel connections with bolts.

Solidworks:

Easy to use, easily adaptable for emerging components which can be challenging to create, including curved stairs, Solidworks, part of Dassault Systèmes, is effective for designing high-end components. It increases productivity, with various data and technical communication input and offers simulation technology to help verify designs. Solidworks automates the ordering, configuring, designing and producing of prefabricated parts. It features Solid Modelling, Motion, Simulation, Toolbox, TolAnalyst, Circute Works, PhotoView 360, ScanTo3D, e-drawings and DWG editor. Solidworks developed other software products to support 3D CAD, simulation, product data management, technical communication, electrical design and 3Dexperince. Even the cost of a new product can be estimated using the integrated automated manufacturing cost tools, saving time and increasing productivity of designers and engineers.

CATIA:

CATIA, with the DELMIA application, shows clients how the building’s components will be assembled. With a 3D model, though all parts are represented, the complexity of construction may not be evident. DELMIA details the sequence and process of construction, piece by piece and step by step.

To summarise and conclude, the increasing usage of BIM (building information modelling) technology in the construction industry supports the success of modular construction. A BIM environment encourages a collaborative process, integrating the disciplines of architecture, engineering and construction. BIM links time and 3D data seamlessly, resulting in accurate predictions of schedules involving factory production to on-site assembly, thus supporting prefabrication. Automation equipment practically eliminates the shop drawing phase and several manufacturers can manufacture modules for on-site assembly. Models are extremely detailed and integrated with other facets of production. Clashes are detected during design, resulting in significant savings in both time and expense. Its design stage and coordination stage integration of all aspects makes prefabricated construction possible. Some of the key modules of construction services, such as the plant room, water pipes, bathrooms, etc., can be fabricated off site as part of the BIM process. This saves time, since much of the important testing, such as pressure tests and air tightness tests, are completed in the factory.

This series of testing for each product means that the resulting quality is near ideal and clashes and other issues are identified before the product reaches the site. Heating and cooling loads, HVAC duct sizing and pipe sizing can be calculated. Also, since modules and components are produced in the factory, the volume of the workforce on site is reduced to a great extent. Additionally, BIM allows building services analyses and helps calculate an informed estimate of how the building will function after construction. Having a model means that energy-saving technologies can be incorporated into the design early in the process. The model will also inform clients on their proposed expenses.

Even with a choice of convenient software options easily available, some firms prefer to develop their own fabrication software, because of labour shortages, decreased margins, tighter schedules, poor quality control implementation, the result of inclement weather, complex components and safety issues. For many construction companies, though, the way forward for prefabrication processes remains using the selection of efficient software currently available or finding a partner with the expertise and experience to do so.