IN A TECHNOLOGY-DRIVEN CONSTRUCTION landscape, fabricators, contractors, and construction firms need to migrate from 2D CAD paper drawings to software-driven BIM.
The Case for BIM
Structural engineers and pre-casting firms using 2D CAD drawings face many challenges in planning, fabricating, and installing prefabricated members. The inability to visualize prefabrication in the pre-construction stage prompts inaccurate manufacture of prefabricated units. It also causes higher onsite clashes between prefabricated members due to inaccurate shop and installation drawings and other issues.
Non-adherence to fabrication standards leads to rework and low-quality manufacturing. Silos or unconnected workflows cause gaps in communication and collaboration between pre-casting teams and other stakeholders. All these challenges lead to higher material wastage, greater rework, project delays, and cost overages.
From initial design to production, precast concrete detailing supports pre-casters with visualization, simulation, and documentation through graphical representation. All of this is why BIM workflows matter. Here is a more detailed breakdown of the issues:
Smart scheduling and detailing through customization
Accurate precast concrete detailing brings about improved prefabrication of beams, columns, slabs, insulated walls, etc. Realizing what the actual building will look like before construction begins results in efficient planning and implementation. Through BIM, floors can be divided into regions; slabs can be split with layout and spacing; floor segments, including hollow-core, solid, distributed slabs, can be modeled in virtual space. Accurate construction planning for the exact size and weight for casting can be gained through BIM at the initial coordination stage.
Comprehensive IFC integration eliminates boundaries in 3D space to design, develop, quality check, transport, and erect prefabricated modules.
Smart details can be added in Revit models through the rule-based batch insertion of anchors, cuts, plates, etc., for in-depth customization.
Greater dimensional accuracy and precise BOQs
Software-based precast concrete detailing supports the creation of element views and sections through automation to generate dimensions, create accurate BOQs, etc., for quality prefabrication and assembly. Precast concrete detailing for building prefabrication provides stakeholders with accurate time schedules, precise material takeoffs, and reduced errors. This helps to speed up the planning and prefabrication process through precast concrete detailing.
Comprehensive IFC integration eliminates boundaries in 3D space to design, develop, quality check, transport, and erect prefabricated modules. (see: Architosh, “Solibri Inside and Vectorworks—Advancing BIM for Users,” 20 Jul 23)
Reduction in carbon footprint and reduced labor requirements
Precast construction elements are deployed widely to reduce labor requirements and drive higher quality standardization and cost-effectiveness. When precast concrete detailing is used to model prefabricated buildings, it reduces the environmental impact of onsite construction. This is because precast members are manufactured in offsite factories. The data in 3D models is used to identify clashes before actual construction begins.
Also, stakeholders can leverage a single source of truth to generate reports, drawings, fabrication data, etc. Reduced human intervention yields greater data consistency for collaboration between teams engaged in planning, manufacturing, and onsite installation.
Improvements in productivity and workflows
Accurate material export to ERP systems and model tracking of precast objects or products improves external and internal workflows and productivity. In precast concrete detailing, comprehensive information on each prefabricated member is stored in the 3D models. Pre-casters use BIM to generate finalized project drawings for manufacturing units and clients. (see image below).
Precast concrete detailing for prefabrication for design and structural detailing
Companies involved in precast structures, from structural engineers, contractors, and other teams, can leverage precast concrete detailing to generate feasibility studies based on stability, BOQs for concrete, design basis, and more. These feasibility studies drive improved detailing for stability through an extensive range of global standards. Precast concrete detailing for element connections and joint designs can be produced, and structural viability can be ensured with improved cost-effectiveness.
Using 3D models for accurate mold and erection drawings with precast detailing
Accurate mold and erection drawings can be extracted from coordinated and clash-free information-rich 3D BIM models. They promote verification, integration, and operations. Layout drawings, framing plans, elevation drawings, and foundation plans complete with accurate dimensions, component locations, height, and stability calculations are calculated. Floor plans, reinforcement plans, and bar bending schedules can be extracted from an interference-free 3D model.
Production and shop drawings with BBS and precast concrete detailing enhance fabrication
Modeling and detailing precast concrete for prefabrication units brings greater consistency to precast elements. The existence of HVAC drawings and section drawings with equipment layouts promotes higher fabrication accuracy. Elements, including solid walls, sandwich walls, reinforced beams and slabs, hollow core slabs, and stair flights, can be fabricated with coordinated and clash-free shop and production drawings.
Complete and high-quality documentation from 3D IFC BIM models improves the construction
Construction documentation is crucial for the prefabrication and installation of prefabricated members. A comprehensive list of drawings, revision logs, erection materials, erection simulations, and more can support pre-casters and contractors to visualize and resolve onsite challenges. All this is achieved through a single source of truth — a 3D IFC BIM model.
Complex and time-bound construction projects require the capabilities of prefabrication for faster construction, cost reduction, and quality enhancement. The future of precast concrete detailing will involve AR/VR capabilities to view precast 3D models from various angles. Getting pre-casters to communicate and collaborate early in the pre-construction phase will set the pace for effective and efficient fabrication and installation.
All of this only is possible when the entire process is conducted through a full BIM workflow, eliminating the inherent disadvantages associated with non-BIM 2D CAD workflows lacking the capacity for a single source of truth (SSoT) 3D model of the intended structure.
Moreover, automation tools like Dynamo will speed up precast modeling and detailing to produce high-quality prefabrication members, while component customization will ensure a standardized prefabricated product.
Bhushan Avsatthi is a talented architect with over 22 years in the field. He oversees the BIM division of TrueCADD (A subsidiary of HitechDigital Solutions), managing multiple teams of architects, structural and MEP engineers, LEED consultants, and energy modeling experts. He has spoken at various international BIM conferences and is deeply involved in green initiatives. His thoughts on global best practices in building design have been published in multiple architectural and engineering journals.