How Structural Engineers Benefit from Constructible Models

Constructible models help engineers identify and avoid obstacles before onsite crews build a project. Find out how using Tekla to enable constructible models can help your structural engineering firm reduce design and review time, contain costs, improve stakeholder collaboration, and produce better-quality structures. 

Constructibility, sometimes called build-ability, is an engineering project management technique. Its principle is to review all construction processes from start to finish during the pre-construction phase.  

Constructibility’s goal is to identify obstacles before a project is actually built. This reduces or prevents errors, delays, and cost overruns.  

Traditionally, engineers produced conceptual models at relatively high levels of development. Designers tended to view details like joints, placements, and connections as “means and methods,” which they would postpone detailing until later in the project lifecycle. 

More Complex Modeling Earlier in the Design Process

However, today’s complex rebar designs and steel connections call for more complex modeling earlier in the design process.

For example, London’s distinctive 225-metre Leadenhall Tower, designed by ARUP using Tekla, involved placing and connecting 9,000 individual steel members. The project scope called for near-fabrication level modeling of all meta-frame nodes and architectural-based connections.

Similarly, Bechtel and CMC designed the liquified natural gas (LNG) tank in Corpus Christi Texas. The facility is a huge, specially designed steel tank with a total storage capacity of roughly 10 million cubic metres of LNG.  

The team took advantage of Tekla’s BIM modeling functionality for rebar estimating, detailing, and coordination. This approach saved time and mitigated risk by planning rebar at the same time the engineers were coordinating with other trades, saving time and identifying and avoiding potential problems. 

Thornton Tomasetti relied on Tekla to deliver the structural engineering of various buildings within the Hudson Yards Development in Manhattan. Their project entailed planning the placement and connection of over 72,000 tons of steel. 

The team reports their work would have been impossible without the level of detail Tekla provided early in the project lifecycle. They concluded that the constructible model approach compressed their work schedule by a minimum of six months. 

Benefits Also Apply to Conventional Projects

On projects like the above, complex geometry generally demands constructible models. However, those benefits also apply to more conventional projects. 

For example, anchor bolt placement can be challenging to plan and coordinate. One crew may be referring to a footing schedule, while another works from a base plate detail drawing. 

This can result in clashes in which a footing’s size or depth doesn’t match the anchor bolt design, meaning the bolt doesn’t fit into its embedment correctly. Similarly, a grade beam section drawing may call for a development length that’s too long for the pad footing. 

Since someone will model these details sooner or later, why not handle them proactively and earlier in the process? Working from a common, constructible model prevents these kinds of common onsite clashes.  

Today’s structural design models often depend on too much guesswork and too many assumptions. This often leads to clashes, requests for information (RFIs), confusion, and delay. 

This miscommunication has adversely affected the engineering profession’s reputation with onsite trades and crews. Now that better tools are available, shouldn’t we hold ourselves to higher standards? 

Evolution of Structural Design

Structural design methods have been evolving over the past fifty years. Engineers have moved from the drawing board to computer assisted design (CAD) to today’s 3D building information models (BIMs). 

However, most stakeholders are still producing and working from 2D drawings to get structures built. We need to ask ourselves what, besides mere habit, is behind the reliance on paper plans. 

Throughout the architecture, engineering, and construction (AEC) project lifecycle, stakeholder teams produce and release a series of independent 2D drawings. The drawback to this process is that, instead of adding information, data gets lost with each drawing iteration. 

On the other hand, when all stakeholders share a common 3D BIM, teams are adding information to a common model, improving consistency, efficiency, and collaboration. That’s why Tekla, BuildingPoint, and many of our customers believe 2D drawings are becoming obsolete. 

Structural Models Save Time and Money

Some of the current hesitation toward working with constructible models like Tekla comes from the tight schedules and budgets under which design teams work. This reluctance doesn’t consider that 3D BIMs actually save time and money, helping teams deliver on time, within budget, and to a higher level of quality. 

Tasks like modeling connections aren’t time consuming when teams take advantage of Tekla’s automated features. For example, connection designs are parametric, so designers can quickly reuse them while the system accommodates different positions and contexts within the structure. 

The 3D BIM can easily generate more accurate 2D drawings at any stage in the process. The difference is that these drawings are also parametric, updating themselves automatically. 

Anytime a stakeholder updates details like connections, all future drawings reflect the new geometry implied by the changes, with all updates tracked. Crews can feel confident they’re working from accurate, up-to-date information. 

Working with a 3D BIM, while generating current 2D drawings and bills of materials for those who need them, turns out to be faster, less costly, and more accurate than traditional methods. That doesn’t necessarily mean engineers no longer need to work with detailers, for example, but it does mean that stakeholder collaboration improves dramatically. 

Seamless Revit Integration and Open Standards 

Tekla Structures seamlessly integrates with Autodesk’s Revit application. Stakeholders can share models back and forth using the Industry Foundation Classes (IFC) open file format standard. 

Trimble also offers an “Export to Revit” software extension at its Tekla Warehouse website. Trimble and BuildingPoint strongly support open BIM standards. 

Working from a genuinely constructible model gives designers confidence that the model will end up working onsite in the real world. It enables coordination based on real-life geometry as well as clash checking at a higher level of detail, earlier in the design process. 

For example, on the Port Canaveral Welcome Centre project, Thornton Tomasetti worked with MEP to resolve model clashes before fabrication. Using an LOD 350 model, the design team detailed all major connections. The crew required only 10 RFIs to complete the work. 

At Quantico Hangar, Thornton Tomasetti’s team used Tekla to model all connections for a massive structure involving 760 tons of steel. The team completed the project with just one RFI. 

FLUOR used Tekla to model another recent structural project and passed the model on to a detailer. The constructible model reduced the time required for the detailing cycle from six weeks to two weeks. 

In their last project, FLUOR simply issued a cover sheet and the Tekla model to the detailer. The team issued only eight RFIs while completing that project. 

Downstream Benefits 

The downstream benefits of working with constructible models include reduced review and design time. The team also produces a better-quality structure upon completion. 

Using a constructible model as a single source of truth improves downstream collaboration, compressing the construction schedule. Detailers can also begin their work earlier and get it done with greater confidence. 

All Stakeholders Benefit from Constructible Models 

In the end, constructible models don’t just benefit structural engineers. They benefit all project stakeholders, improving your team’s reputation and attracting repeat and referral business to your firm. 

Why not contact BuildingPoint today to learn how your firm can start using Tekla to enable constructible models for your structural engineering projects?