Expertise · Archetype Group (Thailand)
Peerapat Pinyopojanee is Lead Civil and Structural Engineer at Archetype Group in Thailand. This story is about a large-span roof truss where the code's usual shortcut for unbraced length would have given either a heavy design or an unsafe one, and about the analysis used to avoid both.
In Peerapat Pinyopojanee's own words.
"I believe delivering the right design requires capturing true structural behavior, not just passing a software check."
I cross-verify software defaults with deep analytical research rather than blindly following standard code multipliers. Analytical rigour is my core: I am a fundamentals-driven structural engineer.
On the Custom House Hotel, an adaptive reuse of an 1888 historic building, I was Lead Structural Design Engineer and designed the underpinning and masonry strengthening solution.
When the unbraced length is a guess
In a complex large-span roof structure, determining an accurate unbraced length for the continuous truss chords was highly ambiguous. Traditional code-based assumptions, relying on simple node-to-node distances or empirical effective length factors, would have led to an overly conservative, heavy and uneconomical design, while underestimating it risked unexpected buckling failure.
Finding the real collapse mechanism
Instead of relying on standard code simplifications, I applied a fundamentals-driven analytical approach. First, I performed a linear buckling (eigenvalue) analysis on the global 3D model to capture the true critical buckling mode shapes of the whole truss system.
Next, I superimposed precise geometric imperfections onto the model based on those critical modes. Finally, by evaluating the imperfect model through the upper bound theorem of plastic limit analysis, I was able to determine the actual collapse mechanism and the ultimate limit load of the structure.
This bypassed the guesswork of defining unbraced lengths altogether. It allowed me to optimise the truss chord design significantly while proving its structural integrity mathematically, raising both the safety and the cost-efficiency of the project.
Q. What makes MIDAS dependable for critical work?
The constant evolution of the software. Knowing that the MIDAS team is always rolling out updates and proactively resolving bugs makes it a highly reliable tool for critical projects.
Where a code factor would have settled the unbraced length by assumption, Peerapat Pinyopojanee let the buckling modes of the actual truss decide. When the shortcut in your own codes feels uncertain, what would it take to find the real mechanism instead?