Protastructure Crack May 2026
To never see a "crack failure" again, adopt these design rules:
A "crack" often appears as a #NUM! error in your support reactions. This happens when you create a mechanism—a structure that can move infinitely without resistance.
Common Scenario: You model a steel column with a pinned base in X and Y but forget to constrain the Z (vertical) or rotational axis. The solver attempts to compute the stiffness matrix, finds a zero on the diagonal, and crashes.
The Fix: Always run a "Kinematic Check" before the full analysis. Navigate to Analysis > Check Stability. This tool highlights nodes with insufficient restraints. protastructure crack
Crack width is not just a software warning; it is a serviceability limit state (SLS) requirement. Concrete naturally cracks due to tensile stresses, but excessive cracking leads to:
ProtaStructure uses finite element analysis (FEA) to compute stresses in reinforced concrete sections. If your report says "Protastructure crack width exceeds limit," the software is alerting you that your design fails the serviceability check.
When a structural model in Protastructure "cracks" under analysis, it usually means the solver cannot find a stable solution. Here are the top reasons why your Protastructure model is cracking under pressure. To never see a "crack failure" again, adopt
Problem: A 250mm flat slab with 3000mm spans showed crack widths of 0.45 mm (limit 0.3 mm) in ProtaStructure.
Attempted fix 1: Increased rebar from T12@200 to T16@200. Result: Crack width reduced to 0.38 mm – still failing.
Solution: Changed rebar to T12@150 (smaller bars, closer spacing) and increased cover from 25mm to 30mm (to improve bond). New crack width: 0.24 mm – Pass. ProtaStructure uses finite element analysis (FEA) to compute
Lesson: ProtaStructure confirms that bar spacing matters more than total area for crack control.
If the concrete cover entered in ProtaStructure is less than the required durability cover (e.g., XC3, XD1 exposure classes), the software will calculate a tighter crack limit. However, too much cover actually increases crack width (because the crack must extend further). Check your cover value.
ProtaStructure, by default, assumes cracked sections for serviceability. If you accidentally force an uncracked section analysis (e.g., by selecting "ignore tension stiffening"), the software will underestimate deflections but overestimate crack widths. Ensure your analysis settings include tension stiffening.