LOWER DEFLECTION CRITERION AND PLASTIC DESIGN MAKES HILTI’S MT SYSTEM MORE EFFICIENT

In today’s construction landscape, the demand for cost-effective yet high-performing solutions has never been higher. Value Engineering plays a critical role in meeting these expectations—by optimizing designs without compromising safety, functionality, or code compliance. At Hilti, our commitment to enable better value engineering drives us to continuously push the limits of technical innovation and economic efficiency, always grounded in our unwavering philosophy of safety.

Two key levers in this pursuit are lower deflection criteria and the use of plastic capacity in design. By allowing for reduced deflection limits and harnessing the full plastic capacity of our MT system, engineers can create slimmer, more material-efficient designs—while still meeting the required performance standards. These focus areas are not just technical adjustments—they are strategic enablers that make our MT system more competitive and sustainable.

Every structural element bends under load, and it is essential to ensure that substructures such as those used in MEP applications continue to meet their functional requirements. While this may not involve the risk of collapse or compromise the overall strength of the substructure, it can significantly impact usability and the perceived safety of the people relying on it. This is why, for MEP substructures as well as primary structural elements, Serviceability Limit States (SLS) are just as important as Ultimate Limit States (ULS). ULS focuses on safety and structural stability under extreme load conditions, whereas SLS ensures proper functionality and comfort during everyday use. In MEP systems, excessive deflection can cause practical issues such as leakage or damage to equipment and may also undermine users’ confidence in the system.

Enter PROFIS MSE, your intelligent design partner for MEP supports from Hilti. Our software includes built-in deflection checks, aligning with industry standards. Until recently, the default displacement criteria settings in Hilti PROFIS MSE were based on primary structure recommendations, L/200 for single span and L/150 for cantilevers. However, MEP substructures are not primary structures and therefore allow for more efficient designs, as they do not require such strict deflection limits.

Recognizing the lack of specific deflection criteria for MEP substructures, Hilti turned to comparable applications, like profiled metal decking under EN 1090, to establish more appropriate limits, as such:

- L/150 for single spans

- L/75 for cantilevers

In fact, this change allows you to obtain higher load capacities by default, giving you more design flexibility and efficiency. And if your project demands stricter limits? No problem. With the Hilti PROFIS MSE design software you can customize the deflection settings to meet your specification requirements.

Bending capacity of all channels and girders is currently calculated in Hilti PROFIS MSE based on the elastic section modulus. Several FEA research studies and tests proved that plastic section modulus can be utilized for bending stress calculation.

For selected Hilti channels and girders, we’ve enhanced our approach by incorporating the plastic section modulus, delivering more accurate and efficient bending stress calculations in line with Eurocode 3.

In this way, we can help to offer smarter designs and optimized solutions by leveraging the capabilities of Hilti PROFIS MSE.

Value Engineering is about making intelligent design decisions that improve performance without inflating cost—and that’s exactly what Hilti’s latest developments in the Hilti MT System deliver. By introducing more suitable deflection criteria for MEP substructures, we recognize the unique demands of secondary systems. Unlike primary structures, these supports don’t require overly strict limits. Allowing for slightly higher deflections—L/150 for single spans and L/75 for cantilevers—reflects realistic usage, helps to improve efficiency, and enables higher default capacities in Hilti PROFIS MSE without sacrificing safety or functionality.

Complementing this, the adoption of plastic section modulus in the design of select Hilti MT channels and girders, supported by both testing and Eurocode guidance, allows for fuller utilization of material capacity. This shift from elastic to plastic design principles increases load-bearing potential while maintaining compliance with structural codes.

Together, these two enhancements—smarter deflection checks and plastic design capability—give engineers more flexibility, confidence, and efficiency in their daily work. Hilti’s PROFIS MSE is not just a design tool—it’s your partner in building smarter, safer, and more optimized MEP support systems.