This article is the summary version of a whitepaper developed by Hilti comparing two alternative solutions for fastening elements to steel: studs and beam clamps (see Figure 1). These solutions are viable alternatives to traditional methods, like welding and bolting. The comparison was done for studs and beam clamps solutions on Hilti’s portfolio only and covers a technical analysis and also a study regarding the total cost of the installation (including tools and labour cost). The full version of the whitepaper can be accessed here.





Figure 1 - Some of the solutions compared: S-BT HL (left), MQT-21-41 R (center) and MAB (right). The comparison done and the results shown include other solutions (for more information please see the full version of the whitepaper).

Technical Comparison

In this chapter we compare both technologies from a technical perspective, including base material, load capacities, corrosive environments, approvals, vibration, fatigue, seismic and fire resistance.

When it comes to base material requirements, studs offer overall broader compatibility, including painted steel (without the need for rework), passive fire protected steel, do not require access to both sides of the base material and can be applied on steel profiles without a flange (which are needed to fix beam clamps). Beam clamps, however, can be a good solution if the fixing is not perpendicular to the base material and when bigger diameters (like M16) are needed.

For resistant loads, the performance of both technologies in shear can be similar, but beam clamps offer a higher resistance for tension loads. Despite that, it’s important to note that some reduction factors might apply to the resistant loads of beam clamps, namely to avoid coating damage (reduction factor up to 50% [1] driven by friction on painted steel surface) and due to the loose of pre-tension over time.

With regards to corrosion, beam clamps are typically used in lower corrosion environments (up to C4) [2], whereas studs can be applied in more aggressive environments (up to C5 or even CX). Studs also offer longer life expectancy in these settings, with certain types providing up to 40 years of corrosion resistance. Studs have also an overall wider range of approvals. Beam clamps, while more limited in their certifications, do have approvals that could be relevant for sprinkler applications (like the FM approval) [3] or automotive industries (like PWIS / LABS confirmation) [4].

In applications subject to vibration, studs have demonstrated a robust performance in tests developed by Hilti, in which no loosening or rotation of the nut/screw was observed. For beam clamps, an Engineering Judgement (EJ) should be performed by Hilti for applications in vibration environments. For fatigue loading, studs should be evaluated through an EJ while beam clamps are not recommended.

Studs were also tested for seismic applications, showing robust performance and allowing seismic design. For beam clamps, Hilti provides a seismic approved bracing solution for sprinkler applications, with the MQS-IB.

Lastly, Hilti studs were tested to fire resistance and on fire rated boundaries, with promising results, further detailed on the whitepaper.

Total Installed Cost Analysis

Besides the technical comparison between the two technologies, Hilti has also done an analysis regarding the total installed cost, i.e. considering the total costs of the application (considering studs/beam clamps cost, cost of the tools needed and labour cost).

Once again, it’s important to refer that this analysis only compares solutions in Hilti’s portfolio. For the labour cost as well as products (further referred as hardware), average values for the German market were assumed. For the tools, a cost per fixing point was estimated based on the lifetime of the tool. To quantify the time needed for the installation, a user was trained in Hilti’s Headquarters and performed four different configurations: (i) headrail application, (ii) trapeze on rod, (iii) heavy trapeze and (iv) cantilever – see Figure 2.



Figure 2 - Different configurations considered: headrail (top left), trapeze on rod (top right), heavy trapeze (bottom left) and cantilever (bottom right).

Hilti’s beam clamps shown to be the most economical solution for the trapeze on rod application. As for the headrail and cantilever applications, studs are the ones providing the best economical solutions. When it comes to the heavy trapeze application, the cost of both technologies is balanced. In Figure 3 it’s possible to see the results for the different applications, with the costs splitted per nature (tool, hardware and labour) – these results apply to the referred assumptions, meaning that different market conditions will lead to different results.

Summary

The purpose of this document is to help the reader on selecting the best technology for fastening elements to steel, between studs and beam clamps. The choice depends on different factors, namely technical (base material, loads, corrosion, approvals…) and cost considerations. Studs are generally the more versatile option, especially for challenging environments and paited steel. Beam clamps, however, offer advantages in some applications, namely on trapeze on rod and non-perpendicular configurations.

References

[1] CEN (European Committee for Standardization), “NP-EN 1993-1-8:2005 Eurocode 3: Design of Steel Structures – Part 1-8: Design of joints,” 2005.
[2] ISO (International Organization for Standardization), “ISO 12944-9:2018 Paints and varnishes – Corrosion protection of steel structures by protective paint systems – Part 9: Protective paint systems and laboratory performance test methods for offshore and related structures,” 2018.
[3] FM Global, "About us," Retrieved from FM Global Website, [Accessed: Jul. 8, 2024].
[4] VDMA (Verband Deutscher Maschinen – und Anlagenbau – German Mechanical Engineering Industry Association), "VDMA 24364 – 2018-05 Hydraulic Fluid Power – Fluids – Method for coding the level of contamination by solid particles," 2018.