3. PROFIS ENGINEERING FUNCTIONALITY

Within the Hilti PROFIS Engineering software concrete fixing module, stand-off functionality (2) can be found in the base plate tab (1), as shown in Fig. 8. When stand-off with grouting is selected (3), the default restraint level is assumed to be 𝛼𝑀 = 2. The user can modify this value (4). By default, Hilti high strength epoxy grout CB-G EG is selected, with a compressive strength of 120N/mm2 (5). The user can also select
any multipurpose grout and enter the desired concrete strength (6).

Figure 8. Clamping, restraint, and grout property options in PROFIS Engineering.
Within the loads tab (1) there are several options for design, and by default the standoff verification is undertaken according to EN 1992-4 ((2), Fig. 8).
To proceed with the SOFA standoff design method, select this from within the standoff section (3).

Figure 9. Choice of design method in PROFIS Engineering.

4. DESIGN EXAMPLE
Problem statement:

1. Verify the steel resistance of the anchors in the grouted stand-off base plate connection below for both EN 1992-4 design and for Hilti SOFA Method design. Assume 𝛼𝑚 = 2.0.
2. Determine the value of the multiplication factor 𝜓𝑏,𝑔 to be applied to the shear concrete breakout failure mode.

Given:
• Hilti HIT-RE 500 V4 adhesive anchor with Grade 8.8 M24 threaded rod
𝑑 = 24 𝑚𝑚
𝐴𝑠 = 352.7 𝑚𝑚2
𝑓𝑢𝑘 = 800 𝑁/𝑚𝑚2
𝛾𝑀𝑠 = 1.5 ETA-20/0541, Table C.1 for normal resistance
𝛾𝑀𝑠 = 1.25 ETA-20/0541, Table C.7 for shear resistance
• Connection properties and dimensions
Grout is non-shrink, flowable, and completely fills the space between the base plate and concrete surface.
𝑓𝑐𝑘 = 40 𝑀𝑃𝑎 Characteristic concrete strength
𝑓𝑔𝑟𝑜𝑢𝑡 = 50 𝑀𝑃𝑎 Characteristic grout strength
𝑡𝑔𝑟𝑜𝑢𝑡 = 44 𝑚𝑚 Grout thickness
𝑒1 = 60 𝑚𝑚 Distance from center of plate to concrete
𝑎3 = 12 𝑚𝑚 Assumed half-diameter spalling depth

Figure 10. Design example parameters.
Initial checks from EN 1992-4, 6.2.2.3 (2):


Calculation of basic threaded rod steel resistances :

EN 1992-4 design for steel resistance:
EN 1992-4 design is invalid in accordance with EN 1992-4, 6.2.2.3 (2) for the following reasons:
• Grout pad thickness 𝑡𝑔𝑟𝑜𝑢𝑡 = 44 𝑚𝑚 exceeds maximum thickness of 40 𝑚𝑚
• Bending moment is present on the connection
Therefore, bolt bending must be calculated in accordance with EN 1992-4, 6.2.2.3 (3).




Hilti SOFA Method design for steel resistance
Tensile forces on anchors
Analysis does not indicate that grout cracking will not occur at ultimate load levels. Therefore, assume that the area outside of the perimeter of the bolt line is not available for force distribution. Distances from anchor centerlines to edge of base plate are greater than the thickness of the grout pad, so 45-degree crushing of edges is assumed not to interfere with base plate behavior.

Calculate the internal lever arm between the tensile steel and the concrete compressive stress block at concrete crushing resistance. Conservatively, omit compressive anchors from section analysis. Using a parabolic compressive reaction for the forces given, an internal lever arm between centroid of Anchors 1 and 2 to centroid of compressive reaction of 𝑧 = 370 𝑚𝑚 is determined.


Summary of tensile design capacities and utilizations for EN 1992-4 and Hilti SOFA*

*Note that the EN 1992-4 calculations in the table above are only used in the calculation of 𝑉𝑅𝑑,𝑠,𝑀 in the shear summary tables below. The SOFA calculations apply to the tensile calculations of an anchor with the assumed load distribution above due to the presence of grout.

Summary of shear design capacities and utilizations for EN 1992-4 and Hilti SOFA

*Reduced grout pad thickness needed to use EN 1992-4 Eq. (7.36)

Summary of interaction design utilisations for EN 1992-4 and Hilti SOFA

*The combined tensile and shear utilisation for EN 1992-4 is incorporated directly into the equation for shear resistance in EN 1992-4 Eq. (7.37). Therefore, the shear utilisations and the combined utilisations are identical.

Calculation of multiplier 𝝍𝒃,𝒈
The multiplier 𝜓𝑏,𝑔 is automatically applied to the shear breakout failure mode in the Hilti SOFA Method design.

The shear breakout resistance will be multiplied by 0.85 in SOFA design.

If you missed part one of this article catch up here.

5. REFERENCES
[1] ACI 318-19 (2019). Building code requirements for structural concrete and commentary .
[2] Adihardjo, R. and Soltis, L. (1979). Combined shear and tension on grouted base details . AISC Engineering Journal, 16(1), 23-26.
[3] EN 1992-4 (2018). Eurocode 2 – Design of concrete structures - Part 4: Design of fastenings for use in concrete .
[4] Fichtner, S. (2011). Investigations on the behavior of group fixtures taking into account the anchor plate thickness and a mortar layer (in German). Ph.D. Dissertation, University of Stuttgart, Stuttgart, DE.
[5] Gomez, I. R., Kanvinde, A. M., and Deierlein, G. G. (2011). Experimental investigation of shear transfer in exposed column base connections . AISC Engineering Journal, 48(4), 245-264.
[6] Gresnigt, N., Romeijn, A., Wald, F., and Steenhuis, M. (2008) Column bases in shear and normal force . HERON, 53(1) 87-108.
[7] McBride, K. (2014). Steel strength of anchor bolts in stand-off base plate connections . Ph.D. Dissertation, University of Florida, Gainesville, FL, USA.
[8] Mullins, D. and Parker, D. (2019). Recommendations for structural grouting. STRUCTURE Magazine online. https://www.structuremag.org/?p=14903
[9] Nakashima, S. (1998). Mechanical characteristics of exposed portions of anchor bolts in steel column bases under combined tension and shear . Journal of Constructional Steel Research, 46(1), 262-263.

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