Analysis of High-Strength Steel Profile and End-Plate Connections with Steel Joints Add-On for RFEM

Analytical Model

This study adopts the design criteria specified in EN 1993-1-8 for evaluating bolt resistance (shear and tension) and plate resistance (bearing and punching shear), utilizing the limit state formulations provided in Table 3.4.

The design resistance of the equivalent T-stub is evaluated independently for the endplate and the column flange components. For each component, the governing design resistance, F_T,Rd is defined as the minimum value derived from three potential failure mechanisms.

The individual resistance for each mode is calculated based on the plastic moment capacity of the flange (M_pl,1,Rd and M_pl,2,Rd) and the tension resistance of the bolt group(∑F_t,Rd). These modes account for complete flange yielding (Mode 1), bolt failure coupled with flange yielding (Mode 2), and pure bolt fracture (Mode 3).

Failure Modes:

Plastic Resistance Moments:

Fig. 1. Failure Modes of T-Stub

Geometric details of beam to column connection

In line with standard construction practice, all beam and column members were fabricated from S355, Q690, and Q960 steel, whereas the endplates used the higher-strength Q690 and Q960 grades. The geometric configurations, including the endplate and bolt-group arrangements, are shown in Figure 2 & 3, and the corresponding experimental test matrix.

Specimen JD1 (S355) used an HEM 300 column section. To assess the performance of a weak-column/strong-beam hierarchy, a uniform HEA 320 beam section together with 10 mm thick S690 endplates was retained. JD2 was fabricated from Q690 steel and JD3 from Q960 steel. The beam and column sections were H300×180×10×12 and H340×200×10×12 for JD2, and H250×180×10×12 and H300×200×10×12 for JD3. M24 grade 8.8 and M27 grade 10.9 bolts were used.

Fig. 2. Endplate/Bolt Configuration of JD1

Fig. 3. Endplate/Bolt Configuration JD2 & JD3

Discussion

Steel Joints for RFEM Solution

This study presents an experimental and numerical investigation into the structural performance of three extended high-strength steel end-plate beam-to-column connections.

The experimental program was augmented by targeted T-stub characterization and high-fidelity finite element (FE) analysis. The connection design was fully integrated into the primary structural model using the FE-based Steel Joints add-on for RFEM 6. After validation against the experimental data and verification within the Eurocode 3 (EC3) framework, the FE models were employed to extract granular insight into localized deformation mechanics. Figs. 4 and 5 and Tables 1 and 2 present the comparison of moment resistance and stiffness across the experimental results, the Steel Joints module in RFEM, and EC3, while Table 3 summarizes the observed failure modes.

Fig. 4. Comparison of Moment Resistance – Experimental, Steel Joints in RFEM and EC-3

Fig. 5. Comparison of Stiffness – Experimental, Steel Joints in RFEM and EC-3

Fig. 6. Equivalent Stresses and Plastic Strain of JD1 Model

Fig. 7. Equivalent Stresses and Plastic Strain of JD2 Model

Fig. 8. Equivalent Stresses and Plastic Strain of JD3 Model

Fig. 9. Design Ratio and Rotational Stiffness of JD1 Model

Fig. 10. Design Ratio and Rotational Stiffness of JD2 Model

Fig. 11. Design Ratio and Rotational Stiffness of JD3 Model

Conclusions

Three bolted end-plate joints (JD1–JD3) were studied by comparing experiments with the RFEM Steel Joints model and the EC-3 hand calculation. For moment resistance, all three methods agreed well. RFEM matched the test results closely (within about 6%), and EC-3 gave safe, slightly conservative values. EC-3 can therefore be trusted for strength design.

The main difference was in initial stiffness. RFEM gave reasonable values, but EC-3 greatly overestimated the stiffness of every joint — roughly 1.7 to 2.7 times the measured values. EC-3 stiffness should therefore be used with care, especially in serviceability and deflection checks.

For failure modes, RFEM correctly predicted what was seen in the tests (endplate yielding with both bolt rows failing), while EC-3 predicted a simpler single-bolt mode. In short, RFEM is a reliable tool for predicting joint resistance, stiffness, and failure, and can reduce the need for testing. EC-3 is safe for strength but tends to overestimate stiffness.