PSI - Issue 64

Maximilian Fehr et al. / Procedia Structural Integrity 64 (2024) 885–892 Maximilian FEHR, Michael BAUR, Giovacchino GENESIO / Structural Integrity Procedia 00 (2019) 000 – 000

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Table 3. Steel-to-steel connection stiffness Degree of Freedom

Stiffness 9.35 * 10 8

Axial stiffness Shear stiffness

∞

∞

A similar approach was taken for the concrete-to-steel connection. To determine the stiffness the ETA for the Hilti HVU2 adhesive capsule (ETA-16/0515, 23.08.2022) was used. With the corresponding stiffnesses provided by the ETA the axial and shear stiffness was calculated. The connection was realized with 8x HVU 2 + HAS-U 5.8 M20 (figure 4) which resulted in the stiffness values listed in table 4.

Table 4. Concrete-to-Steel connection stiffness Degree of Freedom Stiffness Axial stiffness

8.55 * 10 5 kN 2.00 * 10 5 kN/m

∞

Shear stiffness

It should be noted that the stiffness was assumed to be linear elastic according to ETA-16/0515 values given in table C5/6 for cracked concrete, as the anchors behave elastically up to the design resistance. The resulting loads were checked against the resistance values given in the table C10/12 of the ETA (table 4).

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5

4

Fig. 4, post-installed steel-concrete connection with chemical anchors, shear (Frame A, left) und tension/compression (Frame B, right)

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The calculation of the seismic forces and deformations was performed with an response spectrum analysis (RSA). The design spectrum is given by the SIA 261 for the seismic Zone Z1, soil class A (rock), importance factor of 1.5 (hospital building) and a behavior or ductility factor of q=1.0. The elastic design spectrum for 5% damping is depicted in Figure 5. Because the hospital should remain fully operational after an seismic event, no or only minor local plastic deformations are acceptable. A non-ductile design was therefore performed. The connection forces within frames A and B are obtained by using the effective connection stiffnesses from Tables 3 and 4. Figure 5 shows the resulting link forces for frame A (shear forces) and frame B (axial forces) for a seismic load in the positive x-direction. For the other direction the distribution of the connection forces over the height are similar and are not shown here. The maximum tension forces on the fourth floor result from a change in the lateral structural stiffness over the building height, resulting in high shear forces on that floor. In order to get a better understanding of the overall structural behavior, a nonlinear push-over analysis was also performed according to the first mode shape in the positive x-direction to verify the assumed structural behavior. The pushover analyses is conducted solely for the first eigenmode. In generally a push-over analysis is not well suited to accounting for torsional effects or irregular structures over height (H. Meireles et al. (2006)). 0 1 2 -100 -50 0 50 100 150 200 250 300 350 floor i [-] Link forces [kN]

shear loads frame A

axial load frame B