High level shaker tests of the HDR reactor building

In the experiments excitation levels between OBE and SSE (German locations) with levels between 7 and 8 on the modified Mercalli scale were reached. The peak loads were up to a factor of 4.8 higher then in the case of the Friaul earthquake. The HDR reactor building, which was not designed againt earthquake, withstood those loads without global failure. The rocking mode frequency dropped from about 1.5 Hz to 1.0 Hz while increasing the load, which corresponds to a reduction of the soil stiffness by a factor of about two. Damping values for the rocking mode incrased from about 6 to 9% and 5.2 to 8.8%, for the bending mode from 2.7 to 3.5% and 4.6 to 6%, depending on the direction of vibration. While peak accelerations and displacements in the building reached maxima of 0.4 g and 5 cm respectively, local damage such as concrete cracking, but no basement uplift and no soil liquefaction occurred. Circumferential cracking around the building and soil subsidence of about 10 cm could be observ ed. The calculations could describe the principal behavior of the building, but in some cases they showed up much conservatism; e.g. the load bearing capacity of the foundation slab was predicted to be 22.000 kgm (conservative) and 38.000 kgm (best estimate), while 67.000 kgm were reached, or the propagation of accelerations in the free field were measured to be roughly up to 5 times smaller then those predicted by calculations