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SUMMARYPseudo-dynamic tests on a large-scale model of an existing six-pier bridge were performed at the ELSA laboratory using the substructuring technique. Two physical pier models were constructed and tested in the laboratory, while the deck, the abutments and the remaining four piers were numerically modeled on-line. These tests on a large-scale model of an existing bridge are the ÿrst to have been performed considering non-linear behavior for the modeled substructure. Asynchronous input motion, generated for the speciÿc bridge site, was used for the abutments and the pier bases. Three earthquake tests with increasing intensities were carried out, aimed at the assessment of the seismic vulnerability of a typical European motorway bridge designed prior to the modern generation of seismic codes. The experimental results conÿrm the poor seismic behavior of the bridge, evidenced by irregular distribution of damage, limited deformation capacity, tension shift e ects and undesirable failure locations.

SUMMARYThe reliability of a Pseudodynamic (PsD) test depends primarily on the accuracy of the control system. Di$culties arise mainly when the method is applied to very sti! or very heavy structures or to structures with a high number of Degrees of Freedom (DoFs). This paper describes the bi-directional PsD testing of a full-size three-storey building. The tested specimen is a composite structure with plan dimensions of 12;16 m and height of 9)5 m, made of steel columns and beams combined with composite reinforced concrete slabs. The PsD test included the application of two uncorrelated accelerograms along the horizontal directions X and >. Since the structure was not symmetric about the >-axis, the possibility of torsion was considered by taking into account both horizontal displacements and the yaw rotation at every #oor. Three displacement-controlled hydraulic actuators were thus used at each #oor to impose these three DoFs while a fourth actuator with special control strategy was added to optimize the distribution of loads among the pistons. The validity of the testing methodology was veri"ed by performing also a dynamic random burst test on the specimen which was afterwards pseudodynamically reproduced.

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Seismic tests have been conducted on two 3-storey structures protected with pressurized fluid-viscous spring damper devices. One of the structures was a reinforced concrete frame with clay elements in the slabs, while the other one was a steel frame with steel/concrete composite slabs. The spring dampers were installed through K bracing in between the floors. The tests were performed by means of the pseudodynamic method, which allowed the use of large and full-size specimens, and by implementing a specific compensation strategy for the strain-rate effect at the devices. The test results allowed the verification of the adequacy of the attachment system as well as the comparison of the behaviour of the unprotected buildings with several protected configurations, showing the benefits of the application of the devices and the characteristics of their performance. The response of the protected structures was always safer than that of the unprotected ones mainly due to a significant increase of equivalent damping. The increase in the damping ratio depends on the level of deformation. Copyright © 2004 John Wiley & Sons, Ltd