Bi-directional pseudodynamic test of a full-size three-storey building     

F. J. Molina  G. Verzeletti  G. Magonette  Ph. Buchet  M. Gradin 《地震工程与结构动力学》1999,28(12):1541-1566

The reliability of a Pseudodynamic (PsD) test depends primarily on the accuracy of the control system. Difficulties arise mainly when the method is applied to very stiff 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 Y. Since the structure was not symmetric about the Y-axis, the possibility of torsion was considered by taking into account both horizontal displacements and the yaw rotation at every floor. Three displacement-controlled hydraulic actuators were thus used at each floor 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 verified by performing also a dynamic random burst test on the specimen which was afterwards pseudodynamically reproduced. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

The transition zone of the Canary Current upwelling region   总被引：2，自引：0，他引：2  

E. D. Barton  J. Arístegui  P. Tett  M. Cantn  J. García-Braun  S. Hernndez-Len  L. Nykjaer  C. Almeida  J. Almunia  S. Ballesteros  G. Basterretxea  J. Escnez  L. García-Weill  A. Hernndez-Guerra  F. Lpez-Laatzen  R. Molina  M. F. Montero  E. Navarro-Prez  J. M. Rodríguez  K. van Lenning  H. Vlez  K. Wild 《Progress in Oceanography》1998,41(4):455-504

Like all the major upwelling regions, the Canary Current is characterised by intense mesoscale structure in the transition zone between the cool, nutrient-rich waters of the coastal upwelling regime and the warmer, oligotrophic waters of the open ocean. The Canary Island archipelago, which straddles the transition, introduces a second source of variability by perturbing the general southwestward flow of both ocean currents and Trade winds. The combined effects of the flow disturbance and the eddying and meandering of the boundary between upwelled and oceanic waters produce a complex pattern of regional variability. On the basis of historical data and a series of interdisciplinary field studies, the principal features of the region are described. These include a prominent upwelling filament originating near 28°N off the African coast, cyclonic and anti-cyclonic eddies downstream of the archipelago, and warm wake regions protected from the Trade winds by the high volcanic peaks of the islands. The filament is shown to be a recurrent feature, apparently arising from the interaction of a topographically trapped cyclonic eddy with the outer edge of the coastal upwelling zone. Its role in the transport and exchange of biogenic material, including fish larvae, is considered. Strong cyclonic eddies, observed throughout the year, drift slowly southwestward from Gran Canaria. One sampled in late summer was characterised by large vertical isopycnal displacements, apparent surface divergence and strong upwelling, producing a fourfold increase in chlorophyll concentrations over background values. Such intense eddies can be responsible for a major contribution to the vertical flux of nitrogen. The lee region of Gran Canaria is shown to be a location of strong pycnocline deformation resulting from Ekman pumping on the wind shear boundaries, which may contribute to the eddy formation process.  相似文献