Report - PEER - University of California, Berkeley

While the global drift of the buildings (not presented here; see Fischinger et al.2004) never exceeded 1%, large compression deformations (more than 0.5%) wereobserved in higher buildings subjected to moderate earthquakes. In these cases, wallto floor ratio becomes very important. If this ratio is more than 2%, compressionshould be within acceptable range. However, confinement in needed in walls withlower wall-to-floor ratio.This example might demonstrate that even simple deterministic studies usingsimplified push-over procedures may provide meaningful information about seismicvulnerability of structures.4. PARTIAL-STRENGTH CONNECTIONS IN STEEL STRUCTURESIn steel construction in Slovenia partial-strength connections were very often usedwithout assuring the rotation capacity of these connections. Especially asymmetricalend-plate bolted connections with extended end-plate at the upper and flush end-plateat the lower side of the connection were popular (see Fig. 12). They are suitable toresist gravity loading in non-sway frames and can be used also in sway frames whenhorizontal loading is not very important as in the case of moderate wind loading innon-seismic regions. In seismic conditions the tension can arise also at the weakerside of the connection, which then acts as a partial-strength connection withpredominant non-ductile failure at bolts. Under the German influence this type ofconnections was introduced into Slovenia and sometimes used without sufficientprecaution disregarding the fact that Slovenia is unlike Germany a seismic region.To get an insight into the behavior of asymmetric endplate connectionsexperimental and numerical investigations were performed. The main purpose of thiswork was to assess the sensitivity to weaker side collapse of the connections inearthquake conditions as well as further behavior of partly damaged frames.4.1 Experimental AnalysisTee shaped beam-column assembly was chosen to represent a part of a real framearound the connection. The beam part of the assembly was made of IBE 300 hotrolled profile and the column part of HEB 200 hot rolled profile. The tests were rununder displacement control following the sinusoidal pattern with constant amplitudeof approximately two times the yield displacement. The constant frequency of 0.5 Hzwas applied.The first specimen was able to withstand 93 cycles (Fig. 13) and the second one118 cycles before collapsed. Relatively large number of cycles was obtained becausethe imposed displacement amplitude of two times the yield displacement is relativelysmall and can be expected in moderate earthquakes.301