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The contribution of CASIEL infill walls to the shear resistance of steel frames

B.M. Ng’andu, D.R.W. Martens, A.T. Vermeltfoort
Eindhoven University of Technology, the Netherlands

In Europe, calcium silicate element (CASIEL) walls are increasingly employed as partitions and external claddings in buildings. The CASIEL infills and the frames mutually interact through framewall interfaces. This interaction has a significant influence on the load transmission paths of building structures. In order to safeguard the walls and the frames, as well as the finishes from damages, this behaviour needs to be understood and translated into design guidelines. This paper presents results of experiments conducted on 10 large-scale CASIEL-infilled steel frames monotonically loaded by inplane shear. Parameters investigated included frame size, rigidity of frame connections, frame-wall interface gaps, and bearing wedges at the frame top-corners. In general, there was an initial stiff load deflection response followed by a much less stiff response during which frame-wall separation occurred and another stiff response leading to, in the majority of cases, diagonal tension cracking in the infill walls. Shear sliding along the top most bed joint was observed in some specimens. The cracking phase was followed by a less stiff phase, but with an increasing load resistance leading to ultimate failure through crushing of the wall. Increasing the size of the bounding frames increased the stiffness of the infilled frames and moderately increased the cracking loads. Initial gaps between the roof beams and CASIEL wall panels resulted in reduced infilled frame stiffnesses during the transition phase, although they did not significantly reduce the cracking loads. By using bearing wedges in the top corners, the influence of the top gaps was practically eliminated. This technique may be significant in developing a construction technique for industrial application of infilled frames. The rigidity of the frame connections did not significantly influence the stiffnesses and cracking loads of the infill panels.

Key words: Infilled frames, calcium silicate elements, stiffness, tensile cracking, shear sliding, crushing