Robust composite joints

Abstract

“Disasters” such as seismic events, impact or fire loading to structural elements of crucial importance highlight the significance of structural design for robustness. Consequently, exceptional load scenarios are to be considered. The question whether the joints of structures designed according to the current version of Eurocodes have adequate load bearing and defor­mation capacity for such load cases arises. The “alternate load path method” plays a key role in structural design for robustness. By using this design approach, redistribution and distribution of the existing and additional loads, respectively, to the intact structural elements should be enabled after a local failure such as “loss of a column”, preventing so the progressive collapse of the structure. In order to pursue the aforementioned goal, sufficient bearing as well as rotational capacity of the joints are required. In particular, for exceptional events, change of the moment’s sign in the area of the joints is often to be observed. However, until today, attention has been paid mainly to the response of composite joints under negative moments. Herein, besides this load case, the corresponding one of positive moments is investigated as well as the development of a membrane action that supports the load redistribution but requires a tension force capacity of the joints. Experimental research for the load case “loss of a column” was undertaken on both single composite joint specimens and composite frames. Also, an integrated design method, the beamline method, is analysed and constructional recommendations for design of ductile compo­site joints were developed and are herein presented.