Web shear failure of angle-cleat connections loaded at high rates

• Results are presented for both quasi-static and monotonically-increasing dynamic loading to failure of angle web cleat beam–column connections under combined extension and rotation.
• Explicit and implicit dynamic FE models of the connection response are presented, with a discussion of the validation of the models against the experimental data
• Moment-rotation and axial force-extension graphs are presented from both the experimental and numerical model tests.
• Failure mechanisms are discussed, along with the connections' sensitivity to load rate.
• Some parametric study results are also presented from the numerical analyses.

Robustness of structures to prevent progressive collapse has been considered by different building codes since the Ronan Point accident in the UK in 1968 and research on this type of collapse was brought to the fore after the building collapses at the World Trade Center on 9/11 2001. In the case of losing a column, to maintain the integrity of the building large end rotation of the beams is likely to be required in order to transfer the vertical loads from the floor above by re-distribution of loads through the remaining structure. For this reason connections are important in enabling the structure to bridge over the lost column. Connections also need to be capable of resisting high strain rates arising from the dynamic redistribution of moments and tension loads which means they require high ductility to dissipate energy and undergo deformation without failure.This paper presents results from both experimental tests conducted on connections under quasi-static and rapidly applied loading, and a series of ANSYS LS-DYNA finite element analyses which have been developed to model the connection response. A web-cleat connection model, with its complex geometry, has been produced and validated against experimental data. The effect of rate of applied loading on connection response has been investigated both experimentally and by numerical modeling. It is important to understand the effect of loading rate on the response of connections in dynamic frame response to column loss. The results indicate that web angle cleat connections are relatively insensitive to the rate of loading within the range considered here. This suggests that static characterisation of web angle cleat connections may yield suitable data for use in dynamic analysis of frame response in column loss scenarios.