Behaviour of undercut anchors subjected to high strain rate loading

Abstract

Abstract The increase in global terrorism has culminated in the protection of high profile buildings and monuments against the effects of blast loading – a high strain rate loading event. Depending on the design basis threat, the level of protection can range from facade and fenestration upgrade to retrofit of the structural systems. Post-event surveys after the Oklahoma City Bombing and other similar events indicated widespread window glass damage. Most of the injuries reported were attributed to the glass shards, especially in buildings proximate to the target building. Thus, the least protection recommended for buildings is to retrofit window glass against glass shard injury. When the window retrofit consists of anti-shattered film anchored to the window frames, blast loads are transferred to the window frames and ultimately to the structure of the facade through discrete window retention steel anchors. A lot of research has been conducted to investigate the response of upgraded windows however little research is available on the load transfer from the window frames to the facade structure through the window retention anchors. This paper presents results from a finite element analysis program to investigate the tensile behaviour of post-installed undercut anchors under high strain rates. Strain rates varying from 10-5 to 103 s-1 were applied to single undercut steel anchors embedded in concrete blocks. Anchor diameters of 12 mm, 16 mm and 20 mm with various embedment depths were selected for the analyses. The analyses results show increased tensile capacity of undercut anchors with increase in strain rate. The maximum dynamic increase factor for tension of undercut anchors at strain rate of 103 s-1 was about 1.60 for the anchors investigated.