Strain rate behaviour of adhesive anchors in masonry Abass Braimah a,b,⇑ , Rick Guilbeault a , Ettore Contestabile a,b a Canadian Explosives Research Laboratory, Natural Resources Canada, 555 Booth Street, Ottawa, ON K1A 0G1, Canada b Department of Civil and Environmental Engineering, Carleton University, 3432 Mackenzie Building, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada article info Article history: Received 20 June 2013 Revised 17 November 2013 Accepted 24 February 2014 Available online 21 March 2014 Keywords: Adhesive anchors Impulse Impact Blast Retrofit Windows Dynamic increase factor abstract Global terrorism has led to increasing use of anti-shatter film to upgrade window glass to mitigate the hazard associated with glass breakage. When the anti-shatter film is anchored, blast loading is trans- ferred to the structure of the façade through steel anchors. Adhesive anchor are commonly used to fasten window frames to concrete and masonry elements. However, their behaviour in masonry is not very well researched. This paper presents an experimental program to study the behaviour of steel anchors in masonry sub- strates under impact loading. The adhesive anchor-substrate systems consisted of steel rods bonded to clay brick or concrete masonry units with an epoxy-based adhesive. Two penetration angles of 45° and 90° and different embedment depths were investigated. The adhesive anchor-substrate systems were tested in a specially designed drop mass test frame. Dynamic increase factors were recommended for design of anchors embedded in masonry under blast loading. The test results show that clay brick substrate is very brittle and leads to a dynamic increase factors of less than 1.0. For steel anchors in concrete masonry substrate, dynamic increase factors of greater than 1.0 are recommended for design of adhesive anchor-substrate systems under high rates of loading such as blast and impact. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The global spate of terrorism has resulted in increased blast vul- nerability assessments and retrofit of existing buildings to increase their blast resistance. At a minimum, window glass in buildings is upgraded by applying anti-shatter film to window glass to reduce injuries and fatalities caused by glass shards. When blast pressure waves from an explosion impinge on window glass it is likely to break into shards (‘‘knives and daggers’’) which have a potential to cause injury and fatality to building occupants (Fig. 1). According to Mallonee et al. [1], 66% of respondents to a survey conducted by the Oklahoma State Department of Health after the attack on Alfred P. Murrah Building attributed their injuries to glass shards while Norville et al. [2] reported that over 40% of the glass injuries were suffered by people within about 3 m from walls with glazing. Thus, eliminating the hazard associated with glass breakage is essential for limiting injury and fatalities to building occupants in an explosion event. Whether in the target or neighbouring buildings, application of anti-shatter film to window glass can effectively mitigate glass shard injuries. Anti-shatter film is a polyester-based material with high tensile strength and flexibility. When applied to window glass, anti-shatter film binds glass shards (Fig. 1) together and depending on the anchorage method can be thrown into the interior of the building or transfer blast loading to the window frames. There are, princi- pally, three methods for applying anti-shatter film to window glass: daylight, wet-glazed and mechanical anchorage application meth- ods. The daylight application method consists of bonding the anti-shatter film to the visible area of glass and terminating a few millimetres from the window frame. In the wet-glazed application method the anti-shatter film is bonded to the visible glass area and attached to the window frame with a high strength structural adhe- sive while in the mechanical anchorage method the anti-shatter film is bonded to the glass pane and mechanically fastened to the window frame with screws and battens [3]. When blast pressure waves from an explosion impinge on a glass window retrofitted with anti-shatter film applied by the day- light method, the glass breaks at approximately the same load level as the unretrofitted glass. Unlike the unretrofitted glass which breaks into ‘‘knives and daggers’’ (Fig. 1), the glass shards are bound together in the anti-shatter film and driven into the interior http://dx.doi.org/10.1016/j.engstruct.2014.02.018 0141-0296/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Civil and Environmental Engineering, Carleton University, 3432 Mackenzie Building, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada. Tel.: +1 613 520 2600x2077; fax: +1 613 520 3951. E-mail address: abass_braimah@carleton.ca (A. Braimah). Engineering Structures 67 (2014) 96–108 Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct