I have fly braces which restrain EBF link and the other end of these fly braces are anchored to the underside of the double tee flange. Should I be using C1 seismic load type or static load type when designing the fixings for these fly braces?
Also, is C1 seismic load type used to take into account of the cyclic nature of the seismic force or is it to consider for concrete cracking?
Hi Brian,
Thanks for your question.
Although we acknowledge that prestressed elements behave differently from normal reinforced concrete, we advise following the same procedure, given that it is a more conservative approach.
Regarding your second question, please find an extract from one of our articles below explaining the differences between the different seismic categories:
For seismic performance category C1 qualification the controlled crack width is w = 0.5 mm, both for tension and shear testing. The load protocols are cyclic decreasing amplitude load patterns, very similar to low cycle fatigue testing. The crack widths are not changing during the qualification testing.
For seismic performance category C2 qualification the controlled crack width depends on the type of testing and can be constant w = 0.5 mm or w = 0.8 mm, or the crack width is cyclically opened and closed in the w = 0 to 0.8 mm range. The load protocols are cyclic increasing amplitude load patterns, that is widely used for simulated seismic testing of structures. In tension load assessment, the first two-thirds of the load cycles are performed at constant w = 0.5 mm crack width and the last one-third of the load cycles are performed at constant w = 0.8 mm crack width. In shear load assessment, the load cycling is performed at constant w = 0.8 mm crack width. In crack cycling assessment, at two different pre-determined tension load levels, the cracks are cyclically opened and closed in the w = 0 to 0.8 mm range- following an increasing amplitude protocol.
For the static cracked scenario, the crack width is constant at 0.3mm and the load is not cyclic.
More information can be found on this article: https://ask.hilti.co.nz/article/post-installed-anchor-design-in-new-zealand/8io0oj
Please do not hesitate to contact us should you have any other questions.
Kind Regards,
Samuel Aguiar - Engineering Marketing Manager