Does anyone have a design reference that provides guidance on what form pressure should be used when external form vibrators are utilized? In my research, I find several sources that say that form pressure may be significantly increased when external form vibrators are used, but I haven't found a reference that gives specific guidance. The closest thing to specific guidance I have found is the following excerpt from Caltrans Concrete Technology Manual: "The method of consolidating concrete inside the forms is also a factor that affects the magnitude of the effective fluid pressure. Consolidating concrete using internal vibrators results in temporary lateral pressures, because it causes concrete to behave as a fluid for the full depth of vibration (locally to the area of vibration), generating up to at least 10 - 20% greater pressure. If external vibrators are used, the loads it exerts on the forms must also be taken into consideration in form design as it essentially hammers the form against the concrete." This reference would suggest that a pressure as high as 20% greater than fluid pressure should be used, which for tall pours would seem to be unmanageable. Does anyone know of any other references or have any suggestions?
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Jeremy Shively P.E., M.ASCE
Engineer V
Granite Construction Company
Santa Barbara CA
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