Formwork Tie Load and Spacing
Sizes the wall-form ties that take the lateral concrete pressure in tension: tie load = pressure x horizontal spacing x vertical spacing; max tributary = SWL / pressure. At 600 psf on a 24 x 24 in grid, each tie carries 2,400 lb - inside a 3,000 lb tie (5 sf max tributary). Pour faster (900 psf) and the tie hits 3,600 lb, over - tighten to 18 in and it drops to 2,025 lb. A tie failure is a form blowout; the tie manufacturer and ACI 347 govern.
Formula and source
tie_load_lb = lateral_pressure_psf x h_spacing_ft x v_spacing_ft; utilization = tie_load_lb / tie_swl_lb; max_trib_area_ft2 = tie_swl_lb / lateral_pressure_psf.
Formwork tie-load identity by name (tie load = pressure x tributary area; max tributary = SWL / pressure); first-principles statics.
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