TILT-UP CONSTRUCTION - Brock White

General andTechnical InformationAnchor/Insert CapacityAnchors/Inserts are designed to resist loads appliedas direct tension, shear or a combination of the two.The following equations have been developed to predictconcrete capacity of anchors/inserts and are applicableto anchors/inserts that are properly embedded in unconfinedconcrete. Confinement of the concrete, either froman applied compressive force or reinforcement is knownto increase the load carrying capacity of concrete. At thistime, design equations for anchors/inserts, which includereinforcement confinement, have not been developed.General and TechnicalInformationThe Strength of the ConcreteWhen a load is applied to an insert embedded in concrete,it induces a corresponding resistive force in theconcrete. Insert failures can be predicted with a reasonabledegree of accuracy by using the following equation forconcrete breakout from ACI 318 Appendix D.f’ c= Compressive strength of the concrete at time of lift1.5P concrete= 0.75 x j c,Nx l x 24 x √⎺ f’ ch efP concrete= Maximum tension load carried by concrete and;l = Reduction factor for use with lightweightconcrete, see page 6;j c,N= Factor for cracked concrete: 1.0 if cracked and1.25 if uncracked.SurfaceAreaofTheoreticalShearCone35°d hP concreteConcreteSurfaceIllustration A2h ef7Combined Shear and Tension InteractionAnchors/inserts and bolts that are subjected to combinedshear and tension loading should satisfy the followingequation:5 5f v 3 f(t 3F v) + < 1.0( F t)Where:f v = applied shear loadF v = shear safe working loadf t = applied tension loadF t = tension safe working loadPcConcreteSurfaceSurface Areaof TheoreticalleShear Cone35 odh02-09