Behavior, Design and Testing of Anchors in Cracked Concrete
Appears on pages(s):
anchors (fasteners); cracking (fracturing); failure mechanisms; failure; loads (forces); shear properties; structural design; tension; Structural Research
Reinforced concrete structures will generally be cracked under service load due to tensile stresses caused by loads or by the restraint of imposed deformations. Therefore, in general, the design of anchors should be based on the assumption that the concrete is cracked. Under tension loading, anchor behavior is significantly influenced by cracks, depending on the type and design of the anchor. If the failure is caused by concrete cone break-out, the failure load is reduced by approximately 30 to 40 percent compared to the value expected in uncracked concrete. If the failure is caused by pullout (expansion or adhesive anchors), the reduction of the failure load may be much higher. Furthermore, installation inaccuracies may have a very significant negative effect on anchor behavior in cracked concrete. Under shear loading, the behavior of all types of anchors away from edges is not significantly influenced by cracks. The failure load of fastenings close to the edge is reduced by cracks by about 30 percent; however, the reduction is almost independent of the type of anchor. A method for the design of fastenings based on rational engineering models and nonlinear fracture mechanics is proposed. It distinguishes between the different loading directions and failure modes and takes into account all relevant influencing factors.