BEHAVIOR OF FASTENERS LOADED IN TENSION IN CRACKED REINFORCED-CONCRETE

Many reinforced concrete structures are designed under the assumption that the concrete is cracked due to external lends or restraint of imp osed deformations (e.g., due to creep, shrinkage, temperature variatio ns or support settlement). Research shows that fasteners will attract cracks or even induce cracking. Therefore, the behavior of different t ypes of fastener tt cracked reinforced concrete has been studied exten sively. Fasteners suitable for use in cracked reinforced concrete such as cast-in situ headed studs or headed anchors, post-installed underc ut anchors, and specially designed torque-controlled expansion anchors show a reduction of the concrete cone failure load of about 25 to 35 percent compared to uncracked concrete when located in or close to cra cks with a width similar to 0.3 to 0.4 mm (0.012 to 0.016 in.). This c rack width can be expected in typical concrete members designed with o rdinary crack control provisions. The failure load of ordinary torque- controlled expansion, deformation-controlled expansion, and bonded anc hors is more influenced by cracks and may be unpredictable, especially if installation inaccuracies that might occur on site are taken into account. Fasteners used in zones with potential concrete cracking must be suitable for this application. A test program to check the effecti ve functioning of fasteners in cracked reinforced concrete is describe d in technical guides by UEAtc and EOTA, a basis for the proposed ASTM specification.