Dynamic behavior of tensile anchors to concrete

A research project has recently been completed that had the objective of ob taining technical information to determine how the seismic behavior and str ength of anchors (cast-in-place, expansion, and undercut) and their support ing concrete differ from the static behavior To that end, a research progra m was carried out on the dynamic behavior of anchors (fasteners) to concret e. The research program comprised four tasks: 1) static and dynamic behavio r of single tensile anchors (250 tests); 2) static and dynamic behavior of multiple tensile anchors (179 rests); 3) static and dynamic behavior of nea r-edge anchors (150 tests); and 4) static and dynamic behavior of multiple- anchor connections (16 tests). The anchors tested were selected based on th eir reported frequency of use in nuclear power plants in the U.S. Anchors i ncluded cast-in-place headed bolts, grouted headed bolts, two wedge-type ex pansion anchors, one sleeve-type expansion anchor and two undercut anchors. Loading conditions included tension, shear; and combined tension and shear : Test variables included different concrete strengths and types, loading r ate, and the presence of cracks. In this paper; the behavior of single and multiple tensile anchors is described. Under seismic loading, the tensile capacities of most anchors tested in thi s study are at least as high as under quasistatic loaning. As a result, mos t anchors tested in this study: if designed for ductile behavior under quas istatic loading, would behave in a ductile manner under seismic-type loadin g as well. The previously stated conclusions are not true for wedge-type ex pansion anchors; these tend to pull our and pull through under dynamic load ing and should be evaluated individually to determine their seismic adequac y. The previously stated conclusions are also not true for grouted anchors installed in cored holes; these tend to pull out in cracked concrete.