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Number of cycles

FIGURE 34.4 S-N curves for snug-tight anchor rods.

Figure 34.4 shows fatigue test data for anchor rods that were only snug tight. Specimens with a 1:40 misalignment are also included. Under these conditions, the lower-bound fatigue strength corresponds to Category E'. Since no failures occurred below a stress range of 62 MPa in this case, the CAFL at 48 MPa applies regardless of tightening or alignment.

Based on these data, in the AISC Specifications [16] the fatigue resistance of bolts or anchor rods in direct tension, on the tensile stress area, is taken as Category E' in the finite-life range with a CAFL of 48 MPa.

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