Mechanical response of fully bonded bolts under cyclic load

The mechanical properties of a bolting system under cyclic loading were investigated experimentally by pullout tests. Bolts of different diameters were inserted into steel tubes and bonded together by resin or cement to prepare simulated bolting systems for further pullout tests. Uniaxial compression tests showed that cement has a comparatively higher stiffness and peak stress compared with resin. A monotonic pullout test was conducted to determine the safety threshold for cyclic loading and the stress distribution along the steel tube. Interesting results were observed for specimens that were tested under different cyclic loading patterns. For instance, the deformation-memory property of the bolting system under a cyclic disturbance was evaluated; the triggering mechanism of creep behavior under cyclic loading is discussed; contributing factors associated with a hysteresis loop during a cyclic process were investigated; and weakening factors, such as the amplitude, upper loading level, and lower loading level were considered. The influence of cyclic mode on the failure patterns of specimens with different bonding materials was analyzed. Dominating failure modes, such as reversed-cone shaped resin agglomeration, flake-shaped scrapping, and bolt-resin interface debonding for resin-bonded specimens were exhibited and these are discussed. An annulus-shaped bonding block, brittle collapse, and cement-tube interface debonding for cement-bonded specimens is displayed and elucidated.