<p>Experimental measurements for the motion responses of the moored barge alongside a bottom-mounted platform in beam sea are carried out, by which the behavior of motion responses of the barge and the forces on hawsers and fenders are considered. The sway and roll motions are the most important responses in six degrees-of-freedom. The seaward motion responses are mainly held by the hawsers; while the landward motion responses are mainly astricted by the fenders. Correspondingly, the variation tendencies between the tension forces on the hawsers, the compressed deformation and forces of the fenders, and the sway and roll motion responses of the barge generally have the similar behavior. The nonlinear characteristic in this work is mainly from the force-deformation relationship of fenders. With the increase of incident wave amplitudes, the generally decreased normalized amplitudes can be observed, including the tension forces of hawsers, the compressed deformation and the forces of the fenders. More relative kinetic energy is absorbed by the fenders under larger incident wave amplitudes, which is the essential reason for this phenomenon. The dependence of normalized sway/roll motion responses with incident wave amplitudes is more complex. The normalized sway and roll motion amplitudes around the natural roll periods significantly increase with the increase of incident wave amplitudes. This might be the most noteworthy phenomenon in practical engineering.</p>