Global　dynamics　of　an　autoparametric　beam　structure　derived　from　a　flexible　L-shaped　beam　subjected　to　base　excitation　with　one-to-two　internal　resonance　and　principal　resonance　are　investigated.　Hamilton＇s　principle　is　employed　to　obtain　the　nonlinear　partial　differential　governing　equations　of　the　multi-beam　structure.　A　linear　theoretical　analysis　is　implemented　to　derive　the　modal　functions,　and　the　orthogonality　conditions　are　established.　The　analytical　modal　functions　obtained　are　then　adopted　to　truncate　the　partial　differential　governing　equations　into　a　set　of　coupled　nonlinear　ordinary　differential　equations　via　the　Galerkin＇s　procedure.　The　method　of　multiple　scales　is　applied　to　yield　a　set　of　autonomous　equations　of　the　first-order　approximations　to　the　response　of　the　dynamical　system.　The　Energy-Phase　method　is　used　to　study　the　global　bifurcation　and　multi-pulse　chaotic　dynamics　of　such　autoparametric　system.　The　present　analysis　indicates　that　the　chaotic　dynamics　results　from　the　existence　of　ilnikov＇s　type　of　homoclinic　orbits　and　the　parameter　set　for　which　the　system　may　exhibit　chaotic　motions　in　the　sense　of　Smale　horseshoes　are　predicted　analytically.　Numerical　simulations　are　performed　to　validate　the　theoretical　results.