The　analysis　on　the　nonlinear　dynamics　of　the　circular　truss　antenna　is　an　important　problem　for　its　design　and　control　since　its　large　flexible　structure.　This　paper　investigates　the　nonlinear　dynamic　behaviors　of　a　beam-ring　structure　modeling　the　circular　truss　antenna　subjected　to　the　periodic　thermal　excitation.　Based　on　describing　the　displacements　and　the　nonlinear　strains　of　the　beam-ring　structure,　the　kinetic　energy　and　potential　energy　are　calculated　for　the　system.　Using　Hamilton＇s　principle,　the　nonlinear　partial　differential　governing　equations　of　motion　and　the　boundary　conditions　are　derived　for　the　beam-ring　structure.　Applying　Galerkin＇s　approach,　the　nonlinear　partial　governing　differential　equations　of　motion　for　the　beam-ring　structure　are　truncated　into　a　two-degree-of-freedom　system　of　the　ordinary　differential　equation　including　the　quadratic　nonlinearities.　The　four-dimensional　averaged　equation　is　obtained　for　the　case　of　the　primary　resonance　and　1:2　internal　resonance　by　using　the　method　of　multiple　scales.　From　the　averaged　equation,　numerical　simulations　are　presented　to　investigate　the　frequency-response　curves　and　the　influences　of　the　thermal　excitation　on　the　nonlinear　dynamic　responses　of　the　beam-ring　structure.　The　numerical　results　demonstrate　that　there　exist　the　complex　nonlinear　dynamic　phenomena　of　the　beam-ring　structure.　The　finding　phenomena　of　this　paper　are　helpful　for　controlling　the　nonlinear　vibrations　of　the　antenna.　(C)　2019　Elsevier　Masson　SAS.　All　rights　reserved.