To　enhance　the　robustness　of　the　suspended　deck　system　of　half-through　and　through　arch　bridges,　the　suspended　deck　system　of　half-through　and　through　arch　bridges　without　a　stiffening　girder　in　the　longitudinal　direction　of　the　bridges　was　taken　as　the　research　object,　a　robustness　strengthening　structure　with　a　steel　tubular　truss　(STT)　stiffened　longitudinal　girder　was　proposed　for　the　suspended　deck　system,　and　a　comparative　analysis　was　made　on　the　dynamic　responses　of　the　remained　structures　at　the　moment　of　hanger　fracture　before　and　after　the　robustness　strengthening　of　the　suspended　deck　system.　A　test　and　a　finite　element　analysis　were　conducted　on　the　model　of　the　robustness　strengthening　structure　with　an　STT　stiffened　longitudinal　girder,　and　the　mechanical　performance　and　failure　mode　of　the　strengthened　structure　after　the　hanger　fracture　were　studied.　The　effects　of　the　preload　of　finish-rolled　screw-thread　steel　bar,　the　thickness　of　perforated　steel　plate,　and　the　material　on　the　mechanical　performance　of　the　robustness　strengthening　structure　were　discussed.　Research　results　show　that　after　the　suspended　deck　system　is　strengthened　by　the　STT　stiffened　longitudinal　girder,　the　maximum　vertical　displacement　and　stress　of　the　deck　system　reduce　by　1.30(1.31)　and　3.31(1.99)　times,　respectively,　when　the　long　(short)　hanger　fractures.　The　maximum　cable　force　of　the　hanger　adjacent　to　the　fractured　one　reduces　by　1.25　(1.25)　times.　In　the　elastic-plastic　stage,　the　perforated　steel　plate　of　the　structure　strengthened　by　the　STT　stiffened　longitudinal　girder　is　subjected　to　bending　deformation,　and　the　embedded　steel　rebar　near　the　bottom　of　the　cross　beam　is　damaged.　When　the　ultimate　load　is　reached,　a　crack　appears　on　the　weld　between　the　middle-lower　stiffened　steel　plate　and　the　perforated　steel　plate.　Then,　a　crack　appears　on　the　weld　between　the　lower　chord　and　the　perforated　steel　plate,　and　the　carrying　capacity　is　thereby　lost.　The　reasonable　preload　of　the　finish-rolled　screw-thread　steel　bar　is　50　kN,　and　the　reasonable　thickness　of　the　perforated　steel　plate　is　20　mm.　The　ultimate　load　of　the　strengthened　structure　increases　by　11.9%　when　the　material　of　the　perforated　steel　plate　is　updated　from　Q235　to　Q345.　This　indicates　that　enhancing　the　material　strength　of　the　perforated　steel　plate　can　effectively　improve　the　ultimate　bearing　capacity　of　the　strengthened　structure.　To　sum　up,　utilizing　the　STT　stiffened　longitudinal　girder　to　reinforce　the　suspended　deck　system　in　half-through　and　through　arch　bridges　can　effectively　strengthen　its　robustness.　©　2022　Chang＇an　University.　All　rights　reserved.