To　investigate　the　strength　checking　methods　for　a　semi-cylindrical　header-nozzle　intersection　under　combined　piping　loads,　the　simplified　strength　checking　formulae　for　two　piping　load　combinations,　which　are　typical　in　engineering　practice,　are　suggested　based　on　the　combined　limit　piping　load　interactions　of　the　header.　Furthermore,　three　methods　for　determining　the　allowable　piping　load　parameters　of　the　proposed　formulae,　namely　the　plastic　work　curvature　(PWC)　method　of　inelastic　analysis　route　for　design　by　analysis　(DBA),　the　twice　elastic　slope　(TES)　method　of　inelastic　analysis　route　for　DBA,　and　the　elastic　finite　element　analysis　(FEA)　method　of　elastic　analysis　route　for　DBA,　are　presented　and　compared.　Based　on　the　theoretical　analyses　and　the　parametric　comparison　study　results　of　the　three　methods,　it　can　be　concluded　that　the　PWC　method,　which　can　take　the　hardening　material　effect　on　the　plastic　load　results　into　account　well　and　use　the　engineers＇　experience　independent　plastic　work　as　the　global　indicator　of　gross　collapse,　is　the　most　reliable　one　among　the　three　methods,　while　the　elastic　FEA　method　is　of　great　value　for　engineers　to　estimate　the　allowable　piping　loads　quickly　and　conveniently.　©　2013　American　Society　of　Mechanical　Engineers.