This　study　presents　experimental　investigations　on　concrete-filled　steel　tubular　(CFST)　Warren　trusses,　focusing　on　the　stiffness　of　both　the　overall　truss　and　its　joints.　Results　indicate　that　axial　force　distributions　closely　match　those　predicted　by　an　ideal　pin-jointed　truss　model,　with　joint　deformation　contributing　up　to　20　%　to　the　total　truss　deflection.　Analytical　models　for　the　axial　stiffness　of　CFST　K-joints　were　developed,　explicitly　accounting　for　the　effect　of　infilled　concrete　under　both　tensile　and　compressive　brace　loading.　Joint　stiffness　equations　were　derived　through　finite　element　analysis　and　nonlinear　regression.　These　were　integrated　into　a　predictive　model　for　the　flexural　stiffness　of　CFST　Warren　trusses.　Validation　against　experimental　data　showed　that　the　proposed　method　accurately　captures　joint　effects,　with　prediction　errors　within　12　%.　©　2025　Elsevier　Ltd