Due　to　high　strength-to-weight　ratio　and　resistance　to　corrosion,　glass　fiber　reinforced　polymer　(GFRP)　composites　have　been　used　in　various　civil　structures,　where　the　GFRP　profiles　may　be　perforated　to　allow　bolting,　wiring,　and　pipelining,　causing　stress　concentration　in　load-carrying　scenarios.　Based　on　experimental　and　finite　element　methods,　this　paper　the　stress　concentration　behavior　of　perforated　and　bolted　GFRP　square　hollow　sections　(SHS)　as　a　multi-layer　orthogonal　anisotropic　material.　In　this　study,　GFRP　SHS　specimens　with　a　circular　central　hole　with　a　diameter　of　6,　8　or　10 mm　were　subjected　to　uniaxial　compressive　loading,　with　or　without　high-strength　steel　bolts.　The　mechanical　responses　were　monitored,　and　the　stress　concentration　factors　(SCF)　were　determined.　The　experimental　results　indicated　that　as　the　hole　diameter　increased　from　6 mm　to　10 mm,　the　SCF　rose　from　3.40　to　4.59.　The　presence　of　high-strength　steel　bolts　exacerbated　the　stress　concentration,　with　the　SCF　reaching　a　maximum　of　6.07.　Finally,　a　finite　element　model　was　developed　and　validated　against　the　experimental　results,　and　used　to　predict　the　mechanical　performance　of　specimens　with　a　broader　range　of　hole　diameters　and　bolt　sizes,　considering　the　effects　of　bolt　preloads.　The　finite　element　results　demonstrated　that　the　SCF　increased　with　higher　preload　levels,　and　appropriate　preloading　can　reduce　stress　concentration　compared　to　specimens　without　preload.　©　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.　2025.