This　paper　studies　the　effect　of　the　diameter　and　number　of　bars　on　the　cyclic　behavior　of　the　bar　damper　(BD).　A　BD　is　a　metallic　damper　made　of　several　steel　bars　welded　between　the　bottom　and　top　anchor　plates.　The　energy　dissipation　mechanism　of　the　BD　primarily　depends　on　the　flexural　yielding　deformation　of　the　bars　under　either　unidirectional　or　bi-directional　loads.　To　achieve　this　aim,　seven　specimens　were　tested　with　four　different　diameters　of　bars　and　four　different　numbers　of　bars.　A　series　of　quasi-static　cyclic　loading　tests　were　performed　on　the　BD　specimens　in　the　laboratory.　In　addition,　a　comparative　study　of　all　the　geometrical　parameters　of　the　BD,　including　the　height　of　the　BD　was　performed.　The　experimental　results　showed　that　all　BD　specimens　exhibited　stable　hysteretic　behavior　and　low　yield　displacement.　The　BD　specimen　demonstrated　a　damping　ratio　of　34　%-41　%　and　a　ductility　range　of　27–69.　The　results　of　the　comparative　analysis　concluded　that　the　height　of　the　bars　mainly　affects　the　yield　displacement,　ultimate　displacement　and　cumulative　displacement　of　the　damper,　while　the　diameter　and　number　of　bars　affect　the　yield　force　and　ultimate　force　of　the　damper.　©　2025　Institution　of　Structural　Engineers