The　median　S-N　curves　for　laser　beam　welded　6156　Al-alloy　butt　joints　and　T-joints　and　crack　growth　rate　curves　for　the　base　material　were　determined　by　fatigue　experiments　at　stress　ratio　R　=　0.5,　0.06,　1,　respectively.　The　results　showed　that　the　fatigue　strength　of　6156　Al-alloy　butt　joint　is　obviously　higher　than　that　of　T-joint.　The　fatigue　limit　and　the　crack　growth　threshold　were　proposed　to　determine　the　initial　crack　size　for　butt　joint　and　T-joint.　A　fatigue　life　prediction　approach　based　on　crack　closure　was　proposed,　which　can　take　into　account　the　effect　of　welding　residual　stress.　The　predicted　lives　using　the　proposed　approach　agreed　well　with　the　experimental　results.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.