What are the regulations for the weld connection of steel structure, and what are the requirements for the weld size of lap welding, plug welding and slot welding?

1. The stress and structural welds of structural members in the steel structure can be butt welds, fillet welds, combination welds of butt and fillet welds, plug welds and slot welds. The butt welds of important connections or with equal strength requirements should be penetration welds, and the partial penetration welds can be used for thicker plates or without penetration.
2. The groove form of butt weld should be selected according to the plate thickness and construction conditions according to the current national standard Code for Welding of Steel Structures GB 50661.
3. When materials with different thickness and width are butt jointed, a smooth transition shall be made, and the slope value at the joint shall not be greater than 1:2.5
4. When bearing dynamic load, plug welding, slot welding, fillet welding and butt welding shall meet the following requirements:
(1) When plug welding and slot welding are used for components bearing dynamic load without fatigue calculation, the distance between the edge of the hole or slot and the edge of the component in the direction perpendicular to the stress shall not be less than 5 times of the thickness of the component, and shall not be less than 2 times of the width of the hole or slot; The length of the longitudinal fillet weld of the overlapping connection at the end of the component shall not be less than the vertical spacing a between the welds on both sides, and the spacing a shall not be greater than 16 times the thickness t of the thinner part without plug welding, slot welding and other measures.
(2) Fillet weld with leg size less than 5mm shall not be used;
(3) Intermittent groove welds and intermittent fillet welds are strictly prohibited;
(4) Fillet weld shall be used to strengthen the combination weld of butt and fillet weld and the full penetration groove weld of T-shaped connection. The size of the strengthened weld leg shall not be greater than 1/2 of the thickness of the thinner part of the connection part, but the maximum value shall not exceed 10mm;
(5) For the connection subject to dynamic load and fatigue check, when the tensile stress is perpendicular to the weld axis, partial penetration butt weld is strictly prohibited;
(6) Except for the transverse welding position, L-shaped and J-shaped grooves should not be used;
(7) When butt joints with different plate thicknesses bear dynamic load, they shall be made into smooth transition.
5. The size of fillet weld shall meet the following requirements:
(1) The minimum calculated length of fillet weld shall be 8 times of its weld leg size hf, and shall not be less than 40mm; The calculated length of the weld shall be the length of the weld after deducting the length of arc striking and arc stopping;
(2) The minimum length of intermittent fillet weld segment shall not be less than the minimum calculated length;
(3) The minimum leg size of fillet weld should be taken as per Table 2, and the leg size of fillet weld should not be less than 5mm under dynamic load;
(4) When the thickness of the thinner plate in the welded member is not less than 25mm, the fillet weld with the opening groove should be used;
(5) Fillet weld shall be used for welding connection, and thick plate shall not be welded to thin plate.
6. The size and arrangement of fillet weld of lap joint shall meet the following requirements:
(1) For the parts that transmit axial force, the minimum lap length of the lap connection shall be 5 times the thickness of the thinner part, and shall not be less than 25mm (the smaller of t1 and t2 is taken for t in Figure 2; hf is the size of the weld leg, according to the design requirements), and the longitudinal or transverse double fillet weld shall be welded;
(2) When only longitudinal fillet weld is used to connect the end of the profile steel member, the width of the profile steel member shall not be greater than 200mm. When the width is greater than 200mm, transverse fillet weld or intermediate plug weld shall be added; The length of the longitudinal fillet weld on each side of the profile steel member shall not be less than the width of the profile steel member;
(3) When lap welding is adopted for lap connection of section steel members, continuous welding shall be carried out at the corners. When the lap fillet weld at the end of the rod is welded around, the length of the weld around should not be less than 2 times the size of the weld leg, and should be welded continuously;
(4) The maximum leg size of the lap weld along the edge of the base metal shall be the thickness of the base metal when the plate thickness is not more than 6mm, and the thickness of the base metal minus 1mm~2mm when the plate thickness is more than 6mm;
(5) For the casing connection that transfers load with lap weld, only one fillet weld can be welded, and the pipe lap length L shall not be less than 5 (t1+t2), and shall not be less than 25mm. The size of lap weld leg shall meet the design requirements.
7. The size, spacing and weld height of plug weld and slot weld shall meet the following requirements:
(1) The effective area of plug welding and slot welding shall be the nominal area of round hole or long slot hole on the bonding surface.
(2) The minimum center spacing of plug weld shall be 4 times of the hole diameter, the minimum longitudinal spacing of slot weld shall be 2 times of the slot length, and the minimum spacing of two rows of slot holes perpendicular to the slot length direction shall be 4 times of the slot width.
(3) The minimum diameter of plug welding hole shall not be less than the thickness of the opening plate plus 8 mm, and the maximum diameter shall be the greater of the minimum diameter plus 3 mm and the thickness of the opening piece 2.25 times. The length of slot hole shall not exceed 10 times of the thickness of the opening piece. The minimum and maximum slot width shall be the same as the minimum and maximum hole diameter of plug welding hole.
(4) The weld height of plug welding and slot welding shall be the same as that of the base metal when the thickness of the base metal is not more than 16mm; When the base metal thickness is greater than 16mm, it shall not be less than half of the base metal thickness and 16mm, whichever is greater.
(5) The size of plug weld and slot weld shall be calculated and determined according to the shear force on the bonding surface.
8. Intermittent fillet welds can be used in secondary components or secondary welded connections. The length of intermittent fillet weld segment shall not be less than 10hf or 50mm, and its clear distance shall not be more than 15t (for compression members) or 30t (for tension members), t is the thickness of thinner weldment. Intermittent fillet welds should not be used in corrosive environment.