When an earthquake strikes, the parts of a steel building that are most prone to damage are the connections. The roots of beam-column connections tend to break frequently because they are subjected to the greatest forces. To avoid this, there are many ways in the current design, the following are four ways to strengthen the nodes:
1. Wing cover plate reinforcement
Weld the steel plate directly on the outer edge of the upper and lower wing plates of the beam. This can not only effectively improve the bending capacity of the beam, but also has a relatively small impact on the building space. At the same time, the shape of these plates can be adjusted according to the bending moment gradient of the beam member in the vicinity of the column connection, to make it conform to the stress condition of the beam. This reduces the stresses at the interface of the beam-column connection and effectively moves the plastic hinge out of the end side of the column for the purpose.
2. Expanded flange reinforcement
Increase the width of the beam flange to increase the moment-carrying capacity of the beam member. The increased width size of the beam flange can be designed according to the moment demand of the seismic force, to achieve the strength design principle of reducing the stress demand at the column face and forcing the beam plastic hinge away from the column face. Cutting type expanded flange is suitable for welded H-beam, and welded expanded flange is suitable for hot-rolled H-beam. In terms of stress performance, the welded type is prone to residual stresses and deformation and is inferior to the cut type. This form of expanded flange may affect the local effect of the building.
3. Vertical single-ribbed plate reinforcement
This single-ribbed plate consists of three sections: the maximum reinforcement section, the circular section, and the extension section. The purpose of this design is to improve the stress concentration near the welded sector openings more effectively during earthquakes. The plastic deformation is distributed more evenly, thus improving the overall safety and seismic performance of the building structure.
4. Inside flange plate or stiffener plate reinforcement
For this kind of reinforcement, one kind of reinforcement plate is put on the side of the beam, and the other kind is put on two reinforcement plates on the same side. This type can be used not only for newly built steel structures, but also for already built steel structures, and the reinforcement construction is more feasible without affecting the building floor.
The above is the “strong node” of the four different ways, for specific projects, which is more appropriate, it depends on the designer’s choice.