In general, it should be allowed to calculate the horizontal earthquake action in the two main axis directions of the building structure and carry out the seismic check calculation. The horizontal earthquake action in each direction should be borne by the lateral force-resistant members in that direction. For structures with obliquely-crossed lateral force-resistant members, when the intersection angle is greater than 15°, the horizontal seismic action in the direction of each lateral force-resistant member shall be calculated separately.
For space frame structures with significantly asymmetrical mass and stiffness, the torsional effect under the action of a bidirectional horizontal earthquake should be included.
In other cases, the method of adjusting the seismic effect should be allowed to be included in the torsional impact. For large-span and long cantilever structures in seismic fortification of 8 and 9 degrees, vertical seismic action should be calculated. The support conditions of the space frame structure can be assumed to be hinged supports or elastic supports that can be moved laterally in two directions, laterally in one direction, and without lateral displacement according to the rigidity of the support structure and the structure of the support nodes.