The stiffness difference between the two directions of the structure should not be too large
- ① It is necessary to control the ratio of the first vibration period in the direction of the two main shafts, which can generally be controlled according to the period ratio of not less than 0.8.
- ② The displacement ratio exceeds the limit, and the bidirectional earthquake is not calculated.
- Irregular, especially irregular, seriously irregular: if the displacement ratio is greater than 1.2, the torsion is irregular, and the two-way earthquake should be calculated.
- ③ Considering torsional coupling, the displacement ratio should not exceed 1.5 when calculated according to two-way earthquake. If it exceeds 1.5, the structural layout should be readjusted.
The torsional displacement ratio is calculated under the assumption of rigid floor, and the actual stiffness shall be considered in the reinforcement calculation
Length width ratio control
When calculating the structure, each coefficient should be taken reasonably.
① The period reduction factor should be comprehensively determined according to different structural systems, types of infilled walls (considering possible changes) and the number of infilled walls. It should not be reduced or not reduced regardless of the actual situation for the convenience of reinforcement.
Article 3.3.17 of the high standard: when the infilled wall is a brick wall, the frame structure can take 0.6~0.7, the frame shear wall structure 0.7~0.8, and the shear wall structure 0.9~1.0 (attention should be paid to the short leg shear wall structure)
② The stiffness reduction factor of shear wall coupling beam shall ensure that the coupling beam will not crack under normal service conditions. If necessary, secondary calculation shall be carried out to avoid cracking of coupling beam under normal use.
Some components should not be reduced
When the computer calculates, the software reduces the torque of all components according to the input torque reduction coefficient. This will reduce the torque of the folded beam or curved beam with torque, and there are potential safety hazards in the structure. The torque of these components shall not be reduced. The coupling beam (folding beam) of the corner window shall take full account of the fact that the structural software cannot be reduced completely in accordance with the requirements of clause 4.1.2 of the load code. Components with large software reduction shall be manually rechecked.
In addition, attention should be paid to the following aspects:
① When calculating the wall, column and foundation of the structure connected by the main podium, the number of floors is wrong when calculating the reduction of the podium.
Special attention should be paid to this situation.
② In case of staggered floor structure or missing floors in the middle, when the calculated number of floors differs greatly from the actual number, it shall be calculated separately.
③ Special room load reduction.
It should be noted that when the floor height changes greatly (such as the equipment floor), the stiffness ratio and shear bearing capacity ratio of the weak layer of the structure meet the specification requirements
When the shear bearing capacity of the floor is lower than 80% of the upper layer, the weak layer shall be forcibly designated, and the shear bearing capacity ratio shall not be less than 65%. The floor cannot be both weak and weak
The calculated vibration mode number shall be guaranteed
Make the quality participation coefficient not less than 90%. (for complex structures such as steel structure roofs and open structures, the calculated vibration mode number of high-rise structures should not be less than 9; when considering torsional coupling, it should not be less than 15; multi tower structures should not be less than 9 times the number of towers.
Deflection and crack checking calculation shall be carried out for long-span simply supported secondary beams
Especially for beams with large span height ratio. It is required that the span height ratio should not be too large. In the calculation of long-span floor slab, the bearing constraints should be comprehensively considered, and the thickness, elevation and bearing reinforcement of adjacent slabs should be coordinated. The beam as the support shall be greater than twice the thickness of the plate.
For concrete frame tube structure, attention should be paid to improving the seismic capacity of the second line of defense
The 0.2Q0 internal force adjustment coefficient of the outer frame cannot be set to 2 times the maximum value, and should be taken according to the actual ratio. Ensure that the shear force borne by the outer frame is not less than the larger value of 20% of the bottom shear force and 1.5 times the maximum shear force of the calculated floor (note that this is not the smaller value of the two).
Stiffness
For the bottom frame structure, the stiffness ratio of the second floor to the first floor shall not be greater than 2.5 for 6 and 7 degrees, and 2.0 for 8 degrees. Should not be less than 1. For the two-story structure of the bottom frame, the stiffness of the lower two floors should be close. The stiffness ratio of the third floor and the second floor, 6 and 7, should not be greater than 2.0, 8 degrees 1.5. But it should not be less than 1.0. Shear walls should be arranged in both directions. The best result is to be close, and it is not good to be too large or too small. The stiffness is close, and the damage will not be concentrated on one floor. The main purpose is to reduce the weakness of the bottom and prevent the bottom structure from serious damage or even collapse due to excessive lateral displacement.
However, if there are too many concrete walls on the bottom floor, its stiffness may be greater than that of the upper brick concrete structure. In this way, the weak layer may be transferred to the transition layer under the earthquake. The transition layer is a masonry structure, which is less ductile than the reinforced concrete structure at the bottom, and is prone to brittle failure. Therefore, the lateral stiffness ratio of the transition layer and the bottom layer of the frame shear wall building on the ground floor should be controlled within a reasonable range. Pay attention to checking the effective length coefficient of columns layer by layer, especially when there is only cantilever beam in the other direction. The program often considers the cantilever beam as an ordinary frame beam, which leads to errors.