Does pure basement need earthquake force

1. 1 Understanding and application of the ratio of seismic force to seismic interlayer displacement

(1) code requirements: articles 3.4.2 and 3.4.3 of the code for seismic design and article 4.4.2 of the code for design of high rise buildings stipulate that the lateral stiffness of the floor should not be less than 70% of the lateral stiffness of the upper adjacent floor or 80% of the average lateral stiffness of the upper adjacent three floors< (2) calculation formula: ki = VI/ Δ UI

3 scope of application:

① it can be used to calculate the engineering stiffness ratio specified in article 3.4.2 and 3.4.3 of the code for seismic design and article 4.4.2 of the code for seismic design< It can be used to judge whether the basement roof can be used as the embedded end of the superstructure< (2) understanding and application of shear stiffness (1) code requirements:

Article e.0.1 of the code for design of high rise buildings stipulates that when the large space at the bottom is one floor, the equivalent shear stiffness ratio of the upper and lower structures of the transfer floor can be adopted approximately γ It represents the change of stiffness of upper and lower structure of transfer floor, γ It should be close to 1 in non seismic design γ It should not be more than 3. In seismic design γ It should not be greater than 2. See page 151 of the code for design of tall buildings for calculation formula< (2) article 6.1.14 of the code for seismic design stipulates that when the basement roof is used as the embedded part of the superstructure, the ratio of the lateral stiffness of the basement structure to that of the superstructure should not be less than 2. The calculation method of the lateral stiffness can adopt the shear stiffness according to the provisions. The calculation formula is shown on page 253 of seismic code< (2) the calculation method provided by SATWE software is the method provided by seismic code< (3) application scope: it can be used to calculate the stiffness ratio of the project specified in article e.0.1 of the code for design of high rise buildings and article 6.1.14 of the code for seismic design< (3) understanding and application of shear bending stiffness (1) code requirements:

Article e.0.2 of the code for design of high rise buildings stipulates that when the large space at the bottom is more than one floor, the equivalent lateral stiffness ratio of the upper part of the transfer floor to the lower part of the structure shall be calculated γ E can be calculated by formula (e.0.2) using the calculation model shown in Figure E. γ E should be close to 1 in non seismic design γ E should not be greater than 2, when seismic design γ E should not be greater than 1.3. For the calculation formula, see page 151 of the code for design of tall buildings< (2) article e.0.2 of the code also stipulates that when the transfer floor is set at three or more floors, the floor lateral stiffness ratio shall not be less than 60% of the adjacent upper floors< (2) calculation method adopted by SATWE software: simplified calculation of high lateral displacement stiffness

3) application scope: it can be used to calculate the stiffness ratio of Engineering specified in article e.0.2 of the code for design of tall buildings< (4) the main differences between the application scope of stiffness ratio in Shanghai code and national code are as follows:

(1) article 6.1.19 of Shanghai Code stipulates that the lateral stiffness of basement floor should not be less than 1.5 times of that of upper floor when the basement is used as the embedded end of superstructure< (2) the shear stiffness ratio has been used to calculate the three stiffness ratios in Shanghai code< (5) engineering example:

(1) project overview: a project is a frame supported shear wall structure, with 27 floors (including two floors of basement), and the sixth floor is a frame supported transfer floor. The three-dimensional axonometric drawing, the sixth and seventh floor plan of the structure are shown in Figure 1 (the figure is omitted). The seismic fortification intensity of the project is 8 degrees, and the design basic acceleration is 0.3g.

the calculation results of X-direction stiffness ratio of 1-13 floors:

e to the difficulty in listing, the meaning of each line of numbers below is as follows: the calculation method of three kinds of stiffness is separated by "/", the first section is the algorithm of seismic shear force and seismic interlayer displacement ratio, and the second section is shear stiffness, The third section is shear bending stiffness. The specific data are: layer number, RJX, ratx1, weak layer / RJX, ratx1, weak layer / RJX, ratx1, weak layer

where RJX is the lateral stiffness of the tower in the overall coordinate system of the structure (it should be multiplied by the 7th power of 10); Ratx1 is the smaller of the ratio of the lateral stiffness of the tower on this floor to 70% of the lateral stiffness of the corresponding tower on the upper floor or 80% of the average stiffness of the upper three floors. The specific data are as follows:

1, 7.8225, 2.3367, no / 13.204, 1.6408, no / 11.694, 1.9251, no

2, 4.7283, 3.9602, no / 11.444, 1.5127, no / 8.6776, 1.6336, no

3, 1.7251, 1.6527, no / 9.0995, 1.2496, no / 6.0967, 1.2598, no

4, 1.3407, 1.2595, no / 9.6348, 1.0726, No / 6.9007, 1.1557, no

5, 1.2304, 1.2556, no / 9.6348, 0.9018, yes / 6.9221, 0.9716, yes

6, 1.3433, 1.3534, no / 8.0373, 0.6439, yes / 4.3251, 0.4951, yes

7, 1.4179, 2.2177, no / 16.014, 1.3146, no / 11.145, 1.3066, no

8, 0.9138, 1.9275, no / 16.014, 1.3542, No / 11.247.1.3559, no

9, 0.6770, 1.7992, no / 14.782, 1.2500, no / 10.369, 1.2500, no

10, 0.5375, 1.7193, no / 14.782, 1.2500, no / 10.369, 1.2500, no

11, 0.4466, 1.6676, no / 14.782, 1.2500, no / 10.369, 1.2500, no

12, 0.3812, 1.6107, no / 14.782, 1.2500, No / 10.369, 1.2500, no 13, 0.3310, 1.5464, no / 14.782, 1.2500, no / 10.369, 1.2500, no

note 1: when SATWE software calculates "seismic shear force and seismic interlayer displacement ratio", fill in "0" in "relative stiffness ratio of backfill to basement restraint" in "basement information"

note 2: the number of weak layers and corresponding layer number are not defined separately in SATWE software

note 3: this example is mainly used to illustrate the realization process of the three stiffness ratios in SATWE software, and the rationality of the structural scheme is not discussed< (3) analysis of calculation results (1) the judgment results of weak layer are different when stiffness ratio is calculated by different methods

② in the "adjustment information" of SATWE software, the designer should specify the number of the sixth weak layer of the conversion layer. The designation of weak layer number does not affect the program's automatic judgment of other weak layers

③ when the transfer floor is set at three or more floors, the height regulation also stipulates that the lateral stiffness ratio of the floor should not be less than 60% of the adjacent upper floor. This SATWE software has no direct output results, so designers need to calculate the stiffness of each layer separately according to the program output. For example, the calculation results of this project are as follows:

1.3433 × 107／1.4179 × 107＝94.74％> 60%

meet the specification requirements< (4) whether the basement roof can be used as the embedded end of the superstructure:

A) the ratio of seismic shear force to seismic interlayer displacement

= 4.7283 × 107／1.7251 × The basement roof can be used as the embedded end of the superstructure

b) the shear stiffness ratio

= 11.444 × 107／9.0995 × (107) = 1.25 < 2

the roof of the basement can not be used as the embedded end of the superstructure

⑤ when SATWE software calculates the shear bending stiffness, the value range of H1 includes the height of the basement, and the height of H2 is equal to or less than H1. For the designers who want the value of H1 to be taken from 0.00 or above, or remove the basement and recalculate the shear bending stiffness, or manually calculate the stiffness ratio according to the shear bending stiffness output by the program. Taking the project as an example, H1 is calculated from 0.00, using the stiffness string model, the calculation results are as follows:

the floor number of the transfer floor is 6 (including basement), the starting and ending floor number of the lower part of the transfer floor is 3-6, H1 = 21.9m, the starting and ending floor number of the upper part of the transfer floor is 7-13, h2 = 21.0m.

K1 = [1 / (1 / 6.0967 + 1 / 6.9007 + 1 / 6.9221 + 1 / 4.3251)] × 107=1.4607 × 107

K2=[1/1/11.145+1/11.247+1/10.369 × 107=1.5132 × 107

Δ 1=1/K1 Δ 2 = 1 / K2

then shear bending stiffness ratio γ e= Δ one × H2/ Δ two × (6) discussion on the properties of three kinds of stiffness ratio

(1) ratio of seismic shear force to seismic interlayer displacement: a calculation method related to external force. Specified in the specification Δ UI includes not only the displacement caused by seismic force, but also the displacement caused by overturning moment Mi of the floor and the rigid body rotation displacement of the floor caused by the rotation of the next floor< (2) shear stiffness: the calculation method is mainly the ratio of shear area to the corresponding storey height, which is closely related to the shear area and storey height of vertical members. However, the shear stiffness does not consider the influence of the structural system with braces and the height of shear wall openings< (3) shear bending stiffness: actually, it is the interlayer displacement angle under the action of unit force, and its stiffness ratio is also the ratio of interlayer displacement angle. It can consider the influence of shear deformation and bending deformation at the same time, but does not consider the constraints of upper and lower layers

the properties of the three kinds of stiffness are completely different, and there is no necessary connection between them. Because of this, the code gives them different scope of application.

2. Unknown_Error

3. Generally, the basement is a part of the building, and the seismic grade of the building should be the seismic grade of the basement.

4. Should the flat slab floor of basement be considered as seismic action?
flat slab floor: the slab floor is directly supported on columns without beams, which is mostly used in exhibition halls, shops, warehouses and other buildings with large floor load. It is a plate column structure with two-way force. In real life, buildings with seismic requirements do not use beamless floor. Because it's not good for earthquake resistance
in order to improve the punching capacity of the slab at the top of the column, the column cap is often set at the top of the column. Columns are set in the middle of the slab span to rece the slab span. For the slab without beams, the column top structure can be divided into two types: column cap and no column cap.

5. Should the pure basement without superstructure be aseismic designed in earthquake area? This problem has been clearly stated in the original code. For example, article 6.1.3 (3) of code for seismic design of buildings (GB 50010-2002) stipulates that "... For the part without superstructure in the basement, grade 3 or lower can be adopted according to the specific situation", Article 4.8.5 of technical specification for concrete structures of high rise buildings JGJ 3-2002 also stipulates that "... The seismic grade of the part of the basement beyond the scope of the upper main building and without the upper structure can be grade 3 or grade 4 according to the specific situation. In the 9-degree seismic design, the seismic grade of basement structure should not be lower than grade II. " As we all know, when an earthquake occurs, the seismic action (energy) is transmitted by the ground in the form of seismic wave, not by the air. There will be damage phenomena under the surface, such as "landslide, collapse, liquefaction (sandblasting), seismic subsidence" and surface tearing, which indicates that there is still seismic damage under the surface, so the foundation engineering will also be damaged.

6. When calculating the internal force, accidental eccentricity does not need to be considered, but PKPM should be able to automatically judge this point, and the reinforcement calculation results will not be affected at this point. Bidirectional seismic force will obviously affect the calculation of internal force. According to the code, the structure with "obviously asymmetric distribution of mass and stiffness" (article 5.1.1 of code for seismic design (GB 50011-2010)) needs to be considered. It is generally considered that if the displacement ratio is greater than a certain degree (usually controlled above 1.3), it should be considered. You should consider the details yourself. In a word, if there is no special stingy requirement for the cost, it is always safe for designers. Foundation? First of all, not all building foundations need to consider seismic action. For details, please refer to Article 4.2.1 and 4.4.1 of code for seismic design (GB 50011-2010). If the seismic action needs to be considered, check the seismic load when the foundation reads the load, otherwise it can not be selected. As for accidental eccentricity and bidirectional seismic force, the upper part shall prevail.

7. 1. It's not just about power
for example, dead load and live load are vertical, which will proce bending moment at the beam end,
wind load and seismic action are horizontal, but they will also proce bending moment at the beam end,
so the two should be combined
2. In this case, you need to compare the bending moment diagram generated by horizontal load with that generated by vertical load, and the same direction is positive
3. I can't understand this. I suggest you make the whole topic up.

8. The basement is not shockproof. It's dangerous! 1. Hide in the basement, once the house collapses, it will be buried deep underground, and it is not easy to be rescued. 2. Hide in the basement, once the ground water rises after the earthquake (very common), there is no place to hide

9.

Refer to Article 4.2.1 of the code: