2. According to the Technical Specification for Waterproofing of Underground Engineering (GB50108-2001), the concrete cushion of waterproof concrete floor of underground engineering should not be less than C 15, 100 mm, and the soft soil should not be less than 150mm, which is waterproof.
3. The protective layer thickness of waterproof concrete reinforcement near the water surface of underground engineering is required to be not less than 50mm in Technical Specification for Waterproofing of Underground Engineering (GB50108-2001), and the crack width is calculated, which is not more than 0.2mm and should not be penetrated. Many designers adjust the bending distance of basement waterproof structural members in the design, some are hinged at the lower end, some do not consider the unbalanced load coefficient, and many floors are not calculated according to multi-span continuity, and cracks are not calculated, which leads to the violation of strong bars.
4. The connection structure between the basement exterior wall and the floor is unreasonable; The lap joint of external wall reinforcement does not meet the requirements of Code for Design of Concrete Structures (GB500 10—2002), so the lap joint length shall be corrected according to the percentage of the lap joint area of longitudinal reinforcement. 5. The basement exterior wall design should consider the calculation and design of exterior walls with different supporting conditions such as stairwells and driveways, which cannot be the same as general exterior walls. When the roof is not at the same elevation, attention should be paid to the transfer of horizontal force of the upper support of the external wall. 6. When the groundwater level is high, special attention should be paid to the anti-floating calculation of only the basement part and a few floors on the ground, and the uplift bearing capacity of the pile should be calculated when the pile foundation is adopted. {HotTag} 7。 When using independent column foundation or strip foundation with waterproof floor in high-rise basement, mattress should be set under waterproof floor to ensure the actual stress is the same as the design calculation model. 8. For buildings with Class A and Class B foundations, the foundation deformation design shall be carried out according to Article 3.0.2 of Code for Design of Building Foundations (GB 50007—2002).
9. Check the settlement of the pile foundation of the following buildings: (strong steel bar)
1) Building pile foundation, the foundation design level is Grade A. ..
2) The pile foundation of a building with complex shape, uneven load or soft soil layer below the pile tip and design grade B. ..
3) Friction pile foundation. The settlement of pile foundation shall not exceed the allowable value of building settlement, and shall comply with the provisions in Table 5.3.4 of Code for Design of Building Foundation (GB 50007—2002).
10. Designers generally pay insufficient attention to the deformation observation requirements of buildings during construction and use. Engineering scope of deformation observation According to the article 10.2.9 (strong article) of Code for Design of Building Foundation (GB 50007—2002), deformation observation should be carried out for the following buildings during construction and use. A. Buildings with Grade A foundation design;
B. Buildings with design grade B on composite foundation or soft foundation;
C. adding stories to expand the building;
D buildings affected by the excavation of adjacent deep foundation pits or the change of environmental factors such as groundwater;
E. Projects that need to accumulate architectural experience or carry out design back analysis. The observation methods and requirements shall conform to the national industry standard Code for Deformation Measurement of Buildings (JGJ/T 8-97).
1 1. settlement joint foundation and eccentric foundation: the settlement joint foundation of masonry structure is made in the following form: according to the principle of force balance, most foundations have zero pressure zone, and the designed foundation cannot provide the foundation bearing capacity required for design. Many eccentric column foundations with column edges aligned with the foundation also have problems. The zero stress zone can not meet the requirements of Article 4.2.4 of Code for Seismic Design of Buildings (GB 5001-2001).
12. When cement mortar is used for the wall below the moistureproof layer, attention should be paid to checking its strength. (Because the strength of cement mortar decreases).
13. The height of column foundation of individual projects does not meet the requirements of anchorage length of column longitudinal reinforcement. The punching shear bearing capacity of column foundation is not enough.
14. The intersection point of strip foundation under the wall should not be included in the foundation area repeatedly.
15. The basement of masonry structure. (240)
16. The bearing capacity of foundation shall be the characteristic value. In foundation design, the most unfavorable combination of load effects and the corresponding resistance limits are as follows: (Article 3.0.4 of Technical Specification for Building Foundation Treatment)
A. When determining the area and buried depth of the foundation bottom according to the bearing capacity of the foundation or determining the number of piles according to the bearing capacity of a single pile, the load effect transmitted to the foundation bottom or pile cap shall be the standard combination of its corresponding load effects according to the normal service limit. The corresponding resistance should adopt the characteristic value of foundation bearing capacity or the characteristic value of single pile bearing capacity.
B. When calculating the deformation of foundation, the load effect transmitted to the bottom of foundation should be based on the quasi-permanent combination of load effects under the normal service limit state, and should not be included in the wind load and earthquake action. The corresponding limit value should be the allowable value of foundation deformation.
C. When calculating the earth pressure of retaining wall, the stability of foundation or slope and the landslide thrust, the load effect should be based on the basic combination of load effects under the limit state of bearing capacity, but its partial coefficients are all1.0.d. When determining the height of foundation or pile platform, the section of retaining structure, calculating the internal force of foundation or retaining structure, determining the reinforcement and checking the material strength, the load effect from the superstructure and the corresponding base reaction force should be based on the load effect under the limit state of bearing capacity.
17. Can the basement wall be used as the support of the raft? This problem exists in both brick-concrete and concrete structures.
18. The hole of the basement wall door (window) should be calculated and set according to the foundation beam.
19. area of zero stress zone of foundation: for high-rise buildings with aspect ratio greater than 4, tensile stress should not appear at the bottom of foundation under earthquake; For other buildings, the area of zero stress zone between foundation bottom and foundation soil should not exceed 15% of the area of foundation bottom. Special attention should be paid when designing light steel structures.
20. When the basement roof is used as the embedded part of the upper part of the reinforced concrete structure building, the flat floor structure cannot be adopted.
2 1. Whether the number of frame support stories in the basement is included in the code: If the basement roof is used as the embedded part of the superstructure, the number of frame support stories in the basement is not included in the code.
22. When determining the seismic grade of the building, how to determine the height of the building if the basement roof is not used as the burial point of the upper building? From the outdoor ground or from the foundation? When determining the seismic grade of a building, the height of the building is calculated from the outdoor ground.
23. The use of pile foundation (including mixing pile) in the site cannot change the category of the site.
24. The lap joint problem of basement floor reinforcement and foundation beam reinforcement.
25. When calculating the bending moment and shear force of basement exterior wall, the effect caused by earth pressure should be permanent load effect. When considering the combination of variable load effect control, the partial coefficient of earth pressure load is1.2; When considering the combination controlled by the permanent load effect, the partial load coefficient is 1.35. The earth pressure of the basement exterior wall should be static earth pressure. For the live load on the ground, it should also be multiplied by the lateral pressure coefficient. Many designs are not calculated correctly in the design.
26. When calculating the strength of basement floor (the water level is high, and the total vertical load is upward) (the pile foundation is different), the partial coefficient of the slab weight and the load of the covering soil is 1.2, which is wrong. According to Article 3.2.5 of Code for Load of Building Structures (GB 50009-2001+0), the partial load coefficient should be 65438.