1, A: (1) bearing scheme of transverse frame; Advantages: the number of lateral frames is small, which is beneficial to increase the lateral stiffness of buildings; The small cross-section size of longitudinal coupling beam is beneficial to ventilation and lighting of buildings. Disadvantages: the cross-section size of the main girder is large, which increases the structural height.
(2) Bearing scheme of longitudinal frame; Advantages: it is suitable for large-space residence, with large clearance and flexible apartment type. Disadvantages: the depth dimension is limited by the length of the slab, and the lateral stiffness of the building is small.
(3) Hybrid bearing scheme of vertical and horizontal frames. Advantages: uniform stress on each bar and good overall performance;
2. What are the advantages of the framework system? Explain its scope of application.
2. Answer: The advantages of the frame structure system are: the integrity and seismic performance are better than those of the mixed structure, and the plane layout is flexible, which can provide more use space and form a rich and varied facade shape. Scope of application: widely used in industrial workshops and public buildings.
3. What are the design steps of the frame structure?
3. Answer: (1), structural plane layout; (2) Determination of column network and height; (3) Determination of bearing scheme (4) Load calculation; (5) Calculation of internal force and displacement; (6) reinforcement calculation; (7), steel bar selection; (8), draw the structure construction drawing.
4. How to determine the column grid size?
4. Answer: The column net of frame structure should meet the use requirements of buildings, and the specifications and models of components should be less. Column spacing should not be less than 3.6m, and should not be greater than 6.0m. According to the application requirements, the spans of columns are 2.4m, 2.7m, 3.0m, 5.8m, 7.5m, 8.0m and12.0m..
5. How to determine the section size of frame beams and columns?
5. Answer: The section size of the frame beam (1) should meet the rigidity requirements; (2) meet the structural requirements; (3) Meet the bearing capacity requirements.
The section size of frame column (1) should meet the stability requirements; (2) meet the structural requirements; (3) Meet the bearing capacity requirements.
6. How to calculate the internal force and lateral displacement of the frame under horizontal load?
6. Answer: The calculation methods of frame internal force under horizontal load are the reverse bending point method and the D value method. The concrete calculation steps are as follows: determining the position of the reverse bending point; Determination of lateral stiffness of column; Distribution of shear force of each column; Calculation of bending moment at column end; Calculation of bending moment at beam end; Shear force calculation of beam.
The calculation of lateral displacement under horizontal load can be considered as the superposition of lateral displacement caused by bending deformation of beams and columns and axial deformation of columns.
7. What are the calculation points of the modified reverse bending point method (D-value method)?
7. A: The calculation points of the modified reverse bending point method (D value method) are: 1) to correct the lateral stiffness of the column; 2) Modify the stiffness of the bending point; 3) Shear distribution of columns; 4) Calculation of bending moment at column end; 5) Calculation of beam end bending moment; 6) Shear calculation of beam.
8. How to calculate the internal force of the frame under gravity load?
8. Answer: Calculation of internal force of frame under gravity load: Gravity load belongs to vertical load. Multi-layer frame is layered, and the frame composed of beams and upper and lower columns of each layer is used as the calculation unit. According to the calculation of frames without lateral displacement, moment distribution method or iterative method is generally used.
9. What are the calculation points of the secondary distribution method of bending moment?
9. Secondary distribution method of bending moment: 1) Find the bending moment at the fixed end; 2) Find the distribution coefficient and transfer coefficient; 3) distributing and transferring the bending moment twice; 4) Find the bending moment at the beam end.
10. What is the control section of beam and column, and how to determine the unfavorable combination of internal forces of the control section? 1 1. What is a one-way slab? What are the characteristics of its stress and reinforcement structure?
10, the control section of the beam is near the midspan (maximum positive bending moment section) and the intersection of the beam and the column (maximum negative bending moment section).
The control section of the column is at the bottom of the beam (the upper end of the column) and the top of the beam (the lower end of the column), that is, the section with the greatest axial pressure.
Control the unfavorable combination of internal force of section: the arrangement method of vertical load includes the combination method of step-by-step loading; The most unfavorable load position method; Full load method. Different arrangements will produce different internal forces, which are determined by the most unfavorable arrangement. Arrangement method of horizontal loads (wind load and earthquake load): In rectangular plane structure, the internal forces under positive and negative loads are equal in magnitude and opposite in sign, so the positive and negative signs can be added to the internal forces only once.
1 1. What is a one-way slab? What are the characteristics of its stress and reinforcement structure? 1 1, one-way slab: refers to the case where the ratio of the long side to the short side of the slab is greater than 3. The mechanical characteristic is that the load of the plate is mainly transmitted along the short side direction, while the load transmitted along the long side direction is very small and can be ignored. Structural characteristics of steel bars: There are bending reinforcement and separation reinforcement in the slab. General reinforcement is HPB235 grade, with diameters of 6mm, 8mm and 10mm, and the spacing should meet the structural requirements. Structural reinforcement includes distributed reinforcement and additional reinforcement at the top of the slab.
12. What is a two-way board? What are the characteristics of its stress and reinforcement structure? .
12. Two-way board: refers to the case that the ratio of the long side to the short side of the board is less than or equal to 2. The stress characteristic is that the load on the plate is transmitted along the short side and the long side. The structural characteristics of steel bars are: the stressed steel bars of the plate are arranged in two directions respectively, and the arrangement mode of steel bars is bending and separation. Additional reinforcement in two directions shall be provided at the top of the slab.
13. What's the difference between slab stairs and beam slab stairs? What kind of stairs do you design?
13. Slab staircase: it is a sloping slab with two ends supported on the platform beam. The steps of slab stairs are reinforced with inclined beams; When the inclined slab is thick and the span is large, the material consumption is large, and the slab staircase is complete, light and beautiful.
Beam staircase: an inclined beam is arranged on one side of the inclined plate of the staircase, and the tread plate is supported on the inclined beam, and then the inclined beam is supported on the platform beam. The ladder is economical when it is long, but the construction is complicated and the appearance is heavy.
14. What's the difference between step calculation and structure of slab stairs and beam-slab stairs?
14, slab stair tread is calculated as simply supported inclined slab. The upper part of the inclined plate of the structure should be equipped with an appropriate amount of reinforcement, in order to bend the reinforcement, the reinforcement in the middle of the span should be bent at a quarter of the clear distance from the edge of the bearing. It can also be reinforced separately. The steel bars distributed in the pedals should be on the inner side of the stressed steel bars, and generally one should be set under each pedal.
The tread plate of beam stairs is calculated as a one-way slab with both ends obliquely supported on the inclined beam, and the tread height is determined by the structure. The calculation of tread plate is a special trapezoidal cross-section. Generally, one tread is cut vertically and calculated as simply supported vertically. The reinforcement of the tread plate shall be determined according to the calculation, and the reinforcement of each step shall be no less than 2φ6, and the φ6 distributed reinforcement with a spacing of not more than 300mm shall be arranged along the width direction of the step.
15. What are the failure characteristics of beams with few tendons, beams with suitable tendons and beams with super tendons? How to prevent the beam from being short of tendons and more tendons in design?
15. failure characteristics of beams with less reinforcement: with the cracking of concrete in tension area, the reinforcement yields or even breaks. The failure of less reinforcement belongs to brittle failure.
Failure characteristics of beams with appropriate reinforcement: when the reinforcement amount is appropriate, the concrete in the tensile area cracks, and with the increase of load, the steel bars yield, the load further increases, and the concrete in the compression area is crushed and destroyed. It belongs to ductile failure.
The failure characteristics of super-reinforced beams: due to the large amount of steel bars, the steel bars have not yet yielded, and the concrete in the compression area has been crushed and destroyed. It belongs to brittle failure.
According to ξ≤ξb design, to prevent damage to tendons; Press ρ≥ρmin to prevent minor damage to steel bars.
16. What are the failure forms of inclined sections in flexural members? What are their characteristics?
16. The failure forms of oblique section are: 1) oblique compression failure, which is characterized by: when the shear span ratio is small and the amount of web reinforcement is large, with the increase of load, many oblique cracks appear near the beam end, which are crushed like short columns when damaged, and stirrups generally do not yield at this time. ; 2) Shear-compression failure: when the shear-span ratio is moderate and the web reinforcement is appropriate, the main oblique crack first appears in the shear-bending area of the beam. With the increase of load, the main oblique crack extends, and the concrete in the compression area collapses under the combined action of normal stress and shear stress, and the stirrup also yields. ; 3) Cable-stayed failure, which is characterized by large shear-span ratio and small stirrup consumption, will soon expand up and down once the oblique cracks appear, and then split the beam into two parts and destroy it. (Take a beam with web reinforcement as an example)
17. What is a waist tendon? What is its function?
17. Waist tendon: When the beam height h > 700 mm, a waist tendon with a diameter of not less than 10mm should be set on both sides of the beam at intervals of 300 ~ 400 mm along the beam height, and connected with lacing, and the spacing of lacing is generally twice that of stirrups.
Function: To prevent vertical cracks caused by concrete shrinkage and temperature deformation when the beam is too high, and also to strengthen the rigidity of steel skeleton.
18. Why should the spacing s between stirrups and bent steel bars meet certain requirements?
18, the spacing between stirrups and bent steel bars in the beam should not be too large, so as to avoid oblique cracks between stirrups or bent steel bars, thus reducing the shear bearing capacity of the beam. Therefore, the maximum spacing s should meet the specification requirements.
19, what are the basic elements of architecture?
19. The basic elements of architecture are: (1) Architectural function: it is the most important of the three elements. Architectural function is the comprehensive embodiment of people's specific purpose and use requirements when building houses. (2) The materials and technical conditions of the building are important factors that constitute the building. (3) The artistic image of architecture is reflected by its combination of plane space, architectural modeling and elevation, color and texture of materials, and detailed treatment and depiction.
20. Structural composition of civil buildings: it consists of foundation, wall or column, floor, stairs, roof, floor, doors and windows.