According to the conceptual design of the structure, determine the structural materials, structural system, layout and construction methods; Structural analysis and design (including calculation diagram, internal force, deformation analysis and reinforcement calculation, etc. ), structural design; Draw structural construction drawings (including structural layout, final displacement of components and reinforcement diagram, etc.). )
1.2 How many forms of reinforced commercial concrete beam-slab structure are there? How are they divided?
The beam-slab structure composed of one-way slabs is called one-way slab beam-slab structure, and the beam-slab structure composed of two-way slabs is called two-way slab beam-slab structure. When L2/l 1
1.3 How is the load transferred in the slab, secondary beam and main beam of the integral one-way slab structure, and why? What is the difference between the calculation diagrams of elastic theory and plastic theory?
One-way slab is supported by secondary beam, secondary beam is supported by main beam and main beam is supported by column and wall. The load acting on the structure is first transmitted from the one-way slab to the secondary beam, then to the main beam, and finally to the column and wall by the main beam. In order to reduce the span of the whole one-way slab beam-slab structure, secondary beams, main beams, columns or walls should be set up to reduce the span of the main beams. The calculation diagrams of the two are different in the span of structural calculation.
1.4 how to determine the most unfavorable position of live load when it is necessary to calculate the most dangerous internal force of structural span and load-bearing section in the integral beam-slab structure?
(1) If the maximum positive bending moment of the internal section of a span is required, in addition to the dead load, live loads should be arranged in the span, and then live loads should be arranged on both sides of the span. (2) If the maximum negative bending moment of the internal section of a span is required, in addition to the dead load, live loads should not be arranged in the span, but on both sides of the span. (3) If the maximum negative bending moment of a load-bearing section of the structure is required, then the live load is arranged on both sides of the span (4). In order to obtain the maximum shear force of the lateral support section of the structure, except for the dead load, the live load arrangement is the same as that of the section with the largest positive bending moment in the span. When calculating the maximum shear force of the load-bearing section in the middle span of the structure, the live load arrangement is the same as when calculating the maximum negative bending moment of the load-bearing section.
1-5 the connecting line or trajectory of the maximum internal force value of each section of the structure is the internal force envelope diagram of the structure.
If there is only one set of loads on the structure and only one set of internal forces on each section of the structure, the internal force diagram is the internal force envelope diagram. If there are several groups of loads acting on the structure at different times, and there are several groups of internal forces in each section of the structure, the structure has several groups of internal force diagrams, such as bending moment diagram and shear force diagram.
1-6 What is a structural material drawing? What will happen to the material drawing of the structure when the longitudinal reinforcement is bent and closed?
The trajectory of the connection point of the bearing capacity of each section of the structure is the internal resistance diagram of the structure, or the material diagram. 1-7 What is a plastic hinge? What's the difference between it and an ideal hinge?
Under the condition of keeping a certain value of bending moment, the section rotates greatly, just like forming a "hinge". The plastic deformation when the material rotates records the performance of cracks in commercial concrete, so it is called plastic hinge.
An ideal hinge can't transmit bending moment, but it can rotate infinitely, while a plastic hinge can transmit a certain value of plastic bending moment, and it will rotate limited under the action of plastic bending moment. When the rotation range of the plastic hinge exceeds the plastic limit rotation angle, the plastic hinge will be destroyed due to the exhaustion of plastic capacity.
1-8 What is the ultimate state of bearing capacity of a structure? Is it an example?
Remaining full text
There are plastic hinges in the statically indeterminate structure of commercial concrete, and the statically indeterminate structure only reduces one redundant constraint, which not only reduces the statically indeterminate structure once, but also can continue to bear the load. Only when there are multiple plastic hinges in the structure, and when the whole or part of the structure becomes a geometrically variable system, the structure will reach the limit state of bearing capacity.
1-9 What is the plastic internal force redistribution of a structure? What is the relationship between the position of plastic hinge and the value of plastic bending moment and the redistribution of plastic internal force? Try to explain with examples why steel bars can be saved when designing beams and plates according to plastic internal force redistribution method.
The change of structural internal force distribution law relative to elastic internal force distribution is called internal force redistribution.
When the plastic hinge appears on the support B, the mid-span bending moment is m 1, 2, and the bending moment is m 1, 2 =1.15f' l0 = 0.1/7fl0.
1- 10 What is torque amplitude modulation? In the analysis method considering the redistribution of plastic internal forces, why should the investigation scope of plastic hinge bending moment be limited?
The adjustment range of bending moment refers to the difference between the bending moment value obtained according to elastic theory and the absolute value of bending moment at plastic hinge. If the moment amplitude modulation coefficient β is positive, it belongs to the situation that the moment value of section decreases, which will lead to the increase of crack width and structural deformation of commercial concrete, and the degree of increase will increase with the increase of moment adjustment, so adjust the moment adjustment.
1- 1 1 How to increase the rotation ability of plastic hinges? Which of these measures is the most effective?
In order to ensure that the plastic hinge has enough rotation ability, that is, the plastic angle has a large plastic limit rotation height, the steel bar is required to have good plasticity, and the commercial concrete has a large ultimate compressive stress value. Therefore, the engineering structure should adopt HPB235, HRB335 grade steel bars and low-grade commercial concrete. The rotation range of plastic angle is related to the adjustment range of bending moment at plastic hinge, and it is suggested that the adjustment range of bending moment β is ≤20%. For the structure with the ratio of live load Q to dead load G Q/G ≤ 1/3, the adjustment range of bending moment should be controlled at β≤35%. The research shows that increasing the cross-section height and decreasing the cross-section relative compression zone height are effective measures to improve the rotation ability of plastic hinge. What are the basic assumptions for calculating the internal forces of two-way slabs? The most dangerous internal force for calculating the control section of two-way slab is how to arrange the live load. How to break down the load? How to determine the supporting conditions?
When the two-way slab reaches the limit state of bearing capacity, a plastic hinge line is formed at the maximum bending moment under load, and the whole slab is divided into several slabs to form a geometrically variable system.
2. The plastic stranded wire is a straight line under the action of bidirectional vehicle-mounted uniform load, and its position is related to the shape, size, boundary conditions, load, form and reinforcement amount of the plate.
3. The elastic deformation of the two-way slab is smaller than that of the plastic steel strand, so it is regarded as a rigid body, and the overall deformation is concentrated on the plastic steel strand. When the plate reaches the limit state of bearing capacity, all the blocks rotate around the plastic stranded wire.
4. There are many groups of possibilities for the location of plastic hinge line of two-way slab satisfying geometric conditions and equilibrium conditions, but there must be a group of most dangerous failure modes of structural plastic hinge line with minimum ultimate load.
5。 When the plastic stranded wire is loaded on the slab in two directions, the steel bar reaches the yield point, the commercial concrete reaches the tensile and compressive strength, and the section has a certain plastic bending moment.
In order to obtain the maximum bending moment of grid section in two directions, besides dead load, live load should be arranged in the grid. In order to make the bi-directional deformation curve of the grid in area A become the largest curve library, all downward bending deformation areas are loaded, and the * * * live load is arranged in a chessboard shape. In order to make use of the internal force and deformation number of two-way slab in a single grid, the live load of chessboard layout should be decomposed into symmetric load q/2 and grid-filled areas in each area.
Under the action of symmetric load G' = G+Q/2, for the outer boundary supporting conditions of side grids and corner grids, according to the actual situation, if the corner grid is supported on the wall, it can be simplified as hinged support, then the corner grid is regarded as a two-way slab with two fixed supports at the outer edge and two fixed supports at the outer edge, and the rest grids are regarded as two-way slabs with three fixed sides and one shear support.
Under the action of anti-symmetric force load G ′ = q/2, the additional boundary support conditions of boundary elements and corner regions are determined according to the actual situation. If the plate is supported on the wall, it is regarded as hinged support, then all units are simply supported two-way plates.
1- 13 what's the difference between the empirical coefficient method and the equivalent frame method when analyzing the internal force of the whole beamless floor structure according to the elastic theory? How to design the bolt cap?
When analyzing the internal force of the whole flat floor structure, the empirical coefficient method is used when the structure has no lateral displacement, and the frame method is used when the structure has reverse displacement. The punching load force of integral lifting with bolt cap is set as no beam, and the bending moment of plate span, support and section is reduced at the same time.
1- 14 What is the importance of the connection between plates, plates and bearing transverse walls, and plates and longitudinal walls? Commercial concrete grouting between precast slabs, and the connection between slabs and walls will connect the slabs into a whole, which will play the role of transferring horizontal shear force. The connection between the floor and the longitudinal wall will support the longitudinal wall, transfer horizontal pressure and tension, and ensure the vertical stability of the longitudinal wall.
2- 1 What does the structural design of a single-storey factory building include? Briefly describe the main contents and design principles of structural scheme design?
Structural design can be divided into structural scheme design, structural analysis, component section reinforcement calculation and structural measures. Structural scheme design includes determining structural type and system, component modeling and structural arrangement. Reliable principle, reasonable economy and technology. 2-3 What supports should be provided for the single-storey factory building with assembled reinforced commercial concrete bent structure? Briefly describe the functions and setting principles of these supports.
Single-storey factory buildings are supported by roofs and columns, in which roof supports include upper and lower chord horizontal supports and longitudinal horizontal supports. Vertical support and longitudinal horizontal tie rod, skylight beam, etc. The horizontal support of the upper chord is to ensure the stability of the upper chord of the roof truss out of the plane and the longitudinal horizontal stiffness of the roof, and also serves as the horizontal support of the top of the gable wind-resistant column, which is not affected by the wind load and longitudinal horizontal load from the gable. The lateral horizontal brace of the lower chord is used to transfer the gable wind load and longitudinal horizontal load to the longitudinal column, and at the same time prevent the lateral vibration of the lower chord of the roof truss. The function of vertical support is to ensure the out-of-plane stability of roof truss after bearing load and transmit longitudinal horizontal force. The upper chord tie rod ensures the lateral stability of the compressed flange of the upper chord of the roof truss, and the lower chord horizontal tie rod can prevent the lower chord of the roof truss from generating lateral vibration when other crane types vibrate horizontally. Skylight pole support is used to ensure the lateral stability of the top chord of the skylight beam and transfer the wind load on the end wall of the skylight to the roof truss. The gable supported between columns bears the transmission of wind-resistant columns and roof horizontal supports, and cracks the longitudinal horizontal earthquake from the roof structure and the longitudinal horizontal braking force from the crane beam, which are transmitted to the foundation.
2-4. What requirements should be met for the connection between wind-resistant column and roof truss? What are the functions of coupling beam, ring beam and foundation beam? How are they connected to the pillars?
Meet two requirements: first, it must be reliably connected with the roof truss in the horizontal direction to ensure the effective transmission of wind load; Secondly, they should be allowed to have a certain relative displacement in the vertical direction to prevent the adverse effects caused by the uneven settlement of wind-resistant columns and roof trusses. The function of ring beam is to hoop the wall, bent column and wind-resistant column together, so as to enhance the overall stiffness of the factory building and prevent the lower floor from being adversely affected by uneven settlement of foundation or large vibration load.
The coupling beam not only bears the load of the wall, but also plays the role of connecting the longitudinal columns, enhancing the longitudinal stiffness of the factory building and transmitting the longitudinal horizontal load. The foundation beam of the external wall can be settled with the column.
2-5. What assumptions were made when determining the bent structure of a single-storey factory building as shown in the figure? Try to analyze the rationality and applicable conditions of these assumptions.
(1) The lower braid of the column is embedded in the foundation, and the fixed end is located on the top surface of the foundation.
When the soil quality of the factory building foundation is poor, the deformation is large or there is a large area of ground load, the influence of the internal force of the bent frame when the foundation rotates and displaces should be considered.
(2) The top of the column is hinged with the top beam of the roof truss, which can only transmit the vertical axial force and horizontal shear force, and does not transmit the bending moment, so the ability to resist rotation is very small. Therefore, the connection between the column top and the roof truss can be considered as hinged.
(3) The cross beam is a rigid connecting rod with high axial stiffness.
The beam adopts a composite roof truss with lower chord stiffness or a double hinged arch with tie rods. When the roof truss has three hinges, the lateral displacement of the columns at both ends of the beam is not equal because of its large axial deformation. Therefore, the beam should not be assumed as a rigid member when calculating the internal force of bent, and the influence of axial deformation of beam on the internal force of bent should be considered.
2-6. What are the loads acting on the transverse plane bent? How to determine the position of these loads? Try to draw the calculation diagram of bent structure under each single load.
Loads acting on the transverse bent structure include dead load, convertible top load, snow load, dust load, crane load and wind load, which are omitted from the drawing.
2-7. How to calculate the crane load Dmax(Dmin) and the crane load Tmax acting on the bent?
Because the crane load is a moving load, it is necessary to use the influence line principle to find the maximum bearing reaction force of the crane beam, that is, the vertical load Dmax or Dmin of the crane. The maximum reaction force is the reaction force when one of the two cranes runs in parallel and the maximum wheel pressure Fpi max is just outside the axis of the bent column. Dmax=∑Fpi maxyi
2-8. What is contour bending? How to calculate the internal force of contour bending by shear distribution method? Try to describe the calculation steps of internal force of contour bending under arbitrary load.
Contour bent refers to the bent with equal lateral displacement at the top of each column under load.
Shear distribution method: Vi=niF, shear force of each column = shear force F× shear distribution coefficient ni=
2-9. What is the spatial function of a single-storey factory building? What are the factors that affect the spatial function of a single-storey factory building? What is the effect of considering the spatial action on the internal force of the column?
The interaction between bent and bent, bent and gable is called the overall spatial function of the factory building.
The spatial function of a single-storey factory building mainly depends on the roof stiffness, gable stiffness, gable spacing, load type and other factors. When the horizontal concentrated force R acts on the column top of a truss, the horizontal concentrated force R is not only borne by the direct load bent, but also connected with other adjacent bent frames through the longitudinal connection such as the roof, so that the whole plant bears the same burden.
2- 10. which control sections should be selected for the internal force combination of single-order bent columns? Briefly describe the principle of internal force combination, combination items and matters needing attention.
For general single-stage columns, the reinforcement of the whole upper column section is the same, and so is the reinforcement of the whole lower column section. Therefore, the control sections of the upper column and the lower column are obtained separately, and the bottom of the upper column is usually taken as the control section of the upper column. For the lower column, the bracket surface and column bottom are usually used as the control section.
In the internal force analysis of bent frame, it is generally to calculate the internal force of each section of column when various loads act alone. In order to find out the most unfavorable internal force that may appear on the control section of the column, we must also consider the possibility that these single loads appear at the same time, that is, the combination of load effects. After the bent structure is stressed, the bending moment m, axial force n and shear force v are generated in the column at the same time, so the bent column is an eccentric compression member, and its longitudinal stress reinforcement is related to the bending moment and axial force of the control section.
(1) In any case, the internal force generated by dead load must be considered.
(2) In the vertical load of crane, Dmax and Dmin may act on the column of a span factory building or on the right column, and only one combination can be selected.
(3) Tram lateral horizontal load Tmax acts on the same span and two pillars, and only one combination can be selected. (4) Dmax and Dmin in the same span do not necessarily occur at the same time, so when combining internal forces generated by Dmax or Dmin, it is not necessary to combine Tmax to generate internal forces.
5] When the wind load blows to the left and right, only one combination can be selected.
[6] Because it is unlikely that multiple cranes will be fully loaded at the same time, when multiple cranes participate in the combination, their internal forces should be multiplied by the corresponding load reduction factor.
What load effect combinations should be considered in the design of 2- 13 roof truss Briefly describe the key points of roof truss design.
1) full-span dead load+full-span live load
2) Full-span dead load+half-span live load
3) Roof truss gravity load+half-span roof panel gravity load+half-span roof installation live load
Reinforced commercial concrete belongs to statically indeterminate plane truss, and its internal force can be analyzed by simplified method of precise method. In addition to the calculation of bearing capacity, deformation and crack width of roof truss beam in use stage, it is also necessary to check it in construction stage.
What are the mechanical properties of 2- 14 crane beam? Briefly describe the key points of roof truss design.
1) crane load is two groups of moving concentrated loads.
2) The load of crane is only shock and vibration.
3) The crane load is repetitive.
4) The crane load causes the crane beam to generate torque.
The flexural, shear and torsional bearing capacity of crane beam should be calculated, and the fatigue strength and crack resistance of inclined section should also be checked. 3- 1 What is the standard of high-level planning in China?
Reinforced concrete commercial buildings with 10 floors and 10 floors or more than 28 meters in height are called high-rise buildings.
High-rise buildings bear more loads and have less stiffness than multi-storey buildings, and the horizontal load has greater influence on high-rise buildings than multi-storey buildings.
What are the characteristics of 3-2 frame structure? What height and purpose is it suitable for use in a house?
Frame structure is a bar system composed of horizontal frames and columns, which has the characteristics of light structure, easy layout, large use space, good integrity, convenient and economical construction, and is suitable for office buildings, libraries, commercial buildings and other buildings below 70 meters.
3-3 What are the layout methods of the frame structure? What are the characteristics of each arrangement?
There are three commonly used structural arrangements for frame structures: transverse stress arrangement, longitudinal stress arrangement and bidirectional arrangement. When the frame structure is arranged horizontally, it can improve the shortcoming of large difference between the horizontal and vertical stiffness of the building to a certain extent, and because the cross section height of the connecting beam is generally smaller than that of the main beam, the indoor clear height is larger, which is convenient for the pipeline to cross horizontally. When the foundation is uneven along the longitudinal direction of the building, the longitudinal frame can adjust this unevenness to some extent. The frame has two-way load-bearing frames in vertical and horizontal directions, so it has good integrity and mechanical properties.
3-4 How to estimate the section size of frame beams and columns?
Frame beam: HB = (1/8 ~118) l0bb = (1/2 ~1/4) HB \
L0- calculation span h B- section height b B- section width of beam
The ratio of clear distance to section height should not be less than 4, and the section width of beam should not be less than 200 mm.
Frame column: BC = (112 ~118) hihc = (1~ 2) BC.
Hi—— I layer height BC-column section width HC-column section height
The side length of the section should not be greater than 250mm, the diameter should not be less than 350mm, the shear span ratio should be greater than 2, and the section height ratio should not be greater than 3 3-5. How to determine the frame calculation diagram?
Each member of the frame is represented by a single line in the calculation drawing, so the span of the beam is equal to the column section on the left and right sides of the span and the distance between the centroid axes. The height of story column is calculated from the top surface of foundation to the floor elevation, the height of middle story column can be calculated from the next floor elevation to the upper floor elevation, and the height of top story column can be calculated from the top floor elevation to the roof elevation.
3-6 What are the internal force calculation methods of frame structure under vertical load? What are their characteristics?
1) layering method 2) overlapping band 3) coefficient method
3-7 What are the internal force calculation methods of frame structure under horizontal load?
1) Inverse bending point method 2)D value method 3) Gantry method
3-9 Why should we check the lateral displacement of the frame structure? How to check?
The lateral displacement of the frame is caused by the bending deformation of beam-column members and the axial deformation of columns. In multi-story frames, the lateral displacement caused by the axial deformation of columns is very small and can be ignored.
△uj=Vpj/∑Dij The deformation checking calculation of frame structure under normal use conditions requires that the ratio of story drift to story height △u/h should not exceed the limit of 1/550.