How to calculate the ultimate bearing capacity of steel support
Publish: 2021-05-20 18:23:39
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2.
Calculation of pre added axial force of steel support in deep foundation pit: firstly, add the pre added force to zero to calculate an anchor cable tension, which can ensure the stability of foundation pit against overturning, and then multiply it by 70 ~ 95% of the specification to get the pre added force
generally, the preloaded axial force of steel support in deep foundation pit is not more than 450kn, because the pile anchor structure is mostly sand, silt, or clay, and the uplift force of this stratum and anchor cable is limited. The preloaded force of 450kn means that the design tensile force reaches 450 / 0.95 ~ 450 / 0.7, which is basically the limit of ordinary anchor cable in this stratum. If it can not be met, it is necessary to consider densifying the anchor cable spacing
extended data:
basic requirements of deep foundation pit support:
1. The construction scheme of deep foundation pit support must be determined according to the design requirements, depth and on-site environmental engineering progress. After spinning, it shall be approved by the chief engineer of the unit and submitted to the chief supervision engineer for approval, and the construction can be carried out only when it meets the requirements of specifications and laws and regulations
2. The underground water level must be solved in the construction of deep foundation pit. Generally, light well point pumping is used to lower the underground water level to 1.0 meters below the bottom of foundation pit. A special person must be responsible for pumping water for 24 hours on ty, and the pumping records should be made. When the open ditch drainage is adopted, the drainage shall not be interrupted ring the construction period. When the structure does not have anti floating conditions, it is strictly forbidden to stop the drainage
3. During the excavation of deep foundation pit, the distance between multiple excavators should be more than 10m, and the excavation should be carried out layer by layer from top to bottom, and no deep excavation is allowed
The ladder or support should be g up and down the deep foundation pit, and it is forbidden to step on the support, and safety railings should be set around the pit5. When manually lifting earthwork, the lifting tools should be checked to see if they are reliable, and no one should stand under the bucket
When stacking materials and moving construction machinery on the side of deep foundation pit, a certain distance should be kept from the excavation edge. When the soil quality is good, it should be 0.8m away, and the height should not exceed 1.5m During the construction in rainy season, drainage measures must be taken to prevent rainwater and surface water from flowing into the deep foundation pit. During the excavation in rainy season, 15-30cm soil should be left above the elevation of the foundation pit, and the excavation should be carried out after sunny days3. Load input in PKPM
1. The load between beams in PKPM is generally the load generated by the wall on the beam
A: in the calculation, the volume weight of ordinary brick is 18 kn / m2 for the second and fourth walls (ordinary machine-made brick is generally used, which is 19 kn / m2), and the mortar layer is 17 kn / m2 (lime mortar, mixed mortar). In this way, the load generated by each square wall is: 19 times 0.24 + 17 times 0.02 times 2 = 5.24 kn / m2 (the plastering layer is generally 20 thick, double-sided mortar, which is multiplied by 2.)
finally, multiply 5.24 times the wall area on the beam to get the load on the beam
5.24 is a data that is used a lot. If you are familiar with it, you will know it. You can use it directly when calculating
2. When the building model is completed, the dead load and live load on the floor are input, and the load on the beam is input: what should the dead load on the beam include? What should live load include“ What is the purpose of "floor load conction calculation"
does the dead load on the beam include: main beam: dead weight of the beam + main beam under the heavy floor of self bearing wall on the beam: dead weight of the beam. Do you want to add the self weight of the secondary beam on the main beam, the self weight of the floor and the load on it? Does the dead load on the column only include the self weight of the section of the floor where it is located? Do you want to add the load above the floor? Is that right After the dead load and live load are arranged on the floor, only the self weight of the beam is considered when the load of the beam is arranged. Then all the loads on the beam are calculated in the load conction calculation
A: generally, as long as the dead load and live load on the floor are input, it should be noted that the dead load of the floor should include the dead weight of the floor (except for the automatic calculation of the dead weight of the floor)
the program will automatically transmit the floor load to the beam, so the dead weight of the infill wall on the beam is generally input as the dead load, and the dead weight of all beams
columns does not need to be input, so the program will automatically calculate. For columns, it is not necessary to input loads, and all loads transmitted from beams will be automatically calculated back to columns
the above is the general situation, so it is necessary to input the load according to the actual situation. For example, if there is no infilled wall on the beam, but there is a heavy equipment, the dead load of the beam is not input, but the live load on the beam should be input according to the actual force of the equipment. Another example is that the column is subjected to a horizontal force in the middle,
for example, if an awning diagonal rod is set to pull on the column, then the live load of the column must be input. Floor load conction calculation is to transfer the floor load to the beam, then the beam load to the column, and then the column load to the lowest floor, so as to prepare for the foundation calculation
3. What are the load between PKPM beams, uniform load and concentrated load? Where is the load
distributed load (uniform load)
continuous action on a large area of member surface can not be regarded as concentrated load, and any two loads with the same magnitude and direction are called uniformly distributed load
concentrated load is a concept corresponding to uniformly distributed load, and its action area is very small relative to the acted surface, The load that can be simplified as a point is the concentrated load
in PKPM, there may be uniform load between beams and walls. For example, in frame structure, between floor beams, partition walls should be built, and the location of partition walls can be found on a closed surface between columns and beams, which is simplified as uniform load evenly distributed on beams
the concentrated load depends on the specific situation. For example, if a small column is built on a certain beam, and the small column is not planned to be built in the model or the elevation is not on the floor, then the force on the column can be converted into a concentrated force and added to the corresponding action point of the beam or column
the loading position depends on the action position, where the load is applied ~
there is node load, which is not used in general, but for example, the sloping roof will have horizontal force on the beam, while the uniform load and concentrated load in PKPM are all added vertically, so the horizontal force must be applied with node load ~
4 PKPM masonry structure modeling
in the process of PM modeling, I subtract the window and door openings on the wall. Is it necessary to input the loads between beams and walls
best answer
when modeling masonry, the self weight of the wall will be automatically calculated by the program. In addition, you have to input all the loads yourself
5. What is the load between columns in PKPM
the load between columns is the load acting on the middle of columns. It depends on the actual situation. General frame structure is not, but to actual analysis, for example, you pick a bracket on the column, support something else, then you need to add the load between the columns. Or if your column is subjected to horizontal concentrated force at half the height, it should also be increased. That is to say, if there is a load, you will lose; if there is no load, you will not lose
there are live and dead loads on the column. The dead load is calculated automatically by program. The live load is generally transmitted from beams and slabs. Generally, the column load is not input. Generally need to calculate their own input is the beam dead load, the weight of the wall (infilled wall - frame structure), shear wall does not need. Then there is the live load on the plate. In LT, there are reserved openings, but the load needs to be input
6. Generally, as long as the dead load and live load on the floor are input, it should be noted that the dead load of the floor should include the dead weight of the floor (except for the automatic calculation of the dead weight of the floor). The program will automatically transmit the floor load to the beam, so the dead weight of the infill wall on the beam is generally input as the dead load, and the dead weight of all beams and columns does not need to be input, so the program will automatically calculate. For columns, it is not necessary to input loads, and all loads transmitted from beams will be automatically calculated back to columns.
1. The load between beams in PKPM is generally the load generated by the wall on the beam
A: in the calculation, the volume weight of ordinary brick is 18 kn / m2 for the second and fourth walls (ordinary machine-made brick is generally used, which is 19 kn / m2), and the mortar layer is 17 kn / m2 (lime mortar, mixed mortar). In this way, the load generated by each square wall is: 19 times 0.24 + 17 times 0.02 times 2 = 5.24 kn / m2 (the plastering layer is generally 20 thick, double-sided mortar, which is multiplied by 2.)
finally, multiply 5.24 times the wall area on the beam to get the load on the beam
5.24 is a data that is used a lot. If you are familiar with it, you will know it. You can use it directly when calculating
2. When the building model is completed, the dead load and live load on the floor are input, and the load on the beam is input: what should the dead load on the beam include? What should live load include“ What is the purpose of "floor load conction calculation"
does the dead load on the beam include: main beam: dead weight of the beam + main beam under the heavy floor of self bearing wall on the beam: dead weight of the beam. Do you want to add the self weight of the secondary beam on the main beam, the self weight of the floor and the load on it? Does the dead load on the column only include the self weight of the section of the floor where it is located? Do you want to add the load above the floor? Is that right After the dead load and live load are arranged on the floor, only the self weight of the beam is considered when the load of the beam is arranged. Then all the loads on the beam are calculated in the load conction calculation
A: generally, as long as the dead load and live load on the floor are input, it should be noted that the dead load of the floor should include the dead weight of the floor (except for the automatic calculation of the dead weight of the floor)
the program will automatically transmit the floor load to the beam, so the dead weight of the infill wall on the beam is generally input as the dead load, and the dead weight of all beams
columns does not need to be input, so the program will automatically calculate. For columns, it is not necessary to input loads, and all loads transmitted from beams will be automatically calculated back to columns
the above is the general situation, so it is necessary to input the load according to the actual situation. For example, if there is no infilled wall on the beam, but there is a heavy equipment, the dead load of the beam is not input, but the live load on the beam should be input according to the actual force of the equipment. Another example is that the column is subjected to a horizontal force in the middle,
for example, if an awning diagonal rod is set to pull on the column, then the live load of the column must be input. Floor load conction calculation is to transfer the floor load to the beam, then the beam load to the column, and then the column load to the lowest floor, so as to prepare for the foundation calculation
3. What are the load between PKPM beams, uniform load and concentrated load? Where is the load
distributed load (uniform load)
continuous action on a large area of member surface can not be regarded as concentrated load, and any two loads with the same magnitude and direction are called uniformly distributed load
concentrated load is a concept corresponding to uniformly distributed load, and its action area is very small relative to the acted surface, The load that can be simplified as a point is the concentrated load
in PKPM, there may be uniform load between beams and walls. For example, in frame structure, between floor beams, partition walls should be built, and the location of partition walls can be found on a closed surface between columns and beams, which is simplified as uniform load evenly distributed on beams
the concentrated load depends on the specific situation. For example, if a small column is built on a certain beam, and the small column is not planned to be built in the model or the elevation is not on the floor, then the force on the column can be converted into a concentrated force and added to the corresponding action point of the beam or column
the loading position depends on the action position, where the load is applied ~
there is node load, which is not used in general, but for example, the sloping roof will have horizontal force on the beam, while the uniform load and concentrated load in PKPM are all added vertically, so the horizontal force must be applied with node load ~
4 PKPM masonry structure modeling
in the process of PM modeling, I subtract the window and door openings on the wall. Is it necessary to input the loads between beams and walls
best answer
when modeling masonry, the self weight of the wall will be automatically calculated by the program. In addition, you have to input all the loads yourself
5. What is the load between columns in PKPM
the load between columns is the load acting on the middle of columns. It depends on the actual situation. General frame structure is not, but to actual analysis, for example, you pick a bracket on the column, support something else, then you need to add the load between the columns. Or if your column is subjected to horizontal concentrated force at half the height, it should also be increased. That is to say, if there is a load, you will lose; if there is no load, you will not lose
there are live and dead loads on the column. The dead load is calculated automatically by program. The live load is generally transmitted from beams and slabs. Generally, the column load is not input. Generally need to calculate their own input is the beam dead load, the weight of the wall (infilled wall - frame structure), shear wall does not need. Then there is the live load on the plate. In LT, there are reserved openings, but the load needs to be input
6. Generally, as long as the dead load and live load on the floor are input, it should be noted that the dead load of the floor should include the dead weight of the floor (except for the automatic calculation of the dead weight of the floor). The program will automatically transmit the floor load to the beam, so the dead weight of the infill wall on the beam is generally input as the dead load, and the dead weight of all beams and columns does not need to be input, so the program will automatically calculate. For columns, it is not necessary to input loads, and all loads transmitted from beams will be automatically calculated back to columns.
4. This is the numerical representation in computer programs. E is the representation when 10 is used as the power base
7.85e + 03 is the third power of
7.85 times 10
do you understand? If you have any questions, you can ask me.
7.85e + 03 is the third power of
7.85 times 10
do you understand? If you have any questions, you can ask me.
5. Unknown_Error
6. What are the requirements of acceptance standards for steel braces
the acceptance standards for buckling restrained braces are only mentioned in the 2010 edition of code for seismic design of buildings (GB 50011-2010) and technical specification for steel structures of high rise civil buildings (jgj99-2010), but the standards are still low:
1 [GB 50011-2010] buckling restrained braces shall be inspected by sampling test according to the structural form of braces, material of restrained yield section and yield bearing capacity classification in the same project. Buckling restrained braces with the same structural form and material of restrained yield section and yield bearing capacity in the range of 50% to 150% are divided into the same category. The sampling proportion of each category is 2%, and not less than one. During the test, the deformation was carried out three times in turn at 1 / 300, 1 / 200, 1 / 150 and 1 / 100 support length, respectively. The test results show that the hysteretic curve should be stable, full, with positive incremental stiffness, and the bearing capacity of the third cycle of the last stage deformation is not less than 85% of the maximum bearing capacity experienced, and the maximum bearing capacity experienced is not more than 1.1 times of the calculated ultimate bearing capacity of buckling restrained braces
2. [GB 50011-2010] the number of non reusable energy dissipaters, such as metal yield displacement related energy dissipaters, shall not be less than 2 in the same type, and the qualified rate of sampling inspection is 100%. After sampling inspection, they can not be used for the main structure. Type inspection and delivery inspection shall be completed by a third party
3. [jgj99-2010] e.5.1 the design of buckling restrained braces should be based on the test results, and there should be at least two groups of tests: one group is component test to investigate the rotation requirements of brace connection; The other group is the uniaxial test of the brace to test the working behavior of the brace, especially the hysteretic behavior under tension and compression
4. [jgj99-2010] e.5.2 the test loading of buckling restrained braces should be controlled by displacement, the axial displacement should be controlled ring the component test, and the rotational displacement should be controlled ring the component test
5. [jgj99-2010] e.5.3 the energy dissipation buckling restrained brace test should be carried out according to the following loading amplitude and sequence: the axial cumulative inelastic deformation should be at least 200 times of the yield deformation by three times of the tensile and compressive reciprocating deformation of 1 / 300, 1 / 200, 1 / 150 and 1 / 100 brace length respectively (this requirement is not required for component test)
6 [jgj99-2010]
e.5.4 test and inspection requirements for buckling restrained braces
1) in the same project, the buckling restrained braces shall be tested and inspected according to the structural form of braces, core steel support materials and yield bearing capacity classification. The sampling proportion is 2%, and each category has at least one specimen. Buckling restrained braces with the same structural form and core steel support material and the yield bearing capacity within the range of 50% to 150% of the specimen bearing capacity are classified into the same category
2) full scale specimens should be used for the test. If the test device can not meet the requirements of full-scale test, the length of the specimen can be reced
3) the fabrication of buckling restrained brace specimens and components should reflect the actual design situation, including material, size, cross-section composition and end connection of the brace
4) according to the relevant national standards, the material properties of each batch of steel for buckling restrained brace core steel brace should be tested
5) when the test results of the buckling restrained brace specimens meet the following requirements, the specimens are qualified:
A) the material test results meet the requirements of Clause 1 of e.3.8
b) the hysteretic curves of buckling restrained brace specimens are stable and full, and the stiffness increases steadily without stiffness degradation
C) buckling restrained braces have no fracture and joint failure
d) the maximum tensile and compressive capacity of the core element after yielding in each loading cycle is not less than the yield load, and the ratio of the maximum pressure and the maximum tension is not more than 1.3
the code for traditional seismic design has been under review and has not been released. It is the draft of code for seismic energy dissipation of buildings for approval. The testing standard for procts is: routine performance serial number, project performance requirement 1, and the yield load is less than the design value ± Within 15%; At the end of the design value ± Within 10%. 2 yield displacement in design value ± Within 15%; Calculation of design value of yield displacement ± Within 10%. 3. The change of the stiffness after yielding in the design value ± Within 15%; At the end of the design value ± 4% of the design value within 10% ± Within 15%; At the end of the design value ± Within 10%. 5 limit displacement the limit displacement value of each measured proct shall not be less than the design limit displacement value. 6 hysteresis curve area in any cycle, the deviation of measured hysteresis curve envelope area should be less than 1% of the proct design value ± Within 15%; The average deviation of the measured value should be within the design value of the proct ± Within 10%. Fatigue performance 1 the measured damping force of the proct is loaded continuously for 30 cycles under the design displacement under rare earthquake action. The maximum and minimum damping forces of any cycle shall be less than the average value of the maximum and minimum damping forces of all cycles ± Within 15%. 2 hysteresis curve 1) the measured proct is loaded continuously for 30 cycles under the design displacement under rare earthquake action, and the maximum and minimum damping forces when the displacement is zero in any cycle shall be equal to the average value of the maximum and minimum damping forces when the displacement is zero in all cycles ± Within 15%
2) under the design displacement of the measured proct under rare earthquake action, the maximum and minimum displacement when the damping force is zero in any cycle shall be equal to the average value of the maximum and minimum displacement when the damping force is zero in all cycles ± Within 15%. 3. The measured area of hysteresis curve is loaded continuously for 30 cycles under the design displacement under rare earthquake action. The area of hysteresis curve of any cycle shall be less than the average value of the area of hysteresis curve of all cycles ± Within 15%.
the acceptance standards for buckling restrained braces are only mentioned in the 2010 edition of code for seismic design of buildings (GB 50011-2010) and technical specification for steel structures of high rise civil buildings (jgj99-2010), but the standards are still low:
1 [GB 50011-2010] buckling restrained braces shall be inspected by sampling test according to the structural form of braces, material of restrained yield section and yield bearing capacity classification in the same project. Buckling restrained braces with the same structural form and material of restrained yield section and yield bearing capacity in the range of 50% to 150% are divided into the same category. The sampling proportion of each category is 2%, and not less than one. During the test, the deformation was carried out three times in turn at 1 / 300, 1 / 200, 1 / 150 and 1 / 100 support length, respectively. The test results show that the hysteretic curve should be stable, full, with positive incremental stiffness, and the bearing capacity of the third cycle of the last stage deformation is not less than 85% of the maximum bearing capacity experienced, and the maximum bearing capacity experienced is not more than 1.1 times of the calculated ultimate bearing capacity of buckling restrained braces
2. [GB 50011-2010] the number of non reusable energy dissipaters, such as metal yield displacement related energy dissipaters, shall not be less than 2 in the same type, and the qualified rate of sampling inspection is 100%. After sampling inspection, they can not be used for the main structure. Type inspection and delivery inspection shall be completed by a third party
3. [jgj99-2010] e.5.1 the design of buckling restrained braces should be based on the test results, and there should be at least two groups of tests: one group is component test to investigate the rotation requirements of brace connection; The other group is the uniaxial test of the brace to test the working behavior of the brace, especially the hysteretic behavior under tension and compression
4. [jgj99-2010] e.5.2 the test loading of buckling restrained braces should be controlled by displacement, the axial displacement should be controlled ring the component test, and the rotational displacement should be controlled ring the component test
5. [jgj99-2010] e.5.3 the energy dissipation buckling restrained brace test should be carried out according to the following loading amplitude and sequence: the axial cumulative inelastic deformation should be at least 200 times of the yield deformation by three times of the tensile and compressive reciprocating deformation of 1 / 300, 1 / 200, 1 / 150 and 1 / 100 brace length respectively (this requirement is not required for component test)
6 [jgj99-2010]
e.5.4 test and inspection requirements for buckling restrained braces
1) in the same project, the buckling restrained braces shall be tested and inspected according to the structural form of braces, core steel support materials and yield bearing capacity classification. The sampling proportion is 2%, and each category has at least one specimen. Buckling restrained braces with the same structural form and core steel support material and the yield bearing capacity within the range of 50% to 150% of the specimen bearing capacity are classified into the same category
2) full scale specimens should be used for the test. If the test device can not meet the requirements of full-scale test, the length of the specimen can be reced
3) the fabrication of buckling restrained brace specimens and components should reflect the actual design situation, including material, size, cross-section composition and end connection of the brace
4) according to the relevant national standards, the material properties of each batch of steel for buckling restrained brace core steel brace should be tested
5) when the test results of the buckling restrained brace specimens meet the following requirements, the specimens are qualified:
A) the material test results meet the requirements of Clause 1 of e.3.8
b) the hysteretic curves of buckling restrained brace specimens are stable and full, and the stiffness increases steadily without stiffness degradation
C) buckling restrained braces have no fracture and joint failure
d) the maximum tensile and compressive capacity of the core element after yielding in each loading cycle is not less than the yield load, and the ratio of the maximum pressure and the maximum tension is not more than 1.3
the code for traditional seismic design has been under review and has not been released. It is the draft of code for seismic energy dissipation of buildings for approval. The testing standard for procts is: routine performance serial number, project performance requirement 1, and the yield load is less than the design value ± Within 15%; At the end of the design value ± Within 10%. 2 yield displacement in design value ± Within 15%; Calculation of design value of yield displacement ± Within 10%. 3. The change of the stiffness after yielding in the design value ± Within 15%; At the end of the design value ± 4% of the design value within 10% ± Within 15%; At the end of the design value ± Within 10%. 5 limit displacement the limit displacement value of each measured proct shall not be less than the design limit displacement value. 6 hysteresis curve area in any cycle, the deviation of measured hysteresis curve envelope area should be less than 1% of the proct design value ± Within 15%; The average deviation of the measured value should be within the design value of the proct ± Within 10%. Fatigue performance 1 the measured damping force of the proct is loaded continuously for 30 cycles under the design displacement under rare earthquake action. The maximum and minimum damping forces of any cycle shall be less than the average value of the maximum and minimum damping forces of all cycles ± Within 15%. 2 hysteresis curve 1) the measured proct is loaded continuously for 30 cycles under the design displacement under rare earthquake action, and the maximum and minimum damping forces when the displacement is zero in any cycle shall be equal to the average value of the maximum and minimum damping forces when the displacement is zero in all cycles ± Within 15%
2) under the design displacement of the measured proct under rare earthquake action, the maximum and minimum displacement when the damping force is zero in any cycle shall be equal to the average value of the maximum and minimum displacement when the damping force is zero in all cycles ± Within 15%. 3. The measured area of hysteresis curve is loaded continuously for 30 cycles under the design displacement under rare earthquake action. The area of hysteresis curve of any cycle shall be less than the average value of the area of hysteresis curve of all cycles ± Within 15%.
7. 1 General situation of the project
a 33 ~ 38 building of an International Plaza is designed to have one floor underground and 17 ~ 24 floors above the ground, and the transfer floor of the project is located on the second floor. The height of transfer floor is 4.80m, and the cross-section size of frame support and joist of transfer floor is 600mm × 1600mm、700mm × 1600mm、750 mm × 1600 mm、850mm × 1600mm, etc. These beams are bulky and heavy, and the design of formwork and support is the key to construction. Before the construction of the transfer floor, the special construction scheme was designed, and the existing common steel pipe and steel support, plywood and timber were used to solve the construction problems< (2) design scheme of formwork and full scaffold support
1. Design scheme of formwork engineering
the typical transfer floor beam is 850mm × 1600mm (see Figure 1)
Figure 1 × 1600 transfer girder formwork and support system diagram
(1) the beam bottom is 50mm × The beam width is 800-850mm, and five rows of 50 mm are set longitudinally × 100 mm wood square, the spacing is 200-250 mm; The beam width is 600-750mm, and four rows of 50mm are set longitudinally × 100 mm timber square, the middle spacing is 200-250 mm, the transverse timber square spacing is 300, and the beam bottom formwork is laid on it
(2) beam side formwork
the beam side formwork adopts plywood, 50mm × 100 m is used as mould. The horizontal formwork spacing is 400mm, and the vertical formwork spacing is 400mm. The overall beam is pulled by M12 screw, and the screw is set from the bottom of the beam. The horizontal and vertical spacing are set as 400mm 3) Support system of beam slab formwork:
① steel support is adopted at the bottom of frame supported beam. According to the beam width, a steel support is set every 200-250, the longitudinal spacing of steel support is 500mm, and a draw bar is set between the steel supports of floor slab. The scaffold shall be erected according to Clause 3 and Clause 2, with two upper layers × 59mm × 100 mm timber square and springboard are used as steel support, and frame beam (850 mm) is used below × 1600mm) as an example to calculate the strength stability of steel support
② reinforcement measures for basement roof strength
the frame beam steel is supported on the basement roof, with the thickness of 200 mm and the concrete of C30. In order to ensure the bearing capacity of the floor, ring the construction of the second transfer floor, the scaffold support of the basement is not removed, so that the construction load of the transfer floor is transmitted to the foundation through the support
2. The design scheme of support
because the transfer floor is tall, which exceeds the length of ordinary steel support, the steel pipe frame should be set up on the platform. The erection height of the lower frame of the frame supported beam is 2.6m, and the erection height of other parts is 4.4m, which is convenient for binding the beam reinforcement of the transfer floor. Steel pipe frame adopts ф 48 steel pipe is set up, under which wooden springboard and square are used as the bottom plate. The first crossbar is 0.2m from the ground, the second crossbar is 1.2m from the first crossbar, and the fourth crossbar is 1.8m from the third crossbar. The spacing between scaffold poles is 1000mm × 1000mm, within 2m below the frame beam, the densification of vertical pole is 500m × 500m, and each node operator is added one after another to ensure that the fastener does not slip. Every 4000 mm × In order to enhance the overall performance of the steel pipe frame, cross bracing is set within 4000 mm
3. Checking calculation of formwork support system of transfer floor
the 1m long transfer floor girder is taken as the calculation unit for stress checking calculation:
(1) formwork load (taking 850 × 1600 section frame supported beam as an example)
self weight load of frame supported beam formwork 1.2kn. M
self weight load of concrete 32.64kn. M
self weight load of reinforcement 3.6kn. M
load generated by concrete vibration 2Kn. M
self weight of construction personnel and equipment 2.5kn. M
total: 12 × 1.2＋32.64＋3.6＋1.4 × 2 + 2.5) = 51.23kn. M
(2) checking calculation of bottom formwork
① checking calculation of bending bearing capacity
bottom formwork steel support is a multi span continuous beam with more than 5 spans, which is calculated according to 5 spans, the most unfavorable load group is selected, and the coefficient km = -0.105, shear coefficient kV = 0.606, deflection coefficient kV = 0.644 are obtained by looking up the table, which meets the requirements
② deflection checking
the load does not include the construction live load, q = 37.44kn/m, so the deflection meets the requirements< (3) lateral formwork checking
① lateral pressure
if the smaller value is multiplied by the partial factor of 1.2, and the lateral pressure proced by pouring concrete is 4kn / m2, then
② bending strength checking
according to the calculation of five span continuous beam, km, kV and kW are the same as before, and the timber can meet the requirements
③ checking calculation of shear strength
so the wood square meets the shear requirements
④ deflection checking calculation
(4) checking calculation of counter pulling screw
tensile force of each screw
(5) checking calculation of support
the main checking calculation is that the steel support is unstable, and the upper column of steel support is ф 48, the lower column is ф 50，i1=1.57cm,i2=1.87cm，I1=9.89cm4，I2=21.14cm4
the anti sliding calculation of scaffold fastener, because each steel support is under pressure of N and 5.08kn, it is assumed that all of them are transmitted to one steel fastener, and because the anti sliding [R] = 8kN, it meets the requirements
(3) conclusion
e to the sufficient construction preparation, the special construction design scheme of transfer floor formwork and support system was made in detail before the construction, and the detailed technical disclosure was carried out before the implementation. During the construction process, the operation was guided strictly according to the design scheme, and the transfer floor construction was very smooth without any quality problems<
[References]
[1] Ministry of construction of the people's Republic of China. Code for design of timber structures (GB 5005-2003)
[S]. Beijing: China Construction Instry Press, 2003.
[2] compilation group of code for design of steel structures. Code for design of steel structures (GB 50017-2003)
[S]. Beijing: China Planning Press, 2003, 2003.
[3] Chinese Academy of Building Sciences. Code for acceptance of construction quality of concrete structures (GB 50204-2002) [S]. Beijing: China Construction Instry Press, 2003.
[4] Yang Sixin, Yu Zhicheng, Hou qunwei. Template construction manual for building engineering [M]. Beijing: China Construction Instry Press, 2004
a 33 ~ 38 building of an International Plaza is designed to have one floor underground and 17 ~ 24 floors above the ground, and the transfer floor of the project is located on the second floor. The height of transfer floor is 4.80m, and the cross-section size of frame support and joist of transfer floor is 600mm × 1600mm、700mm × 1600mm、750 mm × 1600 mm、850mm × 1600mm, etc. These beams are bulky and heavy, and the design of formwork and support is the key to construction. Before the construction of the transfer floor, the special construction scheme was designed, and the existing common steel pipe and steel support, plywood and timber were used to solve the construction problems< (2) design scheme of formwork and full scaffold support
1. Design scheme of formwork engineering
the typical transfer floor beam is 850mm × 1600mm (see Figure 1)
Figure 1 × 1600 transfer girder formwork and support system diagram
(1) the beam bottom is 50mm × The beam width is 800-850mm, and five rows of 50 mm are set longitudinally × 100 mm wood square, the spacing is 200-250 mm; The beam width is 600-750mm, and four rows of 50mm are set longitudinally × 100 mm timber square, the middle spacing is 200-250 mm, the transverse timber square spacing is 300, and the beam bottom formwork is laid on it
(2) beam side formwork
the beam side formwork adopts plywood, 50mm × 100 m is used as mould. The horizontal formwork spacing is 400mm, and the vertical formwork spacing is 400mm. The overall beam is pulled by M12 screw, and the screw is set from the bottom of the beam. The horizontal and vertical spacing are set as 400mm 3) Support system of beam slab formwork:
① steel support is adopted at the bottom of frame supported beam. According to the beam width, a steel support is set every 200-250, the longitudinal spacing of steel support is 500mm, and a draw bar is set between the steel supports of floor slab. The scaffold shall be erected according to Clause 3 and Clause 2, with two upper layers × 59mm × 100 mm timber square and springboard are used as steel support, and frame beam (850 mm) is used below × 1600mm) as an example to calculate the strength stability of steel support
② reinforcement measures for basement roof strength
the frame beam steel is supported on the basement roof, with the thickness of 200 mm and the concrete of C30. In order to ensure the bearing capacity of the floor, ring the construction of the second transfer floor, the scaffold support of the basement is not removed, so that the construction load of the transfer floor is transmitted to the foundation through the support
2. The design scheme of support
because the transfer floor is tall, which exceeds the length of ordinary steel support, the steel pipe frame should be set up on the platform. The erection height of the lower frame of the frame supported beam is 2.6m, and the erection height of other parts is 4.4m, which is convenient for binding the beam reinforcement of the transfer floor. Steel pipe frame adopts ф 48 steel pipe is set up, under which wooden springboard and square are used as the bottom plate. The first crossbar is 0.2m from the ground, the second crossbar is 1.2m from the first crossbar, and the fourth crossbar is 1.8m from the third crossbar. The spacing between scaffold poles is 1000mm × 1000mm, within 2m below the frame beam, the densification of vertical pole is 500m × 500m, and each node operator is added one after another to ensure that the fastener does not slip. Every 4000 mm × In order to enhance the overall performance of the steel pipe frame, cross bracing is set within 4000 mm
3. Checking calculation of formwork support system of transfer floor
the 1m long transfer floor girder is taken as the calculation unit for stress checking calculation:
(1) formwork load (taking 850 × 1600 section frame supported beam as an example)
self weight load of frame supported beam formwork 1.2kn. M
self weight load of concrete 32.64kn. M
self weight load of reinforcement 3.6kn. M
load generated by concrete vibration 2Kn. M
self weight of construction personnel and equipment 2.5kn. M
total: 12 × 1.2＋32.64＋3.6＋1.4 × 2 + 2.5) = 51.23kn. M
(2) checking calculation of bottom formwork
① checking calculation of bending bearing capacity
bottom formwork steel support is a multi span continuous beam with more than 5 spans, which is calculated according to 5 spans, the most unfavorable load group is selected, and the coefficient km = -0.105, shear coefficient kV = 0.606, deflection coefficient kV = 0.644 are obtained by looking up the table, which meets the requirements
② deflection checking
the load does not include the construction live load, q = 37.44kn/m, so the deflection meets the requirements< (3) lateral formwork checking
① lateral pressure
if the smaller value is multiplied by the partial factor of 1.2, and the lateral pressure proced by pouring concrete is 4kn / m2, then
② bending strength checking
according to the calculation of five span continuous beam, km, kV and kW are the same as before, and the timber can meet the requirements
③ checking calculation of shear strength
so the wood square meets the shear requirements
④ deflection checking calculation
(4) checking calculation of counter pulling screw
tensile force of each screw
(5) checking calculation of support
the main checking calculation is that the steel support is unstable, and the upper column of steel support is ф 48, the lower column is ф 50，i1=1.57cm,i2=1.87cm，I1=9.89cm4，I2=21.14cm4
the anti sliding calculation of scaffold fastener, because each steel support is under pressure of N and 5.08kn, it is assumed that all of them are transmitted to one steel fastener, and because the anti sliding [R] = 8kN, it meets the requirements
(3) conclusion
e to the sufficient construction preparation, the special construction design scheme of transfer floor formwork and support system was made in detail before the construction, and the detailed technical disclosure was carried out before the implementation. During the construction process, the operation was guided strictly according to the design scheme, and the transfer floor construction was very smooth without any quality problems<
[References]
[1] Ministry of construction of the people's Republic of China. Code for design of timber structures (GB 5005-2003)
[S]. Beijing: China Construction Instry Press, 2003.
[2] compilation group of code for design of steel structures. Code for design of steel structures (GB 50017-2003)
[S]. Beijing: China Planning Press, 2003, 2003.
[3] Chinese Academy of Building Sciences. Code for acceptance of construction quality of concrete structures (GB 50204-2002) [S]. Beijing: China Construction Instry Press, 2003.
[4] Yang Sixin, Yu Zhicheng, Hou qunwei. Template construction manual for building engineering [M]. Beijing: China Construction Instry Press, 2004
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