Comprehensive construction technology of super high-rise concrete-filled steel tube structure in Shenzhen SEG Plaza-The Ninth National Conference on Structural Engineering
Invited report of the 9th National Structural Engineering Conference on Super High-Rise Concrete-Filled Steel Tube Structure of Shenzhen SEG Plaza Su Shimei China Construction Engineering Bureau, Beijing 1001 Top-down construction technology, comprehensive construction technology of concrete-filled steel tube structure, high-throwing, vibration-free and self-compacting concrete construction technology. Popularized and applied the construction technology of the unsupported hanging form of the stiff concrete floor, the construction technology of the core-tube elevator shaft tool-type overall lifting formwork, the technology of concentration, mixing of commercial concrete, and the cold extrusion connection technology of thick steel bars. A series of new materials and technologies such as the permeable rigid waterproof technology of the underground and outdoor walls and the automatic temperature measurement computer control system for mass concrete. The development and application of these new technologies have laid the foundation for the high-quality, high-level and high-speed construction of SEG Plaza.
Steel Structure Installation 1 Project Overview 1.1 Shenzhen SEG Plaza, undertaken by the China Construction Bureau, is a modern, multi-functional and intelligent super high-rise building that focuses on high-tech electronic supporting markets and integrates office, exhibition, trade, financial, securities, and entertainment. The project covers an area of ​​9653, with 72 floors above ground and a height of 353.
Depth 19. The total construction area of ​​16670 adopts the combined structure of frame tube structure system and steel tube concrete column steel beam. The tower with an angular plane is arranged with 16 steel tube concrete outer frame columns with a diameter of 1.60 meters along the perimeter, and the core tube is arranged with 8 steel tube concrete columns with a diameter of 8 meters and 1.10 meters on each side connected with steel beams to form a frame -Type cylinder wall structure strong anti-side force member. Between the core tube and the outer frame column is a welded I-beam, a profiled steel plate is laid on the steel beam, and shear studs are set on the flange of the steel beam, and reinforced concrete slabs are poured on it to form an overall composite structure building surface. Along the vertical direction of the tower, a 15-layer reinforced layer is installed from the top of the podium, and 16 steel truss are installed between the core tube and the outer frame column in the reinforced layer, and the periphery of the outer column of this layer is also set up. Steel truss. The reinforced layer forms a relatively rigid disc body, which enhances the working performance of the outer frame of the tower and the core tube, and constitutes a strong spatial anti-side force structural system, which bears the effect of wind load and earthquake.
Su Shimei, male, born in 1945.10, visiting professor, director, and professor-level senior engineer of Tsinghua University 1.2 Construction Technology Overview The construction process of concrete-filled steel tube structure consists of two parts. It is the manufacture and installation of steel structures, including the construction of steel tube reinforced concrete structures, including the pouring of steel tube core concrete, floor profiled steel plates and reinforced concrete floor panels, reinforced concrete shear wall elevator shafts and stairwells.
In the construction of the SEG Plaza, the China Construction Bureau focused on the development of the reverse-construction method of the basement of the basement and the comprehensive construction technology of the concrete-filled steel tube structure. Popularized and applied the construction technology of the unsupported hanging form of the stiff concrete floor, the construction technology of the core-type elevator shaft tool-type overall lifting formwork, the technology of centralized mixing and commercial concrete, and the cold extrusion connection technology of thick steel bars. A series of new materials and technologies such as the permeable rigid waterproof technology of the underground and outdoor walls and the automatic temperature measurement computer control system for mass concrete. The development and application of these new technologies have laid the foundation for the high-quality, high-level and high-speed construction of SEG Plaza.
The following is a brief introduction of the 2 reverse construction method in turn. After the construction of the underground continuous wall and the artificial digging pile, the steel tube concrete column of the 4th basement and the first floor beam and slab structure are constructed, and the crown beam is used to make it and the surrounding Underground continuous wall connection. After this, two construction work surfaces above and below the ground were formed. The physical quantity of the construction of the SEG Plaza project using the reverse construction method is the earthwork excavation and transportation project, the steel structure installation project, the reinforcement project, the template project, the concrete project.
2.1 Deep foundation pit support In the reverse construction method, how to consider and implement deep foundation pit support is the first difficulty. In the construction scheme of the reverse construction method of the basement of SEG Plaza, the deep foundation pit support is to adopt the peripheral structure composed of the underground continuous wall and part of the frame along the wall and its floor structure to bear the external horizontal force of the foundation pit.
The surrounding structure is gradually formed with the excavation of earthwork layer by layer, and its lateral resistance performance is also gradually strengthened. Because the supporting conditions of the foundation pit are first ensured in the plan, the surrounding structure forms a reliable horizontal support of multiple ground connecting walls, and the horizontal lateral displacement of the underground continuous wall during the earthwork excavation process is effectively controlled.
2.2 How to consider the relationship between various professional types of work in the division of construction plane and space, and how to reasonably arrange the division of construction plane and space is the biggest difficulty. In the reverse construction method of the basement of SEG Plaza, the following principles should be followed. First, the structural safety must be ensured, and the foundation pit supporting conditions must be met. Therefore, the plane range of the supporting structure and the plane and space required in the formation process should be guaranteed first.
The second is the earthwork space. Because a large amount of dark excavation in the reverse construction method must be completed and transported to the site within a limited time, it is the key to improving the efficiency and shortening the construction period to fully ensure that the earthwork can achieve the maximum mechanization on the construction plane and space conditions.
On the premise of ensuring the above two, material channel equipment and steel component channel should be arranged like personnel channel. SEG Plaza has four floors of basement. The reverse construction method is long and the construction process is complicated. Therefore, in the construction process, the rational division and utilization of planes and spaces also need to be continuously adjusted and changed. Coordination and cooperation between various professions and types of work processes on site are extremely important.
2.3 The first difficulty in reverse construction is how to formulate the best construction plan for each professional type of work. 2.3.1 Earthwork construction plan SEG Plaza is located in the downtown area, and the amount of earthwork excavated by reverse construction exceeds 10,000 cubic meters. Ergonomics and unearthed speed are crucial. The principle of the earthwork excavation and transportation scheme is to maximize the degree of mechanization of the excavation and transportation under the premise of ensuring the safety of the foundation pit, excavation and soil collection during the day, and concentrated shipment at night. During earth excavation, 12 settlement observation points were set along the crown beams around the underground continuous wall, and settlement observation points were selectively set on the surrounding buildings. Earthwork, after digging, insist on observation times every day. Since the project did not take measures such as precipitation, it did not cause harmful settlement of surrounding buildings. In the process of earthwork excavation, horizontal displacement measuring points of the underground continuous wall are set along each side of the underground continuous wall. Each measuring point starts from under the first floor slab and is continuously arranged downward. Continuously observe the lateral movement of the underground continuous wall. Since the excavation of each floor is started after the upper horizontal support is formed, and the excavation depth of each floor is limited to the height of the floor, the lateral displacement of the underground continuous wall is relatively small, and the maximum horizontal displacement of the wall is only 21 sleeps.
2.3.2 Steel structure installation plan Because the reverse construction steel structure installation is all carried out under the first floor slab, large lifting machinery can not be used. Steel equipment wheel set and fairy hoist are used as special tools and special hoisting technology to complete.
2.3.3 Reinforced concrete structure construction plan In the reverse construction method, the earthwork steel structure installation and the concrete project are connected and cross-constructed, and any work should try to shorten their working time and provide construction conditions for subsequent processes. In the reverse construction method of the basement of SEG Plaza, all the rigid concrete floor structures are all constructed by the hanging form method, because the hanging form construction scheme is not necessary to wait for the template as long as the floor structure concrete strength meets the requirements after the floor concrete is poured. Demolition can start under the floor 2.4 Benefits of reverse construction of Seg Plaza 2.4.1 Reverse construction adjusts the overall progress of high-rise building construction, adjusts most of the underground engineering operation time beyond the key lines, and advances the above-ground engineering. Start construction in the next day to achieve the goal of shortening the total construction period.
2.4.2 It is conducive to improving site utilization in projects with extremely narrow construction sites. After the construction of the first floor, within the range of 7430 and 2 of the first floor, about 23 sites can be used as temporary roads and temporary construction sites. The site has greatly eased the difficulties of the small construction site, so that the subsequent construction projects can be carried out smoothly.
2.4.3 The reverse method can reduce the support cost of deep foundation pits and reduce the engineering cost. If the earthwork excavation is done first, the underground continuous wall must be provided with at least 3 horizontal supports to dig to the depth of 18.25. The reverse method is adopted. After the construction plan, all the horizontal supports are borne by the formal structure.
3.0 Selection of cranes and plane layout 3.1 Since the owner divided the SEG Plaza project into two phases of construction, two tenders, and it is uncertain whether the two phases of the project will be continuously applied 3.1.1 Basement basement steel pipe column and the first floor steel beam single member The maximum size is medium 1600 pay, length 24.2 version, weight 27,60t. All lifting work is carried out on the original ground. The use of â‘´ 0t tire crane is mainly responsible for the lifting of 16 ï¿ 1600mm steel pipe columns; ⑵ 50t crawler crane is responsible for the lifting of all other components. 335t car crane auxiliary crane.
Amount of 12t; ⑵ Taiwan-made C7022 type attached tower crane with a maximum turning radius of 40m and a maximum lifting weight of 16t.
The crane base adopts artificial digging pile foundation, the base elevation is lower than the basement bottom elevation, and the crane is attached to the podium steel structure.
On the 72nd floor of the tower, the height of the roof helicopter apron is 291.60, and the plane shape is angular; the center distance of the outer frame column in the direction of the main axis on both sides is 40, 50mX40.50m, and the center distance of the inner cylinder peripheral column is 21.30mX18.80m.
The maximum weight of a single member is 161.
Because of the heavy workload of installing steel components, two cranes must be installed. In order to give full play to the working performance of the crane, both cranes must be arranged on the steel frame outside the core barrel.
The total height of the building has exceeded 300m. Only the internal climbing crane can be selected. Decided to adopt (1) M440D internal climbing tower crane produced by Australian FAVCO company as the main crane, with a maximum turning radius of 52.50m, a lifting weight of 8t, a maximum lifting weight of 161, a steel rope walk, a turning radius of 32.50, and two domestic 07022 type internal climbing The tower crane is an auxiliary crane with a maximum turning radius of 30.00 and a weight of 71. The maximum lifting weight is 16 and the turning radius is 15.0 at 150 empty installation and conversion positions, and after the completion of the tower, the large tower crane is at 350, 1 high altitude conversion position and removal; the first is How to reasonably design the tool beam system that supports tower crane climbing to make it the most reliable and convenient and the lowest cost; the first is that when two large tower cranes work on the steel frame, those adverse effects will be brought to the steel frame that has not yet formed a complete structure.
3.2.1 Tower crane installation and removal (1) The C7022 tower crane will complete the structural installation of the lowermost installation section of the tower in the early stage of the project; (2) The C7022 tower crane will install the upper and lower tool beam systems at the M440D position; All installation work; â‘·Remove H336B tower crane by M440D tower crane; remove 022 tower crane by 4400 tower crane, and transform 022 tower crane by installing 44 beam tower crane at new location 07022 tower crane tool beam system and tower crane tower construction after renovation After the completion, the specific method of tower crane dismantling is Shanyou, 400 tower crane dismantling 07022 tower crane after transformation, and restore 022 tower crane.
⑵ Install C7022 tower crane in the new location by M440D tower crane.
The 07400 tower crane will remove all 4400 tower cranes including tool beams.
By, 7022 tower crane installation platform is a fully assembled simple tower crane with a lifting capacity of 81.
The 7022 tower crane will be completely removed by the fully assembled simple tower crane, including the tool beam.
Finally, the fully-assembled simple tower crane support is released and put to the ground by an external elevator.
3.2.2 Climbing of tower crane and tool beam system phase engineering Two internal climbing tower cranes from the installation position upper clamping layer 15 to lower clamping layer 12; Times. There are 20 tower crane workstations. Each time the upper and lower clamping layers of the workstation are at a minimum height. 10, the maximum is 17.0 this. Meet the requirements of the manufacturer's instructions. Each climbing height of the tower crane is about 12m. It only takes 301nin time to complete.
The steel beam of the formal project cannot bear the load of the tower crane, and a special tool beam system needs to be designed to support it. It was decided to strengthen the steel corbel on the column of the relevant floor beam of each station during the climbing process of the tower crane so that it can bear the load of the tower crane and tool beam system. The floor beams remain unchanged. After the floor beam is installed, the tool beam is installed on the steel corbel as a support system for the tower crane. Place a 25-height steel beam pad between the tool beam and the steel corbel. In order to facilitate the reinforcement of the floor and the pouring of concrete, 3.2.3 Relevant calculation of the steel structure under the load of the tower crane. The structural characteristics of the SEG Square determine the construction sequence of the structure. The steel structure must be installed first, and then the reinforcement in the core tube can be constructed. Concrete shear wall. Therefore, during the installation of the steel structure, the lateral resistance system of the structure has not been fully formed.
The vertical load of the large tower crane in working condition is 186021 and the horizontal load of the clamping layer is less than 730, and there is also a torque. For the actual construction state, we carefully calculated the internal force and displacement of the structure under the load of the tower crane.
The calculation results show that although the reinforced concrete shear wall in the core tube has not been followed up, as long as the reinforced concrete wall between the floor structure and the peripheral column of the inner tube can be synchronized with the steel structure installation, the impact of the steel frame under construction on the load of the tower crane The maximum lateral displacement is only 3.57. During the construction, several actual observations were made. When the tower crane is working at full load, the top displacement of the concrete-filled steel tube column directly related to the tower crane is within 2.01. Now that the steel structure has been completely constructed, it has been proved that the functional configuration and layout of the two large tower cranes in SEG Plaza are reasonable; the design and climbing process of the tool beam system are advanced and applicable; the calculations related to the tower crane load are basically correct . Therefore, the entire working state of the two tower cranes is safe and reliable. These conditions provide a basic guarantee for the smooth construction of the steel structure of SEG Plaza and ensuring the achievement of the construction period goals.
4.0 Steel structure construction technology 4.1 Compared with the general high-rise steel structure, the steel structure of the SEG Plaza project has the following main difficulties. 4.1.1 In the structural system, the SEG Plaza project belongs to the frame tube structure. But the inner cylinder does not use the usual reinforced concrete cylinder body, but uses 8 steel tube concrete columns on each side, and a framed cylinder wall composed of welded solid web steel beams. There are 4 stiff concrete shear walls in the cylinder along the two main axes. The construction sequence must be the steel structure installation before the shear wall can be constructed. Therefore, in the structural installation stage, there is neither a reinforced concrete cylinder nor a reinforced concrete shear wall. From the outer frame column to the inner cylinder column, from the inner cylinder column to the inner cylinder shear wall type steel skeleton, the complete structure is not formed. The installation and connection of steel components, in particular, did not form an effective anti-side force structural system.
4.1.2 Because the inner frame and outer frame are all steel tube concrete columns, there is only the steel frame of the stiff concrete shear wall in the tube, so the reference of the control measurement can only be transferred to the steel structure, and all the measurement correction work can only be done on the steel structure. It is carried out above, and after the steel beam is installed, the correlation between the steel pipe columns during the measurement and calibration is relatively strong.
4.1.3 Whether the steel pipe column is formed by ordinary coiling process or spiral coiling, the error form of the cross-sectional size is now ellipticity and circumference. Because the wall thickness of the steel pipe is 14, 28, when installing, the upper and lower column sections are The error handling at the interface is mainly to prevent wrong edges, and it is difficult to adjust the axis installation error. SEG Square has many beam axes that are not orthogonal to the cylinder, especially the center of the steel pipe is non-intuitive, so the positioning of the steel pipe column is mainly based on Rely on the datum bus marked outside the steel pipe column. Therefore, the reference bus control method is mainly adopted in the installation and measurement of the steel pipe column. Since the bus bar outside the circular steel pipe will be skewed with the torsion of the steel pipe column, this kind of reference bus bar skew must be from one direction during the measurement and correction Observation can be eliminated.
4.1.5 All beam-column joints at SEG Plaza are connected by beams and steel corbels on both sides of the column. The web is bolted with high-strength bolts, and the upper and lower flanges are fully penetration butt welded. Steel corbels on the upper, middle and lower layers of the round column, each layer is usually a steel corbel in 4 directions, and a few steel corbels in 5 directions. The centerline of some beam steel corbels is not orthogonal to the cylinder. There are also long corbels used in the inner cylinder column. Two long steel corbels adjacent to the column are connected in the middle, and bolt welded joints are also used. This kind of node structure has high requirements on the accuracy of component fabrication and installation correction.
4.2 In view of the above characteristics, in addition to following the general high-rise steel structure installation technology, the installation of the steel structure of SEG Plaza mainly adopts the following technical measures. 4.2.1 On the construction sequence, fully adapt to the structural characteristics, construct the outer frame first, then the core tube, The whole project tower is divided into 5 pipeline operation areas, of which the outer frame is divided into 4 operation areas for continuous pipeline operation. The operation sequence of each zone is installation, correction, welding and inspection. The core barrel steel skeleton is the 5th running water section, allowing the construction progress of the outer frame to be properly lagging behind.
42.2 In terms of measurement, the whole investment and sub-control technology is mainly adopted. The whole investment refers to the overall control of the measurement control network from the base level to the operation layer and the closure detection before starting operation in each installation section and floor, and then in the previous installation section The top of the column and the control axis of the projection plane are used as the basis for the measurement and correction of this installation section. Sub-control means that in the flow operation, the measurement and correction of the frames outside each zone are carried out independently.
4.23 In the aspect of calibration, it mainly adopts the unit calibration technique. The so-called unit refers to a pipeline operation area on the basis of a single steel pipe column initial calibration, all the steel beams of the pipeline section are installed with temporary installation bolts. Then change the strong bolts for initial tightening, and then start the symmetrical correction from the running section to both sides. And complete the final tightening of high-strength bolts.
4.2.4 In terms of welding, in addition to following the conventional welding process requirements, such as strictly implementing the welding sequence and symmetric welding, the reserve shrinkage and other measures, the main setting scheme is adopted. That is, according to the construction flow sequence, a spout is set at the end of the beam at the boundary between the flow areas. In principle, the above-mentioned movable mouth should be welded after the steel structure of the flow section is completely installed.
The welding sequence of the frame is the top beam-column node in the vertical direction, the middle beam-column node part and the beam-column node, and the upper and lower column segments connect the nodes.
In the floor plan, it starts from the center and moves symmetrically to both sides.
4.3 The installation of the steel structure of the SEG Plaza started on January 12, 1997. By 418 days in 1999, it had been capped for 820 days. A total of 16543 steel structures were installed with a total weight of 2259; 60,000 welds, 104,303 profiled steel plates, 565,275 ruthenium welding bolts, and 239,350 sets of torsion shear high-strength bolts were installed. The installation quality is excellent. , The rate of secondary flaw detection is 98.85; the rate of passing inspection is 1. Before the installation of the 10.9 grade torsion-shear type high-strength bolts, a total of 24 sets of friction surface anti-slip coefficient tests were carried out. The average anti-slip coefficient 0.4 satisfies the design requirements of not less than 35, and 8 groups of high-strength bolts were re-examined. The test, all meet the requirements of the specification, the installation inspection qualification rate is 1; the main inspection items of the interlayer verticality deviation axis displacement of the steel pipe installation are 1 cents, the elevation is 291.60, and the maximum vertical deviation of the steel pipe column top is 1. 7 paintings, far less than the standard allowable deviation of 50 awakening.
5.0 Development and application of high-throwing and vibration-free self-compacting concrete technology A total of 86 concrete-filled steel tube columns were arranged in the basement of the SEG Plaza and the podium, and the diameters of the steel tubes were 016000 00, 900 and 800. The tower was equipped with 44 concrete-filled steel tube columns. The diameters are 51600000 and 0 800 respectively. The strength grade of the concrete in the steel pipe is 060050 from bottom to top. The installation section of the steel pipe column is 3 floors, so the secondary pouring height of the concrete in the pipe is about 12, or so.
In the past, the column core concrete casting process of the concrete-filled steel tube structure has mainly used two types of methods. The first type is the traditional vibrating pouring method, and the first type is the non-vibrating pouring method. In the vibrationless pouring method, it is divided into two types: the high-level drop method and the pumping jacking method. The former uses the kinetic energy of high-level drop of concrete to achieve the compaction of the concrete, and the latter uses the concrete formed under pressure to achieve the concrete Dense.
The main disadvantage of the first method is that the quality of concrete is significantly affected by human factors and the construction defects of concrete cannot be exposed. The main disadvantage of the first method is that the test block reflecting the strength of concrete and the forming method of the structural body are different, which affects the credibility of the assessment of concrete strength. The common feature of the above two methods is that the density of concrete depends on the construction methods on site.
After the construction of the SEG Plaza project began, the column core concrete was still cast using the traditional method of layered topping and layering to ensure the compactness of the concrete.
In order to ensure the quality of the concrete in the pipe, various measures have been taken. However, due to the small operating space in the steel pipe, the poor working environment, the labor intensity, and the human factors that affect the quality of the concrete, it still cannot be completely eliminated.
In order to solve the difficulties in the construction of concrete-filled steel tubes, the China Construction Bureau, in cooperation with the Building Materials Institute of the China Academy of Building Research and Shenzhen Neihengshan Concrete Co., Ltd., jointly developed high-throwing and vibration-free self-compacting concrete technology.
5.1 Development Purpose Use local raw materials to develop suitable for regardless of the size of the pipe diameter, using direct throwing and sub-casting molding, without using mechanical vibration, can ensure that the quality of the concrete core column after pouring reaches the mechanical vibration of conventional concrete quality.
5.2 Performance evaluation methods and performance indicators of high-throwing self-compacting self-compacting concrete The slump degree and the degree of collapse expansion are used as important indicators for controlling the performance of self-compacting self-compacting concrete mixture without slumping. Use the 20-meter to do the filling test of the concrete mixture and require it to reach the filling index; use the type-flow meter to do the fluidity test and require to reach the liquidity index to pass, type, and the content of coarse aggregate in the left and right two chambers after the test To determine the segregation resistance of concrete mixtures, and the weight difference between the left and right cavity coarse aggregates is required to meet the segregation resistance index of 0. 7 5.3 Division of development stage and results The development of high-throwing and vibration-free self-compacting concrete is divided into the following In the phase, raw material selection and performance comparison test phase are carried out, mix proportion design phase and simulation test phase.
5.3.1 In the preliminary selection of raw materials and performance comparison test phase, different water-cement ratios were first determined, and then the expansion of cement paste was tested at different admixtures according to the selected cement and admixture. Through experiments, some important parameters were determined.
5.3.2 Concrete mix ratio design stage The concrete mix ratio design is carried out in stages, namely the mix ratio exploration test stage, the optimization test stage and the verification test stage.
The mix ratio exploration test phase is based on the above raw material preliminary test research to make concrete test mixes. Under the same mix ratio, compare the performance of various raw materials made of various raw materials, so as to select both It can meet the various technical requirements of vibration-free self-compacting concrete, and can make the concrete cost the most ideal material. At the same time, it can also initially determine the concrete mix ratio. The optimization test stage is mainly for the admixture of sand to water and cement ratio. The main parameter of volume is used for optimization test, and the optimized concrete mix ratio is proposed.
In the mix ratio verification test stage, the purpose of the verification test is to verify the reproducibility of various properties of concrete with a specific mix ratio. The mix ratio verification test was conducted in two. The first verification test is to verify the reproducibility of the filling and fluidity in each plate according to the characteristics of vibration-free self-compacting. The first is to verify whether the strength of the preparation meets the specified requirements. 53.3 Simulation test The first simulation test confirmed that the high-throwing and vibration-free self-compacting concrete mixture has a high degree of fluidity, filling resistance, segregation resistance and plastic retention performance; The quality of the steel tube concrete poured by the method of high-throwing and pumping vibration-free construction is reliable, and the concrete strength level meets the requirements of 60.
In the first simulation test, a reinforced ring plate was set in the cylinder, and the pumping high-throwing method and hopper high-throwing method were used for casting and forming, and the high-throwing height. , 1600 cylinder adopts pumping high-throwing method, 800 sundial cylinder adopts hopper high-throwing method from concrete mixing completion time 230 to 530 pm, after 3 hours, the concrete slump still maintains 27. 1 Whether pumping high The result of the throwing method or the hopper high throwing method is very ideal. The concrete on the surface of the reinforced ring plate is also very dense, without leaving any holes, and the test is very successful.
Two simulation tests with the same conditions on site confirmed that the high-throwing vibration-free self-compacting concrete has excellent rheological properties and mechanical properties, and is suitable for casting concrete-filled steel tube core columns by pumping high throwing and hopper high throwing methods. The performance of the formed concrete is considered to be highly homogeneous and high-strength high-performance concrete by the quality inspection of the relevant statutory quality inspection department. The simulation test also proves that the strength of the test block under the same condition and the strength of the concrete-filled steel tube core are highly consistent.
As long as the performance index of the concrete mixture meets the requirements and the high-throw construction is performed according to the set requirements, the strength of the maintenance test block under the same conditions meets the requirements. Can guarantee the quality of the concrete-filled steel tube core column. During the development of the test, the National Chengcheng Quality Supervision and Inspection Center was also commissioned to carry out a test on other mechanical properties of the concrete.
5.3.4 On the basis of the completion of the research and development of high-throwing and vibration-free self-compacting concrete, the quality standards of high-throwing and vibration-free self-compacting concrete were compiled. Technical documents such as construction technical regulations are used as temporary regulations during the application of high-throwing, vibration-free and self-compacting concrete to ensure the quality of the project.
The high-throwing, vibration-free and self-compacting concrete technology has improved the construction technology of the concrete-filled steel tube structure in China, which can reduce the labor intensity of workers, avoid dangerous operations in the pipe and artificial factors that affect the quality of the concrete, can effectively control the quality of the column core concrete, and accelerate the construction progress It has a wide application prospect in the construction of concrete-filled steel tube structural engineering.
The high-throwing and vibration-free self-compacting concrete technology was tested and applied in the first part of the SEG Plaza project by the Shenzhen Science and Technology Bureau after the technical appraisal.
6.0 Several site tests and test contents of concrete-filled steel tube structure Test purpose, to understand the joint working conditions and mechanical properties of concrete-filled steel tube columns under the weight of the structure and construction load during the construction process and their mechanical properties; to understand the reinforcement of beam-column joints The action and force transmission characteristics of the ring and the steel tube; understand the longitudinal deformation of the steel tube concrete outer frame column and core tube shear wall in the super high-rise steel tube concrete structure.
Test content Strain observation of the outer wall of the steel tube and core concrete in the concrete-filled steel tube column; observation of the strain of the reinforced ring and outer wall of the steel tube at the beam-column node; longitudinal strain observation of the reinforced concrete core tube wall and the concrete-filled steel tube column.
Observation of the actual structure is limited to the structure's own weight and construction load, so the total load magnitude is very small relative to the ultimate bearing capacity, and the measured data cannot reflect the stress-strain law of the whole structure of the structure, which brings great difficulties to the data analysis .
6.2 The number of measuring points and the arrangement of measuring points Test 6 concrete-filled steel tube columns, including 3 1600 columns, 0, 2 columns, and 800 columns, and observe longitudinal strain of the core concrete and longitudinal and hoop strain of the outer wall of the steel tube respectively , With 87 measuring points; 1 beam-column joint column to observe the strain state of the steel pipe and the reinforced ring, 28 measuring points; 1 column longitudinal strain observation, 1 longitudinal strain variable column, 2 longitudinal strain variables , Counting 29 measuring points.
6.3 Test instruments The main instruments are the 22 type static strain measurement and processing produced by Shanghai Huadong Electronic Instrument Co., Ltd., the 22 type conversion box and the corresponding strain gauge, and the auxiliary instruments are microcomputer precision power supply. 6.4 Data collection adopts a data collection method that combines main data and auxiliary data. The state of each construction layer is taken as a main data collection point. During the construction process of each installation section, the data after the completion of each flow section is observed in accordance with the sequence of the construction flow section as auxiliary data. So as to grasp the strain changes in the whole process.
After more than a year of continuous tracking tests and actual tests during two typhoons of 99089910 this year, a total of more than 50 observations were tested on 6 concrete-filled steel tube columns; loading and unloading tests under design loads were carried out on the nodes; The compression of the wall has been observed more than 20 times, and a large amount of actual measurement data has been collected. 3 65 Test results and analysis 6.5.1 Preliminary analysis results Since the test work is still in progress, the comprehensive analysis of all test data has not yet been done. After preliminary analysis, the following preliminary analysis results are obtained after preliminary analysis of the measured data.
An internal reinforcement ring is provided at the beam-column node, which can effectively transmit the horizontal force transmitted on the beam to the entire section and make the section sheared. Since concrete has a frictional grip on the inner reinforcing ring, it is beneficial to transfer horizontal shear force, which shows that it is a beautiful and effective method of strengthening the joint. The actual observations show that the beam-column joints have less strain under the design load, which indicates that the beam-column joints are safe enough. For such joints, a step-by-step experimental study is needed to better promote the application.
6 The stress-strain test of the concrete-filled steel tube structure is still in progress, trying to extend the test time as much as possible. In addition, in the SEG field, a sprinkling test was conducted on the temperature field of the concrete core of the concrete core of the steel tube under the construction conditions of welding and gas cutting.
The test results show that the above construction projects have very little influence on the column core concrete, n Xinxin. Hu Shide, Hou Junwei. High-rise building construction manual. Beijing State Construction Industry Press. 19 2 Han Linhai. Zhong Putong. Concrete-filled steel tube structure. Dalian Dalian University of Technology Press. 1997 Code for construction and acceptance of concrete structure engineering. Beijing; National Construction Industry Press, 1992 4 Steel Construction Engineering Construction and Acceptance Code 0850 called 595. Beijing Qianguo Construction Industry Extremity Society. , 5
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