As a new type of building, the prefabricated building can effectively improve the construction efficiency, and has little impact on the surrounding environment of the construction, which is conducive to green construction. At present, in engineering construction, the factors affecting the safety of prefabricated building construction mainly include the omission of node design and structural design, the synergistic effect in the construction process is small, and the monitoring of construction quality does not meet the strict requirements of 100%. Let’s take a look at the points of attention in the prefabricated building. Let’s take a look.
1Assembled building management
Application RFID chip
Component manufacturers put RFID chips into their components, and use RFID technology to keep abreast of component production schedules and transportation information and assembly location information. This information helps to check the safety performance of the components at any time during construction and to identify safety issues. As the prefabricated building requires a large number of PC components, it is especially important to build the Internet of Things.
Apply BIM 5D
The application of BIM technology in prefabricated buildings mainly includes three aspects: construction site management, 5D dynamic cost control and visualization. Through BIM technology, the virtual layout and construction process of the building site can be carried out in the computer, and the secondary handling and the boom crossover can be avoided as much as possible. The 5D dynamic cost control of BIM can effectively optimize the construction period by stacking the virtual field materials and controlling the construction progress. Optimize resource allocation and control costs; use BIM technology to visualize technology and virtualize various construction processes, especially full-size 3D display of new technologies, new processes and complex nodes to make communication more efficient.
2 prefabricated building deepening design
Master the deep design requirements
(1) Detailed drawings of prefabricated components shall be drawn in accordance with the requirements for comprehensive design of various professions and production and construction. When there is a conflict in the detail drawing, it is necessary to point out the need for improvement so that the prefabricated component design can be modified in time.
(2) Check the detailed drawings of the prefabricated components to ensure that the requirements of the specifications are met to ensure compliance with the installation requirements. The construction party should understand the relevant national standards and specifications of the assembly type, and check whether the content and depth of the prefabricated parts production details meet the requirements of prefabricated component production, engineering quantity statistics and installation and construction requirements when deepening the design.
Completed deepening design content
(1) Exterior wall decoration finishes. When designing the exterior wall decorative surface, attention should be paid to the layout details such as tile, decorative concrete and stone. Note that the type and amount of materials should meet the design requirements. At the same time, the stone procurement should meet the requirements of aggregate strength and aesthetic appearance.
(2) Energy-saving insulation structure for external walls. The insulation structure should meet the requirements of the building function, pay attention to the selection of insulation materials and the selection of connectors, to ensure that the detailed layout is accurate. At the same time, the design performance should be checked and the design calculation verification process completed.
Prefabricated component production should pay attention to the link
(1) Production plan. The construction party shall timely participate in the design and adjustment of the production plan of the prefabricated components according to the requirements of the drawings to ensure the steady operation of the production and production of the components.
(2) Mold plan. The construction party shall ensure that the drawing design meets the construction needs, and according to the drawings, cooperate with the inspection of the mold plan to make problems, and propose amendments as soon as possible.
(3) Personnel organization. Arrange the quality control of the component production to ensure the strength is up to standard, the size is appropriate, and the look and feel is appropriate; the person should be responsible for communicating on behalf of the construction party and the component factory, timely feedback on the production situation, and conveying the construction requirements for the components.
(4) Technical quality control measures. The quality of the components has a great influence on the post-assembly and installation, and attention should be paid to timely communication with the component manufacturers. The strength of the component should be tested in time. If it does not meet the installation requirements, it should be redone in time; if the difference between the size and the actual requirement is too large, the manufacturer should be contacted in time to correct the deviation.
(5) Storage and transportation plan. On-the-go and reduced transport distances are a powerful guarantee for the savings in prefabricated installations.
3 assembly building earthquake resistance points
Compared with the traditional structure, in the case of strong earthquakes, the building with the cushion-type isolation device at the bottom of the floor will have a certain horizontal movement with the ground friction, and the relative horizontal displacement between the bottom of the house and the ground. In order to increase the period of self-vibration of the building, the lateral movement of the upper structure of the floor becomes smaller, which protects the building structure from the earthquake.
Sliding isolation is to use a smooth moving surface between the building and the superstructure foundation, and use a material with a small friction coefficient on the smooth moving surface to make a relative basic horizontal sliding when the building encounters an earthquake. To unlock the infrastructure and isolate the floor from the ground.
It is formed by replacing the rubber sheet and the thin steel plate, and the edge of the steel plate is retracted into the rubber to prevent the steel plate from rusting. The laminated rubber support can be further divided into a normal laminated rubber support, a high damping laminated rubber support, a lead laminated rubber support and a lead laminated rubber support. Because the lateral deformation of the rubber plate on the lower and lower sides is restrained by the rigid plate, the middle part of the rubber plate is in a three-direction pressure state under the vertical load effect, thereby forming a high compressive strength.
The high-rise isolation device is a means of combining the upper part of the structure and the seismic combination. It is a seismic isolation and energy-consuming device composed of the original structure mass and damping. When the earthquake occurs, the energy-consuming damping device absorbs and consumes energy from the seismic source. The descending structure is subjected to the earthquake. When the earthquake occurred, the support point suspended the entire building on a massive reinforced concrete structure. This suspended isolation method was called suspension isolation. Suspended isolation can greatly reduce the seismic forces on buildings, mainly for living buildings and public buildings.
(1) The thickness of the seismic wall is not less than 160mm and not less than 1/20 of the height of the layer. The thickness of the seismic wall at the bottom reinforcement is not less than 200mm and should not be less than 1/16 of the height of the layer, and the bottom reinforcement layer is 1~3 layers. The distance between the dark-column stirrups is 150mm, and the distance between the plum-shaped ribs between the double-row steel bars of the seismic wall is 400mm; on the other floors, the distance between the dark-column stirrups is 200mm and the tensile rib is 600mm.
(2) The vertical and horizontal distribution of the anti-seismic wall, the reinforcement ratio is not less than 0.25%, and the arrangement is double row, the distance between the reinforcement is not more than 600mm, and the diameter is not less than 6mm.
(3) The constraining edge members of the seismic wall include a dark column, an end column, and a wing wall.
(4) The stirrups shall be set within the length of the longitudinal reinforcement anchorage of the top joint beam.
In the event of an earthquake that has encountered seismic intensity in the region, in order to reduce earthquake damage, reduce and prevent secondary disasters as much as possible, building water supply and drainage, fire protection, heating, ventilation, air conditioning, gas, heat, electricity, communication Anti-vibration brackets shall be provided for electromechanical engineering facilities.
The construction of seismic support hangers mainly involves the use of anchors, reinforced booms, seismic joints, pipe joints, seismic braces, sections and fasteners. The following problems should be noted during construction: (1) All components that make up the seismic support hangers should be finished components to ensure that the construction quality of the support hangers meets the requirements; (2) Because the seismic support hangers are more concentrated in the basement, the basement is indoors humid. Environment, so when purchasing materials for anti-seismic hangers and hangers, comprehensive consideration should be given to factors such as price and quality.
4 assembly building construction points
Splicing joint of I-shaped section column
The splicing joints of the columns are generally just connected nodes, and the column splicing joints should be located outside the plastic zone of the frame joints, generally about 1.3 m above the frame beams. Considering factors such as convenient transportation and lifting conditions, the mounting unit of the column generally adopts 2 or 3 layers and has a length of 12 m or less. Depending on the specific conditions of the design and construction, the splicing of the columns can be done by welding or high strength bolting.
For weld joints in non-seismic design, partial penetration welds may be used, and the effective depth of the groove welds shall not be less than 1/2 of the thickness of the plates. For weld joints with seismic fortification requirements, full penetration groove welds shall be used.
The flange is generally welded for full penetration, and the web can be connected by high-strength bolts. When the column web is welded, the upper column has a K-shaped groove and requires penetration. The splicing joints of the box-section columns should all be welded, in order to facilitate the full-section penetration.
Welded joint of box column
When the box-shaped column in the high-rise steel structure is connected to the cross-shaped column in the lower-section steel concrete, the transmission of the force at the change of the section form should be considered. Part of the force of the box column should be transmitted to the concrete by the stud and the other part of the force transmitted to the cross column below. At the junction of the two sections, the web of the cross-shaped column shall extend into the box-shaped column to form a transition section of two sections. The length of the extension should not be less than the width of the column plus 200mm, and the section of the transition section is in the shape of a field. The transition section is under the main beam and closes the main beam.
Welding studs shall be provided above and below the joints of the two sections. The spacing and row spacing of the studs shall be 150mm, not more than 200mm, and the full height along the cross-shaped columns shall not exceed 300mm.
The splicing joint of the cross-shaped column in the steel reinforced concrete is difficult to be constructed by the high-strength bolt connection of the web in the cross-shaped section, and the flange and the web are preferably welded.
Secondary beam to main beam connection
The connection between the secondary beam and the main beam is usually designed as a hinge, the main beam serves as a support for the secondary beam, and the secondary beam can be regarded as a simply supported beam. The splicing form is as shown in the figure below. The vertical stiffening plate of the secondary beam web and the main beam is connected by high-strength bolts. When the internal force and section of the secondary beam are small, it can also be directly connected with the web of the main beam.
When the number of secondary beams is large and the span and load are large, the connection between the secondary beam and the main beam should be designed as a rigid joint. At this time, the secondary beam can be regarded as a continuous beam, which can reduce the deflection of the secondary beam and save steel.
Lateral bracing of the main beam
According to the seismic design of the frame beam, there may be plastic hinges on the beam (usually 1/10~1-8 beam span from the column axis), and the lateral couplings should be set on the upper and lower flanges of the beam. Lateral bracing can be calculated according to the axial compression member and should meet the slenderness ratio requirements.
Reinforcement of the opening of the beam web
When it is necessary to make a hole in the web of the beam due to the passage of the pipe, the beam should be reinforced according to the position and size of the hole. When the diameter of the circular hole is less than or equal to 1/3 of the beam height, and the hole spacing is greater than 3 times the aperture, and avoiding opening in the 1/8 span of the beam end, the reinforcement may not be strengthened.
When reinforcement is required due to the opening, the bending moment is borne by the beam flange, and the shear force is shared by the web of the orifice section and the reinforcing plate around the hole. The reinforcement of the circular hole can be reinforced by means of a casing, a ring-shaped reinforcing plate or a V-shaped stiffener on the beam web.
When the rectangular hole is opened on the web of the beam, the shearing effect on the web is large. The stiffening plate should be arranged around the hole. The length of the longitudinal stiffening plate extending through the opening is not less than the height of the rectangular hole. The width of the stiffening rib is the width of the beam flange. 1/2 of the thickness is the same as the web.
Frame beam construction
(1) The cross-sectional dimensions of the beam meet the following requirements: the section width is not less than 200 mm; the section aspect ratio is not more than 4; the ratio of the net span to the section height is not less than 4.
(2) The reinforcement of the beam shall ensure that the reinforcement ratio of the longitudinally tensile reinforcement of the beam end is not more than 2.5%, and the ratio of the height of the concrete compression zone to the effective height of the beam end of the compression steel is not more than 0.35. The ratio of the amount of reinforcing steel reinforcement on the bottom surface of the beam end section and the top surface is not less than 0.3.
(3) The length of the beam end stirrup encryption zone, the maximum pitch and the minimum diameter of the stirrup are adopted according to the specification. When the longitudinal reinforcement of the beam end is greater than 2%, the minimum diameter of the stirrup should be increased by 2 mm.
(4) The longitudinal reinforcement of the beam meets the following requirements: the reinforcement along the top and bottom of the beam is not less than 2φ14 and is not less than the larger cross-sectional area of the top and bottom longitudinal reinforcements at both ends of the beam. 1/4, the diameter of each longitudinal bar in the frame beam passing through the center column is not more than 1/20 of the cross-sectional dimension of the column in this direction.
(5) The distance between the stirrups of the beam end encryption zone should be no more than 250mm and 20 times the larger diameter of the stirrups.
5 assembly building inspection points
Prefabricated concrete structure inspection
The content includes general provisions, materials, components, and connections. It clarifies that the material inspection includes concrete, steel bars in the prefabricated components, post-concrete concrete, steel bars, and joint materials on site; component inspections should include prefabricated components. Defects, dimensional deviations and deformations, structural properties, etc. after field and installation; joint quality inspection between structural members shall include structural component position and dimensional deviation, sleeve grouting quality and slurry anchor lap grouting quality, weld joint quality The quality of the joint with the bolt, the quality of the joint grouting at the bottom of the prefabricated shear wall, and the quality of the cast-in-place concrete in the cavity of the double-sided laminated shear wall.
Assembled steel structure inspection
The content includes general provisions, materials, components, and connections. It clarifies the mechanical properties of materials including steel, welding materials and fasteners, chemical composition of raw materials, defects and damage of steel plates and fasteners, and metallographic steel. Content; component inspection should include component size, construction, deviation and deformation; connection detection should include solder joints, bolted connections, rivet joints, etc.
Assembled wood structure inspection
The content includes general provisions, materials, components, and connections. It is clear that the material testing items should include physical properties, chordwise static bending strength, elastic modulus, etc. Component testing items should include dimensional deviation, deformation, cracks, and corrosion protection. Insects, termites, etc.; connection testing should include bolting, toothing, splicing, ribbing, and metal fittings.
Other system testing
(1) The inspection of the external protection system includes general provisions, prefabricated exterior walls, exterior doors and windows, building curtain walls, roofing and so on.
(2) Equipment and pipeline system testing includes general provisions, water supply and drainage, heating, ventilation, air conditioning and gas, electrical and intelligent.
(3) The built-in system test includes general regulations, internal parts system, indoor environment and other contents.