It has been more than a century since the world-renowned architect Walter Gropius proposed the concept of prefabricated concrete buildings, and large-scale prefabricated concrete building practice has been more than half a century. It should be said that the structural connection technology of prefabricated concrete buildings is relatively mature regarding structural safety. From single-story and low-rise buildings to high-rise and super-high-rise buildings, from non-seismic fortification buildings to high-seismic fortification buildings, prefabricated concrete buildings have experienced the test of time and practice and created many classic success cases.
Today, I would like to briefly introduce the methods and technologies of "precast concrete structure connection", which has been the focus of everyone's attention and controversy, from a professional perspective through specific technical details.
Grouting Connection
Rebar sleeve grouting connection is a method of connecting steel bars by embedding a finished sleeve in a precast concrete component, inserting steel bars from both ends of the sleeve, and injecting grouting material.
The grouting sleeve connection is divided into full grouting sleeve connection and semi-grouting sleeve connection. The inner side of the upper part of the semi-grouting sleeve is threaded, the connecting steel bar is threaded, and the steel bar and the sleeve are connected by threads.
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| Full Grouting Sleeve Connection | Half-grouting Sleeve Connection |
| 1-connecting Steel Bar 2-grouting Hole 3-sleeve 4-grouting Hole 5-grouting Material | |
(1) The grouting sleeve connection can connect frame columns.
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| Schematic Diagram Of The Grouting Connection Of Steel Bar Sleeves In Frame Columns | |
| 1-Frame Column 2-Semi-Grouting Sleeve 3-Steel Bars | |
(2) The Steel Bar Grouting Sleeve Connection Can Be Used For The Vertical Connection Of Shear Walls
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| Schematic Diagram Of Shear Wall Steel Bar Sleeve Grouting Connection | |
| 1-Frame Column 2-frame Beam 3-Full Grouting Sleeve | |
2. Spiral Stirrup Grout Anchor Lap Joint
Spiral stirrup grout anchor lap joint is a pre-reserved hole steel bar grouting connection method that uses spiral stirrup grout to strengthen the reserved hole of the lap steel bar. After the reserved component is inserted, the steel bar part is added with a reserved hole, and the steel bar is inserted and grouting is connected. The outer ring concrete of the two overlapping steel bars is reinforced with spiral steel bars, and the concrete is constrained, so that the steel bars can be reliably overlapped.
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| Schematic Diagram Of Spiral Stirrup Grout Anchor Lap Connection |
| 1-Steel Bar 2-spiral Stirrup 3-Inserted Bar |
3. Corrugated pipe grout anchor lap connection
Corrugated pipe grout anchor lap connection is a steel bar grouting connection method that uses corrugated pipes to strengthen the reserved channels. The corrugated pipes constrain the steel bars inserted into the pipes and the grouting materials poured in, thus achieving the lap connection of the steel bars.
Post-cast Concrete Steel Bar Connection
1. Threaded Sleeve Connection
The threaded sleeve connection of steel bars can be used in prefabricated buildings. First, thread the steel bar and then screw it into the threaded sleeve to achieve the connection of the steel bar.
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| Schematic Diagram Of Steel Bar Threaded Sleeve Connection | |
| 1-Threaded Sleeve Joint; 2-Steel Bar | |
The threaded sleeve connection requires high positioning accuracy of the connected steel bar, which is difficult to apply in prefabricated components. However, the accuracy requirements can be reduced by the same transfer method.
2. Extrusion Sleeve Connection
The cold extrusion connection of the steel sleeve is a kind of steel bar connection method that inserts ribbed steel bars into the sleeve from both ends, squeezes the sleeve to deform the sleeve, and then realizes the steel bar connection. It can be used for frame beam-column steel bar connection.
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| Schematic Diagram Of Cold Extrusion Steel Bar Connection | |
3. Glue Injection Sleeve Connection
The steel bar glue injection sleeve connection is a steel bar connection method that inserts the ribbed steel bar into the sleeve from both ends and then injects a special gel to achieve the steel bar connection. It can be used to connect beams and beams. It is widely used in Japan.
4. Ring Reinforcement Binding Lap Connection
Ring reinforcement binding lap connection is a connection method in which the walls of the prefabricated integral shear wall structure are connected through cast-in-place sections (hidden columns). The two connected walls extend the ring anchor steel bars, which are tied and overlapped with the longitudinal bars and stirrups of the hidden columns, and the steel bars are connected after the concrete is poured.
5. Straight Steel Bar Binding Lap Connection
The lap form varies according to the seismic level and construction requirements of the structure. The non-reinforced part of the bottom of the first and second level seismic resistance, the third and fourth level seismic resistance, and non-seismic resistance can adopt lap (I), that is, 100% lap in a single section. This type of lap is mostly used for vertical reinforcement lap of columns and shear walls.
6. Straight Steel Bar Lap Connection Without Binding
Straight steel bar lap connection without binding is a connection method in which two steel bars are directly overlapped together without binding, and then concrete is poured to form the connection of the steel bars. The lap form varies according to the seismic grade and construction requirements of the structure. This type of lap is mostly used for vertical steel bar lap connection of composite slab shear wall and circular hole shear wall.
The close connection of the one-way slab and the connection between the composite slab and support also belong to the lap connection without binding.
7. Steel bar welding connection
Steel bar welding connection is a connection method that directly welds the bars together by butt welding or lap welding. Welding connection is mostly used for low-rise and multi-story shear wall structure connections.
Other Connections For Post-cast Concrete
1. Steel Anchor Ring Connection
Steel anchor ring connection is a connection method that uses steel anchor rings to insert reinforcement and then pour concrete. In the reserved groove on the connection surface of the prefabricated wall panel, a threaded sleeve is embedded in the reserved groove. When the wall is installed, the connection ring is screwed into the threaded sleeve, and then the reinforcement is inserted into the overlapping area of the connection rings of the two walls, and then fine stone concrete is poured to form a wall connection. It is mostly used for multi-layer shear wall connections.
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| Steel Anchor Ring Connection | |
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1-Prefabricated Wall Panel 2-Rebar 3-threaded Embedded Parts 4-Connection Ring |
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2. Steel Bar Anchor Ring Connection
The steel bar anchor ring connection is a connection method in which concrete is poured after the steel bar anchor ring is inserted. The steel bar anchor ring connection refers to a groove reserved at the connection end of a shear wall panel to be connected, and a steel bar anchor ring is extended from the groove. A groove is also reserved at the connection end of another shear wall panel to be connected. A steel bar anchor ring is also extended from the groove. Then the two wall panels are butt-jointed, the two grooves are opposite, and the gap is sealed with a sealing strip. The anchor ring steel bars are staggered to form a public space, two steel bars are inserted into the public space, and then fine stone concrete is poured to form a wall connection.
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Schematic Diagram Of The One-line Node Structure |
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| Schematic Diagram Of L-type Node Structure | Schematic Diagram Of T-type Node Structure |
3. Connector Loop Box Connection
The Connector Loop Box connection is a pre-buried steel cable ring on one side of the wall, which intersects with the pre-buried steel cable ring on the other side of the wall, and steel bars are inserted in the intersection area to form a steel bar connection. The two walls form a cavity at the connection part, and slurry is injected into the cavity for connection. Rope loop connection is mostly used in low-rise houses.
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Post-cast Concrete Connection Of Composite Components
1. Steel Bar Bending And Anchoring
The bending and anchoring connection of steel bars is a common practice when the length of the steel bar straight anchor is insufficient. It is widely used in concrete structures, such as the connection between two-way composite floor slabs in prefabricated concrete structures, the connection between composite beams and end columns, and the out-of-plane connection between prefabricated shear walls and composite beams.
Dry Connection
1. Bolt Dry Connection
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Bolt connection is to achieve the connection with prefabricated components by bolting. Bolt connection can set bolt holes and installation hand holes on the edge of the component, and pass bolts through the bolt holes to achieve a fastening connection. Bolt boxes or customized bolt connectors are used abroad to achieve connection. Bolt connection has a wide range of applications. It is suitable for assembled concrete frame structures and assembled concrete shear wall structures. It is also suitable for the connection between external wall panels and main structures and the connection between prefabricated floor slabs and prefabricated floor slabs.
2. Connector Welding Dry Connection
Connector welding connection is to achieve connection by welding different steel plate connectors embedded in concrete components. Welding is a non-wet operation and a simple and convenient operation. It can be applied to assembled concrete frame structures and assembled concrete shear wall structures.
Other Connections
1. Prestressed Dry Connection
Prestressed PC buildings convert the tensile stress that may occur in advance into compressive stress in design. The scattered PC components are firmly pressed together by prestressing, the compressive stress is between the components, and the stress-bearing surface is the entire contact surface. This structural system changes the existing construction practice of connecting various nodes by the wet cast-in-place method. In the structure above the ground, all wet operations such as node cast-in-place and floor slab superposition cast-in-place can be eliminated, which belongs to dry construction.
2. Combined Connection
The combined connection of steel and steel sleeve grouting is mostly used in frame structures. The specific form is shown in the figure below.
3. Cast In Channel Connection
The cast-in channel connection is suitable for the connection between large block masonry and structural columns. The specific form is shown in the figure below.
