The in-plane stiffness of precast concrete walls increases, resulting in increased precast building stability. Because of the combination of flexural and shear stiffness, they obtain more in-plane stiffness. Precast walls can be short or slim depending on the geometry. It is vital to examine for global in-plane buckling when considering slender walls for construction. These are caused by foundation flexibility or other second-order effects. Buckling caused by out-of-plane stiffness is prevented. However, the same verification must be done for at least a single-story height. The flexural rigidity of the narrow precast concrete walls is dominant, and they are sometimes referred to as shear walls. This is due to their greater capacity to withstand horizontal forces.
Precast Walls’ Structural Actions
To enhance overall structural behaviour and stabilisation of the building, a correct interaction between the precast floors and the stabilising shear wall is critical. Only if the link between the floors and the precast walls is properly connected will proper interaction be facilitated. The interplay of wall elements aids in delivering diaphragm action to the joints, allowing for transfer to shear and tensile joints. This emphasises the significance of good joint design. The strut and tie models are used to comprehend the overall arrangement’s equilibrium system. The joint is designed to provide the desired structural behaviour.
When compared to precast floor diaphragms, precast concrete walls are subjected to higher axial loads and stresses. The stiffness of shear walls is an important characteristic. The stiffness of the wall structure will be affected if a fracture forms in the wall. As a result, the design must be done in such a way that no tensile stresses are allowed in the horizontal joints of the wall, or that only minor tensile stresses are allowed. The most cost-effective way to alleviate tensile strains on the walls is to increase vertical loads on the walls. Precast Concrete Walls’ Structural Actions shows the behaviour of a shear wall under horizontal and vertical loads. The elements should be connected as much as possible.
Cast-in-Situ Concrete Joints
The walls used in precast shafts can be configured as isolated shear walls or joined vertically. As a result, a closed or open cross section is formed. As a result, the shaft will function as a single, stable system. Connections along the vertical joints are required to incorporate wall contact into the system. This is done to counteract shear forces. Interacting Precast Wall Units for Stabilization Interacting Precast Wall Units Stabilizing Units The Precast Wall Units Are Connected Welding and concrete-filled joints are the most prevalent methods of connecting. The interlock pieces provide another way to link. The shear capacity of these interlocking connections is usually larger. In the connection, there is a distortion.
The transverse reinforcement in the cast in situ concrete connection offers continuous shear transfer along the joint. Plain or castellated concrete might be used to fill the cavity. The horizontal joints can have well-distributed or intense transverse reinforcement. When the difficulty of using them at corners is taken into account, they are more stiffer and stronger than welded connections. Welded Attachment Shear force is transferred intermittently through the welded connection. When they’re mounted together as a stabilising system, they get to work. These connections necessitate fire resistance, increased durability, and a high-quality finish. Welded connections can be protected by painting or grouting. When compared to concrete or interlocking connections, these are less stiff.
The Precast Wall Units
The establishment of the facade elements is aided by the use of standing multi-story wall elements or the laying of storey height wall elements. These pieces have the ability to carry vertical loads or act as a non-bearing cladding. Both of the above categories can be built as shear walls or as non-shear walls. To function as a shear wall, the connection must be linked in such a way that the shear force is transferred. If no transference is required, only a non-structural filling as a means of climatic protection is required. The Precast Wall Units Are Connected Alternative layouts for the Facade pieces are shown in Arrangement of multi-story standing wall elements Layout of single-story wall elements Examples When a structure has both, it’s a win-win situation.
You must evaluate the influence of the column connection on the whole construction process while making this type of connection. There are four different types of foundation to column connections. Socketed connection- For low-rise precast buildings, this will offer a fixed base connection to the precast column. The column’s cantilever motion provides lateral stability for the structure, eliminating the need for horizontal and vertical bracing. Overturning moments in the column will be resisted in this case by properly embedding the column in the concrete socket. The bolted or base plate connection between a column and a footing is designed to withstand tension, compression, and shear. It’ll be ideal.
Wall panel to foundation connection
To ensure correct positioning, set the overall size of the base plate slightly less than the column measurements. Mechanical splice connections are a type of moment connection used to prevent overturning. Moment-resisting column splices, cantilever columns, and wall panels all require these types of connections. It’s employed in situations when columns that are part of a column-beam framing system need to be secured at the bottom. Because the bedding joint and grouting sleeves are filled with grout, this form of connection can be treated similarly to in-situ connections. Dowel bars can be pushed upward from the base or downward from the column in this case.
The load-bearing walls are connected to the foundation via these types of connections. Any connection that connects a wall panel to a foundation wall or a continuous footing should allow the panel to be levelled and aligned. The base shear should also be able to be accepted in either direction by the attachment mechanism. The embed edge distances and other design assumptions that should pass production and design standards are the capacities of these connections. The connection is not sensitive to tolerance. To allow the loose angle and accompanying welds, the embed plate and recessed pocket plate must be correctly proportioned. In the precast concrete final, perimeter bars serve as a form of confinement. The centerline of the connections must be at least 60 mm from the precast’s edge.
Beam to column connection
Moment-resistant connections between beams and columns at the corners of frames or a moment-resistant connection to elongate beams are provided by beam-to-column connections. The beam to column connection’s configuration and response, which includes strength, rotational stiffness, and ductility, has a variety of effects on buildings. Both dry and wet connections are possible. They can be divided into two sorts when it comes to dry connections between beam and column. Type one cones have a continuous vertical member, while type two cones have a discontinuous vertical part. Type one is further divided into hidden connections, visible connections, and visible and visible connections. Beam-ends lying on top of columns and continuous beams fastened at the top of columns are two types of type two.
The major function of the column to column connection is to prevent panels from bowing and/or to transfer vertical shear force between panels. Due to the grout coating over the connection, the connection is corrosion resistant. Splice connections and anchor bolts are used in this sort of connection. Splice connections can be constructed to mimic the features of monolithic cast-in-place concrete and are utilised for both interior and external column to column connections. When the actual column length is limited due to production and handling constraints, this connection is used. To accommodate future growth, a splice connection is also used. This enables connections to be made with regularity. In multi-story constructions, anchor bolt connections can be used. The design of the base plate is similar to that of a typical column base.
The connections are usually made by placing a loose plate between two structural steel plates.
Typically, each precast panel is connected to the next or other building structure with metal components and anchors.
In precast structural connection design, the key variables are strength, volume changes, ductility, durability including fire and corrosion.