Precast connections for safe building
Precast connections ensure safety and durability of a precast building. They carry the predefined loads in different building structures and resist fire and water. Industrially produced precast connections are fast and easy to install no matter what the precast product.
Precast is a modular building system based on components and connections. Some type of a precast connection is needed between each produced precast unit. Demands for precast connection types vary among different precast products, local building conditions and restrictions, and loads on the structure. Generally every country has its own system for precast connections. There are several pre-tested connection types for precast floor products, and seismic and support connections.
Precast connection design
Typically precast connections can be done with an industrially produced connection part, wet connection, bolt, or weld connection. In precast connection design the key variables are strength, volume changes, ductility, durability including fire and corrosion, simplicity in production, installation and maintenance, temporary loading conditions, economy and appearance.
Precast buildings suit well for hot, cold and also seismic areas, when the specific local requirements are taken into account in connection design. If planning a building for a seismic area, it is recommended to involve seismic connection design experts into the process.
Precast floor connections
There are several pre-tested connections for hollow-core slab floors. Hollow-core slabs are normally installed on neoprene strips, that can also be used as part of the final connection. Neoprene strips ensure a uniform bearing of floors.
Connections at longitudinal joints are used between the edges of the hollow-core floor unit and beams or walls running parallel with the floor. Their main function is to transfer horizontal shear on the precast units.
Specific precast connection sample drawings can be found for
- HC slab on rectangular beam
- HC slab on rectangular edge beam
- HC slab on concrete wall, wall-to-wall connection
- HC slab on sandwich wall
- HC slab on wall corbel
Precast connections for sandwich walls
Connecting loops, ties and fixing sockets are common safety solutions, when building with sandwich walls.
Connecting loops connect the vertical joints of precast wall panels to each other. They are single-wire loops, which can be applied on wall-to-column joints as well. Connecting loops are easy to install by opening the wall cover, bending the loops to the operating position and connecting them to reinforcement.
Ties connect a facade and an inner panel of a sandwich wall together. They are a connecting reinforcement of the wall including outer, inner and diagonal bars forming a lattice-type of ties. Outer and inner bars can be either normal or stainless steel, whereas diagonal bars are always of stainless steel.
Fixing sockets are used for attaching and fixing objects to precast concrete such as guard rails, lighting fixtures, etc. Their main function is to carry axial load.
Joints of the outer layer of the sandwich wall
Main variables of a high quality precast wall are ventilation in sandwich structures, water resistance and outlook. Most of the precast wall problems are caused by the joint deformations in the outer layer of facades and sandwich walls due to temperature and moisture variation.
The right use of wall joints is essential to prevent these problem. Good wall joint material withstands stress caused by thermal movement in the units, solar ultraviolet and infrared radiation, external air temperature and impurities. Joints should be designed so, that they prevent rainwater entering between precast unit and the insulation.
The key in a sustainable wall joint construction is provision of solid and smooth adhesion surface for the jointing mass in the edges of the wall units. By changing surface material, texture or color at the joints, it is possible to form surfaces, where junctions are seen as a natural parts of the facades.
Leave us a message ›