Joint designer

Joints can be formed by the construction process or the function within the structure. We distinguish five types of joints:

• A working joint (also known as construction joint or day joint) is the separation of two concreting sections in the construction sequence. The joint itself does not fulfill any function and is problematic from a structural point of view and for reasons regarding water tightness of the structure. It is characterized by continuous reinforcement and should generally be structurally designed as a monolithic member.
• The control joint (also known as controlled crack joint or contraction joint) permits restricted shrinkage of the adjacent concreting sections. In particular, during the curing process, stresses in the concrete can thus be selectively introduced into a controlled crack. The cross-section of the concrete component and the reinforcement are weakened in the predetermined crack joint. Waterproofing barriers, included in crack inducers, are frequently used to prevent water penetration.
• The expansion joint (also known as isolation joint) allows more significant movements in case of expansion due to temperature differences, shrinkage or different settlements of the members. This is made possible by interruption of the reinforcement in the joint. This raises the challenge of load transfer between the structural members, which is often solved with shear force dowels.
• The sound insulation joint is characterized by the function of sound reduction. This is particularly relevant for concrete components that are exposed to impact sound.
• The settling joint (also known as settlement joint) creates a deliberate material-free gap to prevent load transfer to a concrete component or the ground below.
  

Joints can occur in different parts of the structure and have corresponding geometries:

• Slab/slab: joints within slabs
  
• Wall/wall: joints between two wall sections.
• Slab/wall: transition from a slab to a rising wall.
• Wall/slab: transition from a wall into a slab.
  

The transmission of transverse or shear forces in joints takes place via different transmission methods. The decisive factor for the shear force transmission is the joint surface, geometry or bearing.

• Rough joint surface: Surface category according to Eurocode 2 (DIN EN 1992-1-1, edition 2011-01, section 6.2.5).
  
• Joint surface indented: Surface category according to Eurocode 2 (DIN EN 1992-1-1, edition 2011-01, section 6.2.5).
  
• Joint reinforced: The shear force is essentially transferred by the reinforcement passing through the joint (e.g. by means of a continuity strip or screwed connection).
  
• Joint for displaceable shear force: If movement is to be enabled within the joint, a continuation of the normal reinforcement is not possible. Instead, reinforcement elements with force transmission allowing movement must be designed. This is possible, particularly with shear force dowels.
• Joints at horizontal bearings:Horizontal joints, especially between stairs and landings, often have specific requirements, especially for impact sound insulation.
  

The joint design is a specific challenge, especially for waterproof structures (WU). Joints - in particular predetermined crack joints and expansion joints - are needed to control stresses within the concrete and to prevent cracking. On the other hand, joints increase the risk of water ingress - which can be minimised in the following ways:

• Without waterproofing: Only suitable for joints without waterproofing requirements.
• Coated metal waterstop: The metal sheet provides a barrier against water penetration. The special coating ensures an increased bond between the concrete and the metal waterstop. This adhesive barrier prevents ingress around the waterstop.
• Coated metal waterstop JGS: Resistance to chemical attack is crucial, especially for the agricultural sector when constructing manure and silage containers.
• Metal waterstop: A metal waterstop is widely used for infrastructure projects.
• Rubber/PVC Waterstop: Waterstops made of PVC or rubber are also a physical barrier. The elasticity characteristic is particularly necessary for expansion joints.
• Injection hose / expanding waterstop: Further joint sealing can be carried out during the project lifecycle using resin or cement slurries injected into a hose, or via swelling materials (expanding waterstops).