Keywords: Construction joints, dilatation, expansion joint, expansion unit, volume changes, uneven settling, rheological changes

The construction joint is defined as the distance between the two building blocks. This type of joint does not have the volume or shape changes - the gap is constant.

The expansion joint is a joint that divides buildings or their individual parts into smaller rigid units. Dilatation is performed to prevent transmission of non-force effects from one part of the structure to another so as not to interfere with the required functions.

The expansion joint is carried out in areas predicted extreme loads, loss of stiffness of the structure, structural changes, changes in the construction system and layout, in places of change of height of a structure or object, in places of geological breaks and irregularities.

Unforced effects include:

• Volume changes due to temperature
• Volume changes due to moisture
• Rheological effects (creep and shrinkage)
• Changing the shape of the foundation joint (bottom surface)

Unforced effects cause mechanical stresses in structures that often exceed the stresses due to common force effects (self-weight, wind load, etc.).

Splitting the structure of a building into individual components, which tend to vary in shape and different subsidence, is appropriate for reducing and reducing stress. Expansion units can be defined as smaller parts of the structure separated from the whole by expansion joints.

Expansion joints eliminate:

• Static effects - volume changes, uneven settling
• Dynamic effects - shocks
• Acoustic effects - noise transmission of structures and vibrations
• Heat-technical effects - Heat and moisture transfer of structures

Each material changes its dimensions with a change in temperature and humidity.

Volume changes can be caused by:

• Changing the temperature of the external and internal environment (thermal expansion of materials) - each material
• Changing the moisture of the materials (drying and swelling)
• Rheological changes of the materials
  • Shrinkage - Volumetric changes due to drying of water from the structure of solidifying and hardening concrete, shrinkage depends on the composition of the concrete mixture, its processing, dimensions and reinforcement of the elements.
  • Creep - volumetric changes due to the load size and the time depends on the composition of the concrete mixture, its processing, and the dimensions of the reinforcement element, load size, load type (permanent, accidental, dynamic) and the time of the load.
• As a result of chemical processes in materials (eg corrosion)

• Element breakage by tensile cracks
• Compression element failure
• Expanding effect on surrounding structures
• Creation and expansion of joints between element and surrounding structures
• Rheological changes of materials

Maximum distance of expansion joints in masonry with lime mortar:

• burnt bricks                          100 m
• sand-lime bricks                  50 m
• concrete blocks                   50 m
• natural stone                        60 m
• reinforced concrete             40 m

For plain or weakly reinforced concrete, the maximum lengths of monolithic expansion units for the protected structure are 30 meters and for the unprotected structure 24 meters. The maximum size of the dilatation units of the steel structure is determined by static calculation.

Construction design of the expansion joints:

• Duplication of supporting structures
• Unilateral sliding fit
• Cantilevered ceiling structure
• Inserted field with slide bearing

• Irregularities in the substructure of the object - irregular and oblique loading of soil layers with different compressibility, different levels of groundwater level, undermined area, additional changes in the subsoil or level of ground water level
• Different loads in the footing bottom - different height of the part of the building, different utility loads in different parts of the building, inappropriate design of the area of individual flat foundations
• Different foundation structures of parts of the building - the combination of shallow and deep foundations
• The time interval between the realizations of the different units of the building - the new part follows the older one, where the settlement has already taken place.

• Expansion joints must allow vertical displacements
• Expansion joints pass through the whole object, including the foundations
• Foundations must not interfere with one another
• Must comply with the required thickness joints

• Sided cantilevered horizontal structures
• Reversible cantilevered horizontal structures
• Fields inserted
• Modulation adjustment