Have you ever questioned how a building with a wide span can withstand an earthquake? The expansion joint that joins two substantial parts aids the structure’s ability to withstand earthquakes. Expansion joints divide long concrete slabs into several sections, preventing earthquake vibration from spreading to other building components. Due to expansion joints, the structure behaves as two or more separate structures during an earthquake. Expansion joints in buildings are commonly seen in a variety of structures, including ships, piping networks, sidewalks, and railroad tracks.
What is an expansion joint?
An expansion joint, also known as a movement joint, is an assembly created to securely hold parts together while safely absorbing vibration, temperature-induced expansion, and contraction of building materials, or to permit movement due to ground settlement or seismic activity. In layman’s terms, an expansion joint is a mid-structure separation intended to relieve stress on building materials brought on by building movement.
Why expansion Joint?
Due to warming and cooling caused by seasonal variations or other heat sources, building faces, concrete slabs, and pipelines expand and contract. These structures would crack under stress-induced conditions until no expansion joints were present. Expansion joints are created to fill the space and resume building assembly activities while accommodating anticipated movements.
Buildings typically have expansion joints to accommodate movements brought on by changes in temperature, moisture, ground settlement, seismic activity, etc.
Building cracks may form if there is any movement in a structure without an expansion joint and having a length of more than 45 meters (IS 456).
The main factors that cause movement in buildings at expansion joints include:
- Thermal expansion and contraction caused by temperature changes
- Sway caused by wind
- Seismic events
- Static load deflection
- Live load deflection
Characteristics of Expansion Joints | Expansion Joint in Buildings
- Expansion joints allow for thermal contraction and expansion without potentially exposing the setting to stress.
- An expansion joint safely accommodates the expansion and contraction of various building materials, dampens vibration, and enables soil movement caused by earthquakes or ground settlement.
- In most cases, expansion joints are situated between bridge spans, paving slabs, railroad tracks, and piping systems.
- The expansion joints are included to withstand the stresses.
- An expansion joint is a partition of sections made of the same material.
- The expansion joints are also known as control joints in concrete block construction.
- The following factors impact the building’s decision regarding expansion joints.
- Local temperature
- Humidity
- Climatic conditions
- Plan & Elevation of the building (dimensions)
- Building irregularities
- Miscellaneous topics
Expansion Joint Transitions
A sealed, secure, and energy-efficient building envelope requires transitions. When factory-fabricated transition assemblies are specified and installed, continuity of seal is achieved at changes in plane and direction, as well as between expansion joints.
By specifying expansion joints that tie into one another and are guaranteed for continuity of seal between like or dissimilar technologies, designers can now wrap the entire building envelope while also ensuring that life safety is addressed.
Passive Fire Protection at Building Expansion Joints
The building’s floors, walls, and ceilings are split in half by expansion joints, which also bisect the structure. If the expansion joint openings are not properly sealed with fire-resistive expansion joint systems, a fire in one room could quickly spread through them. In the past, to prevent heat, flame, and smoke from passing through these large structural openings, a fire barrier in the form of a fire blanket had to be looped into the joint opening. The management of expansion joints has been made simpler by the development of all-in-one water and fire-resistant expansion joints. In place of multiple systems, a single system can fire-rate, bridge, and seal joints.
How to Specify Expansion Joints in a Structure: Dos and Don’ts
Systems for allowing movement gaps in structures come in a wide variety of forms. For complete separation, expansion joints are present throughout every component of a structure, including its floors, walls, ceilings, and roofs (interior & exterior).
- Floor-to-floor
- Floor-to-wall
- Wall-to-wall
- Ceiling-to-ceiling
- Ceiling-to-wall
- Roof-to-roof
- Roof-to-wall
- Joints are generally not required on-grade floors
- Systems may or may not be waterproof
To accommodate the design movement, the gap should be as small as possible, and the expansion joint system’s size needs to allow for the full range of anticipated movements. For instance, a gap may expand and contract seasonally as a result of temperature variations; the joint system must stretch to fill the widest opening but also maintain its integrity as the gap contracts to its smallest size. Fire-stopping systems may also need to be covered or protected for expansion joint systems.
Things to remember
- Expansion joints are positioned where a slab meets a building, another slab, or a pool deck meets the coping.
- The joint cuts through every building assembly, including walls, decks, plazas or split-slab concourses, foundation floors and walls, roofs, planters, and green roofs, fire-rated demising walls and floors, interior floors, etc., because it bisects the entire structure. This space must be filled to restore the waterproofing, fireproofing, soundproofing, air barrier, roof membrane, trafficable surface, and other functions of the building elements it segregates.
- The location of expansion joints in a building is also impacted by the irregularities of the structure, including its mass, plan, stiffness, etc.
- When a building’s length is longer than 45 meters, concrete expansion joints must be used, possibly more than one.
References
Civil Engineering Web, 2021. What is Expansion Joint? [Online]
Available at: https://www.civilengineeringweb.com/2021/08/expansion-joint-for-building.html
[Accessed 6 9 2022].
EMSEAL, 2022. What is an Expansion Joint? [Online]
Available at: https://www.emseal.com/glossary-term/expansion-joint/
[Accessed 6 9 2022].
Rahman, F. U., 2022. Expansion joints in concrete. [Online]
Available at: https://theconstructor.org/concrete/expansion-joint-concrete/25161/
[Accessed 6 9 2022].
Schneeman, C., 2015. The Dos and Don’ts of Specifying Expansion Joints in a Structure. [Online]
Available at: https://walkerconsultants.com/blog/2015/11/30/the-dos-and-donts-of-specifying-expansion-joints-in-buildings/
[Accessed 6 9 2022].
Wikipedia, 2022. Expansion Joint. [Online]
Available at: https://en.wikipedia.org/wiki/Expansion_joint
[Accessed 6 9 2022].
