Understanding Column Extensions Above Roof Slab for Future Construction
In the field of construction, column extensions above the roof slab are a common design element, often referred to as dowel bars or dummy columns. These extensions serve a crucial purpose in facilitating future construction without necessitating extensive modifications to the existing structure. This article aims to demystify the technical names and usage scenarios of these extensions.
The Technical Names of Column Extensions Above Roof Slab
Column extensions above the roof slab, when added to accommodate future construction without altering the current structure, are officially termed as dowel bars or dummy columns. These terms are commonly used in construction documents and building plans to indicate that these columns are not structural members and will not carry any load. Instead, they are designed to extend the building vertically in the future, allowing for additional vertical elements to be added without major disruptions to the existing structure.
Design and Functionality of Dummy Columns
Historically, dummy columns were made from concrete that had a lower grade than the main structure. The use of this lower grade concrete, often referred to as a lean mix, leads to porosity and potential rusting of the embedded steel when exposed to sunlight and rain. To mitigate this issue, modern construction practices now use the same grade of concrete as the main structure for dummy columns, ensuring better durability and resistance to rust.
Dowel bars, also known as dummy columns, can be further described as sections of rebar that serve a similar purpose. They are often covered with lean concrete to match the dimensions of the column and are designed to be removed during the construction of upper floors. This design allows for flexibility in future construction, as the dummy columns can be dismantled without compromising the integrity of the existing structure.
Challenges and Mitigation Strategies
While dummy columns are a beneficial design feature, they do come with their own set of challenges. One common issue is the extension of rebar above the concrete column, which can lead to the rebar resting on the floor and causing deformation. This problem is particularly problematic in scenarios where the rebar is not properly sealed or painted. To mitigate this, some constructors and engineers propose painting the extended rebar with a non-corrosive paint or epoxy to protect the steel from environmental elements and prevent rusting.
Conclusion
Understanding the technical names and functionalities of column extensions above the roof slab for future construction is vital for both construction professionals and building owners. Whether referred to as dowel bars, dummy columns, or column stumps, these extensions play a crucial role in ensuring that buildings can be extended in the future without significant modifications. By adhering to modern construction practices and addressing potential issues, constructors can ensure the longevity and integrity of these design elements.