Serviceability requirements are a crucial aspect of foundation design and construction. They are a set of conditions that determine whether a foundation structure is considered useful for its intended purpose. These requirements complement the strength requirement, which determines the structural soundness of the foundation.
Even if a foundation structure is structurally sound and performs well, it may still be deemed unfit for use if it does not meet the serviceability requirements. The purpose of serviceability requirements is to ensure that a foundation can adequately handle service loads and exhibit satisfactory performance.
Some of the common serviceability requirements for foundations include settlement, heave, tilt, vibration, lateral movement, and durability. Meeting these requirements is essential to prevent issues such as aesthetic problems, decreased usefulness of the structure, and higher maintenance costs.
In summary, meeting serviceability requirements is critical to ensuring that a foundation structure can perform well and remain useful over time. By taking into account factors such as settlement, heave, tilt, vibration, lateral movement, and durability, designers and builders can create foundations that are not only structurally sound but also meet the needs of their intended use.
1. Settlement
Settlement is a phenomenon where a foundation structure moves downwards as a result of the loads it bears. The extent of settlement should be kept within the acceptable limits, which are typically specified by relevant codes, to meet the foundation’s most important serviceability requirements.
The allowable settlement for office buildings, for instance, can range from 12mm to 50mm, with 25mm being a commonly permissible settlement. Similarly, for heavy industrial buildings, the acceptable settlement limit may vary from 25-75mm. In the case of bridges, the permissible settlement is 50mm.
Overall, it is crucial to maintain settlement within the prescribed limits to ensure the stability and safety of a foundation structure. Any significant deviation from the allowable settlement can lead to structural damages or even catastrophic failures, which may pose serious risks to human life and property.
2. Vibration
Foundation structures can experience intense vibrations when they support heavy machinery. To prevent any issues such as resonance, it is crucial for the foundation structure to be capable of absorbing these vibrations. This is especially important when supporting highly sensitive machines.
In instances where sensitive machines are supported by foundations, it is essential to use proper techniques to isolate the machine from the source of vibration. This can involve isolating the machine from the vibration itself or implementing base isolation for the foundation structure.
By taking these precautions, it is possible to ensure that the foundation structure and any machines it supports remain stable and secure, even when subjected to significant vibrations. This is crucial for maintaining the safety and functionality of these structures over time.
3. Lateral movement
The foundation structure of a bridge can be subjected to various types of lateral loads, such as shear and moment. As a result of these loads, the foundation can experience horizontal deformation or movement. It is essential to ensure that this lateral movement is kept within tolerable limits to maintain the structural integrity of the bridge.
To prevent any potential damage or collapse, the maximum tolerable lateral movement for bridges has been determined to be 25mm. This means that any horizontal deformation or movement of the foundation structure should not exceed this limit. By adhering to this standard, the safety of the bridge and the people using it can be maintained.
4. Heave
Heave is a phenomenon that occurs when the foundation of a structure moves upward due to the swelling of expansive soil. It is important to consider heave during the design and construction phases of a building, just like settlement. Failure to do so can have detrimental effects on the stability and safety of the structure. Therefore, it is crucial to account for heave and take appropriate measures to prevent or mitigate its effects. This can involve using specialized foundation designs, incorporating drainage systems, or treating the soil with chemicals to reduce its swelling potential. By taking these precautions, the risk of heave-related damage can be minimized, ensuring the long-term stability and safety of the structure.
5. Tilt
When a foundation experiences heave or settlement on only one side, it can cause the superstructure to tilt. An example of this is the Leaning Tower of Pisa, which has a tilt of approximately 1/10th. However, such tilts can be more problematic in taller buildings and should not exceed 1/500th from the vertical. This is because any greater tilt can negatively impact the aesthetics of the structure. As a result, it is crucial to carefully monitor and address any signs of foundation issues to prevent excessive tilting and maintain the overall integrity of the building.
6. Durability
The durability of a foundation refers to its capacity to endure and withstand the negative impacts of various environmental factors such as chemical, physical, and biological processes that could lead to deterioration. To enhance the foundation’s durability, various techniques can be employed, such as ensuring that the reinforcement has sufficient concrete protection, using chemical-resistant concrete, and insulating the foundation from aggressive agents present in soil and groundwater.
By designating adequate concrete protection for reinforcement, the foundation can be protected from the detrimental effects of chemicals, water, and other environmental factors that could cause corrosion and other forms of damage. Using chemical-resistant concrete, on the other hand, can significantly reduce the risks of chemical reactions and corrosion on the foundation, thus improving its durability.
Insulating the foundation from aggressive agents present in soil and groundwater can also improve its durability. This can be achieved by using various techniques such as coating the foundation with waterproofing materials, installing drainage systems to prevent the accumulation of water around the foundation, and using materials that are resistant to biological processes.
Overall, enhancing the durability of foundation structures is crucial to ensure their longevity and stability, especially in environments that are exposed to aggressive environmental factors. By adopting various techniques such as those mentioned above, the foundation can be effectively protected from damage caused by chemical, physical, and biological processes, thus prolonging its lifespan.