Post Tensioned Slabs

Post Tensioning of Concrete Slabs and Beams

At Somers Engineering Limited, post-tensioning of concrete slabs and beams involves reinforcing concrete with high-strength steel strands or cables, which are tensioned after the concrete has been cast. This method enhances the structural capacity and durability of the concrete, allowing for longer spans, reduced material usage, and minimized cracking. By applying tension to the steel tendons after the concrete hardens, Somers Engineering ensures optimal load distribution and improved performance of the structure. This technique is particularly beneficial for large-scale commercial and industrial buildings, providing cost-effective and resilient solutions tailored to the specific needs of each project.

Owners, Developers, Architects, Engineers, and Contractors are demanding more from buildings today:

Cheaper
Flexible floor layouts: less columns & longer spans
Unique designs: irregular shapes
Faster construction
Sustainable design

Somers Post-Tensioned Slabs

Somers Engineering Limited utilizes post-tensioned slabs in repair projects to restore and enhance the structural integrity of existing buildings. This method involves introducing high-strength steel tendons into the concrete slabs, which are then tensioned to counteract loads and reduce deflection. By applying this technique, Somers can effectively address issues such as cracking, sagging, and general wear in aging structures. The post-tensioning process not only strengthens the repaired slabs but also extends their lifespan and improves overall performance, ensuring that the rehabilitated structures meet modern safety and durability standards. This approach is particularly advantageous for large buildings, where traditional repair methods might be less effective or more costly.

Somers offers post-tensioned slab systems for elevated slabs or slabs on grade. Somers Systems utilize DSI’s post tensioning systems for which their bonded strand post-tensioning systems are in accordance with European Technical Approval ETA-06/0022 and their unbonded monostrand post-tensioning systems are in accordance with ETA-03/0036.

Multi-Strand Bonded Flat Slab Systems

DSI bonded post-tensioning systems use multiple high-strength steel strands housed within a flat duct, with each strand typically stressed individually. The ends of the strands are anchored at two points: the live end and the dead end. The live end uses a DSI anchorage system, which secures the strands in place and allows for the application of tension. At the dead end, the strands are bonded directly to the concrete.

Once the strands are tensioned, the ducts are filled with a cement-based grout. This grout serves a crucial role by creating a continuous bond between the strands and the concrete through the duct wall. This bonding process ensures that the entire length of the tendon is integrated with the surrounding concrete, providing additional strength and stability to the structure.

After grouting, the system no longer relies solely on the anchors for maintaining the tension in the strands. Instead, the bond between the grout and the concrete distributes the forces more evenly across the structure. This characteristic is particularly beneficial in terms of damage resilience and flexibility for structural modifications. If a tendon is damaged or if changes to the structure are needed, the impact is confined to the local area of the slab. The rest of the slab remains unaffected because the bonded system ensures that the load is distributed throughout the length of the tendon, rather than being dependent on the anchor points alone.

This provides a system of strengthening concrete by tensioning the steel members and putting the concrete in compression. In traditional reinforced concrete the steel reinforcement remains inactive until the formwork is removed. In post tensioned concrete high tensile steel tendons are placed and stressed making the reinforcing steel active

Monostrand Unbonded System

At Somers Engineering Limited, the use of DSI unbonded single strand tendon systems in repair projects offers several advantages due to its flexibility and efficiency. This system involves individual high-strength steel strands, each sheathed in a protective coating, allowing them to move independently within the concrete slab.

Key Features of DSI Unbonded Single Strand Tendon System:

Quick Installation: The unbonded system is designed for rapid deployment. This is especially beneficial in repair scenarios where time is a critical factor. By reducing installation time, disruptions to building operations are minimized.
Flexibility in Design: Tendons can be easily deflected to navigate around openings or accommodate irregular slab shapes. This flexibility ensures that the reinforcement can be adapted to the existing conditions of the structure without extensive modifications.
Reduced Friction Losses: The unbonded system experiences lower friction losses compared to bonded systems. This efficiency means that more of the applied tension is effectively transferred to the concrete, enhancing the structural performance.
Increased Eccentricity: The ability to position tendons with greater eccentricity (distance from the neutral axis) allows for more effective counteraction of tensile stresses in the concrete, improving the overall strength and load-bearing capacity of the slab.
No Grouting Required: Unlike bonded systems, the unbonded tendon system does not require grouting. This simplifies the installation process and reduces the potential for errors or complications associated with grout application.
Active Anchors: The anchors in an unbonded system remain active throughout the life of the structure. This means they continue to hold the tension in the strands, providing ongoing support and stability.

Application in Repairs:

In the context of repairing existing structures, these features of the DSI unbonded single strand tendon system provide several distinct advantages:

Adaptability: The ability to deflect tendons and work around existing openings or irregular shapes makes it ideal for retrofitting and reinforcing older buildings where the original design may not be uniform or standard.
Efficiency: The quick installation process reduces downtime, which is crucial for buildings that need to remain operational during repairs.
Maintenance: With no need for grouting, maintenance requirements are lower, and the risk of complications during installation is reduced.
Longevity: The active anchors ensure that the system remains effective over the long term, providing continued structural support and minimizing the need for future interventions.

By employing the DSI unbonded single strand tendon system, Somers Engineering can efficiently and effectively reinforce and repair concrete slabs, enhancing their durability and performance while minimizing disruption and costs.

Somers Post-Tensioning in Civil Structures

Somers Engineering Limited’s post-tensioning systems play a crucial role in repairing various civil structures, including bridges, reservoirs, silos, nuclear facilities, LNG tanks, cryogenic systems, and oil platforms. These systems enhance the structural integrity and performance of these critical infrastructure elements, ensuring their safety and longevity.

Post-Tensioning in Bridge Repairs

In bridge repairs, Somers’ post-tensioning systems enable the creation of longer, more slender spans with fewer supports, allowing for more elegant and efficient designs. When existing bridges show signs of wear, cracking, or structural deficiencies, post-tensioning can be employed to reinforce and strengthen the structure. This process involves adding high-strength steel tendons that are tensioned after the concrete has cured, providing additional support and reducing the likelihood of further cracking. By minimizing cracking, post-tensioning enhances the durability and longevity of the bridge, ensuring it can safely carry traffic for many years.

Comprehensive Scope of Work in Civil Structure Repairs

Somers Engineering’s comprehensive scope of work in repairing civil structures includes:

Consulting: Offering expert advice on the best approaches for repairing and reinforcing existing structures. This includes assessing the current condition, identifying potential issues, and recommending appropriate post-tensioning solutions.
Design & Shop Drawing Engineering: Creating detailed designs and shop drawings for the repair and reinforcement of structures. This ensures that the post-tensioning systems are precisely tailored to the specific requirements of each project, taking into account the unique challenges and constraints of the structure.
Manufacturing and Supply: Producing high-quality post-tensioning components, such as steel tendons and anchorage systems, and supplying them to the repair site. This ensures that all materials meet the necessary standards and are ready for installation.
Site Supervision: Providing on-site supervision during the repair process to ensure that the post-tensioning systems are installed correctly and according to the design specifications. This oversight helps to prevent errors and ensures the effectiveness of the repair.
Inspection and Maintenance: Conducting thorough inspections to assess the condition of the post-tensioned structures and performing any necessary maintenance to keep them in optimal condition. Regular inspection and maintenance are crucial for detecting early signs of wear or damage and addressing them promptly to extend the life of the structure.

Specific Applications in Various Civil Structures

Reservoirs and Silos: Post-tensioning systems can reinforce the walls of reservoirs and silos, which are subject to significant internal pressures. By adding post-tensioned tendons, the walls can better withstand these forces, reducing the risk of cracking and leakage.
Nuclear Facilities and LNG Tanks: These structures require exceptionally high safety standards. Post-tensioning can enhance their resilience to seismic activity and other stresses, ensuring the containment of hazardous materials.
Cryogenic Systems and Oil Platforms: These structures operate under extreme conditions. Post-tensioning provides additional strength and stability, ensuring they remain safe and functional despite the harsh environments.

By leveraging post-tensioning systems in repairs, Somers Engineering enhances the structural performance and durability of critical civil structures, ensuring they can continue to serve their essential functions safely and efficiently.

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