Post-Tensioned Silos
ESPT specializes in the design and construction of post-tensioned concrete silos, offering enhanced structural integrity and durability for storing materials like grains, cement, and other bulk goods.
Prestressed Silos
Prestressed silos are specialized storage structures designed to handle materials like grains, cement, or other bulk goods. They use prestressed concrete, which involves applying tension to steel tendons within the concrete to counteract stresses from external loads. This technique enhances durability, reduces cracking, and allows the silo to withstand high pressures and environmental conditions.
Prestressed silos are commonly used in industries like agriculture, construction, and manufacturing. They are particularly effective for storing materials that exert significant pressure on the walls, such as liquids or fine powders.
Post-Tension Silos
Post-tension silos are a type of reinforced concrete silo that uses post-tensioning techniques to enhance structural integrity and durability. Post-tensioning involves placing steel tendons within the concrete and applying tension after the concrete has set. This method helps counteract the stresses caused by the stored material's weight and lateral pressure.
The use of post-tensioning allows for thinner silo walls, reducing the amount of concrete required and making the construction more economical.
Construction Process
- •Design Phase: Engineers calculate the lateral pressures exerted by the stored materials and design the silo accordingly. This includes considering dynamic pressures caused by seismic activity or uneven loading/unloading.
- •Installation of Tendons: Steel tendons are placed within the concrete structure during construction. These tendons are housed in ducts to allow for tensioning after the concrete has set.
- •Post-Tensioning: Once the concrete has cured, tension is applied to the steel tendons. This process compresses the concrete, counteracting tensile stresses and preventing cracks.
- •Final Adjustments: Engineers perform static evaluations to ensure stability, strength, and crack prevention. This step is crucial for long-term durability.
Advantages
- •Crack Prevention: Post-tensioning minimizes cracking, ensuring impermeability and protecting stored materials from moisture.
- •Cost Efficiency: Thinner walls reduce material usage, making the construction more economical.
- •Durability: The structure can withstand dynamic pressures and seismic activity, extending its lifespan.
Multi-strand Post-Tension Anchorages
- •Design: Multi-strand systems consist of a bundle of steel strands, typically with diameters of 0.5" (12.7 mm) or 0.6" (15.2 mm). These strands are housed in a corrugated galvanized metal duct, which provides protection and allows for tensioning.
- •Anchor Head Unit: The strands are individually gripped in an anchor head unit, which transmits the prestressing force to the concrete. The anchor head is paired with a casting unit and spiral reinforcement to handle the stresses at the anchorage zone.
- •Tensioning Process: The strands are stressed simultaneously using a multi-strand stressing jack, which applies the required force uniformly. After tensioning, the strands are locked in place using wedges in the anchor head.
- •Applications in Silos: Multi-strand anchorages are used in silos to counteract the lateral pressures exerted by stored materials like cement, grains, or coal. They enhance the silo's ability to withstand dynamic loads, seismic activity, and environmental stresses.
Anchorages Testing Methods
- •Load Testing: Anchorages are subjected to controlled loads to verify their ability to handle the forces they were designed for. This includes testing the anchor head, wedges, and bearing plates under simulated conditions.
- •Grouting Tests: Grouting is tested to ensure proper filling of ducts and adequate bonding between tendons and concrete. Pressure tests are conducted to check for leaks or voids in the grout.
- •Component Assembly Tests: Individual components like ducts, grout caps, and couplers are tested for durability and compatibility. These tests ensure that the assembly can withstand environmental stresses and dynamic loads.
- •Corrosion Resistance: Anchorages are tested for their ability to resist corrosion, especially in silos storing materials that may create a humid or chemically aggressive environment.
- •Static and Dynamic Evaluations: Static tests assess the anchorages' performance under constant loads, while dynamic tests simulate fluctuating pressures caused by loading and unloading of materials.