Multi strands hydraulic jack and pump for post tensioning of bridge girder

Post-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons.
Post-tensioning applications include office and apartment buildings, parking structures,slabs- on-ground, bridges, sports stadiums, rock and soil anchors,and water-tanks. In many cases, post-tensioning allows construction that would otherwise be impossible due to either site constraints or architectural requirements. Although post-tensioning systems require specialized knowledge and expertise to fabricate, assemble and install,the concept is easy to explain.

BENEFITS :
To fully appreciate the benefits of
post-tensioning, it is
helpful to know a little bit about concrete. Concrete is
very strong in compression but weak in tension, i.e. it will
crack when forces act to pull it apart. In conventional
concrete construction, if a load such as the cars in a
parking garage is applied to a slab or beam, the beam will
tend to deflect or sag. This deflection will cause the
bottom of the beam to elongate slightly. Even a slight
elongation is usually enough to cause cracking. Steel
reinforcing bars (“rebar”) are typically embedded in the
concrete as tensile reinforcement to limit the crack widths.
Rebar is what is called “passive” reinforcement however;
it does not carry any force until the concrete has already
deflected enough to crack. Post-tensioning tendons, on the
other hand, are considered “active reinforcing. Because it is
prestressed, the steel is effective as reinforcement even
though the concrete may not be cracked. Post-tensioned
structures can be designed to have minimal deflection and
cracking, even under full load.