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Types of prestressed steel strand application instructions
Prestressed concrete is a new technique developed in recent decades, it is in front of the component under external load, in the tension zone of the component in advance exerted pressure on concrete, the pressure is often referred to as prestressed concrete.And artifacts in the use of phase of the external loads tensile stress, the first thing to offset the preloading stress, it is delayed by the cracking of concrete, at the same time also limits the development of the cracks, so as to improve the crack resistance and stiffness of the components.Exerted pressure on the tension zone of the concrete member stress method, is in the tension zone of the tensioned prestressed reinforcement, by prestressed bond between steel and concrete, or anchorage of prestressed elastic contraction force transmitted to the concrete members, and generate the preloading stress.This paper mainly introduces the kinds and application of prestressed reinforcement.www.ytyuyingli.com prestressed anchorage
1. The cold drawing mild steel wire
Cold drawing mild steel wire is made of the disk HPB235 grade steel at room temperature by cold drawn wire drawing die, and the commonly used wire diameter is 3 mm, 4 mm and 5 mm. Cold drawn steel wire strength than raw material yield strength significantly increased, but the plastic is reduced, applicable to small component of prestressed tendon.
2. Cold drawn steel bar
Cold drawn steel bar is HRB335, HRB400, RRB400 grade hot-rolled steel at room temperature through tensioning beyond the yield point of a stress, make its produce certain plastic deformation after unloading, then through aging treatment.Cold drawn steel plastic and elastic modulus decreases while the yield strength and hardness is improved, can be directly used for prestressed reinforcement.
3. High strength steel wire
High strength steel wire is made from high quality carbon steel hot rolled wire rod by cold drawn, then the available machinery way to form processing indentation indentation steel wire, steel wire low temperature (typically below 500 ℃) was carried out on the wire straightening becomes straightening tempering steel after tempering treatment.Commonly used two kinds of high strength steel wire is divided into cold drawing and straightening tempering, according to the shape is divided into smooth, indentation, and three kinds of spiral rib.Prestressed steel wire after straightening tempering, can eliminate residual stress produced in the process of cold drawn steel wire, the steel wire is usually referred to as to eliminate stress.Eliminate the stress relaxation of steel wire loss is lower than prior to eliminate stress, but there are still high, after the stabilization treatment, relaxation values of steel wire is only ordinary wire 0.25 ~ 0.33, the steel wire is called low relaxation wire, has been widely used at home and abroad.The commonly used high strength steel wire is 4 mm in diameter, 5 mm, 6 mm, 7 mm, 8 mm and 9 mm to wait for a few kinds.
4. The steel strand
Steel strand is general by a few root carbon steel wire around a center twisted into a spiral steel wire in the hinge unit, then through the low temperature tempering.The diameter of the steel strand is bigger, generally for 9 ~ 15 mm, very soft, construction is convenient, but the price is more expensive.The strength of the steel strand is higher.Stranded wire specifications there were 2, 3, 7 and 19 shares, etc.7 strands of steel strand because area is larger, soft, construction location is convenient, is suitable for a first method and the method of post-tensioned prestressed structure and component, is one of the most widely used at home and abroad of the prestressed steel.
5. Heat treatment of steel
Heat treatment of steel by ordinary hot rolled carbon steel after quenching and tempering tempering heat treatment, which has the advantages of high strength, high toughness and high adhesive power, 6 ~ 10 mm diameter.Products of reinforced elastic volume of 2 m diameter, length of each coil is 100 ~ 120 m.Heat treatment of steel bar thread shape with longitudinal ribs and longitudinal ribs.
In recent years, China's high strength and high performance prestressed rebar (steel wire, steel strand) have sufficient supply, therefore, advocates the use of high strength prestressed steel strand, steel wire as the main structure of prestressed concrete pipe pile reinforcement in our country.
