Research On The Flexural Behavior Of The Prestressed Hollow Slabs Reinforced By The Pc Steel Bars With Helical Flute

The PC steel bars (Abbreviation of the steel bars for prestressed concrete) is a new prestressed steel produced through the mechanical descaling, cold drawing molding processing, and then through the quenching and heat treatment processes. The production uses the low-alloy hot rolled steel wire rod as the raw material. According to the Chinese code Steel Bars for Prestressed Concrete GB/T 5223.3-2005, the PC bar has the advantages of high strength(1080 MPa～1570 MPa), good ductility(δ_at≥3.5%), well solderability, upsetting and reeling. The production processes of the PC bar use the mechanical bending derusting without pickling. So, promoting to use PC bar in a large scale as a substitute of high-strength steel wire, strand not only can make up the lack of mid-strength steel in our country, but also can reduce the contamination produced along with the washing by the acid in the producing process of the high strength steel wire, strand. This can acquire significant economic and environment benefits.In order to test the flexural behavior of the prestressed medium-span hollow slab reinforced by the PC bars, twelve hollow slabs reinforced by the PC bars are produced according to the Beijing stand atlas Prestressed Long-span Hollow Slab Jing 92G42 and The Design Code Of The Concrete Structure GB50010-2002. The monitoring and analysis of the production process indicates that this batch of the PC bar is brittle, bad behavior of upsetting and steam curing. So, the PC bar's ductility and quality stability still need to be improved.After the curing is done, the load tests are done according to the Beijing standard atlas Prestressed Longspun Hollow Slab Jing 92G42 and monitored the development of the deflection, the crack width and the number of the crack along with the load increasing. Also the structural performance tests are done according to The Acceptance Code of Construction Quality GB50024-2002. Form the test results, we can get the conclusion that the slabs have a good flexural behavior, a good recovery performance and a well crack distribution after the failure of the slab when the adequate prestress is established. The slabs have a good crack resistance and overloading performance. Also it can be made full use of the PC bar's strength.But in this tests, the hollow slab's crack width reinforced by theφ9.0 PC bars is small, and this slabs have the risk of brittle fracture, indicating that the ductility and quality stability of the PC bar continue needs to be improved. After referring to the relevant documents, the irregular cross-section of the hollow slab is equivalent simplified as the工-shaped cross-section for analysis. After the equivalent simplifying, the prestress loss, reverse-arch, crack load, deflection under the serviceability limit state and the ultimate load are calculated according to The Design Code Of The Concrete Structure GB50010-2002. Through the comparing with the test results, the practicable advices are suggested in order to use the PC bar in the engineering.At last, this text analyzes the main reinforcements used in the prestressed hollow slab, and selects four hollow slabs reinforcedby the cold-rolled ribbed steel, high-strength steel wire,strand and PC bar, making a comparative analysis on the flexural behavior of these slabs.