Destructive test study of the flexural load capacity of a full-scale reinforced concrete T-girder strengthened by externally prestressed CFRP plates

Abstract

With the upgrade of the transportation capacity of some existing freight tracks to heavy-haul railways in China, there is increased use of heavy-haul trains with larger axle loads and traction masses than in the past. The existing railway bridges not only bear the increased loads of heavy-haul trains but also experience much more loading times. This situation greatly affects the normal use and even the bearing capacity of reinforced concrete bridges and leads to concrete cracks and decreased flexural rigidity of the girders. As a result, the ultimate bearing capacity and operational safety of girders must be reasonably strengthened. Two reinforced concrete T-girders with a span of 12 m were demolished after 20 years of service. One of the T-girders, without any treatment, was selected for the destructive bending test, and the failure process and actual ultimate bearing capacity were obtained. The other girder was strengthened by the tensioning of prestressed carbon fiber reinforced plastic (CFRP) plates which showed the advantages of high tensile stress more than 2600 MPa, light mass, anti-corrosion and good resistance to durability. Then a destructive comparative bending test was performed to verify the strengthening effect. The research results showed that the actual ultimate flexural load capacity of the unstrengthened T-girder was 1.58 times the original design load capacity. After the T-girder was strengthened by prestressed CFRP plates, the cracking moment and actual ultimate flexural load capacity were 30.5% and 16.4% higher, respectively, which could decrease the cracking degree and deflection-span ratio of the T-girder under the operating conditions of heavy-haul trains. The strengthened T-girder showed a desirable serviceable limit state and ultimate flexural bearing capacity for KM98 trains with 300 kN axles.