The Research Of Reliability For The Strengthened Reinforced Concrete

With the useful life of building growing, more and more buildings are above or close to its design working life. Some degrees of certain security risks exist in these buildings, so it is needed to re-identify their security, applicability and durability. When the identification results of structures do not meet any regulatory requirements, it is needed for technical processing, one way to deal with is by the maintenance reinforcing methods to meet the ultimate limit state and serviceability limit state. For the ultimate limit state of structure member, the specific approach is to use the standard for appraiser of reliability of civil buildings to assess the safety. If the structure does not meet the safety, it is needed to use the technical specification for strengthening to reinforce the structures. However, the reliability specification level of identification and reinforcement of the existing structure is not clear. In this paper, the following aspects are analyzed:(1) In this paper, considering the reliability of existing structure and the proposed structure is different, a new calculation method of the reliability is proposed for existing concrete structures which having used for several years. The corrosion of steel-bar caused by carbonation, the decrease of concrete strength and the influence of subsequent years to the modification of live load are considered. The results indicate that the characteristics of existing structures should be considered on the analysis of the reliability index.(2) For the reinforced concrete columns with axial loads, the reliability index of the original part and new part is calculated respectively according to the design code for reinforcement of increasing cross-section method. The reliability index of the original part is calculated according to existing structures, while the new part is calculated according to the proposed structure. And the influential factors of the two parts to the reliability index are analyzed. The results indicate that the reliability index of the two parts of reinforced concrete can be coordinated by adjusting the proportion of unloading and the load that steel bears.(3) According to the design code for strengthening concrete structure and considering the initial load level and the lag of train of steel for RC beams glued with steel plate, the reliability index of RC beams glued with steel plate is calculated with First Order Second Moment.(4) As a matter of fact, which random input parameters have great influence on the output results is an important issue. The paper take the Finite Element Analysis software Ansys to build the model of the RC beams glued with steel plate and use the PDS module to analysis the sensitivity of the RC beams glued with steel plate. The results indicate that the concrete compressive strength and load contribute more to the deflection and stress of the RC beams glued with steel plate.