Abstract
Importance of consideration of chloride induced corrosion in service life design of reinforced concrete (RC) structures situated in marine environment is well known. This paper attempts to provide, within the framework of Monte Carlo Simulation, methodologies for durability based service life design of RC members. A methodology using fragility curves is proposed to assist in the service life design of freely degrading RC flexural beams. For maintained RC beams, a methodology is developed, that incorporates the concepts of virtual aging, failure rate approach and time-variant reliability analysis. By addressing maintenance at the design stage itself, the methodology developed would help in sustainability based service life design. The use of both the methodologies is demonstrated by considering an example of T-beam. From the results of the example problem considered, it has been found that corrosion initiation time would govern the service life. 30% replacement of cement with pulverized fuel ash is considered as a sustainable alternative for construction of durable structures satisfying the service life performance targets with lesser number of repairs.
Highlights
Engineering structures experience degradation of strength with time due to environmental effects, in addition to long term effects during their service life
Mean initiation time of corrosion for ordinary Portland cement (OPC) concrete beam is 6.69 years, whereas, for 30% pulverized fuel ash (PFA) concrete beam having the same cover, the mean initiation time of corrosion is around 40 years
The increase in Ti of 30% PFA concrete can be attributed, amongst others, to the experimental findings of Dhir & Byars[37], that, 30% PFA concrete has a reduced permeability compared to the OPC concrete, both having been designed for the same compressive strength
Summary
Engineering structures experience degradation of strength with time due to environmental effects, in addition to long term effects during their service life. A time dependent stochastic analysis is required to formulate a framework for the reliability based service life design of RC structures (in this paper an RC beam is considered). A novel methodology based on virtual aging concept (Brown & Proschan[16], Kijima[17], Balaji Rao et al.18) is proposed for reliability analysis of maintained flexural members, which can be used to analyse expected times of inspection and repair, against specified durability limit states in RC structures. The methodology identifies that the corrosion initiation time is a random variable This methodology can assist in durability-based design decision making, giving an opportunity to compare various options, in selection of type of concrete and cover thickness, and their respective future repair requirements and making the design consider the sustainability issues . An example problem of an RC T-beam is presented, to illustrate the proposed methodology
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