Probabilistic modeling of structural deterioration of reinforced and concrete beams under saline environment corrosion

For existing reinforced concrete structures exposed to saline or marine conditions, there is an increasing engineering interest in their remaining safety and serviceability. A significant factor is the corrosion of steel reinforcement. At present there is little field experience and other data available. This limits the possibility for developing purely empirical models for strength and performance deterioration for use in structural safety and serviceability assessment

Modelling deterioration of structural behaviour of reinforced concrete beams under saline environment corrosion

In the assessment of existing structures the likely future deterioration of strength and stiffness is of interest. For reinforced concrete beams one of the most important influencing factors is the loss of reinforcement cross-sectional area at critical locations. Because corrosion is a long-term process for well-designed structures, there is only limited field experience available on which to draw and with which to make empirical rules

Vulnerability assessment of corrosion affected concrete structures

Reinforcement corrosion in concrete is the predominant causal factor for the premature deterioration of reinforced concrete structures, causing various degrees of damage to the structure and leading to final structural collapse. The existence of reinforcement corrosion in concrete structures makes them increasingly vulnerable over time. This ultimately poses a potential risk to the public

New Gain Controllable Resistor-less Current-mode First Order Allpass Filter and its Application

New first order allpass filter (APF) in current mode, constructed from 2 CCCCTAs and grounded capacitor, is presented. The current gain and phase shift can be electronically /orthogonally controlled. Low input and high output impedances are achieved which make the circuit to be easily cascaded to the current-mode circuit without additional current buffers. The operation of the proposed filter has been verified through simulation results which confirm the theoretical analysis. The application example as current-mode quadrature oscillator with non-interactive current control for both of oscillation condition and oscillation frequency is included to show the usability of the proposed filter

Probabilistic modeling of structural deterioration of reinforced concrete beams under saline environment corrosion

For existing reinforced concrete structures exposed to saline or marine conditions, there is an increasing engineering interest in their remaining safety and serviceability. A significant factor is the corrosion of steel reinforcement. At present there is little field experience and other data available. This limits the possibility for developing purely empirical models for strength and performance deterioration for use in structural safety and serviceability assessment. An alternative approach using theoretical concepts and probabilistic modeling is proposed herein. It is based on the evidence that the rate of diffusion of chlorides is influenced by internal damage to the concrete surrounding the reinforcement. This may be due to localized stresses resulting from external loading or through concrete shrinkage. Usually, the net effect is that the time to initiation of active corrosion is shortened, leading to greater localized corrosion and earlier reduction of ultimate capacity and structural stiffness. The proposed procedure is applied to an example beam and compared to experimental observations,including estimates of uncertainty in the remaining ultimate moment capacity and beam stiffness. Reasonably good agreement between the results of the proposed procedure and the experiment was foun

A risk-cost optimized maintenance strategy for corrosion-affected concrete structures

Corrosion of reinforcing steel in concrete is the dominant cause for premature failures of reinforced concrete structures located in chloride-laden environments. It is also observed that some severely deteriorated concrete structures survive for many years without maintenance.This raises the question of why and how to maintain corrosion-affected concrete structures, in particular in the climate of an increasing scarcity of resources. The present article attempts to formulate a maintenance strategy based on risk-cost optimization of a structure during its whole service life. A time-dependent reliability method is employed to determine the probability of exceeding a limit state at each phase of the service life. To facilitate practical application of the formulated maintenance strategy,an algorithm is developed and programmed in a userfriendly manner with a worked example. A merit of the proposed maintenance strategy is that models used in risk assessment for corrosion-affected concrete structures are related to some of the design criteria used by practitioners. It is found in the article that there exists an optimal number of maintenances for cracking and delamination that returns the minimum total cost for the structure in its whole life. The maintenance strategy presented in the article can help structural engineers, operators, and asset managers develop a cost-effective management scheme for corrosion-affected concrete structure

Concrete delamination caused by steel reinforcement corrosion

Practical experience and laboratory observations indicate that corrosion affected reinforced concrete structures are prone more to cracking and delamination of the concrete than to the loss of structural strength. A review of research literature suggests that insufficient theoretical work on corrosion induced concrete delamination has been undertaken. This paper proposes a theoretical method to predict the time to concrete delamination caused by steel reinforcement corrosion. The method is based on fracture mechanics and uses crack opening in concrete as the criterion for its delamination. An analytical model is derived to determine the crack width in concrete. A numerical example is given to illustrate the proposed method and a comparison with both test results and an empirical model indicates a good agreement. It is found in the paper that the corrosion rate is the most significant single factor that affects the time to concrete delamination. The proposed method can be used for the prediction of time to concrete delamination for reinforced concrete structures located in chloride-laden environments. In principle, this provides a means for judging timely intervention and as such has the potential to prolong the service life of corrosion affected concrete structure