S. Ramanujam

Models for Corrosion-Induced Bond Strength Degradation in Reinforced Concrete

The assessment of progressive degradation of bond between concrete and reinforcing steel is of great importance in evaluating the residual strength of the reinforced concrete (RC) structural members with corroded reinforcements. Simple empirical and analytical models are proposed to demonstrate the effect of reinforcement corrosion on the reduction of bond strength. The empirical models are proposed by considering a wide range of published experimental investigations related to the bond strength degradation as a result of reinforcement corrosion. An analytical model for bond strength of corroded reinforcement has been adopted in which the estimation of various bond strength parameters is proposed by the authors. These parameters include corrosion pressure due to expansive action of corrosion products, modeling of tensile behavior of cracked concrete, and adhesion and friction coefficient between the corroded bar and cracked concrete. The performance of the proposed empirical and analytical bond strength models is then investigated through their ability to reproduce the available experimental trends. It has been found that the proposed models are capable of providing the estimates of predicted bond strength of corroded reinforcement that are in reasonably good agreement with the experimentally observed values and are also in agreement with those of the other reported published data on analytical and empirical predictions.

Evaluation of Seismic Fragility of Structures - A Case Study

The present paper attempts to evaluate the seismic fragility for a typical elevated water-retaining structure. The structure is analysed for two cases: (i) empty tank; and (ii) tank filled with water. The various parameters that could affect the seismic structural response include material strength of concrete and reinforcing steel, effective prestress available in the tank, ductility ratio and structural damping available within the structure, normalised ground motion response spectral shape, foundation and surrounding soil parameters and the total height of water available in the tank. Based on this case study, the seismic fragility of the structure is developed. The results are presented as families of conditional probability curves plotted against peak ground acceleration (PGA) at two critical locations. The procedure adopted, incorporates the various randomness and uncertainty associated with the parameters under consideration.

Seismic Requalification of an Underground RCC Duct

The present paper deals with the reevaluation of design stresses and assessment of safety margins available for an underground reinforced cement concrete (RCC) duct. For stress analysis, a hvo-dimensional mathematical model has been adopted to appropriately represent the structure. The structure has been analyzed for both static and seismic loads. The seismic analysis has been carried out for site-specific response spectra. The design checks have been performed using available international standards and, accordingly, the safety margins have been evaluated. The structure has been found to possess sufficient safety margins under all the postulated design loadings. The seismic reassessment methodoloffv conforms to the available international standards.

Seismic Fragility Analysis of a Water Storage Structure

The present paper is concerned with the seismic response and fragility evaluation of a water storage structure. Seismic analysis has been carried out considering the hydrodynamic effects of the contained water. The various parameters that could affect the seismic structural response include material strength of concrete, structural damping available within the structure and the normalized ground motion response spectral shape. Based on this limited case study; the seismic fragility of the structure is developed as families of conditional probability curves plotted against peak ground acceleration (PGA) at the location of interest. The procedure adopted incorporates the various randomness and uncertainty associated with the parameters under consideration.Copyright

Seismic Re-Qualification of an Underground RCC Duct

The present paper deals with the re-evaluation of design stresses and assessment of safety margins available for an underground RCC duct. For stress analysis, a 2-D mathematical model has been adopted to represent the structure appropriately. The structure has been analyzed for both static and seismic loads. The seismic analysis has been carried out for site-specific response spectra. The design checks have been performed using available international standards and accordingly the safety margins have been evaluated. The structure has been found to possess sufficient safety margin under all the postulated design loadings. The seismic reassessment methodology conforms to the available international standards.Copyright