Remaining service life assessment of river bridges with cracked members

Bridges on rivers can have major maintenance problems over the years. The piers of the river bridges can crack due to adverse external effects such as floods, earthquake or chemical spills to river bed. The remaining service life assessment of the cracked bridge piers becomes very important on scheduling an immediate rehabilitation or maintenance program. The focus of the paper is given to develop a computational guideline to be used in remaining service life assessment of river bridge piers. While estimating the service life, rate of corrosion of reinforcing steel is considered as the main reason. The corrosion rate is dependent on actual crack width measured on piers and aggressiveness of environmental conditions surrounding the pier. In this scope, a computational guideline is developed considering crack width, cement type, aggressiveness of environment and concrete cover to assess the corrosion levels.

Relationship between aggressiveness and chloride content on the surface of considered member, and reference diffusion value at accepted reference time are the basic parameters needed to be identified in the analysis. Unless a valid experimental data is provided, for mild, moderate and high aggressiveness surface chloride content can be taken as 2, 4.5 and 12 kg/m³ respectively. Reference diffusion is another complex parameter depending on the aggressiveness and cement type. For instance, reference values for PCC1 type of cement can be taken as 30 mm²/year (mild aggressiveness), 80 mm²/year (moderate aggressiveness) and 600 mm²/year (high aggressiveness) unless a valid data is available.

The results of the method have been checked against the requirements of Turkish Reinforced Concrete Design Code and AASHTO LRFD (2012) to verify the critical crack width limit allowances for structures at different environmental conditions. For instance, at moderate aggressiveness, if the crack width exceeds 0.2 mm, the structures have been determined to have less service life compared to normally deteriorated structures as shown in Figure 1. Figure 1 Expected service life versus crack width at moderate aggressiveness and for PCC1. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig211_1.tif"/>