5. Seismic retrofitting method for reinforced concrete piers with termination of longitudinal bars

During major earthquakes such as the 2011 off the Pacific coast of Tohoku Earthquake, a lot of sections containing termination of longitudinal bars of reinforced concrete (RC) piers suffered damage (Fig.1). Given that damage to sections containing termination of longitudinal bars in RC piers is not taken into account in the design stage, measures need to be taken to improve their seismic performance and prevent their failure. Consequently, a simple retrofitting method was developed to compress band-shaped steel plates to the sections containing termination of longitudinal bars of RC piers using prestressing bars (Fig.2). Compared with the ordinary retrofitting method using RC, the proposed method adds less weight to the RC pier, reducing the load on the foundations. This method offers other advantages, such as the cross section of the RC pier remains almost the same, therefore the width of RC piers in relation to the river width (impediment ratio of river flow) stays practically unchanged even after seismic retrofitting.

It was confirmed that the construction was easy ,and the capacities and deformation performance were increased by Loading tests using large scale specimens (Fig.3). Furthermore, this method was also able to apply damaged sections containing termination of longitudinal bars of RC piers.

Though seismic retrofitting has been carried out for columns of RC viaducts, seismic retrofitting for RC piers will be require in the future. This method realizes effective and economical seismic retrofitting of RC piers.