Seismic strengthening of reinforced concrete walls in existing buildings with fibre-reinforced polymer materials
Principal investigator: Dr Enrique del Rey Castillo, Senior Lecturer at the University of Auckland.
Other team members: Zhibin Li (PhD candidate), Dr Rick Henry (Associate Professor at the University of Auckland), and Andrew Thompson (Structural Engineer at Holmes Consulting)
Project number: 1980
Abstract
Reinforced concrete (RC) buildings constructed prior to the introduction of ductile design requirements may exhibit undesirable seismic behaviour. For RC walls, one such vulnerability is the lack of confinement to end regions that may lead to non-ductile compression failures. To overcome this vulnerability, strengthening of non-ductile RC walls is often required and the addition of confinement to end region concrete can be implemented using carbon fibre reinforced polymer (FRP) laminate and spike anchors. The main issue encountered when applying this strengthening method is the lack of existing design guidance on this confinement method, due to a lack experimental data to validate the approach. The objectives of this study were to:
1. provide the necessary experimental data to quantify the behaviour of concrete confined with FRP laminate and spike anchors,
2. develop a design method to calculate the behaviour of the confined concrete, and
3. verify that this method is applicable to wall boundary region confinement.
Static monotonic axial compression tests were conducted on 75 concrete prisms confined with FRP laminate and spike anchors using various FRP configurations. The most important parameter for both peak strength and deformation capacity is anchor spacing. A simple, analytical method has been developed that appropriately predicts the experimental results. This model was then applied in the design of the FRP strengthening of four concrete walls, and the various FRP configurations were investigated and compared with the behaviour of the un-strengthened wall. The deformation capacity significantly improved, with the failure of the wall being delayed from about 1% lateral drift to over 2.5%.