RC walls with structural deficiencies

Many buildings and bridges in countries like Switzerland, where the seismicity is moderate, were built before modern seismic design codes were introduced at times when there were hardly any provisions for seismic detailing at all. As a result, reinforced concrete (RC) walls and piers feature unfavorable characteristics such as low transverse reinforcement ratios, a lack of confining reinforcement and lap splices in the plastic zone. During an earthquake, structures constructed in this way are prone to brittle failures. In modern design, these types of detailing are hence avoided to ensure ductile behaviour and thereby provide sufficient displacement capacity.

When assessing the seismic performance of existing buildings and bridges, reliable estimates of the elements’ displacement capacity are needed. The objective of several EESD research projects is to contribute to better predictions of the displacement capacity of RC walls and piers taking into account their detailing characteristics. The focus of the projects is on (i) the development of mechanical models describing the force-displacement behaviour taking into account the given detailing characteristics and (ii) the evaluation and development of numerical tools that yield predictions of local engineering demand parameters such as strains, curvatures and crack widths. Our work aims at modifying existing beam element models to account for shear deformations and to improve the prediction of the strain distribution for walls.

To validate our models, we have conducted a large-scale test series on five RC walls was conducted to investigate (i) the stability of thin walls when subjected to uni-directional or bi-directional loading and (ii) the effect of lap splices at the wall base on the deformation capacity.

Simulation of walls with lap splices in the plastic zone.