The Deformation Capacity of Lap Splices in RC Walls: From Experimental Testing to Numerical Modelling

Field observations as well as experimental tests have shown that both the strength and displacement capacity of reinforced concrete (RC) members might be significantly reduced by the presence of lap splices. This degradation applies in particular if the longitudinal reinforcement is spliced in regions where inelastic deformations concentrate, which is frequently the case for RC building walls or bridge piers. In fact, these members often feature lap splices above the foundation level, where seismic demands are largest and damage is likely to occur. In performance-based earthquake engineering (PBEE), which now sets the standards for seismic assessment, deformation rather than force capacities are compared to the demand; however, past experimental studies on spliced members have focused on the characterization of the strength rather than the deformation capacity of lap splices. Further-more, these tests were primarily performed on spliced RC beam and column specimens, typically subjected to mono-tonic loading. Experimental investigations on the deformation capacity of members with lap splices under cyclic loading are underrepresented. This applies in particular to walls, despite the fact that splicing of longitudinal reinforcement in their plastic hinge regions is common construction practice. In line with the available experimental work, most of the developed empirical and analytical expressions aim solely at quantifying the force capacity of lap splices. The preceding observations have motivated the following objectives of the present work: (i) investigate the displacement capacity of spliced RC walls through experimental tests; (ii) propose expressions characterizing the deformation capacity of lap splices subjected to monotonic and cyclic loading; and (iii) develop numerical and mechanical models suitable for practicing engineers to simulate the behaviour of RC members with lap splices. Existing experimental programmes on spliced RC walls, including the cyclic test of two units recently carried out at the structural laboratory of EPFL, are first reviewed and collected in a database. The review of the experimental data shows that the failure of the outermost lap splices, located in the boundary element, typically triggers the failure of the RC wall. Moreover, the main parameters influencing the deformation capacity of lap splices are identified. Building on these findings, an experimental programme on spliced RC wall boundary elements is designed using lapsplice length, confining reinforcement, and loading history as variable parameters. From the obtained results, an empirical expression for the lap-splice strain capacity is derived. A 2D shell element model is first developed to simulate the global force-displacement response of the walls in the aforementioned database. The lap splice response is considered through a new equivalent uniaxial steel stress-strain law. Secondly, an axially equilibrated displacement-based beam element model is proposed in which the lap splice response can be included by using the derived strain limit expression. Finally, a novel mechanical model describing the behaviour of spliced RC wall boundary elements is presented. It extends the tension chord model by accounting for anchorage slip and the presence of lap splices.