The ERIES-ALL4wALL project involves shake-table testing of two slender U-shaped walls, designated as UWS1 and UWS2. These walls are subjected to increasing-intensity input motions that induce, in an alternating manner, unidirectional flexure without torsion along the wall weak axis, and bidirectional flexure with torsion. The tests herein described are the first to assess the torsional nonlinear dynamic response of U-shaped walls. The project concurrently focuses on determining (UWS1) and minimizing (UWS2) residual displacements.

In addition to studying the interaction of torsion and bi-directional flexure in the dynamic response of RC U-shaped core walls, and to investigate, under realistic excitation conditions, a new technology that has the potential to minimize post-earthquake residual displacements, the ERIES-ALL4wALL project had the two following objectives: (i) develop and calibrate numerical models for the walls’ response, which was also needed to estimate the behavior of the units prior to the tests; (ii) apply innovative instrumentation techniques, including distributed fiber optic sensing (DFOS), camera-based vibration measurements, and a motion capture system.

The two half-scale U-shaped wall units, denoted UWS1 and UWS2, are identical in geometry. The walls have a thickness (tw) of 100 mm, with web and flange lengths (Lw and Lf) of 1300 mm and 1050 mm, respectively. These wall units share the same cross-sectional dimensions as previously tested quasi-static wall units but vary with respect to their reinforcement detailing. Differing from previous quasi-static units, these units for dynamic tests have two 100 mm thick intermediate slabs spaced 1.5 m apart. They intend to partially represent the effect of story slabs in the wall response, namely regarding warping and distortion. Each slab measures 1900 mm x 1620 mm and is hollow inside the core wall. The slabs were reinforced with two layers of mesh of 6 mm diameter, with a square spacing of 100 mm. The foundation block, measuring 2.1 m x 2.1 m, was fastened to the shake table floor using sixteen M30 threaded bars evenly spaced at 500 mm orthogonal intervals. A top collar (obtained by considerably increasing the wall thickness at the head) was employed to support the top masses, which is expected to only partially restrain warping. The dimensions of the top collar include a depth of 500 mm. The wall height, measured from the foundation top to the wall collar and approximately the center of the imposed mass blocks, is 4.54 m and 5.1 m.

The design of the test units followed a similar approach to others. Rather than strictly adhering to a specific code, the design prioritized high ductility using capacity design principles deemed reasonable. However, certain aspects, such as longitudinal reinforcement placement, aligned with international building standards for high ductility—e.g., Ductility Class Medium (DCM) or High (DCH) according to Eurocodes 2 and 8. The wall units were designed with boundary elements containing a higher concentration of longitudinal and transverse reinforcement to ensure the development of high compressive strains in these regions, necessary for a ductile wall response.

The two test units differed in the material used to vertically reinforce these boundary elements: UWS1 was reinforced with 12 mm (Φ12) conventional steel according to Eurocode 8.