Deformation Capacity Limits for Reinforced Concrete Walls

Abstract

The use of deformation capacity limits is becoming increasingly common in seismic design and assessment of reinforced concrete (RC) walls. Deformation capacity limits for RC walls in existing design and assessment documents are reviewed using a comprehensive database. It is found that the existing models are inconsistent and do not account for variation in deformation capacity with changes in the ratio of neutral axis depth to wall length ( c/ L w) and ratio of transverse reinforcement spacing to longitudinal bar diameter ( s/ d b) at the wall end region. A new mechanics-based model considering strain limits on the concrete and reinforcement is recommended. Concrete compressive strain limits for different levels of wall end region detailing are selected based on curvature ductilities for the walls in the database. Reinforcement tensile strain is limited based on a model for bar buckling. The proposed model, which accounts for c/ L w and s/ d b, is shown to have less dispersion and more accuracy than existing models when compared against experimental data and provides consistency between assessment and design provisions.

Research Programme on Seismic Performance of Reinforced Concrete Walls: Key Recommendations

“…A database of walls detailed to nominally/limited ductile wall provisions was assembled by Crowe [55] and Shegay et al [16]. As in Figure 14a for ductile walls, similar curvature ductility capacity trends are observed with respect to / for the nominally/limited ductile walls, as seen in Figure 14b.…”

“…Empirical study on the wall deformation capacity using a database of ductile walls previously tested in the literature. [12,16] Gain an in-depth understanding of the global out-of-plane instability/buckling mechanism, including the effect of governing parameters such as wall section thickness, length, axial load and longitudinal reinforcement ratio.…”

“…Recommended values to define deformation demand design limits for ductile and nominally/limited ductile walls are provided in Table 6. Full details of the derivation of Equation (2) are provided by Shegay et al [16]. The proposed design deformation demand limits for ductile walls and nominally/limited ductile walls are plotted with experimental data in Figure 8a and Figure 8b, respectively.…”

“…As in Figure 14a for ductile walls, similar curvature ductility capacity trends are observed with respect to / for the nominally/limited ductile walls, as seen in Figure 14b. Shegay et al [16] extended the model presented in Equation 2to apply for assessment of nominally/limited ductile walls, with recommended corresponding strain limits shown in Table 6. Figure 14b shows that the Shegay et al model can be further simplified by a linear function (Equation 5 Key recommendation: It is recommended that Equation (5) by Crowe [55] or Equation (2) by Shegay et al [16] (with reference to Table 6) are used for the assessment of probable curvature ductility capacity of nominally/limited ductile walls.…”

Experimental study on the effects of bi‐directional loading pattern on rectangular reinforced concrete walls

“…These cracks widened and extended during the last cycle of 2% drift (loading the left side) and 2.5% drift (loading the right side). Such in‐plane and out‐of‐plane diagonal cracks were not reported in previous studies on slender rectangular walls under unidirectional loading 1,12,29,31,50–53 . Based on the results of this experimental study, it can be concluded that asymmetric bi‐directional loading (eg, skewed loading) can trigger the development of diagonal cracks in the out‐of‐plane direction of RC slender walls.…”