Assessment and Design Tools

The objective of this task is the validation and enhancement of flexural analysis assessment models to evaluate the force-displacement behavior of the test units presented in Tasks 1 through 3. The objective of these models is to employ them as the basis for rational and simple design methods of structural walls and wall assemblies and as global predictive and assessment tools in the experimental investigation. These moment-curvature-based assessment models bridge the gap between over-simplified approaches to design and over-complicated non-linear finite element models.

A monotonic flexural model for structural walls with confined-corner elements has been previously developed by the co-PI. The non-linearity that results from shear behavior is determined through assumptions about the spread of plasticity and pure shear deformations. This is accomplished by including a tension shift component in the plastic hinge length and assuming that shear displacements are linearly dependent on flexural displacements. Comparison of the model with experimental data from structural walls with different aspect ratios showed that provided that strain limits, the plastic hinge length, and shear displacements are correctly assumed, relatively simple moment-curvature analyses can form the basis for a practical force-displacement characterization of a reinforced concrete member.

While this model has been shown to model tests on structural walls well enough, several details need refinement for use within the current research project and their wide implementation to thin-webbed members. Strain limits that account for the phenomenon of bar buckling will be investigated by carefully monitoring real strain demands on the confining steel up to yield and considering an energy balance approach and a strain compatibility approach. The correlation between the actual spread of plasticity and the plastic hinge length will be established for high-strength-concrete walls. Finally, fully cyclic models for both steel and concrete, which are already well developed, will be incorporated and the effects of cyclic versus monotonic loading will be established.

The modified section analysis model will be calibrated with respect to the experimental results from the proposed research program. Moreover, the results from the finite element analyses from Task 3 will provide additional insight for calibrating the shear behavior of the HSC structural walls.