Title:
One-Way Shear Strength of Large Beams and Foundation Elements Containing High-Strength Longitudinal Reinforcement
Author(s):
Jerry Y. Zhai and Jack. P. Moehle
Publication:
CRC
Volume:
Issue:
Appears on pages(s):
285
Keywords:
DOI:
Date:
5/1/2025
Abstract:
A set of physical one-way shear tests were modeled in the nonlinear finite element software ATENA. The FE model was calibrated using data from Phase 1, Phase 3, and Phase 4. General observations and ATENA-specific observations from the calibration process are summarized below: 1. Mechanisms relating to the mechanics along the failure crack (crack stiffness, crack opening parameters) were most influential in fine tuning FE model’s failure mode. In ATENA, these are the shear factors, fracture energy, and unloading factors. They may go by different names in other FE software depending on the implemented constitutive models. 2. FE models with the best failure load simulations also tended to produce an accurate crack pattern when compared with the experimental results. 3. There is some inherent variability in the FE modeling process. A sensitivity analysis is recommended when resources permit to observe the scatter in FE load-displacement response. Using the calibrated FE models, the one-way shear strength of mat foundations subject to various loading effects and boundary conditions was investigated. The results of these parametric studies are summarized below: 1. FE models showed that the shear strength of a soil-supported foundation is equal to or greater than the shear strength of the same member loaded as a beam in 3-point bending. The differences are attributed to the presence of vertical clamping stresses in foundations. Other variables, such as member depth and longitudinal reinforcement ratio, are likely to affect the effectiveness of clamping stresses on shear strength but require additional study. 2. When subject to axial loads generated by earth pressure or horizontal friction, shear strength can increase by modest amounts. However, quantifying soil friction or lateral earth pressures in a foundation mat can be difficult and highly variable. It is not recommended to consider axial compression in mat foundations due to the relatively small benefit and large uncertainty in determining axial compression. 3. The axial compression term in the ACI 318-19 shear equations appears to reasonably estimate the increase in shear strength. 4. One-way shear strength is reduced when a mat foundation is subject to significant overturning moment due to increased effective shear spans (M/Vd) and reduced clamping action near the critical section. Designing a mat foundation using procedures for a beam (i.e., considering the size effect) provides a lower bound on design shear strength and is recommended until further studies are able to more fully quantify these effects.