Title: Behavior of Large Pile Caps Subjected to Column Uplift

Author(s): Yasmeen Al-Sakin, Christopher Higgins, James Newell, and Kent Yu

Publication: Structural Journal

Volume: 120

Issue: 6

Appears on pages(s): 123-135

Keywords: anchor; breakout strength; experimental test; failure; highstrength threaded bars (HSTBs); pile caps; uplift

DOI: 10.14359/51739088

Date: 11/1/2023

Abstract:
The structural performance of four reinforced concrete pile cap specimens anchored by widely used proprietary high-strength threaded bars (HSTBs) and subjected to column uplift loads is investigated. The specimens were full-scale replicas of in-service foundations in terms of geometry, material properties, reinforcement details, and loading conditions. The study also included isolated pullout tests of HSTB anchorages. Two of the specimens were modified by increasing the embedment depth of the column anchor plate to assess effectiveness as a possible retrofit approach. Failure of all specimens was brittle without yielding of embedded reinforcing steel. Moreover, the ultimate pullout capacity of the anchors was not achieved in any of the specimens. ACI 318-19 provisions underestimated the concrete breakout capacity of all specimens and were unable to incorporate the beneficial effects of the column anchor plate modification as it only considered the anchor embedment length and edge distance as critical parameters for calculating strength.