National Science Foundation

Behavior and Design of Cast-in-Place Anchors
under Simulated Seismic Loading (NEES-Anchor)

NEESinc

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Principal Investigators:
Jian Zhao
Bahram Shahrooz
Xiangdong Tong

Sponsors:
National Science Foundation
Network for Earthquake Engineering Simulation

Graduate Students: 
Joshua Johnston
Derek Peterson

Undergradduate Students:
Kevin O'Connor and Brian Petrin

Composite construction

Please visit NEES Project Warehouse for the test data
Draft Final Reports:

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Project Description:

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    Headed anchors/studs are commonly used to connect steel members (e.g., columns, girders, or braces) and concrete elements (e.g., foundations, walls, or columns, respectively). The concrete elements may experience substantial damage (e.g., large cracking) during an earthquake; thus, a good understanding of the behavior of anchors in cracked concrete is a prerequisite to ensuring satisfactory seismic performance and safety of structures. Current seismic design guidelines, represented by the Appendix D of ACI 318-08 document, are not adequate particularly in terms of guidelines for design of headed anchors/studs in significantly cracked concrete.  The design provisions seem to tacitly rely on reserved capacity of anchors, and perceived ductile failure modes due to steel fracture. Both of the rationales are questionable because of paucity of supporting data for anchor behavior under seismic loading. In addition, the interaction equations for anchors under combined cyclic tension-shear have not been verified experimentally. As a result, many anchor connections, including those taking advantage of additional reinforcement around the anchors, are often implemented in practice without supporting experimental data, thereby leading to potential uncontrollable structural performance. The knowledge gap is due partly to the limited equipment available to the community before the NEES facilities became operational in 2004. The research team will investigate the fundamental behavior of headed anchors/studs under simulated seismic loading and verify and improve the anchor connection details commonly seen in practice. As part of the proposed analytical studies, the research team will develop connection interface models to improve model-based simulations and to assist in the development of performance-based engineering methodologies. Engineers, students (including those from underrepresented groups), and general public will be involved in the proposed research through a focused education and outreach program. The research will advance the current seismic design practice and enhance our ability to meet the future earthquake challenges.

Anchorage Design Codes and Analysis Tools:

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  • ACI 318-08 Appendix D
  • PCI design handbook 6th edition
  • European regulations
Experimental Tests:

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  • Phase I: Unreinforced single anchors subjected to cyclic loading (Spring 2010)
  • Phase III: Reinforced single anchors subjected to tension  (Spring 2011)
  • Phase IV: Anchor groups in plastic hinge zones of a concrete wall at NEES-UIUC (Summer 2011)
  • Other Tests: Double shear tests of anchor rods with exposed lengths  (Spring 2011)
Analytical Studies:

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  • Simulations of concrete breakout
  • Simulations of exposted anchors in shear
  • Development of zero-length section elements for steel-concrete member interfaces

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