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

1. Behavior and Design of Cast-in-Place Anchors under Simulated Seismic Loading (NEES-Anchor) Chadd Lane Jian Zhao Assistant Professor WisCamp Undergraduate Research Summer 2009 University of Wisconsin Milwaukee

2. Abstract Motivation: • Structural safety • Cracks in the cement, broken anchors, or shifting of the beams. • Maximize structural safety • Saving time and money

3. INTRODUCTION • Behavior of anchor connections • Concrete cracking in tension • Current design regulations • Limited guidance

4. Problem Statement: • How does one maximize structural safety with the number of anchors, anchor design, and location? • How does one disperse the weight of a large beam evenly among all the anchors?

5. Key Terminology Concrete Spall Cone— Steel Breakage— Anchor Pullout— Bond Failure— Edge Distance and Spacing Reduction—

6. Key Terminology continued • Spalled concrete— split, chip, or to break into smaller pieces

7. Key Terminology coninued • A material can be loaded in: a) compression b) tension c) shear

8. Approach: • Computer simulation • failure rate of cement and anchors • Real life seismic loading simulation. • Confirm computer simulations • How the cement and anchors should look when they fail. • Understand the full nature of cement and anchors. • Calculations • How to disperse the weight of the large beam evenly amongst all anchors evenly

9. Anchor Failure Example • One of the anchor bolts was fractured • The other bent under a combined tension and shear action. • The top layer of concrete spalled such that the hairpin, with an intention to help the anchor connection to resist shear, was displaced outside the anchor connection. • Note that the failure of the anchor connection might have contributed to the total collapse of the industrial building.

10. Experimental tests • The experimental tests include the ongoing single-anchor tests at UWM and the anchor group tests (to be conducted at Illinois in 2010). • Anchors in every test group are subjected to these loadings: tension and shear • The loading frame shown right are set for the various loading patterns. Meanwhile • http://www.youtube.com/watch?v=3z4YLUqOysI

11. Experimental tests example • The anchor position is chosen to enable concrete breakout failure. • The same configurations will be cast and tested with various anchor reinforcements to explore practical and effective reinforcement details that can prevent the concrete breakout failure modes. • Headed bars and reinforcement cages are under consideration.

12. Analytical studies • The single anchor tests will be simulated using finite element models to optimize the anchor reinforcement details. • The proposed design procedures will be incorporated in the MathCAD programs.

13. RESEARCH • Using the NEES facility at the University of Illinois. • Obtain detailed experimental - cyclic shear and combined tension-shear. • Evaluate current seismic anchor design provisions and develop new • design methodologies and the use of anchor reinforcements. • Create fiber-based connection interface models. • Promote a timely transfer of knowledge

14. EDUCATION, OUTREACH, & Training • This UWM project is being led by Dr. Zhao • Two graduate students Joshua Johnston and Derek Petersen from UWM and one graduate student from UC are working on the project. • Two undergraduate students Alice Muehlbauer and Chadd Lane.

15. SUMMARYNEES-Anchor • Seismic behavior and design of cast-in-place anchors/studs using NSF NEES facility and local resources. • Anchor tests that simulate a combination of concrete breakout failure under shear and/or tension. • The focus will be also on the improvement of anchor behavior through using anchor reinforcements. • The research program will generate critical knowledge that advances the seismic design of anchor connections, as well as providing essential information for future revision of anchorage design regulations.

16. Thanks • Dr. Zhao and his team • WisCamp and McNair Staff and students • All other people that played a roll in this great experience.