Behaviors of Post-Tensioning and Anchorage Systems REU student: Geoff Madrazo PI’s: Dr. Richard Sause and Dr. James Ricles Graduate Mentor: David Roke ATLSS Center, Lehigh University

Overview Introduction Purpose Objectives Methods and Materials Results Conclusion

Introduction What is post-tensioning? –Used as reinforcement for structural components. –Prestressing structural elements increases their tensile strength. Figure 1 Concrete slab under loading Source: Post-Tensioning Institute

Introduction Structural elements that use post-tensioning: Many types of bridges Elevated slabs Foundations Walls and columns Figure 2 Post-tensioned highway overpass Source: Charlie

Purpose Acquire helpful data on the strength and behaviors of post-tensioning and anchor systems Produce a useful reference for future works which implement post-tensioning

Objectives Test and analyze the PT strand and anchor system Observe and understand behaviors of the anchorage system as documented by Dr. Maria Garlock Find practical scope of use for the strand and anchor in future projects

Methods and Materials wedges PT strand anchor plate Figure 3 Anchorage components Source: DSI Figure 4 Cross-section of anchorage Source: Williams Form Engineering Corp

Methods and Materials PT strand - ASTM A416 –7-wire treated carbon steel –Min. T Y (yield) = kips –Min. T U (breaking) = kips Anchors - ACI code –Guaranteed up to 95% of the breaking strength T U Figures 5 and 6 Wedges and strand Source: Williams Form Engineering Corp

Methods and Materials Static loading tests –2 part wedge vs. 3 part wedge –Stress testing Tensile tests –Wirelock –Copper plates Figure 7 Wirelock compound Source: Millfield Group

Results – So far Static loading tests - test# of wedgesT exp (kips)T exp /T,m ,est (%) Table 1 Test data

Results Low T U High T U Min. T Y kips Avg. T U Figure 8 Stress-strain curve

Results Figure 9 Two-wedge vs. three-wedge plot

Conclusions The anchorage system can not be relied upon to the 95% T U (breaking strength) The PT strand and anchors consistently exceed the yield strength of the strand Three-part wedges perform better under higher loads than two-part wedges

Conclusions There doesn’t appear to be any correlation between the elongation rate (or load rate) and the breaking strength For the Self-Centering Damage-Free Seismic-Resistant Steel Frame Systems project, it is reasonable to design past the yielding of the strands

Acknowledgements David Roke Dr. Sause Dr. Ricles John Hoffner Gene Matlock Dr. Eric Kauffman Chad Kusko ATLSS NEES NSF