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15 th Conference of Earthquake Engineering Lisbon, September 2012 Special Session 24.1 Seismic Retrofit of Masonry Structures. Dissipative Anchoring Devices for the Seismic Retrofit of Heritage Masonry Buildings. Research by: Dr. Dina D’Ayala 1 Eng. Sara Paganoni 2
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15th Conference of Earthquake Engineering Lisbon, September 2012 Special Session 24.1 Seismic Retrofit of Masonry Structures Dissipative Anchoring Devices for the Seismic Retrofit of Heritage Masonry Buildings Research by: Dr. Dina D’Ayala1 Eng. Sara Paganoni2 1 d.d’ayala@ucl.ac.uk, 2 S.Paganoni@bath.ac.uk
Research Rationale and Significance Cat 1 Cat 2 Cat 3 Cat 4 • Problem: Out-of-plane damage of wall panels of heritage masonry structures • Development of anchoring device for: • Control of displacement • Reduction of acceleration • Reduction of stress concentration Nayband, Iran
Validation of Prototypes Characterisation by monotonic/cyclic static/dynamic tests Validation by dynamic tests with earthquake-like input signal Design of prototypes Final design 1) Frictional device 1) Yielding device • Element with reduced: • Cross sectional area • Material strength Mechanism based on Coulomb friction: F//=n∙m∙F┴
Test of prototypes in masonry specimens • Experimental programme: • Pull-out tests; • Cyclic tests of T-shape walls; • Shaking table tests within the FP7-SERIES framework Friction anchors: the sliding mechanism activates for a load lower than pull-out; relative displacements are possible and anchorage failure prevented Standard Anchors: performance varies depending on the bond grout/masonry. Locking is a “source” of capacity BUT there is large scattering in performance
FE and instrumented protypes Computational validation E.g. Friction anchor – stress at slip load Brickwork Grout E.g. Standard anchor in masonry substratum On-site validation through monitoring S. Giuseppe dei Minimi, L’Aquila, Italy Out-of-plane damage of façade as consequence of April 2009 earthquake Microtremor recorded by bending gauge and accelerometer Position of instrumented yielding anchor
Conclusions & further developments • The dissipative anchoring devices are able to: • Provide stable and robust performance for varying frequency/amplitudes/number of cycles of exciting signal • Prevent or delay damage to parent material, thus ensuring occupants’ safety and preservation of historic materials • Comply with prescriptions regarding the use of ductility in the strengthening of connections • Future research programmes include: • Continuous monitoring and development of software for early warning • Development of dimensioning procedure