Dr. Dina D'Ayala University of Bath

Dissipative Anchoring Devices for the Seismic Retrofit of Heritage Masonry Buildings Research by: Dr. Dina D’Ayala 1 Eng. Sara Paganoni th Conference of Earthquake Engineering Lisbon, September 2012 Special Session 24.1 Seismic Retrofit of Masonry Structures

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 Research Rationale and Significance Nayband, Iran Cat 1 Cat 2 Cat 3Cat 4

Validation by dynamic tests with earthquake-like input signal Characterisation by monotonic/cyclic static/dynamic tests Validation of Prototypes Design of prototypes Final design 1) Yielding device 1) Frictional 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 Standard Anchors: performance varies depending on the bond grout/masonry. Locking is a “source” of capacity BUT there is large scattering in performance Friction anchors: the sliding mechanism activates for a load lower than pull-out; relative displacements are possible and anchorage failure prevented

FE and instrumented protypes Computational validation 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 Brickwork Grout E.g. Standard anchor in masonry substratum E.g. Friction anchor – stress at slip load

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