Dr. Dina D'Ayala University of Bath

 

Dissipative Anchoring Devicesfor 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

15th Conference of Earthquake EngineeringLisbon, September 2012Special Session 24.1Seismic Retrofit of Masonry Structures

Problem: Out-of-plane damage of wall panels of heritage masonry structuresDevelopment 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 3 Cat 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 deviceElement with reduced:• Cross sectional area• Material strength

-300

-200

-100

0

100

200

300

400

-2000 0 2000 4000 6000 8000

Stre

ss [M

Pa]

Strain [10e-6]

Anchorage

Dissipative element

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 frameworkStandard 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 monitoringS. Giuseppe dei Minimi, L’Aquila, ItalyOut-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