Experimental and Numerical Assessment of Seismic Retrofit Solutions for Stone Masonry Buildings

Gabriele Guerrini,Christian Salvatori,Andrea Penna,Ilaria Senaldi

doi:10.3390/geosciences11060230

Gabriele Guerrini, Christian Salvatori + Show 2 more

Open Access

https://doi.org/10.3390/geosciences11060230

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Abstract

This paper presents an experimental and numerical study on different retrofit solutions for stone masonry buildings with timber diaphragms in earthquake-prone regions, aiming at enhancing wall-to-diaphragm connections, diaphragms’ stiffness, and masonry properties. The experimental results of incremental dynamic shake-table tests on three full-scale two-story buildings, complemented by material and component characterization tests, are initially summarized. The first building specimen was unstrengthened. The second one was retrofitted at the floor and roof levels with improved wall-to-diaphragm connections and a moderate increase in diaphragm stiffness. Connections were also improved in the third specimen together with a significant enhancement of diaphragm stiffness. The calibration of two numerical models, versus the experimental response of the retrofitted building specimens, is then presented. The models were further modified and reanalyzed to assess the effects of masonry mechanical upgrades, which could be achieved in practice through deep joint repointing or various types of jacketing. These solutions were simulated by applying correction coefficients to the masonry mechanical properties, as suggested by the Italian building code. The effectiveness of the experimentally implemented and numerically simulated interventions are discussed in terms of strength enhancement and failure modes.

Highlights

Masonry constitutes most of the building stock worldwide, especially concerning heritage construction systems
This paper presents an experimental and numerical study on different retrofit solutions for stone masonry buildings with timber diaphragms in earthquake-prone regions, aiming at enhancing wall-to-diaphragm connections, diaphragms’ stiffness, and masonry properties
The second specimen was retrofitted by improving its wall-to-diaphragm connections with steel and reinforced masonry (RM) ring beams at the first floor and roof level, respectively; diaphragm stiffness was only slightly increased by adding a layer of 45-degree oriented timber planks

Summary

Introduction

Masonry constitutes most of the building stock worldwide, especially concerning heritage construction systems. Masonry disgregation and leaf delamination typical of poor bond and constituents should be preliminarily addressed by material enhancements In light of these considerations, three main strategies interact with each other in the retrofit of a stone masonry building [21,22]: 1. The second specimen was retrofitted by improving its wall-to-diaphragm connections with steel and reinforced masonry (RM) ring beams at the first floor and roof level, respectively; diaphragm stiffness was only slightly increased by adding a layer of 45-degree oriented timber planks. Strengthening interventions for the enhancement of the masonry material have been assessed numerically by repeating the pushover analyses after the application of correction coefficients to the masonry mechanical properties, as suggested by the Italian building code [59,60], since these retrofit details could not be explicitly modeled through the chosen macroelement discretization. The effectiveness of different retrofit approaches and combinations is discussed

Experimental Program

Masonry Structures

Timber Floor and Roof Structures

Material Properties and Masses

Testing Protocol and Results

Modeling Strategy

Calibration of Masonry Material Properties

Calibration of Membrane and Beam Element Stiffness

Comparison between Numerical and Experimental Results

Summary and Conclusions