Abstract

The inadequate seismic performance of existing masonry buildings is often linked to the excessively low in-plane stiffness of timber diaphragms and the poor quality of their connections to the walls. However, relevant past studies and seismic events have also shown that rigid diaphragms could be detrimental for existing buildings and do not necessarily lead to an increase in their seismic performance. Therefore, this work explores the opportunity of optimizing the retrofitting of existing timber floors by means of a dissipative strengthening option, consisting of a plywood panel overlay. On the basis of past experimental tests and previously formulated analytical and numerical models for simulating the in-plane response of these retrofitted diaphragms, in this work nonlinear incremental dynamic analyses were performed on three case–study buildings. For each structure three configurations were analyzed: an as-built one, one having floors retrofitted with concrete slabs and one having dissipative diaphragms strengthened with plywood panels. The results showed that the additional beneficial hysteretic energy dissipation of the optimized diaphragms is relevant and can largely increase the seismic performance of the analyzed buildings, while rigid floors only localize the dissipation in the walls. These outcomes can contribute to an efficient seismic retrofitting of existing masonry buildings, demonstrating once more the great potential of wood-based techniques in comparison to the use of reinforced concrete for creating rigid diaphragms.

Highlights

  • Accepted: 24 November 2021Existing unreinforced masonry (URM) constructions featuring timber diaphragms as floors and roofs often constitute a large part of the building stock and architectural herit‐age for several seismic‐prone countries

  • Starting from building building 1 (B1), it can be noticed that as‐built configuration B1‐AB already collapsed at a low level of intensity due to the out‐of‐plane failure of walls or gables

  • With floors stiffened with a concrete slab, a great improvement in the capacity of the building was obtained, mainly be‐

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Summary

Introduction

Existing unreinforced masonry (URM) constructions featuring timber diaphragms as floors and roofs often constitute a large part of the building stock and architectural herit‐. The vulnerability of such buildings to earth‐. Sonry, excessive in‐plane flexibility of timber floors, and the absence of effective connec‐. In this framework, several retrofitting methods for timber diaphragms [1,2,3,4,5,6,7,8,9,10,11,12] and timber–masonry connections [13,14,15,16] have been developed in the recent years, progres‐. The aim of all the techniques was to improve the in‐plane stiffness of the floors, so that they could act as Published: 1 December 2021

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