Latest findings on the behaviour factor q for the seismic design of URM buildings

Abstract

Recent earthquakes as the 2012 Emilia earthquake sequence showed that recently built unreinforced masonry (URM) buildings behaved much better than expected and sustained, despite the maximum PGA values ranged between 0.20 -0.30g, either minor damage or structural damage that is deemed repairable. Especially low-rise residential and commercial masonry buildings with a code-conforming seismic design and detailing behaved in general very well without substantial damages. The low damage grades of modern masonry buildings that was observed during this earthquake series highlighted again that codified design procedures based on linear analysis can be rather conservative. Although advances in simulation tools make nonlinear calculation methods more readily accessible to designers, linear analyses will still be the standard design method for years to come. The present paper aims to improve the linear seismic design method by providing a proper definition of the qfactor of URM buildings. These q-factors are derived for low-rise URM buildings with rigid diaphragms which represent recent construction practise in low to moderate seismic areas of Italy and Germany. The behaviour factor components for deformation and energy dissipation capacity and for overstrength due to the redistribution of forces are derived by means of pushover analyses. Furthermore, considerations on the behaviour factor component due to other sources of overstrength in masonry buildings are presented. As a result of the investigations, rationally based values of the behaviour factor q to be used in linear analyses in the range of 2.0 to 3.0 are proposed.

Investigating the Reliability of Nonlinear Static Procedures for the Seismic Assessment of Existing Masonry Buildings

“…In the case of linear approaches, the use of q-factors is one way to account for the intrinsic ability of a structure to resist energy dissipation [12,13]. For the seismic design of new URM buildings, q-factor reference values, able to implicitly account for plastic behavior up to the near-collapse (NC) limit state, are available [14]. Their use, combined with that of capacity design structural details, aims to ensure the required seismic performance.…”

Effect of Soil Anisotropy on Ground Motion Characteristics

“…This is illustrated in damage assessments of buildings in the countries of Turkey [4][5][6], Greece [7], Iran [8], Mexico [9], Korea [10], Pakistan [11], and Nepal [12]. Numerous scholars have extensively researched the seismic resilience of engineering structures [13][14][15][16]. The analysis of structures for seismic resistance utilizes a range of methodologies, encompassing response spectrum analysis, the base shear method (quasi-static method), and time history analysis.…”

Particular Strength Criteria for Microstructural Analysis of Masonry

“…2) Masonry as a composite medium of homogeneous fragments based on the principles of structural modelling with individual mechanical characteristics of its constituent materials. Based on these 2 principles, authors such as [5], [6], [20]- [25], [9], [13]- [19] among others, use 3 approaches for numerical modelling of masonry using FEM: the macromodel, where the masonry is considered as a continuous and homogeneous material; the micromodel consisting of the constituent materials and contact interfaces; and the simplified micromodel considering extended brick units and conditional interfaces (Fig. 1).…”