Proposition of stiffness reduction in analysis of clay brick masonry under cyclic/seismic loads

Jan Kubica

doi:10.21595/jme.2018.20417

Abstract

Analysis of masonry buildings situated on seismic or mining activity terrains as well as subjected to dynamic human-induced vibrations and influences should base on the appropriated mechanical properties of masonry. There main parameters describing bending and shear stiffness’s of masonry shear walls are modulus of elasticity as well as shear modulus. Values of these parameters under seismic or cyclic loading are rapidly coming down due to the inelastic behaviour of the masonry. The problem of degradation of modulus of elasticity E as well as shear modulus G is presented and discussed based on the tests results of three types of clay brick masonry wall specimens subjected to compressive cyclic loads and some specimens under cyclic horizontally and vertical shearing (in one cycle) carried out at the Department of Structural Engineering of the Silesian University of Technology in Gliwice as well as results obtained by other researchers and available at the technical publications. As result there is proposed to determine the value of modulus of elasticity as 40 % of calculated with accordance with Eurocode 6 [1]. In case of shear modulus it is suggested to determine the G values as 20 % of initial values of modulus of elasticity, that is mean 50 % less than recommended in current version of Eurocode 6 [1] and perfectly correct with requirements given in Eurocode 8 [2].

Highlights

Analysis of masonry buildings situated on seismic or paraseismic terrains as well as subjected to dynamic human-induced vibrations and influences should base on the appropriated analytical models and procedures allowing calculation of resistance and deformability of masonry shear walls
Acceptance in the calculations of masonry walls the values of mechanical parameters of masonry as given in Eurocode 6 [1], usually overstated because they take into account the elastic behaviour of the material, reduces the load-bearing capacity of shear walls and underestimates their deformability
Problem of shear stiffness degradation is analysed by author for many years, especially from the point of view of calculating masonry buildings in the areas of paraseismic influences caused by mining activity

Summary

Introduction

Analysis of masonry buildings situated on seismic or paraseismic terrains as well as subjected to dynamic human-induced vibrations and influences should base on the appropriated analytical models and procedures allowing calculation of resistance and deformability of masonry shear walls. In case of seismic or paraseismic of loadings and influences is necessary to take into consideration that the main material properties of masonry, like modulus of elasticity as well as shear modulus under these types of loading are rapidly coming down due to the inelastic behaviour of the masonry This phenomenon is not taken into account in standard’s regulations: masonry code Eurocode 6 [1] but Eurocode 8 [2] in load bearing elements is recommended 50 % reduction of flexural and shear stiffness of the uncracked elements. It should be necessary to suggest appropriate recommendations for shear stiffness reduction and checking if suggested in Eurocode 8 [2] 50 % reduction is sufficient into design of one of the most popular type of masonry made of clay solid brick with cement-lime mortar

Theoretical considerations

Test’s data and discussion of the problem

Experimental results and its discussion

Conclusions