|Session 10.1 - Structural Masonry|
S-W Chuang, Y. Zhuge, P.C. McBean, T-Y Wong and L. Peters
In the last two decades, several seismic retrofitting techniques for masonry structures have been developed and practiced, but rarely validated with experiments and numerical modelling. Further more, the research has been carried out mainly in America and Japan where the risk of major earthquake is high. In Australia, although unreinforced masonry is one of the most popular types of construction, research into seismic retrofitting of masonry structures is rare. The purpose of this research is to develop a new and high strength seismic retrofitting technique for masonry structures. An innovative retrofitting technique is presented in this paper using Fiber Reinforced Polymers (FRP) strips. In the paper, the experimental results of three unreinforced masonry walls retrofitted with FRP strips are presented. All walls were tested under combined constant gravity load and incrementally increased in-plane lateral displacement reversals. The results showed that both the strength and ductility of tested specimens were significantly enhanced with this technique. Seismic retrofitting of unreinforced masonry walls with FRP proved to be an effective and reliable strengthening alternative.
Paper 012: [Read]
Keywords: seismic, retrofitting, FRP, unreinforced masonry walls
M.C. Griffith and G. Magenes
A displacement-based method has been proposed recently for assessing the out-of-plane stability of unreinforced masonry (URM) walls. This is an important development given that this particular failure mode is arguably the most commonly observed failure mechanism in earthquakes in regions where URM construction is widespread. The proposed method is simple and recognizes that a masonry wall will not collapse as long as it does not deflect beyond its point of stability. In essence, estimates of displacement demand, obtained from a displacement response spectrum, are compared to the displacement capacity for the wall. The accuracy of this procedure was verified by a limited number of shaking table tests and non-linear dynamic analyses. In the proposed paper, results of a comprehensive, systematic assessment of this simplified procedure are presented. In this assessment, the URM wall parameters of: initial elastic stiffness and period, maximum strength and ultimate (stability) displacement, ground motion frequency content and intensity were all investigated. It is shown that the key parameters for accurate assessment of a wall’s seismic demand depend only on a wall’s maximum flexural strength and ultimate displacement capacity. It is also shown that these parameters can be predicted with good confidence since they are relatively insensitive to the mechanical properties of the masonry material.
Keywords: unreinforced masonry, displacement-based analysis, walls, brick
A General Model for Analysing Response of Slender Masonry Structures under Multi-component Earthquake Excitations
In this paper, a numerical method is presented to perform non-linear dynamic analyses of coupled transverse and longitudinal oscillations of masonry beams. The beams are analysed with different constraints, when subjected to any dynamic loading type, including vertical and transverse motion imposed at their support. In developing the model, a non-linear constitutive equation giving stress characteristics as a function of strain, for materials with no tensile strength and limited compressive strength, has been used. The model allows the analysis of the dynamic behaviour of masonry slender structures with primarily flexural behaviour, such as towers, under multi-component earthquake excitations. It seems to be a useful model as it requires short computational time, while accounting for the material non-linear behaviour. Results from a case study provide evidence that there are differences in the dynamic response with respect to responses obtained both from a linear elastic analysis and from a simpler non-linear model, where no allowance for a limited compressive strength was made. Subsequently, preliminary results on dynamic response of slender towers under real input ground motion illustrate the ability of the model to supply information which may be used to evaluate indices of global and local structural damage.
Keywords: slender towers, no-tension material, inelastic coupling phenomena, non-linear dynamic.