In this paper an extensive experimental study is presented in which the efficiency of seismic strengthening of brick masonry walls, typical in Slovenia and wider region, is analyzed. The results of cyclic shear tests of 24 walls are presented. The walls were strengthened using different materials and different layouts of the reinforcement. Externally bonded glass and carbon composites were used for strengthening and were applied to the wall by either cementitious mortar or epoxy resin. 12 walls were first tested up to the point where repair was still feasible and then strengthened and retested until collapse to study the efficiency of repair/strengthening. The rest were strengthened in the undamaged state. In addition to cyclic shear tests, the tests of the composite-masonry bond in double shear lap configuration were also performed. Results of cyclic shear tests show significant differences between different types of strengthening with shear strength resistance improvements of up to 130%. The displacement capacity was barely increased, except for one type of strengthening, thus confirming the importance of correct strengthening layout and anchoring. The observed failure mechanisms were characterized by debonding of coating which resulted in sudden resistance and stiffness degradation, leading to brittle collapse of the walls. The performance of composite-to-masonry bond in double shear lap test was significantly better than in cyclic shear tests. Finally, the resistance of strengthened walls is estimated using simple numerical models based on measured bond strength.
COBISS.SI-ID: 2292327
Some aspects of testing and experimental research of seismic behaviour of masonry walls and buildings, based on the experience obtained at Slovenian National Building and Civil Engineering Institute, are discussed. Typical testing methods are presented and the influence of governing parameters, such as boundary conditions, loading protocols and scale effects, on failure mechanisms and test results, analyzed. The conditions to be fulfilled when testing models of masonry buildings on shaking tabels, are discussed. Finally, typical examples of experimental research to investigate various issues of seismic behaviour of masonry buildings are also briefly described.
COBISS.SI-ID: 2229351
A full scale specimen consisting of a set of two three-storey plain masonry shear walls with openings, laterally braced with cross-walls and connected with r.c. floor slabs has been tested by subjecting it to in-plane acting cyclic seismic loads. The response of the specimen was observed with special attention paid to the behaviour of central piers at each floor level. Typical storey shear mechanism governed the behaviour of the specimen. Shear failure of central piers was observed, characterized by diagonal cracks in the walls.
COBISS.SI-ID: 2228583
To research the efficiency of technologies of strengthening of earthquake-damaged masonry buildings built from hollow clay block, an assemblage of three-storey full scale plain masonry shear walls has been tested after strengthening it by fibre reinforced polymers (FRP). Constant vertical load, typical for residential building was applied by means of a hydraulic system. Seismic loads, acting cyclically at the floor levels, were applied in the form of a linear force pattern along the height. The walls were first tested in unstrengthened state up to the occurrence of considerable damage (beyond maximum resistance limit state) and then strengthened by a system based on FRP coating. After that, the walls were retested until collapse. Because the collapse and damage occurred on the first and second floor, respectively, an additional test of only the top floor was performed. The results of the tests show that adequate strengthening solutions provide significantly improved seismic behaviour. If properly applied and anchored, the coating and the wall act together as a composite material and respond in shear.
COBISS.SI-ID: 2269543
A seismic loss estimation methodology for masonry buildings is introduced. It enables the estimation of losses based on the simulated damage at the building’s level with consideration of epistemic and aleatoric uncertainties. The modelling uncertainties are incorporated through a set of structural models, which are defined by utilizing the Latin Hypercube Sampling technique. The damage of the building is simulated by the pushover analyses, whereas the relationship between the engineering demand parameter at the level of the building and the seismic intensity is estimated by incremental dynamic analysis, which is performed for the single-degree-of-freedom model taking into account the ground motion randomness and the modelling uncertainties. The loss estimation methodology requires the use of the fragility functions, which were in the case of masonry walls established from the experimental database, whereas for the other components, they were adopted according to FEMA P-58-1. The proposed method is demonstrated by means of an example of a three-storey masonry building. It is shown that consideration of the effect of modelling uncertainty increased the probability of collapse in 50 years and the expected annual loss, respectively, for factors of 1.5 and 1.25.
COBISS.SI-ID: 7411297