The results of tests of plain and confined masonry walls with h/l ratio equal to 1·5, made at 1 : 5 scale, have been used to develop a rational method for modelling the seismic behaviour of confined masonry walls. A trilinear model of lateral resistance-displacement envelope curve has been proposed, where the resistance is calculated as a combination of the shear resistance of the plain masonry wall panel and dowel effect of the tie-columns' reinforcement. Lateral stiffness, however, is modelled as a function of the initial effective stiffness and damage, occurring to the panel at characteristic limit states. Good correlation between the predicted and experimental envelopes has been obtained in the particular case studied. The method has been also verified for the case of prototype confined masonry walls with h/l ratio equal to 1·0. Good correlation between the predicted and experimental values of lateral resistance indicates the general validity of the proposed method.
Two models of a typical confined masonry building, which conforms to the requirements of Eurocode 8 for simple buildings, have been tested on a shaking-table. Model test results indicate that prototypes of the tested type and size will be able to withstand, with moderate damage to the walls, strong earthquakes with peak ground acceleration 0·8g, and will not collapse when subjected to repeated shaking with PGA more than 1·3g. Taking into consideration the observed predominant first vibration mode shape and shear-beam-type shape of vibration, a rational method for seismic resistance verification of confined masonry structures has been proposed, modelling the confined masonry shear walls as frames. Good correlation between experimental and calculated envelopes has been obtained, indicating the validity of the proposed method. The measured response of the models has also been used to analyse the value of behaviour factor q proposed by EC 8 for confined masonry structures.
The efficiency of improving the seismic resistance of old masonry buildings by means of seismic isolation and confining the structure with CFRP laminate strips has been investigated. Five models of a simple two-story brick masonry building with wooden floors without wall ties have been tested on the shaking table. The control model has been built directly on the foundation slab. The second model has been separated from it by a damp-proof course in the form of a PVC sheet placed in the bed-joint between the second and the third course, whereas the third model has been isolated by rubber isolators placed between the foundation slab and structural walls. Models four and five have been confined with CFRP laminate strips, simulating the wall ties placed horizontally and vertically at floor levels and corners of the building, respectively. One of the CFRP strengthened models has been placed on seismic isolators. Tests have shown that a simple PVC sheet damp-proof course cannot be considered as seismic isolator unless adequately designed. Tests have also shown that the isolators alone did not prevent the separation of the walls. However, both models confined with CFRP strips exhibited significantly improved seismic behavior. The models did not collapse even when subjected to significantly stronger shaking table motion than that resisted by the control model without wall ties.
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