A high proportion of New Zealand's clay brick unreinforced masonry (URM) structures have not been retrofitted to resist earthquake forces, and in particular to prevent out-of-plane failures which are the most critical deficiencies of URM buildings. Despite a number of seismic improvement techniques having been applied previously there is a significant lack of experimentally validated simple and cost-effective solutions that also consider the impact on the building tenants, aesthetics and heritage building fabric. The main objectives of the research presented herein were to develop and validate seismic securing techniques for URM solid- and cavity-walls that satisfied the above conditions. Full-scale shake-table testing of two cavity and three double-leaf solid clay brick URM walls was undertaken. The vertical timber framing that is typically considered to be a non-structural support for the inner wall lining was used as part of the retrofit solution and was fixed to the wall using mechanical screw-ties in order to form a strong-back. The intended outcomes of the research reported herein included (i) measuring via laboratory testing the improvement of seismic capacity in terms of peak ground acceleration (PGA) achieved and maximum out-of-plane displacement experienced by the URM solid- or cavity-walls due to strong-back retrofit installation; (ii) comparing the performance of different strong-back configurations; (iii) providing construction details, and providing analytical formulations for response prediction.
The study of the behaviour of masonry arches represents a complex problem, which involves different aspects that can significantly affect the load bearing capacity of such structures. In this regard, geometrical imperfections, such as the irregular shape of the arch blocks, the initial position of the first and last voussoirs (boundary conditions), the alignment between the adjoining blocks and the rounded corners of each block, play an important role. An experimental campaign was conducted on a toy arch made by eleven irregular blocks, with the aim of evaluating the effect of such irregularities. A numerical model was developed basing on lower bound (LB) and upper bound (UB) limit analysis approaches (referred to as the static and the kinematic theorem, respectively). A linear programming (LP) solving algorithm was implemented in the software MATLAB and used to solve the minimization/maximization problems. The probability distribution of each considered nonlinearity was estimated, the results of the numerical analysis were correlated with the experimental outcomes and a Montecarlo simulation was carried out to validate the hypothesised probability distributions.
The in-plane stiffness of timber diaphragms commonly found in vintage unreinforced masonry (URM) buildings is largely determined by the rigidity of the fastener connections. Currently in the literature, however, there is limited experimental data on the behavior of floorboard-to-joist connections, and consequently the aim of the present study was to supplement that knowledge. The existing data provided the paramount input parameters for the finite element modeling of timber diaphragms, in order to model and validate the results obtained from the experimental testing of full-scale timber diaphragms. The floorboard-to-joist connections were extracted from two vintage URM buildings and were tested using three different test setups to address various realistic loading configurations. In addition, the floorboard-to-joist connections were improved using new nails or new screws. Specimens comprising plywood or fire-rated gypsum-board panels connected to the salvaged floorboards or joists were also tested as a method for improving the overall diaphragm lateral behavior. The experimental study of timber diaphragm fastener connections consisted of 43 samples, of which the results are presented here.
The current study addresses the final stage of a three-part research program in which a variety of unreinforced masonry (URM) walls were physically tested in situ to measure out-of-plane (OOP) behaviour, were assessed for force-based (i.e., strength) performance, and finally were assessed for displacement-based performance. Predictive assessments were carried out using previously published predictive models, and the comparison of experimental to predictive displacement-based performance is the focus of the study reported herein. Displacement-based criteria were applied at selected points on the force-displacement backbone curve. Other researchers have found weak correlation between the results of experimental data sets and the predictive model that isincorporated within multiple internationally recognised standards such as ASCE 41 and FEMA 356 for URM infill wall drift performance. Furthermore, in situ conditions for URM walls rarely reflect the idealised conditions assumed in analytical predictive models, leading to practicing engineers being uncertain as to which analytical models and inputs are most appropriately applied. In the current study, the predictive results were compared to previously reported experimental results of twelve tests on existing URM walls performed in situ, representing a variety of geometries, boundary conditions, pre-test damage states, and material properties. In general, use of the existing predictive methods results in the over-prediction of the measured displacement parameters, which is likely due to most of the predictive methods being based on historical walls tests in one-way spanning conditions and without rigid restraints capable of effectuating arching action in the wall, in contrast to the wall test conditions in the current study.
