Shear modulus and stiffness of brickwork masonry: An experimental perspective
Masonry is a composite non-homogeneous structural material, whose mechanical properties depend on the properties of and the interaction between the composite components - brick and mortar, their volume ratio, the properties of their bond, and any cracking in the masonry. The mechanical properties of masonry depend on the orientation of the bed joints and the stress state of the joints, and so the values of the shear modulus, as well as the stiffness of masonry structural elements can depend on various factors. An extensive testing programme in several countries addresses the problem of measurement of the stiffness properties of masonry. These testing programs have provided sufficient data to permit a review of the influence of different testing techniques (mono and bi-axial tests), the variations caused by distinct loading conditions (monotonic and cyclic), the impact of the mortar type, as well as influence of the reinforcement. This review considers the impact of the measurement devices used for determining the shear modulus and stiffness of walls on the results. The results clearly indicate a need to re-assess the values stated in almost all national codes for the shear modulus of the masonry, especially for masonry made with lime mortar, where strong anisotropic behaviour is in the stiffness properties.
Lateral Stiffness of Brick Masonry Infilled Plane Frames
In a companion paper, a new finite element technique for the analysis of brickwork infilled plane frames under lateral loads has been presented. In the present paper, the influence of the masonry infill panel opening in the reduction of the infilled frames stiffness has been investigated by means of this technique. A parametric study has been carried out using as parameters the position and the percentage of the masonry infill panel opening for the case of one-story one-bay infilled frame. The investigation has been extended to the case of multistory, fully or partially infilled frames. In particular, the redistribution of action effects of infilled frames under lateral loads has been studied. It is shown that the redistribution of shear force is critically influenced by the presence and continuity of infill panels. The presence of infills leads, in general, to decreased shear forces on the frame columns. However, in the case of an infilled frame with a soft ground story, the shear forces acting on column...
Speci fi cation Test for Panel Data Models with Interactive Fixed E ff ects ∗
In this paper, we propose a consistent nonparametric test for linearity in a large dimensional panel data model with interactive fixed effects. Both lagged dependent variables and conditional heteroskedasticity of unknown form are allowed in the model. We estimate the model under the null hypothesis of linearity to obtain the restricted residuals which are then used to construct the test statistic. We show that after being appropriately centered and standardized, the test statistic is asymptotically normally distributed under both the null hypothesis and a sequence of Pitman local alternatives by using the concept of conditional strong mixing that was recently introduced by Prakasa Rao (2009). To improve the finite sample performance, we propose a bootstrap procedure to obtain the bootstrap -value. A small set of Monte Carlo simulations illustrates that our test performs well in finite samples. An application to an economic growth panel dataset indicates significant nonlinear relationships between economic growth, initial income level and capital accumulation.