The current European building stock is ageing and requires significant renovation efforts to improve its energy performance and ensure structsural safety. As part of the key actions of the European Green Deal, increased building renovations, a `renovation wave', is needed to ensure that the ambitious EU energy saving and decarbonisation goals can be reached by 2030 and 2050, accordingly. To incentivise renovation further, integrating energy retrofitting with seismic strengthening is explored in this study. A combined energy and seismic retrofitting is investigated across twenty European cities with varied seismic hazard levels and different climatic conditions. Typical building types are defined both in terms of their energy and structural characteristics and are associated to the building population of each city. A monetary metric for combined assessments based on expected annual losses from energy costs and seismic losses is used and an optimum retrofitting scenario is identified. By means of the proposed renovation rate of 3%, a reduction of approximately 30% of primary energy use and CO2 emissions may be achieved within a decade. Taking into account energy costs and costs related to structural damage it is found that a combined retrofitting scheme will reduce substantially the payback periods in moderate to high seismicity regions. In such locations the combined energy and seismic retrofitting is justified and proposed instead of the sole energy retrofitting typically applied today in existing buildings.
The elastic macro-mechanical properties of masonry are investigated herein by taking into account the presence of a weakly non-local heterogeneity within a simple gradient elasticity model. Masonry has a heterogeneous structure composed of masonry units bound by mortar. The homogenisation of masonry walls is a challenging task but also a very appealing method for modelling heterogeneity effects exhibited by masonry elements. In particular, it allows the use of smeared mechanical properties, thus avoiding the need of knowing the exact unit-to-unit and joint-to-joint geometry. Current codes provide very simplified empirical expressions to estimate an isotropic elastic modulus of masonry on the basis of its strength properties. The respective equations which do not take into account the anisotropy of masonry, present high scatter resulting in ambiguous safety. The homogenization argument employed in this work is based on a simple procedure utilising Aifantis' gradient elasticity (GradEla) model. The GradEla model is a straightforward extension of Hooke's law by enhancing it with the addition of the Laplacian of the classical expression of the Hookean stress multiplied by an internal length accounting for the local heterogeneity. It has been successfully used to eliminate singularities from dis-location lines and crack tips, as well as in interpreting size effects. However its use in masonry structures has not yet been explored. A first step in this direction is attempted in this paper with emphasis on obtaining practical easy-to-use results rather than exhausting all other possibilities and complexities encountered in GradEla and its generalisation, as well as in more involved homogenisation procedures. In our analysis uniform vertical, horizontal and shear loads are assumed to act on the boundaries of the representative volume/surface element. The components of masonry are assumed to follow a gradient elastic stress distribution resulting in a gradient elastic homogenised model (GREHM). GREHM comprises a set of closed-form concise equations which estimate the elastic moduli in the longitudinal and transverse directions, the shear modulus and the Poisson's ratio. The aforementioned orthotropic material properties are verified using experimental results and also, compared to other homogenisation models. The validation shows that the proposed equations can effectively estimate with considerable precision the elastic properties of masonry walls. To illustrate the resulting estimation of the or-thotropic elastic properties, normalised graphs are provided.