In-plane and out-of-plane seismic damage of masonry infills in existing r.c. structures: the case study of De Gasperi-Battaglia school in Norcia

AbstractA significant correlation between the in-plane (IP) and out-of-plane (OOP) damage propagation of masonry infills (MIs) is frequently observed after strong earthquakes, posing a serious problem as regards vulnerability of public buildings such as schools. The present work is aimed at identifying the effects of different IP and OOP modelling assumptions of MIs on their seismic damage. To this end, the state secondary school De Gasperi-Battaglia in Norcia (Italy), object of monitoring by the Department of Civil Protection since 2000, is investigated for the heterogeneity of infill typologies. The school is composed of a basement and three storeys above ground level, with a reinforced concrete (r.c.) framed structure having a long-shaped rectangular plan. Two typologies can be identified in terms of transverse layout of MIs: (i) double-leaf interior partitions, made of hollow clay bricks; (ii) double-leaf exterior infill walls, constituted by facade solid bricks paired with hollow clay bricks. In addition, partial height infills in the longitudinal direction, due to classroom windows, make the columns susceptible to short column effects. MIs are represented by a five-element macro-model predicting both in-plane (IP) and out-of-plane (OOP) behaviour through a horizontal nonlinear truss and four diagonal nonlinear beam elements, respectively. Stiffness and strength values in the OOP direction are also reduced considering the evolution of the IP damage. Three assumptions are investigated for the behaviour of structural MIs: i.e. elastic both IP and OOP; inelastic IP and elastic OOP; inelastic both IP and OOP. Bare and infilled test structures are subjected to biaxial spectrum-compatible accelerograms, to evaluate the IP and OOP damage levels and effectiveness of the OOP simplified verification proposed by seismic codes

Nonlinear modelling of the in-plane-out-of-plane interaction in the seismic analysis of masonry infills in r.c. framed buildings

Abstract A five-element macro-model, with four diagonal out-of-plane (OP) nonlinear beams and one horizontal in-plane (IP) nonlinear truss, takes into account the OP and IP failure modes occurring, in the event of seismic loading, for masonry infills (MIs) inserted in reinforced concrete (r.c.) framed buildings. Pivot hysteretic models predict the nonlinear IP and OP force-displacement laws of the infill panel, based on geometrical rules defining loading and unloading branches. Firstly, a calibration of the proposed IP-OP interaction model of MIs is carried out considering full-scale experimental results of traditional masonry typologies. To evaluate the interaction, the numerical results of simultaneous IP and OP cyclic tests on MIs at the top, intermediate and lowest levels of an existing six-storey r.c. framed building are presented, assuming different displacement histories: i) OP loading faster than IP, at the sixth storey; ii) equal IP and OP loading, at the third storey; iii) IP loading faster than OP, at the first storey

Code-Oriented Floor Acceleration Response Spectra of RC Framed Buildings Accounting for Nonlinear Response of Masonry Infills

Modern code-oriented elastic floor response spectra formulations for RC framed structures do not take into account effects of non-negligible nonstructural components in terms of mass and stiffness, such as masonry infills (MIs). MIs nonlinear behaviour can be represented through the combination and mutual interaction between the in-plane (IP) and out-of-plane (OOP) responses. The present work is aimed at identifying the effect of IP and OOP nonlinear modelling assumptions on floor acceleration response spectra, consistently with the required seismic intensity level for simplified verification of life-threatening nonstructural elements. To this end, a spatial one-bay multi-storey shear-type model is considered as equivalent to infilled RC framed buildings with common double-leaf MIs. Additional variability of the following design parameters is considered: number of storeys (three, five and seven); behaviour factor (low, 1.5, medium, 3, and high, 4.5); OOP strength of MIs, with lower and upper bound values corresponding to oneand two-way arching mechanisms, respectively. A recently proposed computer code, that includes a five-element nonlinear infill macro-model comprising four diagonal OOP beams and one (horizontal) central IP truss, is considered for the numerical investigation. The proposed algorithm modifies stiffness and strength values of MIs in the OOP direction on the basis of simultaneous or prior IP damage and vice versa. Moreover, a lumped plasticity model describes the inelastic behaviour of RC frame members. Biaxial spectrum-compatible accelerograms are considered at life-safety limit state provided by the Italian seismic code. A simplified code-oriented formulation for the evaluation of floor response spectra of infilled RC framed structures is proposed. Nonstructural maximum acceleration is firstly evaluated by means of vertical and nonstructural amplification factors. Continuous wavelet transforms are used to calibrate parameters that define the resonance region width, accounting for moving resonance due to nonlinearity and higher modes effects. Parabolic and Gaussian curves are considered in order to reproduce preand post-resonance regions, respectively. Finally, a code-oriented proposal is compared to exact elastic and inelastic floor spectra of MIs evaluated over their common range of OOP vibration periods

Seismic Demand of Masonry Infills in R.C. Structures Accounting for the In-Plane/Out-of-Plane Interaction

The out-of-plane verification of unreinforced masonry infills (MIs) placed at different floor levels of a building is generally carried out through simplified methods, but seismic events in Italy (e.g. L'Aquila, 2009) and worldwide (e.g. Northridge, 1994) have highlighted that code provisions may result in wrong estimations of safety. The types of damage observed for MIs are usually a combination of, or an interaction between, in-plane (IP) and outof-plane (OOP) mechanisms. Specifically, the IP drift ratio is generally reduced at the upper storeys of buildings, where the OOP drift ratio increases due to an increase of seismic acceleration. Significant OOP damage may also take place at the lower storeys where the highest values of IP drift ratio are attained. The present work is aimed at identifying the effects of the IP and OOP nonlinear interaction of MIs on their seismic behaviour and acceleration demand. A five-element macro-model comprising four diagonal nonlinear beams and one (horizontal) central nonlinear truss for the prediction of the OOP and IP behaviour of MIs, respectively, is first implemented in a C++ computer code for the nonlinear dynamic analysis of r.c. infilled framed structures. The proposed algorithm addresses the issue of nonlinear interaction by modifying stiffness and strength values of the MI in the OOP direction on the basis of simultaneous or prior IP damage and vice versa. Moreover, a lumped plasticity model describes the inelastic behaviour of r.c. frame members, including a 26-flat surface modelling of the axial load-biaxial bending moment elastic domain at the end sections where inelastic deformations are expected. A spatial one-bay multi-storey shear-type model is considered as equivalent to infilled r.c. framed buildings. In particular, the dependence of the results on variation of the following design parameters is considered: i.e. number of storeys; bay length; aspect ratio of MIs, with two leaves of clay hollow bricks, defined as the ratio between the panel length and height; strength level of the r.c. framed structure. Biaxial spectrum-compatible accelerograms are considered at ultimate limit states. A review of the current Italian (NTC18), European (EC8) and American (FEMA356) code provisions is performed by means of comparison with analyses results

A Method for the Definition of Emergency Rescue Routes Based on the Out-of-Plane Seismic Collapse of Masonry Infills in Reinforced-Concrete-Framed Buildings

One of the main goals of disaster management planning is to ensure the effectiveness of the emergency measures when a hazard occurs. This happens only if the decision-makers use operational tools considering the structural characteristics of urban systems. Starting from these assumptions, the authors proposed an emergency management method based on the integrated work between two different scientific sectors, the urban planning and construction engineering sectors. The proposed method aims to evaluate the practicability of the strategic road network, as well as defining the emergency rescue routes based on the out-of-plane (OOP) seismic collapse of masonry infills (MIs) in reinforced concrete (RC)-framed buildings. The OOP failure of MIs is predicted according to an innovative MI macro-model. The authors test the method on a geographic area in the municipality of Gioia Tauro (Reggio Calabria, Italy). The results show that due to the collapse of MIs, the functionality of the strategic road network in emergency conditions can be compromised, causing losses of the urban systems’ performance. Based on the obtained results, the authors recommend that decision-makers use the proposed methodology to identify the vulnerable rescue paths and to locate the strategic infrastructure while spending the financial resources in a more effective way

A Method for the Definition of Emergency Rescue Routes Based on the Out-of-Plane Seismic Collapse of Masonry Infills in Reinforced-Concrete-Framed Buildings

One of the main goals of disaster management planning is to ensure the effectiveness of the emergency measures when a hazard occurs. This happens only if the decision-makers use operational tools considering the structural characteristics of urban systems. Starting from these assumptions, the authors proposed an emergency management method based on the integrated work between two different scientific sectors, the urban planning and construction engineering sectors. The proposed method aims to evaluate the practicability of the strategic road network, as well as defining the emergency rescue routes based on the out-of-plane (OOP) seismic collapse of masonry infills (MIs) in reinforced concrete (RC)-framed buildings. The OOP failure of MIs is predicted according to an innovative MI macro-model. The authors test the method on a geographic area in the municipality of Gioia Tauro (Reggio Calabria, Italy). The results show that due to the collapse of MIs, the functionality of the strategic road network in emergency conditions can be compromised, causing losses of the urban systems’ performance. Based on the obtained results, the authors recommend that decision-makers use the proposed methodology to identify the vulnerable rescue paths and to locate the strategic infrastructure while spending the financial resources in a more effective way