1,721,116 research outputs found
A Revolutionary Deep Generative Modelling for Linear and Nonlinear Analysis of Masonry
No full textThe primary challenge in designing and analysing masonry structures is predicting their mechanical response. In particular, fast and direct prediction of masonry mechanical response field is desirable. This motivates the present study to introduce an innovative model using a conditional generative adversarial neural network (cGAN) for this purpose within linear or nonlinear ranges. This model establishes a direct connection between masonry microstructural features and both local and global mechanical responses full-fields, overpassing the path dependency of nonlinear mechanical problems. The model predicts strain maps and reaction forces of masonry panels under different loading scenarios and at any level of loading, solely from masonry panels images that encode material properties and loading scenarios into different shades of colours, without the need for information about material constitutive laws. This revolutionary approach holds the potential to serve as metamodel alternative to computationally expensive finite element (FE) simulations for masonry structures.</p
Investigation of the Role of Clay Types and Porous Aggregate Effects on the Hygric Properties of Earth-Based Plasters
No full textThis study deals with the effects of expanded perlite and two type of clays (bentonite and kaolin) on the moisture transport properties of lightweight cement-clay plasters. The specific properties examined in this study are open porosity, open porosity, bulk density, saturation moisture content, capillary absorption coefficient and surface temperature during drying test. In these plaster mixers cement is replaced by a 50% (vol.) kaolin and bentonite content, as well sand is replaced by a 100% (vol.) expanded perlite content. The results indicate that the incorporation of both clay and perlite allows for the production of plasters with a bulk weight and porosity reduction of 100% and 400% respectively. This high void content contributes to high absorption, increasing the material’s water saturation content up to 4 times. The material porosity has influence on surface temperature that rapidly dropped due to evaporation, due to evaporative cooling effect at the first phase of drying, as well as second phase duration.</p
Experimental Evaluation of Salt Crystallization Induced Alterations in Granite Characteristics
No full textConcerning the preservation of built cultural heritage, historical masonry buildings have reached a critical level of deterioration because of their age, which consequently makes their resistance against salt decay problematic. The present study aims to describe the influence of salt crystallization on granite stone materials, a prevalent material in historic masonry in Northern Portugal. The paper aimed to understand the material’s susceptibility to sodium chloride (NaCl) induced damage. A series of nondestructive and destructive experiments (such as ultrasonic pulse velocity measurements and uniaxial compression strength tests) were conducted on granite stone to evaluate its properties in response to the salt crystallization phenomenon. The internal structure and integrity of granite samples were evaluated before and after exposure to salt crystallization cyclic tests. For the wetting/drying cycles, the environmental conditions (temperature and relative humidity) were chosen based on realistic settings, with an emphasis on avoiding the use of severe circumstances. The ultrasonic wave propagation measurements showed indirect indicators of microstructural alterations. The changes in compressive strength aligned with the findings from the other test programs. The combined results of the experimental campaign contribute to a better understanding of how salt crystallization might influence the physical and mechanical characteristics of granite masonry.</p
Experimental Assessment of the Hygric Properties of Granite in the Presence of Salt
No full textThe detrimental effects of salt in masonry structures manifest across two distinct levels: (i) impacting structural elements and (ii) influencing ornamental elements. The presence of salt in the material’s body (even a small amount) can significantly alter the hygric properties of the porous building materials. The presented paper focuses on the hygric properties of a commonly used granite masonry material from the Northern region of Portugal, particularly focusing on its response to the presence of sodium chloride (NaCl) salt. The evaluated properties include results from different experimental methods, including vacuum saturation tests, capillary absorption tests, and cup methods. Additionally, the ultrasonic pulse velocity (UPV) tests were also conducted on granite samples under different conditions (dry state, saturated with pure water, and saturated with a salt solution). Anisotropy in the vapor moisture movement within granite samples was evaluated along perpendicular and parallel directions concerning the rift plane. Results indicated that vapor moisture movement was more restricted through the direction perpendicular to the rift plane in comparison to the parallel direction. The formation of salt crystals within the pore network significantly influenced open porosity and vapor permeability, emphasizing the impact of salt attack on granite masonry. These findings contribute to a better understanding of the influences of salt on granite masonry structures.</p
Strain Rate-Dependent Structural Behaviour of Masonry Structures Loaded by the Impact Force of Waterborne Debris Evaluated According to ASCE/SEI 7–22 Design Prescriptions
No full textAs confirmed by recent post-disaster surveys, masonry buildings may experience substantial damage under waterborne debris impacts in extreme hydrodynamic event scenarios, e.g., floods or tsunamis. The common approach to model such load scenarios is to carry out structural analyses where the debris action is implemented through a representative force-time diagram. Recent studies demonstrated that the strain rate-dependent structural behaviour is activated in masonry structures when subjected to the impact force of waterborne debris, making the implementation of the strain rate-dependent materials necessary to carry out reliable structural simulations. However, these data have been collected using a specific model to compute the impact force-time diagrams developed from numerical and experimental data, which is different from the model prescribed by the US standard ASCE/SEI 7–22 to compute such loads. These two models lead to different force-time diagrams. Therefore, the design strategy imposed by the ASCE standard might affect the high strain rate effects with unknown implications. This study aims to investigate this research gap using nonlinear Finite Element (FE) simulations. A masonry wall is modelled with a micro-modelling approach. The water flow pressures and the debris impact force are applied. It is found that the F-t diagram given by the ASCE model causes significantly different strain rate-time histories in terms of increment rate and peak values across the structure.</p
Moisture and Temperature Effects on Masonry Structures:The Civic Tower of Pavia as a Case Study
No full textThis study focuses on the application of a hygro-thermo-mechanical (HTM) model to evaluate the structural behaviour of full-scale buildings, using a historical masonry structure as case study. In particular, the former Civic Tower of Pavia (Italy) was selected due to its simple morphology, unique historical significance, loading conditions, and the comprehensive set of structural information and material data available from previous studies. First, the proposed HTM model is introduced, including its components, namely the moisture transport model, heat transfer model, and mechanical model. Within this framework, the heat and moisture fields are fully coupled, whereas one-way coupling is employed between the hygrothermal and mechanical fields. Subsequently, the HTM model is applied to the Civic Tower of Pavia, with focus on the effects of moisture and temperature on the structural response. The results of the analysis are presented and dis-cussed in terms of developed stresses at the base of the building. Special attention is given to how moisture and temperature affect the mechanical behaviour of masonry, including potential for damage and failure under severe scenarios. This study offers a comprehensive overview of the HTM model and its practical application in a full-scale case study. The results highlight the critical importance of considering moisture and temperature effects in the design and maintenance of masonry structures, particularly in historical buildings. The paper concludes with recommendations for future research in this area, including the development of more advanced modelling techniques and the acquisition of additional data concerning the behaviour of masonry structures under varying environmental conditions.</p
Simplified two-step homogenization model for full scale FRCM reinforced masonry panels out-of-plane loaded
No full textThe paper deals with the analysis of two series of full scale masonry panels by means of a simplified homogenization approach formulated by the authors [1]. The experimental campaign, which is briefly discussed in the present paper, has been conducted by Nanni and co-workers at the University of Miami [3][4] testing twelve panels constructed adopting two different running bond masonry supports: clay bricks and concrete units. Homogenization is performed through a two-step procedure where the elementary cell is discretized by means of 24 CST elastic elements (bricks) and joints are reduced to interfaces with holonomic softening behavior. At a structural level, the masonry is modeled with rigid elements and homogenized flexural and torsional springs. In order to further validate the homogenization model proposed, a sophisticated tri-dimensional heterogeneous micro-modeling technique is also used. The Fabric Reinforced Cementitious Matrix (FRCM) composite material adopted to strengthen half of the tested walls has been modeled by means of truss elements whose mechanical properties have been calibrated to properly account for the behavior of the textile embedded into the cementitious binder. The accuracy of the proposed model, as well as the computational effort required to complete the analyses, have been evaluated with respect to the numerical and experimental outcomes
Long-Term Behaviour of GFRP-Reinforced Masonry Components Under Outdoor Environmental Conditions:Results After 5-Year Exposure
No full textFiber-reinforced polymers (FRP) have found extensive application in the strengthening and repair of masonry since the 1990s. Despite significant research into the short-term performance of FRP-strengthened masonry, there is still a limited understanding of their long-term behaviour and durability. Therefore, it is still necessary to gain a deeper insight into the mechanisms causing degradation and durability challenges, particularly in situations where these materials are exposed to more severe decay, such as externally bonded systems. Various accelerated ageing tests have been devised to replicate environmental conditions in a shorter time frame. These tests include immersion in water, freeze-thaw cycles, exposure to hygrothermal variations, salt crystallization, and UV radiation, among others. However, the use of accelerated ageing data for reliable estimations of service life requires a clear correlation with actual environmental processes. This study presents preliminary findings from a real exposure experimental campaign spanning 5 years. The complete experimental program (12 years) aims to analyse the natural ageing of masonry components reinforced with externally bonded glass fibres (GFRP). The ageing conditions encompass three scenarios: (a) direct outdoor exposure, involving outdoor hygrothermal variations, sunlight, and rainfall; (b) indirect outdoor exposure, with outdoor hygrothermal variations but sheltered from sunlight and rain; (c) control group maintained in laboratory conditions. The specimens comprise solid extruded fired-clay bricks reinforced with unidirectional GFRP sheets externally bonded through the wet lay-up procedure. Ageing effects on bond performance are evaluated by means of single-lap shear tests. Additionally, the study investigates the impact of surface treatment and the addition of an external render on bond durability.</p
Prediction of the Mix Proportions and Mechanical Performance of Foamed Concrete Blocks of the Masonry
No full textFoamed concrete is a type of lightweight concrete, more than 20% of its volume is air. It possesses high flowability, thermal and acoustic insulation, and low dead load (less aggregate). Due to the philosophy of foam concrete, designing and obtaining the desired densities require a lot of trial mixes and time. Therefore, the main objective of this research is to predict mix proportions and mechanical performance of foamed concrete. Materials used include cement, sand, water and foaming agent (NEOPOR Brand) of organic origin. Fifteen different densities (among 300–1000 kg/m3) were targeted. In the present research density, compressive strength, splitting tensile strength and ultrasonic pulse velocity tests were performed. The results demonstrated that there is a reliable positive relationship between density and strength of foamed concrete. The ultrasound pulse velocity (UPV) test is closely related to the density and mechanical performance of foamed concrete, and thus based on the UPV test, mathematical models were used to determine the mix proportions and strength. Models were validated using data of current and other research works. A high determination coefficient (R2 > 0.8) was achieved for all validations, supporting reliability and the use of these models in future research.</p
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