1,721,015 research outputs found
Feasibility and usefulness of simplified analytical approach to fire design of masonry structures
No full textThe proposed study applies simple expressions of collapse load in exposure conditions, depending on the effective thickness and load eccentricity, to past case studies available in literature. The reduced section corresponding to equivalent ‘cold’ structural collapse under the given applied load is evaluated on the grounds of available experimental information. The results provided by different analytical approaches are assessed with respect to different failure modes under high temperature exposure
Modeling of mechanical damage in traditional brickwork walls after fire exposure
No full textThe paper addresses the issues of fire behavior of masonry walls made of traditional/historical component materials (bricks and mortar).There are reasons for coupling investigations on the residual mechanical properties to fire resistance data, aiming at a more complete knowledge of the behavior of a masonry member during and after fire exposure. The paper proposes a numerical approach via FEM to the problem of residual mechanical performance of load-bearing fire-separating masonry walls after insulation failure. The goal is to establish relationships between fire resistance ratings under exposure and decay in mechanical properties after exposure; the parameter of wall thickness is especially investigated. This is performed by means of FEM analysis, simulating a standard ISO 834 fire resistance test followed by a mechanical compressive failure test on each investigated type of wall. First, a preliminary transient heat flow analysis gives a numerical prediction of fire resistance after violation of I (Insulation) criterion; then, a staggered heat flow - stress analysis repeats the heating of the wall up to insulation failure and calculates the thermal strain accounting for cracking; finally, a ‘cold’ structural analysis in compression is performed on the thermally-deformed model after cooling. The comparison of numerical outcomes to available experimental information allows to judge the reliability of the numerical approach in reproducing the residual behavior of a masonry wall after fire exposure
First evaluation of the structural performance of traditional brickwork after standard fire exposure
No full textThe paper addresses the issues of fire behavior of masonry walls made of traditional/historical component materials (bricks and mortar). There are reasons for coupling investigations on the residual mechanical properties to fire resistance data, aiming at a more complete knowledge of the behavior of a masonry member during and after fire exposure. The paper is part of a research that aims at investigating the relationship between fire and post-fire (i.e. residual) mechanical behavior of masonry walls, paying attention to scale-related problems and to the possible exploitation of numerical tools to establish simplified approaches. The goal is to establish relationships between fire resistance ratings under exposure and decay in mechanical properties after exposure; the parameter of wall thickness is especially investigated, by choosing four different values (i.e. 12, 25, 38 and 51 cm). This is performed by means of FEM analysis with DIANA 9.4.4 software, simulating a standard ISO 834 fire resistance test followed by a mechanical compressive failure test on each investigated type of wall. The approach, successfully tested against experimental data already available, features a preliminary transient heat flow analysis which gives a numerical prediction of fire resistance after violation of I (Insulation) criterion; then, a staggered heat flow - stress analysis repeats the heating of the wall up to insulation failure and calculates the thermal strain accounting for cracking; finally, a ‘cold’ structural analysis in compression is performed on the thermally-deformed model after cooling. The paper also addresses a way for the extended application of the research outcomes, relying on a simple approach based on the concept of equivalent fire severity
Seismic Retrofitting of Traditional Masonry with Pultruded FRP Profiles
No full textThis paper presents a study on the potentiality of seismic retrofitting solutions with pultruded Fiber Reinforced Polymer (FRP) profiles. This material can be used in connected frames
providing lightweight, corrosion-free and reversible retrofitting of masonry buildings with the moderate requirements of surface preservation. In a hypothetical case study, an experimental program was designed; monotonic shear tests on a half-size physical model of the sample wall were performed to assess the structural performance before and after retrofitting with a basic frame of pultruded Glass Fiber Reinforced Polymer (GFRP) C-shaped profiles, connected to the masonry by steel threaded bar connections. During the tests, the drift, the diagonal displacements in the masonry and the micro-strain in the profiles were measured. The retrofitted system has proven very eective in delaying crack appearance, increasing the maximum load (+85% to +93%) and ultimate displacement (up to +303%). The failure mode switches from rocking to a combination of diagonal cracking and bed joint sliding. The gauge recordings show a very limited mechanical exploitation of the GFRP material, despite the noticeable eectiveness of the retrofit. The application seems thus promising and worth a deeper research focus. Finally, a finite element modelling approach has been developed and validated, and it will be useful to envisage the eects of the proposed solution in future research
High temperature effects on masonry materials
No full textResearch on masonry structures is very complex and manifold. A quite novel branchof research for masonry materials is here addressed, i.e. the residual behavior of brick,cement mortar and masonry after exposure to high temperatures. Masonry buildings -especially old and historic ones - are often very vulnerable to the attack of fire, and theneed for fire protection may be in conflict with preservation of architectural heritage.The whole matter of high temperature exposure is rich in physical, mechanical andchemical issues, which are mutually connected. Moreover, masonry material is compositeand involves a variety of combinations of materials, geometry and textures which areidentifiable in masonry buildings through different ages and countries; this leads topossible expensiveness in testing and difficulties in theoretical and experimentalmodeling. The point of view of the mechanical characterization of materials after hightemperature exposure is here taken into consideration; about this peculiar subject, veryfew theoretical as well as experimental studies are currently available.First, the state-of-the-art of such research is briefly outlined. Real events as well asstandard fire tests often demonstrate that masonry walls and structures can excellentlywithstand the high temperatures that can be reached during a fire event; on the otherhand, the residual mechanical performance of a structure after exposure may need to beevaluated, if high levels of fire safety are required.Then, the results of recent investigations are here reported, which have given a firstcontribution to the experimental knowledge of the residual behavior of masonry andseparate components (solid clay bricks and cement mortar) after high temperatureexposure. The theoretical elaborations of such outcomes have been useful to set a firstbasis for the establishment and calibration of analytical tools for the prediction of theresidual mechanical performance of masonry, brick and mortar. © 2012 Nova Science Publishers, Inc. All rights reserved
Residual mechanical parameters of masonry exposed to fire: a new numerical approach
No full textThe paper is part of a research that aims at investigating the relationship between fire and post-fire (i.e. residual) mechanical behaviour of masonry walls, paying attention to the possible exploitation of numerical tools for simplified approaches. The goal is to establish relationships between exposure severity under ISO834 conditions and decay in mechanical properties after exposure; the parameter of wall thickness is especially investigated, by choosing four different values (i.e. 12, 25, 38 and 51 cm). This is performed by means of FEM analysis with DIANA 9.4.4 software, simulating a standard ISO 834 fire resistance test followed by a mechanical compressive failure test on each investigated type of wall. The FE analyses’ outcomes allow to draw exponential expressions of the decay in compressive strength as a function of the exposure severity
Masonry exposed to high temperatures: Mechanical behaviour and properties — An overview
No full textThe paper summarises the available information about the behaviour of masonry assemblies and components exposed to high temperatures and fire. A general frame is provided by fire resistance issues in current code provisions and observations from real events, theoretical as well as experimental researches on materials’ performance during and after exposure to high temperatures. In particular, the newly acquired engineering approach to fire design has raised the need for improvements in the knowledge of fire and post-fire behavior of structures at a material scale; thus, the paper particularly focuses on the mechanical properties of masonry materials, that are still scarcely investigated, especially in the residual (i.e. post-fire) situation. Detailed comments are given about the temperature-dependence of the relevant mechanical properties for masonry and its components, that are put into comparison. Then, the main research needs are outlined in the conclusions
Numerical investigation on the residual behaviour of masonry walls damaged by fire exposure
No full textThe paper proposes a numerical approach to the problem of residual mechanical performance of load-bearing fire-separating masonry walls, via FE modelling. The mechanical features of the model are oriented to capture the cracking behaviour under both thermal and mechanical stress; by doing so, the liability of numerical outcomes could be assessed by comparison to experimental information already obtained. The numerical analysis is performed by means of FEM analysis with DIANA 9.4.4 software, simulating the experimental heating cycle followed by a mechanical ‘cold’ compressive failure test. The comparison of numerical outcomes to available experimental information allows to judge the good reliability of the numerical approach in reproducing the residual behaviour of a masonry wall after fire exposure; this would especially address the issues of physical modelling and the difficulties of relating the behaviour of small samples to real-size walls
FE modelling and experimental investigation on adhesive joints between clay brick and pultruded frp profiles
No full text- …
