The solution of a backward-Kolmogorov equation is presented. This equation is associated with a Markov approximation of the response amplitude of a lightly damped linear oscillator driven by an evolutionary random excitation.
Research Interests: Mechanical Engineering, Civil Engineering, Aerospace Engineering, Mathematics, Random Vibration, and 15 moreApplied Mechanics, Density-functional theory, Mathematical Analysis, Oscillations, Dynamic Response, Separation of variables, Laguerre polynomial, Markov Process, Differential equation, Probability Density Function, Infinite series, Boundary Value Problem, Laguerre function, Laguerre Polynomials, and transition probability
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ABSTRACT
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The determination of the blast protection level of laminated glass windows and facades is of crucial importance, and it is normally done by using experimental investigations. In recent years numerical methods have become much more... more
The determination of the blast protection level of laminated glass windows and facades is of crucial importance, and it is normally done by using experimental investigations. In recent years numerical methods have become much more powerful also with respect to this kind of application. This report attempts to give a first idea of a possible standardisation concerning such numerical simulations. Attention is drawn to the representation of the blast loading and of the behaviour of the material of the mentioned products, to the geometrical meshing, as well as to the modelling of the connections of the glass components to the main structure. The need to validate the numerical models against reliable experimental data, some of which are indicated, is underlined.
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Aufgrund terroristischer Anschlaege sind Baustrukturen auch Explosionen ausgesetzt. In der vorliegenden Untersuchung werden numerische Simulationen verwendet, um die Auswirkungen von Detonationen in schienengebundenen... more
Aufgrund terroristischer Anschlaege sind Baustrukturen auch Explosionen ausgesetzt. In der vorliegenden Untersuchung werden numerische Simulationen verwendet, um die Auswirkungen von Detonationen in schienengebundenen Massenverkehrsmitteln zu untersuchen. Es werden verschiedene Parameter fuer die Detonation innerhalb eines Waggons variiert. An einem Zug ohne Unterteilung werden die Auswirkungen einer Explosion im Tunnel im Vergleich zum freien Feld gezeigt. Ein Risikomodell hilft, die Auswirkungen auf Passagiere zu erkennen. Anhand dieses Modells lassen sich die Einflussfaktoren auf das Risiko der Passagiere herausarbeiten. Es zeigt sich, dass insbesondere Einbauten wie Tueren oder Windfaenge helfen, die Detonationswelle zu reduzieren. (A) ABSTRACT IN ENGLISH: Recent terrorist attacks have shown that civil structures are also exposed to detonations. Numerical simulations are used here to investigate the influence of explosions in mass transport systems. Several attack scenarios are ...
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Numerical simulation tools have been developed suitable for the assessment of the physical vulnerabilities of rail transport infrastructures to explosion loads, mainly due to terrorist bomb attacks. The source term, the air medium and the... more
Numerical simulation tools have been developed suitable for the assessment of the physical vulnerabilities of rail transport infrastructures to explosion loads, mainly due to terrorist bomb attacks. The source term, the air medium and the structure are properly modeled using the computational framework of the explicit finite element code Europlexus. Several new features are added to the code. A case study of a rail station has been conducted, whose geometry has been reconstructed using a laser scanning technique. For several bombing scenarios the structural response is reliably determined, and through appropriate probit functions, the associated risk of human injuries has also been calculated.
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It is important to protect critical buildings (shopping centres, government buildings and embassies), infrastructure and utilities, train and underground stations against being damaged, destroyed or disrupted by deliberate acts of... more
It is important to protect critical buildings (shopping centres, government buildings and embassies), infrastructure and utilities, train and underground stations against being damaged, destroyed or disrupted by deliberate acts of terrorism, criminal activity and malicious behaviour. Normal regulations and building guidelines do not generally take into account these threats. The introduction of appropriate regulations or guidelines, where deemed necessary, should, enhance the resilience of buildings and infrastructure against explosion incidents. In order to protect the built infrastructure, methods are required to quantify the resistance of structural components against explosive loading and to assess the hazards resulting from the failure of an element. The applicable state-of-the-art techniques may include either experimental or numerical methods, or a combination of both. Therefore, the thematic group (TG) on the resistance of structures to explosion effects was formed in order ...
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It is important to protect critical buildings (shopping centres, government buildings and embassies), infrastructure and utilities, train and underground stations from being damaged, destroyed or disrupted by deliberate acts of terrorism,... more
It is important to protect critical buildings (shopping centres, government buildings and embassies), infrastructure and utilities, train and underground stations from being damaged, destroyed or disrupted by deliberate acts of terrorism, criminal activity and malicious behaviour. Normal regulations and building guidelines do not generally take into account these threats. The introduction of appropriate regulations or guidelines, where deemed necessary, should enhance the resilience of buildings and infrastructures against explosion incidents. In order to protect the built infrastructure, testing methods are required which can answer the question whether certain building elements can withstand certain loading conditions created by an explosive event. The applicable state-of-the-art techniques may include either experimental or numerical methods, or a combination of both. Therefore, the thematic group (TG) on the resistance of structures to explosion effects was formed in order to br...
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One of the component tests proposed by the European Enhanced Safety Vehicle Committee (EEVC) in 1998 is the headform against bonnet test. An analysis of the parameters of the test is presented with reference to the concepts of head... more
One of the component tests proposed by the European Enhanced Safety Vehicle Committee (EEVC) in 1998 is the headform against bonnet test. An analysis of the parameters of the test is presented with reference to the concepts of head performance criterion, wrap-around distance, head impact speed, and headform impactor mass. From the analysis it is concluded that the whole bonnet area can be tested with the child head-form, the headform impact velocity should be set equal to 35 km/h and that the mass of the headform can be equal to 3.5 kg. If the windscreen area is taken into account, the mass of the impactor should be 4.8 kg. For the covering abstract see ITRD E120563.
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This study presents a numerical approach for the calculation of fatality risk caused by the impact of flying debris on the human body. Following an explosion, the formation of a large number of high velocity flying fragments, especially... more
This study presents a numerical approach for the calculation of fatality risk caused by the impact of flying debris on the human body. Following an explosion, the formation of a large number of high velocity flying fragments, especially from glass panels, is very possible. The velocity, the mass and the shape of these projectiles define their hazardousness. The developed numerical approach is integrated into the fluid-structure techniques, commonly used for the determination of the behavior of a structure under blast loading. The implementation of the numerical approach in the EUROPLEXUS code is described thoroughly.
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Land mass transport systems have an open architecture and are vulnerable to terrorist attacks. In case of an explosion inside trains or stations, the risk of injuries and fatalities may be mitigated by properly strengthening and... more
Land mass transport systems have an open architecture and are vulnerable to terrorist attacks. In case of an explosion inside trains or stations, the risk of injuries and fatalities may be mitigated by properly strengthening and optimizing these structures. This risk depends on the peak overpressure and impulse, which are estimated here using numerical simulations, and is determined by special probit functions using the pressure–time curve calculated at each fluid point. The geometry of the structures investigated is obtained using a three-dimensional laser-scanning technology. Fluid–structure interaction (FSI) calculations have been performed, and for long, tube-like trains channelling effects have been considered. Several materials are used to describe the structural part of the models. A special FSI technique is presented, whereby a structure can be embedded in a fluid mesh without connection to the fluid nodes. This procedure avoids problems after the element erosion due to fail...
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In order to allow more reliable predictions on the lower head response under core melt-down conditions, the temperature distribution has been analysed including the natural convection in the corium pool. Furthermore, the mechanical models... more
In order to allow more reliable predictions on the lower head response under core melt-down conditions, the temperature distribution has been analysed including the natural convection in the corium pool. Furthermore, the mechanical models and the failure criteria have been improved based on the RUPTHER and FASTHER experiments where typical temperature gradients are simulated. Lower head local melting as well
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Considering the thermomechanical aspect of deformation leads also to the prospect of monitoring thermal emission as an indirect measure of dislocation activity. In this respect it may be considered to be analogous to acoustic emission and... more
Considering the thermomechanical aspect of deformation leads also to the prospect of monitoring thermal emission as an indirect measure of dislocation activity. In this respect it may be considered to be analogous to acoustic emission and so could be viewed as a possible tool for assessing the damage state of components. With this in mind, a damage assessment was carried out on three identically sized and shaped specimens cut from fractured alloy 800H pipe that had been held under a tensile creep stress of 42 MPa at 900°C, failing after 122 h
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The distribution of the crack size during the fatigue crack propagation phenomenon is investigated. A Markovian modeling of the crack is introduced through the fatigue crack growth law, and the associated Fokker‐Planck equation is written... more
The distribution of the crack size during the fatigue crack propagation phenomenon is investigated. A Markovian modeling of the crack is introduced through the fatigue crack growth law, and the associated Fokker‐Planck equation is written while special care is devoted to specifying its boundary conditions. This equation is solved by the method of separation of variables and the sought distribution function is obtained in the form of a convergent infinite series. An illustrative example, demonstrating the applicability of the approach, shows satisfactory agreement between theoretical results and experimental data.
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... Abstract. FISA-2003 : EU Research in Reactor Safety, Luxembourg, L, November 10-13, 2003. Preproc. S.335-40. Publication details. Download, http://opac.fzk.de:... more
... Abstract. FISA-2003 : EU Research in Reactor Safety, Luxembourg, L, November 10-13, 2003. Preproc. S.335-40. Publication details. Download, http://opac.fzk.de: 81/de/oai_frm.html?titlenr=57624&server=//127.0.0.1&port=81. ...
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Research Interests: Materials Science, Engineering Design, Structural Integrity, Strain Rate, Size Effect, and 11 moreInterdisciplinary Engineering, Internal Structure, Pressure Vessel, Elevated Temperature, Severe Accident, Austenite, Dynamic Strain Aging, Strain Rate Effect, Flow Stress, Ultimate Tensile Strength, and Mechanical strength
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Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use which might be made of this publication. Europe Direct is a service to help you find answers to your questions about the European... more
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It is important to protect critical buildings (shopping centres, government buildings and embassies), infrastructure and utilities, train and underground stations against being damaged, destroyed or disrupted by deliberate acts of... more
It is important to protect critical buildings (shopping centres, government buildings and embassies), infrastructure and utilities, train and underground stations against being damaged, destroyed or disrupted by deliberate acts of terrorism, criminal activity and malicious behaviour. Normal regulations and building guidelines do not generally take into account these threats. The introduction of regulations or guidelines should support the resilience of the buildings and infrastructure against explosive incidents. In order to protect the infrastructure, methods are required to quantify the resistance of structural elements against explosive loading and to assess the hazards resulting from failure of an element. The applicable state-of-the-art techniques may be either experimental or numerical methods, or a combination of both. Therefore, the thematic group (TG) on the resistance of structures to explosion effects was formed in order to bring the required expertise together, make it c...
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Finite element or finite volume simulations for the development of blast waves by using a model for the explosion of the solid itself need very fine meshes in the explosive and in the zone around the explosive. Structures may have a long... more
Finite element or finite volume simulations for the development of blast waves by using a model for the explosion of the solid itself need very fine meshes in the explosive and in the zone around the explosive. Structures may have a long distance to the source of the explosive. This leads often to very big meshes with many elements. The explosive is meshed often only coarse and therefore the results are not very accurate. There are several possibilities to deal with this problem. Large 3D calculations with a solid TNT model using a JWL-equation can be used but they are more effective when the results of one finer mesh could be mapped in a coarser mesh after some calculation steps. When the blast wave reaches a certain distance to the charge, the small elements inside the charge are not needed any more since the pressure ratio is decreased strongly. These small elements results in very small time steps for the full model. The report shows the implementation of the mapping algorithm i...
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While in service, pipelines may from time to time be exposed to impact loads from anchors or trawl gear. A lot of parameters influence the behaviour of the pipeline during impact, e.g. the diameter and thickness of the pipeline, the... more
While in service, pipelines may from time to time be exposed to impact loads from anchors or trawl gear. A lot of parameters influence the behaviour of the pipeline during impact, e.g. the diameter and thickness of the pipeline, the impactor’s mass and velocity, and of course the material used. Also potentially influencing the deformation pattern is the presence of surrounding water, which can be a difficult parameter to include experimentally. The pressurised contents of the pipeline can also be an influencing factor. To gain some insight into how the water and possible pressure inside the pipeline affect the global impact behaviour, numerical investigations have been carried out using FSItechniques available in the explicit finite element code Europlexus. One case was set up for validation against available experimental data, and additional cases examined numerically the effect of including pressure and/or surrounding water. The simulations generally captured the deformation and l...
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SHEET, Paper Number 1224 Size Effects in Deformation and Fracture of a Ferritic Reactor Pressure Vessel Steel T. Malmberg, K. Krompholz, D. Kalkhof, G. Solomos, E.C. Aifantis 5) (1) Forschungszentrum Karlsruhe GmbH, Institut für... more
SHEET, Paper Number 1224 Size Effects in Deformation and Fracture of a Ferritic Reactor Pressure Vessel Steel T. Malmberg, K. Krompholz, D. Kalkhof, G. Solomos, E.C. Aifantis 5) (1) Forschungszentrum Karlsruhe GmbH, Institut für Reaktorsicherheit, Postfach 3640, D-76021 Karlsruhe, Germany (2) Paul Scherrer Institut, Labor für Werkstoffverhalten, CH-5232 Villigen PSI, Switzerland (3) European Commission, Joint Research Centre, Institute for Systems, Informatics and Safety, I-21020 Ispra/VA, Italy (4) Aristotle University of Thessaloniki, Laboratory of Mechanics and Materials, GR-54006 Thessaloniki, Greece (5) Michigan Technological University, Center for Mechanics of Materials and Instabilities, Houghton, MI 49931, USA ABSTRACT In support of small scale tests of reactor structures and to extend basic knowledge, screening material tests of different, geometrically similar specimens have been performed to examine the influence of size on the mechanical response. Among other nuclear ste...
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Crashworthiness optimisation of vehicles requires the development of crash testing techniques based on wave propagation principles which allow precise measurement of dynamic loads and displacements, assessment of the mechanical response... more
Crashworthiness optimisation of vehicles requires the development of crash testing techniques based on wave propagation principles which allow precise measurement of dynamic loads and displacements, assessment of the mechanical response of structures subjected to an impact is however a difficult task. The two main parameters which make this task complex are the inertial and the stress wave propagation effects. An important issue for precision impact testing is to know accurately how the energy propagates through the structure in case of an impact. Such precision measurement technique should be applicable to any point of the vehicle structure in order to measure locally and in any direction the distribution of crash energy throughout the crash; this will allow the measurement of all the crash phenomena due to wave propagation and inertia forces at critical points of the structure. Results will allow a realistic validation of the simulation reliability of computer codes and achieve fu...
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At the present paper the response of structural steel components under explosive loading is numerically investigated. First the procedure for determining the pressure loads to be applied on a structure after an explosion is briefly... more
At the present paper the response of structural steel components under explosive loading is numerically investigated. First the procedure for determining the pressure loads to be applied on a structure after an explosion is briefly described. The importance of the material model and its capability of including the high strain-rate effects in the numerical analysis is studied by comparing simulations by the FEM code EUROPLEXUS with published data of real blast experiments. These comparisons are made with respect to the material models, utilizing the Cowper-Symonds law, the Johnson-Cook constitutive equation, a dynamic increase factor for the yield strength or only the static stress values. It is shown that the more comprehensive modelling can adequately reproduce the experimental data.
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This technical report describes a procedure that can be followed for the calculation of the loads to be applied to a structure as a consequence of a blast. The report considers explosions taking place outside a building, which are not... more
This technical report describes a procedure that can be followed for the calculation of the loads to be applied to a structure as a consequence of a blast. The report considers explosions taking place outside a building, which are not addressed directly at the relevant European Standards (Eurocode EN1991-1-7) dealing with accidental loading scenarios. The aim is the production of a simple, self-contained guide enabling the structural engineer to conduct a preliminary design of buildings for possible terrorist attacks. Aspects of the theory of blast waves have been included at an introductory level. The approach of the empirical methods for the prediction of blast loads has been chosen, which is more straightforward and has resulted from extensive experimental testing. For the determination of the main blast parameters, several graphs and diagrams have been included, which have been collected and properly adapted from several authoritative sources. This should make the load calculati...
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A technical literature survey has been conducted concerning the problems of building robustness and progressive collapse. These issues gained special interest in construction after the partial collapse of the Ronan Point apartment... more
A technical literature survey has been conducted concerning the problems of building robustness and progressive collapse. These issues gained special interest in construction after the partial collapse of the Ronan Point apartment building in London in 1968. Enhanced interest appeared again after the disproportionate collapse of the A.P. Murrah Federal Building in Oklahoma City in 1995, and the total collapse of the World Trade Center towers in 2001, both caused by terrorist attacks. This report, which is an updated version of the 2009 one, aims at summarising the state-of-the-art in the subject of progressive collapse risk of civil engineering structures. First, a list of main terms and definitions related to progressive collapse are presented. Then, a review of procedures and strategies for progressive collapse avoidance is provided, based on selected EU and US design codes, standards and guidelines. A review of research efforts and results in the field follows, as reported in int...
Nowadays there is a need to develop special techniques to protect the critical infrastructures from exposing events. The use of real explosive material on the experiments is very expensive and a lot of security measures should be taken.... more
Nowadays there is a need to develop special techniques to protect the critical infrastructures from exposing events. The use of real explosive material on the experiments is very expensive and a lot of security measures should be taken. Especially in the case that the test should be repeated many times in order to obtain accurate results is almost impossible to perform the real explosive experiments. That for came up the idea of a blast simulator that can reproduce an explosive charge in a most economic and controllable way. The setup of such an apparatus is a very difficult task where many details should be studied. The most appropriate way to study the several parameters that influence the performance of the blast actuator is to use numerical simulation techniques. This report performs numerous numerical investigations and gives answers to many questions concerning the performance of the impacting mass of the blast actuator on the specimen. The numerical results have been generate...
Abstract The work presents a numerical approach for the determination of the risk of injuries due to explosion events in large closed spaces, such as metro and railway stations, airport terminals, malls. The study is based on the... more
Abstract The work presents a numerical approach for the determination of the risk of injuries due to explosion events in large closed spaces, such as metro and railway stations, airport terminals, malls. The study is based on the numerical simulation of blast loading scenarios via fluid-structure interaction techniques. Such severe loading conditions induce large motion and significant deformation of the structure and this complicates the definition of a single discretization scheme for both the structural and the fluid domains. Therefore, a special methodology is used in order to de-couple the structure from the fluid at the topological level. The numerical results are generated with the fast transient dynamics explicit finite element code EUROPLEXUS. Investigations focus in particular on the glass parts of the structure due to their fragility and the consequent fragment generation. The numerical results are properly processed in order to calculate the fatal and non-fatal injuries risk. For the fatal injuries, special attention is also paid to the assessment of risk due to the impact of flying debris on the human body.
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A growing interest for the design of structures to sustain blast induced loads has been observed in recent years due to the worldwide rise of terrorist bombing attacks. The blast parameters that are essential for design can be located in... more
A growing interest for the design of structures to sustain blast induced loads has been observed in recent years due to the worldwide rise of terrorist bombing attacks. The blast parameters that are essential for design can be located in various publically available blast design manuals, where the proposed graphs and equations are based on a large experimental database established several decades ago. The degree of uncertainty in the determination of these parameters is significant, as a result of the unstable nature of explosives, the efficiency of the measuring equipment and the large pressure and impulse values involved in the blast phenomena. These uncertainties have been identified in the current study which focuses on the response of steel open sections under blast induced loads and addresses the influence of such uncertainties on the flexural response of axially loaded structural members. The variation of structural and load parameters was considered in the design procedure by utilizing a reliability-based assessment methodology. A probabilistic approach was followed and the reliability of the column was defined with respect to limit states proposed in various blast design manuals. Probability curves are constructed, by using single-degree-of-freedom models, showing the cumulative probability distribution of reaching a certain capacity with respect to a selected limit state. This way instead of a deterministic safe-unsafe criterion in design, the probability of damage is introduced in relation to the applied axial load, which provides a valuable insight to the behaviour of structural members subjected to an explosion.
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A growing interest for the design of structures to sustain blast-induced loads has been observed in recent years as a result of the worldwide rise of terrorist bombing attacks. The blast loading is usually characterized by a sudden... more
A growing interest for the design of structures to sustain blast-induced loads has been observed in recent years as a result of the worldwide rise of terrorist bombing attacks. The blast loading is usually characterized by a sudden increase in the pressure followed by an exponential decay. The parameters of this pressure pulse are essential for design and can be found in various blast design manuals available in the open literature. One of the most widely used sources is a technical report by Kingery–Bulmash, which provides values for many blast parameters in diagrams and polynomial form. However, it does not include an equation for calculating the blast wave decay coefficient, necessary for constructing the pressure–time history of an explosion at a certain point. In this study, a review of the technical literature that contains expressions for the blast pressure decay coefficient is performed, and relevant comparisons have been made. New equations describing the decay coefficient ...
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The determination of the blast protection level of civil engineering buildings components against explosive effects represents a design topic of crucial importance, in current practice. However, some key aspects of blast resistant... more
The determination of the blast protection level of civil engineering buildings components against explosive effects represents a design topic of crucial importance, in current practice. However, some key aspects of blast resistant structures design have been only marginally considered in the last decade, and currently still require appropriate regulations. This is especially true in the case of glass windows and facades, where the intrinsic material brittleness is the major influencing parameter for blast-resistant assemblies. While blast assessment of buildings and systems is usually achieved by means of experimental investigations, as well as Finite-Element numerical simulations, general regulations and guidelines are currently missing. In this regard, the European Reference Network for Critical Infrastructure Protection - Task Group (ERNCIP-TG) “Resistance of Structures to Explosion Effects” attempts to develop guidelines and recommendations aimed to harmonise test procedures in ...
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The determination of the blast protection level of laminated glass windows and facades is of crucial importance, and it is normally done by using experimental investigations. In recent years numerical methods have become much more... more
The determination of the blast protection level of laminated glass windows and facades is of crucial importance, and it is normally done by using experimental investigations. In recent years numerical methods have become much more powerful also with respect to this kind of application. This paper attempts to give a first idea of a possible standardization concerning such numerical simulations. Attention is drawn to the representation of the blast loading and to the proper description of the behaviour of the material of the mentioned products, to the geometrical meshing, and to the modelling of the connections of the glass components to the main structure. The need to validate the numerical models against reliable experimental data, some of which are indicated, is underlined.