Works at Czech Technical University in Prague as Professor and Head of the Department steel and timber structures. In his professional life he concentrates to the connection and fire design of steel structures. After Sept 11 studied experimentally the robustness of multi-storey building in Cardington on the experimental seven-storey building. Served as Chairman of the EU COST TU action Integrated fire engineering and response (IFER) which focussed to cooperation between the research community and fire brigades. In structural steel connection design prepared the component model for column bases and the component based finite element model of joints. Works in ECCS TC 10 Structural joints and in Project team for preparation of EN1993-1-8:2020.
This paper describes two different experiments on connections of trapezoidal sheets under elevate... more This paper describes two different experiments on connections of trapezoidal sheets under elevated temperatures. The first experiments were tensile tests carried out on four sets of tests with screwed connections under ambient and elevated temperatures. One diameter of self-drilling screws and three different thicknesses of trapezoidal sheets were used. The applied screws were without washers, or with sealed or steel washers. The second experiment was performed in a laboratory furnace to check the catenary action of a thin-walled trapezoidal sheet. The basic theory tested in this experiment was that in the first phase of the fire the sheet behaves as a simply supported beam, while in the second phase the load bearing is transferred by a tension membrane. These experiments will be used to develop a design model of connections at high temperatures. High fire resistance of the trapezoidal sheet, dependent on suitable design of the screwed connection to the bearing structure, was confir...
Current fire design models for time-temperature development within structural elements as well as... more Current fire design models for time-temperature development within structural elements as well as for structural behaviour are based on isolated member tests subjected to standard fire regimes, which serve as a reference heating, but do not model natural fire. Only tests on a real structure under a natural fire can evaluate future models of the temperature developments in a fire compartment, of the transfer of heat into the structure and of the overall structural behaviour under fire.To study overall structural behaviour, a research project was conducted on an eight storey steel frame building at the Cardington Building Research Establishment laboratory on January 16, 2003. A fire compartment 11×7 m was prepared on the fourth floor. A fire load of 40 kg/m2 was applied with 100 % permanent mechanical load and 65 % of imposed load. The paper summarises the experimental programme and shows the temperature development of the gas in the fire compartment and of the fire protected columns...
The lightweight sandwiches panels are produced by a modern and environmental controlled technolog... more The lightweight sandwiches panels are produced by a modern and environmental controlled technology. A typical sandwich panel consist of two covering steel sheets, generally made of the trapezoidal or light profiled steel sheets, and of a weak lightweight core. The increasing use of lightweight sandwiches panels in industrial and civil buildings requires the development of suitable methods for analysis. The response of single panel as well as behaviour of whole structure is influenced by joints between sandwiches panels and framework. The stiffening effect of the cladding panels on the structural behaviour of the structure, the stress skin procedure, with the respect to the connections was evaluated in [3] to observe the behaviour under the seismic loading. The published analysis [1] neglects stress distribution between the both metal faces. Only inner sheet is assumed to carry the applied loads and the bearing capacity of the connection, see [2].
... The beam to beam connections were created by fin plates, steel S275. ... Multi-linear isotrop... more ... The beam to beam connections were created by fin plates, steel S275. ... Multi-linear isotropic material with strain hardening was used for mild steel. Temperature dependent stress strainrelationship (σ− ε) of the steel is based on the Eurocode model EN 1993-1-2: 2004. ...
The Mokrsko fire test focused on the overall behaviour of the structure, which cannot be observed... more The Mokrsko fire test focused on the overall behaviour of the structure, which cannot be observed on the separate elements, and also on the temperature of connections with improved fire resistance. During the test, measurements were made of the temperature of the gas and of the elements, the overall and relative deformations, gas pressure, humidity, the radiation of the compartment to structural element and the external steel column, transport of the moisture through the walls, and also the climatic conditions. The results of the test show the differences between the behaviour of the element and the behaviour of the structure exposed to high temperatures during a fire. The collapse of the composite slab was reached. The results of the numerical simulations using the SAFIR program compared well with the measured temperature values in the structure and also in the connections.
The influence of the rotational characteristics of the column bases on the structural frame respo... more The influence of the rotational characteristics of the column bases on the structural frame response is discussed and specific design criteria for stiffness classification into semi-rigid and rigid joints are derived. The particular case of an industrial portal frame is then considered.
This paper describes the principles of Component Based Finite Element Modelling (CBFEM) and the s... more This paper describes the principles of Component Based Finite Element Modelling (CBFEM) and the system response quantity and application features for design of prequalified joints for seismic applications. The elements are analysed by geometrically and materially non-linear analysis with imperfections (GMNIA). The proper behaviour of components, e.g. of bolts, anchor bolts, welds etc., is treated by introducing components representing its behaviour in term of initial stiffness, ultimate resistance and deformation capacity. To show this process a contribution is prepared, which summarises the history of achievements of FEA application in structural connections. Contribution shows the currents trends in advanced modelling of connection components and differences of the research oriented and design-oriented models. Both have their roles in advanced analyses.
This paper describes two different experiments on connections of trapezoidal sheets under elevate... more This paper describes two different experiments on connections of trapezoidal sheets under elevated temperatures. The first experiments were tensile tests carried out on four sets of tests with screwed connections under ambient and elevated temperatures. One diameter of self-drilling screws and three different thicknesses of trapezoidal sheets were used. The applied screws were without washers, or with sealed or steel washers. The second experiment was performed in a laboratory furnace to check the catenary action of a thin-walled trapezoidal sheet. The basic theory tested in this experiment was that in the first phase of the fire the sheet behaves as a simply supported beam, while in the second phase the load bearing is transferred by a tension membrane. These experiments will be used to develop a design model of connections at high temperatures. High fire resistance of the trapezoidal sheet, dependent on suitable design of the screwed connection to the bearing structure, was confir...
Current fire design models for time-temperature development within structural elements as well as... more Current fire design models for time-temperature development within structural elements as well as for structural behaviour are based on isolated member tests subjected to standard fire regimes, which serve as a reference heating, but do not model natural fire. Only tests on a real structure under a natural fire can evaluate future models of the temperature developments in a fire compartment, of the transfer of heat into the structure and of the overall structural behaviour under fire.To study overall structural behaviour, a research project was conducted on an eight storey steel frame building at the Cardington Building Research Establishment laboratory on January 16, 2003. A fire compartment 11×7 m was prepared on the fourth floor. A fire load of 40 kg/m2 was applied with 100 % permanent mechanical load and 65 % of imposed load. The paper summarises the experimental programme and shows the temperature development of the gas in the fire compartment and of the fire protected columns...
The lightweight sandwiches panels are produced by a modern and environmental controlled technolog... more The lightweight sandwiches panels are produced by a modern and environmental controlled technology. A typical sandwich panel consist of two covering steel sheets, generally made of the trapezoidal or light profiled steel sheets, and of a weak lightweight core. The increasing use of lightweight sandwiches panels in industrial and civil buildings requires the development of suitable methods for analysis. The response of single panel as well as behaviour of whole structure is influenced by joints between sandwiches panels and framework. The stiffening effect of the cladding panels on the structural behaviour of the structure, the stress skin procedure, with the respect to the connections was evaluated in [3] to observe the behaviour under the seismic loading. The published analysis [1] neglects stress distribution between the both metal faces. Only inner sheet is assumed to carry the applied loads and the bearing capacity of the connection, see [2].
... The beam to beam connections were created by fin plates, steel S275. ... Multi-linear isotrop... more ... The beam to beam connections were created by fin plates, steel S275. ... Multi-linear isotropic material with strain hardening was used for mild steel. Temperature dependent stress strainrelationship (σ− ε) of the steel is based on the Eurocode model EN 1993-1-2: 2004. ...
The Mokrsko fire test focused on the overall behaviour of the structure, which cannot be observed... more The Mokrsko fire test focused on the overall behaviour of the structure, which cannot be observed on the separate elements, and also on the temperature of connections with improved fire resistance. During the test, measurements were made of the temperature of the gas and of the elements, the overall and relative deformations, gas pressure, humidity, the radiation of the compartment to structural element and the external steel column, transport of the moisture through the walls, and also the climatic conditions. The results of the test show the differences between the behaviour of the element and the behaviour of the structure exposed to high temperatures during a fire. The collapse of the composite slab was reached. The results of the numerical simulations using the SAFIR program compared well with the measured temperature values in the structure and also in the connections.
The influence of the rotational characteristics of the column bases on the structural frame respo... more The influence of the rotational characteristics of the column bases on the structural frame response is discussed and specific design criteria for stiffness classification into semi-rigid and rigid joints are derived. The particular case of an industrial portal frame is then considered.
This paper describes the principles of Component Based Finite Element Modelling (CBFEM) and the s... more This paper describes the principles of Component Based Finite Element Modelling (CBFEM) and the system response quantity and application features for design of prequalified joints for seismic applications. The elements are analysed by geometrically and materially non-linear analysis with imperfections (GMNIA). The proper behaviour of components, e.g. of bolts, anchor bolts, welds etc., is treated by introducing components representing its behaviour in term of initial stiffness, ultimate resistance and deformation capacity. To show this process a contribution is prepared, which summarises the history of achievements of FEA application in structural connections. Contribution shows the currents trends in advanced modelling of connection components and differences of the research oriented and design-oriented models. Both have their roles in advanced analyses.
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Papers by F. Wald