| 1. |
- Honfi, Daniel
(författare)
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Design for Serviceability - A probabilistic approach
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In many design situations the acceptable performance of structures is defined by serviceability requirements. To estimate the probability of serviceability failure three main design aspects should be considered: (1) the relevant exposures, (2) the structural response and (3) the performance criteria. This thesis presents background information and new findings on structural serviceability related to all three aforementioned aspects. To study current practice concerning serviceability design two surveys with experts are presented: (1) serviceability issues in present Swedish design practice and (2) research interviews with international experts working with glass structures. The main conclusion of the two surveys is the general need for better understanding and guidance about serviceability, both in education and design codes. Since load history and long-term deformations may have a large influence on serviceability, an advanced finite element model has been developed to estimate the deflections of structural sized timber beams in natural environment. The model is capable to take into account the combined effect of the variations of relative humidity in the surrounding environment and the time-variant mechanical loading. Based on the results of the model, possibilities of simplified modelling are investigated to predict long-term deflections of timber structures. The reliability of serviceability limit states in current design codes is investigated mainly focusing on static deflections. Simple models are used to compare various construction materials – steel, concrete and timer – in terms of serviceability reliability, based on design according to Eurocode prescriptions using second order reliability methods. It is shown that the reliability of Eurocodes is not consistent. The inconsistency exists among different materials, variable to total load ratios and loaded areas. The proposed method may provide a basis for code calibration with regard to serviceability. As a final step the time-dependent reliability for serviceability design for beams is estimated using Monte Carlo simulation. The study presented in the time-variant analysis is restricted to timber floor beams in offices and residential buildings. However, the presented method provides a framework to calibrate proper deflection limits, load factors and creep coefficients based on a probabilistic investigation involving uncertainties in all important aspects of structural serviceability.
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| 2. |
- Honfi, Daniel, et al.
(författare)
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Glass structures – learning from experts
- 2013
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Ingår i: COST Action TU0905, Mid-term Conference on Structural Glass. - : CRC Press. - 9781138000445 ; , s. 527-535
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Konferensbidrag (refereegranskat)abstract
- Despite the increasing research activity on structural use of glass in the past years, there is still a lack of comprehensive design codes and standards linked to real-life applications on a structural level. However, more and more ambitious buildings and structures are built every year. Thus the knowledge is out there. The aim of the presented project is to collect data on the existing design philosophy and glass failure cases. The investigation includes a survey about how practicing structural engineers deal with different design aspects of glass with a special focus on robustness and serviceability. The current document gives a brief overview about the findings of the interviews
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| 3. |
- Honfi, Daniel, et al.
(författare)
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Modelling of bending creep of low- and high-temperature-dried spruce timber
- 2013
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Ingår i: Wood Science and Technology. - : Springer Science and Business Media LLC. - 1432-5225 .- 0043-7719.
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Tidskriftsartikel (refereegranskat)abstract
- In the current project, a finite element model is developed to analyse the long-term behaviour of timber beams. The time-dependent response of wood subjected to bending and moisture changes is investigated in terms of strains and stresses. A rheological model is implemented to capture the effects of creep, mechano-sorption and hygroexpansion. The model is validated against test results from Bengtsson and Kliger (Holzforschung 57:95–100, 2003). The results of the analysis showed that the mechano-sorptive creep of low- (LT) and high-temperature-dried (HT) timber beams can be sufficiently modelled with a spring and a single Kelvin body. The different mechano-sorptive behaviour of LT- and HT-dried specimens is considered with different mechano-sorptive and shrinkage–swelling parameters. The presented model could be used to derive general mechano-sorptive parameters: (1) for better prediction of creep over the service life and (2) to provide a basis of time-dependent probabilistic calculations for structural-sized timber in serviceability limit state.
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| 4. |
- Honfi, Daniel, et al.
(författare)
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Reliability of beams according to Eurocodes in serviceability limit state
- 2012
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 35, s. 48-54
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Tidskriftsartikel (refereegranskat)abstract
- To achieve a relatively consistent probability of failure for structural elements, most design codes apply reliability based code calibration process. Such approaches commonly focus on the strength of the structural members, which is related to the ultimate limit state (ULS). However in the design of beams the performance of the structural elements is often limited by the serviceability requirements, which are related to the serviceability limit state (SLS) using different load combinations than applied in the ultimate limit state. The current study aims to investigate the reliability for serviceability design for flexural members made of different materials (steel, concrete and timber) according to the specifications of the Eurocodes. Second-order reliability method (SORM) is applied to determine the reliability index for different design situations for beams subjected to bending. The probabilistic models of basic variables for time invariant analysis have been taken from the JCSS Probabilistic Model Code. The characteristic, the frequent and the quasi-permanent combination of actions are investigated and compared. The differences in service reliability for different materials are discussed. The results show that there are differences between the achieved reliability indices in the serviceability state between different materials and that for the given load combinations in the Eurocode the reliability index is often below the one given in the code. (C) 2011 Elsevier Ltd. All rights reserved.
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| 5. |
- Honfi, Daniel
(författare)
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Serviceability floor loads
- 2014
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Ingår i: Structural Safety. - : Elsevier BV. - 0167-4730. ; 50, s. 27-38
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Tidskriftsartikel (refereegranskat)abstract
- Serviceability of structures has to be verified for a lower load level than the design load used for safety considerations. Representative values of actions used in serviceability load combinations are often defined in a way that the fraction of time spent above a given load level should be limited to a certain value. To determine these load levels more information on the stochastic nature of the loading process is needed than to estimate the design load. A convenient way in structural design codes is to express representative values (rare, frequent and quasi-permanent) as a fraction of the characteristic value by using load reduction factors. However, the characteristic value is usually defined in a different way i.e. with a certain probability of not being exceeded (in a chosen period of time). The current paper estimates representative values of floor live loads by numerical simulation using stochastic live load models with a special focus on serviceability. The results are compared to values given in existing standards (Eurocode on first place). Improvements are suggested concerning the load reduction factors, the definitions of the representative values and the stochastic load parameters. (C) 2014 Elsevier Ltd. All rights reserved.
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| 6. |
- Honfi, Daniel, et al.
(författare)
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Structural reliability according to Eurocodes in serviceability limit state
- 2011
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Ingår i: IABSE-IASS 2011 London Symposium Report. - 9780707971223
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Konferensbidrag (refereegranskat)abstract
- The current study aims to investigate the reliability for serviceability design for flexural members made of different materials (steel, concrete and timber) according to the specifications of the current versions of Eurocodes. Second-order reliability method is applied to determine the reliability index for different design situations for simply supported beams subjected to bending. The characteristic, the frequent and the quasi-permanent combination of actions has been investigated and compared. The differences in service reliability for different materials have been discussed.
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| 7. |
- Thelandersson, Sven, et al.
(författare)
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Structural design and detailing for robustness
- 2011
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Ingår i: IABSE-IASS 2011 London Symposium Report. - 9780707971223
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Konferensbidrag (refereegranskat)abstract
- Assessment of robustness of structural systems very often involves assessment of the structural response after local damage. In this paper an attempt is made to describe the state of art in this field with focus on methods which can be used in engineering practice. Advanced non-linear and dynamic computer tools are available today which can deal with most of the above mentioned phenomena but they are often too complex to be used directly in engineering design. Furthermore, the necessary input data concerning non-linear, large deformation behaviour of materials, joints and elements is either lacking or associated with great uncertainty. The commonly applied strategy to prescribe tying requirements will be discussed from the point of view of its effectiveness in different structural systems.
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