Wouter Botte | Ghent University (original) (raw)
Papers by Wouter Botte
Structure and Infrastructure Engineering, 2021
Reinforced concrete structures are often subjected to corrosion, inducing a decreasing reliabilit... more Reinforced concrete structures are often subjected to corrosion, inducing a decreasing reliability over time. This corrosion often exhibits spatial variation, which can be modelled by random fields...
Lecture Notes in Civil Engineering, 2021
This publication is part of the proceedings of the <i>Biot-Bažant</i> <i>Confer... more This publication is part of the proceedings of the <i>Biot-Bažant</i> <i>Conference on Engineering Mechanics and Physics of Porous</i> <i>Materials</i>, which took place virtually on June 1-3, 2021. It contains a one-page abstract and the video of the talk that was given at the conference.
Applied Sciences, 2021
The alternative load path method is widely used to assess the progressive collapse performance of... more The alternative load path method is widely used to assess the progressive collapse performance of reinforced concrete structures. As an alternative to an accurate non–linear dynamic analysis, an energy–based method (EBM) can also be adopted to approximately calculate the dynamic load–bearing capacity curve or the dynamic resistance based on a static capacity curve. However, dynamic effects cannot be explicitly taken into account in the EBM. The model uncertainty associated with the use of the EBM for evaluating the dynamic ultimate capacity of structural frames has not yet been quantified. Knowledge of this model uncertainty is however necessary when applying EBM as part of reliability calculations, for example, in relation to structural robustness quantification. Hence, this article focuses on the evaluation of the performance of the EBM and the quantification of its model uncertainty in the context of reliability–based assessments of progressive or disproportionate collapse. The i...
Quality inspection of strength properties has to ensure that the used materials comply with their... more Quality inspection of strength properties has to ensure that the used materials comply with their specified requirements. Based on the average outgoing quality limit concept, conformity criteria can be designed and evaluated in an objective way. In this contribution, the conformity criteria for the yield strength of steel reinforcement bars given in the European Standard EN 10080 and the German Standard DIN 488-6 are evaluated based on this concept. It was shown that the current conformity parameters suggested in these standards yield OC-lines that cross the limiting boundary. Hence, subsequently, alternative values for the conformity control parameters are proposed. Finally, it was shown that conformity control of reinforcing steel has a beneficial influence on the reliability level of a reinforced concrete beam.
IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019
Recently, several structural failures demonstrated the disastrous consequences of progressive col... more Recently, several structural failures demonstrated the disastrous consequences of progressive collapse and raised the awareness of the engineering community. However the low probability of progressive collapse makes it uneconomical to design every building against progressive collapse using conventional design methods. Furthermore in most cases the initiating events of progressive collapses are unknown during the design. As such, consideration of secondary load-carrying mechanisms can be an effective alternative. These mechanisms include compressive arch action (CAA) and tensile catenary action (TCA) in reinforced concrete (RC) beams. Several researchers have investigated the effects of CAA and TCA experimentally and numerically in individual RC beams. However to date limited studies have been carried out to study these mechanisms in RC beam-grids. Hence in this contribution a validated numerical model is developed to study and quantify the individual contributions and development o...
The Eurocodes currently do not provide a coherent reliability-based justification for the semi-pr... more The Eurocodes currently do not provide a coherent reliability-based justification for the semi-probabilistic design format of temporary structures. Besides the need for suitable target reliability levels, a coherent definition of partial factors is needed, adjusted according to the chosen target reliability level and the intended reference period considered for the design of the temporary structure. When developing such a partial factor approach, attention should be given to the coherency with current Eurocodes to avoid conceptual discrepancies between the design of long-term and temporary structures. In this contribution a full-probabilistic framework for the structural reliability quantification of temporary structures is developed, based on Latin hypercube sampling. A sensitivity study is performed to detect the most important variables to be considered for the reliability analysis. The framework is subsequently used to determine the inherent reliability levels of scaffolds assoc...
Existing concrete bridges can show signs of deterioration, e.g. due to corrosion, in which case t... more Existing concrete bridges can show signs of deterioration, e.g. due to corrosion, in which case the question arises whether these bridges still have an acceptable safety level. To obtain additional information about the state of the structure, different types of information can be gathered. However, the measurements performed are often not used directly to update the estimate of the corrosion degree of the bridge and the resulting information from different measurement types is not combined. In this contribution, it is investigated how parameters of the service life models for concrete girders subjected to chloride-induced corrosion can be updated based on heterogeneous measurement data, with the focus on modal measurements and strain measurements. The posterior distributions of these parameters are generated based on Bayesian updating. These updated distributions can be used to get a more accurate estimate of the real deterioration state of the bridge. Based on this, the failure pr...
Engineering Structures, 2020
Membrane structures are widely used because of their lightweight properties and expressive archit... more Membrane structures are widely used because of their lightweight properties and expressive architectural shapes. However, there does not yet exist a unified design approach for membrane structures as is available for conventional buildings. Because of their flexibility, membrane structures exhibit a different structural behaviour than conventional buildings. Membrane structures are doubly curved, prestressed and the prestress contributes to the stiffness. The structural response of these structures is non-linear, and the hanging and arching directions interact. A probabilistic framework for tensioned membrane structures is developed herein. Using this tool, partial factors are calibrated for a representative tensioned hypar membrane structure made of PVC-coated polyester fabric. Reliability analyses are performed using a First Order Reliability Method in combination with Latin Hypercube Sampling. The approach is illustrated for two load cases, i.e. considering snow load and wind upl...
Reinforced concrete structures degrade over time, among others due to corrosion. This degradation... more Reinforced concrete structures degrade over time, among others due to corrosion. This degradation process is not uniform along the structure. Monitoring and inspections can be used to detect damage and update a deterioration model of the structure. In this work, a model-based method is used to identify damage through the calibration of a FEM model based on modal characteristics. The model calibration is performed by means of a Bayesian method, using MCMC to sample the posterior distributions of model parameters for the time-dependent degradation of material properties. The calibrated model can then be used for a more accurate prediction of the remaining service life. Furthermore, it enables to be implemented in a pre-posterior analysis framework to determine theVoI of the monitoring and inspection program for comparison of different monitoring and inspection strategies.
Based on experimental research on a real-scale one-way reinforced concrete slab with two spans fo... more Based on experimental research on a real-scale one-way reinforced concrete slab with two spans for which the internal support was removed, a numerical model in ABAQUS was developed and validated. The model is subsequently used to investigate the uncertainty of the load bearing capacity of the damaged slab considering four key random variables. Further, the probability density evolution method (PDEM) is applied for the reliability assessment. Although PDEM has in general been applied to solve dynamic reliability problems, in this contribution this method was adapted and applied to a static problem. The PDF of the load bearing capacity is calculated considering the ultimate load bearing capacity of the slab in its damaged state, i.e. the load corresponding with the rupture of the reinforcement bars at the inner support due to the developed tensile membrane action (TMA). Taking into account the obtained PDF for the capacity of the damaged system, the reliability index of the damaged sl...
IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019
The framework of pre-posterior decision analysis has a large potential as a decision support tool... more The framework of pre-posterior decision analysis has a large potential as a decision support tool in structural engineering. It seems ideally suited to tackle problems related to determining the value of Structural Health Monitoring and is commonly applied in inspection and maintenance planning. However, the application of this methodology for integrated life-cycle cost decision making related to monitoring of time-dependent and spatial degradation phenomena in concrete structures, needs further investigation. In this work, the time- dependent and spatial degradation phenomena will be coupled to the pre-posterior decision making approach and applied on concrete beams under bending, subjected to corrosion of the reinforcement. A framework is set up to determine the value of information of inspections enabling adequate decision-making. The methodology incorporates Bayesian updating based on the uncertain inspection outcomes. The framework will be illustrated by application on a simply...
When a continuous reinforced concrete slab is excessively loaded or a certain support is lost due... more When a continuous reinforced concrete slab is excessively loaded or a certain support is lost due to an accidental event, membrane action can be activated in order to generate an additional load transfer to neighbouring supports, which can considerably enchance the load-carrying capacity. This can delay or even prevent a progressive collapse and increase the robustness of concrete structures. In this contribution, the sensitivity of the collapse load of a one-way RC slab to variations of the different design variables is assessed, both for an undamaged situation and a damaged situation considering the removal of an intermediate support. Consequently, a probabilistic model for the load-bearing capacity is established and finally the quantification of the structural robustness is discussed using deterministic and reliability-based robustness indices.
IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management, 2019
Despite the recent amount of theoretical and technological developments, structural robustness is... more Despite the recent amount of theoretical and technological developments, structural robustness is still an issue of controversy being underlined by several structural failures in the past. Current design codes point out different strategies, among which strategies to limit damages due to the collapse of a load-bearing member by applying prescriptive design and detailing rules. For example for consequence class 2 structures EN1991-1-7 defines a risk class CC2b for which also vertical ties are required. However, the background of the design values of vertical ties in current codes is not clear and their adequacy should be validated. Moreover effects such as membrane action and Vierendeel action are important to consider when assessing structural robustness and are difficult to incorporate when applying only traditional design methodologies. To this extent a set of numerical simulations have been executed in this contribution in order to verify the progressive collapse behaviour of RC ...
Before implementing a bridge monitoring strategy, a bridge manager would like to know the return ... more Before implementing a bridge monitoring strategy, a bridge manager would like to know the return on investment. Moreover, in order to spend the available budget as efficiently as possible, the monitoring strategy should be optimized, i.e., the type of measurements but also the time and locations at which these are performed. For this purpose, the Value of Information (VoI) can be used. The VoI represents an estimate of the benefit that can be gained from a monitoring strategy before it is actually implemented. By comparing the VoI of different alternative strategies, the one with the highest VoI can be selected. As such, the VoI is a tool for objective decision-making. The calculation of the VoI is based on pre-posterior analyses, including Bayesian updating of model parameters based on yet unknown monitoring outcomes. When calculating the VoI for an actual case, some challenges arise. First, the calculation of the VoI requires a number of assumptions on different input parameters. ...
Progressive collapse resistance of a building structure is often investigated by the notional rem... more Progressive collapse resistance of a building structure is often investigated by the notional removal of one or more vertical load bearing elements from the structural system. Usually, a nonlinear dynamic analysis is needed to perform such an analysis. To avoid the complex nonlinear dynamic analysis, the energy-based method (EBM) is a promising method to predict the maximum dynamic responses of a structural system, where the dynamic load-bearing capacity curve is derived from the static load-displacement curve based on the principle of energy conservation. In this contribution, the performance of the EBM is evaluated based on a validated finite element model of a tested RC slab. Subsequently, 60 samples are generated by using Latin Hypercube Sampling (LHS), taking into account probability distributions for the most important variables. Both static analyses and direct dynamic analyses are executed for every sample set. Based on the results of the stochastic analyses, the EBM is obser...
In order to assess the structural reliability and redundancy with respect to deterioration, it is... more In order to assess the structural reliability and redundancy with respect to deterioration, it is required to select appropriate models which describe the deterioration process. The parameters associated with these models have to be estimated through statistical interference, which introduces uncertainties in parameter estimates. As the structural reliability indices which are incorporated in the reliability-based redundancy factor can be considered as random variable, this redundancy factor itself is a random variable as well. In case additional information becomes available, the distribution function can be updated by taking into account this extra information. In this contribution, a framework is developed, which allows for the incorporation of additional information in the uncertain reliability index and the associated redundancy factor through Bayesian updating. It is shown that in case additional information on a main variable is gathered, this has a significant effect on the ...
IABSE Congress, Stockholm 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment, 2016
Despite the development of structural codes such as the Eurocodes, one has to acknowledge that st... more Despite the development of structural codes such as the Eurocodes, one has to acknowledge that structural robustness is still an issue of controversy, being underlined by several structural failures in the past decades. One of the problems is the lack of a procedure to quantify the robustness of a structure in an objective way. In this contribution the robustness of a reference reinforced concrete frame is quantified applying a multi-level computational-efficient calculation scheme and using a risk-based robustness index to investigate the effectiveness of the Eurocode guidelines. Hereby the nonlinear behaviour of the reinforced concrete elements and the global behaviour of the structural frame are taken into account.
Engineering Structures, 2021
Structure and Infrastructure Engineering, 2021
Reinforced concrete structures are often subjected to corrosion, inducing a decreasing reliabilit... more Reinforced concrete structures are often subjected to corrosion, inducing a decreasing reliability over time. This corrosion often exhibits spatial variation, which can be modelled by random fields...
Lecture Notes in Civil Engineering, 2021
This publication is part of the proceedings of the <i>Biot-Bažant</i> <i>Confer... more This publication is part of the proceedings of the <i>Biot-Bažant</i> <i>Conference on Engineering Mechanics and Physics of Porous</i> <i>Materials</i>, which took place virtually on June 1-3, 2021. It contains a one-page abstract and the video of the talk that was given at the conference.
Applied Sciences, 2021
The alternative load path method is widely used to assess the progressive collapse performance of... more The alternative load path method is widely used to assess the progressive collapse performance of reinforced concrete structures. As an alternative to an accurate non–linear dynamic analysis, an energy–based method (EBM) can also be adopted to approximately calculate the dynamic load–bearing capacity curve or the dynamic resistance based on a static capacity curve. However, dynamic effects cannot be explicitly taken into account in the EBM. The model uncertainty associated with the use of the EBM for evaluating the dynamic ultimate capacity of structural frames has not yet been quantified. Knowledge of this model uncertainty is however necessary when applying EBM as part of reliability calculations, for example, in relation to structural robustness quantification. Hence, this article focuses on the evaluation of the performance of the EBM and the quantification of its model uncertainty in the context of reliability–based assessments of progressive or disproportionate collapse. The i...
Quality inspection of strength properties has to ensure that the used materials comply with their... more Quality inspection of strength properties has to ensure that the used materials comply with their specified requirements. Based on the average outgoing quality limit concept, conformity criteria can be designed and evaluated in an objective way. In this contribution, the conformity criteria for the yield strength of steel reinforcement bars given in the European Standard EN 10080 and the German Standard DIN 488-6 are evaluated based on this concept. It was shown that the current conformity parameters suggested in these standards yield OC-lines that cross the limiting boundary. Hence, subsequently, alternative values for the conformity control parameters are proposed. Finally, it was shown that conformity control of reinforcing steel has a beneficial influence on the reliability level of a reinforced concrete beam.
IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019
Recently, several structural failures demonstrated the disastrous consequences of progressive col... more Recently, several structural failures demonstrated the disastrous consequences of progressive collapse and raised the awareness of the engineering community. However the low probability of progressive collapse makes it uneconomical to design every building against progressive collapse using conventional design methods. Furthermore in most cases the initiating events of progressive collapses are unknown during the design. As such, consideration of secondary load-carrying mechanisms can be an effective alternative. These mechanisms include compressive arch action (CAA) and tensile catenary action (TCA) in reinforced concrete (RC) beams. Several researchers have investigated the effects of CAA and TCA experimentally and numerically in individual RC beams. However to date limited studies have been carried out to study these mechanisms in RC beam-grids. Hence in this contribution a validated numerical model is developed to study and quantify the individual contributions and development o...
The Eurocodes currently do not provide a coherent reliability-based justification for the semi-pr... more The Eurocodes currently do not provide a coherent reliability-based justification for the semi-probabilistic design format of temporary structures. Besides the need for suitable target reliability levels, a coherent definition of partial factors is needed, adjusted according to the chosen target reliability level and the intended reference period considered for the design of the temporary structure. When developing such a partial factor approach, attention should be given to the coherency with current Eurocodes to avoid conceptual discrepancies between the design of long-term and temporary structures. In this contribution a full-probabilistic framework for the structural reliability quantification of temporary structures is developed, based on Latin hypercube sampling. A sensitivity study is performed to detect the most important variables to be considered for the reliability analysis. The framework is subsequently used to determine the inherent reliability levels of scaffolds assoc...
Existing concrete bridges can show signs of deterioration, e.g. due to corrosion, in which case t... more Existing concrete bridges can show signs of deterioration, e.g. due to corrosion, in which case the question arises whether these bridges still have an acceptable safety level. To obtain additional information about the state of the structure, different types of information can be gathered. However, the measurements performed are often not used directly to update the estimate of the corrosion degree of the bridge and the resulting information from different measurement types is not combined. In this contribution, it is investigated how parameters of the service life models for concrete girders subjected to chloride-induced corrosion can be updated based on heterogeneous measurement data, with the focus on modal measurements and strain measurements. The posterior distributions of these parameters are generated based on Bayesian updating. These updated distributions can be used to get a more accurate estimate of the real deterioration state of the bridge. Based on this, the failure pr...
Engineering Structures, 2020
Membrane structures are widely used because of their lightweight properties and expressive archit... more Membrane structures are widely used because of their lightweight properties and expressive architectural shapes. However, there does not yet exist a unified design approach for membrane structures as is available for conventional buildings. Because of their flexibility, membrane structures exhibit a different structural behaviour than conventional buildings. Membrane structures are doubly curved, prestressed and the prestress contributes to the stiffness. The structural response of these structures is non-linear, and the hanging and arching directions interact. A probabilistic framework for tensioned membrane structures is developed herein. Using this tool, partial factors are calibrated for a representative tensioned hypar membrane structure made of PVC-coated polyester fabric. Reliability analyses are performed using a First Order Reliability Method in combination with Latin Hypercube Sampling. The approach is illustrated for two load cases, i.e. considering snow load and wind upl...
Reinforced concrete structures degrade over time, among others due to corrosion. This degradation... more Reinforced concrete structures degrade over time, among others due to corrosion. This degradation process is not uniform along the structure. Monitoring and inspections can be used to detect damage and update a deterioration model of the structure. In this work, a model-based method is used to identify damage through the calibration of a FEM model based on modal characteristics. The model calibration is performed by means of a Bayesian method, using MCMC to sample the posterior distributions of model parameters for the time-dependent degradation of material properties. The calibrated model can then be used for a more accurate prediction of the remaining service life. Furthermore, it enables to be implemented in a pre-posterior analysis framework to determine theVoI of the monitoring and inspection program for comparison of different monitoring and inspection strategies.
Based on experimental research on a real-scale one-way reinforced concrete slab with two spans fo... more Based on experimental research on a real-scale one-way reinforced concrete slab with two spans for which the internal support was removed, a numerical model in ABAQUS was developed and validated. The model is subsequently used to investigate the uncertainty of the load bearing capacity of the damaged slab considering four key random variables. Further, the probability density evolution method (PDEM) is applied for the reliability assessment. Although PDEM has in general been applied to solve dynamic reliability problems, in this contribution this method was adapted and applied to a static problem. The PDF of the load bearing capacity is calculated considering the ultimate load bearing capacity of the slab in its damaged state, i.e. the load corresponding with the rupture of the reinforcement bars at the inner support due to the developed tensile membrane action (TMA). Taking into account the obtained PDF for the capacity of the damaged system, the reliability index of the damaged sl...
IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019
The framework of pre-posterior decision analysis has a large potential as a decision support tool... more The framework of pre-posterior decision analysis has a large potential as a decision support tool in structural engineering. It seems ideally suited to tackle problems related to determining the value of Structural Health Monitoring and is commonly applied in inspection and maintenance planning. However, the application of this methodology for integrated life-cycle cost decision making related to monitoring of time-dependent and spatial degradation phenomena in concrete structures, needs further investigation. In this work, the time- dependent and spatial degradation phenomena will be coupled to the pre-posterior decision making approach and applied on concrete beams under bending, subjected to corrosion of the reinforcement. A framework is set up to determine the value of information of inspections enabling adequate decision-making. The methodology incorporates Bayesian updating based on the uncertain inspection outcomes. The framework will be illustrated by application on a simply...
When a continuous reinforced concrete slab is excessively loaded or a certain support is lost due... more When a continuous reinforced concrete slab is excessively loaded or a certain support is lost due to an accidental event, membrane action can be activated in order to generate an additional load transfer to neighbouring supports, which can considerably enchance the load-carrying capacity. This can delay or even prevent a progressive collapse and increase the robustness of concrete structures. In this contribution, the sensitivity of the collapse load of a one-way RC slab to variations of the different design variables is assessed, both for an undamaged situation and a damaged situation considering the removal of an intermediate support. Consequently, a probabilistic model for the load-bearing capacity is established and finally the quantification of the structural robustness is discussed using deterministic and reliability-based robustness indices.
IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management, 2019
Despite the recent amount of theoretical and technological developments, structural robustness is... more Despite the recent amount of theoretical and technological developments, structural robustness is still an issue of controversy being underlined by several structural failures in the past. Current design codes point out different strategies, among which strategies to limit damages due to the collapse of a load-bearing member by applying prescriptive design and detailing rules. For example for consequence class 2 structures EN1991-1-7 defines a risk class CC2b for which also vertical ties are required. However, the background of the design values of vertical ties in current codes is not clear and their adequacy should be validated. Moreover effects such as membrane action and Vierendeel action are important to consider when assessing structural robustness and are difficult to incorporate when applying only traditional design methodologies. To this extent a set of numerical simulations have been executed in this contribution in order to verify the progressive collapse behaviour of RC ...
Before implementing a bridge monitoring strategy, a bridge manager would like to know the return ... more Before implementing a bridge monitoring strategy, a bridge manager would like to know the return on investment. Moreover, in order to spend the available budget as efficiently as possible, the monitoring strategy should be optimized, i.e., the type of measurements but also the time and locations at which these are performed. For this purpose, the Value of Information (VoI) can be used. The VoI represents an estimate of the benefit that can be gained from a monitoring strategy before it is actually implemented. By comparing the VoI of different alternative strategies, the one with the highest VoI can be selected. As such, the VoI is a tool for objective decision-making. The calculation of the VoI is based on pre-posterior analyses, including Bayesian updating of model parameters based on yet unknown monitoring outcomes. When calculating the VoI for an actual case, some challenges arise. First, the calculation of the VoI requires a number of assumptions on different input parameters. ...
Progressive collapse resistance of a building structure is often investigated by the notional rem... more Progressive collapse resistance of a building structure is often investigated by the notional removal of one or more vertical load bearing elements from the structural system. Usually, a nonlinear dynamic analysis is needed to perform such an analysis. To avoid the complex nonlinear dynamic analysis, the energy-based method (EBM) is a promising method to predict the maximum dynamic responses of a structural system, where the dynamic load-bearing capacity curve is derived from the static load-displacement curve based on the principle of energy conservation. In this contribution, the performance of the EBM is evaluated based on a validated finite element model of a tested RC slab. Subsequently, 60 samples are generated by using Latin Hypercube Sampling (LHS), taking into account probability distributions for the most important variables. Both static analyses and direct dynamic analyses are executed for every sample set. Based on the results of the stochastic analyses, the EBM is obser...
In order to assess the structural reliability and redundancy with respect to deterioration, it is... more In order to assess the structural reliability and redundancy with respect to deterioration, it is required to select appropriate models which describe the deterioration process. The parameters associated with these models have to be estimated through statistical interference, which introduces uncertainties in parameter estimates. As the structural reliability indices which are incorporated in the reliability-based redundancy factor can be considered as random variable, this redundancy factor itself is a random variable as well. In case additional information becomes available, the distribution function can be updated by taking into account this extra information. In this contribution, a framework is developed, which allows for the incorporation of additional information in the uncertain reliability index and the associated redundancy factor through Bayesian updating. It is shown that in case additional information on a main variable is gathered, this has a significant effect on the ...
IABSE Congress, Stockholm 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment, 2016
Despite the development of structural codes such as the Eurocodes, one has to acknowledge that st... more Despite the development of structural codes such as the Eurocodes, one has to acknowledge that structural robustness is still an issue of controversy, being underlined by several structural failures in the past decades. One of the problems is the lack of a procedure to quantify the robustness of a structure in an objective way. In this contribution the robustness of a reference reinforced concrete frame is quantified applying a multi-level computational-efficient calculation scheme and using a risk-based robustness index to investigate the effectiveness of the Eurocode guidelines. Hereby the nonlinear behaviour of the reinforced concrete elements and the global behaviour of the structural frame are taken into account.
Engineering Structures, 2021