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J. van der Werf
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Master thesis
(2021)
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J. van der Werf, M. Korff, A.P. van den Eijnden, T. Schweckendiek, Mark Post, A.A. Roubos
Reliability analysis is a rational method for dealing with uncertainties. It is increasingly used for the design and assessment of (civil) structures. Reliability analysis, possibly in combination with performance data, allows for instance to update (extend) the lifetime of existing quay wall structures. This gives economic advantages when assessing quay walls, figuring there are thousands of kilometres of quay walls worldwide. Soil-structure analysis (e.g. analysis of quay walls) is however complex and in general requires finite element (FE) models. Conventional reliability methods are mostly incapable of dealing with FE models because they have long (infeasible) calculation times e.g. Monte Carlo, or they cannot deal with the typical noisy and incomplete FE model output e.g. FORM. One way of dealing with these challenges is by using a metamodelling approach, i.e. build up and make use of a response surface on a limited number of model evaluations. One specific application which uses metamodelling is ERRAGA, which is an abbreviation for Efficient and Robust Reliability Analysis for Geotechnical Applications. This thesis investigates the potential of ERRAGA/metamodelling for reliability analysis of quay walls in engineering practice.\medskip
In this thesis ERRAGA is tested on two realistic case studies located in the port of Rotterdam. The first case is called the ‘Sleepbootkade’, a quay constructed from a combi wall with anchors. The second case study is called the HHTP-quay, a combi wall with relieving platform and MV-piles. In the first case focus is placed on getting to understand the details and workings of the ERRAGA method. In the second case focus has been put on the creation of the reliability model and the practical applicability of ERRAGA using the experiences of the first case. Two critical limit states are tested within the case studies: wall failure in bending and geotechnical failure. Especially the limit state geotechnical failure is challenging as relevant output parameters are known to be noisy and/or incomplete.\medskip
The main finding of this thesis is that reliability analysis of quay walls using ERRAGA in combination with a numerical model shows good potential. ERRAGA can generate reliable and accurate results within only hundreds of realizations, hereby overcoming the main drawbacks of existing reliability methods. Main drawback of the ERRAGA method seems to be its inherent complexity and ‘black box’ nature. For the user to employ the full potential of the method some more in depth knowledge and especially the user-defined settings are required. Based on the gained experiences in this thesis some first recommendations are presented for the use and application of ERRAGA in projects. ...
In this thesis ERRAGA is tested on two realistic case studies located in the port of Rotterdam. The first case is called the ‘Sleepbootkade’, a quay constructed from a combi wall with anchors. The second case study is called the HHTP-quay, a combi wall with relieving platform and MV-piles. In the first case focus is placed on getting to understand the details and workings of the ERRAGA method. In the second case focus has been put on the creation of the reliability model and the practical applicability of ERRAGA using the experiences of the first case. Two critical limit states are tested within the case studies: wall failure in bending and geotechnical failure. Especially the limit state geotechnical failure is challenging as relevant output parameters are known to be noisy and/or incomplete.\medskip
The main finding of this thesis is that reliability analysis of quay walls using ERRAGA in combination with a numerical model shows good potential. ERRAGA can generate reliable and accurate results within only hundreds of realizations, hereby overcoming the main drawbacks of existing reliability methods. Main drawback of the ERRAGA method seems to be its inherent complexity and ‘black box’ nature. For the user to employ the full potential of the method some more in depth knowledge and especially the user-defined settings are required. Based on the gained experiences in this thesis some first recommendations are presented for the use and application of ERRAGA in projects. ...
Reliability analysis is a rational method for dealing with uncertainties. It is increasingly used for the design and assessment of (civil) structures. Reliability analysis, possibly in combination with performance data, allows for instance to update (extend) the lifetime of existing quay wall structures. This gives economic advantages when assessing quay walls, figuring there are thousands of kilometres of quay walls worldwide. Soil-structure analysis (e.g. analysis of quay walls) is however complex and in general requires finite element (FE) models. Conventional reliability methods are mostly incapable of dealing with FE models because they have long (infeasible) calculation times e.g. Monte Carlo, or they cannot deal with the typical noisy and incomplete FE model output e.g. FORM. One way of dealing with these challenges is by using a metamodelling approach, i.e. build up and make use of a response surface on a limited number of model evaluations. One specific application which uses metamodelling is ERRAGA, which is an abbreviation for Efficient and Robust Reliability Analysis for Geotechnical Applications. This thesis investigates the potential of ERRAGA/metamodelling for reliability analysis of quay walls in engineering practice.\medskip
In this thesis ERRAGA is tested on two realistic case studies located in the port of Rotterdam. The first case is called the ‘Sleepbootkade’, a quay constructed from a combi wall with anchors. The second case study is called the HHTP-quay, a combi wall with relieving platform and MV-piles. In the first case focus is placed on getting to understand the details and workings of the ERRAGA method. In the second case focus has been put on the creation of the reliability model and the practical applicability of ERRAGA using the experiences of the first case. Two critical limit states are tested within the case studies: wall failure in bending and geotechnical failure. Especially the limit state geotechnical failure is challenging as relevant output parameters are known to be noisy and/or incomplete.\medskip
The main finding of this thesis is that reliability analysis of quay walls using ERRAGA in combination with a numerical model shows good potential. ERRAGA can generate reliable and accurate results within only hundreds of realizations, hereby overcoming the main drawbacks of existing reliability methods. Main drawback of the ERRAGA method seems to be its inherent complexity and ‘black box’ nature. For the user to employ the full potential of the method some more in depth knowledge and especially the user-defined settings are required. Based on the gained experiences in this thesis some first recommendations are presented for the use and application of ERRAGA in projects.
In this thesis ERRAGA is tested on two realistic case studies located in the port of Rotterdam. The first case is called the ‘Sleepbootkade’, a quay constructed from a combi wall with anchors. The second case study is called the HHTP-quay, a combi wall with relieving platform and MV-piles. In the first case focus is placed on getting to understand the details and workings of the ERRAGA method. In the second case focus has been put on the creation of the reliability model and the practical applicability of ERRAGA using the experiences of the first case. Two critical limit states are tested within the case studies: wall failure in bending and geotechnical failure. Especially the limit state geotechnical failure is challenging as relevant output parameters are known to be noisy and/or incomplete.\medskip
The main finding of this thesis is that reliability analysis of quay walls using ERRAGA in combination with a numerical model shows good potential. ERRAGA can generate reliable and accurate results within only hundreds of realizations, hereby overcoming the main drawbacks of existing reliability methods. Main drawback of the ERRAGA method seems to be its inherent complexity and ‘black box’ nature. For the user to employ the full potential of the method some more in depth knowledge and especially the user-defined settings are required. Based on the gained experiences in this thesis some first recommendations are presented for the use and application of ERRAGA in projects.
Journal article
(2019)
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J. J. van der Werf, P. L.M. de Vet, M. P. Boersema, T. J. Bouma, A. J. Nolte, R. A. Schrijvershof, L. M. Soissons, J. Stronkhorst, E. van Zanten, T. Ysebaert
The Eastern Scheldt, a tidal basin in the southwest of The Netherlands, underwent large physical and ecological changes due to a system-wide human interference. The construction of a storm surge barrier at the seaward side and closure of the upstream branches in the 1980s resulted in intertidal flat erosion. This has far reaching consequences for the ecological functioning of these habitats, especially as foraging ground for many wader species. Therefore, a 1.3 million m3 sand nourishment is foreseen on the Roggenplaat intertidal shoal to mitigate the erosion and preserve suitable foraging habitat for waders for the coming 25 years. This paper presents an integral nourishment design approach. It consists of the following steps: (i) understanding the morphology and ecology, (ii) translation of the nourishment objective into an evaluation framework, (iii) construction of a suitability map indicating potential nourishment locations, (iv) generation of nourishment designs, (v) short-term morphodynamic numerical model simulations, (vi) estimation of the long-term shoal development using a simplified approach, (vii) integral evaluation leading to the preferred design. This integral approach resulted in a design that is expected to fulfill the Roggenplaat nourishment objective, accounting for ecological, morphological, economical and technical aspects. This integrated approach could form a basis for future intertidal shoal nourishment designs worldwide.
...
The Eastern Scheldt, a tidal basin in the southwest of The Netherlands, underwent large physical and ecological changes due to a system-wide human interference. The construction of a storm surge barrier at the seaward side and closure of the upstream branches in the 1980s resulted in intertidal flat erosion. This has far reaching consequences for the ecological functioning of these habitats, especially as foraging ground for many wader species. Therefore, a 1.3 million m3 sand nourishment is foreseen on the Roggenplaat intertidal shoal to mitigate the erosion and preserve suitable foraging habitat for waders for the coming 25 years. This paper presents an integral nourishment design approach. It consists of the following steps: (i) understanding the morphology and ecology, (ii) translation of the nourishment objective into an evaluation framework, (iii) construction of a suitability map indicating potential nourishment locations, (iv) generation of nourishment designs, (v) short-term morphodynamic numerical model simulations, (vi) estimation of the long-term shoal development using a simplified approach, (vii) integral evaluation leading to the preferred design. This integral approach resulted in a design that is expected to fulfill the Roggenplaat nourishment objective, accounting for ecological, morphological, economical and technical aspects. This integrated approach could form a basis for future intertidal shoal nourishment designs worldwide.