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To investigate the structural behaviour of large-diameter spiral-welded steel tubes under bending, a full scale experimental program has been performed, consisting of thirteen 42-inch diameter, spiral-welded steel tubes with D/t ratios ranging between 65 and 120. Additionally, numerical studies have been conducted, using nonlinear finite element simulations. A model has been developed to simulate the performed tests, using the actual material properties and initial geometric imperfections obtained from the tested tubes. Finally, a parametric investigation has been performed that investigates the influence of initial geometric imperfections and presence of girth and coil connection welds on the bending behaviour of the considered tubes., Steel & Composite Structures

Civil Engineering and Geosciences, Structural Engineering

Civil Engineering and Geosciences, Structural Engineering

Civil Engineering and Geosciences, Structural Engineering

To investigate the structural behaviour of large-diameter spiral-welded steel tubes under bending, a full scale experimental program has been performed, consisting of thirteen 42-inch diameter, spiral-welded steel tubes with D/t ratios ranging between 65 and 120. Additionally, numerical studies have been conducted, using nonlinear finite element simulations. A model has been developed to simulate the performed tests, using the actual material properties and initial geometric imperfections obtained from the tested tubes. Finally, a parametric investigation has been performed that investigates the influence of initial geometric imperfections and presence of girth and coil connection welds on the bending behaviour of the considered tubes., Steel & Composite Structures

To investigate the structural behaviour of large-diameter spiral-welded steel tubes under bending, a full scale experimental program has been performed, consisting of thirteen 42-inch diameter, spiral-welded steel tubes with D/t ratios ranging between 65 and 120. Additionally, numerical studies have been conducted, using nonlinear finite element simulations. A model has been developed to simulate the performed tests, using the actual material properties and initial geometric imperfections obtained from the tested tubes. Finally, a parametric investigation has been performed that investigates the influence of initial geometric imperfections and presence of girth and coil connection welds on the bending behaviour of the considered tubes., Steel & Composite Structures

In this study, the bending behaviour of tubular members is investigated. The thesis consists of four parts: Part I: Literature study of the bending behaviour of tubular members Part II: Spiral-welded tubes for application in combined walls Part III: Deformation of buried pipelines crossing active strike-slip faults Part IV: Closure In Part I, a literature study of the bending of tubular members is presented. In Parts II and III, two more specific topics within this broad field of research are discussed. In a final part of the thesis, an evaluation of the performed research is presented., Steel & Composite Structures

This paper presents the results of extensive measurements on weld toe geometry of as-welded and TIG-dressed butt welded connections in high strength steels S460, S690 and very high strength steels S890 and S1100. Descriptions of the measurement techniques and data analysis are presented. Four weld toe parameters have been formulated to characterize the weld toe: weld toe radius, weld toe angle, weld height and undercut. From the data can be concluded that TIG-dressing, on average, has a beneficial effect on the geometry of the weld toe. However, TIG-dressed weld toes have different appearances and as a result, weld toe parameters show more variation after TIG-dressing. An improvement of the weakest link is therefore not guaranteed. The reheating of weld material and surrounding parent material results in a new fusion zone (FZ) and heat affected zone (HAZ). Hardness measurements have been performed in all different zones and show an increase of hardness as a result of TIG-dressing, with an occasional exception in the very high strength steels., Structural Engineering, Civil Engineering and Geosciences

This paper presents the results of extensive measurements on weld toe geometry of as-welded and TIG-dressed butt welded connections in high strength steels S460, S690 and very high strength steels S890 and S1100. Descriptions of the measurement techniques and data analysis are presented. Four weld toe parameters have been formulated to characterize the weld toe: weld toe radius, weld toe angle, weld height and undercut. From the data can be concluded that TIG-dressing, on average, has a beneficial effect on the geometry of the weld toe. However, TIG-dressed weld toes have different appearances and as a result, weld toe parameters show more variation after TIG-dressing. An improvement of the weakest link is therefore not guaranteed. The reheating of weld material and surrounding parent material results in a new fusion zone (FZ) and heat affected zone (HAZ). Hardness measurements have been performed in all different zones and show an increase of hardness as a result of TIG-dressing, with an occasional exception in the very high strength steels., Structural Engineering, Civil Engineering and Geosciences

Weld improvement techniques are aimed at reducing the notch effects of welds and generally focus on two aspects: a change of geometry of the weld toe and a change of the weld residual stresses. In this paper, fatigue tests are discussed, performed on butt welded specimens in steel grades ranging from S460 to S1100 in the TIG-dressed condition. The test results are compared with modelled fatigue strength according to the notch stress theory and similar specimens in the as-welded condition. The changed notch geometry of the joints is based on the results of a parallel program of weld toe geometry measurements. The individual data points and their failure mode give good qualitative insight in the effect of TIG-dressing on butt welded joints in high strength steel. Overall, a positive effect of TIG-dressing on the weld toe is visible. On the basis of a large dataset of measured weld toe geometries a model has been developed based on the notch stress theory. The theoretical results of the model are compared with the results of the physical tests, showing significant differences between the model and the fatigue tests., Structural Engineering, Civil Engineering and Geosciences

Weld improvement techniques are aimed at reducing the notch effects of welds and generally focus on two aspects: a change of geometry of the weld toe and a change of the weld residual stresses. In this paper, fatigue tests are discussed, performed on butt welded specimens in steel grades ranging from S460 to S1100 in the TIG-dressed condition. The test results are compared with modelled fatigue strength according to the notch stress theory and similar specimens in the as-welded condition. The changed notch geometry of the joints is based on the results of a parallel program of weld toe geometry measurements. The individual data points and their failure mode give good qualitative insight in the effect of TIG-dressing on butt welded joints in high strength steel. Overall, a positive effect of TIG-dressing on the weld toe is visible. On the basis of a large dataset of measured weld toe geometries a model has been developed based on the notch stress theory. The theoretical results of the model are compared with the results of the physical tests, showing significant differences between the model and the fatigue tests., Structural Engineering, Civil Engineering and Geosciences

This paper presents the results of extensive measurements on weld toe geometry of as-welded and TIG-dressed butt welded connections in high strength steels S460, S690 and very high strength steels S890 and S1100. Descriptions of the measurement techniques and data analysis are presented. Four weld toe parameters have been formulated to characterize the weld toe: weld toe radius, weld toe angle, weld height and undercut. From the data can be concluded that TIG-dressing, on average, has a beneficial effect on the geometry of the weld toe. However, TIG-dressed weld toes have different appearances and as a result, weld toe parameters show more variation after TIG-dressing. An improvement of the weakest link is therefore not guaranteed. The reheating of weld material and surrounding parent material results in a new fusion zone (FZ) and heat affected zone (HAZ). Hardness measurements have been performed in all different zones and show an increase of hardness as a result of TIG-dressing, with an occasional exception in the very high strength steels., Structural Engineering, Civil Engineering and Geosciences

A European research project (RFCS) has started to provide economic and safe guidance for the design of spirally welded tubes in combined walls. The main motivation for this project called COMBITUBE is that the current Eurocode 3 regulations for tubes in quay walls lead to uneconomic designs, because of poor local buckling design rules for these tubes. Because the most important load in quay walls is bending due to earth load, economic design implies a high diameter to wall thickness ratio. For relatively thin walled shells, the Eurocode 3 rules provide good results for the local buckling stress. For thicker walled shells where local buckling occurs when a part of the cross section has yielded, rather poor and uneconomic estimates of the local buckling bending moment are obtained. Also, no information on the deformation capacity is given. A solution for this problem is the application of strain based design methods, where the strain at local buckling is determined, from which the curvature (deformation capacity) and via the stress strain relationship, the bending moment can be obtained. The advantages of strain based design are explained. In comparison with longitudinally welded tubes and seamless tubes not much bending test results are available for spirally welded tubes. Therefore in the project full scale four point bending tests on spirally welded tubes with diameters up to 1060 mm are performed. Test results obtained so far are presented. The test results are used for the validation of FEA models for parameter studies where the effect of geometrical conditions (spiral welds and girth welds, geometrical imperfections), material properties and loading (mainly combinations of bending moment, normal force and earth loads) on the local buckling curvature and bending moment capacity are determined. Therefore, in the test program accurate measurements are performed of these conditions. Moment - curvature and curvature - ovalisation relationships are presented and compa, Structural Engineering, Civil Engineering and Geosciences

A European research project (RFCS) has started to provide economic and safe guidance for the design of spirally welded tubes in combined walls. The main motivation for this project called COMBITUBE is that the current Eurocode 3 regulations for tubes in quay walls lead to uneconomic designs, because of poor local buckling design rules for these tubes. Because the most important load in quay walls is bending due to earth load, economic design implies a high diameter to wall thickness ratio. For relatively thin walled shells, the Eurocode 3 rules provide good results for the local buckling stress. For thicker walled shells where local buckling occurs when a part of the cross section has yielded, rather poor and uneconomic estimates of the local buckling bending moment are obtained. Also, no information on the deformation capacity is given. A solution for this problem is the application of strain based design methods, where the strain at local buckling is determined, from which the curvature (deformation capacity) and via the stress strain relationship, the bending moment can be obtained. The advantages of strain based design are explained. In comparison with longitudinally welded tubes and seamless tubes not much bending test results are available for spirally welded tubes. Therefore in the project full scale four point bending tests on spirally welded tubes with diameters up to 1060 mm are performed. Test results obtained so far are presented. The test results are used for the validation of FEA models for parameter studies where the effect of geometrical conditions (spiral welds and girth welds, geometrical imperfections), material properties and loading (mainly combinations of bending moment, normal force and earth loads) on the local buckling curvature and bending moment capacity are determined. Therefore, in the test program accurate measurements are performed of these conditions. Moment - curvature and curvature - ovalisation relationships are presented and compa, Structural Engineering, Civil Engineering and Geosciences

When high strength steels are applicated in dynamically loaded structures, fatigue problems can arise. In most current design codes, the fatigue strength of high strength steels is either not discussed or determined as similar to mild steels. This assumption can be related to the dominance of the crack propagation life during in the total fatigue life when considering welded connections. Weld improvements can increase the length of the crack initiation life and thus increase the total fatigue life and may lead to a difference in fatigue strength between high strength steel and mild steels. This study focuses on the the effects of TIG-dressing on the weld toe geometry and the fatigue strength of TIG-dressed specimens. First a literature study is presented which summarizes earlier researches into the effect of TIG-dressing on fatigue strength and the behaviour of high strength steel in fatigue conditions, both in an as welded situation as after TIG-dressing. The weld toe geometry before and after TIG-dressing is determined. This leads to a extensive data set containing the geometry of the complete weld. The weld toe is then described with the aid of four parameters: weld toe radius, weld toe angle, weld height and undercut. Any influence of the static strength of the material, or any differences between rolled and cast steel are investigated. A comparison is made between the as welded specimens and TIG-dressed specimens. This changed geometry has been coupled to a changed fatigue strength with the aid of the notch stress approach. FEM analyses of the weld toe, based on measured geometries, have been carried out to determine stress concentration factors. Adjustments of the fatigue strength to account for loading mode, thickness, residual stress and mean stress have been derived from literature. A small reduction in residual stress, caused by the TIG-dressing procedure, has also been derived from literature. Fatigue tests have been carried out on 24 specimens ranging fr, Steel Structures, Structural Engineering, Civil Engineering and Geosciences

When high strength steels are applicated in dynamically loaded structures, fatigue problems can arise. In most current design codes, the fatigue strength of high strength steels is either not discussed or determined as similar to mild steels. This assumption can be related to the dominance of the crack propagation life during in the total fatigue life when considering welded connections. Weld improvements can increase the length of the crack initiation life and thus increase the total fatigue life and may lead to a difference in fatigue strength between high strength steel and mild steels. This study focuses on the the effects of TIG-dressing on the weld toe geometry and the fatigue strength of TIG-dressed specimens. First a literature study is presented which summarizes earlier researches into the effect of TIG-dressing on fatigue strength and the behaviour of high strength steel in fatigue conditions, both in an as welded situation as after TIG-dressing. The weld toe geometry before and after TIG-dressing is determined. This leads to a extensive data set containing the geometry of the complete weld. The weld toe is then described with the aid of four parameters: weld toe radius, weld toe angle, weld height and undercut. Any influence of the static strength of the material, or any differences between rolled and cast steel are investigated. A comparison is made between the as welded specimens and TIG-dressed specimens. This changed geometry has been coupled to a changed fatigue strength with the aid of the notch stress approach. FEM analyses of the weld toe, based on measured geometries, have been carried out to determine stress concentration factors. Adjustments of the fatigue strength to account for loading mode, thickness, residual stress and mean stress have been derived from literature. A small reduction in residual stress, caused by the TIG-dressing procedure, has also been derived from literature. Fatigue tests have been carried out on 24 specimens ranging fr, Steel Structures, Structural Engineering, Civil Engineering and Geosciences