A.M. (Nol) Gresnigt - Academia.edu (original) (raw)
Papers by A.M. (Nol) Gresnigt
The present study examines the behavior of steel pipeline elbows subjected to strong cyclic loadi... more The present study examines the behavior of steel pipeline elbows subjected to strong cyclic loading conditions. A set of experiments is conducted where in-plane cyclic bending with constant amplitude is applied on the elbow specimens by controlling the elbow enddisplacements, resulting in failure within the low-cycle-fatigue range. The experimental work is supported by finite element analysis using detailed numerical models that take into account geometrical and material nonlinearities. Cyclic plasticity related phenomena are accounted for with the use of advanced plasticity models focusing on the localized concentration of deformations at the critical positions where cracking is likely to take place. Finally, the experimental/FE results are compared with analytical elastic/plastic solution. The experimental results are used to develop a low-cycle-fatigue curve in the framework of the strain-based fatigue design concept. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE)
In the framework of the INDUSE project, which aims at innovative design method- ologies for the s... more In the framework of the INDUSE project, which aims at innovative design method- ologies for the seismic design of industrial equipment and piping systems, case studies have been carried out, performing static and dynamic seismic analyses for two existing steel pipe- line systems including steel supporting structures, situated in an area of moderate seismic ac- tivity: a) A long aboveground 10" ammonia transmission line situated on sleepers with a vertical expansion loop and ending with a fixed point. The system may be typical for long distance above ground pipelines and for pipelines on jetties. b) A 20" gas transmission pipeline at the interface of a buried pipeline section and an above ground piping section, including a branch connection, a vertical spring support structure and a fixed point, e.g. a tank nozzle. This system is typical for many plant piping systems. The calculations were made using commercially available software. Both simplified static equivalent ('u...
Modern high strength steels combine high strength with good ductility properties and good weldabi... more Modern high strength steels combine high strength with good ductility properties and good weldability. Reduced material and welding costs have made it economical to apply high strength steel grades X70 (API) and StE 480.7 TM (DIN), instead of lower grades like X60. In some countries however, the application of X70 and StE 480.7 TM is hampered because of existing rules for the maximum yield to tensile ratio (Re/Rm), and the maximum design stress. In this paper, results are presented of a research program, to investigate whether it is allowed to raise the limit for the measured Re/Rm (on delivery) from 0.85 to 0.87, and to raise the maximum Re for design calculations from 0.75 Rm to 0.85 Rm. The influence of the specific properties of high strength steel on all possible failure modes (limit-states) was considered. Attention is focused on the influence of weld metal matching and possible flaws in the weld on strain capacity of the pipe wall, and further on local buckling and burst due ...
Geohazards and Pipelines, 2021
Thin-Walled Structures, 2016
In the second part of this investigation, numerical simulations are conducted using nonlinear fin... more In the second part of this investigation, numerical simulations are conducted using nonlinear finite element simulations, to define the bending strength and deformation capacity of largediameter spiral-welded steel tubes. Under bending loading, the principal failure mode of those tubes is local buckling (wrinkling) of the tube wall, as shown experimentally in the companion paper (Part I) in a series of tests on 42-inch-diameter tubes [1], and this failure mode is explicitly simulated. Initially, a special-purpose numerical simulation of the cold bending process is conducted to calculate the corresponding residual stresses. Subsequently, a comparison with the test data on 42-inch-diameter tubes reported in Part I is conducted, using the actual material properties and initial geometric imperfections obtained from the tested specimens, as well as the residual stresses computed by the numerical process. Finally, a parametric investigation is performed on the influence of material properties, geometric initial imperfections and residual stresses on local buckling of spiral-welded tubes.
Bending moments on bends in pipelines may cause severe ovalization and stresses, both in longitud... more Bending moments on bends in pipelines may cause severe ovalization and stresses, both in longitudinal and circumferential directions. The bending stiffness depends not only on the radius of the bend, the diameter-to-wall-thickness ratio and the internal or external pressure, but also on the length of the bend, the loads due to the surrounding soil and the bending direction. After start of yielding, the bending moment may still increase considerably. For example, it can be shown that for bends with a radius-to-diameter ratio equal to 3, the maximum moment may be 2 or 3 times greater than the moment where first yielding started. Also the rotation capacity (the ability to follow imposed deformation) is many times greater than elastic theory can predict. In this paper, the strnctural behaviour of bends is analyzed. Improved analytical models for elastic design and new analytical models for plastic design are presented. The results of the analytical models are compared with test results and the results of finite element calculations.
Lecture Notes in Engineering, 1987
In this paper a calculation model for the relation between local load and indentation depth, incl... more In this paper a calculation model for the relation between local load and indentation depth, including internal pressure, is given. The formulas have been derived by means of theory of shells and theory of plasticity. Via coefficients and a few interventions these theoretical formulas have been adapted to the results of tests and the results of finite element calculations. The calculation model thus obtained is capable of predicting the real local load — indentation depth diagram in a sufficiently accurate manner.
24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 1, Parts A and B, 2005
In the development of design methods for single-pile flexible dolphins used for the berthing of b... more In the development of design methods for single-pile flexible dolphins used for the berthing of bulk carriers, the design stress has been gradually increased to the yield stress to employ the elastic energy absorption capacity of the pile more optimally. In recent guidelines, e.g. EAU 1996 [3] and PIANC 2002 [5], also the plastic yielding capacity is implicitly or explicitly included in the ultimate load-bearing capacity. This movement towards plastic design is not accompanied by the development of calculation models and design criteria to assess the plastic load-bearing capacity and relevant failure modes such as local buckling and ovalisation of the cross-section. To investigate the nonlinear load-deflection behaviour of a dolphin, a numerical model was developed based on the Beam on Nonlinear Winkler Foundation (BNWF) method [7] and extended for the plastic range of the steel pile using plasticity theory, which has been verified and confirmed by FEM analysis. The resulting Bruijn...
29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 5, Parts A and B, 2010
A promising possibility to reduce costs in pipelines that require corrosion resistant alloys (CRA... more A promising possibility to reduce costs in pipelines that require corrosion resistant alloys (CRA) is the use of lined pipe, consisting of a carbon steel load-bearing outer pipe that provides the structural capacity and a corrosion-resistant alloy (CRA) liner, protecting the carbon steel outer pipe from the transported corrosive product. The objective of the current research is to identify all variables that have an influence on the mechanical behaviour of lined pipe during bending and to determine their influence on this behaviour. The parameters that determine the resistance to pipe ovalisation and liner wrinkling are to be quantified, enabling safe and economic design of lined pipe for installation. This paper describes the approach and results obtained so far during the current research.
Volume 4: Pipeline and Riser Technology, 2011
A promising possibility to reduce costs in pipelines that require corrosion resistant alloys (CRA... more A promising possibility to reduce costs in pipelines that require corrosion resistant alloys (CRA) is the use of lined pipe, consisting of a carbon steel load-bearing outer pipe that provides the structural capacity and a corrosion-resistant alloy (CRA) liner, protecting the carbon steel outer pipe from the transported corrosive product. The objective of the current research is to identify all variables that have an influence on the mechanical behaviour of lined pipe during bending. The parameters that determine the resistance to pipe ovalisation and liner wrinkling have to be quantified, enabling safe and economic design of lined pipe for installation. In this paper, the influence of friction and mechanical bond on the behaviour of lined pipe during bending is investigated in three dimensional computational models. The numerical results are compared with the results of pure bending tests.
Volume 8: Seismic Engineering, 2013
In this paper the low cycle fatigue behaviour of steel elbows under strong cyclic loading conditi... more In this paper the low cycle fatigue behaviour of steel elbows under strong cyclic loading conditions (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data for in-plane bending. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the low-cycle fatigue of elbows, focusing on the stress and strain variations. Strain gauge measurements are compared with finite element models. Upon calculation of local strain variation at the critical location, the number of cycles to fracture can be estimated.
Design and Analysis of Pressure Vessels, Heat Exchangers and Piping Components, 2004
ABSTRACT In this paper the response of internally pressurized pipe elbows under bending loads (in... more ABSTRACT In this paper the response of internally pressurized pipe elbows under bending loads (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the ultimate capacity of 90 deg elbows, focusing on the failure mode (buckling or flattening) and the maximum bending strength. The effects of moderate pressure levels on the ultimate moment and the failure mode are examined extensively.
Volume 4: Production Pipelines and Flowlines; Project Management; Facilities Integrity Management; Operations and Maintenance; Pipelining in Northern and Offshore Environments; Strain-Based Design; Standards and Regulations, 2014
Numerical simulations are conducted to define the bending deformation capacity of large-diameter ... more Numerical simulations are conducted to define the bending deformation capacity of large-diameter spiral-welded tubes, towards efficient strain-based design. Under bending loading, the principal failure mode of those tubes is local buckling (wrinkling) of the tube wall. Bending moment, curvature and ovalization are monitored through the numerical analysis, and comparison is conducted with available test data on two 42-inch-diameter tubes, with D/t ratio of 67 and 119, described in detail elsewhere. The analysis accounts for the actual material properties. Initial geometric imperfections (profile, thickness, ovalization) are obtained from the tested specimens. Furthermore, residual stresses are also considered in the analysis, as computed by a numerical simulation of the cold bending process. A parametric analysis is also conducted on the influence of material properties, geometric initial imperfections and residual stresses on local buckling of spiral-welded tubes. Finally, a compari...
Volume 3: Pipeline and Riser Technology; CFD and VIV, 2007
A 12.75 inch outer diameter single walled pipe bending test was executed and theoretical and FE a... more A 12.75 inch outer diameter single walled pipe bending test was executed and theoretical and FE analysis of this test was performed as preparation for 12.75 inch outer diameter TFP bending tests. The main objective of the TFP bending tests was to determine the initiation and degree of liner wrinkling occurring during the TFP spooling-on phase when simulating the reeling pipelay installation method. Due to lack of a definition of liner wrinkling initiation, the crossing of a certain threshold of the liner wrinkle height was defined as liner wrinkling initiation. The bending tests results indicated that (1) the extent of liner wrinkling decreased if TFP with a high mechanical bonding strength was used. (2) The presence of a circumferential weld in the highly bonded TFPs initiated higher liner wrinkles at lower curvatures than in case no circumferential weld was present. (3) The ERW outer pipe longitudinal weld did not result in higher liner wrinkles. API residual compressive stress te...
Proceedings of the 10th Pacific Structural Steel Conference (PSSC 2013), 2013
A European research project (RFCS) has started to provide economic and safe guidance for the desi... more 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 curvatureovalisation relationships are presented and compared with theoretical predictions.
Progress in Structural Engineering and Materials, 1997
This review highlights some of the recent developments in steel design and construction, and its ... more This review highlights some of the recent developments in steel design and construction, and its associated research. In recent decades, labour costs have increased considerably while material costs have remained constant. Therefore, there is a tendency to simplify the most labour-intensive parts of a steel structure: the connections, thus cutting labour costs. Simplifying the fabrication process is of considerably more importance than minimizing the use of materials. Research has been carried out to support the process of simplification. This review reports on some of the practical outcomes of this research. Special attention is given to fabrication and erection-friendly connections, the application of preloaded fasteners, and unstiffened moment connections (including base plates). Finally, in the conclusions, the review identifies future research needs.
The present study examines the behavior of steel pipeline elbows subjected to strong cyclic loadi... more The present study examines the behavior of steel pipeline elbows subjected to strong cyclic loading conditions. A set of experiments is conducted where in-plane cyclic bending with constant amplitude is applied on the elbow specimens by controlling the elbow enddisplacements, resulting in failure within the low-cycle-fatigue range. The experimental work is supported by finite element analysis using detailed numerical models that take into account geometrical and material nonlinearities. Cyclic plasticity related phenomena are accounted for with the use of advanced plasticity models focusing on the localized concentration of deformations at the critical positions where cracking is likely to take place. Finally, the experimental/FE results are compared with analytical elastic/plastic solution. The experimental results are used to develop a low-cycle-fatigue curve in the framework of the strain-based fatigue design concept. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE)
In the framework of the INDUSE project, which aims at innovative design method- ologies for the s... more In the framework of the INDUSE project, which aims at innovative design method- ologies for the seismic design of industrial equipment and piping systems, case studies have been carried out, performing static and dynamic seismic analyses for two existing steel pipe- line systems including steel supporting structures, situated in an area of moderate seismic ac- tivity: a) A long aboveground 10" ammonia transmission line situated on sleepers with a vertical expansion loop and ending with a fixed point. The system may be typical for long distance above ground pipelines and for pipelines on jetties. b) A 20" gas transmission pipeline at the interface of a buried pipeline section and an above ground piping section, including a branch connection, a vertical spring support structure and a fixed point, e.g. a tank nozzle. This system is typical for many plant piping systems. The calculations were made using commercially available software. Both simplified static equivalent ('u...
Modern high strength steels combine high strength with good ductility properties and good weldabi... more Modern high strength steels combine high strength with good ductility properties and good weldability. Reduced material and welding costs have made it economical to apply high strength steel grades X70 (API) and StE 480.7 TM (DIN), instead of lower grades like X60. In some countries however, the application of X70 and StE 480.7 TM is hampered because of existing rules for the maximum yield to tensile ratio (Re/Rm), and the maximum design stress. In this paper, results are presented of a research program, to investigate whether it is allowed to raise the limit for the measured Re/Rm (on delivery) from 0.85 to 0.87, and to raise the maximum Re for design calculations from 0.75 Rm to 0.85 Rm. The influence of the specific properties of high strength steel on all possible failure modes (limit-states) was considered. Attention is focused on the influence of weld metal matching and possible flaws in the weld on strain capacity of the pipe wall, and further on local buckling and burst due ...
Geohazards and Pipelines, 2021
Thin-Walled Structures, 2016
In the second part of this investigation, numerical simulations are conducted using nonlinear fin... more In the second part of this investigation, numerical simulations are conducted using nonlinear finite element simulations, to define the bending strength and deformation capacity of largediameter spiral-welded steel tubes. Under bending loading, the principal failure mode of those tubes is local buckling (wrinkling) of the tube wall, as shown experimentally in the companion paper (Part I) in a series of tests on 42-inch-diameter tubes [1], and this failure mode is explicitly simulated. Initially, a special-purpose numerical simulation of the cold bending process is conducted to calculate the corresponding residual stresses. Subsequently, a comparison with the test data on 42-inch-diameter tubes reported in Part I is conducted, using the actual material properties and initial geometric imperfections obtained from the tested specimens, as well as the residual stresses computed by the numerical process. Finally, a parametric investigation is performed on the influence of material properties, geometric initial imperfections and residual stresses on local buckling of spiral-welded tubes.
Bending moments on bends in pipelines may cause severe ovalization and stresses, both in longitud... more Bending moments on bends in pipelines may cause severe ovalization and stresses, both in longitudinal and circumferential directions. The bending stiffness depends not only on the radius of the bend, the diameter-to-wall-thickness ratio and the internal or external pressure, but also on the length of the bend, the loads due to the surrounding soil and the bending direction. After start of yielding, the bending moment may still increase considerably. For example, it can be shown that for bends with a radius-to-diameter ratio equal to 3, the maximum moment may be 2 or 3 times greater than the moment where first yielding started. Also the rotation capacity (the ability to follow imposed deformation) is many times greater than elastic theory can predict. In this paper, the strnctural behaviour of bends is analyzed. Improved analytical models for elastic design and new analytical models for plastic design are presented. The results of the analytical models are compared with test results and the results of finite element calculations.
Lecture Notes in Engineering, 1987
In this paper a calculation model for the relation between local load and indentation depth, incl... more In this paper a calculation model for the relation between local load and indentation depth, including internal pressure, is given. The formulas have been derived by means of theory of shells and theory of plasticity. Via coefficients and a few interventions these theoretical formulas have been adapted to the results of tests and the results of finite element calculations. The calculation model thus obtained is capable of predicting the real local load — indentation depth diagram in a sufficiently accurate manner.
24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 1, Parts A and B, 2005
In the development of design methods for single-pile flexible dolphins used for the berthing of b... more In the development of design methods for single-pile flexible dolphins used for the berthing of bulk carriers, the design stress has been gradually increased to the yield stress to employ the elastic energy absorption capacity of the pile more optimally. In recent guidelines, e.g. EAU 1996 [3] and PIANC 2002 [5], also the plastic yielding capacity is implicitly or explicitly included in the ultimate load-bearing capacity. This movement towards plastic design is not accompanied by the development of calculation models and design criteria to assess the plastic load-bearing capacity and relevant failure modes such as local buckling and ovalisation of the cross-section. To investigate the nonlinear load-deflection behaviour of a dolphin, a numerical model was developed based on the Beam on Nonlinear Winkler Foundation (BNWF) method [7] and extended for the plastic range of the steel pile using plasticity theory, which has been verified and confirmed by FEM analysis. The resulting Bruijn...
29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 5, Parts A and B, 2010
A promising possibility to reduce costs in pipelines that require corrosion resistant alloys (CRA... more A promising possibility to reduce costs in pipelines that require corrosion resistant alloys (CRA) is the use of lined pipe, consisting of a carbon steel load-bearing outer pipe that provides the structural capacity and a corrosion-resistant alloy (CRA) liner, protecting the carbon steel outer pipe from the transported corrosive product. The objective of the current research is to identify all variables that have an influence on the mechanical behaviour of lined pipe during bending and to determine their influence on this behaviour. The parameters that determine the resistance to pipe ovalisation and liner wrinkling are to be quantified, enabling safe and economic design of lined pipe for installation. This paper describes the approach and results obtained so far during the current research.
Volume 4: Pipeline and Riser Technology, 2011
A promising possibility to reduce costs in pipelines that require corrosion resistant alloys (CRA... more A promising possibility to reduce costs in pipelines that require corrosion resistant alloys (CRA) is the use of lined pipe, consisting of a carbon steel load-bearing outer pipe that provides the structural capacity and a corrosion-resistant alloy (CRA) liner, protecting the carbon steel outer pipe from the transported corrosive product. The objective of the current research is to identify all variables that have an influence on the mechanical behaviour of lined pipe during bending. The parameters that determine the resistance to pipe ovalisation and liner wrinkling have to be quantified, enabling safe and economic design of lined pipe for installation. In this paper, the influence of friction and mechanical bond on the behaviour of lined pipe during bending is investigated in three dimensional computational models. The numerical results are compared with the results of pure bending tests.
Volume 8: Seismic Engineering, 2013
In this paper the low cycle fatigue behaviour of steel elbows under strong cyclic loading conditi... more In this paper the low cycle fatigue behaviour of steel elbows under strong cyclic loading conditions (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data for in-plane bending. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the low-cycle fatigue of elbows, focusing on the stress and strain variations. Strain gauge measurements are compared with finite element models. Upon calculation of local strain variation at the critical location, the number of cycles to fracture can be estimated.
Design and Analysis of Pressure Vessels, Heat Exchangers and Piping Components, 2004
ABSTRACT In this paper the response of internally pressurized pipe elbows under bending loads (in... more ABSTRACT In this paper the response of internally pressurized pipe elbows under bending loads (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the ultimate capacity of 90 deg elbows, focusing on the failure mode (buckling or flattening) and the maximum bending strength. The effects of moderate pressure levels on the ultimate moment and the failure mode are examined extensively.
Volume 4: Production Pipelines and Flowlines; Project Management; Facilities Integrity Management; Operations and Maintenance; Pipelining in Northern and Offshore Environments; Strain-Based Design; Standards and Regulations, 2014
Numerical simulations are conducted to define the bending deformation capacity of large-diameter ... more Numerical simulations are conducted to define the bending deformation capacity of large-diameter spiral-welded tubes, towards efficient strain-based design. Under bending loading, the principal failure mode of those tubes is local buckling (wrinkling) of the tube wall. Bending moment, curvature and ovalization are monitored through the numerical analysis, and comparison is conducted with available test data on two 42-inch-diameter tubes, with D/t ratio of 67 and 119, described in detail elsewhere. The analysis accounts for the actual material properties. Initial geometric imperfections (profile, thickness, ovalization) are obtained from the tested specimens. Furthermore, residual stresses are also considered in the analysis, as computed by a numerical simulation of the cold bending process. A parametric analysis is also conducted on the influence of material properties, geometric initial imperfections and residual stresses on local buckling of spiral-welded tubes. Finally, a compari...
Volume 3: Pipeline and Riser Technology; CFD and VIV, 2007
A 12.75 inch outer diameter single walled pipe bending test was executed and theoretical and FE a... more A 12.75 inch outer diameter single walled pipe bending test was executed and theoretical and FE analysis of this test was performed as preparation for 12.75 inch outer diameter TFP bending tests. The main objective of the TFP bending tests was to determine the initiation and degree of liner wrinkling occurring during the TFP spooling-on phase when simulating the reeling pipelay installation method. Due to lack of a definition of liner wrinkling initiation, the crossing of a certain threshold of the liner wrinkle height was defined as liner wrinkling initiation. The bending tests results indicated that (1) the extent of liner wrinkling decreased if TFP with a high mechanical bonding strength was used. (2) The presence of a circumferential weld in the highly bonded TFPs initiated higher liner wrinkles at lower curvatures than in case no circumferential weld was present. (3) The ERW outer pipe longitudinal weld did not result in higher liner wrinkles. API residual compressive stress te...
Proceedings of the 10th Pacific Structural Steel Conference (PSSC 2013), 2013
A European research project (RFCS) has started to provide economic and safe guidance for the desi... more 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 curvatureovalisation relationships are presented and compared with theoretical predictions.
Progress in Structural Engineering and Materials, 1997
This review highlights some of the recent developments in steel design and construction, and its ... more This review highlights some of the recent developments in steel design and construction, and its associated research. In recent decades, labour costs have increased considerably while material costs have remained constant. Therefore, there is a tendency to simplify the most labour-intensive parts of a steel structure: the connections, thus cutting labour costs. Simplifying the fabrication process is of considerably more importance than minimizing the use of materials. Research has been carried out to support the process of simplification. This review reports on some of the practical outcomes of this research. Special attention is given to fabrication and erection-friendly connections, the application of preloaded fasteners, and unstiffened moment connections (including base plates). Finally, in the conclusions, the review identifies future research needs.