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Development of the modified clothoidal (MCL) shape of composite dowels against the background of fatigue and technological issues

Wojciech Lorenc
Wojciech Lorenc
 and 
Maciej Kożuch
Maciej Kożuch
   | Apr 08, 2024
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Article Category: Original Study
Published Online: Apr 08, 2024
Page range: -
Received: Sep 28, 2023
Accepted: Mar 01, 2024
DOI: https://doi.org/10.2478/sgem-2024-0005
Keywords
© 2024 Wojciech Lorenc et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1:

Dimensions accepted in further analysis of the PZ shape.
Dimensions accepted in further analysis of the PZ shape.

Figure 2:

Results of push-out tests conducted by UBWM [7]: force per dowel versus relative slip for the SA, PZ, and CL shapes (the horizontal axis shows the slip displacement measured in the tests).
Results of push-out tests conducted by UBWM [7]: force per dowel versus relative slip for the SA, PZ, and CL shapes (the horizontal axis shows the slip displacement measured in the tests).

Figure 3:

Cutting technology for production of test specimens for project [7]: a) and b) single cutting line for the PZ and SA shapes and c) two cutting lines for the CL shape.
Cutting technology for production of test specimens for project [7]: a) and b) single cutting line for the PZ and SA shapes and c) two cutting lines for the CL shape.

Figure 4:

The idea of the new push-out-test (NPOT) specimen proposed by the author to be used for cyclic tests [7] (2 million cycles).
The idea of the new push-out-test (NPOT) specimen proposed by the author to be used for cyclic tests [7] (2 million cycles).

Figure 5:

The test stand for NPOT.
The test stand for NPOT.

Figure 6:

The sensor system and bearings for NPOT.
The sensor system and bearings for NPOT.

Figure 7:

Numerical models of the NPOT specimen (only the steel part of the composite model is extruded for visualization of the stress layout): models with displacement visualization in the direction of the force (a, b, and c) and the steel part of the model and the principal stresses (d, e and f): u1 stands for displacement according to the direction of acting force and σ1 stands for maximum principal stress (tension).
Numerical models of the NPOT specimen (only the steel part of the composite model is extruded for visualization of the stress layout): models with displacement visualization in the direction of the force (a, b, and c) and the steel part of the model and the principal stresses (d, e and f): u1 stands for displacement according to the direction of acting force and σ1 stands for maximum principal stress (tension).

Figure 8:

Results for the NPOT-SA1 element (CL shape drawing is for reference only): changes in displacement of the measuring points together with the number of load cycles (no teeth damage; however, there was a fatigue crack in the weld of the steel element transmitting the force to the webs).
Results for the NPOT-SA1 element (CL shape drawing is for reference only): changes in displacement of the measuring points together with the number of load cycles (no teeth damage; however, there was a fatigue crack in the weld of the steel element transmitting the force to the webs).

Figure 9:

Results for the NPOT-PZ2 element (CL shape drawing is for reference only): changes in displacement of the measuring points with the number of load cycles (steel tooth crack as predicted).
Results for the NPOT-PZ2 element (CL shape drawing is for reference only): changes in displacement of the measuring points with the number of load cycles (steel tooth crack as predicted).

Figure 10:

Documentation of fatigue cracks in the NPOT-PZ2 specimen tested in of the PreCo-Beam project [7]: a–f) view after cutting the concrete part, g) general view of the crack, h) beginning of the crack, and i) end of the crack
Documentation of fatigue cracks in the NPOT-PZ2 specimen tested in of the PreCo-Beam project [7]: a–f) view after cutting the concrete part, g) general view of the crack, h) beginning of the crack, and i) end of the crack

Figure 11:

The original concept of dimensionless resistance of steel dowels regarding local and global effects [5,6] (Fig. 13d in [6]): fatigue coefficients for tension stress for PZ shape (at the left; to be compared with Fig. 20 and [22] for the clothoidal shape) and general prediction for complete stress set (at the right).
The original concept of dimensionless resistance of steel dowels regarding local and global effects [5,6] (Fig. 13d in [6]): fatigue coefficients for tension stress for PZ shape (at the left; to be compared with Fig. 20 and [22] for the clothoidal shape) and general prediction for complete stress set (at the right).

Figure 12:

Strain gauges on NPOT specimens with CL shapes for purposes of [7].
Strain gauges on NPOT specimens with CL shapes for purposes of [7].

Figure 13:

Principal (maximum) stress layout in the tooth for the NPOT model according to FE simulations.
Principal (maximum) stress layout in the tooth for the NPOT model according to FE simulations.

Figure 14:

Summary of characteristics of the basic shapes highlighting the problems with the idea of a new cutting line and the basis standing behind this idea (original drawing of steel parts of NPOT specimens for discussions with partners of the PreCo-Beam [7] project: only the SA and PZ shapes were used in bridges before construction of the “Wierna Rzeka” Bridge in Poland [62]).
Summary of characteristics of the basic shapes highlighting the problems with the idea of a new cutting line and the basis standing behind this idea (original drawing of steel parts of NPOT specimens for discussions with partners of the PreCo-Beam [7] project: only the SA and PZ shapes were used in bridges before construction of the “Wierna Rzeka” Bridge in Poland [62]).

Figure 15:

Production technology of the clothoidal symmetrical shape without problems with overheating of the steel (the process results in a shape with a more extensive upper part of the steel dowel compared to the initial CL shape): the idea of cutting line (at the top) and the first-cut sheet fragments delivered by the contractor for acceptance of the technology (pictures taken in Wrocław on 10.17.2008)
Production technology of the clothoidal symmetrical shape without problems with overheating of the steel (the process results in a shape with a more extensive upper part of the steel dowel compared to the initial CL shape): the idea of cutting line (at the top) and the first-cut sheet fragments delivered by the contractor for acceptance of the technology (pictures taken in Wrocław on 10.17.2008)

Figure 16:

Application of the new cutting line for the production of beams for the “Wierna Rzeka” Bridge with a new shape with dimensions of 115/250 mm (the left picture shows the cutting line by ArcelorMittal, where this procedure was implemented later on).
Application of the new cutting line for the production of beams for the “Wierna Rzeka” Bridge with a new shape with dimensions of 115/250 mm (the left picture shows the cutting line by ArcelorMittal, where this procedure was implemented later on).

Figure 17:

Drawings of composite spans of the innovative “Wierna Rzeka” Bridge in Poland, the first implementation of the clothoidal shape in structural engineering and the first railway bridge using composite dowels (no welding of T-sections).
Drawings of composite spans of the innovative “Wierna Rzeka” Bridge in Poland, the first implementation of the clothoidal shape in structural engineering and the first railway bridge using composite dowels (no welding of T-sections).

Figure 18:

Cutting specification for the first implementation of the modified clothoidal shape for the “Wierna Rzeka” Bridge (cutting done in Poland): a) geometry and specification of the cutting process (screen view during cutting), b) cutting progress, c) stops during cutting, d) deformation of the separated T-section due to eigenstresses, e) the separation process, and f) beams after separation with the final shape of the steel dowels.
Cutting specification for the first implementation of the modified clothoidal shape for the “Wierna Rzeka” Bridge (cutting done in Poland): a) geometry and specification of the cutting process (screen view during cutting), b) cutting progress, c) stops during cutting, d) deformation of the separated T-section due to eigenstresses, e) the separation process, and f) beams after separation with the final shape of the steel dowels.

Figure 19:

Results of the numerical simulations of the MCL 115/250 shape (the shape after optimization of the ratio according to the procedure presented in Fig. 30 in [57]) by Abaqus software.
Results of the numerical simulations of the MCL 115/250 shape (the shape after optimization of the ratio according to the procedure presented in Fig. 30 in [57]) by Abaqus software.

Figure 20:

Dimensionless stress concentration factors (according to [5,6]) for the MCL 115/250 shape and the PZ 300/100 shape.
Dimensionless stress concentration factors (according to [5,6]) for the MCL 115/250 shape and the PZ 300/100 shape.

Figure 21:

Adjustment of the cutting line by ArcelorMittal (the left picture by ArcelorMittal): a) first version of the line with wastes to remove, b) adjustment of the line results in the wastes falling down during cutting because the line has a realistic thickness (however, no overheating occurs).
Adjustment of the cutting line by ArcelorMittal (the left picture by ArcelorMittal): a) first version of the line with wastes to remove, b) adjustment of the line results in the wastes falling down during cutting because the line has a realistic thickness (however, no overheating occurs).

Figure 22:

Different shapes and technologies of production of steel dowels with the clothoidal shape: a and b) different shapes of the “nose” of steel dowels by different producers fabricated in Poland out of plates by oxy-cutting, c) small dowels fabricated in Luxembourg by plasma cutting, d) elements of the PE4 bridge design by the author in Poland [12] fabricated in Luxembourg by oxy-cutting and plasma cutting, and e) steel elements of the PE4 bridge at the construction site (a large number of elements were produced with the MCL 115/250 shape).
Different shapes and technologies of production of steel dowels with the clothoidal shape: a and b) different shapes of the “nose” of steel dowels by different producers fabricated in Poland out of plates by oxy-cutting, c) small dowels fabricated in Luxembourg by plasma cutting, d) elements of the PE4 bridge design by the author in Poland [12] fabricated in Luxembourg by oxy-cutting and plasma cutting, and e) steel elements of the PE4 bridge at the construction site (a large number of elements were produced with the MCL 115/250 shape).

Figure 23:

Tolerances for production of steel connectors using the geometry of the modified clothoidal shape of connector.
Tolerances for production of steel connectors using the geometry of the modified clothoidal shape of connector.

Figure 24:

“Wierna Rzeka” railway bridge in Poland, the first implementation of the clothoidal shape of dowels
“Wierna Rzeka” railway bridge in Poland, the first implementation of the clothoidal shape of dowels

Figure 25:

Implementation of composite dowels in innovative composite bridges in Poland: a) and b) implementation in beams – bridge in Elbląg (presented in [41]) and c) implementation in arches – a new solution as part of a network arch bridge using composite dowels [63].
Implementation of composite dowels in innovative composite bridges in Poland: a) and b) implementation in beams – bridge in Elbląg (presented in [41]) and c) implementation in arches – a new solution as part of a network arch bridge using composite dowels [63].

Figure 26:

Nominal geometry of the modified clothoidal shape of a single connector MCL 100/250 according to [16] given as a function of the spacing of connectors ex.
Nominal geometry of the modified clothoidal shape of a single connector MCL 100/250 according to [16] given as a function of the spacing of connectors ex.

Main stress values (MPa) in the NPOT models estimated using FEA for coarse mesh density – the stress level is given at the minimum (σP = 120 kN) and maximum (σP = 280 kN) load level and their difference (ΔσP = 160 kN).

σP = 120 kN ΔσP = 160 kN σP = 280 kN
CL 132.0 176.0 308.0
SA 134.6 179.4 314.0
PZ 157.6 210.2 367.8
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