dr. ir. Maarten Kruijer


PhD Project:

Modelling the time dependent behaviour of steel Reinforced Thermoplastic Pipes.

Start / End:

1st December 2001 to 11th may 2006


The PhD study was performed within the framework of an EUREKA supported research project: “high pressure reinforced pipes” (E!2601). This research project was supported by and carried out at the Research and Development department of Pipelife Nederland B.V.

Other members in the EUREKA project were:

Twente University (Netherlands)

Bekaert N.V. (Belgium)

Seaflex S.A. (Norway)

Gurit Suprem (Switserland)


Steel Reinforced Thermoplastic Pipe (s-RTP) is a new class of pipe that offers the benefits of Polyethylene (PE) at pressures up to 150 bar (5 inch inner diameter), whereas PE is limited to pressures below 16 bar. Such advantages include corrosion resistance, continuous lengths, damage tolerance and coilability. A mathematical model is developed combining the linear elastic behaviour of the steel cords and the non-linear viscoelastic behaviour of the HDPE in a multilayer pipe model based on generalised plane strain

conditions. By this model the time dependent deformation and failure behaviour can be described for each particular pipe geometry and no long term (> 1000 hours) testing on prototype pipes is necessary anymore in the development phase. The thesis concludes with a design strategy, based on the prepared model which can be used by field engineers to practically design sRTPs.

Related research:

W. Kruis, Pull-out in steel Reinforced Thermoplastic Pipes, master thesis report, Twente University, 2005. Experimental research, analysing the capabilities of stress transfer for a particular type of steel cord embedded in a HDPE plate.

M.P.Kruijer, Analysis of the mechanical behaviour of a Reinforced Thermoplastic Pipe, master thesis report, Twente University, 2001. Development of a mathematical model which can be used to design and engineer aramid reinforced thermoplastic pipes.


M.P. Kruijer, L.L. Warnet and R. Akkerman, Modelling of the viscoelastic behaviour of steel reinforced thermoplastic pipes, Composites Part A: Applied Science and Manufacturing, Vol.37, 2006, p.356-367.

M.P. Kruijer, L.L. Warnet and R. Akkerman, Analysis of the mechanical properties of a reinforced thermoplastic pipe (RTP), Composites Part A: Applied Science and Manufacturing, Vol.36, 2005, p. 291-300.

M.P. Kruijer, L.L. Warnet and R. Akkerman, Modelling the mechanical behaviour of steel compact cords, International Journal of Solids and Structures, To be submitted.

M. Kruijer, Modelling the time-dependent mechanical behaviour of steel reinforced thermoplastics pipes, PhD thesis University of Twente, 2006, ISBN 90‑365‑2341‑0.


As from January 1st 2006 Maarten Kruijer joined Pipelife Nederland B.V. Nowadays, this company makes the steel reinforced thermoplastic pipe commercially available under the name SoluforceÒ Heavy. Questions, remarks? Please send me an e-mail.