Marine Structures LaboratoryTechnical specifications and testing facilities

Main installations

Strong Floor: 7 x 11 square meters, weigth 200 tons, maximum point load 2000 kN. Adjacent floor space approximately 500 square meters for smaller loads.

Hydraulic power: Primary ring main 500 l/min, second-ary ring main 50 l/min, 240 bar.

Acturators: A range of servohydraulic acturators for static and dynamic testing, from 100 kN load capacity to a maximum load/stroke of 4000 kN/1000 mm.

Control system: Several computerized systems for multi-acturator control, fatigue load simulation, data logging with on-line reduction and analysis.

Rig system: Modular frame system which can be built to accomodate specimens and structural models with a wide range of shapes and sizes, under unaxial or multiaxial loading, and with load capacities up to 4000 kN.

Materials and construction technology - fields of research

Fatigue testing: High performance dynamic actura-tors with load capacities up to 2000 kN with hydraulic grips.

A wide range of load programs, in-cluding randomized load sequences with variable or constant rms levels and variable signal bandwidth.

l environmental chambers for low temprature testing

l seawater testing with temprature control and cathodic protection

l testing of large structural mod-els with automated crack growth monitoring

Steel rope testing: Static and dynamic testing of heavy steel rope, with axial loading and specimen lengths of up to 7 meters.

The main activities in the laboratory are the testing of structures, structural components and materials. Typical problems involve fatigue testing, ultimate strength and collapse testing, testing for serviceability, and advanced materials testing. Experimental work is often combined with analytical or numerical analysis.

A wide range of structural analysis programs are available for linear and non-linear static and dynamic analyses. These include special programs for fatigue and fracture mechanics analysis, and the collapse behaviour of intact and damaged structures.

The Marine Structures Laboratory is operated by MARINTEK, Department of Structural Engineering in cooperation with Norwegian University of Science and Technology, Department of Marine Structures.

Fracture testing of tubular member, with fatigue crack, 4000 kN load capacity.

Fatigue testing of 75 mm diameter steel rope.

Large scale welded girders, length 8 m, plate thick- ness 60 mm, fatigue tested with variable amplitude loading, two actuators in simulatneous computer control.

Collapse of tubular frame, simulating collision load-ing on jacket structure.

Development of fatigue crack growth in welded specimen. Beachmarks produced by block loading.

Marine Structures LaboratoryTechnical specifications and testing facilities

Collapse testing: Maximum load capacity 4000 kN, stroke 1000 mm in closed loop con-trol.

Large models can be tested under controlled conditions of multiaxial loading to obtain the buckling and collapse characteristics of intact and damaged structures.

Fracture testing: Realistic models of wide plates, pipelines, risers, tether elements and tubular joints can be tested to fracture at tempratures down to -50 degrees.

Facility for testing of flexible pipe

Rig for full scale dynamic testing of flexible pipe

Configuration: Horizontal, in a test frame on the laboratory floor.

Pipe model: Length 15 m flange-to-flange.

Loading: Two independent modes of loading; tensile axial loading at one end, bending loading in opposite end.l Bending load capacity: 1 MNm

dynamic, 30 degrees tilt static, ± 30 degrees dynamic.

l Axial load capacity: 1.5 MN dy-namic, 500 mm stroke dynamic.

Load signal: State-of-art digital con-trol electronics, computerised load generation. The system accepts any sequence of peaks and troughs, e.g. generated by a block program to be specified by Client.

Pressure: Internal pressure of pipe up to 600 bar.

Environment: Oil or water filled pipe model, ambient room temperature.

Instrumentation for measurement of:l Number of cycles l Internal temperature of pipe l Temperature in outer armour layer l Ambient temperature l Internal pressure l Applied tension l Rocking angle l Strain in outer armour layer

Facility for:l Conditioning of pipe at 125 oC

internal temperature, 500 bar pres-sure.

l Leak testing at 110 % of design pressure, ambient temperature.

Condition monitoring: Condition monitoring of pipe during testing may be performed by Robit, using state-of-art methods:l Eddy current inspection of outer

tensile armour layers l X-ray inspection of metallic com-

ponents l Acoustic emission for detection

of development of fatigue or wear modes of failure

The test rig complies with API re-quirements for full scale testing of flexible pipes.

Thermal Cycling Testing of Flexible Risers

MARINTEK has established a facility for testing of flexible pipes subjected to thermal cycling simulating shut-downs. By calibration to data inferred from field failures, a test procedure has been established in which the conditions of failed pipes are simulat-ed. The temperature may be cycled by programmed profiles from -20 to 1300C. There are 10 slots for simul-taneous testing of pipe models.

Using numerical simulation of the transient thermal response in flexible pipes subjected to various scenarios of shut-down (described below) test procedures are developed by which a wide range of field conditions may be simulated. More than 20 pipes have been/are being tested, from all three major suppliers of flexible pipe.

The test procedures which have been developed are in the process of being written into API guidelines.

Small scale test facility for flexible risers:

Fully equipped structural laboratory for tests on flexible pipe components:

l Small scale tests of tensile ar-mour, effects of fretting contact, wear, sea water etc., assessment of SN design curve. Dedicated test facility for wear testing of compos-ite tensile armour

l Small scale tests of hoop stress profiles, component tests, fatigue and wear

l Fatigue and ultimate strength tests of armour components anchored in epoxy

l Wear of anti-friction layers, effect of elevated temperature

Design analysis:

MARINTEK/SINTEF has for more than a decade been heavily engaged in development of advanced software for analysis of risers, riser systems and flowlines. The following is a short list of computer codes which are available:

l RIFLEX: Non-linear FE code for 3-D global analysis of pipe, static

Instrumentation of jacket model for ultimate strength and collapse test.

Fatigue testing of tubular T-joint, out-of-plane bending. Chord diameter 500 mm (410 kB).

Hot spot region in a tubular joint, instrumented for strain measurements and crack growth monitoring by th potential drop method.

and dynamic analysis, frequency and time domain analysis, as-sessment of test parameters for simulation of operating conditions.

l CAFLEX: Pipe-wall analysis with assumed axisymmetric conditions.

l BFLEX: Stress analysis of tensile and hoop armour with arbitrary curvature gradient along pipe, fatigue analysis.

l General FEM: Component analy-sis, e.g. hoop stress profiles, end-fitting details, etc.

Thermal analysis of flexible risers

A computer code has been devel-oped for calculation of transient temperature fields in a pipe with end fitting during temperature cycles. The computational model is based on the following elements:

l OLGA (1989) is a computer code developed for analysis of two-phase transport of oil and gas through pipelines. The program calculates in time domain the separation of oil and gas, and the thermal conditions inside a pipe due to pressure release.

l FAHTS (1995) - Fire and Heat Transfer Simulations in Framed Structures is a finite element code for analysis of heat transfer in time

domain, taking into account heat transport by convection, conduct-ance and radiation. Three-dimen-sional fields and transients can be calculated assuming rotational symmetry.

l USFOS (1988) - Ultimate Strength Analysis of Framed Offshore Structures is a non-linear finite ele-ment code. Geometric and mate-rial non-linearities are accounted for.

The program suite is used for cal-culation of transient and stationary temperature distributions in a flexible riser system, and thermal forces in the different layers of the pipe includ-ing effects of end termination, bend stiffener and external environment. The program has been validated against realistic laboratory tests.

URL: http://www.marintek.sintef.no

Contact persons:MARINTEK: Oddvar.Eide@marintek.sintef.noNTNU: stig.berge@ntnu.no

Norwegian Marine Technology Research InstituteAddress: POB 4125 Valentinlyst, NO-7450 Trondheim,, NorwayPhone: +47 7359 5500 Fax: +47 7359 5776E-mail: marintek@marintek.sintef.no

The Marine Structures Laboratory is situated at the Marine Technology Centre in Trondheim, Norway