Marine Structures Laboratory

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, Div. of Structural Engineering in cooperation with Norwegian University of Science and Technology (Marine Structures Group).  The laboratory is certified to ISO 9001.

Stucture testing
Pipe testing

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, secondary ring main 50 l/min, 240 bar.

Acturators:

A range of servohydraulic acturators for static and dynamic testing, from 25 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.

Facility for testing of flexible pipes and umbilicals

Illustrasjonsbilde/FOTOThree Test Rigs

There are three test rigs for full scale dynamic testing of flexible pipes and umbilicals.

  • 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.
    1. Bending load capacity: 1 MNm dynamic, 30 degrees tilt static, ± 30 degrees dynamic.
    2. Axial load capacity: 3.0 MN dynamic, 500 mm stroke dynamic.
  • Load signal: State-of-art digital control 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 700 bar.
  • Environment: Oil or water filled pipe model, ambient room temperature.

Instrumentation for measurement of

  • Number of cycles
  • Internal temperature of pipe
  • Temperature in outer armour layer
  • Ambient temperature
  • Internal pressure
  • Applied tension
  • Rocking angle
  • Strain in armour layers and steel tubes by fibreoptics or conventional strain gauges

Facility for

  • Conditioning of pipe at 125 oC internal temperature, 500 bar pressure.
  • Leak testing at 110 % of design pressure, ambient temperature.

Condition monitoring

Condition monitoring of pipe during testing may be performed, using state-of-art methods:

  • Eddy current inspection of outer tensile armour layers
  • X-ray inspection of metallic components
  • Acoustic emission for detection of development of fatigue or wear modes of failure
  • The test rig complies with API requirements for full scale testing of flexible pipes.
  • Strain gauge monitoring

Small scale test facility for flexible risers

  • Fully equipped structural laboratory for tests on flexible pipe components:
  • Small scale tests of tensile armour, effects of fretting contact, wear, sea water with gas mixtures (CO2, H2S, N2),
  • Assessment of SN design curve.
  • Dedicated test facility for wear testing of composite tensile armour
  • Small scale tests of hoop stress profiles, component tests, fatigue and wear
  • Fatigue and ultimate strength tests of armour components anchored in epoxy
  • Wear of anti-friction layers, effect of elevated temperature

Design analysis

The following is a short list of computer codes used:

  • RIFLEX: Non-linear FE code for 3-D global analysis of pipe, static and dynamic analysis, frequency and time domain analysis, assessment of test parameters for simulation of operating conditions.
  • CAFLEX: Pipe-wall analysis with assumed axisymmetric conditions.
  • BFLEX: Stress analysis of tensile and hoop armour with arbitrary curvature gradient along pipe, fatigue analysis.
  • UFLEX: 2D and 3D stress analysis of umbilicals
  • USAP: 3D stress analysis of umbilicals
  • General FEM: Component analysis, e.g. hoop stress profiles, end-fitting details, etc.

Test rig for creep and fatigue testing of electrical conductors

  • Dynamic testing at variable tension, curvature, and temperature
  • Tensions from 0-25 kN
  • Curvatures from 0.5 - 10 m -1
  • Temperature cycling -20°C/+ 90°C

 

Materials and construction technology - fields of research

Fatigue testing:

High performance dynamic acturators with load capacities up to 2000 kN with hydraulic grips. A wide range of load programs, including randomized load sequences with variable or constant rms levels and variable signal bandwidth.

  • environmental chambers for low temprature testing
  • seawater testing with temprature control and cathodic protection
  • testing of large structural models 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.

Collapse testing:

Maximum load capacity 4000 kN, stroke 1000 mm in closed loop control. 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.