Couplers

Static testing is carried out to verify the strength and performance of mechanical couplers under defined loading conditions. Testing is typically conducted in accordance with recognised standards including BS 8597 (CARES TA1-A, TA1-B), ISO 15630-1 (and ISO 6892-1), ISO 15835-2 and Sellafield Engineering Standard ES_0_3110_2 (CARES TA1-C). While most tests are conducted in tension, certain specifications also require compression testing, which we are fully equipped to perform.

We offer testing of couplers for bar diameters up to 50mm using universal test machines with capacities up to 1500kN. All equipment operates under UKAS accreditation to ISO 17025, with load cell calibration to ISO 7500-1 Class 1 or better or ASTM E4 to within 1%.

All testing is computer controlled, with modern digital systems capturing detailed data including full stress-strain curves for post-test analysis. Tensile testing is carried out using electronic extensometers through yield, with gauge lengths from 100mm to 800mm to accommodate a wide range of coupler types.

Dual averaging extensometry is used as standard to account for inherent misalignment in mechanical joints, with all extensometers calibrated to ISO 9513 Class 1 or better. Testing programmes typically include both the mechanical splice and a reference bar to allow direct comparison of performance.

Fatigue testing is carried out to assess the performance of mechanical couplers under repeated loading conditions, simulating long-term service behaviour.

In the UK, BS 8597 and CARES Technical Appendix TA1-A define fatigue requirements, while ISO 15835 specifies high cycle fatigue testing for couplers. We conduct testing to both standards using our range of computer controlled fatigue test systems, accommodating splice lengths of up to 1.3m.

Testing is carried out using either electro-magnetic resonance machines with load capacity up to 400kN, operating at frequencies between 80-140Hz, or a 270kN servo-hydraulic test machine for controlled testing at frequencies up to 30Hz.

Seismic testing evaluates the performance of mechanical couplers under cyclic loading conditions representative of earthquake activity, in accordance with ISO 15835.

Two levels of testing are defined. S1 simulates moderate seismic loading, applying twenty stress cycles between 0.5 times the yield stress in compression and 0.9 times the yield stress in tension, followed by tensile loading to failure. Displacement across the joint is continuously monitored throughout the test.

S2 simulates severe seismic loading. The joint is subjected to cyclic loading up to two times the yield strain, followed by repeated loading and unloading cycles, before being loaded to five times the yield strain and finally to failure. Displacement is measured throughout each phase of the test.

We have developed this testing capability as part of an ongoing research programme and offer seismic testing as a UKAS accredited service using an in-house procedure, refined to address limitations identified in the ISO method.