Quasi Static Testing Systems

Computer controlled servo-hydraulic multi-actuator testing systems allow for fatigue testing, quasi static testing including Pseudo-Dynamic Testing (PST).  In PST a large scale test structure is attached to a strong floor, strong wall, and/or reaction frame and excited slowly at low frequencies with multiple actuators.  A PC-based digital controller measures and controls the force and displacement of each actuator.  Fatigue and basic quasi static testing use open loop control to drive the actuators with a pre-programmed time history or block cycle.

During PST the controller internally computes the theoretical inertial forces that would exist in the true dynamic event such as an earthquake.  Hence, PDT can slowly expose a structure to the forces, strains, and displacements that would actually occur during a dynamic event.  The advantage over a shake table is the ability to test much larger structures, without requiring large and more expensive hydraulic power systems, shake tables, and actuators with high flow servo valves.

Components of a typical ANCO quasi static testing system include:

• Structures laboratory with strong floor and walls with attachment inserts.
• Multiple actuators with static force rating of 100 kN -1000 kN.  Stroke from +/- 100 mm to +/- 400 mm.  Peak velocity of 1 cm/s -10 cm/s.
• Vane type bridge load cells with 150% force measurement overload capacity.
• Magnetostrictive coaxial displacement transducers.
• Zero maintenance PTFE swivels or steel-on-steel lubricated swivels on base and piston, with client specified bolt pattern.  Swivels have +/- 100 degree/+/-8 degree capacity.
• Hydraulic power supplies rated for fatigue operation and 15-180 GPM.
• Hydraulic power supply with capacity of 30-300 GPM (110-1100 L/min) at 3,000 psi (21 MPa).
• Hydraulic hoses to place the actuators up to 30 m from the strong wall or strong floor local manifolds (with quick release connectors).
• 5-15 GPM two-stage servo valves (option for larger valves).
• Frequency response 0-20 Hz.
• PC-based digital control system (ANIPC and TRIDENT) with up to 8 actuators control and acquire up to 128 channels of data.
• Additional strain or displacement measurement transducers, as required.