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:
Three-actuator masonry wall system with PDT balancing of vertical loading.
Photo courtesy of Drexel University.
3 axes fatigue loading frame for Drexel University, Pennsylvania, USA.