PSI - Issue 5

J. Morais et al. / Procedia Structural Integrity 5 (2017) 705–712 Morais J et al./ Structural Integrity Procedia 00 (2017) 000 – 000

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full-scaled damper. The main difference is that it has fewer and shorter wires, thus reducing the allowable load and displacement ranges without compromising the validation goal of the device.

Fig. 5. (left) virtual representation of the fully assembled prototype and (right) a photograph of the manufactured device.

The device prototype is externally similar to a hydraulic cylinder with a tubular body, two cylinder heads and a rod. Both heads have lateral extensions to serve as anchor points to each wire bundle. The other end of each wire bundle anchors on similar extensions on two internal pistons. The piston extensions pass through windows opened on the sides of the tubular body. Each bundle is arranged on perpendicular planes aligned with the longitudinal axis of the device to get a more compact arrangement for a given wire length. The internal pistons are connected to the rod with opposite twisting threads, so that by rotating the rod the initial pre-strain can be simultaneously applied to both wire bundles. One of the cylinder heads and the opposite end of the rod have a swivel head connector. Relative motion between these points stretches one of the wire bundles and shortens the other by the same amount, thus performing the intended damping purpose. The experimental validation process of the damper began with a series of cyclic traction/compression tests. At this stage no tests simulating seismic conditions were performed. The tests were conducted on a servohydraulic testing machine (SCHENCK HYDROPULS PSB – 500 kN) endowed with a displacement control (Fig. 6). A load cell and a displacement transducer were used to measure the external load and the applied displacement, respectively. The analog signals produced by the transducers, after have being amplified and filtered in a signal conditioning module, designed and built at LNEC, were measured and recorded using a NI 9215 data acquisition system. 3. Experimental tests

Fig. 6. (left) damper prototype ready to be tested, (right) prototype mounted on the testing machine.