Design Provisions for An Easy Intervention in the Future Life of a Structure. The Case of the Post- Byzantine Timber-roofed Basilicas of Troodos Area in Cyprus

Background: This article deals with the timber- roofed basilicas of Troodos which were built from the mid-15th to the late-19th century AD. The most impressive constructional feature of these basilicas is the existence of two constructionally distinctive, but cooperating, parts of the roof. The basilicas’ construction system is mainly characterized by the ability to confront successfully the dynamic loads of an earthquake. Objective: This study investigates design provisions that can make easier any future intervention and retrofitting. Methods It is suggested that the design concept of these basilicas incorporated, among other objectives, a remarkable provision for an easy repair intervention and retrofitting, at a later stage during their life. The timber- roofed basilicas of Troodos demonstrate a cleverly designed structure, where the co-operation between the roof and masonry plays an important role in their anti-seismic design. Results and Conclusion: The timber-roofed basilicas of Troodos present a remarkable design provision that made intervention an easy task, at any stage of their future life. This particular design concept seems to be valuable even today and can be easily adopted when designing modern contemporary structures with a long-term life objective.

Vibration Attenuation by a Combination of a Piezoelectric Stack and a Permanent Magnet

The present work proposes a non-contact vibration attenuator made up of a permanent magnet mounted on a piezoelectric stack. Two such actuators are made to work simultaneously in a 'twin-actuator' configuration. It is conceived that a controlled change in the gap between the actuator and the structure is capable of attenuation of vibration of the structure. This appropriate change in gap is achieved by controlled motion of the piezoelectric stacks. It is shown that the actuator works as an active damper when the extension and contraction of the actuators are made proportional to the velocity of the beam. The resolution of extension of a piezoelectric stack is in the order of nanometers. Thus in the proposed actuator the force of actuation can be applied with great precision. This actuator is also attractive for its simple constructional feature.