Reinforcement of the 18th Century Buttresses of Maniace Castle: Design and Execution

ABSTRACT

Maniace Castle, built on Ortygia island in Siracusa (Italy) in the first half of the 13th century and hosting a magnificent hypostyle hall (the Salone), a square area covered by 25 cross vaults supported by columns, was severely damaged by the 1693 earthquake and the explosion of the ammunition dump in 1704. The buttresses, built immediately afterward to counteract the thrust of the 10 surviving vaults, did not guarantee adequate seismic safety so that a metal scaffolding was installed in 2001 to prevent an overturning mechanism. This article discusses the design and execution of an external pre-stressing steel system to increase existing buttress strength and the seismic capacity of the Salone, starting with historical and constructional analyses and dealing with both analytical and technical aspects. The monitoring system installed to detect structural response during and after the working execution is shown, along with some of the data acquired so far.     

ANALYTICAL MODELLING OF THE SEISMIC BEHAVIOUR OF PRECAST CONCRETE FRAMES DESIGNED WITH DUCTILE CONNECTIONS

Pure precast beam-column systems incorporate unbonded reinforced at the critical sections, causing strain incompatibility between steel and concrete. As a result, classical section analysis method, well know for characterising monolithic concrete members, cannot be directly applicable to these systems. This paper provides a section analysis method suitable for precast members, incorporating, through an analogy with equivalent cast-in-place solution named “monolithic beam analogy”, an additional condition on the member global displacement. The proposed method was first validated with the experimental data from tests on beam-column Hybrid subassemblages. Using appropriate hysteresis rules and the response envelopes defined by the section analysis method, a prediction of the behaviour of the PRESSS test building was carried out. Satisfactory agreements obtained between the analytical and experimental results confirm the validity of the suggested methodology. Derivation of the method and experimental validation are herein presented.     

CONCEPT AND DEVELOPMENT OF HYBRID SOLUTIONS FOR SEISMIC RESISTANT BRIDGE SYSTEMS

The development of alternative solutions for precast concrete buildings based on jointed ductile connections has introduced innovative concepts in the design of lateral-load resisting frame and wall systems. Particularly efficient is the hybrid system, where precast elements are connected via post-tensioning techniques and self-centring and energy dissipating properties are adequately combined to achieve the target maximum displacement with negligible residual displacements. In this contribution, the concept of hybrid system is extended to bridges as a viable and efficient solution for an improved seismic performance when compared with monolithic counterparts. Critical discussion on the cyclic behaviour of hybrid systems, highlighting the most significant parameters governing the response, is carried out.

The concept of a flexible seismic design (displacement-based) of hybrid bridge piers and systems is proposed and its reliability confirmed by quasi-static cyclic (push-pull) and nonlinear time-history analyses based on lumped plasticity numerical models.