Ilaria Ricci

Shaking Table Test Design to Evaluate Earthquake Capacity of a 3-Storey Building Specimen Composed of Cast-In-Situ Concrete Walls

This paper presents the work developed to design a shaking-table test at the EUCENTRE Lab, for the evaluation of the maximum capacity of a 3-storey building subjected to earthquake loading. The structural system of the building is composed of cast-in-situ sandwich squat reinforced concrete walls using polystyrene as a support for the concrete. The purpose of this test is to verify the dynamic behavior of this structural typology under earthquake acceleration. Previous to the shakeing-table tests carried out at the EUCENTRE Lab, extensive analytical and numerical research was developed on a set of models of the building under seismic input. Also, experimental tests were performed on single r.c. panels subjected to pseudo-static cyclic loading. The structural specimen was a structural system composed of cast-in-situ squat sandwich concrete walls characterized by 5.50 × 4.10 m in plan and 8.25 m in height. The input for the simulation was the Montenegro earthquake of April 1979. The construction of this building was developed outside the laboratory; it was lifted and pulled inside using hydraulic jacks and a roller system. A bracing system was developed to assure the integrity of the structure during the transportation process. This chapter presents some preliminary results of the shaking-table tests.

A special solution for lateral-resisting systems capable of multiple seismic performances

This paper aims at presenting an innovative approach for an optimised/full-controlled seismic design of structures which combines recent contributions in the field of earthquake engineering and overcomes the traditional design approach leading to the identification of the characteristics of the lateral-resisting system capable of satisfying multiple seismic performance objectives. In this respect, it is fundamental the total conceptual separation between the structural systems resisting to vertical and horizontal loads. With reference to both (1) a braced pendular frame structure and (2) a shear-type frame system coupled with a lateral-resisting element (such as a reinforced concrete core or a bracing system), the approach here presented identifies the characteristics (strength, stiffness, ductility, energy-absorption) of the system resisting to horizontal loads which enables to satisfy prescribed seismic performance objectives. This is achieved through the identification of an objectives curve, in the Force-Displacement diagram, of the mechanical characteristics of the structure. The lateral-resisting system is obtained by means of (1) special braces in the case of the braced pendular frame structure and (2) special connection elements in the case of the shear-type system coupled with a lateral-resisting element.

A case study of a building in L'Aquila, Italy for evaluating the effects of masonry infills on the seismic behavior of r.c. frame structures

It is known that the seismic response of a structural system is highly influenced, in addition to the earthquake input, by the dynamic characteristics of the system itself. It has been observed during the L’Aquila earthquake that some buildings have shown unexpected good performances. The aim of this paper is to understand why these structures, designed for accelerations lower than those recorded during the L’Aquila’s earthquake, have shown performances higher than the design ones. The attention is focused on a real case study of a reinforced concrete frame building structure located in L’Aquila. The paper investigates the role of the masonry infills which, before reaching their ultimate capacity, allows to avoid significant structural damage and excursion in the inelastic range. The seismic behaviour of the examined building is studied within Performance Based Seismic Design approach. In particular, by imposing the performance objectives, an “objectives curve”, in the Force-Displacement diagram related to the mechanical characteristics of the structure, is obtained. Both the contribution of the columns and the masonry infills are considered in the evaluation of the Force-Displacement diagram. Then, time-history analyses are performed by applying to the building under study recorded ground motions of the L’Aquila earthquake. A non linear model of the structure, and in particular of the masonry infill, is implemented for the analyses. The examined response quantities are bending moments and chord rotations of columns and beams as well as forces and deformations of masonry infills. For comparison purposes two cases are studied: the first is the bare frame, the second is the infilled frame. These analyses allow to identify the effects of the masonry infills on the response of the case study.

Correlations Between the Experimental Results of Pseudo-Static Tests with Cyclic Horizontal Load on Concrete/Polystyrene Sandwich Bearing Panels and their analytical counterparts

In recent years, the seismic behavior of reinforced concrete bearing squat walls structures has been the object of several research works. This paper presents a summary of the results obtained in a wide experimental/analytical/numerical correlation campaign carried out as a joint effort between the University of Bologna and the EUCENTRE labs in Pavia. This effort was devoted at the assessment of the seismic performances of structures composed of (lightly reinforced) concrete/polystyrene sandwich bearing squat walls. In this paper: (1) the results of a number of pseudo-static tests with cyclic horizontal load have been briefly recalled; (2) extensive analytical developments have been carried out to evaluate the mechanical characteristics and the seismic behavior of lightly reinforced concrete panels; (3) a comparison between the analytical and the experimental results has been performed. The comparison shows a good agreement between the experimental results and their analytical counterparts.