Simone Peloso

FRP SEISMIC RETROFIT OF RC SQUARE HOLLOW SECTION BRIDGE PIERS

The research work presented in this paper deals with the seismic assessment of hol-low bridge piers strengthened with fibre-reinforced polymer (FRP). The scope of the strengthening is to overcome some common deficiencies derived from the use of non-seismic design rules, which can often lead to inadequate response when operating in cyclic loading. The strengthening design was studied by means of a parametric analysis considering different fibres and geometrical parameters applied to typical case studies. Quasi-static cyclic tests were performed on five 1:4 scaled piers designed according to old non-seismic Italian codes and strengthened according to the previous analytical study. Efficiency of FRP strengthening was evaluated by comparing the experimental results with those obtained in a previous experimental research performed on similar non-strengthened specimens. Base shear versus lateral deflection curves, dissipated en-ergy and collapse mechanisms comparison shows the achievable effectiveness once the debonding risk has been overcome.

Dynamic testing of a four-storey building with reinforced concrete and unreinforced masonry walls: Prediction, test results and data set

AbstractThis paper presents the results of a series of shake-table tests on a half-scale, four-storey building with reinforced concrete and unreinforced masonry walls. Due to the lack of reference tests, the seismic behaviour of such mixed structures is poorly understood. The test unit was subjected to several runs of increasing intensity yielding performance states between minor damage and near collapse. Before the test, the expected peak table accelerations leading to different limit states were estimated using the capacity spectrum method, and the predicted values corresponded rather well to actual sustained accelerations. Next to these analyses, the paper describes the test unit, instrumentation and input motion, and comments on the response of the mixed structure in terms of damage evolution and global response quantities, such as force–displacement response and drift and acceleration profiles. The raw and post-processed data sets are made publically available, and all relevant information with regard to data organisation and post-processing procedure is described in an appendix to this paper. The test serves therefore as a benchmark for the validation of numerical models of such mixed structures. The project aims at providing a foundation for the development of seismic design and assessment methods of mixed structures, which are currently not covered by structural codes, including Eurocode 8.

Computer Vision System for Monitoring in Dynamic Structural Testing

In combination with standard transducers and data acquisition systems, computer vision can be adopted in order to perform the analysis of the behaviour of structures during dynamic tests such as earthquake simulations on shake tables. The paper describes the design and implementation of a machine vision system aimed at providing bi-dimensional position measurement of reflective markers directly placed on test specimens. The developed solution is composed of a scalable set of acquisition units, each consisting of a high definition digital camera and a personal computer. A sequence of images is acquired by the cameras and the position of the markers in the scene is estimated by means of a software application running on the computers. Each unit can perform measurements in a single plane which is defined in a previous calibration phase. The method has many advantages over the most commonly used acquisition devices such as accelerometers and potentiometers: first, the absence of contact between the acquisition device and the tested structure, which allows the non-invasive deployment of an arbitrary number of measurement targets, which is even more important in destructive tests, for preventing the loss of expensive transducers; second, the direct calculation of the position of an object in length units, without the need of post processing like integration and conversion, as required when using accelerometers in shake table tests. Besides, in the selected plane, thanks to the adoption of infrared illumination and filters to reduce environmental lighting interferences, each unit can follow the movements of a large number of markers (up to 50 for each camera in the performed tests) with a precision of around 0.05 mm. On the other hand, the method is by itself unable to overcome problems deriving from the three-dimensional movement of the selected markers. The paper also explains the different approaches and the corresponding results obtained while solving this issue.

Eucentre TREES Lab: Laboratory for Training and Research in Earthquake Engineering and Seismology

Italian awareness about the seismic vulnerability of its building stock dramatically increased after two earthquakes hit the nation: Umbria-Marche earthquake (1997) and Molise earthquake (2002). These two seismic events caused important losses in terms of human life as well as to the economic and artistic wealth. From here the decision to take important actions aiming to the reduction of the national seismic risk: creation of a new seismic zonation of Italy; adoption of a new seismic code; foundation of a research center on earthquake engineering. The paper reviews the development of Eucentre Foundation (European Centre for Training and Research in Earthquake Engineering) and its experimental laboratory TREES Lab (Laboratory for Training and Research in Earthquake Engineering and Seismology). A brief description of the experimental facilities at TREES Lab is reported, describing the principal characteristics of Shaking Table, Bearing Tester System, Reaction Wall-Strong Floor Structure and Mobile Unit. Furthermore, an introduction to some past and current research projects is given to explain what can be done exploiting the capabilities of the TREES Lab facility. Finally, the experimental activities within the SERIES (Seismic Engineering Research Infrastructures for European Synergies) project are described.

Shake Table Testing of a Half-Scaled RC-URM Wall Structure

With the introduction of higher seismic design forces in the Swiss loading standard of 2003 most unreinforced masonry (URM) buildings fail to satisfy the seismic design check. For this reason, in new construction projects, a number of URM walls are nowadays replaced by reinforced concrete (RC) walls. The lateral bracing system of the resulting structure consists therefore of URM walls and some RC walls which are coupled by RC slabs and masonry spandrels. The same situation characterises a number of seismically retrofitted URM building across Europe in which RC walls are added to the original structure to improve its seismic behaviour. Within the framework of the FP7-SERIES project, a four-storey RC-URM wall structure was tested on the shake table at the EUCENTRE TREES Laboratory (Laboratory for Training and Research in Earthquake Engineering and Engineering Seismology) in Pavia (Italy). The test was conducted at half-scale and is part of a larger research initiative on mixed RC-URM wall systems initiated at EPFL (Ecole Polytechnique Federale de Lausanne, Switzerland). The key objective of the testing campaign was to gain insight into the dynamic behaviour of mixed RC-URM wall structures and to provide input for the definition of a performance-based design approach of such mixed structural system. Multiple shaking at increasing intensity was used to test the dynamic behaviour of the examined building. During the final shaking several of the URM walls lost their axial load bearing capacity, however, the structure did not collapse as it was subjected to uni-directional loading only and the axial load was transferred to the RC walls and the URM walls that were loaded out-of-plane. Random noise vibration tests were performed to monitor the elongation of the natural periods induced by the damage progression. The paper presents details on the structural system and the selected ground motion, the test set-up and the instrumentation. Additionally, initial results of the shake table test are presented with a first interpretation of the observed structural behaviour.