Emanuela Speranzini

Structural reliability analysis using a standard deterministic finite element code

A method for performing a reliability analysis of structural systems within a standard finite element code is presented. This numerical procedure can be implemented in any finite element (f.e.) code having an internal optimization routine. The design points of structural problems are determined by calculating the minimum distance from the origin to the failure surface in a set of normalized variables, by using the minimization routine of the f.e. code. In order to test the procedure, simple structural systems are solved and the results are compared with those obtained by using different approaches. Some examples of application of the procedure for the reliability analysis of real structures are presented.

Durability analysis for FRP and SRG composites in civil applications

In this study, an effort was made to develop an experimental protocol to study the effects of accelerated ageing on composite materials based on bamboo and steel fibers. The physic-mechanical properties of different types of steel and bamboo fibers were investigated. Specimens were subjected to environmental agents. Mechanical and physical tests were used to measure the retained properties and to observe the causes of damage and strength reduction. The experimental data showed that resin properties may strongly influence the durability of FRP reinforcement, environmental combined cycles did not take to significant damage of conditioned specimens; steel fibers are sensitive to alkaline attack when resin does not provide adequate protection to fibers.

Image Analysis Technique for Material Behavior Evaluation in Civil Structures

The article presents a hybrid monitoring technique for the measurement of the deformation field. The goal is to obtain information about crack propagation in existing structures, for the purpose of monitoring their state of health. The measurement technique is based on the capture and analysis of a digital image set. Special markers were used on the surface of the structures that can be removed without damaging existing structures as the historical masonry. The digital image analysis was done using software specifically designed in Matlab to follow the tracking of the markers and determine the evolution of the deformation state. The method can be used in any type of structure but is particularly suitable when it is necessary not to damage the surface of structures. A series of experiments carried out on masonry walls of the Oliverian Museum (Pesaro, Italy) and Palazzo Silvi (Perugia, Italy) have allowed the validation of the procedure elaborated by comparing the results with those derived from traditional measuring techniques.

Bending Tests on Natural Fiber Reinforced Fir Wooden Elements

This paper gives the results of an experiment on timber elements reinforced in the tension zone through the application of strips of natural flax, hemp, bamboo and basalt fibers, creating different arrangements and using different quantities. The testing consisted of several stages that concerned wood rafters and beams of low and good quality. The wooden elements were subjected to bending tests that made it possible to measure the increase in capacity and stiffness resulting from the composite reinforcement.

Fibre Bragg Gratings for the Monitoring of Wooden Structures

The aim of this work was to develop and validate an experimental methodology suitable for analysing on-site the behaviour of fibre-reinforced wooden structures. The proposed measurement method is based on the application of fibre Bragg grating (FBG) strain sensors. An analysis of adhesive behaviour was performed preliminarily, which provided indications for choosing the type of adhesive and for the fibre bonding length in accordance with the volume of measurement. The first series of tests was carried out on wood samples to verify the coupling between the measuring sensor and the wood support when the latter is subject to mechanical stresses. The second investigation was done on site to test the behaviour of a historical wood floor before and after reinforcement by means of a series of tests performed using optical fibres with the Bragg grating. The optical fibre system measurements were compared to those obtained using a laser vibrometer, a measurement system of proven stability and precision. The comparison makes it possible to confirm the validity of the results and the reliability of the system for the monitoring of historic wooden structures.

Optimal Allocation of Available Resources to Improve the Reliability of Building Systems

This paper deals with structural optimization under limited resources. As a first relevant example, the problem of reduction of seismic risk in a built environment is tackled. Following other recent researches [1–3], three alternative “types” of retrofitting (upgrading intervention) of known cost per unit volume are considered; it is also assumed that the “vulnerability” of each building, the “losses” under an earthquake of given magnitude and their possible reduction thanks to an upgrading intervention are known. Such “losses” can be either (i) the direct and/or indirect “economical” costs of construction damage, or (ii) the non-monetary losses related to the number of “victims”, i.e. of persons physically affected by the ruin of a building. Use is made of “dynamic programming” in order to allocate the total available resources among the buildings, in such a way that the expected cost reduction is maximized; in these calculations, “economical” and non-monetary losses are considered separately; the possibility of taking both into account is also discussed. Numerical examples are presented.