This paper deals with the preliminary results of an extensive experimental program devoted to the evaluation of the ultimate resistance of aluminium alloy channels subjected to local buckling under uniform compression. In particular, the results of 34 stub column tests performed on aluminium channels made of 6000 series alloy are presented.Both the effective width approach and the effective thickness approach are applied for predicting the local buckling resistance of channels under uniform compression. The accuracy of the two approaches is discussed on the basis of the experimental evidence.The Eurocode 9 provisions for local buckling of both flat internal and flat outstanding elements in thin walled sections are examined and compared with the obtained results.

This paper summarizes the main features of the seismic retrofitting project of a school building located in Montella (AV), Italy. Specifically, it describes the as-built status in terms of structural organization, member detailing, and existing materials properties. Then, it outlines the main assumptions and results obtained from seismic analysis, of both as-built and retrofitted structure. Comments about the construction stage are also reported by describing the main operations put in place with the aim to realize the shear wall system, which is the main retrofitting intervention, and some local strengthening measures consisting in steel plating and jacketing of some underdesigned RC members. Some emphasis is placed on the realization of micro-piles and extra foundations of the aforementioned shear walls. Besides its specific interest, the reported project may be intended as representative of a wide class of seismic assessment and retrofitting projects that have been realized in Italy in the last decade.

Fabric-reinforced cementitious matrix (FRCM) composites have recently enter the market as a promising, sustainable, and durable solution for the external strengthening of RC and masonry structural members. In this paper, an analytical study on the confinement of concrete with FRCM materials is presented. To this purpose, a wide database including results of compression tests performed on more than 250 concrete cylinders externally wrapped with FRCM was collected from the literature, firstly to perform an overall analysis of the efficiency of the FRCM confinement by varying some of the relevant parameters, such as: type of fiber (glass, carbon, steel, PBO or basalt) and geometry of the mesh, number of layers, composition of the inorganic matrix and compressive strength of the unconfined concrete. Then, preliminary relationships for estimating the compression strength of FRCM confined concrete were developed through best-fit techniques.

This paper outlines a rational strategy for retrofitting Reinforced Concrete (RC), which is based on combing member- and structure-level techniques in order to achieve optimal design objectives in a Performance-Based approach. Member-level techniques (such as confinement with composite materials, steel or concrete jacketing) are supposed to enhance capacity of single members, whereas structure-level techniques (generally based on introducing steel bracings systems or shear walls) aim to reduce the seismic demand on the existing frame as a whole. A novel procedure, based on a “dedicated” genetic algorithms, is developed by the authors for selecting “optimal” retrofitting solutions, among the technically feasible ones, obtained by combining alternative configurations of steel bracing systems and FRP-confinement of critical members. The main assumptions about the representations of “individuals” and the main information about the genetic operations (i.e. selection, crossover and mutation) are summarised in the paper. Finally, a sample application of the procedure is proposed with the aim to demonstrate its potential in selecting rational retrofitting solutions.

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The mechanical behaviour of Recycled Aggregate Concrete (RAC) is investigated by reporting the main results of experimental tests intended at understanding the influence of Recycled Concrete Aggregates (RCAs) on the resulting mechanical properties of concrete. The focus is placed on the higher porosity of RCAs and their higher water absorption capacity. Consequently, the role of the initial moisture conditions of RCAs at mixing is also unveiled and its consequences on both the hydration reaction and the time evolution of compressive strength are highlighted. The influence of processing procedures intended at reducing the aforementioned porosity is also discussed.

This paper presents a rational strategy developed for optimizing seismic retrofitting of Reinforced Concrete (RC) frames.It is based on combing member-and structure-level techniques in order to achieve optimal design objectives within a multi-level Performance-Based approach.On the one hand, in principle, confinement with composite materials, steel and/or concrete jacketing might be considered as a member-level technique capable to enhance the capacity of under-designed members and, consequently, of the structure as a whole.On the other hand, introducing steel bracing systems or shear walls might be taken into account as structure-level techniques.Generally, member-and structure-level techniques are not employed together in seismic retrofitting or, in the cases in which they are combined, no well-established rules are available for choosing their optimal combination.However, a synergistic use of such techniques by means of well-defined procedures could help designers obtain optimal seismic retrofitting performance.The latest progresses about a procedure developed by the authors for selecting the optimal retrofitting solution among the technically feasible ones, obtained by combining alternative configurations of steel bracing systems and FRP-confinement of critical members, are presented herein.Specifically, the main aspects about formulating a genetic algorithm capable to select the "fittest" retrofitting solution is implemented and summarised.The main assumptions about the representations of "individuals" as part of this genetic algorithm and the main information about the generic operations (i.e.selection, crossover and mutation) are outlined.Finally, the procedure is applied to a 3D frame with the aim to demonstrate its potential.

Existing Reinforced Concrete (RC) structures built in earthquake-prone regions during the '60s and '70s of the past century generally result vulnerable to seismic actions. In such structures masonry walls are widely adopted both as internal partitions and external infills. Recent studies demonstrate that such components can significantly affect the global response of RC structures. Nevertheless, the mechanical contribution of infills is neglected in the common design practice and they are included in structural models by means of their weight and mass only. Both accurate modelling of masonry infill and practice-oriented approaches are nowadays available for simulating the nonlinear response of masonry walls, whereas no well established methods exist for evaluating the global response of RC infilled frames by means of simplified Nonlinear Static (NLS) analysis. However, simplified procedures, based on extending the N2 Method, have been recently developed. Two of those procedures are summarised and compared in the present paper. More specifically, a parametric analysis is proposed with the aim to highlight their weaknesses and strengths. To do so, the results of both static and dynamic analyses are reported and discussed.

This work is intended at generalising the μd-T-Rμ relationships, currently available in the literature for defining inelastic design spectra, with the aim to take into account the actual dissipative capacity of structural systems. In fact, the inelastic spectra currently adopted in Nonlinear Static Analyses are generally based on an ideal elastic-perfectly plastic behaviour. Therefore, a more general hysteretic law is considered for parameterising the dissipative capacity of the structural systems under consideration. Non Linear Time History analyses are carried out for evaluating their dynamic response. A calibration of the aforementioned μd-T-Rμ relationships is proposed for enhancing the accuracy of inelastic seismic design spectra and, hence, the resulting relationships widely adopted in seismic analysis procedures, such as the N2 Method.

The experimental activity reported in this chapter was aimed at enhancing the knowledge about the mechanical behaviour and durability of concretes made with Recycled Concrete Aggregates (RCAs) and coal Fly Ash (FA) and their possible use for structural purposes. To this end, starting from a reference concrete composition, twelve mixtures were designed by replacing part of the ordinary constituents (i.e. cement, sand and coarse aggregates) with the FA and RCAs. The time evolution of the compressive strength, as well as the splitting strength, were measured with the aim to monitor the mechanical performance, whereas the durability performance was scrutinised by measuring water permeability, carbonation depth and chloride-ions ingress. The obtained results unveil the influence of both RCAs and FA on the resulting concrete performance and highlight that their combined use can lead to a synergistic effect in terms of the relevant physical and mechanical properties of structural concrete.

The seismic response of non-structural components in civil and industrial buildings, often neglected or disregarded in the common design/assessment practice, revealed its dramatic relevance in recent seismic events that resulted in significant damage observed in the wide class of “objects” referred to as “non-structural components” (e.g., partitions, masonry infill, suspended ceilings, finishing, specific equipment and so on. The observed damage, sometimes leading to collapse of these components and even loss of human lives, highlighted the lack of knowledge that still affects both analysis procedures and design/assessment methods currently adopted for analysing their seismic response. This paper is mainly intended at providing readers with an overview of both the historical development and the current state of the formulations adopted by codes and standards for evaluating the maximum accelerations induced by seismic shakings on non-structural components. The difference among these formulations is firstly outlined and the predictions based on the most up-to-date codes are compared with the results of a wide parametric analysis based on a 2DOF system, intended at simulating the coupled response of both main structure and non-structural component. This parametric comparison shows that the current formulations are not fully capable of reproducing the effect of the interaction between main structure and non-structural components

This work reports the results of an experimental programme aimed at investigating the in-plane behaviour of clay-brick masonry walls externally strengthened by carbon fiber reinforced polymer (CFRP) strips. Particularly, four different geometrical layouts were considered for the CFRP strips, though keeping unchanged the quantity of composites employed in each wall. Firstly, a preliminary experimental work was carried out on samples of the constitutive materials for quantifying their key mechanical properties and evaluating the bond behaviour of FRP strips on the masonry substrates. Then, eleven cyclic shear-compression tests were performed to observe the response of strengthened walls and the influence of the strengthening layouts under investigation. The proposed experimental report is intended as a contribution to the current state of knowledge about the behaviour of FRP-strengthened masonry walls: it is available to assess the accuracy and possibly improve the predictive capacity of design-oriented capacity models. Finally, the comparison of the reported experimental results with the predictions obtained by applying the analytical relationships proposed by a recently issued guideline for FRP strengthening of masonry structures is proposed.

This study reports the results of a wide experimental campaign intended at investigating the mechanical and durability performance of structural concretes made with Recycled Concrete Aggregates (RCAs) and coal Fly Ash (FA). To this end, twelve mixtures were designed by replacing part of the ordinary constituents (i.e. cement, sand and coarse aggregates) of a reference one with RCAs and FA. Samples of these mixtures were subjected to various tests aimed at assessing both their structural properties and durability performance. As for the former, time evolution of compressive strength was monitored at various curing times up to 365 days, and the splitting strength was determined at 28 days. Moreover, the expected durability performance of the aforementioned concrete mixtures was scrutinised by measuring some relevant physical quantities, such as water permeability, carbonation depth and chloride-ions ingress at various curing ages.The results obtained from these tests are often not self-evident, as they unveil the synergistic effect of combining both RCAs and FA on the resulting physical and mechanical properties of "green" concrete. Moreover, they demonstrate that the current code restrictions on the use of both RCAs and FA for structural concrete might be significantly relaxed, especially if the delayed binder effect, induced by the latter, is duly taken into account and, hence, concrete properties are measured at curing times longer than the conventional 28 days. (C) 2016 Elsevier Ltd. All rights reserved.

This paper presents the results of experimental tests intended at investigating the behaviour of two cost competitive solutions for realising dissipative devices to be adopted as link elements in Y-shaped eccentric braces (EB), widely employed both for seismic protection of newly designed structures and retrofitting of existing ones. These structural components, generally referred to as Steel Slit Shape (SSS) and Short Link (SL) devices, were realised through standard welding and cutting procedures generally employed in steel workshops. Experimental tests with both constant and variable displacement amplitude protocols were carried out for observing the mechanical performance for these devices under cyclic actions. Since a fast degradation in shear strength was generally observed for all the tested specimens, a low-cycle fatigue was identified: it resulted that the same curve can be employed describing the number of cycles leading to low-fatigue failure for a given amplitude of the imposed cyclic displacement history. This curve is an essential tool for describing the behaviour of this devices that, although characterised by poorer mechanical performance under cyclic actions, have the potential to be utilised as dissipative components, for instance in Y-shaped steel bracings adopted for retrofitting reinforced concrete structures in medium-to-low seismic intensity area. (C) 2016 Elsevier Ltd. All rights reserved.

In the last decade, nonlinear static procedures emerged as the reference practice-oriented analysis method for structures under seismic actions. These procedures are generally based upon two key steps: (i) performing a nonlinear static (pushover) analysis under lateral forces and (ii) evaluating the seismic demand through the so-called capacity spectrum obtained at the end of the previous step.This paper specifically deals with the latter and proposes a parametric comparison between two wide classes of methods formally based on conceptually alternative approaches for defining the demand spectra in nonlinear static analyses of dissipative structures. First of all, the paper outlines the main conceptual aspects of such alternative methods and reports their key operational details. Particularly, it proposes a dimensionless formulation of their relationships and demonstrates that both methods are based upon a small and almost common set of dimensionless parameters. Therefore, a wide parametric analysis is proposed to compare the ductility demand obtained by means of these two alternative methods with the aim of describing and quantifying the different predictions obtained by applying such methods. Finally, the results of nonlinear time-history analyses are proposed for assessing the two aforementioned methods. (C) 2015 Elsevier Ltd. All rights reserved.