Andrea Prota

Reconstruction process of damaged residential buildings outside historical centres after the L’Aquila earthquake: part I—"light damage" reconstruction

Assessment of the seismic damage and usability of the building stock started a few days after the L’Aquila earthquake in order to evaluate the safety conditions of the buildings concerned. Several ordinances of the Prime Minister were issued to regulate the reconstruction process. In particular, based also on damage level, the procedures for repair, strengthening or demolition/reconstruction of residential buildings were established with the definition of relevant state funding. For each damaged building, practitioners engaged by property owners designed repair and strengthening interventions and then computed the corresponding costs. These projects were the technical basis for funding applications that owners submitted to the government. Technical and financial information collected during the approval procedure of such applications allowed compilation of a database regarding 5775 residential buildings damaged by the L’Aquila earthquake. The present study examines the restoration policy and the procedures regulating the reconstruction process of residential property outside city centres. In particular, the data related to the first phase of the reconstruction process (the so-called “light damage” reconstruction) to recover the usability of slightly damaged buildings are illustrated. The discussion focuses on the time-to-approval of funding applications and on the public contributions granted for repair and local strengthening works.

Seismic Strengthening of Masonry Vaults with Abutments Using Textile-Reinforced Mortar

AbstractInnovative materials and technologies have been developed to limit the effects of earthquakes on structures, and the use of composite materials has been shown to be effective in existing buildings. In view of this background, experimental tests can provide a contribution to the interpretation of available strengthening interventions. The results of experiments with an innovative strengthening system are presented herein. The strengthening technique used is based on a textile-reinforced mortar (TRM) system coupled with traditional strengthening approaches, and was applied to a type of full-scale masonry vault that is typically found in the roofs of religious buildings. The experiments consisted of several shaking table tests, both before and after the application of the strengthening system. The seismic behavior of the vault after strengthening was significantly improved. The instrumental response of the vault started to change before the initial visible damage, which only occurred when the peak gr...

Remarks on damage and response of school buildings after the Central Italy earthquake sequence

The seismic assessment of the vulnerability of existing public structures, especially school buildings, is a crucial issue in seismic prone countries. Recently, several national and regional programs and activities have focussed on the mitigation of Italian public buildings. They promote the scheduling of public buildings’ structural safety assessment and, when needed, the design and execution of strengthening interventions. Nevertheless, the three strong earthquakes that occurred in the last decade in Italy, Abruzzo (2009), Emilia (2012), and Central Italy (2016), confirmed the vulnerability of school buildings and the social importance of their quick re-opening after a damaging earthquake. In the present paper, the activities carried out on 1514 school building structures in the aftermath of the 2016 Central Italy earthquake sequence are reported and analysed. According to survey data collected by post-earthquake usability inspections, the paper analyses the school buildings characteristics, damage level and extent to structural and non-structural components as well as the correlation between seismic intensity and observed damage.

Confinement of Full-Scale Masonry Columns with FRCM Systems

The effectiveness of FRP systems as a confinement technique to strengthen masonry columns has been widely investigated in the last decades. Recently, a new technique, Fabric Reinforced Cementitious Matrix (FRCM), based on the use of fibrous nets embedded in inorganic matrix, has been developed and investigated as a strengthening solution in masonry buildings. Actually, the number of experimental tests on masonry columns confined by using FRCM systems is very limited, especially for real scale specimens. To fill such gap an experimental program aimed at investigating the behaviour of full scale columns made of limestone masonry blocks confined with different FRCM systems has been carried out. The results of four uniaxial compression tests are illustrated and discussed. The used FRCM systems are made with glass and basalt dry nets embedded in a lime-based mortar. The influence of transverse confinement by using internal reinforcement in forms of pultruded GFRP bars has been also investigated. The mechanical properties of the confined specimens resulted increased in terms of load-carrying capacity and ultimate axial strain.

Repair Costs of Existing RC Buildings Damaged by the L'Aquila Earthquake and Comparison with FEMA P-58 Predictions

Recent seismic events are a unique opportunity to monitor and collect details of direct repair costs and the downtimes associated with massive reconstruction processes. This paper focuses on the actual repair costs of five RC buildings damaged by the 2009 LAquila earthquake. The repair costs for structural and nonstructural components that experienced different types of earthquake damage are discussed and then used as a benchmark for the predictions. The comparison at both the building and component levels revealed that the FEMA P-58 methodology is suitable, in general, for application to different types of building stock. Ad hoc upgrades to the FEMA fragility database for components that are typical of the Mediterranean area are required. When implementing the proposed modifications, a reasonable level of consistency is achieved in terms of actual and predicted repair costs (differences in the range of 30–48%). A discussion on the actual repair costs and the main differences with the predicted costs for infills and partitions, structural subassemblies, floor finishes, and other acceleration-sensitive nonstructural components is provided, along with suggestions for further improving.

Numerical Investigation of Masonry Strengthened with Composites

In this work, two main fiber strengthening systems typically applied in masonry structures have been investigated: composites made of basalt and hemp fibers, coupled with inorganic matrix. Starting from the experimental results on composites, the out-of-plane behavior of the strengthened masonry was assessed according to several numerical analyses. In a first step, the ultimate behavior was assessed in terms of P (axial load)-M (bending moment) domain (i.e., failure surface), changing several mechanical parameters. In order to assess the ductility capacity of the strengthened masonry elements, the P-M domain was estimated starting from the bending moment-curvature diagrams. Key information about the impact of several mechanical parameters on both the capacity and the ductility was considered. Furthermore, the numerical analyses allow the assessment of the efficiency of the strengthening system, changing the main mechanical properties. Basalt fibers had lower efficiency when applied to weak masonry. In this case, the elastic properties of the masonry did not influence the structural behavior under a no tension assumption for the masonry. Conversely, their impact became non-negligible, especially for higher values of the compressive strength of the masonry. The stress-strain curve used to model the composite impacted the flexural strength. Natural fibers provided similar outcomes, but a first difference regards the higher mechanical compatibility of the strengthening system with the substrate. In this case, the ultimate condition is due to the failure mode of the composite. The stress-strain curves used to model the strengthening system are crucial in the ductility estimation of the strengthened masonry. However, the behavior of the composite strongly influences the curvature ductility in the case of higher compressive strength for masonry. The numerical results discussed in this paper provide the base to develop normalized capacity models able to provide important information on the out-of-plane behavior of masonry elements strengthened with inorganic matrix and several kinds of fibers, both synthetic and natural.

Comparative Analysis of Existing RC Columns Jacketed with CFRP or FRCC

Reinforced concrete (RC) columns typical of existing structures often exhibit premature failures during seismic events (i.e., longitudinal bars buckling and shear interaction mechanisms) due to the poor quality concrete and the absence of proper seismic details in the potential plastic hinge region. The Fiber Reinforced Polymers (FRP) externally bonded reinforcement is known to be a valid technique to improve the shear capacity or the ductility of existing RC columns. However, few experimental tests have proven its effectiveness in the case of columns affected by shear interaction mechanisms. In this work, the behavior of existing RC columns with border line behavior between flexure and shear have been investigated in the case of poor quality concrete and light FRP strengthening with local jacketing and medium quality concrete and strong FRP strengthening with local jacketing, in order to highlight the effect of concrete strength on the effectiveness of the retrofit intervention. As an alternative to FRP jacketing; the effectiveness of the Fiber Reinforced Cementitious Composite (FRCC) jacketing for the seismic strengthening of columns with highly deteriorated concrete cover or columns already damaged by an earthquake is also evaluated. Six full-scale RC columns have been tested under cyclic loading: one was used as a control specimen; four were strengthened in the potential plastic hinge region with carbon FRP (CFRP); and one was fully jacketed with FRCC. The comparison between poor and medium quality concrete columns showed that the CFRP local jacketing is more effective in the case of poor quality concrete. The FRCC jacketing appears to be a sound repair strategy and a suitable alternative to the FRP jacketing in case of poor quality; however, more experimental research is needed for improving this retrofit technique.

BEHAVIOR OF CFRP CONFINED RC COLUMNS UNDER AXIAL LOAD AND UNIAXIAL CYCLIC LATERAL LOADING

In recent years, the use of FRP wrapping of reinforced concrete (RC) members has been recognized as a reliable method for seismic retrofit of existing structures. The external confinement of existing RC columns with FRPs is a sound technique for increasing the columns ductility, by preventing brittle mechanisms such as bars buckling or post-yielding shear failures and by improving the mechanical properties of concrete due to the lateral confining effect. Several models have been developed for predicting the ultimate displacement capacity and the ductility of FRP confined RC columns, however the accuracy of predictions has not been well established yet. In this study, the experimental behavior of a RC column confined at the plastic hinge region with one ply of carbon fibers (CFRP) is firstly analyzed and compared with the response of the unstrengthened control column. The specimens are cantilevers loaded with a low compressive axial load and subjected to uniaxial cyclic horizontal displacements. The responses of the columns have been analyzed and compared in terms of failure modes and strength and deformation capacity. Particular attention has been focused on the strain distribution recorded on the CFRP strips used to confine the RC column end; the strain profiles along the cross-section perimeter in case of axial load and bending moment interaction are presented and discussed at different load levels. In the second part of the study, the deformation capacity of FRP confined RC column is analytically obtained, by using models for FRP confined square columns available in literature. The comparison between analytical and experimental results showed that currently available models give conservative predictions of ultimate deformation capacity of confined columns. 2753 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 2753-2764