Ciro Del Vecchio

Experimental Investigation of Exterior RC Beam-Column Joints Retrofitted with FRP Systems

Premature brittle failures because of seismic actions strongly affect the behavior of existing reinforced concrete (RC) structural systems. They commonly involve exterior beam-column joints of structures designed without transverse reinforcement. This paper investigates the behavior of unconfined joints that do not conform to current seismic codes and the effectiveness of externally bonded fiber-reinforced polymers (FRPs) as a strengthening technique. It presents an experimental program carried out on six full-scale RC corner joints under constant axial load and transverse cyclic loading in the as-built and FRP-strengthened configuration. After describing the specimen design strategy and test setup, seismic performance is compared. Particular attention is paid to comparing the experimental capacity of as-built joints and the capacity, which can be predicted on the basis of models available in the literature. Finally, a discussion on the effectiveness of different FRP-strengthening layouts is reported.

The Italian guidelines for seismic risk classification of constructions: technical principles and validation

The Italian “Guidelines for the seismic risk classification of constructions” approved in February 2017 define the technical principles for exploiting tax deductions with respect to seismic strengthening interventions on existing buildings (Sismabonus). Tax deductions represent a unique opportunity to improve the seismic safety of the existing Italian building stock. The guidelines are very simple and allow practitioners to deal with the sophisticated concepts behind modern seismic design, such as expected annual losses (EAL) and repair costs (expressed as a fraction of the Reconstruction Cost: %RC). The seismic risk classes of buildings and the class upgrade due to strengthening interventions can be assessed using the principles included in the guidelines. The seismic risk class is the minimum between the class defined by the building safety index at the ultimate limit state and the one related to the EAL. The latter class depends on the area under the curve of the expected losses, which is easily obtained by computing the safety index converted in the return period (annual frequency) at different limit states and the relevant %RC. This paper illustrates the technical principles at the base of the guidelines and the procedure used to calibrate the repair costs associated with the different limit states using the actual repair costs monitored in the reconstruction process following recent Italian earthquakes. Finally, simple tools to estimate the cost of the strengthening interventions to improve the seismic capacity at the life-safety limit states are provided.

Implementation and Validation of the Simple Lateral Mechanism Analysis (SLaMA) for the Seismic Performance Assessment of a Damaged Case Study Building

ABSTRACT The new guidelines for the seismic assessment of existing buildings recently introduced by the New Zealand Society for Earthquake Engineering (NZSEE) recommend the Simple Lateral Mechanism Analysis (SLaMA) as an “analytical” first phase of any other numerically-based analysis. This article illustrates the development of the SLaMA method and its validation with reference to an existing RC building severely damaged during the Christchurch earthquake (2011). The capacity of the lateral resisting systems is assessed from component/subassembly to system level. The comparison of the results with observed damage and with the outcomes of refined numerical analyses confirms the effectiveness of this method.

VALIDATION OF REFINED NUMERICAL MODELING FOR EXISTING RC BUILDINGS: COMPARISON BETWEEN PREDICTED AND OBSERVED EARTHQUAKE DAMAGE

A reliable estimation of the seismic performances of existing reinforced concrete building is of paramount importance to design proper retrofit solutions. Number of refined numerical models are nowadays available, nevertheless predicting the seismic performance and the earthquake damage at component level is still a challenging task. Marked nonlinear phenomena, strength and stiffness degradation and pinching affect the cyclic behavior of structural members designed with reinforcement details non-conforming with current seismic codes. This, along with the interaction between the bare frame and the stiff infills, makes complex the reproduction of the global structural behavior. This study focuses on a refined modeling procedure properly developed for existing RC frames. The modeling assumptions, the hysteresis assigned to the different building components and the modeling strategy accounting for the infill contribution are presented and discussed. The model validation at component and building level related to case-study buildings damaged by the L’Aquila (2009) earthquake is presented. A component-by-component comparison between predicted and observed damage is shown. The proposed numerical model and the in-depth discussion on the earthquake damage are useful to identify the building weaknesses, estimate the repair costs and design proper retrofit solutions. 2792 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 2792-2804

Correlation of In-Situ Material Characterization Tests and Experimental Performances of RC Members

Existing RC buildings of the Mediterranean area commonly show high variability in the material mechanical properties because of the construction age and manufacturing processes. Such a variability has been confirmed by number of in-situ tests performed during the reconstruction process in the aftermath of L’Aquila 2009 earthquake. In this context, destructive and non-destructive characterization tests are useful supporting tools to estimate the actual concrete mechanical properties and to improve the accuracy of the seismic capacity assessment. The paper reports of a wide material characterization program consisting of destructive and non-destructive tests carried out on a building severely damaged by the L’Aquila 2009 earthquake. Due to poor concrete mechanical properties and seismic structural weaknesses, the building was demolished. Portions of the structural systems have been extracted before the building demolition, subjected to material characterization tests and then tested in laboratory. The comparison between the two sets of material characterization test programs and the correlation with the experimental performances of an RC column tested under compressive axial load is presented herein.

NUMERICAL SEISMIC ASSESSMENT OF AN EXISTING BRIDGE WITH DIFFERENT SUPPORT CONFIGURATIONS

The assessment of existing infrastructures is a critical issue in the seismic protection of the modern societies. Field surveys in the aftermath of major seismic events have demonstrated the high vulnerability of highway bridges. This led to an increasing interest in the seismic performance assessment of existing bridges. The present paper deals with the seismic assessment of a bridge substructure reproducing typical existing Italian infrastructures. The reference structural system is a reinforced concrete (RC) 1:3 scale single span bridge that will be tested on the shaking table facilities at the University of Naples, Italy. The details of the numerical models adopted in the nonlinear dynamic analysis and the seismic performance prediction required for the test preparation are discussed in details. The record selection, the development of a step-by step validated numerical model are presented for the case study comprising an existing RC bridge designed primarily for gravity loads . The advanced numerical models and the assumptions made to account for the shear behavior of the piers are also illustrated. The preliminary results of the incremental dynamic analysis are presented and analyzed with reference to the effectiveness of the use of base isolation strategy commonly adopted for the seismic retrofit of the bridge deck.