Bond deterioration effects on corroded RC bridge pier in seismic zone

The effects of corrosion focusing on the consequences of bond strength deterioration for a reinforced concrete bridge pier in a seismic affected area are examined in this research. A bond degradation model based on the local bond stress-slip model presented in FIB Model Code 2010 is chosen. A motorway overpass object of a previous study, which considered the rebars cross-section reduction effect only, has been selected to assess the seismic capacity of the corroded pier in the time domain when bond degradation due to corrosion is also taken into account. The modification of strength capacity and ductility of the structural element is analyzed and the effect of corrosion during the whole service life of the structure is obtained. It is concluded that the effect of bond degradation is more critical for the safety of the pier than the effect of rebars cross-section loss

Resilience assessment of high damping rubber bearings in beyond-design conditions

Passive isolation systems are an established solution for the design of civil engineering structures that are required to provide superior performances in the case of a seismic event. Although their application to the seismic protection of bridges is currently limited, isolation systems are likely to become more widespread in the design of strategic infrastructures and facilities. In this work numerical investigations on the ultimate limit state conditions of filled high damping rubber bearings under cyclic shear loading are presented, focusing on the influence of the axial load with respect to the device

Damage risk assessment of historical asset using laser scan and finite element approach

Most part of valuable art goods are conserved in the Museums, which are in charge of their maintenance and their exposure; some of them, however, have an outdoor location, enriching the artistic and touristic worth of the towns which host them. The art works have an intrinsic vulnerability, due to their irregular shape, slenderness, fragility and - as concerns some sculptures of historical centers - to their oldness. The outdoor artifacts, however, have further hazard sources, since they can hardly be guarded, and they are subjected to possible vandalism actions and lunatic or terrorist attacks. In this work the dynamic response of artifacts to blasts of assigned intensity are investigated on a case-study, i.e. the Fountain of Neptune, located in "Piazza della Signoria", in Florence. The Fountain of Neptune is a marble and bronze opus made by Bartolomeo Ammannati between 1560 and 1565. The main character of the Fountain, Neptune, is a marble statue 5.7 meters tall, with a weight equal to 11.5 ton. A preliminary laser scanner survey has been made to achieve the geometrical representation of the statue. The considered load condition consists of an explosion caused by 10 kg of TNT placed at 8 meters from the Fountain. The dynamic behavior of the complex under the assumed load has been represented through a numerical analysis, by considering the main statue only - since it is the slenderest element of the complex - and by assuming it as simply supported on the pedestal, without any connector. The obtained results showed the vulnerability of the statue to the assumed blast, and pointed out the role plaid by the contact assumption on its dynamic response

Developing a laboratory facility to assess friction coefficients of standing samples

The numerical representation of the dynamic response of art works is the most reliable instrument to predict their seismic safety. Their adoption, however, require the knowledge of the effective mechanical properties of the artifacts and their restraint conditions. Namely, the amount of friction arising between standing art works and their supports largely affects the quality of their collapse and, therefore, the choice of the model to adopt in the analysis. In this work a facility for assessing the dynamic contact behaviour of marble sample standing on different supports has been investigated. The facility consists of a dynamic test to perform through the bidirectional shaking table at the Disaster Resilience Simulation Laboratory at the Politecnico di Torino. The friction coefficient has been found from the dynamic test by comparing the acceleration registered at the load cell, which is related to the reaction of the sample, and one measured at the shaking table surface. The obtained values of friction coefficient have been related to the velocity of the adopted input. A preliminary test on a single concrete sample has been performed to check the proposed procedure, by considering three different loading conditions: one of them is the acceleration history of a real ground motion, while the other two have a constant amplitude and a constant frequency, respectively

Seismic Resilience of Electric Power Networks in Urban Areas

Recent natural disasters have raised the question of how communities can recover from extreme events. In the last decade the research has been focusing on analyzing interdependencies between different networks. In this paper the focus is on the distribution power network, developing a method to estimate a realistic grid of a vir-tual city called “Ideal City” freely inspired to the city of Turin in Italy. A software called Matpower devel-oped by the Joint Research Center has been used for the load flow analysis of the power network. Fragility curves, repair costs and downtime are evaluated using FEMA’s database. Finally, a strategy to improve the network resilience is proposed considering the complexity of the environmen

Vulnerability Assessment of a Civic Tower Using Ambient Vibration Tests

This paper focuses on the vulnerability assessment of a civic tower built in 1512, which is now considered a national monument. It is the original bell tower of S. Ambrogio church that was destroyed in 1809. Experimental investigations have been carried out on this historical tower. First, detailed investigations have been carried out to identify the geometry of the tower as well as the mechanical features of the constituting materials. Then, ambient vibration tests have been applied using five Micro Electro-Mechanical Systems (MEMS) sensors to detect of the main dynamic features, e.g., modal parameters and damping. Two output-only identification methods, including Frequency Domain Decomposition and Random Decrement Techniques, have been used. The outcomes of the modal identification have been employed to inform the FE model. The numerical analysis can be used for vulnerability assessment, providing a valuable picture of possible damage evolution, tower collapse mechanism, and subsequently, useful hints for the execution of structural retrofitting strategies

Exploring simulation tools for urban seismic analysis and resilience assessment

Nowadays, the refined models of simulation to evaluate the seismic damage in an urban area are becoming of paramount interest for the scientific community. Regional seismic damage simulation can potentially provide valuable information that can facilitate decision making, enhance planning for disaster mitigation, and reduce human and economic losses. However, the application of refined models is limited because of their high computational cost and needs of highly experienced users. For these reasons, these approaches remain academic experiences. This study proposes a straightforward approach to the problem, at the same time competitive, to simulate the seismic response and to assess the degree of damage at urban scale. At first, the simulation of the standard building is performed using an equivalent single degree of freedom model. Subsequently, the same approach is extended to a number of regular buildings from a virtual city sample for time-history seismic response analysis. The first part of this work is devoted to present the methodology to prepare the one-degree-of-freedom model of the standard building by comparing it with a refined multi degrees of freedom model as a target. Finally, a seismic damage simulation of a virtual city sample is implemented to demonstrate the capacity and advantages of the proposed method at increasing seismic intensities for damage assessment. It is the starting phase for further multi-hazards analyses at the regional scale through agent-based models

Temperature Effects Removal from Non-Stationary Bridge–Vehicle Interaction Signals for ML Damage Detection

The development of Structural Health Monitoring (SHM) and Non-Destructive Testing (NDT) techniques has rapidly evolved and matured over the past few decades. Advances in sensor technology have facilitated deploying SHM systems for large-scale structures and local NDT of structural members. Although both methods have been successfully applied to identify structural damage in various systems, Environmental and Operational Condition (EOC) variations can influence sensor measurements and mask damage signatures in the structural response. EOCs include environmental conditions, such as temperature, humidity, and wind, as well as operational conditions, such as mass loading, vibration, and boundary conditions. The effect of EOCs can significantly undermine the reliability and robustness of damage assessment technologies and limit their performance. Thus, successful SHM and NDT systems can compensate for changing EOCs. This paper provides a stateof-the-art review of the effects of EOCs on SHM and NDT systems. It presents recent developments in advanced sensing technology, signal processing, and analysis techniques that aim to eliminate the masking effect of EOC variations and increase the damage sensitivity and performance of SHM and NDT systems. The paper concludes with current research challenges, trends, and recommendations for future research directions

Modelling interdependencies among critical infrastructures at urban scale

Modern urban areas are transforming into sophisticated systems integrating both structures and infrastructures. This interconnection significantly increases the risk of disasters, which involves typical urban areas at different levels with structural, social, psychological and economic consequences. Therefore, improving emergency preparedness and mitigating possible disaster-induced losses of populous modern cities is becoming crucial. Critical infrastructure, e.g. the transportation, electric and water networks, can be damaged due to inherent fragility with respect to the initiating external hazard (e.g. earthquake). Buildings collapse after strong earthquakes is the typical source of malfunctioning for connected critical infrastructures. In this work, the effect of debris after structural collapse or extensive damages on related networks is studied. A new formula to evaluate the debris affected area as function of the geometric characteristics of the masonry buildings is proposed. This strategy can be implemented in a virtual city model that is recognized useful for decision makers to quantify the performance of critical infrastructures following a disaster and to plan better resilience strategies in order to limit losses and downtime

Nondestructive monitoring techniques for crack detection and localization in RC elements

This paper presents the structural and damage assessment of a reinforced concrete (RC) beam subjected to a four-point bending test until yielding of reinforcing steel. The deterioration progress was monitored using different nondestructive testing (NDT) techniques. The strain was measured by distributed fiber optic sensors (FOSs), embedded prior to concrete pouring. The initiation and propagation of cracks were monitored by acoustic emission (AE) sensors attached to the surface of the material. The recorded AE activity results in good agreement with FOS strain measurements. The results of the integrated monitoring system are confirmed by visual observation of the actual crack pattern. At different loading steps, digital image correlation (DIC) analysis was also conducted