Seismic vulnerability assessment of bridges

The basic idea of the project is to apply sophisticated as well as simple methods to bridge Warth/ Austria, which was built 20 years ago, in order to assess its earthquake capacity. Comparing the results the simplest method should be defined which gives the structural behaviour in an adequate way. The goal is the development of simple methods for the assessment, which are based on measurements of structural parameters. In this project expensive testing is carried out (dynamic insitu measurements for one week, pseudodynamic tests in ELSA lab) which cannot be the standard procedure for each bridge to be assessed. The benefit of the in-situ test is that we can start with an updated FE model which is close to the (linear) reality. The main benefit of the pseudodynamic tests will be the information on the ductile behaviour of large R/C bridge piers with hollow cross section. Hence, the first main goal of the project is to find the simplest procedure giving the necessary parameters in an adequate way. The second main goal is to elaborate information for the authorities and bridge owners about the most adequate retrofitting measures. It is emphasized that a lot of work has been done all over the world. But it is important to have in mind the bridge types mainly used in (Central) Europe and especially in the Alpine Regions. In the past the greater part of all research work on bridges in the field of Earthquake Engineering concentrated on small and medium bridges and some large special constructions like suspension bridges and cable-stayedbridges. In our project, besides reliability also the intervention costs will be evaluated in order help the bridge owner to select the most adequate measure.

2002

Recent earthquake effects on reinforced concrete bridges have shown that many behave poorly and some possess very low levels of safety, to the extent that they are at risk of collapse, especially those built according to outdated seismic codes. Thus, efforts must be made to develop and apply accurate bridge assessment methodologies that will assist in the determination of failure probability in order to evaluate the need for retrofitting and to improve seismic safety levels.

Earthquake Spectra, 2014

This study focuses on the evaluation of the seismic vulnerability of the Italian roadway bridge stock, within the framework of a Civil Protection sponsored project. A comprehensive database of existing bridges (17,000 bridges with different level of knowledge) was implemented. At the core of the study stands a procedure for automatically carrying out state-of-the-art analytical evaluation of fragility curves for two performance levels—damage and collapse—on an individual bridge basis. A WebGIS was developed to handle data and results. The main outputs are maps of bridge seismic risk (from the fragilities and the hazard maps) at the national level and real-time scenario damage-probability maps (from the fragilities and the scenario shake maps). In the latter case, the WebGIS also performs network analysis to identify routes to be followed by rescue teams. Consistency of the fragility derivation over the entire bridge stock is regarded as a major advantage of the adopted approach.

2014

This work describes the main results of an in situ experimental campaign carried out in the context of the seismic assessment of 71 existing road bridges as representative of the main structural typologies located in the Veneto region and pertaining to the regional roadway managing authority Veneto Strade SpA. An initial in situ and laboratory experimental campaign on basic materials and an overall geometrical survey were carried out for each bridge, using different tests according to the construction typologies, with the aim of characterising the main mechanical parameters of the significant structural elements. Structural assessment has been subsequently carried out according to the parameters derived from the above campaign and the design ground motion action. The results have been compared with those deriving from a preliminary analysis conducted on the basis of some assumptions on materials' mechanical characteristics related to the original design documents and the construction practice at the time of the structures' edification. This comparative analysis could give some insights on appropriate and rational planning of inspections on existing bridges and reliability of basic assumptions for their seismic assessment.

Revista Facultad de Ingeniería, Universidad de Antioquia, 2022

The recent devastating earthquakes have revealed that bridges are one of the most vulnerable components of transportation systems. These seismic events highlighted the need to mitigate the risk resulting from the failure of bridges. This study aims to consider the seismic risk of an extensive heritage of existing civil engineering structures proceeding with prioritization. This imposes the need to consider the design of a geographic information system (GIS) based on the analysis of the different components of risk: hazard, vulnerability, and risk. The assessment of the seismic vulnerability of bridges integrates the various structural and non-structural components of bridges, taking into account their specificities in Algeria. The application of this approach to the Oran region has resulted in the development of a tool using a database to process as much geolocated information as possible, thus contributing to more efficient crisis management, and making it possible to avoid bridge damage and failures that can result in loss of life and monetary losses. This tool could also be used for the inspection of bridges as well as the optimal prioritization of preventive and corrective measures necessary before a major earthquake hits the bridge network in the Oran Region.

2016

The present paper describes a methodology with its different steps used for assessing the vulnerability of existing reinforced concrete bridges at the capital city of Algeria, Algiers. The methodology was applied to 148 reinforced concrete bridges localized at Algiers and represents a part of the strategic bridges. It is a simple and efficient inspection method for the preliminary evaluation of seismic vulnerability of existing bridges. This assessment was conducted based on two earthquake scenarios considering two existing faults that can generate earthquakes with a maximum acceleration of 0.8g. The main findings of this study are summarized in this paper.

Advances in Bridge Engineering

Bridges are vital to modern transportation infrastructure, providing convenient and efficient access to different locations. However, these structures are susceptible to forces that can cause significant damage and pose a hazard in the event of seismic activity. A country's economy relies heavily on its bridge infrastructure, but many older bridges built before 1970 are showing signs of deterioration due to climate change and other factors. At the time of their construction, seismic design codes did not provide sufficient guidance on proper design and detailing to ensure ductility and capacity, resulting in deficient bridges. This paper provides a brief overview of the literature on the seismic behaviour of bridges and the analytical methods used to evaluate their performance. Various factors that influence the behaviour of different types of bridges are also discussed. This paper aims to establish a theoretical foundation for selecting appropriate methods to analyze bridge stru...

Depending on the location, highway bridges can often support considerable amounts of traffic. Due to the limitations on current earthquake forecasting techniques, a normal amount of traffic will also typically remain on a bridge when an earthquake occurs. In addition to traffic, scour effects are also a potential hazard to bridge piers that may simultaneously impact the structural integrity of the bridge together with seismic loads. Although a few studies investigating the combined effect of extreme and service loads have been conducted on long-span bridges or in high-seismic zones, the studies on typical short-and medium-span bridges in low and moderate seismic zones are rare. A general dynamic simulation methodology is introduced to study the combined realistic service and extreme loads on short-and medium-span bridges. Following the introduction of the methodology, a numerical study investigating the seismic performance of a typical highway bridge in mountainous states is carried out. The bridge is subjected to different combinations of traffic, seismic, and scour and the effects on the structural performance of the bridge are investigated. The bridge, including both superstructure and substructure, is modeled in detail using SAP2000 to accommodate the goals of this study. The traffic load is considered through dynamic interaction analysis of vehicles in the simulated stochastic traffic flow. Through studying the bridge performance under various combined extreme and service loads, findings are made about controlling cases for different bridge responses and the validity of the traditional superposition approach with consideration to load combinations is also discussed. As the initial effort studied the bridge performance under multiple service and extreme loads, this study sheds some light on more comprehensive studies for the future.

To facilitate quick post-earthquake assessment of bridge condition, monitoring systems can be installed onto structures. However, due to high cost it is impractical to monitor all bridges within a network. Bridges which are exposed to increased hazards, are vulnerable and have high failure consequences pose the greatest risk to network functionality should they fail in a seismic event, and would therefore benefit the most from implementation of monitoring systems and quick condition assessment methodologies. This paper outlines a methodology to prioritise bridges for monitoring and quick condition assessment based on their seismic risk. The methodology uses four factors to determine risk, i.e. seismic hazard, vulnerability, failure impact and uncertainty of available data and assessment methods. The hazard factor accounts for the seismicity levels at bridge sites and length of time of exposure to hazard. Structural and geotechnical aspects have been combined to determine the vulnerability of each bridge. Impacts quantify the consequences of bridge failure on safety and network functionality. The uncertainty premium accounts for the quality, variability and limitations of data and risk assessment methods used. The overall risk calculated for each bridge within a stock enables prioritisation of structures for monitoring and quick post-disaster assessment. The whole spectrum of approaches to bridge monitoring and condition evaluation comprises bridge specific monitoring data used for quick and accurate analyses for the most critical, high risk bridges; data sourced from wide-area strong motion arrays used for quick but less accurate assessment for medium risk structures; and traditional visual inspection based assessment of low risk bridges. A discrete scoring system was adopted and detailed tables that enable scoring the hazards, vulnerabilities, impacts and data and assessment uncertainties developed. The proposed methodology was applied to a selection of bridges from the city of Wellington, New Zealand to test its applicability and performance. A comparative study with another seismic risk assessment method was also conducted. The results showed that the methodology effectively prioritised bridges depending on seismic risk. The methodology was also able to determine if risk at a particular bridge site was predominantly related to hazard, structural vulnerability, geotechnical vulnerability or impact. The methodology is simple, quick and flexible and can be adapted based on the level of accuracy required. The uncertainty premium allows risk to be determined given variable data and assessment method quality which has the benefit of being able to tailor data collection and assessment to the needs of each network and available resources.

Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2017

During the last three decades, a large number of analytical methodologies have been developed for the seismic assessment of bridges and the derivation of bridge fragility curves. However, recently, the research focus has shifted on the derivation of bridge-specific fragility curves, recognizing the effect of different geometry, structural system, component and soil properties, on the seismic assessment results. In this context, a new, component-based methodology for the derivation of bridgespecific fragility curves has been proposed by the authors, with a view to overcoming the inherent difficulties in assessing all bridges of a road network and the drawbacks of existing methodologies, which propose usage of the same group of fragility curves for bridges classified within the same category. Therefore, the main issue addressed in this paper is to analytically determine capacity and demand in bridge-specific fragility analysis in the frame of the methodology previously proposed by the authors, aiming at application to realistically sized bridge stocks. Capacity (resistance) is calculated individually for each critical component with the aid of inelastic pushover analysis, quantifying damage in displacement terms based on the capacity curve and the correlation of global to local damage. Bridge piers, abutments and bearings are considered as the (seismically) critical components of a bridge system; piers of different types and characteristics, and different types of abutments and bearings are analysed and included in a database that provides case-specific limit state thresholds of component capacity. The effect of component parameters on limit state thresholds is therefore assessed, highlighting the differences according to the limit state and component considered. Demand is also calculated for each component using either inelastic response-history or elastic dynamic analysis, depending on the application scale (single bridge vs bridge stock), while uncertainties in both capacity and demand are quantified. Case-specific capacity and demand estimations using the proposed methodology are given here for three bridges having different structural systems, and the derived bridgespecific fragility curves are compared with fragility curves for all bridges classified within the same category, to assess the degree of over-or underestimation of the probability of damage when generic bridge classes are used.