Helmut Wenzel

One of the most promising computational methods in the field of Structural Health Monitoring is the Finite Element Model Updating. The VCUPDATE solution presented in this work is a Scilab code performing the iterative updating algorithm interfaced with a Finite Element code (OpenSees or ANSYS) executing the numerical analysis. The code is applied to the damage detection on beam structures. At first, a simple case numerically generated by OpenSees is investigated. Subsequently, using experimental test data, the code is applied to a real structure by using OpenSees as well as ANSYS.

The concept of value of information (VoI) enables quantification of the benefits provided by structural health monitoring (SHM) systems – in principle. Its implementation is challenging, as it requires an explicit modelling of the structural system’s life cycle, in particular of the decisions that are taken based on the SHM information. In this paper, we approach the VoI analysis through an influence diagram (ID), which supports the modelling process. We provide a simple example for illustration and discuss challenges associated with real-life implementation.

The most frequent disasters in Western Saudi Arabia are flash floods, earthquakes and volcanism, especially submarine volcanism potentially causing tsunamis in the Red Sea and submarine mass movements, dust storms and droughts. As the consequences and effects of the climate change are expected to have an increasing impact on the intensity and occurrence of geohazards as flash floods, length of drought periods, or dust storms, the systematic, continuous monitoring of these hazards and affected areas using satellite data and integration of the results into a geographic information systems (GIS) database is an important issue for hazard preparedness and risk assessment. Visual interpretation and digital image processing of optical aerial and satellite images, as well as of radar images, combined with Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Shuttle Radar Topographic Mission (SRTM) and Advanced Land Observing Satellite (ALOS) PALSAR DEM data are used in th...

In the IRIS project (European 7 th framework program) we have designed an original experimental setting for assessing the structural fragility of thick shear-walls. The main motivation is to improve the understanding of the non-linear behaviour under seismic loads of structures typical for the existing NPPs. In this context it is not only important to assess the ultimate capacity of a structure, but also its dynamic response in the "moderate damage" regime relevant for the verifications of components' fragilities through the FRS (Frequency Response Spectra). The dynamic response of structures of interest (e.g. electrical buildings) is essentially determined by the behaviour of the walls loaded in shear. The main specificity of the shear-wall of a nuclear installation is its much higher thickness than in the conventional civil structures. Many experimental campaigns (pseudo-dynamic or shaking table tests) were already done in this area, also at CEA and JRC, but so far m...

Bridge weight and traffic loads as well as braking and wind forces generate a number of different forces that must be transmitted to the ground through bridge piers and abutments. This is the task of bridge bearings, designed, manufactured and installed to permit movements and torsional effects caused by traffic, temperature variations, pre-stress, shrinkage and creep. Bridge bearings are therefore critical components of a bridge structure and demand high quality standards. An ongoing increase of traffic volume, higher cruising speeds and more flexible structures result in a redefinition of requirements for bearing systems. Furthermore the ambitions and challenges of bridge engineers to exceed not even finalised constructions in their dimensions and technical performances are also transferred to bridge bearing manufacturers. The lack in reasonable technologies to meet these extreme product specifications mainly results in expensive custom-made products with reduced lifetime performa...

Asset management depends on well-defined rules and standards for general application. Research results often represent the state of science in specific sections of specific cases. Standardization needs a downgrade of scientific work towards generally applicable specifications. This often leads to irritation in the scientific community fearing that their most interesting results are not specifically appreciated. This conflict makes standardization sometimes difficult.COST action TU1406 is devoted to harmonizing the state of science and technology and to bring all involved disciplines into the process. The results produced are of value for a number of standards on ISO, CEN and National level. This represents another difficulty, namely, to find the right place in any of the organizations and to identify the most suitable technical committee and code.This contribution reports on the experiences made with various committees and the results achieved. It soon became clear that specific par...

Asset management of signature bridges requires innovative approaches. Decision making cannot follow available codes and standards because these do not cover the extraordinary size and importance of these assets. Decision making in asset management shall be based on reliable data and prediction technologies. In order to ensure safety, durability and operability, information on the structural performance of the respective bridge is required. Monitoring producing information on the performance of these structures has become mature after intensive research and development funded by the European Commission. Most of the parameters that describe bridge performance can now reasonably be monitored. The paper includes an example of successful implementation, refers to a useful classification and specifies the applicable standards that can provide a framework for risk-based asset management approaches.

In the current research structural health monitoring is considered for addressing the critical issue of post-earthquake damage detection. A non-standard approach for damage detection via acoustic emission is presented -acoustic emissions are monitored in the low frequency range (up to 120 Hz). Such emissions are termed high-frequency transients. Further a damage indicator defined as the Time-Ratio Damage Indicator is introduced. The indicator relies on time-instance measurements of damage initiation and deformation peaks. Based on the time-instance measurements a procedure for estimation of the maximum drift ratio is proposed. Monitoring data is used from a shaking-table test of a full-scale reinforced concrete bridge pier. Damage of the experimental column is successfully detected and the proposed damage indicator is calculated. Keywords—Acoustic emission, Damage detection, Shaking table test, Structural health monitoring, High-frequency transients.

A method for the estimation of the ductility demand on reinforced concrete piers during ground seismic shaking is proposed. The required input is the measurement data from a structural health monitoring system within the time window of the seismic event. The procedure relies on detection of high-frequency transients related to damage and their distance forward in time to the closest deformation extrema. A formulation is proposed which relates these measurements to the ductility demand on the pier. A step-by-step description of the procedure is provided along with a case study implementation on an experimental reinforced concrete column. The ductility demand is estimated and compared with the one obtained from the experimental force–deformation curve.

ABSTRACT Bridges are ageing and traffic is growing, which creates a demand for accurate fatigue life assessment. The Europabrücke – a well known Austrian steel bridge near Innsbruck, opened in 1963 - is one of the main alpine north-south routes for urban and freight traffic. It represents a bridge generation, where bridge designers acted on a maxim of building material economisation. A long-term preoccupation of VCE with BRIMOS (BRIdge MOnitoring System) on the Europabrücke (since 1997) with regard to fatigue problems and possible damage led to the installation of a permanent monitoring system in 2003. Since that time a lot of investigations and additional special measurements were devoted to innovative, mainly monitoring-based fatigue assessment. As life-time predictions in modern standards depend on lots of assumptions, the emphasis is to replace those premises – referring to loading - by monitoring. • Basically all bridge structures on this highway belong to the same bridge generation, all subjected to the same loading history and all of them are facing evident fatigue problems these days. As the long-term investigations are following the issue of fatigue, it is focused on this limit state of serviceability instead of usually followed studies dealing with ultimate limit state (adjustment factor  linked approach). • This approach deals with real loading impact and its consequences in terms of ageing at the same time. • A tool providing real loading configurations and corresponding loading intensities (tonnages) for continuative fatigue calculations on existing structures was developed. • It was not aspired to develop a completely refined model for every relevant structural detail. This is the reason, why no axle loads approach was followed (according to common practice). Instead of this a so-called damage equivalency parameter was derived. • The developed tool can be immediately applied for relevant cases and related structural analysis. The model is based on the outer bridge span next to the uphill abutment, as it was proven to be the most influenced span by freight traffic. It is composed of real loading configurations and the real level of loading intensity (taken from a dynamic traffic-weight registration system) - both linked to their individual frequency of occurrence. To discuss and to compare the resulting impact with regard to damage accumulation, two most appropriate fatigue-models from EC1-2 were chosen.

ABSTRACT Degradation of structural components is a fact. In order to apply these changes over lifetime in precise cost models a standardized degradation law is desired. Standardization particularly helps in a competitive environment like construction to apply innovative technologies. In CEN-workshop 63 “Condition, Determination for Integrated Lifetime Assessment of Constructed Facilities and Components” a generic degradation law has been developed. It serves to determine the design life or the residual life of existing structures, helps to assess the real degradation process and enables the development of optimized maintenance plans.

ABSTRACT Versagensmodelle hoher Komplexität sind notwendig, um das Verhalten kritischer Infrastrukturelemente zu beschreiben. Dynamische Messungen haben wesentlich zu einem besseren Verständnis der Systeme geführt. Die Systemidentifikation wird jedoch zumeist im linearen Bereich durch ambiente Messungen durchgeführt. Im IRIS-Projekt werden zahlreiche Großversuche durchgeführt, bei denen Systeme auch bis in den nichtlinearen Bereich belastet werden. Dies verbessert das Verständnis, wie ambiente Ergebnisse in den nichtlinearen Bereich extrapoliert werden können. Der Beitrag gibt einen Überblick über die durchgeführten Experimente dieses Projektes und die daraus gewonnenen Erkenntnisse. Behandelt werden unter anderem: • Zerstörungsversuch an Rohrleitungen im Labor • Zerstörender Versuch an Brücken im Feld (Straße) • Zerstörungsfreier Versuch an Brücken im Feld (Bahn) • Großversuch an Schubwänden (Wandstärke 40 cm) im europäischen Forschungszentrum JRC

ABSTRACT The nature and purpose of an investment and its operational environment have a decisive influence on the type of assets required to achieve given objectives. These influencing factors need to be considered when an asset management system is implemented. The proposed system for infrastructure assets follows the principles, concepts and terminology relating to assets, asset management and asset management systems as specified in ISO55000 (Asset management – Overview, principles and terminology). In ISO31000 (Risk management-principles and guidelines) it is stated that “internal and external factors and influences that make it uncertain whether or when they will achieve their objectives” is a challenge to organi-zations. The effect this uncertainty has on organizations objectives is “risk”. This paper follows the risk framework specified in ISO31000 which is complemented with object specific risk management plans that serve particular objectives, context, structure, operations, processes, functions, services and specific practices employed in this sector. A first attempt to standardize an aging function has been performed in the IRIS Project in CWS 16663, which has been taken over by many standard institutions al-ready (i.e. USA, Japan, Russia, UK, Germany and many others).

Risk management based on probabilistic approaches is becoming more and more the current practice. The performance of a probabilistic hazard assessment required knowledge on materials, systems and properties. Our constructed environment is, unlike the automotive or aeronautic sector, characterized by a wide scatter of the real quantities. Monitoring is able to identify the systems in a way that allows reducing the uncertainties considerably. Sorrow system identification is able to reduce the systematic errors to less than 1%. Extensive studies in the past have revealed that particular concrete structures can deviate over 30% from the values as planned by the designer. Fortunately these deviations are mainly in the save direction. This knowledge can help to adjust the assessment of our structures to justified level. In the light of the problem with bridges rated deficient in an extent that is not manageable anymore, this identification could solve part of the problem.The monitoring campaigns carried out at more than 400 bridges in the past years have shown that over 95% of the bridge stock shows higher capacities than anticipated. The few problems remaining can easily be approached by relevant retrofit measures. It has been demonstrated that the existing budgets for bridge maintenance and retrofit are actually sufficient, in case that the money only has to be spent on those structures absolutely requiring an intervention.

Conventional lifecycle models are based on the information provided by the respective databases. In order to introduce objective values for assessment monitoring results are utilized. In the following description this process is elaborated. The presented approach has been developed for Central European conditions and the related database and information structure. Nevertheless the principle can be applied globally when the respective interfaces are fitted for the specific purpose

System identification methodologies have reached a mature state. Damage detection has been the key topic of recent research work in this field. Learning from evolution of dynamic characteristic throughout the damage process, one can validate damage detection methods or set benchmark studies for typical aging processes of a structure. When dynamics gain a guiding role in the behaviour of a structure our conventional approaches fail. The influence of the various non- linearities can not be neglected anymore. This paper is determined to describe a number of these non-linearities and their embedment into the system identification procedure. The results show that changes of natural frequencies are clearly visible, but not a reliable identification approach.Identifying the non-linearities helps to identify damage at an early stage and enables even damage quantification, location and most important remaining lifetime prediction.