László Gergely Vigh

Seismic Performance of Conventional Girder Bridges in Moderate Seismic Regions

AbstractThe majority of continuous girder bridges in regions of moderate seismicity were designed before the introduction of modern seismic codes that prescribe seismic design verification for such structures. The objective of this study is to investigate the seismic performance of typical Hungarian continuous girder bridges through a parametric study. A design space is described by a set of eight parameters. More than 10,000 bridge archetypes are designed without any seismic verification to mimic the design of conventional bridges. The seismic performance of each archetype is then evaluated with modal response spectrum analysis of a detailed finite-element model. The results highlight the vulnerability of piers and bearings and imply that the superstructures are not expected to fail under moderate ground motion intensities. Long bridges with short piers and large spans show the worst performance, especially if the number of fixed bearings in the longitudinal direction is small. This indicates the large i...

A methodology for the development of historical building archetypes for seismic performance assessment

The probabilistic estimation of the magnitude of historical earthquakes requires the analysis of actual building structures affected by those earthquakes. The analysis complicates because most of these buildings no longer exist or were greatly modified, present a great variety of features and the number of analysis for probabilistic assessment is high. As it is not practical to analyze all structures, an alternative is to use structural archetypes representing the affected buildings. This paper presents an approach to develop a quantitative framework for the generation of historical archetypes. The method is illustrated via the definition of a specific archetype for the study and assessment of the effects of the 1763 Komarom earthquake. The historical survey of Tata, Hungary, is assumed as representative of the region and one historical building is utilized to illustrate the archetypes evaluation process.

Seismic Reliability Assessment of Typical Road Bridges in Hungary

ABSTRACT Prior to modern seismic codes, several road bridges were not designed for earthquakes in many moderate seismic regions. The seismic performance of these bridges is questionable. A portfolio of 30 non-seismically designed bridges is compiled for seismic reliability assessment. Fragility analysis is conducted, and the reliability of each structure is determined considering typical moderate seismic areas. The study shows that slab and multi-girder bridges with elastomeric bearings perform worse, whereas girder bridges with conventional bearings and multi-girder bridges with monolithic joints have better behavior. It is also shown that seismic design per Eurocode 8 leads to a reliability index of ~2.

Seismic fragility assessment of integral precast multi-span bridges in areas of moderate seismicity

In lack of seismic provisions in the pre-Eurocode ages, most of the existing Hungarian bridges were not designed for seismic actions, therefore their seismic performance is questionable. The most commonly used structural type in highway construction is the integral precast multi-girder bridge. These bridges are typically constructed as continuous multi-support systems with monolithic joints at each support, thus their behavior may be significantly different from those applying simply supported beams and conventional bearings. A parametric fragility analysis of a wide range of different layouts is carried out using detailed and advanced non-linear numerical models. The results indicate that the abutment joints are highly vulnerable and piers are also critical for longer bridges. The study implies that without seismic design, integral precast multi-girder bridges are highly susceptible to pier shear failure, the probability of collapse is relatively high. The results also provide a solid basis for retrofit planning as well as for development of design concepts of newly built structures in moderate seismic zones.

On the European Norms of Design of Buckling Restrained Braced Frames

The application of buckling restrained braced frames is hindered in Europe by the absence of a standardized design procedure in Eurocode 8, the European seismic design standard. The presented research aims to develop a robust design procedure for buckling restrained braced frames. A design procedure is proposed by the authors. Its performance has been evaluated for buckling restrained braced frames with chevron type brace configurations using a state-of-the-art methodology based on the recommendations in the FEMA P695 document. A special numerical material model was developed within the scope of this research to represent the behavior of buckling restrained braces more appropriately in a numerical environment. A total of 24 archetype designs were prepared and their nonlinear dynamic response was calculated using real ground motion records in incremental dynamic analyses. Evaluation of archetype collapse probabilities confirm that the proposed design procedure can utilize the advantageous behavior of buckling restrained braces. Resulting reliability indices suggest a need for additional regulations in the Eurocodes that introduce reasonable structural reliability index limits for seismic design.

Plate Stability Verifications of Aluminium Plate Girders

The paper focuses on overall and local web plate buckling of longitudinally multi-stiffened aluminium plate girders subjected to compression, bending, shear and transverse loading. The authors completed wide-range bifurcation stability analysis by energy method. Based on the results of the completed parametric study, buckling coefficients are formulated, taking also into account the possible interaction of local and overall buckling. Modifications are proposed for the standard Eurocode calculations of critical loads. Modification in resistance calculation for web crippling is also proposed to take the beneficial effect of curved flange-to-web connection into account. Numerical model is developed for nonlinear static analysis. Virtual experimenting – considering actual material behaviour and imperfections – is invoked for the calibration of the model.

Conceptual Design of an Aluminium Bridge in Alma, QC

The City Council of Alma, Quebec, Canada intends to erect a new footbridge celebrating the 150-year anniversary of the city. Functioning as communal and cultural ground, an island will be built on the 100 m wide River Petite Décharge hosting a pedestrian area with pathways plants and artistic installations, being a symbolic landmark. The bridge has to provide connection between both the river sides and the island. Original and aesthetic design ideas for the bridge structure are searched. In the first phase of our work, preliminary study proposing 10 alternatives for the bridge was completed. The city has been selected three alternatives for further studies: double-arch classic bridge, classic cable stayed bridge with single pylon, artistic/industrial truss bridge with three lane decks. In the second phase of the work, we prepared the general preliminary design calculations, technical drawings, perspective drawings for the three selected versions. Common factor in all variants is the need and intent to apply advanced, state-of-the-art aluminium technology. The paper describes the evolution of the conceptual design of the bridge.

Long-Term Trends in Annual Ground Snow Maxima for the Carpathian Region

The current structural design provisions are prevalently based on experience and on the assumption of stationary meteorological conditions. However, the observations of past decades and advanced climate models show that this assumption is debatable. Therefore, this paper examines the historical long-term trends in ground snow load maxima, and their effect on structural reliability. For this purpose, the Carpathian region is selected, and data from a joint research effort of nine countries of the region are used. Annual maxima snow water equivalents are taken, and univariate generalized extreme value distribution is adopted as a probabilistic model. Stationary and five non-stationary distributions are fitted to the observations utilizing the maximum likelihood method. Statistical and information theory based approaches are used to compare the models and to identify trends. Additionally, reliability analyses are performed on a simple structure to explore the practical significance of the trends. The calculations show decreasing trends in annual maxima for most of the region. Although statistically significant changes are detected at many locations, the practical significance - with respect to structural reliability - is considerable only for a few, and the effect is favourable. The results indicate that contrary to the widespread practice in extreme event modelling, the exclusive use of statistical techniques on the analysed extremes is insufficient to identify practically significant trends. This should be demonstrated using practically relevant examples, e.g. reliability of structures.

Fragility Estimation and Comparison Using IDA and Simplified Macro-Modeling of In-Plane Shear in Old Masonry Walls

The estimation of fragility functions associated with dynamic structural analysis provides the probability of a certain damage state given an intensity measure. The presented paper discusses this technique regarding its application to a method to estimate the magnitude of historical seismic events relying on the behavior and damage in real historical structures. A bin of 50 seismic records is selected matching the Komarom hazard spectrum and applied with Incremental Dynamic Analysis to generate the damage state points of a 2D one-story frame numerical model developed using Opensees code and calibrated to simulate the in-plane shear behavior of historical old clay and adobe masonry infilled walls. A scaling technique is applied and a damage type identification strategy adapted to the material model are developed to perform Incremental Dynamic Analysis and efficient fragility function fitting in MATLAB. Results highlight considerable uncertainties regarding the calibration of the numerical model, material and geometric nonlinearities and seismic record selection in this procedure. Despite efficiency, the methodology application and overview suggest that a full probabilistic approach fragility function fitting using the background of seismic hazard analysis and reliability theory, providing a concomitant sensitivity analysis, is important to proceed with variables weight evaluation and account for uncertainties.