Analysis on the Time-Varying Fragility of Offshore Concrete Bridge

For offshore bridges, the most prominent problem in the whole life cycle is that it is in an earthquake prone zone and an offshore corrosion environment at the same time. A nonlinear dynamic analysis model is set up for an offshore multispan and continuous rigid frame bridge based on the OpenSEES platform. The fragility surface of the bridge pier, bearing, bridge platform, and system are established by selecting a reasonable damage constitutive model of the material durability and a damage index analysis that studies the damage of the bridge durability to time-varying seismic fragility of bridge components and the system of the whole life cycle in offshore environment. The results show that the durability damage will lead to a constant decline in seismic capacity of the pier and an increase of the seismic demand under earthquake action as well as the probability to reach the ultimate failure state; compared to high piers, a low pier is more vulnerable to the offshore corrosion environment; the seismic fragility of bridge platform is higher than that of simply bearing; and the influence of offshore corrosion on environment is relatively large. With the prolongation of service period, the effect of durability damage on the seismic fragility of bridge system cannot be ignored in the coastal environment and it is necessary to make a reasonable evaluation on the seismic fragility of bridge structure during the whole life period.

Scour-dependent empirical fragility modelling of bridge structures under earthquakes

Fragility analysis is often employed to evaluate the vulnerability of structures subject to strong earthquakes, and in recent years, it further becomes one of the basic components for assessing the seismic resilience of civil structures and infrastructure systems. For river-crossing bridges that are exposed to both strong earthquakes and flooding events, a significant risk to bridge structures is the conjunct effects of seismic excitation and bridge scour. However, how to consider scour as a secondary hazard in performing fragility analysis and how to achieve balance among physical complexity, simplification and analytical rigour are not fully addressed in the literature. Extended from the traditional fragility modelling and incremental dynamic seismic analysis, a scour-dependent empirical fragility modelling approach is proposed in this article. In the proposed model, the model parameters are associated with scour depths in terms of quadratic polynomials, which provide great flexibility to consider the complex effects of bridge scour. Numerical analysis based on a simple two-span bridge model with pile foundations demonstrates the effectiveness and accuracy of the proposed approach. The fragility surface generated in this work can be used to assess the seismic resilience of scoured bridge under earthquake loads.

Multi-hazard fragility analysis for fluvial dikes in earthquake- and flood-prone areas

The paper presents a methodology for the multi-hazard fragility analysis of fluvial earthen dikes in earthquake- and flood-prone areas due to liquefaction. The methodology has been applied for the area along the Rhine River reach and adjacent floodplains between the gauges at Andernach and Düsseldorf. Along this domain, the urban areas are partly protected by dikes, which may be prone to failure during exceptional floods and/or earthquakes. The fragility of the earthen dikes is analysed in terms of liquefaction potential, characterized by the factor of safety estimated using the procedure of Seed and Idriss (1971). Uncertainties in the geometrical and geotechnical dike parameters are considered in a Monte Carlo simulation (MCS). Failure probability of the earthen structures is presented in the form of a fragility surface as a function of both seismic hazard and hydrologic/hydraulic load.

Multi-hazard fragility analysis for fluvial earthen dikes in earthquake and flood prone areas

The paper presents a methodological framework for multi-hazard fragility analyses for fluvial earthen dikes in earthquake and flood prone areas. The methodology and results are an integral part of the multi-hazard (earthquake-flood) risk study implemented within the framework of the EU FP7 project MATRIX (New Multi-Hazard and Multi-Risk Assessment Methods for Europe) for the area around Cologne, Germany. The study area covers the Rhine River reach and adjacent floodplains between the gauges Andernach and Düsseldorf. Along this domain, the inhabited areas are partly protected by earthen embankments (dikes or levees), which may be prone to failure in case of exceptional floods and/or earthquakes. The main focus of the study is to consider the damage potential of the dikes within the context of the possible interaction between the two hazards. The fragility of the earthen dikes is analyzed in terms of liquefaction potential characterized by the factor of safety. Uncertainties in the geometrical and geotechnical dike parameters are considered by using a Monte Carlo approach. The damage potential of the earthen structures is presented in the form of a fragility surface showing the damage probability as a function of both seismic ground shaking and flood water level. The obtained results can be used for multi-hazard risk assessment in earthquake and flood prone areas and, in particular, are intended for comprehensive risk assessment in the area around the city of Cologne.

Structural Vulnerability Assessment of Historical Buildings in Turkey

Structural Vulnerability assessment of historical buildings is very important to carry them to the future. Turkey is a rich country in terms of historic masterships mostly from Ottoman Empire, such as mosques, bathhouses, churches and aqueducts. Especially mosques are the common historical structures in turkey. Therefore, in the present study, structural vulnerability assessment of historical mosques in Turkey was carried out. One of the existing ones is considered as a sample building and structural vulnerability assessment was carried out on this building. The sample building was selected as Konak Mosque located in Izmir, Turkey. The mosque was structurally investigated through advanced approaches. The mosque, constructed in 1755 by Ottoman at very central location close by the clock tower, is little one decorated with blue tiles. The mosque is also nearby a historical bazaar where the main historical business stream line is located. Konak Mosque is one of these new styles in that age. It can be named as a signature historical building representing Islamic minimalist oriented architecture with its unique octagonal plan. In the present study, the building was modelled by using the Finite Element Modelling (FEM) software, SAP2000. Time history analyses were carried out using 10 different ground motion data. Displacements, base shear and stress values were interpreted and the results were displayed graphically and discussed. For probabilistic seismic risk assessment, fragility analyses were also carried out and the fragility curve and surface were sketched for the mosque. Saddle point was determined on the fragility surface.