•Modeled corrosion-fatigue degradation to assess life-long performance of RC bridges.•Rebar pitting corrosion and traffic-induced fatigue stresses form this degradation.•Degrading bridges are ...analyzed for earthquakes with substantial vertical components.•FE model of the bridge is updated at every life-cycle year to capture degradation.•Results portray higher life-cycle seismic vulnerability of all critical components.
Highway bridges, located in heavy traffic and corrosive environments, are prone to corrosion-fatigue degradation, due to which material properties of steel and concrete in bridge girders get altered and effective area of rebars reduces resulting in reduced flexural stiffness of girders. Consequently, exposed bridges become weaker to resist earthquake loads, particularly for the ones having three significant translational components. It is, therefore, important to evaluate life-long performance of bridges that suffer from corrosion-fatigue degradation and are subjected to seismic events having substantial vertical ground motions (VGMs). Such a threatening scenario for seismic safety of bridges has not been explored yet. The current study demonstrates the confronting role of corrosion-fatigue degradation and VGM on bridge seismic response through a representative multi-span RC bridge in Gujarat, India, and required information on corrosion, traffic, and seismic activities is acquired from appropriate sources. The degradation mechanism is modeled as a coupled phenomenon of pitting corrosion of rebar and traffic-induced fatigue stresses that give rise to fatigue cracks at deep pit locations of rebars in girders. Developed numerical model of the bridge composes of all essential features to accurately capture the gradual degradation along life-span and fluctuations in response of key vulnerable bridge components under horizontal and vertical excitations. Results suggest that ignoring the impact of this degradation mechanism and VGM can lead to higher seismic vulnerability of bridges and endanger their safety under future earthquakes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The continuously growing amount of seismic data collected worldwide is outpacing our abilities for analysis, since to date, such datasets have been analyzed in a human-expert-intensive, supervised ...fashion. Moreover, analyses that are conducted can be strongly biased by the standard models employed by seismologists. In response to both of these challenges, we develop a new unsupervised machine learning framework for detecting and clustering seismic signals in continuous seismic records. Our approach combines a deep scattering network and a Gaussian mixture model to cluster seismic signal segments and detect novel structures. To illustrate the power of the framework, we analyze seismic data acquired during the June 2017 Nuugaatsiaq, Greenland landslide. We demonstrate the blind detection and recovery of the repeating precursory seismicity that was recorded before the main landslide rupture, which suggests that our approach could lead to more informative forecasting of the seismic activity in seismogenic areas.
•A State-of-the-art review on the seismic response and design of tunnels is presented.•Emphasis is placed on recorded responses of actual tunnels during past earthquakes.•Relevant recent experimental ...and numerical studies are discussed.
The paper presents a state-of-the-art review of the current understanding of the seismic behaviour of tunnels. Emphasis is placed on recorded responses of actual tunnels during past earthquakes, as well as relevant experimental studies. In particular, the observed seismic performance of tunnels is initially discussed, by providing cases of reported damage during past earthquakes. This is followed by a review of the current monitoring systems for this infrastructure, which can be used to create future case studies based on actual recordings of the seismic response. Subsequently, the paper provides a summary of relevant experimental studies that took place in the centrifuge or on shaking tables, followed by a short discussion of current analytical models, simplified methods and numerical schemes for the seismic analysis and vulnerability assessment of tunnels. Throughout the presentation, the current overall gaps in understanding the seismic response of tunnels are identified in an attempt to stimulate further work in these areas by the research community.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A number of Nuclear Power Plants (NPPs) in India are coming up in soft soil condition particularly on alluvium in active seismic zone on Combined Piled-Raft Foundation (CPRF). So far, no study has ...been reported considering nonlinearity of soil for the NPP structures founded on CPRF considering earthquake loads.
In the present study, the dynamic responses of raft, pile group and CPRF of a NPP are investigated by simulating the nonlinear finite element model. The effects of nonreflecting boundary condition, pile-soil-interaction by the embedded constraint, raft-pile interaction by the tie constraint and raft-soil-interaction by the penalty constraint, were considered. The material nonlinearity of soil was taken into account using an advanced constitutive model Drucker-Prager with cap plasticity. The geometrical nonlinearity is also considered using the concept of the contact surface. Thus, a complete 3D finite element numerical model of a nuclear structure considering raft-pile-soil-structure interaction (RPSSI) for nonlinear seismic analysis is developed. The validation is carried out by comparing the results from the present study with experimental and numerical results available in the literature. Nonlinear analyses of raft, pile group and CPRF in the time domain finite element formulation carried out and results are compared with that using the linear analysis.
A comparison of two analyses shows that linear analysis underestimates the response of soil, piles and structure. The effect of type of boundary used in the analyses is significant. It was also observed that the response of NPP structure is significantly affected by the type of foundation used under the superstructure. The effect of SSI is examined with two major novelty i.e. (a) Effect of CPRF (b) Consideration of Nonlinearity of Soil. Effect of frequency of excitation and PGA of earthquake motion is examined. This study indicates the importance of CPRF over the raft foundation and pile group foundation for the design of nuclear power plants. Also, it examines the effects of nonlinearity on the response.
•Advantage of using Combined Pile-Raft-Foundation (CPRF) for Nuclear Power Plant (NPP) Structures.•Three-Dimensional Finite Element Analysis of a Nuclear Power Plant founded on CPRF for Seismic Loads. Consideration of Raft-Pile-Soil-Structure Interaction (RPSSI).•Effects of Geometrical and Soil Nonlinearity on the response of Structure and of Foundation.•Comparison of Response of NPP Structure founded on Raft, Piles and CPRF.•Effect of CPRF on the response of NPP for different earthquakes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the present study four G+5 steel structures were modeled without bracings and having X, V bracings and diagonal bracings with foundation depth of 2m support conditions are assumed to be pinned at ...the bottom or at the supports/footings, seismic loads are applied as per IS:1893-2002 The structures having length = 28.2 m, width = 17m and height = 20m. The structures modeled in STAAD.Pro“structural analysis and design software by considering various loads and load combinations by their relative occurrence are considered the material properties considered are” Fe250 rolled steel sections structures were considered in seismic zones 2, 3, 4 and 5 X type bracings systems are observed to better in high seismic zones.
Distributed fiber-optical acoustic sensing (DAS) is a new and booming technology in seismic exploration. DAS technology has been gradually applied to the exploration of vertical seismic profile (VSP) ...due to its strong resistance to high temperature and pressure, high sensitivity, high precision (trace interval can be accurate to about 1 m), and so on. However, real DAS-VSP data are always contaminated by both random and coherent noises, which greatly affects the quality of DAS-VSP data. In order to suppress the background noise and increase the signal-to-noise ratio (SNR), a convolutional neural network (CNN) based on leaky rectifier linear unit (ReLU) and forward modeling is proposed and named L-FM-CNN. In terms of network architecture, Leaky ReLU is adopted as the activation function of CNN, which can enhance the recovery ability of trained CNN denoising model to the weak effective signals. As for the training data set, we construct a high-authenticity theoretical pure seismic data set for DAS-VSP data through the complexity of forward models and the diversification of physical parameters. In addition, we propose a new mean square error (MSE) loss function combined with an energy ratio matrix (ERM). The ERM can adjust the SNR between the signal patch and noise patch during the network training and thus increase the robustness of trained CNN denoising model for the DAS-VSP data with different SNRs, especially the DAS-VSP data with extremely low SNR. Both synthetic and real experiments prove the effectiveness of the proposed L-FM-CNN.
•Superelastic shape memory alloy (SMA) cables are comprehensively studied.•Thermal-mechanical characterisations of the SMA material are carried out.•A series of SMA cable specimens are tested under ...various cyclic loading protocols.•A simple yet effective numerical modelling method is proposed for SMA cables.•A prototype bridge employing SMA cables as restrainers is designed and analysed.
This paper reports a comprehensive study on the mechanical behavior, annealing (heat treatment) scheme, hysteretic modelling strategy, and potential seismic application of superelastic shape memory alloy (SMA) cables. The study commenced with the thermal-mechanical characterization of monofilament SMA wires, and in particular, the influence of annealing scheme on the mechanical and phase transformation characteristics of the material was revealed. A series of 7 × 7 SMA cable specimens were subsequently tested at room temperature under various cyclic loading protocols. It is observed, among other findings, that the SMA cables are able to reasonably “scale up” the satisfactory properties of the SMA wires, and the mechanical behavior of the SMA cables may be improved by annealing. Moderate annealing temperature and duration (i.e., 350–400 °C for 15 min) can generally increase the stiffness, energy dissipation, and form setting ability of the SMA cables considered in this study, whereas an overly high annealing temperature tends to compromise these characteristics. Following the experimental study, an effective numerical modelling approach is proposed which reliably captures the basic mechanical behavior of the SMA cables. A model bridge, where SMA cables are adopted as restrainers, is finally designed and analyzed to demonstrate the efficiency of the SMA components for seismic damage mitigation. The analysis result shows that the SMA-cable restrainers can effectively control the peak and residual displacements of the bridge girder, and make the bridge more resilient.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Deep intracontinental earthquakes are poorly understood, despite their potential to cause significant destruction. Although lower crustal strength is currently a topic of debate, dry lower ...continental crust may be strong under high-grade conditions. Such strength could enable earthquake slip at high differential stress within a predominantly viscous regime, but requires further documentation in nature. Here, we analyse geological observations of seismic structures in exhumed lower crustal rocks. A granulite facies shear zone network dissects an anorthosite intrusion in Lofoten, northern Norway, and separates relatively undeformed, microcracked blocks of anorthosite. In these blocks, pristine pseudotachylytes decorate fault sets that link adjacent or intersecting shear zones. These fossil seismogenic faults are rarely >15 m in length, yet record single-event displacements of tens of centimetres, a slip/length ratio that implies >1 GPa stress drops. These pseudotachylytes represent direct identification of earthquake nucleation as a transient consequence of ongoing, localised aseismic creep.
•An advanced FE non-linear modelling of X-Lam timber buildings is presented.•Shaking-table tests of X-Lam timber buildings were simulated with good results.•Parametric analyses on friction effect and ...strength domain in fasteners are shown.
This paper presents an advanced FE modelling of cross-laminated (X-Lam) timber buildings for non-linear dynamic analyses. The model has been used to reproduce the experimental results of the shaking table tests carried out in Japan within the SOFIE project on the 3- and 7-storey full-scale timber buildings. The X-Lam timber panels have been schematized with linear-elastic shell elements, whereas all metal connectors (hold-downs, angle brackets, screws) have been described with 3-DOFs non-linear hysteretic springs. The hysteretic law has a trilinear backbone curve, and is characterised by pinching, post-peak softening, strength and stiffness degradation. The approximating hysteretic laws of the springs have been calibrated on the experimental cyclic tests carried out on each single metal connector. Additional features of the model are the possibilities to account for friction at the interface between upper and lower X-Lam panels, and for a strength domain between shear and tensile force in the metal connectors. Due to the lack of experimental results, these variables have been identified via parametric study so as to reduce the difference between the numerical prediction and the experimental result of X-Lam single walls loaded with cyclic horizontal load. The experimental–numerical comparisons of the shaking table tests demonstrate the capacity of the model to capture the seismic responses of both buildings with errors within 20% in relative acceleration and 7% in roof displacement. Friction has been found to significantly affect the seismic response as it reduces the peak top displacement up to 31%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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