The determination of spatially‐varying broadband ground motions is a prerequisite for the seismic analysis of dams. However, generating realistic ground motions at a specific dam site remains a ...challenge. Source‐to‐structure simulation, which considers source, propagation path, and site, is a promising way to reasonably synthesize site‐specific ground motions. This paper proposes a practical framework for the seismic analysis of dams based on a deterministic numerical source‐to‐structure simulation. The site‐specific broadband ground motions are generated by a physics‐based 3D numerical simulation using the spectral element method (SEM) in a coarse mesh, while the nonlinear dynamic response of the dam is simulated by the finite element method (FEM) in a fine mesh. The proposed framework bridges the gap between wavefield simulation and seismic analysis of dams. The seismic response analysis of Pacoima dam during the 1994 Northridge earthquake was conducted as a case study, making it the first demonstration of a complete source‐to‐structure simulation for realistic concrete dams using the purely numerical method. Results show that the calculated seismic response agrees with the observation, thus indicating the utility of the proposed framework for source‐to‐dam simulation.
Summary
The intrinsic vulnerability of masonry structures to seismic events makes structural health monitoring of the utmost importance for the conservation of the built heritage. The development of ...piezoresistive bricks, also termed smart bricks, is an innovative technology recently proposed by the authors for the monitoring of such structures. Smart bricks exhibit measurable variations in their electrical properties when subjected to external loads or, alternatively, strain self‐sensing capabilities. Therefore, the deployment of a network of smart bricks into a masonry structure confers self‐diagnostic properties to the host structure. In this light, this paper presents a theoretical investigation on the application of smart bricks to full‐scale masonry structures for seismic assessment. This includes the study of the convenience of providing electrical isolation conditions to the sensors, as well as the effectiveness of smart bricks when installed into either new constructions or in pre‐existing structures. Secondly, numerical results are presented on the seismic analysis of a three‐dimensional masonry building equipped with a network of smart bricks. Finally, in order to map the strain field throughout the structure exploiting the outputs of a limited number of sensors, an interpolation‐based strain reconstruction approach is proposed.
•The Improved Fish-Bone model for seismic analyses of frame buildings is introduced.•It can estimate the response history of storey shears, drifts and accelerations.•Pushover curves, IDA curves, and ...fragility functions are sufficiently accurate.•The IFB model is computationally efficient and robust.•The use of the IFB model is currently limited to 2D problems.
The improved fish-bone (IFB) model for seismic analysis of older and contemporary reinforced concrete frames is proposed by introducing a new procedure for the estimation of parameters of structural elements of the fish-bone model. The procedure makes it possible to approximately account for the importance of structural elements on the seismic response of a frame building and the effect of potential redistribution of demands between structural elements of the frame building. Firstly, the IFB model is described. Follows demonstration of its capability by simulating the response history of storey shears, storey drifts and storey accelerations of selected pseudo-dynamically tested frames. Finally, it is shown that the IFB models can provide pushover curves, the corresponding damage states and fragility functions based on response history analysis which are very similar to those obtained by the conventional multi-degree-of-freedom models. The capability of the IFB model with respect to conventional fish-bone model is also demonstrated by the pushover analysis. It can be observed that the IFB model significantly improves the simulation of the older reinforced concrete frames, which do not fulfil the strong column – weak beam concept, and the frames for which the columns or beams of one storey of a frame building differ significantly from each other. Additional research is needed to extend the capabilities of simplified structural models to plan irregular frame building.
The questions asking whether the Sun shrinks with the solar activity and what causes this have been a subject of debate. Helioseismology provides a means to measure with high precision the radial ...displacement of subsurface layers, the so-called "seismic radius," through the analysis of oscillation frequencies of surface gravity (f) modes. Here, we present results of a new analysis of 21 years of helioseismology data from two space missions, the Solar and Heliospheric Observatory and the Solar Dynamics Observatory, which allow us to resolve previous uncertainties and compare variations of the seismic radius in two solar cycles. After removing the f-mode frequency changes associated with the surface activity, we find that the mean seismic radius is reduced by 1-2 km during the solar maxima and that most significant variations of the solar radius occur beneath the visible surface of the Sun at a depth of about 5 2 Mm, where the radius is reduced by 5-8 km. These variations can be interpreted as changes in the solar subsurface structure caused by the predominately vertical ∼10 kG magnetic field.
The prediction of volcanic eruptions and the evaluation of associated risks remain a timely and unresolved issue. This paper presents a method to automatically classify seismic events linked to ...volcanic activity. As increased seismic activity is an indicator of volcanic unrest, automatic classification of volcano seismic events is of major interest for volcano monitoring. The proposed architecture is based on supervised classification, whereby a prediction model is built from an extensive data set of labeled observations. Relevant events should then be detected. Three steps are involved in the building of the prediction model: (i) signals preprocessing, (ii) representation of the signals in the feature space, and (iii) use of an automatic classifier to train the model. Our main contribution lies in the feature space where the seismic observations are represented by 102 features gathered from both acoustic and seismic fields. Ideally, observations are separable in the feature space, depending on their class. The architecture is tested on 109,609 seismic events that were recorded between June 2006 and September 2011 at Ubinas Volcano, Peru. Six main classes of signals are considered: long‐period events, volcanic tremors, volcano tectonic events, explosions, hybrid events, and tornillos. Our model reaches 93.5% ± 0.50% accuracy, thereby validating the presented architecture and the features used. Furthermore, we illustrate the limited influence of the learning algorithm used (i.e., random forest and support vector machines) by showing that the results remain accurate regardless of the algorithm selected for the training stage. The model is then used to analyze 6 years of data.
Key Points
We propose a supervised process for the automatic classification of volcano seismic signals
We test and validate the proposed architecture on 6 years of continuous seismic recordings from a short‐period seismic station
The automatic classification scheme performs better than human analysts in a crisis situation
The available theoretical models for evaluating seismic active earth pressures are limited to plane strain analyses and linear failure criterion. To fill this research gap, with a combination of the ...kinematical approach of limit analysis, the spatial discretization technique as well as the pseudo-static approach, this work develops a discretized three-dimensional failure mechanism of sloping backfills that is composed of an end cap and a central plane-strain insert to estimate the seismic active earth pressure coefficient under nonlinear failure criterion. Compared with the existing three-dimensional kinematically admissible failure mechanisms, the developed one has three significant merits: (1) the normality condition is strictly satisfied in the generation of the end cap; (2) the work rates can be computed by a summation of elementary work rates conveniently instead of tedious integral schemes; (3) the considerations of the nonlinear failure criterion and the sloping backfill. Comparisons with the existing upper bound solutions and experimental results in terms of active earth forces or active earth pressure coefficients are conducted to verify the proposed model. Parametric studies are performed to study the influences of model parameters, including the seismic coefficient, the sloping angle of backfills as well as the nonlinear parameters, on the active earth pressure coefficients.
•The limits of traditional PBSD requirements for mass timber building is presented.•The process to combine traditional design and GA optimization is illustrated.•Two examples are designed and were ...shown to result in different designs.
This paper presents a rational procedure to optimize design for mass timber rocking wall systems utilizing a genetic algorithm (GA) beyond typical displacement-based design metrics for wood buildings. Traditional displacement-based design is limited to simple displacement targets, with optimization techniques (GA), it is feasibly to consider more performance chrematistics (e.g. costs, serviceability, etc.). By formulating drift targets and other structural design limit states within an elimination step of the GA optimization process, the method proposed here optimizes rocking wall design with multiple criteria that factor much more than lateral displacement targets in the seismic analysis. This type of optimization is difficult to perform using traditional manual trial-and-error approaches. An existing simplified nonlinear time-history simulation model (validated through full-scale shake table test data) of a wood rocking wall is employed in this process. The design for an example building in Seattle with a six-story rocking wall is presented using the proposed procedure. The results revealed that the optimization of the mass timber rocking wall lateral system can be achieved in a reasonable time frame using the proposed method. Even though the same drift limits were applied, final designs produced by GA varied, depending on the other optimization objectives. This demonstrates how the seismic design of wood rocking wall systems could be readily improved with computerized optimization tools that factor in other aspects of the design including cost.
Prior to implementing retrofitting measures for seismic action, it is necessary to evaluate the global capacity of unreinforced masonry (URM) buildings. Even with simplified assumptions, equivalent ...frame (EF) modeling adequately captures global responses and failure mechanisms in existing buildings, making it a popular modeling strategy among structural engineers. However, macro‐elements employed in the EF modeling of URM walls consider in‐plane (IP) and out‐of‐plane (OP) behaviors separately by decoupling their interaction and require independent verification for OP failure involving limit analysis. Such decoupling of interaction is justifiable if proper wall‐wall/wall‐floor connections and rigid‐diaphragm action of slabs are ensured; however, OP failure is likely a result of inadequate connections. Multiple components of ground motion excitation and plan eccentricity in buildings can activate bidirectional interaction in such circumstances. Due to OP damage, the interaction reduces the full IP strength of a URM wall, resulting in overestimating its lateral capacity. This paper proposes a frame‐like 3D macro‐element incorporating the effect of OP action on the IP shear response of URM piers under static and monotonic lateral loads. Only two parameters modifying IP shear stiffness and capacity are required to account for the interaction. Analytical expressions for the interaction parameters are proposed from a detailed micro‐modeling study. The paper also demonstrates, within the EF modeling, the applicability of the proposed macro‐element for seismic analysis of regular URM shear walls with openings.
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