Search

Seismic response prediction is a challenging problem and is significant in every stage during a structure's life cycle. Deep neural network has proven to be an efficient tool in the response prediction of structures. However, a conventional neural network with deterministic parameters is unable to predict the random dynamic response of structures. In this paper, a deep Bayesian convolutional neural network is proposed to predict seismic response. The Bayes-backpropagation algorithm is applied to train the proposed Bayesian deep learning model. A numerical example of a three-dimensional building structure is utilized to validate the performance of the proposed model. The result shows that both acceleration and displacement responses can be predicted with a high level of accuracy by using the proposed method. The main statistical indices of prediction results agree closely with the results from finite element analysis. Furthermore, the influence of random parameters and the robustness of the proposed model are discussed. [ABSTRACT FROM AUTHOR]

The finite element model of suspension bridge was established according to the actual bridge engineering in Southwest area of China. In order to simulate the random ground motion model accurately and efficiently, the orthogonal random function ground motion modeling method based on Priestley evolution spectrum theory is adopted. The dimensionality reduction simulation of random ground motion is realized, and the simulated ground motion samples are input into the finite element model to carry out the time history analysis. Finally, the seismic response of the bearing and pylon is analyzed and important conclusions are drawn. [ABSTRACT FROM AUTHOR]

The evaluation of the seismic vulnerability of existing buildings is becoming very significant nowadays, especially for ancient masonry structures, that represent the cultural and historical heritage of our countries. In this research, the Cathedral of Santa Maria Assunta in Catanzaro (Italy) is analyzed to evaluate its structural response. The main physical properties of the constituent materials were deduced from an extensive diagnostic campaign, while the structural geometry and the construction details were derived from an accurate 3D laser scanner survey. A global dynamic analysis, based on the design response spectrum, is performed on a finite element model for studying the seismic response of the structure. Moreover, a local analysis is conducted to evaluate the safety factors corresponding to potential failure mechanisms along preassigned failure surfaces. Furthermore, pushover analyses are performed on macro-elements, properly extracted from the whole structure and with an independent behavior with regard to seismic actions. A novel model based on inter-element fracture approach is used for the material nonlinearity and its results are compared with a well-known classical damage model in order to point out the capability of the method. Finally, the results obtained with the three different models are compared in terms of seismic vulnerability indicators. [ABSTRACT FROM AUTHOR]

The topographic amplification effect has significant impacts on structural safety since it causes inconsistencies in seismic response. Previous studies on topographical influence focus on a certain point and cross-sections, which is insufficient to comprehensively understand the topographic amplification effect. Besides, few studies analyze the relationship between seismic response and ground motion frequency. Hence, this study aims to investigate the effects of topographic irregularity of the whole site, and explore the relationship between seismic response characteristics and signal frequency. An analysis procedure for modeling and meshing an actual 3D site is proposed by combining SolidWorks, SketchUp and Abaqus. Finite element method (FEM) is applied to simulate the seismic response. Results show that the site amplification and de-amplification are associated with topographic features. Specifically, the seismic responses of ravine and ridge areas could differ by a factor of two. However, acceleration response in ravine areas shows unusual amplification under input signal frequencies over 4 Hz. Besides, the frequency of input ground motion certainly affects the seismic site amplification. Specifically, in this study, the seismic response peaks when the input frequency is in the range of 0.4–0.8 Hz, which corresponds to the resonance frequency of the numerical model. In terms of frequency, site amplification showed a correlation between actual recordings and artificial signal inputs, but lower intensities are observed when actual records are input. Therefore, the engineering risk will be underestimated when the topographic irregularity and frequency characteristic of input ground motion are inappropriately considered. The findings of this study provide a new approach to investigate the actual 3D site amplification effects and shed new insight on regional seismic risk analysis. • A method for generating numerical models of irregular 3D terrain is proposed. • The correlation between the seismic response and topographic characteristics of the valley at the actual site is investigated. • Seismic site amplification is closely related to input signal frequency. [ABSTRACT FROM AUTHOR]

Liquid storage tanks are lifeline structures and strategically very important. Heavy damages or even collapse of these facilities subjected to strong earthquakes may cause disastrous consequences. In this paper, the seismic response of a multistage series liquid storage tank was simulated by a finite element method and verified by a scaled-down experiment. The structural flexibility of the tank and the liquid-structure coupling characteristics between the liquid and tank wall were considered in the research. A multimass-block and spring model was employed to be equivalent to the longitudinal vibration of the liquid in the storage tank. The relationships between the connection springs and the elements of the stiffness matrix were explicitly deduced. The seismic response analysis of a four-stage series liquid tank was carried out, and the acceleration response, the stress response of the tank, and the vertical vibration of the liquid were obtained. The experimental results are in good agreement with the simulation results, which verifies the effectiveness of the modeling method in this paper. [ABSTRACT FROM AUTHOR]

• Modeling uncertainties are incorporated into the failure fragility curves of substation equipment interconnected by rigid bus conductors. • Sensitivity analysis is carried out to identify the influential modeling parameters on the seismic response. • An efficient method based on the ET method is proposed to estimate response distributions and fragility parameters of the connected apparatuses. • A multi-hazard risk analysis is performed by presenting a rapid seismic risk framework based on the scenario sampling analysis and ET method. This study aims to evaluate the influences of modeling-related uncertainties on the seismic response and fragility function of the four vulnerable components of electrical substation equipment, taking into account the dynamic interaction between apparatuses via bus slider-rigid bus conductors. The 3D finite element model for interconnected disconnect switch- circuit breaker-current transformer-surge arrester system is developed in OpenSees software. A sensitivity analysis is conducted to evaluate and rank the importance of individual random variables on the seismic responses. To incorporate modeling uncertainties into the failure fragility function, probabilistic structural interconnected simulations are generated using the Latin hypercube sampling technique. The fragility curves for each apparatus in the connected system are derived using incremental dynamic analysis (IDA). An efficient procedure based on the endurance time (ET) method is presented for estimating response distributions and fragility parameters of the interconnected apparatuses while considering modeling uncertainty. The proposed approach provides acceptable results compared to those from the IDA while tremendously reducing computer run-time. This investigation also puts forth a rapid detailed seismic risk analysis framework using scenario sampling analysis. To this end, the ET response distributions are exploited as equipment response models within reliability-based risk analysis. Results indicate that the damping ratio and porcelain elastic modulus have a substantial effect on the seismic responses of equipment. In addition, modeling uncertainties affect the median and dispersion values of the failure fragilities by up to −5.9% and +22% on average for all equipment cases, respectively. According to the loss curves, it is observed that the circuit breaker contributes the greatest to the system's overall loss, whereas the surge arrester contributes the least. [ABSTRACT FROM AUTHOR]

Abstract The out-of-plane response is a complex and at the same time key aspect of the seismic vulnerability of masonry structures. It depends on several factors, some of which are the material properties, the quality of the walls, the geometry of the structure, the connections between structural elements and the stiffness of the diaphragms. During the last years, a wide variety of numerical methods has been employed to assess the out-of-plane behaviour of unreinforced masonry structures. Finite element macro-modelling approaches are among the most famous as they allow modelling large structures at a reasonable computational cost. However, macro-modelling approaches may result in a non-realistic representation of localized cracks and a dependency of the numerical solution on the finite element mesh. Mixed strain/displacement finite elements have been recently proposed as a remedy to the above numerical pathologies. Due to the independent interpolation of strains and displacements these finite element formulations are characterized by an enhanced accuracy in strain localization and crack propagation problems, being at the same time practically mesh independent. For these reasons, mixed finite elements are employed in this work for the out-of-plane assessment of unreinforced masonry structures, being at the same time their first real-scale application. A full-scale experimental campaign of two masonry structures, a stone and a brick one, subjected to shaking-table tests is chosen as reference benchmark. Their structural response under seismic actions is numerically assessed through nonlinear static analysis. The proposed approach is validated through the comparison of the numerical results with the experimental ones, as well as with the results obtained using standard irreducible finite elements. Highlights • Large-scale application of mixed strain/displacement finite element formulation. • Simulation of shaking table experiments on brick and stone masonry mock-ups. • The mixed formulation predicts the out-of-plane collapse mechanisms. • Mesh-dependency study using the standard and the mixed formulation. • The mixed formulation gives mesh-independent results without tracking procedures. [ABSTRACT FROM AUTHOR]

Stabilizing pile is widely used in the landslide controlling projects and shows excellent seismic performance under the action of earthquake. Therefore, in order to improve seismic design theory, it is of importance to study the seismic response characteristics of stabilizing pile based on elastic-plastic analysis. In view of this, elastic-plastic constitutive model was established to deduce the plastic zone of stabilizing pile. Based on elastic-plastic analysis, the seismic response characteristics and the influence of different section sizes, material strengths, and peak ground motion acceleration (PGA) were analyzed by ANSYS 3D. Resultantly, the elastic-plastic fourth-order tensor Cijklep was deduced, which can be used to calculate plastic strain of stabilizing pile under loading. Compared with Chinese code, the material of stabilizing pile working with elastic-plastic state will be decreased under the same section size and the same property. Furthermore, stabilizing pile is in the elastic stage at the beginning under the action of earthquake. With the increase of ground motion time, the section starts to exhibit elastic-plastic state and then the plastic zone expands gradually. Finally, the plastic zone runs through the whole section, resulting in the performance loss of the pile. In addition, under the different design parameters, pile shows different seismic response characteristics; namely, changing these parameters reasonably can improve the seismic design. [ABSTRACT FROM AUTHOR]

Bridge columns are known as the most vulnerable components of a bridge and operate as the core substructure elements of the bridge support system. Post-earthquake evidence reveals that large deformation and extensive damage of bridge columns are linked to the force and deformation capacity of the columns. Since research on the seismic vulnerability of bridges with various column shapes is limited, this paper aims to address this deficiency by evaluating the seismic performance of a variety of common column shapes. This analytical study involves assessing circular, rectangular, and oblong-shaped columns. Each shape of the column is tested as prismatic or flared along the column height as many of the bridges, constructed after 1970 in high seismic zone areas like California, are supported by flared columns. First, the study concentrates on assessment of several different column shapes as individual elements through both monotonic and cyclic pushover analysis. Second, a complete bridge system is investigated for the impact of the cross-section shapes and column flares on the fragility assessment findings. This article deals with the seismic vulnerability assessment of box-girder types bridges. A set of numerical bridge models that accounts for geometric and material uncertainties according to the California bridge characteristics is created in OpenSees. According to the results, oblong columns display less fragility compared to the other column shapes. The comparison of the seismic analysis for prismatic and flared columns shows the vulnerability of flared columns. The findings indicate that neglecting the effect of column shapes on the bridge fragilities leads to an unreliable estimation of the seismic risk and associated losses. [ABSTRACT FROM AUTHOR]

This paper presents two finite element modeling approaches for seismic evaluation of curved precast-prestressed concrete (PSC) I-girder bridges and compares the results in a statistical and graphical manner. These approaches, including area and spine models, were applied to a simply-supported, curved PSC I-girder bridge under an ensemble of 3D synthetic ground motions. Along with performing non-linear time history (NLTH) analyses of the bridge to capture its separate seismic response, the efficiency of each approach was evaluated with respect to execution time and each was compared. This comparison reveals that the seismic responses that were computed at low computational cost from the spine approach are reasonably analogous to those from the area model. Seismic fragility curves of a portfolio of curved PSC bridges using the spine approach are also created to assess their vulnerability and then compared to those gained from past studies. This comparison shows a reasonable agreement for the PSC portfolio. [ABSTRACT FROM AUTHOR]

Seismic protection of ancient masonry towers is a topic of great concern among the scientific community. A methodology for the seismic vulnerability assessment of all types of towers and slender unreinforced masonry structures (e.g., light houses and minarets) is presented. The approach is developed by four validated 3D FEM models representative of European towers. The models are subjected to linear elastic investigations to establish load carrying capacity and dynamic properties for validation against similar towers. Seismic simulations are developed through intensive nonlinear static pushover analyses. From the assessments, the failure modes and overall seismic response of the towers are obtained. Low tensile strength of masonry and large openings at belfries have significant influence on the seismic behavior, resulting in a quasi-brittle failure. All the towers presented an imminent high vulnerability to seismic actions. The few investigations reported in literature on the seismic behavior of towers are focused on in-plane behavior, disregarding out-of-plane behavior and toe crushing, both aspects are investigated in this paper. The more flexible towers are close to present toe crushing in both planes. The failure mechanisms are validated with reported post-earthquake observations on real damaged towers. [ABSTRACT FROM AUTHOR]

• SMA-based TMDs were proposed and optimized to control the seismic responses of wind turbine tower. • Effectiveness of SMA-based TMDs in the seismic response mitigation of wind turbine tower was investigated. • Control performances of SMA-based and linear TMDs were compared. This study proposes replacing the spring and dashpot elements in the conventional tuned mass damper (TMD) by shape memory alloy (SMA) wires to form an SMA-based TMD to control the seismic responses of wind turbine tower. An equivalent linearization method is adopted to optimize the initial stiffness of SMA-based TMD by minimizing the root mean square (RMS) displacement of the tower. To have an insight into the control performance of SMA-based TMDs, a three-dimensional (3D) finite element model of a typical wind turbine tower is developed in ABAQUS, and tower responses without and with SMA-based TMDs when subjected to simulated and recorded ground motions are systematically analysed. For comparison, seismic responses of the tower controlled by the linear TMDs are also simulated. Numerical results show that the SMA-based TMDs can substantially mitigate seismic responses of the tower with almost the same reduction ratios as the linear TMDs, while the strokes of the SMA-based TMDs are much smaller than those of the linear TMDs. This merit makes the proposed method more practical compared to the conventional TMD-based method since the space in the nacelle and tower is normally very limited. [ABSTRACT FROM AUTHOR]

Due to structural irregularity, curved bridgesaremore likely to cause non-uniform collisions and unseating between adjacent components when subjected to earthquakes. Based on the analysis of the collision response of curved bridges duringearthquakes, and according to the seismic characteristics of curved bridges, research was carried out on pounding mitigation and unseating prevention measures. A curved bridge with double column piers was taken as an engineering example, and a finite element model of curved bridges thatcould consider the non-uniform contact collision between adjacent components was built with ABAQUS software. Viscoelastic dampers, viscous dampers, and a lead rubber bearing were selected as the damping devices, and a steel wire rope-rubber mat was used as the pounding mitigation device to form the combinatorial seismic mitigation system. Based on the principle of energy dissipation combined with constraints, three kinds of combined seismic mitigation case were determined; a seismic response analysis was then performed. The results indicated that the three kinds of combined seismic case were effective atreducing the response topounding force, stress, damage, girder torsion and displacement, and achieved the goals of seismic mitigation and unseating prevention. [ABSTRACT FROM AUTHOR]

• Geometrical survey of a 40 m height masonry bell tower by means of drone and images elaboration algorithm. • Mechanical and chemical diagnostic of existing masonry with different non destructive tests. • Seismic vulnerability assessment by means of modal, pushover and kinematic analyses. • Strengthening design against overturning of masonry bell tower. The masonry building Heritage embraces a large variety of structural typologies, including churches, bridges, arenas, theatres, portals, castles, temples, and towers. The structural behaviour of these constructions appears often complex to be understood due to the uncertainties related to the materials and internal geometry. In this paper, a complete study (i.e. from the data acquisition and elaboration to the vulnerability analysis and proposal for a non-invasive strengthening procedure) of a monumental bell tower building is reported. An extensive program of structural and geometrical surveys has been planned and performed. The main goal of the breakdown was to assess the stability and the seismic vulnerability of the bell tower. Moreover, an innovative use of the drone-based survey for the computation of the geometry of the structure is proposed, in order to significantly reduce the time-cost expenditure of the structural assessment, without any significant lack in the accuracy of the measurements. The resulting object, obtained from the drone-based digitalized survey, was inputted and set in a Finite Element Method (FEM) code for structural modelling. Moreover, a nonlinear kinematic analysis was performed to individuate the possible failure mechanisms. Finally, a non-invasive strengthening procedure, aiming to the improvement of the seismic capacity, is proposed. [ABSTRACT FROM AUTHOR]