Seismic Applications Research Articles

Experimental Study on the Seismic Mechanism of Full-scale Specimens of Superimposed Slab Shear Walls with Innovative Construction Details

The seismic performance of precast reinforced concrete structures has long been a source of concern that impedes their use in seismic regions and high-rise buildings. To further optimize the reinforcement configuration and enhance the seismic performance of the superimposed slab shear wall structures, this research proposed a superimposed slab shear wall with innovative construction details. Five innovative superimposed slab shear walls and one cast-in-place concrete shear wall were designed and tested under low cycle lateral load. The effect of axial compression was considered during tests and analyses as well. In this paper, the seismic performance, including failure mode, hysteretic behavior, load-bearing capacity, lateral stiffness degradation, energy dissipation, and seismic ductility was investigated and analyzed. The experimental results showed that five innovative superimposed slab shear walls and one cast-in-place concrete shear wall exhibited a similar failure mode of flexural-shear failure, and a large area of concrete was damaged and crushed at the shear wall corner. However, the area of crushing concrete in the cast-in-place concrete shear wall was relatively small. And the area of crushing concrete in the superimposed slab shear walls increased with the axial compression ratio. For the superimposed slab shear walls, the development of concrete cracks decreased gradually with the enlargement in the axial compression ratio, while the length of the cracks increased in this respect. The results indicated that innovative superimposed slab shear walls had a higher strength capacity and lower lateral-resistant stiffness than the cast-in-place concrete shear wall. With the enlargement in the axial compression ratio, the peak strength capacity of the superimposed slab shear wall increased obviously, while it degraded rapidly after the peak load. It is suggested that the contribution of axial compression to the shear resist capacity of the inclined section should not be considered in practical design. Meanwhile, the ductility coefficients of the six specimens were larger than 2.2, which was in accordance with the seismic requirements. This investigation could provide effective experimental data for future structural seismic performance evaluations and applications of precast superimposed slab shear wall structures.

Seismic Rigoletto: Hazards, risks and seismic roulette applications

Neo-Deterministic Seismic Hazard Assessment (NDSHA), dating back to the turn of the Millennium, is the new multi-disciplinary scenario- and physics-based approach for the evaluation of seismic hazard and safety–guaranteeing “prevention rather than cure.” When earthquakes occur, shaking certainly does not depend on sporadic occurrences within the study area, nor on anti-seismic (earthquake-resistant) design parameters scaled otherwise to probabilistic models of earthquake return-period and likelihood — as adopted in the widespread application of the model-driven Probabilistic Seismic Hazard Analysis (PSHA). Therefore, from a policy perspective of prevention, coherent and compatible with the most advanced theories in Earth Science, it is essential that at least the infrastructure installations and public structures are designed so as to resist future strong earthquakes. Evidences and case histories detailed in the newly published book Earthquakes and Sustainable Infrastructure present a new paradigm for Reliable Seismic Hazard Assessment (RSHA) and seismic safety — comprehensively detailing in one volume the ‘state-of-the-art’ scientific knowledge on earthquakes and their related seismic risks, and actions that can be taken to ensure greater safety and sustainability. The book is appropriately dedicated to the centenary of Russian geophysicist Vladimir Keilis-Borok (1921–2013), whose mathematical-geophysical insights have been seminal for the innovative paradigm of Neo-deterministic seismic hazard assessment. This review focuses on Hazards, Risks and Prediction initially discussed in the introductory Chapter 1 — an understanding of which is essential in the applications of the state-of-the-art knowledge presented in the book’s 29 following chapters.

Superelastic Conical Friction Pendulum Isolator for Seismic Isolation of Bridges under Near-Fault Ground Motions

To improve the seismic performance of bridges, this study develops a novel superelastic conical friction pendulum isolator (SCFPI) by incorporating an improved conical friction pendulum isolator (CFPI) with shape memory alloy (SMA). The flat sliding function designed for the improved conical friction pendulum isolator is to enhance the adaptability under service loadings. The analytical model of the novel SCFPI is derived and the numerical model is developed within the OpenSees platform to investigate the hysteretic behavior under cyclic loadings. A cost-effective design method is proposed to design the SCFPI system for example bridges. The response mitigation efficacy of the novel SCFPI system is investigated using the optimum design parameters under near-fault ground motions. Several case studies are conducted to demonstrate the effectiveness of the novel SCFPI system and cost-effective design method. Results indicate that the cost-effective design method is particularly effective for parameter optimization of the novel SCFPI, which achieves effective mitigation for the displacement responses of the isolator and superstructure and also effectively controls the seismic force increment in piers. Case studies indicate the reliable re-centering capacity and mitigation efficacy of the SCFPI system for bridges under near-fault ground motions. The findings of this study contribute to upgrading structural resilience and promoting seismic applications as a reliable technical guidance.

Superelastic pendulum isolator with multi-stage variable curvature for seismic resilience enhancement of cold-regional bridges

This study develops a novel superelastic pendulum isolator with multi-stage variable curvature (SPIVC) to enhance the seismic resilience of the cold-regional bridges. The SPIVC comprises the improved conical friction pendulum bearing (CFPB) with flat surface, spherical surface and inclined surface connected in series and re-centering devices fabricated by copper-based shape memory alloy (CuSMA). The novel SPIVC features the deformation accommodation under service loadings and seismic isolation under seismic shaking. The numerical model of the SPIVC is developed within OpenSees using the experimentally observed parameters. A typical continuous bridge is selected as benchmark bridge to investigate the seismic performance of the SPIVC system in cold regions. To achieve optimum parameters of the SPIVC, a cost-effective design method is developed based on the hysteretic characteristics of the re-centering device. The seismic performance of cold-regional bridge with SPIVCs under near-fault earthquakes is investigated and assessed by case study. Results show that the proposed method is effective to capture the isolator parameters. Case studies demonstrate the re-centering and seismic isolation performance of the SPIVC system employing the optimum parameters for bridges in cold regions, i.e., the novel SPIVC system can perform the dual control of the girder displacement, permanent isolator displacement and the seismic shear of the piers for each ambient temperature. The achieved findings can be employed to guide the resilience enhancement of the cold-regional structures and potential seismic applications.

Some remarks on the performance of three advanced soil constitutive models in the small-strain region

ABSTRACT This short communication identifies some inconsistencies in the numerical predictions of three advanced soil constitutive models. The chosen constitutive models are subject to simple numerical tests in the small-strain range relevant to the cyclic response of soil in seismic, offshore and urban applications. The numerical tests comprise a cyclic simple shear test in the small-strain range, a simple shear test with very small strain unloading-reloading loops and a test on the dependence of the rate of the shear stiffness degradation on the changing mean confining stress. The results are briefly discussed and, in some cases, the reasons for the observed inconsistencies and potential improvements in the formulations of the investigated constitutive models are initially drafted.

Seismic collapse assessment of archetype frames with ductile concrete beam hinges

Highly ductile cement-based materials have emerged as alternatives to conventional concrete materials to improve the seismic resistance of reinforced concrete (RC) structures. While experimental and numerical research on the behavior of individual components has provided significant knowledge on element-level response, relatively little is known about how ductile cement-based materials influence system-level behavior in seismic applications. This study uses recently developed lumped-plasticity models to simulate the unique failure characteristics and ductility of reinforced ductile-cement-based materials in beam hinges and applies them in the assessment of archetype frame structures. Numerous story heights (four, eight, and twelve), frame configurations (perimeter vs. space), materials (conventional vs. ductile concrete), and replacement mechanisms within the beam hinges are considered in the seismic analysis of the archetype structures. Results and comparisons are made in terms of the probability of collapse at 2% in 50-year ground motion, mean annual frequency of collapse, and adjusted collapse margin ratio (ACMR) across archetype structures. The results show that engineered HPFRCCs in beam plastic-hinge regions can improve the seismic safety of moment frame buildings with higher collapse margin ratios, lower probability of collapse, and the ability to withstand large deformations. Data is also reported on how ductile concrete materials can reduce concrete volume and longitudinal reinforcement tonnage across frame configurations and story heights while maintaining or improving seismic resistance of the structural system. Results demonstrate future research needs to assess life-cycle costs, predict column hinge behavior, and develop code-based design methods for structural systems using highly ductile concrete materials.

Waveform Inversion of Shallow Seismic data with Randomly Selected Sources

Applying waveform inversion with randomly selected sources (RS) increases the convergence rate of the optimization process within full-waveform inversion (FWI) workflows and reduces overall computational time. FWI has been shown to be a valuable addition to the existing geophysical methods for near-surface characterization. Accurate 3D modeling of the (visco) elastic wavefield allows to diminish assumptions about wave propagation and include surface- and body-wave based arrivals within the inversion workflow. This approach could result in reliable high-resolution subsurface models, but generally it comes at a high computational cost for each individual source modeling. Commonly, multiple sources are involved in the inversion process, which proportionally increases the resulting computations for a time-domain FWI, but seismic data with dense source/receiver coverage usually contain redundant information. This is especially true for seismic near-surface applications, where the number of recorded sources per wavelength of interest are normally excessive. The inversion performance was increased by randomly selecting a subset of sources at each FWI iteration. The method's effectiveness is obvious on a FWI near-surface void detection application. Synthetic 2D experiments for fixed and rolling spreads showed comparable results with fewer calculations. The best performance was achieved when a single random source was used for each inversion iteration. The effectiveness of the method was also evident on a shallow 3D field dataset collected in the Sonora Desert in western Arizona, where data were acquired over a 10-m deep void with known location, orientation, and dimensions.

Data processing of the Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system and application to South China Sea data

Data processing of the Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system and application to South China Sea data

Seismic Reduction Mechanism and Engineering Application of Paste Backfilling Mining in Deep Rock Burst Mines

In the process of coal resources development, a large number of strip coal pillars have been left behind in the coal mines in central–eastern China. With the increase in coal mining depth year by year, the rock burst threat of strip coal pillars is becoming more and more prominent due to the influence of buried depth, geological structure, gob and other factors. Backfilling mining is the main means to recover the residual strip coal pillar. In order to investigate the effect of backfilling mining on the prevention and control of rock burst, taking the paste backfilling workface 1# of Gucheng coal mine as the engineering background, a comprehensive research method of theoretical analysis, numerical simulation and field monitoring was used to study the evolution of stress and of the overburden spatial structure of the backfilling workface under the control of the backfilled ratio. The results showed that the backfilling mining controls the movement and deformation of overburden by reducing the activity range of roof strata. The overburden fracture development height decreases with the increase in backfilled ratio, but there is a boundary effect influenced by the roof deflection before backfilling and the defective distance of roof contact. With the increase in backfilled ratio, the concentration coefficient of front abutment pressure, the vertical displacement of the roof and the development height of the plastic zone of overlying strata decreased obviously, which indicates that filling mining can effectively control the stress of surrounding rock and the movement of overlying strata. The field monitoring data showed that the influence range of the front abutment pressure of the paste backfilling workface was about 90 m and the maximum stress of the surrounding rock of the two entries did not exceed 7 MPa. The average daily frequency of microseism was 1.34, and the average daily total energy of microseism was 1.80 + 103 J, which decreased by 69% and 90%, respectively, compared with the caving method working face with similar geological conditions. The data above showed that the backfilling mining can effectively reduce the working face stress level and dynamic load strength to achieve the effect of prevention and control of rock burst.

Geophysics-steered self-supervised learning for deconvolution

SUMMARYDeep learning (DL) has achieved remarkable progress in geophysics. The most commonly used supervised learning (SL) framework requires massive labelled representative data to train artificial neural networks (ANNs) for good generalization. However, the labels are limited or unavailable for field seismic data applications. In addition, SL generally cannot take advantage of well-known physical laws and thus fails to generate physically consistent results. The weaknesses of standard SL are non-negligible. Therefore, we provide an open-source package for geophysics-steered self-supervised learning (SSL; taking application to seismic deconvolution as an example). With the wavelet given, we incorporate the convolution model into the loss function to measure the error between the synthetic trace generated by the ANN deconvolution result and the observed data, steering the ANN’s learning process toward yielding accurate and physically consistent results. We utilize an enhanced U-Net as the ANN. We determine a hard threshold operator to impose a sparse constraint on the ANN deconvolution result, which is challenging for current DL platforms because no layer is available. 2-D/3-D ANNs can naturally introduce spatial regularization to the ANN deconvolution results. Tests on synthetic data and 3-D field data with available well logs verify the effectiveness of the proposed approach. The approach outperforms the traditional trace-by-trace method in terms of accuracy and spatial continuity. Experiments on synthetic data validate that sparsity promotion matters for sparse recovery problems. Field data results of the proposed approach precisely identify the layer interfaces and mostly match well with the log. All codes and data are publicly available at https://doi.org/10.5281/zenodo.7233751 (Xintao Chai).

Homogenization of porous thin layers for seismic reflectivity applications

Homogenization of porous thin layers for seismic reflectivity applications

Homogenization of porous thin layers for seismic reflectivity applications

Homogenization of porous thin layers for seismic reflectivity applications

Simultaneous denoising and resolution enhancement of seismic data based on elastic convolution dictionary learning

Enhancing seismic resolution is a key component in seismic data processing, which plays a valuable role in raising the prospecting accuracy of oil reservoirs. However, in noisy situations, existing resolution enhancement methods are difficult to yield satisfactory processing outcomes for reservoir characterization. To solve this problem, we develop a new approach for simultaneous denoising and resolution enhancement of seismic data based on convolution dictionary learning. First, an elastic convolution dictionary learning algorithm is presented to efficiently learn a convolution dictionary with stronger representation capability from the noisy data to be processed. Specifically, the algorithm introduces the elastic L1/2 norm as a sparsity constraint and employs a steepest gradient descent strategy to efficiently solve the frequency-domain linear system with substantial computational cost in a half-quadratic splitting framework. Then, based on the learned convolution dictionary, a weighted convolutional sparse representation paradigm is designed to encode the noisy data to acquire an optimal sparse approximation of the effective signal. Subsequently, a high-resolution dictionary with a broadband spectrum is constructed by the proposed parameter scaling strategy and matched filtering technique on the basis of atomic spectrum modeling. Finally, the optimal sparse approximation of the effective signal and the constructed high-resolution dictionary are used for data reconstruction to obtain the seismic signal with high resolution and high signal-to-noise ratio. Synthetic and field dataset examples are executed to check the effectiveness and reliability of the developed method. The results indicate that this method has a more competitive performance in seismic applications compared with the conventional deconvolution and spectral whitening methods.

高減衰ゴム系積層ゴム支承を有する免震建物のバイリニアモデルへの置換

High damping laminated rubber bearings are highly popular in seismic isolation application. However, due to the nonlinear dependency of the force restoring characteristics on shear strain, energy balance methods cannot be applied to evaluate the response of the isolation layer. Therefore, by replacing the complex restoring force characteristics of high damping rubber bearings with a simple bi-linear model, energy balance methods can be applied. In this paper, several replacement methods are compared in reproducing the accuracy of the response of the isolation layer using time history analysis and considering different earthquake motion phase characteristics and shear strain conditions.

Large-size shape memory alloy plates subjected to cyclic tension: Towards novel self-centring connections in steel frames

In this study, the hysteretic behaviour of shape memory alloy (SMA) plates under cyclic tension-release loadings was examined to promote their seismic applications, with an emphasis on large-size SMA plates with different geometries. Based on a series of SMA plate coupons extracted from base plates with different geometries, the thermal characteristics were investigated, and the phase transformation behaviour of the SMA plates was characterised. Subsequently, cyclic tension-release tests were conducted on the SMA plates in the laboratory, and the key mechanical performance indexes including the transformation strength, post-yield behaviour, self-centring capabilities, and energy dissipation abilities were carefully investigated. According to the results, SMA plates have a comparatively encouraging self-centring ability and moderate energy dissipation capabilities within a specified strain range. However, larger SMA plates show less satisfactory self-centring behaviour and are prone to brittle fracture at the edges. Based on the test programme, a numerical investigation was conducted to offer further insight into the potential applications of large-size SMA plates in the seismic field. A practical modelling procedure, namely the hybrid finite element (FE) modelling technique, was proposed and used to reproduce the degradation and cumulative residual deformation in the SMA plates. Moreover, nonlinear response history analyses (NL-RHAs) were performed on a prototype steel frame equipped with SMA plates in the connections to verify the feasibility of using large-size SMA plates in steel structures.

Generation and Evaluation of CPT Data Using Kriging Interpolation Technique

The cone penetration test (CPT) has been the de facto field exploration method in geotechnical engineering for decades. Variations of CPT can measure parameters for seismic, environmental, and hydrological applications. Analyzing response often requires properties in areas that have little or no data. Therefore, given the limited CPT data, it is critical to understand how to accurately estimate the soil properties at unsampled locations. In this paper, we generated soil shear wave velocity profiles using the kriging interpolation technique and assessed their performance using site response analysis. Four kriging interpolation-based shear wave velocity profiles and four additional CPT-based shear wave velocity profiles defined site conditions for response analysis. We performed a series of 1-D equivalent linear site response analyses using STRATA software. The site response analysis results are presented as amplification factors (AF), peak ground acceleration (PGA) profiles, surface spectral acceleration, and surface acceleration time histories. Compared to CPT-based profiles, the results of kriging interpolation-based profiles were evaluated and discussed. The results confirmed the reliability of the kriging interpolation technique in predicting soil parameters at unsampled locations.

Seismic responses, damage mechanisms and retrofitting methods for deep braced excavation: Centrifuge test and numerical analysis

The current study investigates the nonlinear seismic responses and damage mechanisms of the deep braced excavation, which has rarely been inspected in previous studies. An effective numerical model is developed based on dynamic centrifuge tests to properly capture the responses and damage of the structure under earthquakes. The model is established by using the nonlinear properties of the material (for both soil and structure) and contact. The procedure of constructing the numerical model including determining the material parameters, boundary conditions, and contact properties is elaborated. The seismic responses of the deep braced excavation during earthquakes with increasing levels of earthquake intensity are clearly investigated and compared with those in the static condition. Then, the damage mechanisms of the structure are stated. Finally, different seismic retrofitting methods are proposed; and, the most effective method is suggested. The findings from this study can provide a clear understanding of the seismic responses, damage mechanisms, seismic retrofitting methods, and also recommendations for seismic design applications of deep braced excavations.

Seismic structural control using magneto-rheological dampers: A decentralized interval type-2 fractional-order fuzzy PID controller optimized based on energy concepts

In this paper, a combination of the interval type-2 fuzzy logic controller (IT2FLC) with the fractional-order proportional–integral–derivative (FOPID) controller, namely optimal interval type-2 fractional-order fuzzy proportional–integral–derivative controller (OIT2FOFPIDC), is developed for enhancing the seismic performance and robustness in seismic structural control applications. Based on the energy concepts, a decentralized framework of the OIT2FOFPIDC is proposed for easy and simple implementation in structures during earthquakes. For this purpose, a coot optimization algorithm (COA), as a powerful optimization algorithm, is also applied to adjust the membership functions (MFs), scaling factors, and the main controller parameters. Three controllers, namely optimal type-1 fuzzy proportional–integral–derivative controller (OT1FPIDC), optimal interval type-2 fuzzy proportional–integral–derivative controller (OIT2FPIDC), and optimal proportional–integral–derivative controller (OPIDC), are also proposed for comparison purposes. The seismic performances of the suggested controllers are examined with the evaluation of nine seismic performance indices and different ground accelerations in a 6-story smart structure equipped with two dampers. The robustness of the four controllers in the presence of the stiffness uncertainties is also compared in this study. On average, a reduction of 25.0%, 18.8%, and 18.5% in peak displacement, inter-story drift, and acceleration of stories is obtained for the OIT2FOFPIDC over the OT1FPIDC, respectively. Similarly, these reductions in comparison with the OIT2FPIDC are 16.3%, 13.3%, and 12.0%. Also, these reductions, in comparison with the OPIDC, are 33.3%, 27.8%, and 25.8%. Furthermore, simulation results show that the OIT2FOFPIDC is more robust than the other proposed controllers against uncertainties due to structural stiffness.

SLIM‐FLOOR BEAM‐TO‐COLUMN JOINTS FOR SEISMIC‐RESISTANT STRUCTURES: JOINT PERFORMANCE AND CASE STUDY ON MOMENT‐RESISTING FRAMES

AbstractThe current seismic design of steel and composite frames relies on lateral frame stiffness and on the controlled failure mechanism of dissipative members or connections. The implementation of the slim‐floor solution in practice results in several advantages. But due to the reduced height of the slim‐floor beam – generally considered to result in lower flexural stiffness – the current practice disregards the usage of moment‐resisting slim‐floor beam‐to‐column joints in seismic applications. However, a previous study of the authors has experimentally and numerically confirmed the possibility of expanding the application of composite beams by developing inelastic behaviour in slim‐floor beams. The test results allowed the definition of the slim‐floor beam's mechanical characteristics and the evaluation of the structure's seismic performance through nonlinear static and dynamic analyses. The usage of the slim‐floor system resulted in a vertical space gain ‐ due to its reduced height ‐ and demonstrated the solution's effectiveness when implemented in seismic‐resistant structures.

RCS MOMENT FRAMES IN HIGH SEISMIC ZONES IN THE UNITED STATES

AbstractThe research on composite moment connections for seismic applications is examined to propose an update of the Guidelines for Design of Joints Between Steel Beams and Reinforced Concrete Columns, published by the ASCE in 1994. These guidelines were developed based on limited experimental data and restrict composite moment frames to zones of low to moderate seismicity. Recent experimental data, however, support their use in high seismic regions. A database of full‐scale connection tests is included, accompanied by a comparison between strength measured experimentally vs. the calculated joint strength. Results from this comparison show good agreement.