Seismic Tests Research Articles

Full-Scale Testing on Seismic Performance of Surge Arrester with Retrofitted Composite Insulators

In electrical substations, glass-fibre reinforced polymer (GFRP) insulators provide an alternative to porcelain insulators for better seismic performance. The bonded connection between the composite tube and the metal end fitting is a weak link under earthquake actions, and the failure risk of ultra-high voltage (UHV) substation equipment with GFRP composite insulators can be considerable in places with high seismicity. This study solved the problem by retrofitting and experimentally qualifying the seismic performance of surge arresters made of composite insulators. To ensure safety under a bending moment corresponding to the seismic demand, the bonded sleeve joint between the tube and end fitting was retrofitted by shear stiffeners and higher strength end fitting. A full-scale shaking table test was carried out to verify the performance of the retrofitted surge arrester, and the seismic responses to increasing earthquake actions were analyzed. The specimens in this study were full-scale, had the largest dimensions among substation equipment of the same type, and were subjected to an extremely high earthquake action of 0.5 g; therefore, the seismic testing results produced in this study can serve as an important reference for the industry.

Research and Application of Seismic Performance of Medical Imaging Equipment

In view of the shortage of research on the seismic performance of medical imaging equipment, this paper investigates and summarizes the seismic regulatory requirements and seismic tests of medical imaging equipment, and focuses on the parameter selection, detection steps, result evaluation and detection equipment requirements of seismic detection of medical imaging equipment. The seismic test data of medical imaging equipment with various installation modes are analyzed, and the seismic performance of medical imaging equipment is analyzed and summarized.

Seismic Performance Test of Concrete Column Reinforced with EPFT

Seismic Performance Test of Concrete Column Reinforced with EPFT

In situ seismic testing for experimental modal analysis of civil structures

This paper presents a novel excitation method for in situ experimental modal analysis (EMA) and compares its performance to ambient vibration analysis, also known as operational modal analysis (OMA). The method consists of base excitation through ground accelerations generated through a large mobile shaker, a unique form of building excitation which has not been studied to date. The controllable and repeatable nature of the excitation complements some limitations of OMA, including inconsistent excitation conditions and low energy at high frequencies. The method is applied to an instrumented eleven-story building in Austin, Texas, resulting in observations of significant energy input up to 50 Hz. The high input bandwidth is essential to characterizing high order modes which ambient sources do not excite. Using a five-minute set of multiple 20-s chirp excitations from 5 to 50 Hz in two directions (vertical and transverse), it is shown that the in situ seismic EMA yields modes which are not identified through standard ambient OMA. The differences in identification methods were most noticeable above 7 Hz, where vertical contributions accounted for a significant portion of the modal response. Above 11 Hz, ambient excitation was too weak for proper OMA, but EMA enabled the identification of high-order “local” modes, although their complete identification was limited by low sensor density. The primary benefit of OMA comes from processing time series of much longer duration (20 min), which reduced variation in most of the modal estimates, given the fairly consistent ambient excitation conditions during testing. Overall, in situ seismic testing is shown to be a viable option for forced vibration testing of very large civil structures. With refinements in the testing methods, the technique could be used as a complement to ambient vibration testing in contexts where the ambient excitation bandwidth is limited or quick, short-term tests are desired.

Wolverines (Gulo gulo) in the Arctic: Revisiting distribution and identifying research and conservation priorities amid rapid environmental change.

Wolverines (Gulo gulo) occupy most of the globe’s Arctic tundra. Given the rapidly warming climate and expanding human activity in this biome, understanding wolverine ecology, and therefore the species’ vulnerability to such changes, is increasingly important for developing research priorities and effective management strategies. Here, we review and synthesize knowledge of wolverines in the Arctic using both Western science sources and available Indigenous Knowledge (IK) to improve our understanding of wolverine ecology in the Arctic and better predict the species’ susceptibility to change. To accomplish this, we update the pan-Arctic distribution map of wolverines to account for recent observations and then discuss resulting inference and uncertainties. We use these patterns to contextualize and discuss potential underlying drivers of distribution and population dynamics, drawing upon knowledge of food habits, habitat associations, and harvest, as well as studies of wolverine ecology elsewhere. We then identify four broad areas to prioritize conservation and research efforts: (1) Monitoring trends in population abundance, demographics, and distribution and the drivers thereof, (2) Evaluating and predicting wolverines’ responses to ongoing climate change, particularly the consequences of reduced snow and sea ice, and shifts in prey availability, (3) Understanding wolverines’ response to human development, including the possible impact of wintertime over-snow travel and seismic testing to reproductive denning, as well as vulnerability to hunting and trapping associated with increased human access, and (4) Ensuring that current and future harvest are sustainable.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00300-022-03079-4.

Seismic Performance Test of Multi-ply Metal Bellow-Type Expansion Joints

Seismic Performance Test of Multi-ply Metal Bellow-Type Expansion Joints

Field Research on the Treatment of Coastal Phase Liquefaction Foundation with Clay Interlayer Using Resonance Probe Compaction Method

The resonance probe compaction (RPC) method is an effective technique for particular soils, which mainly includes sandy and loess. However, the application of RPC on contaioning clay interlayer area has never been seen. In this study, a successful case of using the RPB method to treat the clay interlayer foundation is presented in detail. The test results of Huaiyan high-speed railway construction project are introduced. The test is divided into the laboratory test and the field test, mainly including standard penetration test (SPT), cone penetration test (CPT) and seismic wave cone penetration test (SCPT). The test results indicated that the cone resistance of silt and silty sand layers increased to an average of 2.13 times compared with an average of 4.39 MPa before treatment, and the sleeve friction whose initial average is 54.17 kPa increased to an average of 1.74 times. The existence of the clay interlayer does not affect the consolidation and drainage of the silt layer and the silt sand layer, and after the construction, the excess pore water pressure around the vibration point can be dissipated by more than 90% within 15 minutes. After reinforcement, the standard penetration number of subsoil, increased by about 15%–95% compared with an average of 19 blows before treatment and the clay particle content of some clay interlayers are reduced to less than 10%. The shear wave velocity of the subsoil in the treatment depth increased by about 15%–48% compared with 140 m/s before treatment. The RPC method was successful for the coastal phase liquefaction foundations.

Experimental study of post-installed anchor embedded in concrete under simulated seismic and wind loads

In this study, experimental protocol to simulate wind-induced vibration of post-installed anchor embedded in concrete was developed. The proposed loading protocol was based on the ratio of deformation due to seismic load and dynamic wind load of anchors in the connection between the sign structure and the concrete building. Then, based on ACI 355.2 and the developed protocol, numerous experimental tests were conducted to evaluate the performance of anchor under simulated seismic and wind loads. In simulated seismic test, crack width of concrete did not affect the performance of anchor. Their maximum force as well as residual capacity showed practically the same value. Moreover, anchor used in this experiment satisfied the condition to be rated as full capacity for seismic performance. In simulated wind test, the crack width did not cause any difference in performance of the anchor in tension test. Though, in simulated wind shear test, there was a major difference for the anchor residual capacity. Additionally, the performance of anchor in simulated wind test did not satisfy the criteria to be rated as full capacity.

Stiffness decay characteristics and disturbance effect evaluation of structured clay based on in-situ tests

The structure of the sedimentary clay influences its mechanical behavior in non-negligible ways. This paper proposes an effective approach for investigating the in-situ stiffness characteristics from shear modulus and strain decay curves (G–γ curves) based on self-boring pressuremeter and seismic dilatometer tests. To evaluate the excavation disturbance effects on the structured clay, the stiffness parameters from pre-bored pressuremeter tests are compared with the results of self-boring pressuremeter tests. The result indicates that the complete in-situ G–γ curves can be acquired by integrating the strain-dependent tangent shear modulus Gt from self-boring pressuremeter tests and the small-strain modulus G0 from seismic dilatometer tests. Simultaneous observations of the G–γ curves with hyperbolic shapes in semi-logarithmic coordinates at the same strain scale show the similarity of the stiffness decay mode of the soil at different depths. The increase in the measured values of Gt and G0 with depth can be attributed to the improved consolidation pressures and cemented strength in the structured clay. Additionally, the G/G0–γ curves measured by the in-situ tests generally agree well with the results predicted by the Stokoe model. The excavation disturbance weakens the stiffness of the structured clay, as evidenced by Gt from the pre-bored pressuremeter data being significantly smaller than that from self-boring pressuremeter tests at the same depth. Based on quantitative analysis, the disturbance degree computed from the measured results has a low sensitivity to the soil depth and a strong negative correlation with the strain level of the soil. This study provides an effective method for predicting the stiffness parameters of structured soil based on in-situ tests.

An Attempt to Study Foundation Anchoring Conditions in Sedimentary Estuaries Using Integrated Methods

The search for and knowledge of the best conditions for anchoring the foundations of certain structures such as bridges, tunnels and quays in sedimentary estuaries is a challenge, for both scientists in general and engineers in particular. Indeed, wharves are structures that receive a lot of stresses and therefore require anchoring to avoid tilting and to guarantee their stability during service. This work, based on the analysis of data from seismic refraction methods, mechanical soundings and laboratory tests, characterises the terrain of the Wouri estuary in Central Africa. The objective is to determine and present the subsurface layers encountered as well as their characteristics, in order to define the best conditions for anchoring the foundations to ensure the stability of the quays to be built there. The seismic refraction campaign shows that the study area is relatively heterogeneous over the first 25 m, with velocities measured in the range 1520–1750 m/s; modulated in two distinct ranges, between 1520–1580 m/s characteristic of mud and loose sediments (alternating layers of clay, sand, loose silt) and the range 1580–1750 m/s corresponding to the signature of sandy-silty or compact clays. The mechanical tests show sedimentary soils, with alternating layers of sandy clay and clayey sand over the 42 m drilled, loose over the first 30 m in the bank area and over the first 15 m in the canal or dredge area, with a limit pressure of less than 1 MPa. Similarly, the soil samples taken and tested in the laboratory show that the soils are clayey over the first 30 metres, plastic and liquid with respect to their water content, respectively, below and above the liquidity limits, confirming their loose character. The results of seismic refraction, mechanical soundings and laboratory tests show that, in estuarine areas characterised by alternating sandy clay and clayey sand, there are not always hard formations in the first 25 metres of depth but, from a depth of 30 m, the soils become moderately compact and begin to form an anchoring layer sufficient to guarantee the stability of the quays against earth pressure forces.

An efficient full-wavefield computational approach for seismic testing in a layered half-space

Inversion of subsurface shear-wave velocity profile based on effective dispersion curve or full wavefield is still rare due to the lack of efficient forward computation kernel for the full wavefield in a layered medium. To facilitate exploiting the complete signal content in seismic testing, an efficient new computational framework for modeling synthetic full wavefields in horizontally layered systems is proposed. Dynamic response of an isotropic elastic layered system subjected to vertical loading is implemented and thoroughly validated. The new procedure is based the Fourier-Bessel series expansion (not the traditional Fourier-Bessel transform), and it is at least two-orders faster than the current full wavefield computation method based on integral transformation. It considers survey parameters and models all wave phenomena, including near-field effect and leaky waves, which cannot be captured by the modal summation method. Examples of full wavefield simulation are presented to demonstrate different levels of information provided by the experimentally available fundamental mode, broadband effective dispersion curve, and the full velocity spectrum. Different earth models may have similar fundamental modes or even effective dispersion curves; however, their difference manifests in different higher-mode contributions and can only be exploited by utilizing the entire velocity spectra including the vertical and radial components. The coupling between the vertical and radial components in terms of their spectral ratio and phase difference can provide additional constraints (data) in seismic testing.

Geotechnical characterization of the estuarine deltaic deposits in the Guayaquil city through in situ and laboratory tests

According to previously available research and seismic microzonation studies a large area of the Guayaquil (Ecuador, South America) sits on estuarine deltaic deposits which consist of weak and highly compressible clays with diatoms. The nature of these fine-grained deposits may determine difficulties in a proper estimation of the soil properties. In this respect, the paper provides a detailed geotechnical and geophysical characterization of these soft clays, carried out in the estuarine complex of the Ecuadorean city. Borehole logs, standard penetration tests (SPT), piezocone tests (CPTu), a seismic dilatometer test (SDMT), a non-invasive geophysical survey, and laboratory tests were performed and then compared to analyze the static and dynamic geotechnical parameters of these deposits. The interpretation of the results highlighted the higher reliability of CPTu and SDMT rather than SPT and characterization lab testing to estimate soil shear strength, compressibility and stress history due to the soft nature of these clays, underlining also a certain sensitivity to the presence of the diatoms.

3D Finite Element Analysis of Seismic Response of Rigid Pile Composite Foundation with Microprobe Group.

In order to study the seismic performance of the rigid pile composite foundation, a three-dimensional finite element analysis of the seismic response of the rigid pile composite foundation with microprobe group was proposed. The three-dimensional finite element method is used to analyze the dynamic response law of pile group rigid pile composite foundation under the action of the earthquake, especially the internal force response of the pile body. It is worth noting that when the internal force response of pile decreases significantly, the maximum internal force of the whole pile is also significantly smaller than the maximum internal force of pile foundation. However, when the pile body is located on a layered foundation and the modulus of adjacent soil layers differs greatly, the earthquake action will cause the pile body to generate a large internal force. The seismic performance of the rigid pile composite foundation is feasible, and it can be extended and applied to the similar seismic performance test of other composite foundations.

Artificial Intelligence for Automating Seismic Horizon Picking

Fully-automated seismic horizon picking dramatically shortens the time between acquiring seismic data and picking drilling targets. Oil and gas exploration companies worldwide spend millions of tedious man-hours picking horizons on seismic data to produce inventories of drilling targets. Freeing up that time to better incorporate the geologic and geophysical properties within mapped structures guarantees more drilling success. Artificial intelligence is frequently mentioned in today’s news: self-driving cars, vehicle identification, robot vacuums, fingerprint identification, facial recognition and Alexa are just a few examples. Why not seismic data interpretation? Here, it is proven that automated seismic horizon picking is possible. From a two-column text file of time-amplitude pairs my algorithm produces a reflection-time-ordered text file of all continuous series of connected pixel coordinates easily-read by mapping software. These connected pixels are plotted separately on the input seismic test line’s peaks and troughs. More than 10,000 connected segments were written in less than a minute of computer time, saving many hours of manual labour. This time-saving extrapolated to 3D seismic surveys will reduce the time it takes to find drilling targets by months.

Experimental Investigation of the Influence of the Anchor Cable Inclination Angle on the Seismic Response Characteristics of Anchored Piles

Studies show that prestressed anchor cable antislide piles have good antiseismic characteristics. As an important parameter in the design of anchor-cable piles, the effect of anchor-cable inclination on the seismic response of the anchor-cable pile system has been rarely studied so far. In the present study, the seismic response characteristics of the anchor-pulled pile under different cable inclinations are studied using a large-scale seismic model test platform and numerical methods. The obtained results show that the inclined angle of the anchor cable has a great influence on the seismic response of the pile-anchor system. It is found that under the same seismic conditions, the axial force of the anchor cable becomes smaller as the anchor dip angle increases, while the pile top displacement becomes larger. The dynamic earth pressure behind the pile changes from the sliding surface to the pile top, indicating that the earth pressure near the sliding surface and the pile top is of active and passive earth pressure types, respectively. This pressure decreases with the increase of the anchor dip angle, thereby affecting the performance of the antisliding pile.

Experimental seismic behaviors of different connections to CFST end-columns in shear walls

A new hot-rolled T-shaped connector (HTC) connection was proposed herein to solve the connecting difficulties between H-shaped beams and small-sized composite walls or CFST columns in steel residential buildings. The connection utilizes the hot rolled flange-to-web arch transition in hot rolled beams as the beam-end connector. In this way, the hot-rolled arch transition of the connector provides a smooth section transition at the column face junction to avoid stress concentrations and premature fracture problems in traditional welded junctions. The new connections, together with the existing endplate type and side plate type connections, were applied to a specially-shaped corrugated plate shear wall system. Seismic loading tests were performed to explore seismic behaviors and the applicability of those connections in steel residential buildings. Results indicated that the side plate connections and HTC connections exerted good hysteretic performance with stable hysteretic behaviors, slow stiffness degradation, good energy dissipation ability, and satisfactory ductility. The endplate connection experienced early fracture failure of the side plate to endplate welds. In addition to the satisfactory seismic performance, the proposed HTC connections had no extended stiffeners and little intrusion into the indoor space, and could be easily hidden within partition walls.

Hysteretic model and resilient application of corrugated shear panel dampers

In this study, corrugated steel shear panels were applied to a metallic shear panel damper (SPD) to improve its seismic performance. The seismic performance tests and analysis of eight specimens were performed for different corrugated steel panel directions, arrangement forms, and material strengths. The results showed that the metallic corrugated shear panel dampers (CSPDs) exhibited remarkable plastic deformation and plump hysteretic loops. The direction of corrugated shear panels had the most significant influence on the energy dissipation performance, and the results of the horizontal corrugated direction exhibited the great performance. Then, the improved Bouc–Wen model was used to predict the hysteretic behaviour of the CSPDs, and the universal global optimization algorithm was applied to identify the model parameters. Additionally, a typical 12 storey benchmark steel frame structure was retrofitted with the CSPDs to verify the application effect of the CSPDs on structural vibration control. And the seismic fragility analysis was implemented to quantify the exceeding probabilities of different damaged states for the original structure and the damper improved structure. Compared with the benchmark frame, the performance level of the damper improvement frame in operation, immediate occupancy, life safety, and collapse prevention increased by 1.51%, 11.50%, 45.59%, and 81.19%, respectively, under the maximum considered earthquake (MCE) level. The analyses showed that the CSPDs could significantly improve the seismic resilience performance of the structure.

A dynamic poroelastic model for auxetic polyurethane foams involving viscoelasticity and pneumatic damping effects in the linear regime

This work proposes a new dynamic poroelastic model to describe the vibration transmissibility of auxetic polyurethane (PU) foams. The model includes the pneumatic damping effect provided by the porous structure of the foam, and the viscoelasticity of the PU material. The auxetic foam is manufactured using a simplified and relatively low-cost uniaxially thermoforming compression technique, which allows the production of a foam with transverse isotropic properties. Stress relaxation, quasi-static cyclic compressive-tensile and seismic base vibration tests in the small strains and linear elastic regimes have been performed in this work. The permeability and the viscoelasticity of the auxetic foams with different thermoforming compression ratios along the thermoforming and transverse directions are identified by performing a nonlinear regression from the mechanical and vibration-derived data. The auxetic foams possess lower stiffness along the thermoforming direction and higher modulus along the transverse one. The moduli of different auxetic foams obtained from quasi-static tests are 40%–70% lower than the corresponding dynamic values estimated from the seismic base excitation, while the static loss factors are all around 20%–100% lower than the corresponding dynamic ones. The enhancements of the dynamic stiffness and damping are mainly caused by the pneumatic damping effect and the viscoelasticity of the PU material. The permeability of the auxetic foam loaded along the thermoforming direction is ∼ 2 times larger than the one of the pristine foam, but 50% smaller when the foam is dynamically loaded along the transverse direction, due to the transverse isotropic microstructure of this porous material.

Struggle for the sands of Xolobeni – From post-colonial environmental injustice to crisis of democracy

In resource-rich South Africa, natural resource extraction has been fundamental to processes of primitive accumulation, forming the bedrock of the national economy. Accordingly, struggles for control over land and resources have been constant throughout this nation’s history. The coastal sands of Xolobeni on South Africa's Wild Coast, where Australia’s Mineral Commodities (MRC) and its South African subsidiary Transworld Energy and Minerals (TEM) Ltd. has set its sights on a wealth of titanium and other minerals, is home to one such struggle. Taking an approach of narrative enquiry, this article applies an analytic lens of post-colonial environmental injustice to show how the State has colluded with corporate powers to sacrifice marginal black South African communities upon an altar of development defined by extractivism and dominated by global capitalism. Its analysis reveals the captured South African state as the leading agent of “slow violence”, and argues that this conflict is indicative of a larger crisis of democracy. It also questions how communities who oppose mining and favour alternative forms of development, can successfully defend land and livelihoods. Reflecting on an ongoing court battle with Shell over seismic testing off the Wild Coast, the article concludes that the State cannot be depended upon to protect the interests of rural communities, or to deliver societal transformation, let alone decolonisation. The onus instead lies with the strength of civil society, backed up by the protective powers of an independent South African judiciary.

Microfacies and Reservoir Connectivity of Shore Sandbar, Southern Indus Basin, Pakistan

Shore sand bar reservoirs have attracted much attention as one of the target intervals with the greatest potential for petroleum exploration and development in marine sedimentary basins. Nevertheless, due to lack of effective research methods, it is difficult to analyze the rapid lateral change and heterogeneity in a sand bar reservoir, which has a major impact on the efficient petroleum development that seriously restricts the rolling evaluation and efficient development of sand-bar reservoirs. In this study, based on integrated analysis of cores, thin sections, logging, 3D seismic data, production test and dynamic data, through a combination analysis of drilling and seismic interpretation data—the petromineral composition, microfacies and reservoir connectivity of the shore sand bar in the southern Indus basin are investigated, which is used for the fine description of the sandbar reservoir. The results show that the shore sand bar is located in a relatively high-energy shore sedimentary environment, which is conducive to forming a favorable lithologic reservoir. Four sedimentary microfacies types are identified, including center bar, bar edge, inter bar and local mudstone interbeds. The sandbar microfacies are changed rapidly, and different microfacies types overlap each other, especially the inter bar and local mudstone interbeds that overlap and intersect in the center bar and bar edge, which significantly reduces the internal reservoir connectivity as well as intensifying the heterogeneity of the sandbar reservoir. The sandbar reservoir is not connected transversely, the physical properties are changing rapidly, and the sandbar reservoir is cut into several relatively independent oil reservoirs.