Large Horizontal Displacements Research Articles

Analysis of Factors Affecting Bearing Capacity of Large Diameter Single Piles of Offshore Wind Power under Earthquake Loads

The offshore wind turbine single pile foundation structure is simple and easy to install, but in the earthquake environment, large horizontal displacement is easy to occur, which affects the safe operation of offshore wind turbines. For this reason, the bearing characteristics and influencing factors of large-diameter single-pile offshore wind power under earthquake load are analyzed. The Mohr-Coulomb model is used as the model. The ABAQUS is used to construct the large-scale single-pile finite element model of offshore wind power. Loads and analysis of bearing characteristics and influencing factors of large-diameter single-pile offshore wind power under seismic loading. It is found that the increase of pile foundation depth will significantly reduce the horizontal displacement at the top of single pile. After increasing to a certain extent, it has no significant effect on the development of horizontal deformation of large diameter single pile; with the increase of pile diameter and wall thickness, The deformation of large diameter single pile foundation is reduced, but the influence of the pile foundation thickness on the horizontal deformation of the large diame-ter single pile foundation is no longer significant.

Stacking interactions of borazine: important stacking at large horizontal displacements and dihydrogen bonding governed by electrostatic potentials of borazine.

Potential energy surfaces of borazine-benzene and borazine-borazine stacking interactions were studied by performing DFT, CCSD(T)/CBS and SAPT calculations. The strongest borazine-benzene stacking was found in a parallel-displaced geometry, with a CCSD(T)/CBS interaction energy of -3.46 kcal mol-1. The strongest borazine-borazine stacking has a sandwich geometry, with a CCSD(T)/CBS interaction energy of -3.57 kcal mol-1. The study showed that borazine forms significant stacking interactions at large horizontal displacements (over 4.5 Å), with energies of -2.20 kcal mol-1 for the borazine-benzene and -1.96 kcal mol-1 for the borazine-borazine system. The strength of interactions and their geometrical preferences can be rationalized by observing the electrostatic potentials of borazine and benzene, which is in agreement with SAPT analysis showing that electrostatics is the most important energy component for borazine stacking. All the interactions found in crystal structures of borazine and related compounds were identified either as potential curve minima or the geometries obtained from their optimizations. We also report a new dihydrogen bonding dimer with a CCSD(T)/CBS interaction energy of -2.37 kcal mol-1, which is encountered in the borazine crystal structures and enables the formation of additional simultaneous interactions that contribute to the overall stability of the crystals.

Benefits of Seismic Isolation for Nuclear Structures Subjected to Severe Earthquake

The Fukushima accident has reiterated that the seismic safety is a clear necessity in the design of nuclear power plants. To overcome the weaknesses of the plant design, appropriate measures or interventions have thus to be put in place to improve the nuclear safety. In this study, seismic isolation, widely adopted for conventional constructions, is considered as retrofit measure to provide superior performance of plant itself, even when exceptional events occur. In this paper, we numerically investigate the dynamic behaviour of a Small Modular Reactor (SMR) plant subjected to 0.6g PGA; in doing that time-history analysis has been performed assuming the reactor building with and without isolators. For that purpose, a suitable FEM model has been implemented to provide in-structure response spectra at safety relevant locations and subsystem supports. Adequate steel and concrete properties as well as isolators properties, experimentally determined, have been assumed. Results have shown the benefits of seismic isolation for NPP that can so sustain levels of loading beyond the design input and demonstrated that failure of an isolation system cannot occur before failure of the isolated structure. However, the large horizontal displacements of the structure require appropriate considerations in the layout and interfaces for interconnected systems.

Interface shear characteristics of dredger fill and concrete using large size direct shear test

A large-size direct shear test was conducted to test the interface of dredger fill and concrete. The effect that concrete strength and the density of dredger fill have on the properties of interface is then analyzed. Digital photography was used to record soil particles of dredger fill moving near the interface, and the particle images were analyzed by particle image velocimetry technique. The results of the tests show that the shear strength of interface fit the model laid out in the Mohr–Coulomb theory. The relationship between shear displacement and shear stress fit the hyperbola model. Soil particles of dredger fill near the interface have large horizontal displacement and obvious vertical displacement of the particles. Under high normal stress, concrete strength has significant influences on the shear strength of interface. Density of dredger fill has great effects on the shear strength of interface.

Flexural strength of AAC masonry with bed joint reinforcement

AbstractThe paper presents the results of comparative investigations of flexural strength of unreinforced and reinforced autoclaved aerated concrete (AAC) masonry. The plane of masonry failure was perpendicular to the bed joints plane. Reinforcement in the form of steel wire, glass, and basalt fibers placed in masonry bed joints influenced the higher flexural strength and crack resistance of masonry specimens. Reinforced masonry showed plastic nature after cracking allowing for large horizontal displacements and transferring the substantial loads perpendicular to the surface of masonry in relation to the unreinforced masonry. For most reinforced masonry specimens, the strengthening after cracking was observed which means that the maximum value of load occurred in the cracked masonry.

Overexploitation of groundwater resources in the faulted basin of Querétaro, Mexico: A 3D deformation and stress analysis

The City of Querétaro is located on a continental basin filled since the Oligocene with lacustrine and alluvial sediments, pyroclastic deposits, and interbedded fractured basalts. The graben structure of the basin was formed by two major North-South trending normal faults, among which the thicknesses of the filling materials vary many tens of meters in close distances. Hence, important differences of hydraulic and mechanical properties characterize the various geologic units. Groundwater has been strongly withdrawn over the last three decades in the study area, with a decline of the piezometric level exceeding 100 m. Because of the high variability of the geologic deposits, the piezometric decrease and consequently the effective stress increase are characterized by a large spatial variability. Piezometric variations are also due to faults that strongly impact on groundwater flow dynamics. The deformation and effective stress variability has caused large differential subsidence causing ground fracturing that has damaged the urban infrastructure of the City of Querétaro. This complex geological setting has been properly accounted into a three-dimensional (3D) flow and geomechanical modeling approach to quantify the displacement, deformation, and stress fields caused by water withdrawal. The static geologic model was accurately defined using geological logs from extraction wells, field mapping of faults, fractures, and the integration of major structures reported in previous geophysical works. The model has been calibrated using observed groundwater levels and land settlement records. The simulations have spanned the period from 1970 to 2011. The modeling results highlight that the areas where large differential subsidence and horizontal displacements developed correspond to the portions of the city where ground fractures are observed. Normal and shear components of the stress field changes accumulate along the discontinuity surfaces at depth, providing evidence that large piezometric declines can be a key factor triggering the fault reactivation. The spatial relationship between major withdrawals, discontinuities of the geologic structure, and accumulation of large stress and strain fields clearly emerged from the outcomes of the 3D geomechanical model.

Inelastic response of base-isolated structures subjected to impact

While base isolation provides enhanced structural and non-structural seismic performance, there are still concerns regarding large horizontal displacements in extreme earthquakes. Excessive horizontal displacements may induce detrimental pounding of base-isolated structures against the moat wall or the restraining rim of friction pendulum bearings, resulting in yielding or even collapse of the superstructure. This paper uses a simplified two degrees-of-freedom model to investigate the inelastic responses of various base-isolated superstructure designs subjected to impact. It is found that the stiffness of the superstructure largely dictates its response to the transient impact force. The stiff superstructure is very sensitive to the impact force and develops considerably large ductility demands compared to the case with the absence of impact. However, for the flexible superstructure, the ductility demand is more dependent on system yielding under the input motion and does not increase as dramatically when impact is introduced, indicating that it is less sensitive to impact.

Structural style, formation of low angle normal fault and its controls on the evolution of Baiyun Rift, northern margin of the South China Sea

Recent studies of high-resolution seismic reflection profiles in the northern rifted margin of the South China Sea revealed that low angle normal faults dominated the structural evolution of deepwater basins rather than high angle normal faults solely as was previously assumed; however, none of the studies proposed kinematic restorations of the fault system and the relationship to continental margin formation. The Baiyun Rift is located in the slope of the northern margin of the South China Sea underlain by extremely thinned continental crust. It is filled with a relatively complete sequence of Cenozoic sediments up to 10 km and has been considered the best-documented deepwater basin. Basin-wide 3D seismic data together with the available deepwater well data have allowed the structural framework to be built and tectono-stratigraphic history of the Baiyun Rift to be traced in detailed from the rift stage; a quantitative study of the primary geometry and kinematics of the major faults can be performed consequently. Results show the inception of the rift is characterized by faults slipped at high angles; the later stage (mid-Eocene) of intensive extension is dominated by a fault system with large horizontal displacements (>10 km) and initial low dips (<30°). The observations can be best explained by a low angle normal faulting (faults started out at shallow angles during mid-Eocene or being rotated from high angles) following a scattered high angle normal faulting. As a consequence, the polyphase faulting created a large accommodation space vertically and horizontally and formed a deep and wide shape of the Baiyun Rift. Besides, the phenomenon that the cessation of the rift in the Baiyun Rift predated the final breakup of the continental margin suggests the timing of the rifting events along the northern margin of the South China Sea is non-instantaneous. This study implies the progressive deformation dominated by low angle normal faulting causes an uneven distribution of the continental crustal thickness and may favor the breakup location in the northern South China Sea.

Effect of super-structure frequency on the seismic behavior of pile-raft foundation using physical modeling

This paper presents the results of two physical test series, including shaking table and centrifuge modeling, on two super-structures with different frequencies and supported by piled raft foundations in a dry sand bed. While the height and weight of two super-structures were kept constant, the axial force and bending moment of piles, as well as horizontal displacement of super-structures were recorded during seismic loadings. The input seismic loadings were given different amplitudes and frequencies. The shaking table and the centrifuge test results indicated that the super-structure frequency strongly affected the pile-raft system responses. Based on the centrifuge test results, the super-structure had larger horizontal displacement, when the excitation frequency was close to system frequency with low base acceleration (0.14g), while subsequently, axial force and bending moment of piles increased. In high input base acceleration (0.4g), excitation frequency dominated the super-structure response, and larger responses occurred at smaller (1Hz) input excitation frequency.

RADAR Remote Sensing Combined with Continuous GPS Measurements for the Monitoring of Deformations of Geothermal Fields: A Proposed Methodology

Electricity generation from geothermal sources is associated with geothermal fluid extraction and re-injection, resulting in surface changes/displacements horizontally and vertically (uplift or sinking) (Eneva, 2009). Besides, previous geodetic monitoring of geothermal production sites have shown large subsidence and horizontal displacement at tribute to thermal contraction, pressure reduction in the reservoir, and/or changes in the local stress field (Heimlich, Masson, & Gourmelen, 2013). Conventional surveying methods employed to measure the deformations of structures with small and slow displacements have often provided in frequent though precise estimates of these deformations. With the development of high precision GPS methods and Remote Sensing, an alternative method for monitoring structural deformations is available. Continuous GPS measurements technique with its higher temporal resolution is complemented with RADAR remote sensing so as to cover larger areas spatially. Citing case studies, this paper fronts the application of RADAR Remote Sensing complimented with continuous GPS measurements as an ideal way of monitoring deformations of geothermal fields for better geothermal field management. A similar proposition has been forwarded for approval in the management of Olkaria Geothermal Field which houses the largest geothermal power plant in Africa.

Influence of Grid Reinforcement Placed In Masonry Bed Joints on Its Flexural Strength

The paper presents the test results of the flexural strength of masonry when plane of failure is perpendicular to the bed joints. Comparison tests of unreinforced specimens and specimens reinforced with steel wire, glass and basalt fibre grids applied in masonry bed joints showed the higher flexural strength and crack resistance of masonry reinforced in this manner and so loaded. Reinforced masonry exposed plastic character after cracking allow for large horizontal displacements and transfer the considerable loads perpendicular to their surface. The strengthening of masonry was observed in most tests of reinforced specimens leading to occurrence of the maximum load in after cracking phase.

Complex rupture process of the Mw 7.8, 2016, Kaikoura earthquake, New Zealand, and its aftershock sequence

The M7.8 Kaikoura Earthquake that struck the northeastern South Island, New Zealand, on November 14, 2016 (local time), is one of the largest ever instrumentally recorded earthquakes in New Zealand. It occurred at the southern termination of the Hikurangi subduction margin, where the subducting Pacific Plate transitions into the dextral Alpine transform fault. The earthquake produced significant distributed uplift along the north-eastern part of the South Island, reaching a peak amplitude of ∼8 m, which was accompanied by large (≥10 m) horizontal coseismic displacements at the ground surface along discrete active faults. The seismic waveforms' expression of the main shock indicate a complex rupture process. Early automated centroid moment tensor solutions indicated a strong non-double-couple term, which supports a complex rupture involving multiple faults. The hypocentral distribution of aftershocks, which appears diffuse over a broad region, clusters spatially along lineaments with different orientations. A key question of global interest is to shed light on the mechanism with which such a complex rupture occurred, and whether the underlying plate-interface was involved in the rupture. The consequences for seismic hazard of such a distributed, shallow faulting is important to be assessed. We perform a broad seismological analysis, combining regional and teleseismic seismograms, GPS and InSAR, to determine the rupture process of the main shock and moment tensors of 118 aftershocks down to Mw 4.2. The joint interpretation of the main rupture and aftershock sequence allow reconstruction of the geometry, and suggests sequential activation and slip distribution on at least three major active fault domains. We find that the rupture nucleated as a weak strike-slip event along the Humps Fault, which progressively propagated northward onto a shallow reverse fault, where most of the seismic moment was released, before it triggered slip on a second set of strike-slip faults at the northern end of the rupture. The northern and southern strike-slip fault domains have the same orientation but are spatially separated by >15 km. In our model, the low angle splay thrust fault is located above the slab and connects the strike-slip faults kinematically. During the aftershock phase, the entire fault system remained active.

Non-tectonic liquefaction-induced large surface displacements in the Aso Valley, Japan, caused by the 2016 Kumamoto earthquake, revealed by ALOS-2 SAR

We constructed and analyzed full 3-D ground surface displacement field associated with the 2016 Kumamoto (Japan) earthquake using satellite radar images from ALOS-2. Displacements reflect not only tectonic crustal deformation caused by main earthquake faults but also non-tectonic surface deformations. The largest deformations in the earthquake sequence were found in the Aso Valley, along the NW outer rim of the Mt. Aso caldera. Large, independent surface deformations occurred in three areas with diameters of 500 m–2 km in the Aso Valley, and each area was horizontally displaced by more than 2 m to the NNW. These areas are underlain by thick lake-bottom deposits of saturated silt with low penetration resistance. As the direction of the displacements was parallel to the ground slope in each area, the strong seismic motion of the earthquake most probably induced liquefaction in the lake-bottom deposits and the ground surface slid horizontally along the slope on the liquefied silt. Because the areas of the large displacements are closely related to the thickness and shape of the lake-bottom deposits, amplification of the seismic wave in these deposits likely contributed to the liquefaction. A seismograph installed at the Aso Valley recorded co-seismic movement within several seconds of the main shock, indicating a possibility of the strong seismic motion amplifying the horizontal displacement of this area. On the SSE side of the deformed areas, numerous graben-like ruptures developed. As these ruptures are caused by surface tension during the large horizontal displacement, they are not earthquake fault traces and the process of this deformation is non-tectonic.

Stability study on structural systems assembled by system scaffolds

This study investigates the stability of the structural systems assembled by system scaffolds. Loading tests were conducted on the indoor single-bay system scaffolds and the outdoor full-scale structural system assembled by system scaffolds. Test results were compared with the second-order inelastic analysis with semi-rigid joints to determine the reliability of various analytical parameters. The study reveals that, while the failure model of the single-bay two-storey system scaffold without diagonal braces is overall buckling failure of the structure, the failure model of the same structure with diagonal braces is buckling failure of the vertical standards between the upper and lower storeys. The critical load of the configuration with diagonal braces is about double that of the same structure without diagonal braces. At the moment of buckling failure of the outdoor full-scale two-row, two-bay, six-storey structural system assembled by system scaffolds, the vertical standards at the four corners appeared to have large horizontal displacements owing to without diagonal braces. However, the vertical standard in the center did not exhibit obvious horizontal deformation because it was reinforced with diagonal braces on four sides. In addition, the use of diagonal braces can significantly increase the load capacity of vertical standards. This study recommends that all vertical standards be reinforced with diagonal braces to ensure the load capacity of the structural systems assembled by system scaffolds. A second-order inelastic analysis with semi-rigid joints and various notional lateral forces is recommended to determine the critical loads of full-scale structural systems assembled by system scaffolds.

Synthesis, crystal structure and study of the crystal packing in the complex bis(4-aminopyridine-κN1)dichloridocobalt(II).

Despite the large number of reported crystalline structures of coordination complexes bearing pyridines as ligands, the relevance of π-π interactions among these hereroaromatic systems in the stabilization of their supramolecular structures and properties is not very well documented in the recent literature. The title compound, [CoCl2(C5H6N2)2], was obtained as bright-blue crystals suitable for single-crystal X-ray diffraction analysis from the reaction of 4-aminopyridine with cobalt(II) chloride in ethanol. The new complex was fully characterized by a variety of spectroscopic techniques and single-crystal X-ray diffraction. The crystal structure showed a tetrahedral complex stabilized mainly by bidimensional motifs constructed by π-π interactions with large horizontal displacements between the 4-aminopyridine units, and N-H...Cl hydrogen bonds. Other short contacts, such as C-H...Cl interactions, complete the three-dimensional arrangement. The supramolecular investigation was extended by statistical studies using the Cambridge Structural Database and a Hirshfeld surface analysis.

A true three-dimensional wellbore positioning method based on the earth ellipsoid

Abstract In view of the problems existing in the current wellbore positioning method, a true three-dimensional wellbore positioning method was presented, and an example for analysis was given. The current positioning method uses the grid north as the reference datum to the north, positions in the horizontal plane based on the map projection coordinates, and positions in the vertical direction based on the elevation coordinates. It has inherent defects and errors, as the two positioning methods above are independent of each other, and only use the constant meridian convergence and constant magnetic declination at the wellhead to calculate the borehole trajectory for the whole well. Based on the earth ellipsoid and its calculating principle, the transformation relationship between the wellhead coordinate system, geodetic coordinate system and elevation coordinate system was revealed, and the true three-dimensional wellbore positioning method using the true north as the reference datum to the north was presented. Analysis results of an example show that the current positioning method yields a smaller vertical depth and a larger horizontal displacement for the target, and produces larger errors compared with the true three-dimensional positioning method. The true three-dimensional positioning method has fundamentally solved the problems existing in the current positioning method, accurately positioning the relative location between the target and the wellhead, and significantly improves the accuracy and reliability of borehole trajectory design.

Numerical simulation tool for paving block structures assessed by means of full-scale accelerated pavement tests

ABSTRACTBlock pavements are an attractive alternative to asphalt and concrete pavements, especially in communal areas. Architects and urban planners would like to take advantage of various shapes, colours and textures of paving blocks in order to achieve a higher quality of urban space if the performance of block pavements could be better predicted to avoid large horizontal displacements of chipped stone corners and rutting. Unfortunately, the computational performance prediction of paving block structures is more complex than that for flexible pavements with homogeneous surface layers of asphalt concrete. The influence of the large number of vertical joints between paving blocks on the overall mechanical performance has not been considered sufficiently within computational tools yet. The proposed numerical simulation tool is able to take into account the complex mechanical behaviour of sand-filled joints as well as the non-linear mechanical behaviour of the underlying base courses. Joints are modelled using a Mohr–Coulomb-type friction model with the normal stresses non-linearly related with joint opening. Three different experimental set-ups were developed for the identification of the model parameters. The base behaviour was modelled using the Drucker–Prager cap model. The paper shows that the proposed tool predicts reasonable deformations and stresses in block pavements. The results of the simulations were compared with measured stresses from the full-scale accelerated pavement testing and a good agreement was observed.

Suggestion of an equation of motion to calculate the damping ratio during earthquake based on a cyclic procedure

Large horizontal relative displacements are naturally caused by seismic excitation, which is able to provide collisions between two adjacent buildings due to insufficient separation distance and severe damages due to impacts, especially in tall buildings. In this paper, the impact is numerically simulated and two needed parameters are calculated, including the impact force and energy absorption. In order to calculate the mentioned parameters, mathematical study is carried out to model an unreal link element, which is logically assumed to be a spring and dashpot to determine the lateral displacement and damping ratio of the impact. For the determination of the dynamic response of the impact, a new equation of motion is theoretically suggested to the evaluate impact force and energy dissipation. In order to confirm the rendered equation, a series of parametric studies are performed and the accuracy of the formulas is confirmed.

Coordinating Benzenes Stack Stronger than Noncoordinating Benzenes, even at Large Horizontal Displacements

Stacking interactions between two benzene molecules that coordinate transition metal ions within organometallic sandwich and half-sandwich compounds were investigated by performing Cambridge Structural Database (CSD) search and DFT-D calculations. Calculations of interaction energies revealed that stacking interactions between coordinating benzenes of sandwich (−3.69 kcal/mol) and half-sandwich compounds (−3.29 kcal/mol) are significantly stronger than the stacking interaction between noncoordinating benzenes (−2.73 kcal/mol). At large horizontal displacements (offset r = 5.0 A), these sandwich∥sandwich interactions are remarkably strong (−3.03 kcal/mol), while half-sandwich∥half-sandwich interactions are significantly weaker (−1.27 kcal/mol). The results of calculations are in good agreement with the data in the crystal structures from the CSD, where 76% of sandwich∥sandwich contacts have large horizontal displacements, which is significantly more than 46% of half-sandwich∥half-sandwich contacts arranged...

Parametric study of the wave-induced residual liquefaction around an embedded pipeline

Wave-induced liquefaction in a porous seabed around submarine pipeline may cause catastrophic consequences such as large horizontal displacements of pipelines on the seabed, sinking or floatation of buried pipelines. Most previous studies in relation to the wave and seabed interactions with embedded pipeline dealt with the wave-induced instaneous seabed response and possible resulting momentary liquefaction (where the soil is liquefied instantaneously during the passage of a wave trough), using theory of poro-elasticity. Studies for the interactions between a buried pipeline and a soil undergoing build-up of pore pressure and residual liquefaction have been comparatively rare. In this paper, this complicated process was investigated by using a new developed integrated numerical model with RANS (Reynolds averaged Navier–Stokes) equations used for governing the incompressible flow in the wave field and Biot consolidation equations used for linking the solid–pore fluid interactions in a porous seabed with embedded pipeline. Regarding the wave-induced residual soil response, a two-dimensional poro-elastoplastic solution with the new definition of the source term was developed, where the pre-consolidation analysis of seabed foundation under gravitational forces including the body forces of a pipeline was incorporated. The proposed numerical model was verified with laboratory experiment to demonstrate its accuracy and effectiveness. The numerical results indicate that residual liquefaction is more likely to occur in the vicinity of the pipeline compared to that in the far-field. The inclusion of body forces of a pipeline in the pre-consolidation analysis of seabed foundation significantly affects the potential for residual liquefaction in the vicinity of the pipeline, especially for a shallow-embedded case. Parametric studies reveal that the gradients of maximum liquefaction depth with various wave and soil characteristics become steeper as pipeline burial depth decreases.