Lateral Loading Conditions Research Articles

Intradiscal cement leakage (ICL) increases the stress on adjacent vertebrae after kyphoplasty for osteoporotic vertebra compression fracture (OVCF): a finite-element study

This study aimed to explore the biomechanical effects on adjacent vertebra of thoracolumbar Osteoporotic Vertebra Compression Fracture (OVCF) after Percutaneous Kyphoplasty (PKP) with intraoperative intradiscal cement leakage (ICL) by applying a Finite-Element Analysis. We collected pre- and post-operative computer tomography (CT) images of a 71-year-old female patient with single T12 OVCF, who underwent an intraoperative cement leakage into the T12–L1 disc. Three-dimensional finite element models of thoracolumbar spine (T10–L2) were built with the support of Materialise Interactive Medical Image Control System (MIMICS) and ABAQUS software. The stress on adjacent vertebrae and endplates under the uniform compressive pressure (0.3 MPa) and during different loading moments were analyzed. The three-dimensional finite element models reveal an asymmetrical distribution of von Mises stresses on the adjacent endplate unaffected by the surgical intervention. The maximum von Mises stress on adjacent vertebral bodies increased during different loading conditions, especially for lateral bending and rotation loading conditions, whereas the maximum von Mises stress on distal non-treated vertebrae decreased on anteflexion and backward extension loading conditions. Post-operative adjacent vertebra compression fractures after PKP with intraoperative intradiscal cement leakage (ICL) may be closely related to the biomechanical changes of adjacent vertebrae of thoracolumbar OVCF, and it may increase the risk of postoperative fracture.

Inclination Effect of Cyclic Load Synchronous with Lateral Static Load on Pile Group in Sandy Soil

In general Pile foundations are often subject to more than one load in nature. Two loadings, when simultaneous, cause serious problems in the bearing capacity. Therefore, the major objective of this study is to assessment the performance of piles under inclined cyclic loads simultaneous with static lateral loads in sandy soil with a relative density of 70%. A laboratory investigates were conducted to determine effect of several factors on group pile performance model (2×2), including: the ratio of spaces between piles (i.e. 3D, 5D, 7D), influence of inclination angles of cyclic loading (i.e. 0°, 10°, 20°, 30°), the cyclic load ratio (i.e. 20%, 40%, 60% and 80%) and the effect of the presence of a static lateral load on the cyclic load. In light of the findings, the presence of the static load with the inclined lateral cyclic load has a positive effect on the deep foundations where the lateral deflection was reduced by an average of 54% for the three spaces. Also the lateral deflection at combined lateral loading decreases with increasing pile spacing, the percentages of decreases in the lateral deflection were (16%, 73%, 75% ) for spacing (3D, 5D, 7D ) respectively

In-Vitro Comparison of Fracture Strength of Endocrowns and Overlays in Endodontically Treated Teeth Manufactured with Monolithic Lithium Disilicate and Zirconia.

To evaluate the fracture strength and the failure mode of endodontically treated molars restored with monolithic lithium disilicate and zirconia endocrowns and overlays. A total of 48 extracted mandibular molars were endodontically treated, decoronated 2 mm above the cementoenamel junction and divided into four 12-specimen groups. Group ELD: lithium disilicate endocrowns. Group EZ: monolithic zirconia endocrowns. Group OLD: lithium disilicate overlays. Group OZ: monolithic zirconia overlays. Overlays did not extend in the pulp chamber and endocrowns extended in the pulp chamber 2 mm. After adhesive bonding of the restorations, the specimens were subjected to thermocycling (×5000 cycles) and then to fracture resistance testing at lateral static loading (1 mm/min) at a universal testing machine. The failure mode of the specimens was qualitatively evaluated. Differences in means were compared using with t-tests for independent samples or Mann-Whitney test (p < 0.05). Weibull distribution analysis was also performed. Group ELD showed significantly higher fracture strength than all other groups (p = 0.001), and the highest Weibull modulus. Conclusions: Lithium disilicate endocrowns exhibit higher fracture strength and are more reliable compared to the other types of restorations examined. Endocrowns had more catastrophic failures compared to overlays.

Behaviour of bio-inspired grouped battered minipiles under lateral loading in clay

The field of bio-inspired geotechnics has been growing in response to the demand for foundations that are sustainable and yet have improved load-bearing capacities. This study aims to address the gap in a specialised adaptation of root system architecture for designing resilient foundations. The lateral load behaviour of one such novel grouped battered minipile configuration is evaluated in this study based on full-scale field testing and numerical modelling to report the unknown increase of load capacity caused by shape modification. First, three single minipiles battered at 0° and 25° were subjected to static lateral loading in fine-grained soil. The strain profiles along the individual minipile shafts were obtained using optic fibre sensors. Consecutively, full-scale lateral load tests on two types of minipile groups were also performed; one group had a configuration of two 25° battered minipiles perpendicular to the direction of loading mimicking a tree-root system, and another conventional group had two positive and negative battered minipiles. A numerical model was developed to investigate the effect of pile spacing and obtain soil pressures, bending moments and axial forces of the battered minipile groups. Results show that increased bearing area and higher engagement of soil volume for the novel minipile group with two perpendicular battered minipiles were larger than the conventional minipile group; thus, the former offered higher lateral resistance. The deflection pattern, bending moment and p-y curves showed a shadowing effect in stiff clay for battered minipile groups at a pile head spacing of three times the minipile diameter.

Model experiment and numerical analysis of horizontal subgrade reactions acting on flexible walls

A method of reinforcing breakwaters with piles has been proposed. In this structure, designing piles as passive piles is important. Although most previous studies on horizontal subgrade reactions have been limited to the deformation mode of walls, the subgrade reaction to the wall is known to depend on the deformation mode of the wall. Herein, we investigated the changes in the subgrade reaction due to different deformation modes of the wall using model loading experiments and finite element analysis. The model ground was simulated using an aluminum rod mass, and an aluminum plate was used for the wall model. The model ground height was set to the horizontal ground condition with a 200 mm step at the front and rear of the wall. Lateral loads were applied simultaneously to the wall at two different depths. By controlling the ratio of the two levels of the lateral load applied to the wall, the deformation mode of the wall was altered. The experimental results indicated that the magnitude of the subgrade reaction at the same deflection depended on the deformation mode of the wall. The elastoplastic finite element analysis results of the lateral pile-head loading experiment in the horizontal ground condition exhibited good agreement with the experimental results. Under the two-point loading condition, the behavior of the wall was significantly different for cases in which the deformation mode differed from that of the lateral pile-head loading condition. By comparing the behavior of the ground around the wall, we discovered that the shear deformation of the ground differed depending on the deformation mode.

Response of laterally loaded finned piles in sand

This paper investigates the response of finned piles in sand subjected to static lateral load through laboratory tests and full-scale field tests. Firstly, model tests were carried out on free headed single piles of different shaft diameters with and without fins in sand to explore the performance of the piles under lateral loading. The results obtained from monotonic loading tests on three series of piles of three different combination of fins and pile shaft diameters were presented. The effect of fins on improving the stiffness and ultimate lateral capacity of the piles was discussed. An equivalent diameter was proposed for a finned pile, which enabled the experimental results to be back calculated using an available elasto-plastic solution for laterally loaded piles in sand. Secondly, field tests were conducted on laterally loaded Starfin screw piles in loose to medium dense sand. The proposed approach was then used for the analysis of the measured response of Starfin screw piles and further validated against measured test results from fully instrumented finned piles in overconsolidated dense sand. The results show that the proposed equivalent diameter and approach for the analysis of finned piles provided the most satisfactory match to the measured data, ranging from the initial elastic state to the ultimate limit state.

A new hollow solenoid receiver compatible with the global double-D transmitter for EV inductive charging.

Inductive power transfer (IPT) technology is a promising solution for charging the electric vehicles (EVs) by enabling an EV to charge its energy storage system (battery) without any connecting wires through magnetic coupling. This paper proposes a new receiver design named Hollow Solenoid receiver that is compatible with the standard double-D transmitter defined by the SAE J2954 standard. A deep design analysis for the proposed Hollow Solenoid receiver is presented to define the optimum design parameters for coil (inductances, number of turns, dimensions, wires, etc.) and ferrite core (dimensions, number, arrangement, etc.). Several WPT3 (11.1kVA) solenoid receiver (SR) designs were presented and analyzed based on efficiency, weight, size, volume, and cost. The performance of the proposed SR was compared with the global Double-D receiver (DDR) presented by the SAE J2954 standard under different lateral and rotational alignment and loading conditions considering coupling factor, transmission power and efficiency, and stray electromagnetic fields (EMFs). The entire IPT system including coils, compensation network, power converters, controls, and battery load was modeled and analyzed for both SR and DDR coils. The results reveal that the proposed SR is compatible with the global DD transmitter at different alignment and loading conditions and is able to transmit the desired power (11kW) at an efficiency > 85%. Hollow SR design shows the highest efficiency and lowest size, weight, and cost compared to DDR and other designs.

Nonlinear dynamic seismic analysis of a modern concrete core wall building in Los Angeles using the BTM‐shell methodology

AbstractThis paper discusses the nonlinear dynamic seismic response of a 14‐story reinforced concrete core wall building designed with the prescriptive requirements of the 2019 California Building Code for a near‐fault site in Los Angeles, California, simulated with a detailed nonlinear analysis of the complete structure and subjected to an ensemble of three‐component ground motion input. The study follows up on a recently published work by the authors, which examined the response of the specific building to static lateral loads. The nonlinear model of the building was developed in the software FE‐Multiphys using a shell‐element implementation of the beam–truss model (BTM). The BTM has been extensively validated through prior studies for planar, flanged, and coupled walls under static and dynamic loading. The building model was subjected to an ensemble of ground motions scaled at the design and risk‐targeted maximum considered earthquake levels. The vertical ground motion component and the out‐of‐plane shear degradation of wall piers were included in the simulations. The analyses elucidate the profound effect of nonlinear flexure–shear interaction and of the multidirectional behavior of the flanged coupled core wall on the evolution and localization of damage and on residual deformations. The coupling behavior between the core wall, the slabs, and the columns is also analyzed, and the importance of modeling the nonlinear behavior of all slabs for the residual damage evaluation is demonstrated. The aim of this study is to improve the understanding of issues arising from prescriptive design requirements as well as of issues associated with limitations of standard nonlinear seismic analysis.

Factors affecting axial and lateral load transfer of hollow fibre-reinforced polymer piles in soft clay

ABSTRACT The growing interest in the long-term performance of pile foundations and their ability to resist the negative effects of water exposure and aggressive environmental conditions has led to considering non-corrosive materials such as fibre-reinforced polymer (FRP). The most common applications are light-bearing structures in waterfront environments, while applications for larger structures have not been widely accepted in industry due to the lack of long-term records and design guidelines available. In this study, a numerical model using the finite element method was developed to simulate small-scale load tests of hollow carbon-fibre reinforced polymer (CFRP) and glass-fibre reinforced polymer (GFRP) piles in soft clay. The findings of this research indicate that the number of FRP layers impacts loading behaviour significantly, while inner tube soil height has a reasonable influence on axial load response and fibre orientation has a minor effect under lateral load conditions.

Axial and lateral bearing capacity assessment of bored piles on medium-dense sand and liquefiable potential based on numerical simulation

Liquefaction on bridges can cause structural failure due to loss of soil strength. The Showa Bridge that collapsed in 1964 Niigata earthquake was caused by buckling in piles as the soil layer liquefied and friction losses. In addition, there was a case of Palu IV bridge collapse in Indonesia during the recent 2018 Palu earthquake, which indicated have been affected by earthquakes and liquefaction. This study examines the reliability of the bored pile foundation of the Kretek 2 Bridge in Bantul Regency, Yogyakarta Special Region Province, for axial and lateral bearing capacity. This research method uses the soil structure interaction and 3D numerical simulation by Midas Civil and Midas GTS NX pile modeling. The pile driving analysis and lateral static loading test were also conducted, which can be compared to MIDAS results. For the foundation modeling result, there is an increase in axial and moment forces but a decrease in shear forces during liquefaction. While the lateral displacement increases significantly in the liquefaction state, foundation performance is still stable. Therefore, the foundation of the kretek 2 bridge is sufficient to support axial and lateral load both in a static state and a liquefaction state.

Calibrating resistance factor for LRFD of deep foundation under lateral loading condition with serviceability limit state

Deep foundations are often used to support bridges and buildings when the surface soils are not sufficiently strong. In this study, the resistance factor (RF) in the load and resistance factor design (LRFD) for laterally loaded drilled shafts as deep foundation was calibrated and proposed. The serviceability limit state (SLS) associated with allowable displacement was targeted as it frequently governs the design of deep foundation. For this purpose, a database was established for rigid piles, such as drilled shafts, by collecting various load test results from full-scale field tests, centrifuge tests, and 1-g model tests. The normalized load–displacement curves were introduced, and uncertainties were captured and characterized based on the normalized hyperbolic relationship. The statistical properties of load and resistance were evaluated and introduced into the Monte Carlo simulation, which was performed for calibrating RF according to the allowable displacement and target reliability index. The relationship between the SLS RF and the allowable displacement was proposed and compared with the factor of safety for the conventional design method for laterally loaded drilled shafts.

Theoretical model to predict the seismic drift concentration effect for self-centering-braced frame

This study is motivated to predict such drift concentration effects for SCB frames with the perfect flag-shape hysteretic behavior. Nonlinear time history analyses are conducted to compare and elucidate different deformation mechanisms between BRB and SCB frames. An elastic-plastic static model is established to predict the static drift concentration factor (DCFS) for the SCB frame under static lateral loads, where influential parameters include the column-to-frame stiffness ratios, α, and the SCB's post-yielding stiffness ratio, βk,2. To capture the dynamic loading effect, a regressive formula is further developed as the dynamic amplification factor by normalizing the dynamic drift concentration factor (DCFD) with the DCFS under static loads. The results show that unlike BRB frames with drift concentrated in the bottom story, SCB frames often feature peak story drifts in the top story. As opposed to BRB frames, the equivalent lateral loads do not feature an inverted triangle distribution but a parabolic distribution along the building height. The drift concentration effect for the SCB frame is reliably predicted by multiplying static DCFS with the corresponding closed-form formula for the dynamic amplification factor. The predicted DCFD is also utilized to identify a design range of βk,2 (i.e., 0.2–0.4) to effectively control the peak story drift and drift concentration for SCB frames.

Experimental and Numerical Study of the Behavior of RC Shear Wall with Opening Using Concealed Stiffeners

A shear wall becomes weak when an opening is provided in it. It is important to provide some arrangement in the shear wall having an opening for recovering strength loss due to the opening. It may be recovered by providing some steel profiles around the opening or at weaker sections in the shear wall having an opening. At first, the identification of weaker sections in the shear wall having an opening is important and then, the wall can be made stronger as the shear wall without an opening by strengthening weaker sections. In the present study, the performance of a shear wall having an opening subjected to horizontal cyclic loading along the plane of the shear wall in the presence of concealed stiffeners is investigated. The reduced models of shear walls with openings were tested under axial and lateral load conditions. Load-carrying capacity, deformation behavior and strain behavior of shear walls were studied with experiments and the validation of the results was made with general-purpose finite element software ANSYS. Significant improvements were observed in strength, deformation and strain behavior of a shear wall having a central opening using concealed reinforced concrete (RC) stiffeners and steel tube stiffeners. KEYWORDS: Shear wall, Strength, Stiffness, Strain, Openings, Stiffeners.

Behavior and modeling of large-scale concrete-filled FRP tubes with longitudinal steel rebars under lateral impact loading

Fiber-reinforced polymer (FRP) has been utilized extensively as a confining material for concrete in civil engineering. Concrete-filled FRP tubes (CFFTs), consisting of a FRP tube, a concrete core and optional longitudinal rebars, are particularly attractive to be used as bridge piers in harsh environments. Most studies on CFFTs have been focused on their behaviors under static loading conditions. To extend existing studies, three identical large-scale CFFTs with longitudinal steel rebars (SR-CFFTs) were investigated experimentally, two of which were tested under lateral impact loading and one was under lateral static loading. To compare the confining behavior between FRP tube and steel stirrups, three identical large-scale reinforced concrete (RC) columns with approximately the same hoop confinement stiffness as SR-CFFTs (i.e., steel stirrups for RC columns, FRP tube for SR-CFFTs) were tested as companion specimens. The test results indicated that, (1) under lateral static loading, the RC column failed with a shear-failure manner, while the SR-CFFT specimen failed with combined bending and shear failure characteristics; (2) under lateral impact loading, the shear-dominant failure mechanism was evident for RC columns, while the failure mechanism of SR-CFFTs was flexural-dominant owing to the effective hoop confinement provided by FRP; (3) under the same impacting velocity, the SR-CFFT specimen had much less damage and much less lateral displacement than the corresponding RC column. The established FE models could provide reasonably accurate predictions for the dynamic behaviors, the impact force–time history curves and the column deformations for both RC columns and SR-CFFTs. Parameter studies were conducted to analyze the effects of the concrete strength, the longitudinal steel ratio, the impact velocity and the impact mass.

A macro‐element with bidirectional interaction for seismic analysis of unreinforced masonry walls

AbstractPrior to implementing retrofitting measures for seismic action, it is necessary to evaluate the global capacity of unreinforced masonry (URM) buildings. Even with simplified assumptions, equivalent frame (EF) modeling adequately captures global responses and failure mechanisms in existing buildings, making it a popular modeling strategy among structural engineers. However, macro‐elements employed in the EF modeling of URM walls consider in‐plane (IP) and out‐of‐plane (OP) behaviors separately by decoupling their interaction and require independent verification for OP failure involving limit analysis. Such decoupling of interaction is justifiable if proper wall‐wall/wall‐floor connections and rigid‐diaphragm action of slabs are ensured; however, OP failure is likely a result of inadequate connections. Multiple components of ground motion excitation and plan eccentricity in buildings can activate bidirectional interaction in such circumstances. Due to OP damage, the interaction reduces the full IP strength of a URM wall, resulting in overestimating its lateral capacity. This paper proposes a frame‐like 3D macro‐element incorporating the effect of OP action on the IP shear response of URM piers under static and monotonic lateral loads. Only two parameters modifying IP shear stiffness and capacity are required to account for the interaction. Analytical expressions for the interaction parameters are proposed from a detailed micro‐modeling study. The paper also demonstrates, within the EF modeling, the applicability of the proposed macro‐element for seismic analysis of regular URM shear walls with openings.

Nonlinear time history seismic analysis of inelastic 3D frame buildings in a reduced modal space

This research investigates the formulation of a reduced modal space for the nonlinear dynamic seismic analysis of elasto-plastic 3D frame buildings. Starting from a full finite element model, the modal shapes of the reduced model for the kinematics are selected as the relevant linear elastic modes of the generalized stiffness/mass linear eigenvalue problem in terms of participation factor plus collapse mechanisms associated to appropriate static lateral loads. The internal forces are evaluated on the full model to guaranty an accurate description of the constitutive laws. The equations of motion are then projected in the modal space for the step-by-step solution by a Newmark average acceleration scheme. The advantage is that the Newton iteration of the implicit method are carried out by inverting only the reduced tangent matrix. The proposed reduction method is tested for a reinforced concrete building varying frequency content, direction and amplitude of the ground motion. Accuracy and robustness are demonstrated employing a few tens of modes, including elastic modes and plastic collapse mechanisms. The need for plastic modes for describing the structural dynamics in case of seismic actions leading to significant plastic excursions is highlighted, together with the limits of simplified approaches, as the pushover analysis, based on the hypothesis of shape conservation in the inelastic range regardless of the building regularity.

Seismic behaviors of tailings and recycled aggregate concrete-filled steel tube columns

To alleviate the shortage of river sand and the pollution of construction waste, this paper proposed the tailings and recycled aggregate concrete (TRAC) and its application in concrete-filled steel tube (CFT) columns. Six full-scale TRAC filled square steel tube (TRACFST) columns were tested under axial static load and lateral cyclic load, and the results were verified by the finite element method(FEM). The principal parameters were substitution rate of RAC (0%, 50%, 100%) and axial load ratio (0.3, 0.5). The failure mode of the specimens was presented. Based on the experimental data, the hysteresis curves, skeleton curves, ductility, energy dissipation capacity, and stiffness degradation of the specimens were analyzed. The difference of peak bearing capacity of specimens with different RAC substitution rates was no more than 5%. The average ductility coefficient of the specimens with 100% substitution rate increased by 1%-7% compared with the specimens with 0% substitution rate. The TRACFST columns exhibit remarkable seismic performance.

An approach for 2D modelling of laterally loaded piles

Despite a considerable progress in the analysis and design of monopiles, many methods are based on complex mathematical structures with doubtful or hard assumptions to verify. Therefore, there is still a need for simple and yet accurate methods for the analysis of monopiles under drained and undrained lateral cyclic loading conditions. In this work, a simple yet efficient two-dimensional modelling approach for the analysis of monopiles is proposed. To account for out-of-plane frictional forces, counter-forces derived from virtual frictional forces generated at the out-of-plane pile interface are applied along the pile length together with the scaled pile stiffness. The predictive capabilities of the proposed approach were validated by back-calculating two different experimental sets. The first consists of a small-scale field monopile test on a coarse-grained soil subjected to lateral cyclic loading under drained conditions. The second is a centrifuge test involving a fine-grained soil subjected to lateral cyclic loading under practically undrained conditions. Simulation results with the proposed approach suggest an accurate prediction of pile displacements and bending moments under both drained and undrained lateral cyclic conditions. The method is, however, unable to reproduce pore water pressures generated behind the pile in low permeability materials.

The p-y model of single pile foundation for OWTs under combined lateral environment loading and earthquake in saturated sand

A series of centrifuge tests were conducted on offshore wind turbines (OWTs) subjected to combined static lateral loading and the earthquake (LEAP wave) to obtain p-y curves (where p is the soil resistance and y is relative displacement between pile and soil), and a simplified beam on Winkler foundation (BNWF) model was proposed. The p-y curves are to investigate the influence of static lateral loading on the dynamic pile-soil interaction, and the BNWF model is to verify the p-y curves and to predict the after-shaking horizontal displacement. It's found that the dynamic p-y curve of shallow soil oscillated and moved to the right due to the influence of lateral loading; meanwhile the LEAP wave resulted in liquefaction of the surrounding soil and the p-y curve moved to the lower right, namely, the soil resistance decreased yet the displacement kept increasing. The BNWF model uses a hyperbolic function to fit the experimental p-y curves, and two parameters in the p-y curves, namely, the initial modulus of the subgrade reaction and the ultimate subgrade reaction, were connected with the excess pore pressure ratio (EPR). The comparison between the model and the test results verifies its effectiveness in predicting the after-shaking horizontal displacement.

BEARING CAPACITY AND SLIDING RESISTANCE OF SPREAD FOUNDATION UNDER VERTICAL AND LATERAL COMBINED LOAD

To clarify behavior and sliding resistance of a spread foundation under combined load, static vertical loading test, and static vertical and lateral combined loading tests were conducted on a spread foundation on sand. The sliding resistance under the combined load was caused by the soil failure beneath the foundation. After the peak of the lateral resistance, settlement and horizontal displacement increased although vertical and lateral load did not increase. When the vertical load is less than about 1/2 of the ultimate bearing capacity, the vertical load could be retained and the horizontal displacement was greater than the settlement.