Increase In Lateral Displacement Research Articles

Evaluation of liquefaction‐induced lateral spread displacement based on ensemble learning

Liquefaction‐induced lateral spread is a kind of ground deformation caused by soil liquefaction, which is a danger to houses, roads and other infrastructures. In order to systematically investigate the influence law of different parameters on lateral displacement, this paper establishes a numerical model of the seismic responses of gently sloping grounds through the open‐source finite element software OpenSees and carries out a large number of calculations considering various working conditions. Based on the calculation results, eXtreme Gradient Boosting (XGBoost) and random forest (RF) regression are used to build the proxy models for lateral spread displacement prediction. The finite element model was verified by using the multiple VELACS No. 2 centrifuge experiments. Finally, the model was interpreted using SHapley Additive exPlanation (SHAP) method. The results of the model training showed that both models were able to achieve a good fit to the numerical calculation results, with the RF model having a smaller prediction error for the centrifuge experiments. The model interpretation results showed that the modified cumulative absolute velocity (CAV5) was the most important input variable in the model, and the importance of ground slope (S), relative density (Dr) and thickness of liquefiable soil layer (HL) was relatively high. In addition, the influence of each parameter on the lateral displacement is consistent with the actual situation, reflecting the rationality of the model prediction process. In addition, the results showed that there is a threshold for the modified cumulative absolute velocity (CAV5) and Arias intensity (Ia) that leads to a significant increase in lateral displacement. The thresholds of CAV5 and Ia are 1.3 g s and 1.0 m/s, respectively. These thresholds are in good agreement with the thresholds for triggering the overall initial liquefaction of the soil layer determined by related studies, which provides a reference for the evaluation of liquefaction‐induced lateral displacement.

Electrohydrodynamic jet printed bioinspired piezoelectric hair-like sensor for high-sensitivity air-flow detection

Inspired by the highly sensitive hairs of creatures in nature, this work proposes a high-aspect-ratio piezoelectric sensor that is processed using electrohydrodynamic jet (E-jet) printing technology. A thin layer of piezoelectric material is directly written on the surface of tungsten steel microwire by E-jet printing. The piezoelectric material was crystallized by high-temperature annealing and fully bonded to the microwire. The annealed piezoelectric thin film was then sputtered with copper electrodes which forms a piezoelectric hair-like sensor with a diameter of 120 μm and an aspect ratio of 300. It was observed that the piezoelectric hair-like sensor generates 18 mV with a displacement of 100 μm. The output signal increases linearly with the increase of lateral displacement and velocity. It was examined that the piezoelectric hair-like sensor can detect airflow velocity as low as 0.01 m s−1, which shows a lower detection threshold compared to piezoelectric hair-like airflow sensors processed in other ways. In addition, the piezoelectric hair-like sensor allows for the detection of an airflow velocity of 10 m s−1 and a response time of 70 ms. The experimental results show that the piezoelectric hair-like sensor has high sensitivity, a wide detection range and rapid detection response, which is expected to be a high-performance sensor for biosensing and airflow monitoring.

Hysteretic behavior of concrete-filled bimetallic tube (CFBT) columns under combined loads

The experimental results on the hysteretic behavior of concrete-filled stainless steel (outer)-carbon steel (inside) bimetallic tube (CFBT) columns are presented in this paper. Five CFBT column specimens and one conventional concrete-filled carbon steel tube (CFST) column specimen were tested under combined constant axial compression and reversed lateral loads, and the main test parameters included the axial compression ratio and strength of the infilled concrete. The experimental results showed that, the failure characteristic of CFBT columns was close to that of CFST columns with the same parameters, which was featured by local outward buckling of the steel tube accompanied by concrete crushing at the corresponding location. No delamination of the bimetallic tube was observed during the whole loading process. The load versus deformation curves for all the specimens exhibited a plump shape without obvious pinching phenomenon, indicating favorable load-carrying and energy dissipation capacities. During loading, the strength of CFBT columns showed a stable degradation rate with the increase of lateral displacement. Both the yield load and peak load of CFBT columns tended to increase as either the axial compression ratio or concrete strength increased. The Eurocode 4 gave acceptable predictions of the strength of CFBT columns under combined loads.

Investigation on vertical stiffness reduction of thick rubber bearings under lateral displacement

Elastomeric bearings with thick rubber layers, called Thick Rubber Bearings (TRBs), can be used as three-dimensional (3D) isolators. During their design, the vertical stiffness is a critical parameter. This study focuses on exploring the parameters that influence the vertical stiffness reduction of TRBs and on developing a simplified method for its prediction. Four full-scale TRBs with various first and second shape factors (S1 and S2) were designed and subjected to axial tests under lateral displacement. Their vertical stiffness was determined. The experimental results showed that for bearings with a lower S1, the vertical stiffness under small lateral displacement increases and then decreases as the lateral displacement increases. Then, tests at the material and isolator levels were used to calibrate a finite element (FE) model of TRBs. A parametric FE study was carried out to investigate the effects of various parameters on the normalized vertical stiffness of TRBs over a wide range of lateral displacements. The study quantified the vertical stiffness reduction for different values of pressure, S1, and S2. It also evaluated code recommendations for the steel shims used in TRBs. Then, existing formulations were compared to numerical results and it was shown that they cannot accurately predict the reduction of the vertical stiffness of TRBs. Finally, an empirical formulation considering the variation in S1 and S2 of TRBs was proposed. The predicted results showed good agreement with the numerical data.

Lateral release associated with MPFL reconstruction in patients with acute patellar dislocation

ObjectiveMedial patellofemoral ligament (MPFL) injury occurs in the majority of the cases of acute patellar dislocation. The role of concomitant lateral retinaculum release with MPFL reconstruction is not clearly understood. Even though the lateral retinaculum plays a role in both medial and lateral patellofemoral joint stability in MPFL intact knees, studies have shown mixed clinical outcomes following its release during MPFL reconstruction surgery. Better understanding of the biomechanical effects of the release of the lateral retinaculum during MPFL reconstruction is warranted. We hypothesize that performing a lateral release concurrent with MPFL reconstruction will disrupt the patellofemoral joint biomechanics and result in lateral patellar instability.MethodsA previously developed and validated finite element (FE) model of the patellofemoral joint was used to understand the effect of lateral retinaculum release following MPFL reconstruction. Contact pressure (CP), contact area (CA) and lateral patellar displacement were recorded. abstract.ResultsFE modeling and analysis demonstrated that lateral retinacular release following MPFL reconstruction with tibial tuberosity-tibial groove distance (TT-TG) of 12 mm resulted in a 39% decrease in CP, 44% decrease in CA and a 20% increase in lateral patellar displacement when compared to a knee with an intact MPFL. In addition, there was a 45% decrease in CP, 44% decrease in CA and a 21% increase in lateral displacement when compared to a knee that only had an MPFL reconstruction.ConclusionThis FE-based analysis exhibits that concomitant lateral retinaculum release with MPFL reconstruction results in decreased PF CA, CP and increased lateral patellar displacement with increased knee flexion, which may increase the risk of patellar instability.

Seismic Pounding Response of Neighboring Structure using Various Codes with Soil-Structure Interaction effects: Focus on Separation Gap

Due to the high cost and less availability of land, the buildings are constructed adjacent to each other with a significantly smaller separation gap. Whenever seismic forces act on adjacent structures, they collide and cause significant structural and architectural damage. Soil-Structure Interaction (SSI) effects cause more complications in the adjacent structures. This paper assesses the gap distance between RC bare frame adjacent structures of varying heights in medium and soft soil with and without SSI to avoid the pounding effect of an earthquake. The main objectives are to find the separation distance between adjacent buildings by the provisions of FEMA 356, IS 1893 (Part 1):2002, IS 1893 (Part 1):2016 and EN 1998-1:2004. The separation gap between different codes was then compared to determine the minimum separation required to prevent pounding between the structures. The maximum lateral displacement on the roof and the time period of the adjacent buildings are compared with and without SSI. There is a significant increase in lateral displacement, separation distance, and time period considering SSI. It is found that the Indian code overestimates the separation distance. Thus, this study guides structural engineers to maintain a minimum separation distance between buildings erected on medium and soft soils in high seismic zones of India. Doi: 10.28991/CEJ-2022-08-02-09 Full Text: PDF

Analysis of a Monopile under Two-Way Cyclic Loading

A large diameter monopiles are commonly used as an offshore wind turbine (OWT) foundation to withstand lateral cyclic loads due to wind and wave action. In the present study, a two-dimensional finite element analysis was performed to evaluate the behavior of a monopile under two-way lateral cyclic loading. The centrifuge test carried out on a 0.7m diameter pile was being used to validate the constituent model. The parametric study was carried out on a monopile by varying the slenderness ratio (L/D = 4, 5, and 6) and load amplitudes (30%, 40%, and 50% of the ultimate pile capacity). From the load-displacement response of a monopile, it was observed that the measured accumulated displacement increases drastically for the first load cycle. For a given embedded length, the lateral displacement was observed to increase with an increase in load amplitude. For an embedded length of L/D = 4, the increase in load amplitude from 30% - 40% resulted in an increase in lateral displacement to 24%.

Experimental investigation into the seismic behavior of squat reinforced concrete walls subjected to acid rain erosion

Acid rain erosion will continuously deteriorate the physical and mechanical properties of materials and finally degrade the seismic performance of reinforced concrete (RC) structures. Nevertheless, the effect of acid deposition on squat RC walls, an important part of lateral force-resisting systems, has not been reported in existing research. Thus, in this paper, an artificial climate simulation method was used to accelerate the acidic attack process on four squat RC wall specimens with an aspect ratio of 1.0. Then quasi-static loading tests were conducted to observe their cyclic behavior under different acid rain spraying cycles (ARSCs). The results show that as ARSCs increase, the degree of degradation of concrete strength and the corrosion weight loss of steel bars have a rising trend, and the bearing capacity and deformation capacity of the squat RC walls deteriorate gradually. Simultaneously, the ratio of shear displacement to total lateral displacement increases, indicating a more noticeable shear failure characteristic with the addition of ARSCs. Moreover, the failure mode shifts from the mixed flexure and diagonal compression mode to the diagonal tension mode with a significant decrease in ductility and energy-dissipation capacity. It is also found that the degradation rate of the shear strength of squat walls under acid rain erosion is larger than that of the flexural strength, which may lead to the transition of failure mode.

Comparative Study of Indonesian Seismic Codes Applied on Vertically Irregular RC Building in High Seismicity Region

The Aceh earthquake suffering Indonesia in 2004, and some big ground motions afterward led the earthquake-resistant building standard provisions to be updated. The rise of ground motions increases the lateral forces, so reevaluating existing buildings is needed, especially for Irregular buildings, which are more vulnerable than the regular ones. This study investigates the increase of earthquake loads and the building response in the high seismicity region due to the updated Indonesian code from SNI 1726:2002 to SNI 1726:2012. Building A in DI Yogyakarta with vertical irregularity on a certain floor is chosen as the object to be studied. There are two types of seismic loads to be simulated, response spectrum and time history analysis. The building is simulated using the numerical program, and four ground motion histories are selected for the dynamic exiting forces. The analysis result shows an increase in the story force either in the response spectrum or the time history. By taking the building's top floor as the reference point, the increase in lateral displacement is also detected in both response spectrum and time history analysis. From the interstory drift ratio examinations, it is also found that there is a weak point located on the setback part that is not identified just by observing the total displacement. This paper compiles the comparison of two versions of the Indonesian seismic code, two types of seismic force, and two points of view in analyzing the building response. Furthermore, the result presented in this paper also beneficial for mitigating the building.

Impact of Roadside Fixed Objects in Traffic Conditions

Highway Capacity Manual (HCM) assumes that traffic flow rates are equally distributed between lanes, which is not always the case. Lane distribution and speed are influenced by lateral clearance on the roadsides. In Jordan, the absence of well-marked lanes and poor lane discipline results in under-utilizing of the freeway capacity. The objective of this study is to look into the impact of the presence of roadside objects on lane distribution and speed. Test sections were selected on six-lane freeway segments located in sub-urban areas on tangent highway segments. Speed measurements and distribution counts made for each lane on a directional three-lane segment of the freeway. The results showed that lane distribution significantly varies depending on lateral clearance and traffic. As lateral displacement increases, right-lane-use and left-lane-use increases while the middle-lane use remains almost at the same level. Average speed increases as the lateral clearance increases. The results also showed that average speed and lane distribution for 1.5m lateral clearances are very similar to no obstacle conditions. The impact of an obstacle is more significant on the right lane while the use of the left lane fluctuates with a significant increase if traffic flow rates reach high levels.

Study on failure mechanism of red clay slope under dry and wet cycles

In order to study the failure characteristics and mechanism of red clay slope under dry-wet cycling conditions, a model slope similar to engineering slope was established. The test slope was monitored by testing elements, and the variation laws of moisture content, temperature, pore water pressure, soil pressure and displacement were analyzed respectively under the alternating conditions of dry-wet cycling. The failure characteristics and mechanism of slope are obtained. With the increase of dry-wet cycles, the overall water content of slope increases, pore water pressure decreases, lateral displacement increases, and vertical displacement remains unchanged to a certain extent. After five dry-wet cycles, the water content of the top and top of the slope is the largest, the water content of the bottom and foot of the slope is the smallest, the horizontal displacement of the slope is the largest, and the horizontal displacement of the top of the slope is the smallest. The range of temperature change increases with the number of dry-wet cycles, and tends to be stable after the third dry-wet cycle. The earth pressure is the largest at the top of the slope, followed by the foot of the slope and the smallest at the slope surface, and the first two dry-wet cycles have the greatest impact on the earth pressure. In the process of dry-wet cycling, the surface cracks of slope undergo the cyclic process of cracking, healing and re-cracking. The width and depth of cracks increase gradually. The surface failure characteristics represented by gully weathering and spalling gradually change into shallow failure characteristics represented by collapse and slump.

Experimental study on damage detection of RC bridge piers under ambient vibration

This paper presents an experimental method for damage detection of bridge piers as the basic and strategic elements in such engineering structures. Definition of percentage and location of damage are considered as initial data to solve damage detection problems. Nowadays, regarding the development of inverse methods for damage detection such as definition of objective functions and optimization approaches, the present experimental study can be utilized as initial stage of such methods. In this study, three 1/3 scaled test specimens of RC bridge piers are casted. Spacing of transverse reinforcements is considered as the main variable parameter for test specimens. The constant vertical loads and low vibrations as cyclic loads are applied to the specimens and the results including the hysteresis behavior of specimens and the backbone curves are investigated. The damage percentage per first four steps is also extracted to utilize the results using Banon-Veneziano method. Also increase in lateral displacement during first steps initiated micro cracks propagated along nearly one tenth of the piers length (0.1L) above the foundation. The cracks were propagated after an increase in displacement from fourth step and were separately observed. Finally, the ultimate failures were observed along nearly one fifth of the piers length (0.2L). Finally, the results revealed that the proposed method is an appropriate method to determine the severity of damage and its location as the primary information in reverse-optimization methods.

Seismic Response Evaluation of Seismically Isolated Nuclear Power Plant Structure Subjected to Gyeong-Ju Earthquake

The Gyeong-Ju earthquake in the magnitude of 5.8 on the Richter scaleoccurred in September 12, 2016. Because there are many nuclear power plants (NPP) near the epicenter of the Gyeong-Ju earthquake, the seismic stability of nuclear power plants is becoming a social problem. In order to evaluate the safety of seismically isolated NPP, the seismic response of a NPP subjected to the Gyeong-Ju earthquake was compared with those of 30 sets of artificial earthquakes corresponding to the nuclear standard design spectrum (NSDS). A 2-node model and a simple beam-stick model were used for the seismic analysis of seismically isolated NPP structures. Using 2-node model, the effect of internal temperature rise, decrease of shear stiffness, increase of lateral displacement and decrease of vertical stiffness according to nonlinear behavior of lead-rubber bearing (LRB) were evaluated. The displacement response, the acceleration response, and the shear force response of the seismically isolated nuclear containment structure were evaluated using the simple beam-stick model. It can be observed that the seismic responses of the isolated nuclear structure subjected to Gyeong-Ju earthquake is significantly less than those to the artificial earthquakes corresponding to NSDS.

Variation of the vertical stiffness of strip-shaped fiber-reinforced elastomeric isolators under lateral loading

A fiber-reinforced elastomeric isolator (FREI) is a relatively new type of isolator that utilizes fiber material for the reinforcing layers. FREIs can be installed in a bonded or unbonded application. In this study, finite element analysis (FEA) is carried out on bonded and unbonded strip-shaped FREIs to investigate the variation in vertical stiffness as the isolator undergoes lateral displacement. The vertical stiffness of the isolators under pure compression obtained by FEA was in good agreement with the predictions of two available closed-form solutions. As the lateral displacement increases, it was observed that for bonded FREIs the vertical stiffness decreases monotonically; whereas, for unbonded FREIs, the vertical stiffness decreased up to 175% shear deformation, where an increase in vertical stiffness was observed. FEA results confirmed that the effective overlap area method provides reasonable estimates for the vertical stiffness of bonded FREIs. It is observed that as the applied vertical stress increases, the vertical stiffness of bonded and unbonded FREIs increases. Finally, the paper shows that under large lateral displacements, bonded FREIs develop large tensile stresses in the regions outside the overlapping areas, while the tensile stresses that develop in unbonded FREIs are very low and confined in a small region.

DESIGN OF DSCT WIND TURBINE TOWER CONSIDERING LARGE DISPLACEMENT EFFECT

A double-skinned composite tubular (DSCT) offshore wind power tower was designed. Because a heavy wind power turbine is supported by a slender tower, the actual resisting moment capacity of the tower against wind load becomes less than its original moment capacity as its lateral displacement increases. Therefore, its actual moment capacity should be found for safe design by considering large displacement effect. In this study, 40 sections of DSCT wind power towers were designed for a 5.0MW turbine and the performances of the designed 40 sections were analyzed with and without considerations of large displacement effect. In designing and analyzing them, the material nonlinearity and the confining effect of concrete considered. The comparison of the analysis results showed the moment capacity loss of the wind power tower by the mass of the turbine is significant and the large displacement effect should be considered for the safe design of the wind power tower.

Undrained vertical bearing capacity of pile located near soft clay slope

The bearing capacity of shallow foundations on slopes is commonly calculated from proposed design charts or using empirical equations. However, there is little information that attempted to analyze the behavior of piles near slopes. This paper presents the results of numerical studies carried out on behavior of pile located near soft clay slopes under undrained vertical loading conditions. A series of three-dimensional numerical models was performed for various pile geometry, different distances of the pile and slope angle. The obtained results show that, as the pile embedded length increases, full formations of wedge failure occurs and, therefore, a greater axial capacity of the pile is mobilized. In addition, by decreasing the distance of the pile from the slope crest the lateral movement of soils increases and the lack of soils on the slope side of the pile tend to reduce the bearing capacity. Furthermore, by increasing the slope angle, the pile lateral displacement increases and, therefore, the eccentricity of the axial load on the pile will produce more additional bending moments in the pile and thereby the axial capacity reduction increases. The results of the analysis are presented in chart form as reduction factors (RF) on horizontal ground ultimate loads.

대변위 효과를 고려한 5MW급 터빈 대응 DSCT 풍력 타워의 구조적 거동 분석

콘크리트 충전 이중강관(DSCT; Double-Skinned Composite Tubular) 해상풍력 타워를 설계하였다. 세장비가 큰 풍력타워는 고중량의 풍력터빈을 지지하므로 안전한 풍력발전 타워의 설계를 위해서는 대변위 효과를 고려하여 실제 횡력에 저항할 수 있는 타워의 모멘트 성능을 계산하는 것이 중요하다. 본 연구에서는 5.0MW 급의 터빈에 대응하는 40개의 DSCT 풍력타워 단면을 설계하고 풍력타워를 대변위 효과를 고려한 경우와 고려하지 않은 경우에 대해 거동을 분석하였다. 설계와 해석에는 모두 재료비선형성과 콘크리트의 구속 효과가 고려되었다. 해석결과의 비교로 터빈 자중에 의한 대변위 효과로 인하여 풍력타워의 실 모멘트 저항 성능 감소분이 상당하며, 안전한 풍력타워의 설계를 위해서는 대변위 효과가 반드시 고려되어야 함을 알 수 있었다. A double-skinned composite tubular (DSCT) offshore wind power tower was designed. Because a wind power turbine is heavy and a wind power tower is very slender, the actual resisting moment capacity of the tower against wind load becomes less than its original moment capacity as its lateral displacement increases. Therefore, its actual moment capacity should be found for safe design by considering large displacement effect. In this study, 40 sections of DSCT wind power towers were designed for a 5.0MW turbine and the performances of the designed 40 sections were analyzed with and without considerations of large displacement effect. In designing and analyzing them, the material nonlinearity and the confining effect of concrete were considered. The comparison of the analysis results showed the moment capacity loss of the wind power tower by the mass of the turbine is significant and the large displacement effect should be considered for the safe design of the wind power tower.

Lateral Force and Lateral Connection Stiffness of Flux Pinned Docking Interface

Another novel flux pinned docking interface consisting of an YBCO high temperature superconductor bulk and two electromagnets is designed in order to improve the connection stiffness of this docking interface and the detailed control strategy of the docking process is introduced. Using this novel docking interface, two spacecraft modules appear with a noncontacting connection status through intervehicle interaction, but with the characteristics of passive stability. The identical current loop model is proposed based on the Ampere current loop hypothesis to treat the magnetic field of the cylindrical permanent magnet that may be installed in the flux pinned docking interface, and the improved image dipole model is adopted with the intention of analyzing the flux pinned lateral force of the novel docking interface theoretically. Additionally, the experiment data of the flux pinned lateral force between a YBCO high temperature superconductor bulk and a cylindrical NdFeB permanent magnet is collected. The theoretical calculation and experimental data both show an initial decrease then increase with the increase of lateral displacement. Moreover, the theoretical analysis compared to the corresponding experimental data indicates that the improved image dipole model is an effective approach. Furthermore, the flux pinned lateral connection stiffness is obtained based on Hooke’s law, showing that this stiffness initially decreases then increases as the lateral displacement that is larger than zero increases.

Fixation Stability Following High Tibial Osteotomy -A Radiostereometric Analysis

Fifteen patients with varus gonarthrosis underwent high tibial osteotomy and internal fixation with an L-shaped rigid plate. In 9 patients, an average wedge size of 7.1 degrees was resected leaving the medial cortex of the proximal tibia intact (group 1). In 6 patients, the medial cortex of the proximal tibia was unintentionally fractured during surgery when an average 10.7 degrees wedge was resected (group 2). Postoperatively, patients were monitored with serial radiostereometric analysis (RSA), conventional radiographs, and clinical evaluation for 1 year. In group 2, RSA revealed a 1.3-mm increase in lateral displacement of the distal tibial segment within 3 weeks following surgery. Twelve weeks after surgery, micromotion between tibial segments was below the precision of the RSA setup in 14 of 15 patients. These findings indicate that in cases with larger wedge sizes (>8 degrees), fracture of the medial cortex of the proximal tibia was frequent and resulted in significant lateral displacement of the distal tibia relative to the tibial plateau. In such cases, prophylactic additional medial fixation rather than lateral L-plate fixation alone is advised to minimize the propensity for lateral displacement of the distal tibia and to avoid subsequent loss of correction.

Stability, bone healing and loss of correction after valgus realignment of the tibial head. A roentgen stereometry analysis

In high tibial closing-wedge osteotomies (HTO), closure of an osteotomy gap after resection of a bony wedge can be associated with a fissure of the medial cortex of the tibial head (MCT). The effect of a broken MCT on the recurrence of varus deformity is disputed. In this study, serial roentgen stereometric analysis (RSA) was used to determine the fixation stability of a rigid internal "L" plate after HTO. Full weight lower limb radiographs were used to determine the sagittal alignment in patients with varying degrees of varus malalignment and correction over time. Forty-two patients with varus gonarthrosis stage I-III (Ahlback) were treated with HTO and internal fixation with an L-shaped rigid plate. Patients were followed by serial RSA, conventional radiographs, and clinical evaluation (Hospital of Special Surgery score) over a 12-month period. In 19 of 42 successive patients, an average wedge size of 6.9 degrees was resected leaving the MCT intact (group 1). In 23 of 42 of patients, the MCT was unintentionally fissured during surgery when an average 10.3 degrees -wedge was resected (group 2). In group 2, RSA revealed a fivefold increase in lateral displacement of the distal tibial segment within 3 weeks after HTO. Twelve weeks after HTO, translations between tibial segments were below the accuracy of the RSA setup in the majority of patients. Group 1 patients demonstrated a higher initial fixation stability, less occurrence of varus deformity, and a higher HSS score compared to patients with larger wedge sizes and frequent fracture of the MCT (group 2). Before bone healing is achieved, the integrity of the MCT plays a crucial role for the clinical and radiological outcome after HTO.