Research on the spatial effect of foundation pit under asymmetric loads

Introduction The etiology of spinal deformity in idiopathic scoliosis is unclear to date. One of the suspected influences is the asymmetric loading condition involved in the disorder. The aim of this project is to test the hypothesis that asymmetric dynamic loading influences the morphological and biological characteristics of the intervertebral discs in scoliosis. The study is performed with organ cultured discs by using a custom-designed asymmetrical loading device. Material and Methods Bovine caudal discs (6–10 months) were used in current study. For symmetric dynamic loading (Parallel), discs were placed in custom-designed chambers, and compressed by parallel metal plates in a Bose mechanical testing device. For asymmetric dynamic loading (Wedge), a 10° wedge was placed underneath the discs to mimic the load bearing condition of discs in scoliotic patients. The discs were submitted to 2 different load regimes: (1) 1 hour dynamic loading (0.02–0.4 MPa, 1Hz) and 23 hours free swelling culture for 7 days; (2) 1 hour dynamic loading (0.02–0.4 MPa, 1Hz) and 23 hours static loading (0.2 MPa) for 7 days. Disc heights were measured with caliper before and after each loading. After 7 days of culture, gene expression levels of aggrecan (ACAN), type I and II collagen (COL1 and COL2), IL1, IL6, and MMP1 in the annulus fibrosus was analyzed by real-time PCR. Genes that have been found dysregulated in human scoliotic discs compared with healthy controls were also measured in the organ cultured discs, including MMP13, type X collagen (COL10), CXCR4, BMP3, S100A12, and S100A8 ( n = 8). Results Disc height showed a constant drop in load regime 2, while a temporary decrease after 1h dynamic loading followed by free swelling recovery was noted in load regime 1. After 7th dynamic loading, the change in shape was greater in load regime 2 (disc height ratio wedged to non-wedged side of 0.81), than that in load regime 1 (height ratio of 0.87, p < 0.05). Under load regime 2, MMP13 gene expression level increased 6.1-fold in Wedge disc compared with Parallel disc, while gene expression levels of COL10, CXCR4, BMP3, S100A12, and S100A8 were not affected. Gene expression levels of ACAN, COL1 and COL2 under load regime 1 were significantly higher compared with load regime 2. Moreover, discs under load regime 2 showed a trend in higher IL1, IL6, and MMP1 gene expression compared with regime 1. Conclusion Diurnal dynamic loading and free swelling recovery could maintain the gene expression of organ cultured discs at their physiological level. Diurnal dynamic loading followed by static loading mimicked a degenerative condition, as indicated by lower anabolic and higher catabolic gene expression. These results suggest that recovery of disc height and morphology after dynamic load may help to prevent degeneration of discs under constant loading. Asymmetric dynamic and static loading regime induces an increase in MMP13 gene expression compared with symmetric loading, which was also observed in a human scoliosis sample dataset. These results indicate that short-term asymmetric loading may be used to mimic early changes associated with the onset of scoliosis. Acknowledgment This study is supported by AOSpine International.

The purpose of this study was to investigate the effect of different load carriage modes on coordinative patterns in the lower extremities during walking. Twenty-five university students walked on a treadmill at their preferred pace under three different load conditions: symmetric load (5% of body mass in messenger bags on each shoulder hanging vertically and against the hips), asymmetric load 1 (10% of body mass in a messenger bag on one shoulder hanging vertically against the ipsilateral hip), and asymmetric load 2 (10% of body mass in a messenger bag on one shoulder with the bag draped across the trunk to the contralateral hip). Altered thigh-shank and shank-foot couplings were found for the loaded side during the stance of gait when comparing the asymmetric 1 and 2 to the symmetric load. In addition, thigh-thigh coupling was changed during gait when comparing the asymmetric load 2 and symmetric load. However, we did not find any significant differences in intralimb and interlimb couplings between the two different asymmetric load conditions. The results suggest potential benefits when carrying symmetrical loads in order to decrease abnormal limb coordination in daily activities. Thus, it may be advisable to distribute load more symmetrically to avoid abnormal gait.

PurposeTo determine the effects of asymmetric loads on muscle activity with the bench press.MethodSeventeen resistance-trained men performed one familiarization session including testing one repetition maximum (1RM) and three 5 repetition maximum (RM) lifts; using symmetric loads, 5% asymmetric loads, and 10% asymmetric loads. The asymmetric loading (i.e., reduced load on one side) was calculated as 5% and 10% of the subject`s 1RM load. In the experimental session, the three conditions of 5RM were conducted with electromyographic activity from the pectoralis major, triceps brachii, biceps brachii, anterior deltoid, posterior deltoid, and external oblique on both sides of the body.ResultsOn the loaded side, asymmetric loads reduced triceps brachii activation compared to symmetric loads, whereas the other muscles demonstrated similar muscle activity between the three conditions. On the de-loaded side, 10% asymmetry in loading resulted in lower pectoralis major, anterior deltoid, and biceps brachii activation compared to 5% asymmetric and symmetric loading. On the de-loaded side, only pectoralis major demonstrated lower muscle activation than symmetric loads. Furthermore, asymmetric loads increased external oblique activation on both sides compared to symmetric loads.ConclusionsAsymmetric bench press loads reduced chest and shoulder muscle activity on the de-loaded side while maintaining the muscle activity for the loaded side. The authors recommend resistance-trained participants struggling with strength imbalances between sides, or activities require asymmetric force generation (i.e., alpine skiing or martial arts), to implement asymmetric training as a supplement to the traditional resistance training.

In practical engineering, natural soil deposits often sustain an initial driving force prior to cyclic shear, owing to earthquakes, traffic and waves; such asymmetrical loading conditions may significantly affect the liquefaction susceptibility and failure mechanism of sand. To understand the typical cyclic liquefaction responses, comprehensive asymmetrical cyclic loading tests were conducted on sand samples subjected to either compressional or extensional static stress. The results indicated that different stress conditions can result in three distinct failure mechanisms: flow liquefaction, cyclic mobility and residual deformation accumulation. According to the experimental observations, an anisotropic sand model was developed within the framework of the anisotropic critical state theory. The model employed a fabric-dependent dilatancy, and accounted for the effects of the fabric evolution and accumulated loading index on the plastic hardening, in order to better reflect the cyclic degradation of the plastic modulus. The predictive capacity of the model was confirmed through undrained monotonic test results for samples with different densities. Comparisons between the model responses and experimental results indicated the excellent capabilities of the developed model in terms of capturing the typical deformation, strength and fabric characteristics of different cyclic failure mechanisms of sand under either symmetrical or asymmetrical loading conditions.

The thickness of aquifer is relatively large, the aquifer is not completely isolated by the diaphragm wall, and the water flow inside and outside the foundation pit flows at the bottom of the diaphragm wall. This article reports indoor experiments and theoretical methods which are used to study the deformation mechanism and law caused by dewatering in foundation pit under the condition of incomplete isolation of the inner and outer aquifers of the foundation pit based on typical geological conditions in South China. Our findings are as follows. (1) Through the experimental analysis of the mechanism of groundwater seepage around the foundation pit, the effective influence depth of precipitation in the foundation pit is greater than that outside the foundation pit, and the effective influence depth of double well precipitation is greater than that of single well precipitation. It reveals that the precipitation curve outside the foundation pit under the influence of seepage around the foundation pit presents the characteristics, and puts forward the calculation formula of surface settlement change outside the pit caused by partially penetrating well precipitation in the completely decomposed granite stratum. The calculation results of the theoretical formula are in good agreement with the experimental results, which has good accuracy and applicability. (2) The surface settlement outside the pit caused by dewatering in the foundation pit is mainly concentrated in the surrounding seepage area, and the change value of surface settlement outside the pit caused by double well dewatering is 2∼3 times greater than that caused by single well dewatering. When the whole well is vertically reinjected, the maximum surface settlement is 0.009 mm at the side near the diaphragm wall, and 0.005 mm at the side far away from the diaphragm wall. When the whole well is at an inclination of 10°, the maximum surface settlement is 0.002 mm at the side near the diaphragm wall, and 0.008 mm at the side far away from the diaphragm wall. When the whole well is at an inclination of 20°, the maximum surface settlement is −0.005 mm at the side near the diaphragm wall, and 0.011 mm at the side far away from the diaphragm wall. The full well depth recharge with an inclination of 20° has the largest influence on the surface settlement of the foundation pit, and the recharge effect is the best. (3) The lateral displacement of diaphragm wall increases by 24% compared with that without reinjection. The maximum lateral displacement of the diaphragm wall is 0.09% of the precipitation depth when the whole well is tilted at 10° for reinjection, and the lateral displacement of the diaphragm wall increases by 13% compared with that without reinjection. The maximum lateral displacement of the diaphragm wall is 0.082% of the precipitation depth when the whole well is tilted at 20° for reinjection, and the lateral displacement of the diaphragm wall increases by 4.9% compared with that without reinjection. The full well depth recharge with an inclination of 20° has the least impact on the diaphragm wall, and the recharge effect is the best. The above results can be provided as theoretical foundation for the study of the deformation mechanism and law caused by dewatering in foundation pit.

Three-dimensional panels are one of the modern construction systems which can be placed in the category of industrial buildings. There have always been a lot of studies and efforts to identify the behavior of these panels and improve their capacity due to their earthquake resistance and high speed of performance. This study will provide a comparative evaluation of behavior of updated three-dimensional panel\'s structural components under lateral load in both independent and dependent modes. In fact, this study tries to simultaneously evaluate strengthening effect of three-dimensional panels and the effects of system state (independent, L-shaped and BOX shaped Walls) with reinforcement armatures with different angles on the three-dimensional panels. Overall, six independent wall model, L-shaped, roofed L-shaped, BOX-shaped walls with symmetric loading, BOX -shaped wall with asymmetrical loading and roofed BOX-shaped wall were built. Then the models are strengthened without strengthened reinforcement and with strengthened reinforcements with an angle of 30, 45 and 60 degrees. The applied lateral loading, is exerted by changing the location on the end wall. In BOX-shaped wall, in symmetric and asymmetric loading, the load bearing capacity will be increased about 200 and 50% respectively. Now, if strengthened, the load bearing capacity in symmetric and asymmetric loading will be increased 3.5 and 2 times respectively. The effective angle of placement of strengthened reinforcement in the independent wall is 45 and 60 degrees. But in BOX-shaped and L-shaped walls, the use of strengthened reinforcement 45 degrees is recommended.

Objectives: The objective of the study was to determine the optimal use of a new optical device, the RibEye system, intended to obtain internal ribcage deflections from tests using anthropomorphic test dummies. Specifically, the study was designed to determine the most efficacious mounting location of light emitting diodes (LEDs) on the ribs and sternum in the 50th percentile male Hybrid III dummy. Methods: Optical signal drop-out and accuracy assessment tests were conducted. In the former series, symmetric antero-posterior chest compressive loading was accomplished using cylindrical and square indenters, and asymmetrical compressive loading was accomplished using unilateral offset and diagonal belt-type loadings. LEDs were mounted to multiple ribs bilaterally at varying locations on the ribcage. The internal chest potentiometer available in the Hybrid III dummy was used. The latter series, aimed at examining the system accuracy, consisted of tests with LEDs mounted to the 4 corners of the sternum, termed sternum-mounted LED tests; rib-mounted tests wherein LEDs were mounted either to a specific rib or in the intercostal space of two successive ribs; rib-mounted tests with rotated chest simulating oblique loading; and indenter-mounted isolated LED tests. An electro-hydraulic testing device was used to apply compressive loads via an indenter in all tests. Displacement profiles were extracted from the optical system records, drop-out evaluations were conducted, and the system accuracy was evaluated by comparing data from the indenter and/or internal chest potentiometer. Results: In general, results indicated that the RibEye system captures rib cage deformations effectively. Under symmetric loading, LEDs on the sternum responded similar to the internal chest potentiometer. The accuracy of the system depended on the location of position of the LEDs on the rib, magnitude of rib deformation, and potential interference from internal dummy structures such as the presence of the internal chest potentiometer. Optimum locations for LED placement were found to be at a distance of 9 cm, measured along the outer curvilinear path of the rib from the mid-sternum on either side. At this location, the system showed no signal drop-out at deflections representative of the United States current frontal impact Injury Assessment Reference Values. Signal drop-out was also depended on the type of loading: diagonal belt-type loading produced more signal loss. Mounting LEDs away from the center of the rib representing eccentric superior-inferior (z) axis placement also resulted in loss of accuracy. Conclusions: These controlled evaluations provide a fundamental understanding of the performance of the system as installed in the 50th percentile male Hybrid III dummy and its ability to measure both antero-posterior and lateral components of deflections at multiple ribs, including the sternum for frontal impact applications. The system may be optimally used to gather rib deflection data without signal drop-out under symmetrical and asymmetrical loadings when LEDs are mounted on the superior-inferior centerline of the ribs with no eccentricity along the z-axis and at the 9-cm location from the mid-sternum on either side of the ribcage and at any corner on the sternum to obtain sternum deflections.

The school backpack constitutes a daily load for schoolchildren: we set out to analyse the postural effects of this load, considering trunk rotation, shoulder asymmetry, thoracic kyphosis, lumbar lordosis, and sagittal and frontal decompensation from the plumbline. A group of 43 subjects (mean age = 12.5 ± 0.5 years) were considered: average backpack loads and average time spent getting to/from home/school (7 min) had been determined in a previous study conducted on this population. Children were evaluated by means of an optoelectronic device in different conditions corresponding to their usual everyday school backpack activities: without load; bearing 12 (week maximum) and 8 (week average) kg symmetrical loads; bearing an 8 kg asymmetrical load; after fatigue due to backpack carrying (a 7-minute treadmill walking session bearing an 8 kg symmetrical load). Both types of load induce changes in posture: the symmetrical one in the sagittal plane, without statistical significant differences between 8 and 12 kg, and the asymmetrical one in all anatomical planes. Usual fatigue accentuates sagittal effects, but recovery of all parameters (except lumbar lordosis) follows removal of the load. The backpack load effect on schoolchildren posture should be more carefully evaluated in the future, even if we must bear in mind that laws protect workers to carry heavy loads but not children, and results in the literature support the hypothesis that back pain in youngsters is correlated with back pain in adulthood

Ten men and eight women participated in a repeated-measures experiment in which sudden loads were applied unexpectedly to a container held in the hands. Three independent variables were investigated: lifting belt use, preload, and load symmetry. To determine whether a lifting belt would help protect the spine in sudden symmetric and asymmetric loading situations. Unexpected loading events have long been associated with the onset of back pain. Based on work showing that lifting belts restrict motion of the torso, the hypothesis was that a lifting belt would stiffen the spine, thereby protecting its supporting tissues. A weight, equal to 7.5% of the subjects' trunk extension force, was allowed to fall 1 m before the bottom of a box held by blindfolded subjects was pulled. Kinetic and kinematic data, obtained from two force plates and a magnetic motion measurement system, were used in a three-dimensional, dynamic, linked-segment biomechanical model to calculate spine moments. Electromyogram data were simultaneously obtained from eight trunk muscles. The belt reduced the forward bending of the spine during the symmetric loadings. In the men, the belt also reduced the forward flexion moment acting on the spine. The belt restricted lateral bending in the women and men, when the box was preloaded. The peak electromyogram amplitudes from posterior contralateral erector spinae and latissimus dorsi muscles increased during the asymmetric loadings, whereas three ipsilateral muscles were less active. The conflicting moment and electromyographic results, combined with the influence of load symmetry, preload, and gender make the benefits of the lifting belt difficult to delineate. Although the data support the hypothesis that the belt stiffens the torso's response to sudden loading, the effects are small, and considerable individual differences exist. The findings show that during unexpected sudden loading, a belt may reduce the net external moment loading. At the same time the belt appears to alter the muscle response strategy so that the belt's overall effect on an individual's safety is hard to determine.

Suspension structures, known for their excellent properties, have been widely used to cover medium and large spans. Their efficiency lies in their ability to primarily withstand permanent and variable loads through tension. Consequently, suspension roof structures typically adopt a parabolic shape, which remains in equilibrium under symmetric loads. However, when subjected to asymmetric loads, such structures experience significant kinematic displacements. To reduce these displacements, suspension systems with bending stiffness, commonly referred to as “rigid” cables, are employed. Such elements increase the sustainability of the suspension system compared with conventional spiral ropes. Although previous studies have analyzed the behavior of such systems under symmetric loads, this article examines the performance of an innovative cable–strut system composed of straight “rigid” elements under asymmetric loads. The behavior of three different types of suspension structures under asymmetric loads is analyzed. A non-linear analysis of forces and displacements is conducted in this system, assessing the impact of bending stiffness on the structural response. The results indicate that the proposed two-level suspension system performs more effectively under asymmetric loads than both conventional parabolic suspension structures and suspension systems comprising two straight “rigid” elements. It was found that the total forces and stresses in the “rigid” upper chord elements of the two-level system are the lowest among all the systems considered. Therefore, this system is particularly suitable for covering medium- and large-span roofs, especially when subjected to relatively large asymmetric loads.

Interlimb asymmetries may influence contralateral knee osteoarthritis (OA) progression, yet research remains unclear. This study examined whether patient-reported outcomes and knee biomechanics differ between individuals with knee OA exhibiting symmetrical versus asymmetrical knee loading. Forty-three individuals with knee OA were dichotomized into symmetrical (≤14% asymmetry; n = 19) and asymmetrical (>14% asymmetry; n = 24) groups based on total joint moment symmetry indices. Participants completed the Knee Injury and Osteoarthritis Outcome Score and Intermittent and Constant Osteoarthritis Pain questionnaires. Three-dimensional kinematics and kinetics were collected during walking at a self-selected speed. Independent t tests and statistical parametric mapping examined between-group differences in patient-reported outcomes and biomechanical measures. Individuals with symmetrical knee loading had worse Knee Injury and Osteoarthritis Outcome Score activities of daily living scores (P = .041) than those with asymmetrical loading. Individuals with symmetrical knee loading exhibited less knee extension moment during late stance (P = .031) and lower knee adduction moment range in their affected knee compared with asymmetrical loaders. Individuals with symmetrical knee loading walked with lower knee flexion angles (P = .011), less midstance unloading (P = .011), and lower peak knee flexion moment (P < .001) in their contralateral knee compared with asymmetrical loaders. Symmetrical knee loading was associated with affected and contralateral knee biomechanics that were consistent with more severe knee OA and worse functional outcomes.

O71: Skeletal and anthropometric determinants of gait balance in asymptomatic adult subjects

Carrying asymmetric loads during stair negotiation

P36: Relation between navicular mobility and multi-segment foot kinematics during walking

The tensile, creep, fatigue and creep-fatigue tests of the nickel-based superalloy GH4169 were carried out. According to the deformation characteristics of GH4169 alloy, the Ohno-Karim kinematic model (O-K model) can be used to describe the tensile behavior. The creep constitutive model presented in this paper can be used to predict the three-stage creep characteristics of the GH4169 alloy. The modified Ohno-Karim kinematic hardening model, combined with an isotropic hardening model, can well predict the cyclic softening behavior of the material under symmetric loads and the mean stress relaxation behavior under asymmetric loads. Based on the modified Ohno-Karim kinematic hardening model, isotropic hardening model and creep constitutive model, a non-unified constitutive model was established. The creep-fatigue behavior of the GH4169 alloy under symmetric and asymmetric loads is simulated by using the non-unified constitutive model. The simulation results are very close to the experimental results; however, the prediction results of the time-dependent relaxation load are relatively small.