Plane Joint Research Articles

Investigating the Effect of Interface Morphology in Adhesively Bonded Composite Wavy-Lap Joints

Joints and interfaces are one of the key aspects of the design and production of composite structures. This paper investigates the effect of adhesive–adherend interface morphology on the mechanical behavior of wavy-lap joints with the aim to improve the mechanical performance. Intentional deviation from a flat joint plane was introduced in different bond angles (0°, 60°, 90° and 120°) and the joints were subjected to a quasi-static tensile load. Comparisons were made regarding the mechanical behavior of the conventional flat joint and the wavy joints. The visible failure modes that occurred within each of the joint configurations was also highlighted and explained. Load vs. displacement graphs were produced and compared, as well as the failure modes discussed both visually and qualitatively. It was observed that distinct interface morphologies result in variation in the load–displacement curve and damage types. The wavy-lap joints experience a considerably higher displacement due to the additional bending in the joint area, and the initial damage starts occurring at a higher displacement. However, the load level had its maximum value for the single-lap joints. Our findings provide insight for the development of different interface morphology angle variation to optimize the joints behavior, which is widely observed in some biological systems to improve their performance.

Change Detection and Feature Extraction of Debris-Flow Initiation by Rock-Slope Failure Using Point Cloud Processing

Our understanding of debris-flow initiation by slope failure is restricted by the challenge of acquiring accurate geomorphic features of debris flows and the structural setting of the rock mass in the remote mountainous terrain. Point cloud data of debris flows in Sabino Canyon, Tucson, Arizona, July 2006, with initiation by joint-controlled rock slope were obtained using multitemporal LiDAR scanning. Topographic changes were detected by comparing historical LiDAR scanning data of this area since 2005 by adopting open-source CloudCompare software. The results showed persistent scour and erosion in the debris flows after 2006. Point cloud data of joint-controlled rock in the initiation zone were generated by the means of photogrammetry using Pix4D software. The joint planes, the dip direction and the dip value of the joint plane, the joint spacing, and the joint roughness were therefore acquired by point cloud processing. Our study contributes a foundation for analyzing the relationship between the rock features, the generation of slope failure, and the initiation of debris flows.

How Well Do Commonly Used Co-contraction Indices Approximate Lower Limb Joint Stiffness Trends During Gait for Individuals Post-stroke?

Muscle co-contraction generates joint stiffness to improve stability and accuracy during limb movement but at the expense of higher energetic cost. However, quantification of joint stiffness is difficult using either experimental or computational means. In contrast, quantification of muscle co-contraction using an EMG-based Co-Contraction Index (CCI) is easier and may offer an alternative for estimating joint stiffness. This study investigated the feasibility of using two common CCIs to approximate lower limb joint stiffness trends during gait. Calibrated EMG-driven lower extremity musculoskeletal models constructed for two individuals post-stroke were used to generate the quantities required for CCI calculations and model-based estimation of joint stiffness. CCIs were calculated for various combinations of antagonist muscle pairs based on two common CCI formulations: Rudolph et al. (2000) (CCI1) and Falconer and Winter (1985) (CCI2). CCI1 measures antagonist muscle activation relative to not only total activation of agonist plus antagonist muscles but also agonist muscle activation, while CCI2 measures antagonist muscle activation relative to only total muscle activation. We computed the correlation between these two CCIs and model-based estimates of sagittal plane joint stiffness for the hip, knee, and ankle of both legs. Although we observed moderate to strong correlations between some CCI formulations and corresponding joint stiffness, these associations were highly dependent on the methodological choices made for CCI computation. Specifically, we found that: (1) CCI1 was generally more correlated with joint stiffness than was CCI2, (2) CCI calculation using EMG signals with calibrated electromechanical delay generally yielded the best correlations with joint stiffness, and (3) choice of antagonist muscle pairs significantly influenced CCI correlation with joint stiffness. By providing guidance on how methodological choices influence CCI correlation with joint stiffness trends, this study may facilitate a simpler alternate approach for studying joint stiffness during human movement.

Eccentric ankle arthritis in the sagittal plane: a novel description of anterior and posterior ankle arthritis

BackgroundTo report radiographic characteristics of anterior and posterior ankle arthritis, which demonstrates the eccentric narrowing of either aspect of the tibiotalar joint in the sagittal plane. MethodsRadiographic analysis of 19 ankles with anterior arthritis and 16 ankles with posterior arthritis was performed, which were defined as having both (1) eccentric narrowing of the anterior or posterior tibiotalar joint space on lateral radiographs and (2) talar tilt angle less than 4 degrees on anteroposterior radiographs. Measured radiographic parameters were: Talar tilt angle, medial distal tibial angle (MDTA), talar center migration (TCM), anterior distal tibial angle (ADTA), tibial axis-to-talus ratio (TT ratio), talo-first metatarsal (Meary) angle, hindfoot alignment angle (HAA), hindfoot moment arm, and mechanical axis deviation (MAD). An Intergroup comparison analysis, including a normal control group, was also performed. ResultsThe TT ratio was significantly different between each group, indicating a distinct talus position in the sagittal plane. The anterior group had a significantly larger TCM than the control group and lower ADTA compared to other groups, indicating medial translation of the talus and anterior opening of the tibial plafond. The posterior group demonstrated a significantly higher Meary angle and lower HAA compared to other groups and lower MDTA compared to the control group, indicating lower medial longitudinal arch, valgus heel alignment, and varus tibial plafond. The MAD was significantly higher in both the anterior and posterior groups than the control group, indicating varus lower limb alignment. ConclusionAnterior ankle arthritis demonstrated anteromedial translation of the talus and anterior opening of the tibial plafond. Posterior ankle arthritis was associated with the lower medial longitudinal arch and hindfoot valgus, indicating an association with flatfoot deformity. Both anterior and posterior ankle arthritis were associated with varus lower limb alignment.

Seismic behavior and strength of L-shaped steel reinforced concrete column-concrete beam planar and spatial joints

The study presented experimental and numerical investigation on the seismic performance of steel reinforced concrete (SRC) L-shaped column- reinforced concrete (RC) beam joints. Various parameters described as steel configuration form, axial compressive ratio, loading angle, and the existence of slab were examined through 4 planar joints and 7 spatial joints. The characteristics of the load-displacement response included the bearing capacity, ductility, story drift ratio, energy-dissipating capacity, and stiffness degradation were analyzed. The results showed that shear failure and flexural failure in the beam tip were observed for planar joints and spatial joint, respectively. And RC joint with slab failed with the plastic hinge in the slab and bottom of the beam. The results indicated that hysteretic curves of spatial joints with solid-web steel were plumper than those with hollow-web specimens. The capacity of planar joints was higher than that of space joints, while the opposite was true for energy-dissipation capacity and ductility. The high compression ratio contributed to the increase in capacity and initial stiffness of the joint. The elastic and elastic-plastic story deformation capacity of L-shaped column frame joints satisfied the code requirement. A design formula of joint shear resistance based on the superposition theory and equilibrium plasticity truss model was proposed for engineering application.

Numerical Investigation on the Hydraulic Fracture Evolution of Jointed Shale

Joints are a common structure of heterogeneous shale rock masses, and in situ stress is the environment in which heterogeneous rock masses can be found. The existence of joint plane and confining pressure difference influences the physical properties of shale and propagation of fractures. In this study, jointed shale specimens were simulated under different confining pressures to explore the failure patterns and fracture propagation behavior of hydraulic fracturing. Different from the common research of hydraulic fracturing on signal parallel joint rock mass, the simulations in this study considered three points (parallel joint, multi‐dip angle joint, and no‐joint points). The effects of the single‐dip angle joint, multi‐dip angle joint, and confining pressure difference on the hydraulic fracture evolution and stress evolution of the jointed shale were studied comprehensively. The confining pressure difference coefficient proposed in this study was used to accurately describe the confining pressure difference. Results indicate that the larger is the confining pressure difference, the stronger is the control of the maximum principal stress on fracture evolution; by contrast, the smaller is the confining pressure difference, the stronger is the control of the joint plane on fracture evolution. Under the same confining pressure difference, the hydraulic fracture propagates more easily along the small dip angle joint plane. As the value of the confining pressure difference coefficient moves closer to zero, the hydraulic fracture propagates randomly, the tensile stress region around the fracture tip widens, and the joint planes fractured by tensile increase. This study can offer valuable guidance to the design of unconventional reservoir reconstruction.

Joint loads and muscle force distribution during classical and jazz pirouettes

The objective of this study was to analyze the muscle force distribution and lower limb joint loading during two types of pirouettes and check which muscle in which pirouette generates the highest force and which joint is the most loaded. Skilled dancers (n = 16) performed single-turn pirouettes in jazz and classic styles. Kinematic and kinetic data were collected using the Vicon system and Kistler plates. The joint reaction forces and muscle forces were calculated using a musculoskeletal model in the AnyBody Modeling System. No statistically significant differences were found for the duration of the turn in both pirouettes. The range of motion in all joints of supporting leg in sagittal plane and in hip joint in frontal plane for non-supporting leg were significantly higher in classic pirouette. The ankle joint was the most loaded joint in both pirouettes and its maximal value was significantly higher in classic pirouette. The force generated by ankle plantar flexors muscles was significantly greater in the jazz pirouette in turn phase. For the nonsupport limb, external hip rotators generated significantly greater force when performing the classic pirouette. It seems that early stage dancers may start their lessons with jazz pirouettes, where necessary joint mobility is lesser. They also are supposed to increase muscle strength and body awareness with such proceedings. A better awareness of the mechanical loads on the musculoskeletal system which a dancer performing pirouettes faces should have an impact on the way dance classes are conducted and choreographic elements are sequenced.

A Robust Hybrid Position/Force Control Considering Motor Torque Saturation

This paper proposes a robust hybrid position/force control (HPFC) system for multi-degree of freedom manipulators (MDoFMs) with torque constraints on each joint. General HPFC systems can control the interactive contact forces and positions of manipulators in various environments. In HPFC systems, to improve the control performance for MDoFMs, motor torque saturation should be considered. Thus, a robust HPFC system that considers torque constraints by predictive functional control (PFC) is proposed in this paper. The proposed method simultaneously handles the response characteristics and torque constraints of actuators by using PFC as joint space position controllers. Additionally, the robustness of actuators against external forces is enhanced, and the model parameter errors are compensated by the disturbance observer technique. Moreover, implicit force control law and inverse kinematics are introduced for the workspace position/force control to implement the joint space position controllers. Consequently, the stability and robustness of the actuators are considered, and suitable position/force control can be performed even if the torque is saturated. The validity of the proposed method is tested with three planar manipulator joints with a uniaxial force sensor.

Effects of joint orientation and spacing on the boreability of jointed rock mass using tunnel boring machines

Rock mass boreability plays a key role in the performance of tunnel boring machines (TBMs). The angle and orientation of the plane of joint are two factors which affect the boreability of the jointed rock masses. This paper is aimed at describing the combined effects of joint orientation and spacing on the boreability and presenting a new model and classification system to predict the boreability of the jointed rock masses, focusing on field studies. In this regard, a database of three water conveyance projects including the Queens Tunnel in USA, Kerman Tunnel in Iran, and Maroshi-Ruparel Tunnel in India has been employed. A total fracturing factor (presented by Bruland) has been applied as well. The results showed that the increase in the total fracturing factor will result in higher boreability. A model was developed for predicting the boreability of the jointed rock mass based on the total fracturing factor, and the convergence coefficient of this model was 0.7. The volumetric joint count classification system was also developed to analyze the relationship between the total fracturing factor and the volumetric joint count. In order to predict the boreability of the jointed rock mass in the Zagros Tunnel in Iran, the boreability was classified in three categories. The result showed a good agreement between the predicted and actual boreability of the jointed rock mass.

Study on Double‐Shear Test of Anchor Cable and C‐Shaped Tube

The free section of prestressed anchor cable is a weak part of support. A new supporting structure named Anchor Cable and C‐Shaped Tube, which can bear transverse shear force, solves the problem that rock bolt and anchor cable are prone to shear failure in the free section and also solves the contradiction between high preload and low shear bearing capacity of support materials. Double‐shear tests of Anchor Cable and C‐Shaped Tube with smooth joint planes were carried out. Double‐shear tests were carried out on the anchor cables with the diameter of 21.6 mm and the same type of Anchor Cable and C‐Shaped Tube under different preload conditions. The influence of the preload on the shear performance of supporting materials and the enhancement effect of Anchor Cable and C‐Shaped Tube supporting structure on the shear performance of anchor cables were analyzed. The test results confirm that Anchor Cable and C‐Shaped Tube can improve the transverse shear resistance of the supporting material and increase the axial ultimate bearing capacity of the anchor cable during the shearing process. It is found that, during the double‐shear test, the fracture form of the supporting materials is tensile fracture, and when it is sheared, Anchor Cable and C‐Shaped Tube can reduce the stress concentration of the interaction between the joint surface and the surrounding rock and reduce the damage to the surrounding rock.

Biomechanical characteristics of walking and running in children aged 3-6 years

Objective: Biomechanical methods were used to explore the influence of age and gender on children’s motor characteristics, and the internal muscle strength were calculated through simulation modeling, so as to provide ideas for the screening of children with diseases and promotion of motor development. Method: BTS motion capture system collects kinematics data; Kistler force platform collects dynamic data, the simulation software(Anybody 5.2)calculates the muscle strength of the lower limb, two-way ANOVA was performed for difference test. Results: gait: SB, SD, SDI and TA muscle strength increased gradually. GMIP muscle strength: 4 years old group is greater than 3-years-old group. SDI and TFL strength: boys’ were greater than girls’. Running: GM muscle strength: boys’ are greater than girls’. PB muscle strength: the 3-year-old group has smallest muscle strength. GMAS muscle strength: the 3-year-old group has the largest muscle strength, boys’ are greater than girls’. Conclusions: (1) Walking: At the striking time, the buffering capacity of ankle is enhanced gradually. At the moment of lifting off the ground, the range of ankle stretching increased gradually, The angular velocity characteristics has a gender difference. The development of hip flexor muscle strength was uneven between boys and girls. The cushioning muscle strength of the ankle was greater in the 5-year-old group.(2) There were gender differences in time parameters of running. The flexion angle of the ankle was larger at the striking time, which was related to different striking patterns. At the time off-the-ground, the 5-year-old group had the largest hip extension angle. Younger children used more frontal plane joint movement and more hip abductor force.

Numerical Study on Anisotropic Influence of Joint Spacing on Mechanical Behavior of Rock Mass Models under Uniaxial Compression

Mechanical properties of rock masses are dominated by the nonlinear response of joints and their arrangement. In this paper, combined influences of joint spacing (s) and joint inclination angle (β) on mechanical behavior of rock mass models with large open joints under uniaxial compression were investigated by PFC modeling. With a large amount of local measurement circles placed along the pre-defined measurement lines (ML), stresses and joint response parameters at different scales (the measurement circles, the MLs and the whole specimen) were defined and calculated. It was found that macroscopic behaviors of the jointed specimens, such as four types of deformation behaviors, four failure modes, strength, deformability modulus and ductility index, are dominated by nonlinear response of the joint system, especially the interaction between the joints and rock bridges. The joints may experience three stages, i.e., starting to close, closed and opening again. On the joint plane, the peak stresses of the rock bridges and those of the joints may not be reached at the same time; i.e., joint strength mobilization happens with the loss of the rock bridges’ resistance. The influence of s on specimen behavior is little for β = 90°, obvious for β = 0° or 30° and significant for β = 45° or 60°, and this can be related to their different microscopic damage mechanisms.

Duty Factor Reflects Lower Limb Kinematics of Running

The aim was to identify the differences in lower limb kinematics used by high (DFhigh) and low (DFlow) duty factor (DF) runners, particularly their sagittal plane (hip, knee, and ankle) joint angles and pelvis and foot segment angles during stance. Fifty-nine runners were divided in two DF groups based on their mean DF measured across a range of speeds. Temporal characteristics and whole-body three-dimensional kinematics of the running step were recorded from treadmill runs at 8, 10, 12, 14, 16, and 18 km/h. Across speeds, DFhigh runners, which limit vertical displacement of the COM and promote forward propulsion, exhibited more lower limb flexion than DFlow during the ground contact time and were rearfoot strikers. On the contrary, DFlow runners used a more extended lower limb than DFhigh due to a stiffer leg and were midfoot and forefoot strikers. Therefore, two different lower limb kinematic mechanisms are involved in running and the one of an individual is reflected by the DF.

Paleostress Analysis of the Northeastern Limb of Pulkhana Anticline /NE Iraq: Implications for Arabian Plate Tectonic Evolution

Pulkhana anticline is located in Tuzhurmatu area, about 50 km SE of Kirkuk city. The study area forms a part of the Zagros Folded Zone which is situated in the unstable shelf of Iraq within the physiographic zone called Foothill Zone (in the middle of Hemrin- Makhul subzone). The north eastern limb of the anticline reaches to 50ᵒ and the dip of the south western limb reaches to 70ᵒ. The core of the structure comprises the rocks of Fat’ha Formation surrounded by rocks of Injana and Mukdadiya Formations, whereas Bai-Hasan Formation forms the slopes of the low hills surrounding the anticline. These Formations range in age from Middle Miocene to Pliocene. More than 761 readings of joint planes were collected from 20 stations within 5 traverses in the study area. The study of joint sets and system was within Injana and Mukhdadiya formations, along traverses with 3-5 stations for each travers track. The results showed the presence of two sets of tension joints (bc, ac) and five sets of shear joints, through defining the maximum stress axis (σ1) and acute angle dividers for these conjugate joints. It was determined that two directions of Paleostress are present in the area, which are NE-SW and NW-SE. The direction of the first major stress (NE-SW) is orthogonal with, or normal to, the fold axis in the study area, which can be considered as a horizontal component which resulted from oblique collision of Arabian and Eurasian Plates. This old compressive stress is the reason behind the formation of the tension joint (ac) and shear joints, where the sets (ac) and system are perpendicular-semi perpendicular to the bedding plane, as they were formed at an early stage of folding. Also, the ) joint was formed in five tectonic stages with different time intervals. Joints formed in different tectonic stages, in the study area, are attributed to oblique collision of Arabian and Eurasian plates and counter clockwise rotation of Arabian plate relative to Eruasian plate.

Enriched numerical procedures for bolt reinforced fully saturated fractured porous media

Stability analysis of underground structures made in fractured porous continua requires knowledge of rock deformation and pore pressure. Often, reinforcements in terms of rock bolts are installed to enhance the stability and hence the interaction between rock mass and bolt shank becomes inevitable. Extended Finite Element Method (XFEM) has been applied to handle the pre-existing joint planes and rock bolts. Porous media is simulated using Biot’s consolidation theory, whereas fluid flow through fracture is achieved via Cubic law. This paper presents a comprehensive numerical formulation of fractured porous rock media with reinforcement and fluid flow. Apart from solving a benchmark problem, stability of a reinforced tunnel in the vicinity of a joint is also presented using the proposed numerical procedure.

Deformability of the masonry subjected to shearing due to vertical displacements

The paper presents the results of tests of masonry specimens subjected to vertical displacement, with limited deformations in a direction parallel to the masonry bed joints (horizontally) and additionally compressed in the direction perpendicular to the bed joints (vertically). Specimens in the form of fragments of masonry walls were made of solid ceramic brick and AAC blocks. Studies have shown that the nature of the relationship between wall deformation angles and shear stresses caused by vertical displacements depends on the values of accompanying compressive stresses normal to the plane of the masonry bed joints. Compressive stresses have a positive effect on the load-bearing capacity and crack resistance of this type of masonry walls and the angles of deformation occurring at the moment of cracking. The dependence of the transverse stiffness modulus on the value of shear stresses is strongly non-linear, but with increasing shear stresses, it stabilises at a certain level independent of the values of compressive stresses associated with shear.

Experimental study on the combined shear and bending behaviour of corbel joints in precast concrete segmental inverted-T caps

Precast construction of caps is adopted to reduce on-site construction time and facilitate installation. A corbel joint (CJ) is proposed as an innovative joint form to improve the mechanical behaviour and construction performance of precast concrete segmental inverted-T caps. To obtain a further understanding of the failure modes and resistance mechanisms of CJs subjected to combined shear and bending, eight cap specimens with different shear-span ratios (1.61, 2.37, and 3.89) and joint types (CJ, monolithic concrete, and straight joints with a single tooth or multiple teeth) were match cast and tested. The experimental results showed that the CJs achieved superior mechanical and deformation performance and higher bearing capacity compared to conventional straight joints. Owing to corbels intercepting cracks, the CJs were not fully opened similar to straight joints at the limit state. Furthermore, the reinforcement in the corbels reached the yield strength, which suggested that the CJs could transfer the shear force between two adjacent segments effectively and reliably. When the shear-span ratios changed from 1.61 to 3.89, the ultimate shear force in the joint plane reduced by 57.9%, while the ultimate bending moment increased by 5.2%. Therefore, the ultimate shear and bending moment of the CJs were correlated.

Slope Stability Analysis along NH 1D from Sonamarg to Kargil, J&K, India: Implications for Landslide Risk Reduction

Abstract The present work attempts to analyze the slope stability of road section along the national highway NH-1D from Sonamarg to Kargil in the erstwhile J&K, India. The rugged and treacherous terrain in this region is prone to frequent slope failures taking heavy toll of life, property and inconveniences to commuters due to disruption of vehicular movement. For slope study analysis twenty facets were chosen for detail based kinematic analysis and Rock Mass Rating (RMR) to identify the causes and types of failure and potential failure directions. The RMR values obtained from the study range from17 to 96, representing very poor to very good rating and the slopes range from completely unstable to completely stable. The kinematic analysis reveals that most joint planes intersect with each other in different directions consequently forming different potential failure modes. The study concludes that the existing slopes require urgent mitigation measures to thwart the failure.

Development of a new empirical fragmentation model using rock mass properties, blasthole parameters, and powder factor

Rock fragmentation as one of the most important blasting results plays an indispensable role in subsequent stages such as secondary breakage, loading, hauling, crushing and grinding, and relevant energy consumption. Since several rock mass properties, blasthole parameters, and powder factor can affect the fragmentation results, development of an accurate model to predict fragment size has long been a complicated subject. In this study, rock mass properties, blasthole parameters, powder factor (q), and fragment size distribution of blasted rock using image analysis technique were determined for several blasting operations in different zones of Sungun open pit copper mine, Rashakan limestone mine, Soufian limestone mine, and Golgohar open pit iron mine. The median fragment size (X50) varied from 10.4 to 32.1 cm, and the predicted X50 by the modified Kuz–Ram models was significantly different from the X50 of the results. Because only a coefficient has been changed from one model to another and the impact of the combination of the parameters on X50 has not yet been well investigated, the impact of individual essential parameters such as blasthole diameter (ϕh), charge per blasthole (Q), rock mass properties, and q on the X50, X80, and uniformity index (n) was originally analyzed to clarify how their combination affects the fragment size of blasted rocks. ϕh and Q had a similar or a parallel effect on the fragmentation results. Two types of relations between X50 with the new combination of Q, q, SANFO, and blastability index (BI) and X50 with the combination of ϕh, q, SANFO, and BI with acceptable correlations were obtained and the correlations also increased when the parameter of joint plane spacing (JPS) was adjusted in the BI system. At the end, a new empirical model was achieved to predict X50 as a function of combination of Q, q, SANFO and adjusted BI with higher correlation (R2 = 0.865), less root mean square error (RMSE = 3.3 cm), and less coefficient of variation (CV = 19.9%) with actual field results.

An investigation of the possibility of estimating the residual shear strength of rough joints using planar small joint in limestone rocks

Determining the residual frictional properties of rock discontinuities in detail is crucial for the design of safe rock structures. In this paper, direct shear experiments were conducted on two types of artificial limestone joint samples (rough standard tensile joints and grinded planar small joints). The primary goal of this study is to compare the shear behavior of the two above-mentioned types of rock joints during the residual state of shear. The result of roughness analysis shows that during the shearing of rough joints, the increase in normal stress resulted from reduction in contact area which is caused by the mismatch between two surfaces in residual state, will lead to the stress concentration, asperity degradation and plastic deformations. Therefore, several CNL direct shear tests under different normal stresses were carried out on planar joint samples having small contact area (10 × 10 mm2) and it was found that when approximately similar normal stress acts on contact areas during residual state, the residual shear strength measured from those ground surfaces show a good accordance with the residual friction of standard rough joint samples.