Rotational Deformity Research Articles

3D CT scan—A valuable adjunct to radiography

Abstract Background: Deformity correction is based on Full-length True Antero-Posterior and Lateral radiographs. However, a 3D computed tomography (CT) Scan provides a more intricate and detailed understanding of the deformities, so as to plan for the correction with utmost precision. Objective: To prove that 3D computed tomography (CT) Scan provides a more intricate and detailed understanding of the deformities. Materials and Methods: A series of 107 cases, studied from 2017, for a period of 5 years, at our institute was done by means of 3D CT scan. Evaluation was done by measuring angles and lines for further deformity correction, especially in the complex rotational deformities; and osteotomies were performed with Ilizarov fixation. 3D printing was done in selected cases. The patient was made to walk in the immediate postoperative period. The Hexapods were tuned as per the calculations made on the SUV software, for gradual correction. Results: The greatest advantage of using 3D CT is a visualization of the minute details. This may alter the number of osteotomies needed. Eventually, this aids in better correction, when compared with a normal X-ray scannogram. Precision of up to 0.001° was achieved with the DICOM images obtained upon doing the 3D CT, in our study. Conclusion: The information on the deformity in sagittal, frontal, and rotational planes is obtained by doing a 3D CT scan, which allows for further precise planning of the correction. And, as a matter of fact, many Orthopedic Surgeons do not attempt deformity correction as they do not have access to proper full-length X-ray scannograms. Our method gives a precise, cheap, and easily available full-length picture of the deformity, with many more advantages.

Rotational Guided Growth: A Preliminary Study of Its Use in Children.

Torsional malalignment of the legs is common in children, and those that do not remodel may benefit from surgical correction. Traditionally, this is corrected with an open osteotomy. Guided growth is the gold standard for minimally invasive angular correction and has been investigated for use in torsional deformities. This study presents our preliminary results of rotationally guided growth in the femur and tibia using a novel technique of peripheral flexible tethers. A total of 8 bones in 5 patients were treated with flexible tethers consisting of separated halves of a hinge plate (Orthopediatrics Pega Medical, Montreal, QC, Canada), which were fixed to the epiphysis and metaphysis at 45° angles to the physis and connected with Fibertape (Arthrex, Naples, FL, USA). The implants are placed medially and laterally in the opposite 45° inclination, determined by the desired direction of rotation. Additionally, the average treatment time was 12 months. All patients corrected the rotational malalignment by clinical evaluation. The average rotational change was 30° in the femurs and 9.5° in the tibias. Further, the average follow-up was 18 months, with no recurrence of the rotational deformity. There was no change in longitudinal growth in the patients who underwent bilateral treatment. Rotational guided growth with flexible tether devices is a novel technique that successfully corrects torsional malalignment without invasive osteotomy surgery.

Rotating Scarf osteotomy in treating hallux valgus combined with the first metatarsal rotation

To explore clinical effect of rotational Scarf osteotomy in treating hallux valgus (HV) with rotation of the first metatarsal bone. From January 2018 to October 2019, 35 patients (40 feet) with HV and rotation deformity of the first metatarsal were treated with rotational Scarf osteotomy, including 5 males and 30 females;aged from 25 to 76 years old with an average of (40.32±5.43) years old. Hallux valgus angle(HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), the first metatarsal length (FML) were observed and compared, American Orthopedic Foot and Ankle Society(AOFAS) of hallux metatarsophalangeal interphalangeal joint score and visual analogue scale (VAS) were used to evaluate functional evaluation. Thirty-five patients(40 feet) were followed up from 12 to 36 months with an average of (14.35±3.62) months. HVA, IMA and DMAA were corrected from (36.32±4.51) °, (14.21±3.22) ° and (28.35±4.32) ° before operation to (14.32±5.71) °, (5.83±3.97) ° and (7.32±2.14) ° after operation respectively (P<0.05). There was no satistical difference in FML before and after operation (P>0.05). AOFAS score and VAS improved from (57.00±4.31) and (6.00±1.21) before operation to (90.31±3.28) and (1.42±0.83) after operation, respectively, and had significant difference(P<0.05);according to AOFAS score, 23 feet got excellent results, 15 feet good and 2 feet fair. Rotational Scarf osteotomy with strong correction and high dimension could effectively correct HV combined with rotation deformity of the first metatarsal bone, improve function of the forefoot, and obtain good clinical results.

Mechanical properties of re-entrant anti-chiral auxetic metamaterial under the in-plane compression

Traditional auxetic metamaterials are characterized by negative Poisson’s ratio but weak stiffness. In this paper, a new auxetic metamaterial, re-entrant star-shape anti-chiral auxetic metamaterial (Re-S-AC), is proposed and the in-plane mechanical properties of the Re-S-AC are investigated by experimental test and numerical analysis. The crushing test of the Re-S-AC fabricated by the selective laser melting (SLM) method is performed to investigate the deformation mechanism and validate the accuracy of the numerical model. Compared with the anti-tetrachiral and re-entrant star-shape, the Re-S-AC simultaneously exhibits concave and rotational deformation under the in-plane compression, and mean compression stress is highest at the same thickness and same mass. In addition, parametric analysis is conducted to comprehensively reveal the influence of geometric characteristics on the mechanical properties of the Re-S-AC. The results found that the node center distance, node diameter and wall thickness have significant effect on the mechanical properties and deformation mode of the Re-S-AC. Compared with other parameters, wall thickness has the greater effect on the mechanical properties. When wall thickness is from 0.4 mm to 0.8 mm, the Young’s modulus, yield strength, and mean compression stress increase by 447.27%, 530.62%, and 370.87%, respectively. This study provides a reference method for improving the mechanical properties of the auxetic metamaterial.

The Salford technique of correction of rotational malalignment in lower limbs

Derotational osteotomies of lower limb are widely used to correct rotational deformity and the ability to translate pre-operative plan to accurate intra-operative correction remains challenging in these situations. Salford technique uses pre-operative CT scan, limb length radiographs and PACS tools to calculate a correction distance that can be marked on the surface of bone at the osteotomy site intra-operatively to obtain accurate correction. The calculation is based on the two dimensional geometrical formulae of a circle. We present this case report of a patient who underwent derotational osteotomies of femur and ipsilateral tibia along with Medial patellofemoral ligament reconstruction using this technique. Salford technique is simple, reproducible and cost effective in allowing surgeons to accurately correct rotational deformity of lower limbs without the need for specialist equipment.

Interobserver reliability of biplanar radiography is unaffected by clinical factors relevant to individuals at risk of pathological lower limb torsion

BackgroundAssessments of lower limb torsion are ubiquitous in clinical gait analysis practice as pathologic lower limb rotational deformity may contribute to gait abnormalities, anterior knee pain, as well as other debilitating conditions. Understandably, the overall utility of any torsional assessment is dependent on the measurement method’s intrinsic accuracy, precision, and robustness to clinical interference factors. Recently, biplanar radiography (BPR) measurements of torsion have been shown to be both accurate and precise, but the robustness of BPR to potential interference factors is unknown. Research questionHow robust are BPR lower limb torsional assessments to six potential interference factors: amount of torsion, skeletal maturity, radiograph quality, prior osteotomy, presence of implants, and observer training background and experience? MethodsIn this retrospective cohort study, four observers of diverse backgrounds and experience generated digital 3D reconstructions of 44 lower limbs using BPR images obtained during standard of care visits (age range 7–35 years). From each reconstruction, four lower limb torsional parameters were computed: femoral torsion, femorotibial rotation, tibial torsion, and transmalleolar axis equivalent. The mean absolute deviation (MAD) of each torsional parameter – calculated across the four observers – was used as the measure of reliability and tested against all interference factors. ResultsResults demonstrated that the average MAD was 2.1 degrees for femoral torsion, 3.0 degrees for transmalleolar axis equivalent, 3.8 degrees for femorotibial rotation, and 4.7 degrees for tibial torsion. None of the six potential interference factors were found to systematically influence BPR reliability across all four torsional parameters. Of the factors found to statistically influence one or more torsional parameter, none affected MAD values to a clinically meaningful extent. SignificanceIn addition to being accurate and precise, BPR appears to be robust to several clinical factors relevant to children and young adults with or at risk for pathological lower limb torsion.

Upper Extremity Skeletal Muscle Mass Asymmetry Exacerbated by Shoulder Imbalance in Lenke1A Adolescent Idiopathic Scoliosis

Limb muscle strength asymmetry affects many physical abilities. The present study (1) quantified limb muscle asymmetry in patients with adolescent idiopathic scoliosis (AIS); (2) compared AIS patients with major thoracolumbar/lumbar (TL/L) or major thoracic (MT) curves; (3) examined correlations between limb muscle asymmetry and radiographic parameters. Patients with AIS with major TL/L curves (Lenke type 5C) and MT curves (Lenke Type 1A) who underwent posterior spinal fusion at our university hospitals were included. Patients with left hand dominance were excluded. Body composition was measured using whole-body dual-energy X-ray absorptiometry and asymmetry of left and right side skeletal muscles were evaluated. Upper extremity skeletal muscles on the dominant side were significantly larger than those on the nondominant side in both Lenke1A and 5C groups. The asymmetry of upper extremity skeletal muscles was significantly greater in the Lenke1A group than in the Lenke5C group. Additionally, the size of the asymmetry did not correlate with the magnitude of the major curve and rotational deformation but did correlate with a right shoulder imbalance in the Lenke1A group. These results suggest that in AIS with a constructive thoracic curve, right shoulder imbalance is an independent risk factor for upper extremity skeletal muscle asymmetry.

Tibia Multiplanar Deformities and Growth Disturbance Following Expandable Endoprosthetic Distal Femur Replacement.

Expandable distal femur endoprosthesis (EDFE) is commonly used to compensate for the loss of the distal femoral epiphyseal plate in skeletally immature children who have undergone surgical resection of bone malignancies. However, the effect of the passive tibial component of the EDFE on tibial growth has not been extensively studied in the literature. This study aims to delineate the type, frequency, and associated risk factors of multiplanar proximal tibial deformities in skeletally immature children following the use of the expandable distal femur endoprosthesis (EDFE). Moreover, we plan to detect how these deformities influence the long-term functionality of the endoprosthesis in defining the need for subsequent implant revision or further surgical management. A total of 20 patients aged (7-12) years underwent expandable distal femur replacement. Two types of implants were used: Juvenile Tumor System (JTS) non-invasive prosthesis in 14 patients, and Modular Universal Tumor and Revision System (MUTARS)® Xpand Growing Prostheses in six patients. A scanogram and CT scan documented the measurements of longitudinal and multiplanar growth as leg length discrepancy (LLD), femur length discrepancy (FLD), tibia length discrepancy (TLD), and the yield values of rotational, sagittal, and coronal deformities of the tibia. The patients were followed up to assess the need for further management. Sex, age, size of tibial plate perforation, and type of implant used were studied for possible correlation with deformities or growth disturbance. The patients were followed up for a mean of 3 (2-7) years. A total of 14 patients, (10 JTS, 4 implant cast) had a tibial deformity and/or growth disturbance. A single patient was found to have all deformities (growth, rotational, coronal, and sagittal). Fourteen patients were found to have an LLD ranging from 5.3 to 59 mm (median 21 mm), 12 had a TLD from 3 to 30 mm, (median 10 mm), and 11 patients showed evidence of malrotation from 6 to 32 degrees (median 11 degrees). TLD was found to contribute entirely to LLD in three patients, and &gt;50% of LLDs in seven patients. All LLDs were treated conservatively, except in three patients; two received contralateral tibia epiphysiodesis and one received revision with a new implant. A single patient had a posterior tibia slope angle (PTSA) of -2.8 degrees, and three patients had a coronal deformity with a mean medial proximal tibia angle (MPTA) of 80.3 (77-83 degrees). Tibial growth disturbance and multiplanar deformities occur in the majority of patients following EDFE replacement, exacerbating LLD. Yet, these disturbances may be well tolerated, managed conservatively, and rarely mandate endoprosthetic revision or subsequent corrective surgery. Age at the time of surgery was found to be the only significant contributor to the development of tibia growth disturbance.

A numerical modelling of rotating substellar objects up to mass-shedding limits

ABSTRACT Rotation may affect the occurrence of sustainable hydrogen burning in very low-mass stellar objects by the introduction of centrifugal force to the hydrostatic balance as well as by the appearance of rotational break-up of the objects (mass-shedding limit) for rapidly rotating cases. We numerically construct the models of rotating very low-mass stellar objects that may or may not experience sustained nuclear reaction (hydrogen-burning) as their energy source. The rotation is not limited to being slow so the effect of the rotational deformation of them is not infinitesimally small. Critical curves of sustainable hydrogen burning in the parameter space of mass versus central degeneracy, on which the nuclear energy generation balances the surface luminosity, are obtained for different values of angular momentum. It is shown that if the angular momentum exceeds the threshold $J_0=8.85\times 10^{48}\, {\rm erg}~{\rm s}$ the critical curve is broken up into two branches with lower and higher degeneracy because of the mass-shedding limit. Based on the results, we model mechano-thermal evolutions of substellar objects, in which cooling, as well as mass/angular momentum reductions, are followed for two simplified cases. The case with such external braking mechanisms as magnetized wind or magnetic braking is mainly controlled by the spin-down time-scale. The other case with no external braking leads to the mass-shedding limit after gravitational contraction. Thereafter the object sheds its mass to form a ring or a disc surrounding it and shrinks.

Patellar Instability.

Certain anatomic factors, such as patella alta, increased tibial tubercle-trochlear groove distance, rotational deformity, and trochlear dysplasia, are associated with an increased risk of recurrent patellar instability. The presence of a preoperative J-sign is predictive of recurrent instability after operative management. Isolated medial patellofemoral ligament reconstruction may be considered on an individualized basis, considering whether the patient has anatomic abnormalities such as valgus malalignment, trochlear dysplasia, or patella alta in addition to the patient activity level. More complex operative management (bony or cartilaginous procedures) should be considered in patients with recurrent instability, malalignment, and certain anatomic factors.

BIOLOGICAL PLATING OSTEOSYNTHESIS IN COMMINUTED SUBTROCHANTERIC FRACTURES WITH DYNAMIC HIP SCREW

Background: Comminuted subtrochanteric fractures represent a challenge for trauma surgeons. Fractures in the subtrochanteric region present challenges to achieving stable fixation and appropriate reduction because the subtrochanteric region of the femur is one of the highest stressed zones in the human skeleton where tensile or compressive stresses can exceed several multiples of body weight. Aim: The aim of this study is to observe the results of biological DHS fixation in the management of comminuted subtrochanteric fractures of femur in adults. Method: A prospective study was conducted on a group of 25 patients in the Postgraduate Department of Orthopaedics, Government Medical College, Srinagar. In all the patients along with personal data, mode of trauma, type of fracture, intra-operative &amp; post-operative complications, follow up examination including hip joint examination, duration of full weight bearing was considered. Patients were assessed clinically for pain, hip and knee range of motion, angular and rotational deformities and leg-length discrepancy. Union was assessed radiographically. Results: Majority of the patients had trauma due to RTA (76%), fall from height/stairs/standing position (20%), and direct impact (4%). There were 5 type 3A, 6 type 3B, 8 type 4 and 6 type 5 fractures according to Seinsheimer classification. According to criteria laid by Trauma hip rating scale, excellent results were achieved in 16 patients, good in 8 patients and poor in 1 patient. However, no case of failure was reported. Union occurred in all cases. None of the patients had clinical pain or dysfunction. Conclusion: Biological DHS is an effective and reliable option in the treatment of comminuted subtrochanteric fractures as, DHS allows good fixation of a fracture that extends into piriformis fossa (type 5). This procedure offers the significant advantage of being less technically demanding, simple and familiar to most surgeons and Leads to less blood loss.

Fractal Analysis for Wave Propagation in Combustion–Explosion Fracturing Shale Reservoir

The in-situ combustion–explosion fracturing technology in shale reservoirs can promote continuous fracture expansion with a radial detonation wave first converging into a shock wave and then decaying into an elastic wave. The transformation scale of the shale reservoir is determined by the range of wave propagation during combustion–explosion. As wave propagation paths are usually tortuous and fractal, the previous integer wave models are not competent to describe the wave propagation and estimate the impact range of the combustion–explosion fracturing process. This study develops two fractional wave propagation models and seeks analytical solutions. Firstly, a novel fractional wave model of rotation angle is proposed to describe the process of detonation waves converting into shock waves in a bifurcated structure. The radial displacement gradient of the detonation wave is represented by the internal expansion and rotation deformation of the shale. Secondly, another fractional wave propagation model of radial displacement is proposed to show the process of a shock wave decaying into an elastic wave. Thirdly, the proposed models are analytically solved through the fractional variable separation method and variational iteration method, respectively. Analytical solutions for rotation angle and radial displacement with fractal time and space are obtained. Finally, the impacts of the branching parameter of the detonation wave converge bifurcation system, aggregation order of detonation compression wave, and different types of explosives on the rotation angle of the shock wave are investigated. The propagation mechanism of the primary wave (P-wave) with time and space is analyzed. The analytical solutions can well describe the wave propagation process in fractured shales. The proposed fractional wave propagation models can promote the research of wave propagation in the combustion–explosion fracturing process of shale reservoirs.

Ice fabrics in two-dimensional flows: beyond pure and simple shear

Abstract. Ice fabrics – the distribution of crystal orientations in a polycrystal – are key for understanding and predicting ice flow dynamics. Despite their importance, the characteristics and evolution of fabrics produced outside of the deformation regimes of pure and simple shear flow has largely been neglected, yet they are a common occurrence within ice sheets. Here, we use a recently developed numerical model (SpecCAF) to classify all fabrics produced over a continuous spectrum of incompressible two-dimensional deformation regimes and temperatures. The model has been shown to accurately predict ice fabrics produced in experiments, where the ice has been deformed in either uniaxial compression or simple shear. Here we use the model to reveal fabrics produced in regimes intermediate to pure and simple shear, as well as those that are more rotational than simple shear. We find that intermediate deformation regimes between pure and simple shear result in a smooth transition between a fabric characterised by a girdle and a secondary cluster pattern. Highly rotational deformation regimes are revealed to produce a weak girdle fabric. Furthermore, we provide regime diagrams to help constrain deformation conditions of measured ice fabrics. We also obtain predictions for the strain scales over which fabric evolution takes place at any given temperature. The use of our model in large-scale ice flow models and for interpreting fabrics observed in ice cores and seismic anisotropy provides new tools supporting the community in predicting and interpreting ice flow in a changing climate.

The Spatio-Temporal Evolution of Overlying Rock Structure and Mine Pressure Behavior in a Short-Distance Coal Seam Face

This research is aimed at exploring the evolution of overlying strata structure and the ground pressure in the working face mining of close-distance coal seams. By taking the Xiashijie Coal Mine as an example, the direct relationship between the rotation angle of key blocks of overlying strata and the subsidence of key blocks and the length of rock blocks was deduced using theoretical analysis and similar simulation experiments, and the critical criterion of basic overlying strata breaking was formed. Through the real-time monitoring of the characteristics of overlying strata and its pressure, the evolution of overlying strata structure and the ground pressure in the working face mining of close-distance coal seams could be clarified. The results show that the main factors that affect the turning angle of key blocks are the subsidence of key blocks and the length of rock blocks. When the subsidence and turning angle of rock blocks are larger and the length is smaller, the rock blocks are prone to rotational deformation and instability. The lower coal mining of the nearby coal seam group is more difficult due to the overlying strata caving in upper coal mining, and the damage height is about 335 mm higher than that in the upper coal. When mining over the same distance between the upper and lower coal seams of the close-distance coal seam group, fewer weightings are generated when mining the lower coal seam working face, the average weighting step is longer, and the average single weighting value is high. The research results provide a basis for the safe mining of close coal seams.

Nonoperative Versus Operative Treatment of Type IIA Supracondylar Humerus Fractures: A Prospective Evaluation of 99 Patients.

Although current clinical practice guidelines from the American Academy of Orthopaedic Surgeons suggest that Type II and III supracondylar humerus (SCH) fractures be treated by closed reduction and pin fixation, controversy remains as to whether type IIa fractures with no rotation or angular deformity require surgery. The purpose of our study was to prospectively compare radiographic and functional outcomes of type IIa SCH fractures treated with or without surgery. Between 2017 and 2019, 105 patients between 2 and 12 years of age presenting with type IIa SCH fractures and without prior elbow trauma, neuromuscular or metabolic conditions, were prospectively enrolled. Ten orthopaedic surgeons managed the patients with 5 preferring surgical treatment and 5 preferring an initial attempt at nonoperative treatment. Patients in the nonoperative cohort were managed with a long-arm cast and close radiographic follow-up. Patients underwent a standardized protocol, including 3 to 4 weeks of casting, bilateral radiographic follow-up 6 months postinjury, and telephone follow-up at 6, 12, and 24 months. Ninety-nine patients met the inclusion criteria (45 nonoperative and 54 operatives). Of the nonoperative patients, 4 (9%) were converted to surgery up to their first clinical follow-up. No differences were identified between the cohorts with respect to demographic data, but patients undergoing surgery had on average 6 degrees more posterior angulation at the fracture site preoperatively (P<0.05). At the final clinical follow-up (mean=6mo), the nonoperative group had more radiographic extension (176.9 vs 174.4 degrees, P=0.04) as measured by the hourglass angle, but no other clinical or radiographic differences were appreciated. Complications were similar between the nonoperative and operative groups: refracture (4.4 vs 5.6%), avascular necrosis (2.2 vs 1.9%) and infection (0 vs 1.9%) (P>0.05). Patient-reported outcomes at a mean of 24 months showed no differences between groups. Contrary to American Academy of Orthopaedic Surgeons guidelines, about 90% of patients with type IIa supracondylar fractures can be treated nonoperatively and will achieve good radiographic and functional outcomes with mild residual deformity improving over time. Patients treated nonoperatively must be monitored closely to assess for early loss of reduction and the need for surgical intervention.

A Cadaveric Study Verifying the Potential of a Rotational Biplanar Chevron Osteotomy to Correct the 3-Dimensional Hallux Valgus Deformity.

Metatarsal pronation is present in 87% of patients with hallux valgus (HV) deformity. The chevron osteotomy is commonly used worldwide to correct mild to moderate HV deformities. Many modifications have been described, but few address the rotational deformity of the first metatarsal. The rotational biplanar chevron osteotomy (RBCO), described by M. Prado et al, presents a variation of a biplanar chevron osteotomy that can be used to address first metatarsal rotation. The objective of this study is to investigate and verify the technique of the RBCO. We conducted our study performing an RBCO on 9 cadaveric limbs. The technique uses a medial-based wedge parallel to the plantar limb of the osteotomy to make the distal fragment free to correct rotation. A goniometer was used by 2 individual surgeons to control the rotational correction achieved. The osteotomy was considered simple to perform and we experienced no complications, such as fractures or instability. The result was satisfactory alignment and adequate stability. On average, a 2 mm wedge resulted in 11° of rotational correction. We predict that RBCO can safely be used for correcting the metatarsal rotation when necessary in mild to moderate HV deformity foot. Level IV.

Weakened section detailing for scoured/elevated pile groups in sands toward post-earthquake resilient behavior: Quasi-static tests

Scoured or elevated pile-group foundations in coastal regions may experience noticeable residual deformation after strong earthquakes, leading to the loss of functionality and even collapse of the supported structures. To address this problem, a weakened section detailing, which is characterized by a large cover-thickness across a pile-length beneath the cap, is proposed to release constraints on the pile/pile-cap interface, and thereby reduce the residual deformation and meanwhile mitigate underground pile damage. To demonstrate the effectiveness of this section detailing, a pair of quasi-static tests were designed and conducted on two scaled specimens representing scoured pile-group foundations, one with the weakened section detailing and the other with the conventional one, under laterally cyclic loads that mimic horizontal earthquake loading. Test results are interpreted in terms of (1) structural failure mechanisms including damage modes and ductility capacity, and (2) post-earthquake resilient behavior reflected by residual deformation. Compared with the conventional one, the results well demonstrate the feasibility of the weakened section in reducing residual cap deformation (by as large as 34% and 80% for the translational and rotational deformation, respectively, at the ultimate state), mitigating underground damage, and improving ductility capacity under earthquake conditions, while almost maintaining the compression, shear and bending capacities under normal operational conditions. The test results also indicate a need to enhance the seismic shear capacity of the weakened section.

Contribution of tension–torsion coupling effect on elastic properties of chiral and anti-chiral structures

Tension-induced rotation and rotation-induced tension are two types of tension–torsion coupling (TTC). The rotation deformation along with TTC effect is a major factor that can induce the planar porous structure to exhibit the auxetic behavior, but why do some structures have numerous rotations but do not exhibit the auxetic behavior? In this study, we propose an analytical framework to address this issue by quantitatively analyzing the independent effects of direct bending of ligaments and rotation of rigid rings on the mechanical properties of the chiral and antichiral honeycombs. The chirality and the angle between force and ligament mainly affect rotation of rigid rings and direct bending of ligaments, respectively. The analytical expressions of TTC coefficients, Poisson’s ratio and Young’s modulus of antichiral-4, antichiral-3 and chiral-3 honeycombs are derived. The effects of the eccentric distance, the rotation stiffness, the tension and bending stiffness of ligaments on the TTC coefficients, Poisson’s ratio and Young’s modulus are revealed via analytical expressions and numerical results. This work provides a guideline for tailoring Young’s modulus and Poisson’s ratio by tuning the TTC effect to alter the relative strength of direct and rotation-induced deformations in the porous structures from a theoretical point of view.

A force-resisting rotary friction damper (RFD): Verification and comparison with traditional RFD

A force-resisting rotary friction damper (RFD) is proposed in this paper, which can be applied where there is a large rotational deformation. Its exclusive configuration lies in that multiple bolts are symmetrically arranged on concentric circles centered on the hinge pin to apply preload, resulting in: [i] an independent force-transfer capability decoupled with the moment to meet shear or axial forces-transfer demands and [ii] providing larger friction bending-moment with smaller compressive stresses on friction shim and lower maximum stress on the steel plate compared to the traditional RFD under the same preload and friction coefficient. A prototype of the proposed RFD was manufactured and tested twice without tightening the bolts again and replacing the friction shims by cyclic loading to investigate its mechanical property and recoverability. The test results showed that the moment–angle hysteretic curve of the proposed RFD was an ideal rectangle, indicating a reasonable mechanism. The variation of the friction bending-moment was within 4.00 % between the two-time tests, indicating that the proposed RFD has satisfactory recoverability and can uninterruptedly provide energy absorption during dense aftershocks. Then, a refined finite element model was established and calibrated by the test results. For the numerical prototype studied, the friction bending-moment of the proposed RFD was approximately 35 % larger than that of the traditional RFD while its maximum pressure on friction shim was about 40 % of the corresponding traditional RFD. The difference in the friction moment between the theoretical and numerical results was within 4.50 %. The concept of the force-resisting RFD was justified.

Dynamic characteristics of composite damping sandwich open conical shell

In this work, the dynamic characteristics of composite damping sandwich open conical shells are investigated. Considering the superposition effect of rotational inertia and shear deformation during structural vibration, the expressions of kinetic energy and strain energy of composite damping sandwich open conical shell (CDSOCS) are derived based on the first-order shear deformation theory. The Rayleigh-Ritz method is used to establish the free vibration equations for thin and medium-thickness shells. According to the simply supported boundary conditions, the Navier double series method is used to solve the vibration equation. The theoretical solution is compared with the previous results and ANSYS finite element simulation results, and the rationality and effectiveness of the theoretical calculation model are verified. The influence of the thickness change of the sandwich layer under different laying angles and the position change of the sandwich layer under different thickness-diameter ratios on the dynamic characteristics of the CDSOCS is discussed, which provides a reference for the design of orthotropic composite damping sandwich complex structures.