Rotational Rigidity Research Articles

Research on Mechanical Properties of Dingtougong Mortise-Tenon Joints of Chinese Traditional Hall-Style Timber Buildings Built in the Song and Yuan Dynasties

ABSTRACTIn order to study structural properties of Dingtougong mortise-tenon joints of Chinese traditional hall-style timber buildings built in the Song and Yuan dynasties, and to provide theoretical basis for structural analysis and scientific conservation of this type of architectural heritages. First, the main structural characteristics of the Chinese hall-style timber buildings built in the Song and Yuan dynasties were sorted out, including the structural forms, structural dimensions, and configurations of mortise-tenon joints. Then, the low cyclic loading tests of the six reduced-scale mortise-tenon joints were carried out, including the five groups of Dingtougong mortise-tenon joints, and the one reference group of mortise-tenon joint without Dingtougong. The results show that all the five groups of Dingtougong mortise-tenon joints have better structural performance than the one reference group of mortise-tenon joint on the aspects of ultimate capacity and rotational rigidity. In the five groups of Dingtougong mortise-tenon joints, the structural performance of the Dingtougong mortise-tenon joint with Dingtougong of through mortise-tenon joint is obviously superior to that of the Dingtougong mortise-tenon joint with Dingtougong of half mortise-tenon joint. Besides, considering material nonlinearity and contact nonlinearity, the finite element models of the six groups of mortise-tenon joints were built up by ANSYS, and the structural properties of these mortise-tenon joints under in-plane vertical load, out-of-plane horizontal load and torque load were analyzed and compared with the experimental results. The theoretical results very coincide with the experimental results. Under in-plane vertical load, the Dingtougong obviously improves the mechanical performance of the mortise-tenon joint. In addition, the relationships among the initial elastic rotational rigidity KY under in-plane vertical load, the initial elastic rotational rigidity KX under out-of-plane horizontal load, and the initial elastic rotational rigidity KR under torque load of these six groups of mortise-tenon joints were obtained, the results of which can provide theoretical base for structural analysis and conservation design of Chinese traditional hall-style timber buildings.

Rotational Restraint to Purlins Provided by Standing Seam Roof Systems

The finite element model used for analyzing the rotational restraint rigidity of standing seam roof systems was developed. The influences of different factors on the rotational restraint rigidity provided by two types of standing seam roof systems were studied. The variables include local deformation of standing seam roof panels, panel thickness, clip tab thickness, and the relative sliding of clip tab and clip base. The restraint mechanism of standing seam roof systems to the purlins was studied. It is shown that the rotational restraint rigidity provided by the two types of researching standing seam roof systems mainly depends on the slide tab thickness and the roof panel thickness. Finally, formulae for calculating rotational restraint rigidity of the LSIII and SS360 standing seam roof systems were also proposed based on parametric analysis results.

Investigation of the rigidity of welded shear tab connections

Shear tab connections are among the economical connections that are usually designed as a simple connection. The shear tab connection sustains some bending moment as the beam end rotates and therefore it may be classified as semi-rigid connections, based on the geometry of the connection. In this research, the end rotation of steel girders with shear tab connection, which is both welded to the supporting member and to the beam’s web, is investigated. 317 finite element models with different beam sizes and shear tab plates are used to investigate their effect on the connection rigidity and classification, under service loads. The results show that the main source of the connection rotation was the plastic deformations in the shear tab and the plastic modulus of the shear tab section plays an important role in the determination of the welded shear tab connection rotational rigidity. It also concluded that the gap between the beam and the connection face has negligible effect on the rigidity of the connection. Increasing the shear tab height leads to the increase of the shear tab section plastic modulus, which results in the increase of the connection rigidity. In addition, based on the results, a simple equation is introduced to predict the rigidity of the shear tab connections.

RESEARCH FEATURES OF AEROELASTIC OSCILLATIONS OF UNMANNED AERIAL VEHICLES WITH ELECTRIC ACTUATOR OF RUDDERS

Designing a modern flight vehicle is associated with the need to solve many scientific and technical problems. These tasks include the prevention of insecure self-oscillations in flight, taking into account the elasticity of the structure. These problems relate to dynamic aeroelasticity, a science that examines the interaction of an elastic structure (at its oscillation) with an air flow. Maneuverable unmanned aerial vehicles (UAVs) are considered. Since UAVs are essentially not used without an automatic control system (ACS), its presence must be taken into account when considering the vibrations of an elastic structure in flight. The influence of the elasticity of UAV design on the operation of ACS in flight is manifested in the possibility of self-oscillations in the loop "elastic UAV – ACS". Self-oscillations lead to disruption of normal operation of the onboard equipment or its failure. The complexity of the problem requires its consideration at almost all stages of UAV’s development, including the creation of a prototype and testing. The computational and experimental studies of the characteristics of elastic oscillations in the UAV flight of the cross-shaped scheme are considered. The features of these UAVs (options with a modular design, the nonlinearity of the airframe, rudders, ACS, and others) due to a significant amount of testing that is the basis for the calculations. Electric actuators have a small continuous operation time, and resource use, there are gearboxes with a large gear ratio and backlashes. This determines the dependence of the rotation rigidity of the rudders on the amplitude and frequency, as well as a significant increase in the total moments of inertia. The technique of bench experiment with obtaining data to assess the boundaries of the flutter and the boundaries of the stability of the loop "elastic UAV – ACS" is given. The questions of improvement of the stabilization system of UAV required for the study of its stability at frequencies of elastic oscillations are considered, as well as the evaluation of the limiting cycles of self-oscillations is given.

Ceramic motorized spindle for NC machine tool

In order to reduce the inertia force and centrifugal force generated when the spindle bearing unit rotates at a high speed and to increase its limit rotation speed, precision, rigidity, service life and reliability, it can meet the high speed and high precision requirements of the spindle system. The innovative design of the ceramic motorized spindle unit, testing and analysis of the comprehensive performance of ceramic motorized spindle and the related research on the intelligentization of the ceramic motorized spindle were carried out. Finally, the current limitations and challenges are discussed, and the future development trend of the numerically-controlled machine tool ceramic motorized spindle is forecasted.

Biomechanical Analysis of Cortical Versus Pedicle Screw Fixation Stability in TLIF, PLIF, and XLIF Applications

Study Design:Cadaveric biomechanical study.Objectives:Medial-to-lateral trajectory cortical screws are of clinical interest due to the ability to place them through a less disruptive, medialized exposure compared with conventional pedicle screws. In this study, cortical and pedicle screw trajectory stability was investigated in single-level transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF), and extreme lateral interbody fusion (XLIF) constructs.Methods:Eight lumbar spinal units were used for each interbody/screw trajectory combination. The following constructs were tested: TLIF + unilateral facetectomy (UF) + bilateral pedicle screws (BPS), TLIF + UF + bilateral cortical screws (BCS), PLIF + medial facetectomy (MF) + BPS, PLIF + bilateral facetectomy (BF) + BPS, PLIF + MF + BCS, PLIF + BF + BCS, XLIF + BPS, XLIF + BCS, and XLIF + bilateral laminotomy + BCS. Range of motion (ROM) in flexion-extension, lateral bending, and axial rotation was assessed using pure moments.Results:All instrumented constructs were significantly more rigid than intact (P < .05) in all test directions except TLIF + UF + BCS, PLIF + MF + BCS, and PLIF + BF + BCS in axial rotation. In general, XLIF and PLIF + MF constructs were more rigid (lowest ROM) than TLIF + UF and PLIF + BF constructs. In the presence of substantial iatrogenic destabilization (TLIF + UF and PLIF + BF), cortical screw constructs tended to be less rigid (higher ROM) than the same pedicle screw constructs in lateral bending and axial rotation; however, no statistically significant differences were found when comparing pedicle and cortical fixation for the same interbody procedures.Conclusions:Both cortical and pedicle trajectory screw fixation provided stability to the 1-level interbody constructs. Constructs with the least iatrogenic destabilization were most rigid. The more destabilized constructs showed less lateral bending and axial rotation rigidity with cortical screws compared with pedicle screws. Further investigation is warranted to understand the clinical implications of differences between constructs.

Parametric Study of Stiffeners in Steel Composite Tub Girders

Closed structural sections (rectangular, circular, trapezoidal shape) possess high rotational rigidity compared to open sections like I girder. For highly curved bridges, closed sections with high torsional rigidity is an absolute choice. This paper suggests the use of steel – composite Tub girder instead of concrete I girder in rail bridges. Stiffeners were used to strengthen the girder. Deflection and stress study has been done for the entire girder on various thickness of stiffeners under different loading.

Chemistry of 2,4,6-Tri-tert-butylanilides Possessing Isolable Rotational Isomer

Amide C-N bond in 2,6-di-tert-butylanilides has a high rotational barrier and the individual amide rotational isomers can be isolated at ambient temperature. These anilides have been reported by Chupp et al. in 1967, but no systematic study with anilide substrates other than α-haloacetoanilides, or the stereoselective synthesis of anilide rotamers have been reported. In addition, the structural properties of these anilides have not been investigated in detail. We succeeded in the highly selective stereodivergent synthesis of Z- and E-rotamers of various N-allyl-2,4,6-tri-tert-butylanilides through Pd(0) and Pd(II) catalyzed N-allylation of O-allyl-N-(2,4,6-tri-tert-butylphenyl)imidates. Moreover, the relative thermodynamic stabilities of the obtained anilide rotamers were clarified. Specific reactivity of 2,4,6-tri-tert-butylanilide derivatives was also found. For examples, in intramolecular Diels-Alder reaction of N-ally 2-furoyl amides, 2,4,6-tri-tert-butylphenyl group on the nitrogen atom remarkably accelerated the reaction. Although the reaction of ordinal anilide anion with alkyl halide gives N-alkylation product, the alkylation with 2,4,6-tri-tert-butylanilide anion preferentially proceeded on the oxygen atom to give O-alkyl imidate. O-Benzyl imidate, which was obtained by the reaction with benzyl bromide, was used as bezylation reagent of alcohols and carboxylic acids. In contrast to rotational rigidity of 2,4,6-tri-tert-butylanilide, in the anilide enolates, interconversion between the rotamers readily occurs at ambient temperature, and their reaction with electrophiles gave rotamer mixtures of the products in a ratio that depends on the reactivity of the electrophiles. Furthermore, as an application of this isomerization reaction, switching between the anilide rotamers was achieved.

7-Hexyloxy-3-[4’-(3-methylbutyloxy) phenyl]-4H-1-benzopyran-4-one: Study of Smectic behaviour and UV absorption profile

abstractThe intermolecular interaction energies between a pair of 7-Hexyloxy-3-[4’-(3-methylbutyloxy) phenyl]-4H-1-benzopyran-4-one (HMBPB) molecules have been estimated with respect to translational and orientational motions. The complete neglect differential overlap (CNDO/S) method has been employed to calculate the net atomic charge and atomic dipole moment components at each atomic center. The modified Rayleigh-Schrodinger perturbation theory along with multicentered-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a ‘6-exp’ potential function has been assumed for short-range interactions. The total interaction energy values obtained through these computations have been used to calculate the probability of each configuration at room temperature (300K), and isotropic-smectic transition temperature (412.6K). Molecular arrangements inside a bulk of materials and smectic behavior of the compound in terms of their relative order have been discussed. Translational and rotational rigidity of the molecule has been analyzed to understand the smectic behaviour. The UV absorption profile has been estimated using CNDO/S, and INDO/S methods.

Lateral distortional buckling of cellular composite-beams

Abstract In the region of negative bending moments of continuous and semi-continuous steel and concrete composite beams, the inferior portion of the steel section is subjected to compression while the top flange is restricted by the slab, which may cause a global instability limit state know as lateral distortional buckling (LDB) characterized by a lateral displacement and rotation of the bottom flange with a distortion of the section’s web when it doesn’t have enough flexural rigidity. The ABNT NBR 8800:2008 provides an approximate procedure for the verification of this limit state, in which the resistant moment to LDB is obtained from the elastic critical moment in the negative moment region. One of the essential parameters for the evaluation of the critical moment is the composite beam’s rotational rigidity. This procedure is restricted only to to steel and concrete composite beams with sections that have plane webs. In this paper, an equation for the calculation of the rotational rigidity of cellular sections was developed in order to determine the LDB elastic critical moment. The formulation was verified by numerical analyses performed in ANSYS and its efficiency was confirmed. Finally, the procedure described in ABNT NBR 8800:2008 for the calculation of the critical LDB moment was expanded to composite beams with cellular sections in a numerical example with the appropriate modifications in geometric properties and rotational rigidity.

Structure–Activity Relationships of 6- and 8-Gingerol Analogs as Anti-Biofilm Agents

Pseudomonas aeruginosa is a causative agent of chronic infections in immunocompromised patients. Disruption of quorum sensing circuits is an attractive strategy for treating diseases associated with P. aeruginosa infection. In this study, we designed and synthesized a series of gingerol analogs targeting LasR, a master regulator of quorum sensing networks in P. aeruginosa. Structure-activity relationship studies showed that a hydrogen-bonding interaction in the head section, stereochemistry and rotational rigidity in the middle section, and optimal alkyl chain length in the tail section are important factors for the enhancement of LasR-binding affinity and for the inhibition of biofilm formation. The most potent compound 41, an analog of (R)-8-gingerol with restricted rotation, showed stronger LasR-binding affinity and inhibition of biofilm formation than the known LasR antagonist (S)-6-gingerol. This new LasR antagonist can be used as an early lead compound for the development of anti-biofilm agents to treat P. aeruginosa infections.

Gas–magnetic bearings in high-speed rotor systems

The cantilever overhang of a shaft on gas–magnetic bearings significantly affects the output characteristics of a high-speed rotor system. The rotational precision and rigidity of the rotor may be increased by adaptive control of the magnetic forces.

Five-axis machining on CNC milling machines

At the present time, the parts of the machines are becoming more complex and precise. This requires the development of new machining technologies. In these conditions, multi-axis CNC machining is one of those technologies. In spite of the 20-year history of development, this approach still requires increasing efficiency in implementation to modern tasks. This article presents classification of the five-axis machines depending of the Z-axis location and the axis types and configuration. By default, Z-axis is spindle axis, and therefore, spindle location is determines the machine type (a vertical or horizontal machine). The particular configuration depends on which two of the three rotation axes are used and where they are located. Catalogues review gave the advantages, features and fields of the application of the particular configuration of five-axis machines. This article shows that path generation and vibrations are the main keypoints for improvement of five-axis machining. Path strategies evaluates from linear to advanced trochoidal with features detection. The high-speed machining is the main approach for finish five-axis machining, but other approaches are also used. Because of lower rigidity the vibration during five-axis machining could be both regenerative and forces depending on tool rotation speed and rigidity of machining system. The traditional methods for vibration decreasing are not effective often.

Topology Optimization of Reinforced Concrete Plane Frames

The definition of the number of columns, as well as their positions in the structure, is one of the tasks of the designer, and has a significant impact on both cost and structural behavior. This work presents a study developed in order to obtain the spacing of reinforced concrete columns of building structures corresponding to the smallest global cost (concrete, steel, and formworks). To achieve this objective, the plane frame was modeled as beam elements supported by springs with rotational rigidity. The optimization design variables are the height of beams and the length of columns. At the beginning of the process, columns were closely positioned, with small spacing among them, being the cost of the whole structure minimized. The less stressed column were removed from the structure, generating a redistribution of efforts. The optimization process was repeated, with the columns being successively removed from the structure. The optimal spacing corresponds to the configuration of minimum cost. The present work presents some examples of structures analyzed by the proposed procedure. It was observed that the optimum column spacing is similar to those suggested by practice.

Seismic design of buckling-restrained brace welded end connection considering frame action effects: Theoretical, numerical and practical approaches

The negative effect of in-plane frame action on the performance of buckling-restrained brace (BRB) end connections was confirmed experimentally in the authors’ prior work. The triggering moment induced by rigid-body rotation of BRB ends, and the amplified moment resulting from bending and semi-rigid effects of the connections, were found to be responsible for premature in-plane buckling of the BRB end connections. These effects, however, have not yet been incorporated into the current design procedure. This study aims to further discuss the amplified moment from theoretical, numerical and practical perspectives. As a companion research, the frame action effects of non-moment braced frame and their influences on the cruciform BRB end section using full penetration groove weld connection to the gusset plate are discussed. An analytical model is first proposed for derivation of the BRB end moments considering the concerned frame action effects. Theoretical analysis is conducted to highlight the key parameters affecting the amplified moment factor, an index for evaluating the contribution of the amplified moment. To avoid direct prediction of the complex semi-rigid effects between BRB end and gusset plate, an equivalent rigidity concept is proposed to combine the contributions of both flexural and rotational rigidities of the entire connection. Simple formulae for estimation of the equivalent rigidity and the effective length factor of the connection are determined by finite element analysis. The theoretical BRB end moments using such an equivalent approach are validated experimentally and numerically. A practical approach to simply estimation of the amplified moment factor is also presented. Seismic design procedure for the BRB welded end connection considering the concerned effects are summarized finally.

Research on Mechanical Properties of Main Joints of Chinese Traditional Timber Buildings with the Type of Post-and-Lintel Construction

ABSTRACTThe mechanical properties of Chinese traditional timber buildings with the type of post-and-lintel construction were studied with experimental and theoretical method. There are mainly two types of mortise-tenon joints in the type of post-and-lintel construction which are the Mantou mortise-tenon joint and the Zhi mortise-tenon joint at the foot of short column respectively. In this article, two scaled Mantou mortise-tenon joint specimens and three scaled Zhi mortise-tenon joint specimens designed according to the actual configurations were tested and analyzed. The failure modes, hysteresis curves, skeleton curves, and in-plane rotational rigidity of these two types of mortise-tenon joints under low cyclic loading were obtained. The results show that the hysteretic curves of the Mantou mortise-tenon joints appear to be Z shape and have obvious pinch effects, but the hysteresis curves of the Zhi mortise-tenon joints at the foot of short column appear to be reverse S shape and are not plump. During the process of the test, these two types of mortise-tenon joints orderly pass through elastic stage, yield stage, and failure stage. Furthermore, with the consideration of the nonlinear contact influence of the mortise-tenon joint and the nonlinear stress-strain behavior of the timber material, the mechanical properties of these two types of mortise-tenon joints were analyzed by ANSYS software. The theoretical results agreed well with the experimental results. The relationship of the elastic in-plane rotational rigidity, elastic out-of-plane rotational rigidity, and elastic torsional rigidity of these two types of mortise-tenon joints were achieved, the ratio of these three dimensional rotation rigidity is about 4.64:1.00:0.78 for the Mantou mortise-tenon joints, and is about 0.97:1.00:0.74 for the Zhi mortise-tenon joints at the foot of short column. The results can provide theoretical base for structural analysis and repair design of the Chinese traditional timber buildings with the type of post-and-lintel construction.

Gait deviations in patients operated on bladder extrophy

Based on these vectors the forward – backward bending and rotation from the upper trunk with respect to lower trunk and pelvis, and from the lower trunk with respect to the pelvis were analyzed. Furthermore, the torsional offset (TO) [2] of upper trunkwith respect to lower trunkandpelvis andTOof lower trunkwith respect to pelvis were calculated in the different phases of the gait cycle. Results: In the scoliosis group, mean Cobb angle was 26.03◦ ±7.14 and mean spinal rotation was 22.77%±6.79. Sagital plane kinematics werewithin normal ranges at the ankle, knee and hip. High AI was found for frontal and transverse plane kinematics. In loading respons, AI for peak pelvis obliquity and peak hip exorotation in the scoliotic group was 13.39% and 49.83% respectively, compared to −16.58% and −7.6% in the control group. In pre-swing, AI for peak pelvis exorotation was −67.39% in the scoliotic group compared to 7.26% in the control group. In swing AI for peak hip abduction was −10.90% in the scoliotic group compared to -1.68% in the control group. Upper to lower trunk rotation was continuously clockwise in the scoliosis group while in the control group the rotation was symmetric. Upper trunk to pelvis motion showed a bending of 4.5◦ in the scoliosis group and 32.3◦ in the control group. Rotation was similar in both groups. Lower trunk to pelvis motion was similar in both groups with 3–4◦ of bending and 11.5–12◦ of rotation switching clockwise to anti-clockwise during the gait cycle, but the switch occurred later in the gait cycle in the scoliotic group. Discussion and conclusions: AI up to 14% are reported in normal subjects [2]. We found high AI for frontal and transverse plane motion compared to normal data,which canbe related to the spinal deformation in these planes. An excessive pelvic clockwise rotation coincides with an excessive anticlockwise torsion of the upper trunk. Compensatory hip rotation was found to align the legs into the walking direction. The lack of bending of the upper trunk and the delay in switch in rotation of the lower trunkwith respect to the pelvis might be due to the rotational deformity and rigidity of the scoliotic spine. Insight in how different parts of the trunk act during gait in subjects with scoliosis will enhance the understanding of the pathology and will provide information for optimized treatment. Therefore, further research on a larger population including kinetic analysis will be performed.

The influence of rotational flexibility of beam-column connection on roof plane rigidity of energy-active cover of frame-purlin hall

The paper analyses the influence of the rotational flexibility of beam-column connection on the roof plane rigidity of the longitudinally braced frame-purlin cover of the solid wall hall. The cover is adapted to obtain thermal energy from solar radiation. The roof cover is then provided in the form of a transparent glass barrier which requires considerable roof plane rigidity. The analysis aimed to compare the roof plane rigidity of the frame-purlin cover to those of space structures and truss-purlin covers, depending on the type of longitudinal bracing and rotational rigidity of the beam-column connection. The investigations were conducted for three types of roof plane bracing and different rigidity indexes of the beam-column connection (from u=0 – pin connection, through u=0.25; 0.5; 0.75 – semi-rigid connection, to u=1 – rigid connection). In the transfer of horizontal forces, the interaction of the rigidity of frames with flexible nodes (beam-column) with longitudinal roof plane bracings supported by lateral bracings of gable walls was observed. The highest roof plane rigidity was demonstrated by 2X-shaped and K-shaped braces with rigid nodes at frame corners.

弾性回転剛性と耐力を広範囲・高精度で調整できる鉄骨柱脚

An anchor-bolt-yield-type exposed column-base is typically used in low to medium-rise steel buildings. These column-base details are generally designed to consider the semi-rigid rotation spring, that caused by elastic/plastic elongation of anchor bolts. Such semirigid rotation spring stiffness (rotational rigidity) of column-base have a large effect on the seismic behavior of the building.In this paper, the authors proposed new type of column-base, that hysteresis same to a restoring force characteristics of generally type exposed column-base. And more, the new type of column base can controlled rotational rigidity. An experimental study has been carried out on new type of column-base subjected to cyclic loadings, and the following conclusions were drawn.1) Rotational rigidity of column base changed by the adjusting of anchor bolt length & column-base detail. 2) The proposed models of the restoring force characteristics showed good agreement with the experimental results for all specimens. 3) New type of column base having repaired performance, that anchor bolt can changed after the earthquake.

Seismic Behaviour and Seismic Design of Single-Layer Reticulated Shells with Semi-Rigid Joint System

An investigation of the seismic behaviour and a design method for single-layer reticulated shells with semi-rigid joints is described in this paper. A semi-rigid joint system has some bending and rotational rigidity that lying between that of a rigid-joint and a pin-joint. The seismic capacity of Kiewit reticulated shells with bolt-ball joints is analyzed in detail on the basis of the bending rigidity of the bolt-ball joint reported by others. The change rules of natural frequency and seismic internal force coefficient are reviewed by analyzing of large-scale shells with different span, depth-to-span ratio, bending rigidity, roof load, section size of members and seismic wave parameters. The seismic internal force coefficient (under the influence of bending moment) for shells with a semi-rigid joint system is summarized statistically to provide the maximal seismic response envelop.