Selection Of Joints Research Articles

Fragility function development and seismic loss assessment of expansion joints

SummaryExpansion joints are used as a special connection equipment between adjacent buildings to accommodate the relative motions generated by wind, thermal, or earthquake loads, but they often exhibit damage during severe earthquakes. The level of damage and safety factors required to avoid loss of function are not well considered in current design practices. The objective of this paper is to provide quantitative information on the seismic damage probability of common expansion joints and the associated repair costs. The designer and engineer can refer to this information as a basis for decision making in the selection of expansion joints. Four common types of expansion joints are considered: high‐ and standard‐performance floor and wall expansion joints, whose damage states have been evaluated recently by the authors through shaking table tests. First, the fragility functions of expansion joints for seven damage patterns are developed utilizing the test results. Next, the vulnerability of expansion joints installed between adjacent building models is assessed via incremental dynamic analysis. The recommended level of safety factor to ensure the function of expansion joints is discussed. Finally, a procedure for cost‐effective selection of expansion joints is introduced, where case studies are examined using buildings with different characteristics. The presented results are deemed to be beneficial for improving the design practice of expansion joints and for reducing future seismic loss.

Damage sequence and safety margin assessment of expansion joints by shake table testing

SummaryThe performance of nonstructural components has attracted attention, and previous large earthquakes have resulted in widespread damage to expansion joints. In contrast to the main structural components, for which ductility beyond the design tolerance is ensured, the safety margin of nonstructural components classified as the product of mechanical engineering, such as expansion joints, is uncertain. This paper investigates the damage sequence and safety margin of expansion joints through shake table testing. The expansion joints were installed to connect 2 rigid steel frames with short and long natural periods. Four commonly used types, high‐performance and standard‐performance floor and wall expansion joints, were tested. Seven damage patterns of the 4 expansion joints were observed, and most of the damage patterns were considered displacement dependent. The damage mechanisms and relative displacements at the moment of damage were identified by using strain gauges attached near collision and damage locations. The high‐performance expansion joints showed only minor damage beyond the design motion range, whereas the standard‐performance expansion joints exhibited minor damage below the design motion range and failure at the design motion range or slightly beyond. For each damage state, repair information was obtained through a questionnaire to an expansion joint manufacturer, and the sum of the initial cost and repair cost for high‐performance and standard‐performance expansion joints was compared. The results will be useful for the selection of expansion joints in the design process.

Design charts for end-plate beam-to-column steel joints

The component method provided by Eurocode 3 for the evaluation of strength and stiffness of beam-to-column joints is considered a very laborious procedure that is often difficult to apply. This is owing to the large number of geometrical and mechanical parameters involved in the analytical formulations. Hence, the component method is only seldom used for practical applications, with the consequence that the real behaviour of joints in terms of strength and stiffness is not accounted for. The aim of this paper is to provide an automatic tool that allows an easy-to-use application of the component method for the evaluation of beam-to-column joints stiffness and strength, and also enables plotting of the moment–rotation curve describing the joints' behaviour. Moreover, the proposed tool is used to carry out parametric analyses for two bolt-rows in end-plate beam-to-column steel joints. This is addressed to the definition of design charts for the optimal selection of joints.

Selection, Maintenance and Acoustic Diagnostics of Expansion Joints in Bridges Located in Areas with Ground Deformations

Abstract In the paper are presented general rules of the assortment of expansion joints in bridges located in areas being under the mining impacts. The maintenance problems associated with ground deformations are also mentioned. The special attention is given to the noise emitted by expansion joint devices. A legal status in the protection from noise and factors affecting this noise are discussed.

Tracking a Subset of Skeleton Joints: An Effective Approach towards Complex Human Activity Recognition

We present a robust algorithm for complex human activity recognition for natural human-robot interaction. The algorithm is based on tracking the position of selected joints in human skeleton. For any given activity, only a few skeleton joints are involved in performing the activity, so a subset of joints contributing the most towards the activity is selected. Our approach of tracking a subset of skeleton joints (instead of tracking the whole skeleton) is computationally efficient and provides better recognition accuracy. We have developed both manual and automatic approaches for the selection of these joints. The position of the selected joints is tracked for the duration of the activity and is used to construct feature vectors for each activity. Once the feature vectors have been constructed, we use a Support Vector Machines (SVM) multiclass classifier for training and testing the algorithm. The algorithm has been tested on a purposely built dataset of depth videos recorded using Kinect camera. The dataset consists of 250 videos of 10 different activities being performed by different users. Experimental results show classification accuracy of 83% when tracking all skeleton joints, 95% when using manual selection of subset joints, and 89% when using automatic selection of subset joints.

ТЕРМИНОЛОГИЧЕСКИЕ АСПЕКТЫ В АНАТОМИИ ЧЕЛОВЕКА

In anatomy, as in no other science, terminology is an important tool that reveals the structure of an organ or its topographic peculiarities. Anatomical terminology is inherent in conservatism, which ensures the continuity and unity of views on the structure of organs. But there are sometimes terms that may be unsuccessful and hamper a common understanding of the name of any part of the body in clinical or educational aspects. So, in our opinion, the canaliculi of tympanic nerve and chorda tympani don’t match the definition of a canal or canaliculus. The term joint does not reflect the shape of the articular surfaces. Therefore, the selection of condylar joints based on the shape of the articular surfaces, difficult, incompetent, since they have an ellipsoidal shape.

Clinical examination or whole-body magnetic resonance imaging: the Holy Grail of spondyloarthritis imaging

Whole-body magnetic resonance imaging allows acquisition of diagnostic images in the shortest scan time, leading to better patient compliance and artifact-free images. Methods of clinical examination of the anterior chest wall joints vary between physician groups and consideration of the rules of rib motion is suggested. The type of joint and its synovial lining may also aid imaging/clinical correlation. This well-written study by experts in the field with a standardized design and methodology allows good scientific analysis and suggests the advantages of whole-body magnetic resonance imaging in anterior chest wall imaging. Selection of clinical examination criteria and specific joints may have had an influence on the study results and the lack of association reported.

Nano-Hardness Testing of Wear Particles in Sheep Knee Joints

This work aimed to establish a suitable procedure for establishing wear particle hardness and to investigate if the hardness of articular cartilage wear particles increases with increasing grades of osteoarthritis. To achieve the goals a selection of fresh sheep knee joints were obtained and consequently worn in a specially designed wear simulator. Wear particles were then removed from the joint using a syringe and prepared for hardness testing. In order to test the hardness of the wear particle samples nanoindentation was used. Once completed statistical analyses and correlation analyses were performed in order to find any relationships present. This was the first time that the hardness of the wear particles was tested and studied. As a result of the tests performed a general relationship between wear particle hardness and osteoarthritis grade was able to be determined. It was also determined that further work needed to be conducted on the experimental procedure to increase the accuracy of the results obtained.

Topology optimization by penalty (TOP) method

In traditional structural topology optimization (TO), the material properties of continuum finite elements of fixed form and coupling are varied to find the optimal topology that satisfies the design problem. We develop an alternative, fundamental formulation where the design space search is dependent on the coupling, and the goal of the topology optimization by penalty (TOP) method is to determine the optimal finite element coupling constraints. By this approach, seemingly disparate topology design problems, e.g., the topology design of structural supports, topology optimization for fluid mechanics problems, topology optimization with convective heat transfer, topology optimization by the element connectivity parameterization method, and the optimal layout of structural joints, can be understood as related formulations under a common topology optimization umbrella, and more importantly, this general framework can be applied to new design problems. For example, in modern multibody dynamics synthesis, the geometric form of finite elements of fixed material properties and interconnectivity are varied to find the optimal topology that satisfies the mechanism design problem. The a priori selection of coupling, e.g., by revolute or translational joints, severely limits the design space search. The TOP method addresses this limitation in a novel way. We develop the methodology and apply the TOP method to the diverse design problems discussed above.

A comparison of clinical vs ultrasound determined synovitis in rheumatoid arthritis utilizing gray-scale, power Doppler and the intravenous microbubble contrast agent 'Sono-Vue'(R)

Synovitis in rheumatoid arthritis (RA) is assessed clinically by the presence of joint tenderness and swelling. Synovial thickening and increased vascularity may also be detected by high-resolution ultrasonography (US) and power Doppler (PD). This study investigated the relationship between clinical and sonographic features of synovial disease utilizing US, PD and the contrast agent Sono-Vue. Forty RA patients were recruited. One proximal inter-phalangeal or metacarpophalangeal joint was selected per patient, as being unambiguously either: swollen and tender, just swollen, just tender or neither swollen nor tender (Nil). Ten joints were selected per clinical group. On US, the mean synovial thickness was measured and synovial hypertrophy and erosions were graded subjectively. Synovial vascularity demonstrated by PD was scored subjectively pre- and post-contrast. All grades of synovial vascularity were found in each clinical group including the Nil group. There were significant differences between the four clinical groups for both synovial hypertrophy (P = 0.024) and PD scores pre- (P = 0.022) and post- (P = 0.039) contrast. Tender-only joints showed significantly less vascularity than other groups. Post-contrast, the median PD scores increased in all but the Nil group, in some cases from the normal to abnormal range. Synovitis demonstrated by US and PD is not predicted by patterns of disease as described by joint swelling and tenderness despite unambiguous selection of joints. Synovial vascularity was the least in tender-only joints and was heterogeneous in all other groups, including Nil joints. These findings question the reliability of traditional clinical signs in RA synovitis assessment.

Fatigue initiation in adhesively-bonded single-lap joints

This paper presents detailed experimental fatigue data obtained from a selection of joints tested under cyclic loads. Some were tested to failure to determine fatigue load-life data. The other specimens were tested to induce different levels of damage. Multiple strain gauges (SGs) were used to record the change in backface strain during the testing, allowing measurement of damage in different locations. The overlap region was then sectioned and polished so it could be inspected using microscopy. The experimental results showed that damage first appeared in the fillet, appearing as a change in adhesive colour in a specific area. Cracks were observed in one specimen, which was tested for a higher number of cycles. A damage scale based on area affected, change in colour and size of cracks is proposed to classify the damaged sections. A result of this work is to tie the backface strain readings with the damage scale allowing damage to be assessed in a non-destructive manner.

Mechanical design of the humanoid robot platform, HUBO

The Korea Advanced Institute of Science and Technology (KAIST) humanoid robot-1 (KHR-1) was developed for the purpose of researching the walking action of bipeds. KHR-1, which has no hands or head, has 21 d.o.f.: 12 d.o.f. in the legs, 1 d.o.f. in the torso and 8 d.o.f. in the arms. The second version of this humanoid robot, KHR-2 (which has 41 d.o.f.) can walk on a living-room floor; it also moves and looks like a human. The third version, KHR-3 (HUBO), has more human-like features, a greater variety of movements and a more human-friendly character. We present the mechanical design of HUBO, including the design concept, the lower-body design, the upper-body design and the actuator selection of joints. Previously we developed and published details of KHR-1 and KHR-2. The HUBO platform, which is based on KHR-2, has 41 d.o.f., stands 125 cm tall and weighs 55 kg. From a mechanical point of view, HUBO has greater mechanical stiffness and a more detailed frame design than KHR-2. The stiffness of the frame was increased, and the detailed design around the joints and link frame was either modified or fully redesigned. We initially introduced an exterior art design concept for KHR-2 and that concept was implemented in HUBO at the mechanical design stage.

KBS-selection of universal joint used in agricultural machinery

Abstract In this study, a knowledge-based system was developed to a id in selection of universal joint, which is used in agricultural machinery (KBS_UJ). In selection of the universal joints, it is very important to choose the suitable mechanism for the agricultural machinery, which is going to be used. A main programme was written by using the AutoLISP and DCL languages. According to the Turkish Standards in different categories, maximum torque and maximum power, critical revolution number and power capacities of various tube profiles, joint open length depending on the tube profile type, joint closed dimensions and joint tube dimensions were determined and selected joint was drawn in 2D. The system was tested on joint producer in order to validate the decision obtained. The system can be helpful to producer, farmer or safety working

Evaluation of Performance of Bridge Deck Expansion Joints

The bridge deck expansion joint is an important element in the functioning of bridge structures. When joints fail to function properly, they can create problems out of proportion to their size. Selection of a good joint for use can create fewer bridge maintenance problems. The purpose of the study was to evaluate the performance of several types of joints currently in use on Indiana highway bridges. The types of joints investigated are compression seal, strip seal, integral abutment, poured silicone, and polymer modified asphalt. The research was accomplished through questionnaire surveys, analysis of Indiana Department of Transportation roadway management data, and expert interviews. The questionnaire survey identified the problems and their causes and the merits and potential improvements of each type of joint. The analysis of Indiana roadway management data ranked the performance of different types of joints based on the deterioration rates estimated by the regression coefficients. The expert interviews investigated the practices of Indiana and its surrounding states regarding the selection and maintenance of joints. Based on the research results, several suggestions were proposed to ensure the longer service life of expansion joints.

An algorithm for the kinematic analysis and optimal input joint assignment of recursive mechanisms

A multiloop mechanism is called recursive if its kinematic analysis can be reduced to the analysis of a recursive loop sequence, i.e. a sequence of loops with trivial, linear coupling between these loops. The kinematic analysis of multiloop mechanisms by symbolic or iterative methods is simplified substantially if a (partial) recursive loop sequence is found. Recursiveness depends on the selection of input joints and frequently inputs are not preassigned but an assignment must be found such that a recursive loop sequence exists. The presented algorithm provides all possible input joint assignments and corresponding recursive loop sequences of arbitrary recursive mechanisms. The core of the algorithm is of linear complexity in the number of bodies plus joints. Through this efficiency an analysis of mechanisms with thousands of bodies and joints becomes practically feasible.

Workspace evaluation of Stewart platforms

The workspace and the dexterity of a Stewart platform are affected by the choice of its major dimensions, actuator stroke and the kinematic constraints of its joints. An investigation of the effects of these parameters on workspace volume of the platform is presented. The obtained results were normalized so that they could be used as a design tool for the selection of dimensions, joints and actuators.

Forward kinematics of walking machines with pantograph legs based on selections of independent joints

This article studies the forward kinematics of walking machines with pantograph legs. The walking machine is supported by three legs and each leg has 3 degrees of freedom (dof). Because the body has 6 dof motion, only 6 joint variables among the 9 are independent. Thus, there are 84 possible ways to select the 6 independent joint variables. It is shown that the complexity of the forward position solutions is very much dependent on the selection of independent joints. In the category of 3:2:1 (the 3 numbers denote the number of independent joints at each of the supporting legs), all 54 combinations give closed-form solutions. Among the 27 combinations of category 2:2:2, 10 possess closed-form solutions, 16 yield to higher-order polynomials, and 1 gives no solutions. The 3 combinations of category 3:3:0 give no solutions. The results are useful to control and simulation of walking machines and other parallel systems consisting of pantograph subchains such as parallel manipulators, multifingered hands, and multiply coordinated manipulators. © 1992 John Wiley & Sons, Inc.

Acoustic emission inspection of the strength of joints made by resistance welding

1. It was shown that the formation of weld joints in resistance welding in the solid state is accompanied by dynamic processes caused by development of plastic deformation. 2. The development of plastic deformation occurs discretely in short intervals of time. 3. A correlation was established between the strength of a joint and the acoustic emission parameters. 4. A method was developed for determination of a criterion of selection of joints with a specified strength and an apparatus using this method was developed.

The significance of sesamoids and retro‐articular processes for the mechanics of joints

Extensor muscles may insert by means of flexible tendons that wrap round the joint, through rigid sesamoids, or on to retro‐articular processes. The three types of joint are examined, and equations are derived relating the force required in the muscle to the force exerted on the environment. A selection of mammalian joints are analysed to illustrate the theoretical conclusions.

Composites for large space structures

A preliminary study of advanced composites and truss-type designs for application to large space structures is discussed. The benefits of advanced composite materials for large space structures and examples of large space structure design concepts and construction techniques are presented. Criteria are developed to guide the selection of structural elements, joints, and on-orbit fabrication techniques for truss-type structures and a ranking of candidate on-orbit fabrication techniques is accomplished in accordance with the criteria developed. On the basis of study results, recommended research and development goals for design, construction, and on-orbit fabrication of large space structures are established.