Quasi-non-linear fracture mechanics analysis of splitting failure in moment-resisting dowel joints

This article addresses the splitting failure of moment-resisting dowel-type fastener joints, in which the failure may be attributed to the perpendicular-to-grain loading of one single dowel located close to the end of a beam. A quasi-non-linear fracture mechanics model based on beam on elastic foundation theory is applied. A simple approximation suitable for practical design is also proposed. Model predictions of the influence of edge distances and end distances are compared with test results.     

Splitting strength of beams loaded perpendicular to grain by dowel joints

A linear elastic fracture mechanics model for calculation of the splitting strength of dowel-type fastener joints loaded perpendicular to grain (Van der Put/Leijten model) has previously been presented, and now forms the basis for design in Eurocode 5. The original Van der Put/Leijten model was derived using a number of simplifying assumptions, e.g., that the normal forces in the cracked parts of the beam can be ignored, leading to a solution that does not involve the effect of an initial crack. In the present article an extended version of the Van der Put/Leijten model is derived without any simplifying assumptions, and it is shown that the original Van der Put/Leijten model appears as a special case, namely by assuming that only contributions from shear deformations are significant. The model presented here involves the effect of an initial crack and may be characterized as a generalized linear elastic fracture mechanics model. Results of tests showing the influence of initial cracks of various lengths are presented and compared with the predictions.     

Lateral resistance of anchor-bolt joints between timber sills and foundations III: numerical simulations of the effect of sill thickness on the effective lateral resistance of multiple anchor-bolt joints

Effective lateral resistance of multiple anchorbolt joints was estimated by considering sill thickness or length/diameter ratios of anchor bolts. Load-slip relationships of single anchor bolt joints were analyzed by the stepwise linear approximation based on the generalized theory of a beam on an elastic foundation and the criterion of “fracture bearing displacement” for several sill thicknesses or length/diameter ratios of anchor bolts. Monte Carlo simulations of the effective lateral resistance of multiple anchor-bolt joints were conducted using the analyzed load-slip curves of single anchor-bolt joints. Effective resistance ratios of multiple anchor-bolt joints were simulated for some combinations of length/diameter ratios of anchor bolts, lead-hole clearances, and number of anchor bolts. The simulated results are: (1) the influence of lead-hole clearance becomes more apparent as length/diameter ratios of single anchor-bolt joints decrease; (2) there is no obvious effect of number of anchor-bolts over the range of 5 to 15; (3) average effective resistance ratios can be adopted for allowable stress design; and (4) reduction of effective resistance ratios should be considered particularly for small length/diameter ratios of anchor-bolt joints.     

ONE IMPLICIT FUNCTION THEOREM

In this paper, we obtained one implicit function theorm,which, in the inverse function cases, becomes to the necessary and sufficient condition for the mapping is a homeomorphism.     

Use of ethanol in the treatment of distal tarsal joint osteoarthritis: 24 cases

Reasons for performing this study: Intra‐articular ethanol has been described to promote distal tarsal joint ankylosis. Its use and results in clinical cases affected by osteoarthritis (OA) have not been reported. Objectives: To describe and evaluate the results of treatment of distal tarsal joint OA by facilitated ankylosis stimulated by intra‐articular ethanol injection. Methods: Twenty‐four horses met the inclusion criteria of tarsometatarsal and centrodistal joint OA diagnosed by a positive response to intra‐articular analgesia, radiographic evaluation and recurrence of lameness ≤4 months after intra‐articular medication with a corticosteroid. Horses were sedated and, following a radiographic contrast study of the tarsometatarsal joint, medication with 2–4 ml of either 100% pure ethanol (G100) or a 70% ethanol (G70) solution was applied. Horses were classified as improved based on a 50% reduction from initial lameness grade combined with an increase in exercise level. Results: Of the 24 horses included in this study, 20 had the treatment performed bilaterally and 4 unilaterally. All horses were available for initial follow‐up examination and 21 for a second one 6–9 months after treatment. This represented a total of 44 treated limbs and 35 available for long‐term follow‐up. Of these, 21/35 (60%) were considered improved, which corresponds to 11/21 horses (52%). Of 21 horses, 4 (19%) deteriorated and 2 of these developed significant complications related to treatment. Conclusions: Distal tarsal joint ankylosis with ethanol should be considered a safe and economic treatment in cases of distal tarsal joint OA that fail to show long‐term improvement with intra‐articular corticosteroid treatment. Potential relevance: Ethanol should be considered in the treatment of certain cases of distal tarsal joint OA. The importance of performing an adequate radiographic contrast study of the tarsometatarsal joint prior to treatment is highlighted.     

草原土壤胀缩运动的发生机制研究

着重调查草原地裂缝的空间静态分布及时间动态分布,并调查土壤及植被状况,研究草原土壤胀缩运动的发生机制,结果表明:土壤的开裂主要与土壤粘粒(<0.001mm)含量有关,土壤粘粒含量越高,土壤胀缩程度越大。认为土壤胀缩运动主要决定于土壤粘粒的含量,同时季节性冻融作用与干湿交替作用是导致土壤胀缩运动的直接因素。     

经济形势严峻背景下劳动法应对调整制度研究

在因全球新冠肺炎疫情肆虐导致经济萎缩时,德、日等发达国家企业实行短时工作制,通过减少正常工作时间、降低工资来避免裁员,从而保持社会稳定。我国目前的劳动法律体系中,并无这样的制度安排。构建劳动法应对调整制度,是完善劳动法体系的需要,有利于保障社会平稳发展。全球经济萎缩背景下,劳动法应对调整制度应由缩短工作时间、鼓励企业尽量不裁员、改革失业补助政策、暂缓调整最低工资标准及社会刺激计划等组成。     

神蜂精的药效学试验 Ⅱ.神蜂精对虎斑蛙神经传导和肌肉收缩力的影响

神蜂精对虎斑蛙的神经电位传导有很强的阻滞作用． ２５％ 的神蜂精溶液在给药后４ ｍ ｉｎ 对蛙坐骨神经动作电位的传导开始有明显的阻滞作用（Ｐ＜ ０．０５）; ５０％ 以上神蜂精溶液在２ ｍ ｉｎ 内就开始有显著阻滞作用（Ｐ＜ ０．０５）,并随给药时间推移,阻滞作用不断加强,表现出明显的时程效应．此外,不同剂量的神蜂精组间还表现出明显的剂量依赖性阻滞效应（ｒ＝ ０．９８）,而对照组１０ ｍ ｉｎ 内仍无阻滞作用．神蜂精对蛙的肌肉收缩力也有抑制作用．在给药后２～４ ｍ ｉｎ, ２００％ 的神蜂精（指内含２００个蜂单位蜂毒）与对照组对蛙缝匠肌收缩力均有抑制作用,但前者明显高于后者（２ ｍ ｉｎ 时, Ｐ＜ ０．０１; ４ ｍ ｉｎ 时, Ｐ＜ ０．００１）,且１０ ｍ ｉｎ 后肌肉收缩完全受抑制．上述试验表明神蜂精具有较强的阻滞神经动作电位传导和抑制肌肉收缩作用,证明了神蜂精对椎间盘突出症等病症引起的神经酸痛和肌肉犟痉痉挛具有较好的缓解治疗作用．     

Age-related changes in contractions of chicken aorta and ischiadic artery

The characteristics of the contraction of vascular smooth muscle were examined in thoracic aorta and ischiadic artery of chickens aged 3, 6, 10 and 18 weeks. High K⁺ solution induced a sustained contraction in smooth muscle preparations of aorta and ischiadic artery in vitro . The contraction of the ischiadic artery became greater with age, whereas the contraction of the aortic preparation did not. In the ischiadic artery, the magnitude of the contraction divided by the weight of the muscle preparation was constant at all ages studied. However, those in the aortic preparation decreased with age. These results suggest that the changes in the contractile responses of vascular smooth muscle owing to the age of chickens vary widely according to the preparations of blood vessels, and that the functional smooth muscle cells in the thoracic aorta of chicken do not increase with age.     

Fracture of multiply-bolted joints under lateral force perpendicular to wood grain

The crack initiation and propagation of multiplybolted joints subjected to lateral forces perpendicular to the grain were analyzed. Two types of bolted joint were subjected to lateral loads perpendicular to the grain. One had joints of two bolts aligned with the wood grain (type H), and the other had joints of two or three bolts aligned perpendicular to the grain (type V). The crack initiation and propagation were analyzed by means of the average stress method (ASM) and linear elastic fracture mechanics (LEFM), respectively. The maximum loads calculated by LEFM agreed comparatively well with the experimental results, and it was proved that the LEFM was an appropriate tool to analyze the fracture of multiply-bolted joints subjected to a force perpendicular to the grain. It was also found that the multiply-bolted joints failed with the fracture of the wood before the joints yielded, and that it caused a considerable decrease of the maximum loads. The reduction of strength should be considered in the design of multiply-bolted joints subjected to lateral forces perpendicular to the grain.Part of this work was presented at the annual meeting of the Architectural Institute of Japan, Hikone, September 1996