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08 June 2008, Volume 30 Issue 3
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    Application study
    2008, 30(3):  47-51.  doi:10.6052/1000-0992-2007-452
    Abstract ( 948 )   PDF (963KB) ( 1415 )  
    The dynamical stability of biped locomotion and the dynamical process of jumping motion of human body are analyzed in this paper. Some problems related to the race-walking and running are discussed.
    2008, 30(3):  63-66.  doi:10.6052/1000-0992-2007-548
    Abstract ( 1243 )   PDF (709KB) ( 679 )  
    In this paper, the effect of the section size on the strain energy of vaulting poles is investigated in the static equilibrium condition. The variation of the wall thickness of the vaulting pole along its length is obtained. The deformation curve of the vaulting pole under the ultimate state is computed by Finite Element Method, and the assumption that the ultimate deformation curve is in a form of arc is verified as well. The performance index is modified based on the energy conservation, taking into account the contribution of the vaulter's muscle work to the height of pole vaulting. The computational formula of the vaulting height is derived as a function of the weight, the height of athletes and the pole grasp height.
    Review
    2008, 30(3):  10-14.  doi:10.6052/1000-0879-2007-598
    Abstract ( 1051 )   PDF (1443KB) ( 792 )  
    Biomechanics in sports applies mechanical concepts and principles to study human body movements. It is important for understanding human body movements, improving sports performance, preventing sports injuries, and helping rehabilitation. This article reviews its history, current research areas, and related studies in China, together with its development in future.
    Application study
    2008, 30(3):  36-40.  doi:10.6052/1000-0879-2008-010
    Abstract ( 1031 )   PDF (3068KB) ( 473 )  
    This paper investigates the consolidation temperature of large-volume concrete used in the stadium which was constructed for the 2008 summer Olympic Games hold in Beijing. The variation and distribution of the temperature during consolidation of the concrete are studied by finite element method. The real boundary conditions of temperature field and climate effect are considered in modelling the practical construction environment.
    2008, 30(3):  41-46.  doi:10.6052/1000-0879-2008-011
    Abstract ( 1082 )   PDF (2808KB) ( 634 )  
    The thermal stress in consolidation of concrete is analyzed for construction of the National Stadium, the main track and field stadium for Olympics 2008 in Beijing. A numerical simulation of the thermal stress was performed by finite element method, considering the deformation induced by shrinkage and creep of the concrete. A method to deal with the boundary condition of traction was adopted according to the practical situation of the stadium. An optimal procedure was suggested to prevent the surface cracking and adjust the thermal stress of the concrete. This study contributes to achieve lower cost of the detection, higher efficiency and better quality of the construction.
    2008, 30(3):  89-90.  doi:10.6052/1000-0879-2008-049
    Abstract ( 937 )   PDF (1852KB) ( 1131 )  
    The ETFE film structure is a newly developed architectural form which applys new material. Today , after the National Swimming Center's finish, this new film material has already showed a great ability in entering the architecture market in China, when people are still marvelling at its infinite charm. The development, property and application of main material for film structure in water cubic---ETFE, is introduced in this paper.
    2008, 30(3):  75-79.  doi:10.6052/1000-0879-2008-052
    Abstract ( 1112 )   PDF (1162KB) ( 830 )  
    The path of discus flight and the effects of the throw velocity/angle, spin and wind conditions on discus flight are discussed in this paper, considering the aerodynamic force on the discus. The theoretical and experimental investigations of discus flight indicate the following useful conclusions: the optimum combination of throw angle and discus inclination angle is 35°/26° at zero wind, while 45° is not the best release angle due to the aerodynamic force; different combinations of throw angle and inclination angle should be adopted according to local wind conditions; a spin speed of 25 r/s when releasing the discus is enough to stabilize the discus's initial orientation.
    2008, 30(3):  56-59.  doi:10.6052/1000-0879-2008-122
    Abstract ( 1223 )   PDF (666KB) ( 505 )  
    It was believed that plantar pressure might play an important role in the beneficial effect of backward walking exercise on health. Plantar pressure distributions of 12 healthy boys during normal and backward walking were collected. The sampling rate was 250\,Hz. The maximum force, pressure, and impulse of different regions during backward and normal walking were compared. The plantar foot plane is divided into 10 regions, including first, 2nd, 3rd, 4th, 5th metatarsal head (MTH), great toe (GT), lesser toes (LT), midfoot (MF), lateral heel (LH), medial heel (MH). The plantar pressure distributions of normal and backward walking were found significantly different. Compared with normal walking, the loading of the MF, 4th, and 5th MTH during backward walking were significantly greater, whereas those of the first and 2nd MTH were significantly smaller. These results suggest that plantar pressure distributions during backward walking may contribute to the improvement effects of backward walking exercise in fitness and rehabilitation.
    2008, 30(3):  71-74.  doi:10.6052/1000-0879-2008-123
    Abstract ( 1276 )   PDF (769KB) ( 667 )  
    Forward handspring and salto double forward piked is one of the most difficult movements in men's vaulting horse. Hu Junjie is the only Chinese gymnast who brought this movement to success. Based on a 3D motion analysis, the kinematic features and the technical characteristics of the forward handspring and salto double forward piked performed by Hu Junjie are analyzed in this paper. The variations of some kinematic parameters, such as the displacements, horizontal and vertical velocities of mass center, the displacements and angles of main joints are obtained. The results of analysis can provide a technical and theoretical guidance for further design of movements for Chinese gymnasts in this field.
    Terms
    2008, 30(3):  121-121.  doi:10.6052/1000-0879-2008-132
    Abstract ( 1294 )   PDF (207KB) ( 499 )  
    Application study
    2008, 30(3):  28-35.  doi:10.6052/1000-0879-2008-163
    Abstract ( 1094 )   PDF (6333KB) ( 620 )  
    The National Stadium is one of the most important stadiums for Olympics 2008. The stadium roof (114 m × 144.5 m) is two-way beam string structure (TBSS), a new and efficient spatial structure. To study the mechnical features of the structure, a 1:10 structure model of 11.4 m × 14.45 m is made. The following cases are included in the experiment: different tension methods, different load cases and emergency load cases (such as when the cables are destroyed). Transverse cable force, longitudinal cable force, stresses and deformation in the structure are studied in detail.
    Interesting mechanics story
    2008, 30(3):  115-119.  doi:10.6052/1000-0879-2008-182
    Abstract ( 964 )   PDF (1328KB) ( 620 )  
    Application study
    2008, 30(3):  24-27.  doi:10.6052/1000-0879-2008-199
    Abstract ( 997 )   PDF (873KB) ( 717 )  
    Based on fire plume models, the smoke temperature above the fire source at different heights was predicted for typical fire scenarios of Beijing National Stadium of Olympics 2008. The strength and modulus of elasticity of steel under different temperatures were considered to determine the critical temperature value. Accordingly the fire hazard region for steel structures in Beijing National Stadium of Olympics 2008 was determined to be with in 10.2\,m above the seats.
    2008, 30(3):  60-62.  doi:10.6052/1000-0879-2008-208
    Abstract ( 1355 )   PDF (993KB) ( 693 )  
    As a special skate board, the vigor board can move forward by swing and twisting of the body of user. In this paper the dynamic principle of the motion of vigor board is analyzed. The friction forces on wheels acted by the ground produce an impulse effect when the front and rear broads rotate periodically as a result of body's motion. The formula to calculate the average impulse force is derived, and the zigzag of trajectory is explained.
    2008, 30(3):  67-70.  doi:10.6052/1000-0879-2008-260
    Abstract ( 1038 )   PDF (1159KB) ( 579 )  
    In this paper, finite element method (FEM) software is used to simulate the large deformation process of pole during the pole vaulting. The deformation, jump heights and performance index are obtained from the calculations for poles made of different materials. The highest records are predicted for different materials' poles through the design of pole sections. Carbon fiber reinforced composites poles with uniform and varying sections are designed for Bubka as an standard, to let him to reach higher height.
    2008, 30(3):  52-55.  doi:10.6052/1000-0879-2008-272
    Abstract ( 1576 )   PDF (745KB) ( 947 )  
    The taking-off process in springboard diving motion is analyzed in this paper on the basis of mechanical model of diver/springboard system. The idea of improving spring-board diving performance by increasing taking-off energy is suggested. The mechanical explanation of various current spring-board taking-off techniques is given.
    Review
    2008, 30(3):  15-23.  doi:10.6052/1000-0879-2008-297
    Abstract ( 1219 )   PDF (18476KB) ( 1387 )  
    Retractable roof is a type of structure, which or a part of which can open or close within a short time. In this paper we discuss several typical structures. The movement of retractable roof makes the design of retractable roof structures very complex. Compared with the conventional buildings, the design of retractable roof structures is composed of three parts: architecture, structure and mechanism. They are mutually related.
    2008, 30(3):  1-9.  doi:10.6052/1000-0879-2008-316
    Abstract ( 1161 )   PDF (3651KB) ( 718 )  
    This article will adhere to the subject of association of mechanics with sports in Olympic Games, and give a concise description, with illustrations of a few examples, of the common origin of mechanics and Olympic Games, the past and future contributions of mechanics to the advancement of sports in Olympic Games. Thus the readers will have a bird's-eye view of the relationship between mechanics and sports in Olympic Games, which will provide the foundation for further exploration of relevant details regarding mechanics in any specific sport in Olympic Games.