Bearing Capacity of Mixed Pile with Stiffness Core   总被引：3，自引：0，他引：3  

岳建伟姜忻良  凌光荣 《天津大学学报(英文版)》2006,12(3):204-208

To study load transfer mechanism and bearing capacity of a mixed pile with stiffness core (MPSC), which is formed by inserting a precast reinforced concrete pile (PRCP), in-situ tests involving MPSCs with different lengths, diameters, water cement ratios and PRCPs, cement mixed piles, and drilling hole piles, were carried out. Limit bearing capacities, load-settlement curves and stress distribution of MPSCs and mixed piles were obtained. The load transfer between cement soil and PRCP was analyzed by finite element method (FEM). Test results and FEM analysis show that an MPSC has fully utilized the big friction from a cement mixed pile and the high compressive strength from a PRCP which transfers outer top load into the inner cement soil, and that inserting a PRCP into a mixed pile changes the stress distribution of a mixed pile and improves frictional resistance between a mixed pile and soil. The length and the section area on PRCP of an MPSC both have an optimum value. Adopting MPSC is effective in improving the bearing capacity of soft soil ground.  相似文献   

钢筋砼结构施工期楼层承载力的安全性复核     

王君章 《大连大学学报》2011,32(3):72-74

提出多层钢筋砼结构在施工期间,施工荷载在各相关楼层间的分配及承载力安全性复核的方法。解决了多层砼结构模板支撑系统的安装及拆除无依据、凭经验施工的问题。  相似文献   

受周期力作用刚度不均等转轴的副临界转速     

谭世复 《湖州师范学院学报》1989,(5)

有关转轴临界转速,迄今已有不少讨论,本文就刚度不均等转轴,提供一种临界转速的分析计算方法。  相似文献   

并联机床主模块静刚度的有限元分析(英文)   总被引：4，自引：0，他引：4  

周立华  王玉茹  黄田  MODLER K H 《天津大学学报(英文版)》2001,7(1)

借助商用有限元分析软件 ANSYS,首先研究了并联机床主模块各主要构件对其刚度的贡献 ,发现机架起主要作用 ;进而研究了约束条件、支链长度以及不同工作方式对其刚度的影响规律 ,发现当约束机架上不含驱动单元的主侧面时 ,主模块的刚度最大 ,并且主模块用于立式机床时 ,其刚度远优于用于卧式机床 ;最后 ,分析总结了机床位于工作空间不同位置时的刚度变化规律 .该成果为并联机床主模块的设计提供了重要的理论指导 .  相似文献   

Relationship between skeletal muscle contractile properties and power production capacity in female Olympic rugby players     

Pedro L. Valenzuela  Zigor Montalvo  G. Sánchez-Martínez  Elaia Torrontegi  J. De La Calle-Herrero  R. Domínguez-castells 《European Journal of Sport Science》2018,18(5):677-684

This study aimed to determine which contractile properties measured by tensiomyography (TMG) could better differentiate athletes with high- and low-power values, as well as to analyse the relationship between contractile properties and power production capacity. The contractile properties of the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL) of an Olympic women’s Rugby Sevens team (n?=?14) were analysed before a Wingate test in which their peak power output (PPO) was determined. Athletes were then divided into a high-power (HP) and a low-power (LP) group. HP presented an almost certainly higher PPO (9.8?±?0.3 vs. 8.9?±?0.4 W kg^?1, ES?=?3.00) than LP, as well as a very likely lower radial displacement (3.39?±?1.16 vs. 5.65?±?1.50?mm, ES?=?1.68) and velocity of deformation (0.08?±?0.02 vs. 0.13?±?0.03 mm ms^?1, ES?=?1.87) of the VL. A likely lower time of delay was observed in HP for all analysed muscles (ES?>?0.60). PPO was very largely related to the radial displacement (r?=??0.75, 90% CI?=??0.90 to ?0.44) and velocity of deformation (r?=??0.70, 90% CI?=??0.87 to ?0.34) of the VL. A large correlation was found between PPO and the time of delay of the VL (r?=??0.61, 90% CI?=??0.84 to ?0.22). No correlations were found for the contractile properties of RF or VM. These results highlight the importance of VL contractile properties (but not so much those of RF and VM) for maximal power production and suggest TMG as a practical technique for its evaluation.  相似文献   

Analysis on stiffness and damping performance of active magnetic bearing system     

Wang Xiping Yu Liang 《上海大学学报(英文版)》1998,2(3):221-225

１ＩｎｔｒｏｄｕｃｔｉｏｎＴｏｈａｖｅｐｒｏｐｅｒｓｔｉｆｎｅｓｓａｎｄｄａｍｐｉｎｇｉｓａｎｅｓｓｅｎｔｉａｌｃｏｎｄｉｔｉｏｎｆｏｒａｎａｃｔｉｖｅｍａｇｎｅｔｉｃｂｅａｒｉｎｇｓｙｓｔｅｍｔｏｗｏｒｋｎｏｒｍａｌｙ．Ｔｈｅｓｔｉｆｎｅｓｓｏｆａ...  相似文献   

宝兴大厦地震反应分析     

石立彬  陈清军 《科技成果管理与研究》2008,(7):95-97

文章采用SATWEI和ETABS等软件对宝兴大厦进行内力分析,获得有价值的地震响应参数,从而了解扭转效应,即对于部分框支剪力墙结构,当转换层层高较大时,转换层以上结构抗侧刚度由最大层间位移角控制。  相似文献   

Sprint running: how changes in step frequency affect running mechanics and leg spring behaviour at maximal speed     

Andrea Monte  Valentina Muollo  Francesca Nardello 《Journal of sports sciences》2017,35(4):339-345

The purpose of this study was to investigate the changes in selected biomechanical variables in 80-m maximal sprint runs while imposing changes in step frequency (SF) and to investigate if these adaptations differ based on gender and training level. A total of 40 athletes (10 elite men and 10 women, 10 intermediate men and 10 women) participated in this study; they were requested to perform 5 trials at maximal running speed (RS): at the self-selected frequency (SF_s) and at SF ±15% and ±30%SF_s. Contact time (CT) and flight time (FT) as well as step length (SL) decreased with increasing SF, while k_vert increased with it. At SF_s, k_leg was the lowest (a 20% decrease at ±30%SF_s), while RS was the largest (a 12% decrease at ±30%SF_s). Only small changes (1.5%) in maximal vertical force (F_max) were observed as a function of SF, but maximum leg spring compression (ΔL) was largest at SF_s and decreased by about 25% at ±30%SF_s. Significant differences in F_max, Δy, k_leg and k_vert were observed as a function of skill and gender (P < 0.001). Our results indicate that RS is optimised at SF_s and that, while k_vert follows the changes in SF, k_leg is lowest at SF_s.  相似文献   

The influence of golf shaft stiffness on grip and clubhead kinematics     

Sasho J. MacKenzie  Daniel E. Boucher 《Journal of sports sciences》2017,35(2):105-111

The purpose of this study was to investigate the influence of shaft stiffness on grip and clubhead kinematics. Two driver shafts with disparate levels of stiffness, but very similar inertial properties, were tested by 33 golfers representing a range of abilities. Shaft deflection data as well as grip and clubhead kinematics were collected from 14 swings, with each shaft, for each golfer using an optical motion capture system. The more flexible shaft (R-Flex) demonstrated a higher contribution to clubhead speed from shaft deflection dynamics (P < .001), but was also associated with significantly less grip angular velocity at impact (P = .001), resulting in no significant difference in clubhead speed (P = .14). However, at the individual level, half of the participants demonstrated a significant difference in clubhead speed between shafts. The more flexible shaft was also associated with significantly different magnitudes of head rotation relative to the grip. More specifically, both bend loft (P < .001) and bend lie (P < .001) were greater for the R-Flex shaft, while bend close (P = .017) was greater for the stiffer (X-Flex) shaft. However, changes in grip orientation resulted in no significant differences in face orientation, between the shafts, at impact.  相似文献   

The effect of core training on distal limb performance during ballistic strike manoeuvres     

Benjamin Lee 《Journal of sports sciences》2017,35(18):1768-1780

Ballistic limb motion is enabled by proximal “core” stiffness. However, controversy exists regarding the best method of training this characteristic. This study sought to determine the most effective core training method to enhance distal limb athleticism. A total of 12 participants (24 ± 3 years, 1.8 ± 0.05 m, 76.8 ± 9.7 kg) consisting of Muay Thai athletes performed a core training protocol (Isometric vs. Dynamic, with Control) for 6 weeks, using a repeated measures design to assess performance (peak strike velocity, peak impact force, muscular activation) in various strikes. Isometric training increased impact force in Jab (554.4 ± 70.1 N), Cross (1895.2 ± 203.1 N), Combo (616.8 ± 54.9 N), and Knee (1240.0 ± 89.1 N) trials (P < 0.05). Dynamic training increased strike velocity in Jab (1.3 ± 0.2 m · s^?1), Cross (5.5 ± 0.9 m · s^?1), Combo (0.7 ± 0.1, 2.8 ± 0.3 m · s^?1), and Knee (3.2 ± 0.3 m · s^?1) trials (P < 0.05). Isometric training increased Combo impact force 935.1 ± 100.3 N greater than Dynamic and 931.6 ± 108.5 N more than Control (P < 0.05). Dynamic training increased Jab strike velocity 1.3 ± 0.1 m · s^?1 greater than Isometric and 0.8 ± 0.1 m · s^?1 more than Control (P < 0.05). It appears that both static and dynamic approaches to core training are needed to enhance both velocity and force in distal limbs.  相似文献