谈包裹预应力筋波纹管的固定技术改进

介绍了预应力混凝土的应用背景及性能要求,分析了有粘结预应力筋波纹管传统固定方式的不足之处,就波纹管的固定方式提出了改进措施,可供同类工程施工参考借鉴。     

Effect of Platelet-Rich Plasma and Bioactive Glass Powder for the Improvement of Rotator Cuff Tendon-to-Bone Healing in a Rabbit Model

To test the hypothesis that a platelet-rich plasma (PRP) plus bioactive glass (BG) mixture could shorten the tendon-bone healing process in rotator cuff tendon repair, thirty mature male New Zealand white rabbits were randomly divided into three groups, Control, PRP, and PRP + BG. All groups underwent a surgical procedure to establish a rotator cuff tendon healing model. Mechanical examinations and histological assays were taken to verify the adhesion of the tendon-bone. Real-time PCR was adopted to analyze Bone Morphogenetic Protein-2 (BMP-2). The maximum load-to-failure value in mechanical examinations was significantly higher in the PRP + BG group than that in the control group after six weeks (Control 38.73 ± 8.58, PRP 54.49 ± 8.72, PRP + BG 79.15 ± 7.62, p < 0.001), but it was not significantly different at 12 weeks (PRP 74.27 ± 7.74, PRP + BG 82.57 ± 6.63, p = 0.145). In histological assays, H&E (hematoxylin-eosin) staining showed that the interface between the tendon-bone integration was much sturdier in the PRP + BG group compared to the other two groups at each time point, and more ordered arranged tendon fibers can be seen at 12 weeks. At six weeks, the mRNA expression levels of BMP-2 in the PRP + BG group were higher than those in the other groups (PRP + BG 0.65 ± 0.11, PRP 2.284 ± 0.07, Control 0.12 ± 0.05, p < 0.05). However, there was no significant difference in the mRNA expression levels of BMP-2 among the three groups at 12 weeks (p = 0.922, 0.067, 0.056). BMP-2 levels in PRP and PRP+BG groups were significantly lower at 12 weeks compared to six weeks (p = 0.006, <0.001).We found that the PRP + BG mixture could enhance tendon-bone healing in rotator cuff tendon repair.     

玻璃酸钠注射治疗指屈肌腱狭窄性腱鞘炎的临床观察

目的观察腱鞘内注射玻璃酸钠治疗指屈肌腱狭窄性腱鞘炎的临床疗效。方法根据病情程度将20例、25指指屈肌腱狭窄性腱鞘炎分为Ⅰ～Ⅲ度,男5例,女15例,平均年龄23.6岁;拇指12指,示指2指,中指4指,环指6指,小指1指。均向指屈肌腱鞘内注射玻璃酸钠1个疗程,随访4～1 2月,平均随访6.5月。结果20例患者注射1针后症状明显缓解,疗程结束1周后19例症状完全消失,1例仍有轻度疼痛活动受限。结论玻璃酸钠治疗指屈肌腱腱鞘炎能取得很好的疗效。     

某办公楼的检测与加层改造设计

通过对某中学办公楼进行的现场检测和计算分析,确定该结构主要构件的强度,以加层后结构新增荷载的情况和检测所得结构主要承重构件的强度为依据,结合非承重构件的检测情况,对该办公楼进行了加固设计,对类似工程具有借鉴意义。     

污水处理厂卵形消化池无粘结预应力施工技术

北京小红门污水处理厂卵形消化池预应力工程施工中采取了以样板引路、用摩擦损失测试确定张拉控制数据、选择预应力筋张拉顺序等措施,降低了施工成本,保证了主体结构质量。     

Simulation of Corrosion Crack in Pretensioned Prestressed Concrete Members

Corrosion of PC tendon embedded in concrete deteriorates performance of PC （prestressed concrete） members. Corrosion crack observed in pretensioned PC members is different from that in reinforced concrete and post tensioned PC members. The purpose of this study is to clarify mechanisms of corrosion crack in pretensioned PC members. Contribution of compressive stress induced by prestressing force and arrangement of PC tendons on corrosion crack in pretensioned PC members is investigated through experiment and numerical analysis. Three dimensional finite element analyses were carried out to simulate corrosion crack in PC specimen. Based on the analytical and experimental results, the influencing factor of corrosion crack in pretensioned PC members is discussed. It was concluded that the contribution of compressive stress in concrete by prestressing force on corrosion crack is not significant and that the dominant reason for wider corrosion cracks in pretensioned PC members is the arrangement of PC tendons with small intervals.     

碳纤维复合材料筋在不同锚固填料中的锚固性能试验研究

为了分析对比不同锚固填料的锚固效果,需要寻求一种更好的粘结介质以提高CFRP筋粘结式锚具的锚固性能。本文主要针对环氧树脂型锚固填料,采用四种不同环氧型锚固填料,对不同长度和锥段倾角的锚具进行灌锚,并进行了静载拉伸试验研究。试验结果表明:1采用Lica型建筑粘结胶对CFRP筋进行锚固,锚固长度至少需要达到50倍筋材直径;2Wirelock在固化过程中发生了收缩,不可用于直筒型锚具,当锚具内壁有了3°锥角后,Wirelock可以锚固住碳纤维复合材料筋;3冷铸填料高温固化过程中容易导致筋材的强度下降至原有强度的78.87%左右;4环氧树脂砂浆用于锚固碳纤维复合材料筋材,锚固长度需要达到40倍筋材直径;5相同条件下,四种锚固胶在锚具内部的变形程度为Lica型建筑粘结胶最大,环氧树脂砂浆次之,然后是冷铸填料,Wirelock钢丝绳胶水的变形程度最小。     

Model predictive control for tendon‐driven balloon actuator on simulation

Many pneumatic actuators have been developed to be lightweight with high output for decreasing the impact force. However, for pneumatic actuators it is difficult to maintain exact control because these actuators have constraints. In this study, we developed model predictive control (MPC) that can accommodate these constraints when applied to the pneumatic actuator we developed. As described here, we compared and evaluated the control performance using MPC and proportional–integral–derivative (PID) control with an anti‐windup control system. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

预应力AFRP筋混凝土梁受弯性能的试验研究

对一组配置芳伦纤维增强塑料AFRP预应力筋的简支梁进行受弯试验,考察AFRP筋配筋率、张拉控制应力、非预应力钢筋配筋率等因素对构件承载能力的影响,分析了开裂荷载、极限荷载、荷载-挠度关系、裂缝发生发展、平截面假定、AFRP筋和普通钢筋的应变发展状况等。试验结果表明:有粘结预应力AFRP筋混凝土梁的受载全过程可分为三个阶段,即从加载到混凝土开裂,再到非预应力筋屈服,最终达到极限承载力;虽然AFRP筋材没有屈服点,但是其弹性模量较低,因此,试验梁破坏前有明显的变形和预兆;破坏时,AFRP筋应变不一定达到极限,其值可按平截面假定计算;此外,试验表明,适当提高张拉控制力能提高梁的极限承载能力。