混凝土工程孔洞及漏筋原因分析及处理技术

结合工程实例,针对混凝土工程孔洞、漏筋问题,进行原因分析,并制定了针对性的治理措施,以减少或消除同类问题,使混凝土质量实现有效控制。     

Automatic measurement and warning of tension force reduction in a PT tendon using eddy current sensing

Post-tensioning (PT) using a bundle of pre-stressed strands is a critical process for assembling pre-fabricated and modularized bridge members. However, the tension force gradually diminishes over time due to such factors as corrosion, creep, and steel relaxation. Such changes compromise the overall safety of such structures. In this study, an eddy-current-based tension-force-loss warning (EC-TFLW) technique is proposed to detect and warn automatically of excessive loss of tension force in a PT tendon. A ring-type eddy-current sensor (ECS) is mounted on the outer surface of a wedge holding a tendon, and the level of eddy current measured by the ECS is related to the tension force of the tendon. The advantages of the proposed technique include: (1) low power consumption, (2) low cost, (3) simple installation, and (4) automated warning. The performance of the proposed EC-TFLW technique was validated experimentally in a full-scale lab test of a 3.3-m long, 15.2-mm diameter, mono-strand tendon that was tensioned using a universal testing machine (from 20 to 180 kN). Statistical hypothesis testing using the chi-square distribution was applied to the measured eddy current signals, and if the decline in tension exceeded a certain level, a warning was sent out automatically.     

CFRP筋复合型锚具锚固性能研究

为解决碳纤维增强复合材料(CFRP)筋的锚固问题,研制了由粘结材料、金属筒、夹片和锚环组成的CFRP筋复合型锚具,并进行了夹片长度、金属筒长度、夹片夹持位置以及粘结材料对CFRP筋复合型锚具的锚固性能影响试验.结果表明:粘结材料、金属筒长度和夹片夹持位置均对锚固性能有较大影响;夹片的夹持位置应避免在金属筒两端,且宜使金属筒受压区长度小于受拉区长度;Lica-B型粘结材料锚固性能优于Lica-A型粘结材料;复合型锚具各组件协同工作性能良好,夹片与金属筒间无滑移产生;参数合理的该类复合型锚具可有效锚固直径为8 mm的CFRP筋.     

The Therapeutic Potential of Exosomes in Soft Tissue Repair and Regeneration

Soft tissue defects are common following trauma and tumor extirpation. These injuries can result in poor functional recovery and lead to a diminished quality of life. The healing of skin and muscle is a complex process that, at present, leads to incomplete recovery and scarring. Regenerative medicine may offer the opportunity to improve the healing process and functional outcomes. Barriers to regenerative strategies have included cost, regulatory hurdles, and the need for cell-based therapies. In recent years, exosomes, or extracellular vesicles, have gained tremendous attention in the field of soft tissue repair and regeneration. These nanosized extracellular particles (30–140 nm) can break the cellular boundaries, as well as facilitate intracellular signal delivery in various regenerative physiologic and pathologic processes. Existing studies have established the potential of exosomes in regenerating tendons, skeletal muscles, and peripheral nerves through different mechanisms, including promoting myogenesis, increasing tenocyte differentiation and enhancing neurite outgrowth, and the proliferation of Schwann cells. These exosomes can be stored for immediate use in the operating room, and can be produced cost efficiently. In this article, we critically review the current advances of exosomes in soft tissue (tendons, skeletal muscles, and peripheral nerves) healing. Additionally, new directions for clinical applications in the future will be discussed.     

筋腱断裂后张力腿平台-筋腱-立管耦合系统响应分析

以某张力腿平台为例,建立了张力腿平台-筋腱-立管耦合系统动力学分析模型,开展了多种工况和不同筋腱断裂状态下平台-筋腱-立管系统瞬态响应研究.结果 表明:筋腱断裂后,平台运动位移和绕Z轴转动角度变化较小,平台绕X、Y轴转动角度变化较大且发生高频波动,经过衰减后平台的运动频率与完整状态下保持一致;位于断裂筋腱对角线位置上的...     

The Effect of Age and Intrinsic Aerobic Exercise Capacity on the Expression of Inflammation and Remodeling Markers in Rat Achilles Tendons

Old age, adiposity, and metabolic disorders are known as risk factors for chronic tendinopathy, which is a common problem in both athletes and the general population. However, the importance of these influencing factors has not yet been well understood. This study investigated alterations in gene expression and histology of Achilles tendons of young (10 weeks) and old (100 weeks) rats bred for low (low capacity runners, LCR) and high (high capacity runners, HCR) intrinsic aerobic exercise capacity. In this rat model, LCR displayed a phenotype of reduced exercise capacity, higher body weight, and metabolic dysfunctions compared to HCR. We hypothesized that the risk factors for tendinopathy in old LCR could lead to more pronounced impairments in Achilles tendon tissue. In quantitative real-time PCR (qPCR), age-related downregulation of tenocyte markers e.g., tenomodulin, genes related to matrix modeling and remodeling (e.g., collagens, elastin, biglycan, fibronectin, tenascin C) as well as transforming growth factor beta 3 (Tgfb3) have been detected. Inflammation marker cyclooxygenase 2 (Cox2) was downregulated in old rats, while microsomal prostaglandin E synthase 2 (Ptges2) was upregulated in old HCR and old LCR. In all groups, interleukin 6 (Il6), interleukin 1 beta (Il1b), and tumor necrosis factor alpha (Tnfa) showed no significant alteration. In histological evaluation, tendons of old rats had fewer and more elongated tenocyte nuclei than young rats. Even though a higher content of glycosaminoglycans, a sign of degeneration, was found in old HCR and LCR, no further signs of tendinopathy were detectable in tendons of old rats by histological evaluation. Low intrinsic aerobic exercise capacity and the associated phenotype did not show significant effects on gene expression and tendon histology. These findings indicate that aging seems to play a prominent role in molecular and structural alterations of Achilles tendon tissue and suggests that other risk factors associated with intrinsic aerobic exercise capacity are less influential in this rat model.     

有粘结CFRP筋预应力损失计算

通过6根有粘结预应力CFRP筋混凝土梁的单调静力试验,结合系统查阅的国内外有关试验研究资料,对有粘结预应力CFRP筋混凝土梁中CFRP筋预应力损失的计算方法进行了研究,并提出了有关设计建议。     

玄武岩纤维筋的力学特性与破坏模式试验研究

玄武岩纤维筋预应力锚索的主体受力构件为BFRP筋,对BFRP筋的力学性质和破坏模式进行研究,可为BFRP筋预应力锚索在不同岩土工程对象中的应用提供参考和技术指导。研究表明：BFRP筋是一种典型的线弹性材料,极限荷载张拉破坏前筋材只存在线性应变,张拉过程中由于纵向拉伸下筋材环氧树脂基体传递剪力滞后使得BFRP筋具有自断口向两端发展的“灯笼状”破坏模式,极限荷载作用下BFRP筋聚集的弹性能瞬间释放,筋材发生脆性破坏,破坏前无明显征兆;相比于表面未粘砂的BFRP筋,表面粘砂的BFRP筋由于砂粒占据了筋材表面一定空间,导致其环氧树脂基体对玄武岩纤维的包裹程度降低,造成表面粘砂的BFRP筋强度稍低于表面未粘砂的BFRP筋。总的来看,尽管BFRP筋的抗拉强度较高,但其变形能力和抗剪切能力较弱,破坏前不存在屈服变形,单一手段的BFRP筋预应力锚索在动载或大变形能力的岩土锚固工程中适用性较差。     

义乌江连续梁桥长索单端张拉问题研究

立足于工程实际,通过理论计算分析了长索单端张拉的可行性,针对单端张拉对结构所产生的影响进行计算,为长索单端张拉在工程上的应用提供理论支持。另外通过现场试验,找出长索单端张拉过程中无法理想实现双控这一通病产生的原因,并为如何避免类似问题提出了建议。     

预应力AFRP筋混凝土梁受弯承载力有限元分析

介绍了FRP筋的种类、基本性质及其名义屈服应力,并通过具体实例,运用ADINA软件对预应力AFRP混凝土简支梁进行了非线性有限元分析,并给出了有关的设计和应用建议。