Strengthening of Interior Slab–Column Connections Using a Combination of FRP Sheets and Steel Bolts

The results of an experimental investigation undertaken to evaluate a new technique for strengthening interior slab–column connection in combined flexural and shear modes are presented. The technique consists of using a combination of shear bolts inserted into holes and prestressed against the concrete surface for improving the punching shear capacity, and external [fiber-reinforced polymer (FRP)] reinforcement bonded to the tension face of the slabs in two perpendicular directions for increasing the flexural strength of the slabs. Square slab specimens of 670×670?mm dimensions were tested and the main test variables included the ratio of steel reinforcement (1.0 and 1.5%), span–depth ratio or thickness (55 and 75?mm) of the slabs, area, and configuration of steel bolts, and area of FRP reinforcement. It was found that the use of shear bolts alone improves the punching shear strength and increases the ductility of failure by changing the failure mode from punching to flexural. However, the use of a combination of shear bolts and a moderate amount of FRP reinforcement increased the flexural strength and resulted in a substantial improvement of the punching shear capacity of the slabs. The corresponding increases attained levels between 34 and 77%. A design approach is presented for evaluating the ultimate capacity of the slab–column connections when strengthened using the proposed strengthening technique. Strength results predicted by the proposed approach were in good agreement with the experimental results.     

Numerical Modeling of Bolted Lap Joint Behavior

Nonlinear finite-element models are developed that predict the load-elongation behavior of conical-head bolted lap joints, and the load-elongation predictions are compared with experimental test data. The study is conducted for several panel thicknesses with three fastener sizes and three panel materials. The model load-elongation predictions are in excellent agreement with experimental test data. Model parameters, such as part discretization, material model selection, sliding interface friction coefficients, and convergence tolerances, are discussed. A means of inducing clamp in the joint is also developed. The results show that nonlinear finite-element analysis may reliably predict the behavior of conical-head bolted joints.     

基于RFID技术的风电塔筒螺栓松动智能检测系统

针对传统检测风电塔筒螺栓松动程度时容易出现过检、漏检的问题,文中提出设计用于辅助检测的基于物联网技术的风电塔筒螺栓松动智能检测系统。该系统为监测紧固螺栓用液压扳手的液压泵工作状态,改造液压扳手将液压泵压力表改为带变送器的压力传感器,将物联网中感知层传感器射频识别(Radio Frequency Identification,RFID)读卡器用于设计该系统的检测目标识别电路。由于安装RFID标签时涉及设备改造,文中运用ANSYS软件对改造后风电塔筒螺栓受力情况进行分析,给出了安全的改造方案。并设计过检、漏检报警电路来辅助检测风电塔筒螺栓松动情况。该系统中还设计了大容量SD卡存储电路,将运检结果保存于SD卡中,方便读取、分析检测结果。实际应用表明,使用该系统可以杜绝漏检情况的发生,减少过检情况的出现,提高螺栓松动检测效率。     

Behaviour of Grade 8.8 bolts under natural fire conditions—Tests and model

Recent full-scale experimental tests performed on steel and composite structures have demonstrated that the presence of tensile forces in axially-restrained beams during the cooling phase of a fire could lead to bolt failures. In order to understand this observation and design structures that are not prone to such a failure mode, it is essential to have a deep knowledge of the material behaviour of all the components, including bolts, during both the heating and cooling phase.In the present article, the test set-ups and the results of the tensile and shear tests performed at the Centro Sviluppo Materiali (Italy) on Grade 8.8 bolts under heating-cooling cycles are described.Then, material laws are defined for characterising the mechanical behaviour of Grade 8.8 bolts under heating and cooling phases. These laws account for the non-reversibility of the mechanical properties of Grade 8.8 bolts.     

太原一电厂六期锅炉柱脚固定新方案的确立和实施

太原一电厂１３号锅炉柱脚施工中,采用了取消埋设地脚螺栓的定位方法,缩短了工期,提高了效益,取得良好效果。     

Performance of a Nongasketed Flange Joint under Combined Internal Pressure and Bending Loading

Performance of a bolted flange joint is characterized mainly due to its “strength” and “sealing capability.” A number of analytical and experimental studies have been conducted to study these characteristics only under internal pressure loading. A very limited amount of work is found in the literature under combined internal pressure and bending loading. Due to the ignorance of this external loading, i.e., bending loading, the optimized performance of the bolted flange joint cannot be achieved. The present design codes do not address the effects of bending loading on the structural integrity and sealing ability. To investigate joint strength and sealing capability under combined loading, an extensive comparative experimental and numerical study of a nongasketed flange joint is carried out and overall joint performance and behavior is discussed. Actual joint load capacity is determined under both the design and proof test pressure with maximum additional external bending loading that can be applied for safe joint performance. In addition, as experimentally it is impossible to test different flange joint sizes under combined loading application, hence finite element model developed and verified with the experimental results, presented in this paper can be used as base to study the behavior for different nongasketed flange joint sizes for different classes under combined pressure and bending loading.     

承力框螺栓断裂分析与改进设计探讨

针对某型飞机第二交点框框缘下部 3个螺栓在全机疲劳试验中出现疲劳断裂情况 ,从该框接头区的结构形式、连接支臂与框缘螺栓受力特点、全机疲劳试验情况出发 ,对螺栓断裂的原因进行了分析 ,并根据分析结果探讨了该螺栓的改进方案     

液压拉伸器的使用与维护

液压拉伸器是一种先进的螺栓预紧和拆卸工具，已广泛用于大直径螺栓的预紧，文中给出了液压拉伸器的正确使用与维护方法。     

某型起重机操纵室螺栓装配顺序优化设计

在某型起重机操纵室装配过程中,其顶部玻璃极易开裂.经过调查发现:由于安装螺栓支座与安装平台存在较大间隙,且两者之间为刚性连接,导致在螺栓拧紧过程中,顶部玻璃产生较大的装配应力致其开裂.在不增加制造成本的前提下,采用有限元结构刚度分析方法,对比分析4种螺栓安装顺序方案对操纵室顶部玻璃内应力的影响,给出最优的装配顺序方案,降低顶部玻璃装配内应力,解决玻璃装配开裂问题.     

紧固件在复杂载荷下的疲劳强度可靠性设计

针对迈因纳定理在解决紧固件疲劳强度可靠性中存在的问题，提出了一种紧固件在复杂载荷作用时，疲劳强度可靠性设计的方法．