内置复材约束的T形截面钢管混凝土组合柱轴压力学性能试验研究

内置复材约束的T形截面钢管混凝土组合柱(T-section concrete filled steel and GFRP tubular composite column,T-SCFC)包括外部钢管、夹层混凝土、玻璃纤维增强树脂复合材料(Glass fiber reinforced polymer,GFRP)管和核心混凝土。对14根不同截面形式的约束混凝土短柱和3组内置不同复材管壁厚的T形截面钢管混凝土组合柱进行轴压试验,对比分析了方钢管混凝土短柱(Square concrete filled steel tube,CFST)、复材管约束混凝土短柱(Concrete filled GFRP tube,CFFT)、内置复材约束方钢管混凝土短柱(Steelconcrete-GFRP-concrete tube,SCFC)和T-SCFC柱在轴压荷载作用下的力学性能。建立与试件同尺寸的有限元模型,并开展数值参数分析,研究不同钢管壁厚和核心混凝土强度对T-SCFC柱轴心受压性能的影响。结果表明：内置约束复材管可以明显提高方钢管混凝土短柱的受压性能,显著延缓SCFC短柱在轴压荷载作用下的钢材屈服和...     

新型CFRP-UHPC组合管混凝土圆柱轴压性能

为研究超高性能混凝土(UHPC)管替代碳纤维增强聚合物(CFRP)-钢管混凝土组合柱中钢管的可行性,提出一种外部缠绕CFRP的UHPC预制管、内部现浇填充普通混凝土的新型CFRP-UHPC组合管混凝土(Concrete-filled CFRP-UHPC tube,CFFUT)柱。对10个CFFUT圆柱(包含2个对比柱)进行了单调轴压试验,研究了UHPC管壁厚度、CFRP环向包裹层数和核心混凝土强度等的影响规律。结果表明：CFRP-UHPC管可以有效提高组合柱的承载力、变形能力和延性;CFFUT圆柱破坏形态为核心混凝土压溃、UHPC管开裂和CFRP拉断,破坏后整体性较好,属延性破坏模式;CFFUT圆柱的极限承载力与UHPC管壁厚度、CFRP层数和核心混凝土强度呈正相关;延性系数随UHPC管壁厚度、CFRP层数增加而提高,随核心混凝土强度增加先提高后降低。揭示了CFFUT柱的界面增强作用机制,CFFUT柱极限承载力与同等截面普通混凝土柱相比提高93.9%～203.5%,且CFFUT柱极限承载力一定程度上与CFRP-钢管混凝土柱相当。建立了CFFUT圆柱轴压极限承载力理论计算模型,并通过有限...     

GFWRP管增强混凝土柱的轴压泊松比

为完善和发展GFWRP管增强混凝土柱的设计与计算理论,设计并制备了不同管径、壁厚及缠绕角的GWFRP管混凝土柱试件。进行了轴心压缩试验并对试验结果回归分析,得到GFWRP管混凝土柱轴心压缩过程中转折点及峰值点的泊松比变化方程和相应的应变预测公式,得到组合结构轴压全过程的泊松比变化预测方程。可由给定的组分材料性能预测组合构件的极限泊松比和极限应变,达到预测实际工程中GFWRP管混凝土柱抗力与变形性能的目的。通过试验及计算结果对GFWRP管混凝土与传统钢管混凝土的泊松比变化趋势进行了对比分析,发现两者变化规律完全不同。进一步探讨了GFWRP约束管的纤维缠绕角对组合结构轴压泊松比的影响。结果表明,纤维缠绕角与轴压泊松比近似成反比关系。为制定合理的GFWRP复合材料增强混凝土柱规范提供了理论依据。      

锻后身管壁厚方向力学性能变化实验研究

目的 针对传统身管材料30SiMn2MoVA,研究精锻工艺和热处理工艺对身管壁厚方向力学性能的影响。方法 采用线切割方式沿身管内表层、中间层和外表层分层取样,通过拉伸实验和胀形实验,分别获取身管材料经精锻成形工艺后壁厚方向纵向力学性能和横向力学性能的变化规律,同时获得残余应力对锻后身管壁厚方向力学性能的影响。结果 身管毛坯壁厚方向各层材料力学性能基本相同,精锻后内表层材料强度性能明显高于中间层和外表层,外表层和中间层伸长率要高于内表层;去应力后,身管材料强度性能和伸长率基本得到恢复,但横向伸长率恢复不明显。结论 精锻工艺对身管材料内表层的强度性能提升最大,同时塑性消耗也最大,锻后热处理工艺能使身管强度性能得到恢复,提高身管材料的纵向伸长率。     

CFRP圆钢管混凝土中长柱轴压承载力研究

该文在钢管混凝土柱研究的基础上,进一步探究碳纤维布(CFRP)对圆钢管混凝土中长柱轴压承载力极限的影响.制作10根不同CFRP圆钢管混凝土中长柱进行轴压试验,探讨CFRP圆钢管混凝土中长柱的受力过程、破坏形态和轴压极限承载力,分析CFRP层数、混凝土强度、钢管壁厚与长细比对其极限承载力的影响,为CFRP圆钢管混凝土中长...     

内高压成形波节管承载特性分析

内高压成形波节管作为目前应用最广换热设备,其变形特点以及成形后承载特性均备受关注.本文通过数值模拟和实验研究的方法,首先分析波节管内高压成形壁厚分布规律、成形精度以及残余应力分布情况,然后分析成形后波节管在承载时,典型区域应力应变分布情况,得出波节管在承受不同载荷时的变形特点.研究结果表明:在内高压成形过程,当整形压力为290 MPa时,成形精度较好,根部过渡区域减薄率达21.63%,且此处残余应力最大.在承载过程,当波节管承受内压力自由胀形时,波节管等效应力的最大值出现在波节根部过渡区域,此处为承载的薄弱区域;当波节管承受轴向压缩和拉伸载荷时,波峰及其附近区域与之对应的产生轴向拉应变和轴向压应变,体现出波节管具备很好的轴向位移补偿能力.     

高压玻璃钢井下管的技术特点及应用

高压玻璃钢井下管可替代油田上的钢管用于油管、套管等领域,本文主要从产品的工艺特点,产品特点及实际应用情况等方面对高压玻璃钢井下管掌行了介绍,并认为高压玻璃钢井下管是一种很有前途的产品,值得在油田上大力推广。     

复合材料在身管火炮中的使用研究

复合材料在各种武器装备中得到了越来越广泛的应用，其中之一就是在身管火炮炮身方面的应用。根据复合材料圆筒结构静态刚强度和动态特性分析的理论模型，综合考虑其刚强度和动态特性的要求，通过改变复合材料圆筒中材料的缠绕角、缠绕顺序和采用T300和S2复合材料混杂等形式来研究复合材料圆筒中材料的有效使用，得出了基于厚度和角度优化的方式较为有效的结论。     

内爆炸载荷下双层钢管结构的动力响应

采用实验与数值模拟相结合的方法研究了双层钢管结构在内爆炸载荷作用下的动力响应。考察了内外层钢管的壁厚设置与炸药质量对结构变形失效模式及其抗爆性能的影响。结果表明:与外管壁厚相比,内管壁厚对结构变形失效模式起主导作用,随着炸药质量的增加,内管壁厚对结构变形的影响逐渐减弱;并且内管壁厚的改变显著影响结构的能量分配机制,增加炸药质量时,外管能量耗散增幅大于内管。     

纤维缠绕玻璃钢三通管的研究

本文分析了中间为偏心球体的玻璃钢三通管缠绕规律,给出了纤维在臂-球-臂缠绕时架空高度计算式。文中分别讨论了三通管的测地线和非测地线缠绕,指出用单一线型进行测地线缠绕时,在柄-球交接处存在一微小三角空白区,需要进行补强,本文还推导了丝嘴平面运动时的运动方程,讨论了避免芯模与丝嘴碰撞的条件,为在价廉的计算机控制的简单缠绕机上实现中间为偏心球体的玻璃钢三通的缠绕提供了依据。      

基于Ansys Workbench的快装箱多目标优化设计

目的研究快装箱在压力作用下的静态特性,并对其结构进行多目标优化设计。方法通过Ansys Workbench建立快装箱的几何模型和有限元模型,对快装箱进行静态分析。以快装箱的各箱板厚度和各钢边厚度为设计变量,以快装箱的质量、最大变形量和最大等效应力为目标函数建立多目标优化的数学模型,对快装箱进行多目标优化设计,并且分析对比优化前后的结果。结果通过分析获得的优化前后快装箱的箱板厚度和钢边厚度都有所减小,在保证强度和刚度的条件下,使得总质量减少了9.018%。结论经分析快装箱的多目标优化设计是合理的,在满足使用要求的前提下,减少了总质量,节约了材料,降低了成本。     

硬质合金内衬的组合超高压筒体优化设计

研究了硬质合金内衬的多层组合超高压筒体的强度优化设计。以等强度理论为设计原则,建立了以各外层径比(外径与内径的比值)为变量,容器总径比为约束,弹性承压能力最大为目标的优化设计数学模型。应用Lagrange乘子法进行优化,得到了各层最优径比公式及最大内压公式。在此基础上,从叠加原理出发,推导了不同材料多层容器的层间缩套压力及过盈量的最优精确解。最后通过实际算例与分析表明,硬质合金内衬的组合容器需要更大的缩套压力,对于三层容器,中间层和内衬主要承担径向压应力,而外层主要承担周向拉应力。     

Strain aging on the yield strength to tensile strength ratio of UOE pipe

Strain aging of microalloyed steel pipe can occur at the relatively low temperatures associated with the pipe coating process and/or during long-term storage. A Box–Behnken statistical design was used to determine the significant strain aging variables that affect the longitudinal yield strength to tensile strength (Y/TS) ratio for three uncoated X70 UOE pipes. The strain aging variables examined include time, temperature, steel composition/microstructure (vis-a-vis the C/Nb ratio) and position through the pipe wall thickness. Metallographic and electron backscattered diffraction examinations were undertaken to determine the grain size and phase percentages of the as-received pipe steel. Both position in the pipe and the C/Nb ratio were found to have a statistically significant effect on the yield strength to tensile strength ratio.     

Optimum detailed design of reinforced concrete frames using genetic algorithms

This article presents the application of the genetic algorithm to the optimum detailed design of reinforced concrete frames based on Indian Standard specifications. The objective function is the total cost of the frame which includes the cost of concrete, formwork and reinforcing steel for individual members of the frame. In order for the optimum design to be directly constructible without any further modifications, aspects such as available standard reinforcement bar diameters, spacing requirements of reinforcing bars, modular sizes of members, architectural requirements on member sizes and other practical requirements in addition to relevant codal provisions are incorporated into the optimum design model. The produced optimum design satisfies the strength, serviceability, ductility, durability and other constraints related to good design and detailing practice. The detailing of reinforcements in the beam members is carried out as a sub-level optimization problem. This strategy helps to reduce the size of the optimization problem and saves computational time. The proposed method is demonstrated through several example problems and the optimum results obtained are compared with those in the available literature. It is concluded that the proposed optimum design model can be adopted in design offices as it yields rational, reliable, economical, time-saving and practical designs.     

复杂载荷下钢带缠绕增强复合管力学特性

为研究海洋油气输送用钢带缠绕增强复合管在复杂载荷下的力学响应特性,考虑非线性接触,建立钢带缠绕增强复合管数值计算模型,研究由内外压、弯曲及拉伸载荷组合作用下钢带缠绕增强复合管的变形及承载性能.结果表明,压差(外压大于内压,≤2MPa)越大钢带缠绕增强复合管的柔性越高.与纯弯曲相比,拉伸载荷和压差的附加联合作用使钢带缠绕...     

玻璃纤维增强树脂复合材料管-钢筋/混凝土空心构件抗弯性能

为研究玻璃纤维增强树脂复合材料(GFRP)管-钢筋/混凝土空心构件的抗弯性能,编制了受弯构件的非线性分析程序,系统地分析了空心率、配筋率、GFRP管管壁厚度及混凝土强度等级等主要参数对其抗弯性能的影响,并通过试验对所编制的程序进行验证,最后建立适用于GFRP管-钢筋/混凝土空心构件的抗弯承载力计算公式。结果表明:利用编制的受弯构件非线性分析程序与建立的抗弯承载力公式,计算结果与试验结果均吻合较好,抗弯承载力随空心率的减小、配筋率的提高、GFRP管管壁厚度的增加及混凝土强度的增大而增加,空心率对构件抗弯承载力影响最大,其次是配筋率和GFRP管管壁厚度,最后是混凝土强度等级,空心部分半径比在0.25~0.5为宜,可以适当提高配筋率、GFRP管管壁厚度或混凝土强度等级来弥补该空心构件抗弯承载力,研究结论可为该结构在实际应用中提供参考依据。      

钢筋混凝土结构的应力拓扑优化方法研究

基于预测混凝土失效行为的Drucker-Prager(D-P)屈服准则,研究了进行钢筋混凝土结构配筋设计的应力拓扑优化方法。结合扩展的双材料密度惩罚模型,优化问题构造为以单元人工密度为设计变量、混凝土材料Drucker-Prager屈服函数为约束条件的钢筋用量最小化问题。为合理定义混凝土应力并防止应力奇异解现象,采用局部应力插值模型和ε-松弛方法对混凝土应力约束条件进行处理。推导约束函数的伴随法灵敏度计算公式,运用基于梯度的连续性优化算法求解优化问题。数值算例验证了所提优化模型的正确性及数值算法的有效性,并通过与传统最小柔顺性拓扑优化结果的比较,说明了该文方法能够充分利用混凝土的抗压能力和钢筋的抗拉能力,设计结果更为实用。     

Design optimization of cold-formed steel portal frames taking into account the effect of building topology

Cold-formed steel portal frames are a popular form of construction for low-rise commercial, light industrial and agricultural buildings with spans of up to 20 m. In this article, a real-coded genetic algorithm is described that is used to minimize the cost of the main frame of such buildings. The key decision variables considered in this proposed algorithm consist of both the spacing and pitch of the frame as continuous variables, as well as the discrete section sizes. A routine taking the structural analysis and frame design for cold-formed steel sections is embedded into a genetic algorithm. The results show that the real-coded genetic algorithm handles effectively the mixture of design variables, with high robustness and consistency in achieving the optimum solution. All wind load combinations according to Australian code are considered in this research. Results for frames with knee braces are also included, for which the optimization achieved even larger savings in cost.     

Thermoeconomic optimization of a single effect water/LiBr vapour absorption refrigeration system

In this paper, the thermoeconomic theory is applied to the economic optimization of a single effect water/LiBr vapour absorption refrigeration system for air-conditioning application, aimed at minimizing its overall operation and amortization cost. The mathematical and numerical techniques based optimization of thermal system is not always possible due to plant complexities. Therefore, a simplified cost minimization methodology is applied to evaluate the economic costs of all the internal flows and products of the system by formulating exergoeconomic cost equations. Once these costs are determined, the system is thermoeconomically evaluated to identify the effects of design variables on costs and enables to suggest values of design variables that would make the overall system cost effective. Finally, an approximate optimum design configuration is obtained by means of sequential local optimization of the system, carried out unit by unit. The result compares this optimum with the base case and shows percentage variations in the system's operation and amortization cost.     

Experimental Investigation of Bond Stress and Deformations in LWAC Ties Reinforced with GFRP Bars

The structures' durability is an engineering concern for a long time but has been increased in the last years. Lightweight aggregate concrete (LWAC) combined with glass fibre reinforced polymer bars allows to create structures with high performance in terms of durability. The glass fibre reinforced polymer (GFRP) bars have different ribs from those of steel bars, and consequently, its bond to concrete is affected. Moreover, the Young's modulus of GFRP is much below compared with that of steel, and this influences significantly the behaviour of structural elements reinforced with this material. This paper presents an experimental study focused on bond between LWAC and reinforcing bars of GFRP. Thirty‐six pull‐out tests were carried out using steel and GFRP bars. These reinforcements were combined with three types of concrete, all with the same design density 1900 kg m^?3 but with different values of compressive strength: 35, 55 and 70 MPa. Furthermore, 12 reinforced ties were tested, combining different types of bars (steel and GFRP), two different diameters (12 and 16 mm) and the three types of LWAC. Based on experimental results, several relations were established to understand the behaviour of LWAC structures reinforced with GFRP bars, mainly in the serviceability conditions. These results point out that ties deformation and crack width are very affected by the reduced Young's modulus of GFRP: deformations and crack width of ties reinforced with GFRP are significantly higher, approximately three times greater, compared with those of ties reinforced with steel. The tension stiffening effect was also analysed in detail, and it was found that it is slightly influenced by the concrete compressive strength but is highly dependent of the Young's modulus of the reinforcing material.