半刚性连接钢框架极限承载力分析

本文依据增量理论,采用钢结构高等分析方法中的等效假想荷载塑性铰法对钢框架结构进行二阶弹塑性极限承载力分析,通过对计算结果的分析比较表明精确分析框架结构在荷载作用下的性能时,应当考虑节点刚度的非线性和截面局部屈服对结构极限承载力的影响。     

基于神经网络的半刚性节点关键参数研究

介绍了框架结构的连接方法,分析了半刚性节点的研究现状及进展情况,针对目前框架结构的链接方法中存在的问题,以半刚性节点为研究对象,利用神经网络方法建立了粒子群RBF神经网络算法,按照节点聚类分析方法建立了神经网络算法的聚类分析并给出了其分析合理性评判标准.对节点模型初始转动刚度进行了预测分析,预测结果与实际结果较为接近,...     

碳纤维增强钢筋混凝土梁二次受弯承载力的试验研究

通过试验，本文对用碳纤维加固的二次受力钢筋砼梁的破坏特性、屈服弯矩、极限承载力、刚度等进行了研究与分析。     

轻钢与泡沫混凝土组合墙体抗剪承载力计算研究

通过试验研究了轻钢与泡沫混凝土组合墙体的力学性能.研究表明:泡沫混凝土密度、含钢率等参数,对组合墙体破坏形态并无影响,但组合墙体的抗剪承载力受泡沫混凝土密度、含钢率影响较大.本文结合相关轻钢结构规范及理论,提出了轻钢泡沫混凝土组合墙体抗剪承载力计算公式,其计算结果与试验结果吻合度较高.研究成果可为轻钢与泡沫混凝土组合墙...     

基于软化效应的型钢混凝土节点抗剪承载力计算

根据现有试验资料,对规范YB 9082—2006《钢骨混凝土结构技术规程》和JGJ 138—2016《组合结构设计规范》中型钢混凝土节点抗剪承载力计算公式进行计算,结果表明,规范计算结果偏于保守,且离散性较大,主要原因在于混凝土项取值过于简化,导致计算结果离散性大。基于软化效应,考虑主拉方向对主压方向强度的弱化影响,对混凝土强度、配箍率、型钢约束强度、轴压比等因素的影响进行量化分析,并提出抗剪承载力计算公式中混凝土项的修正公式,结果表明,所提公式可以合理考虑各因素的影响,提高计算结果的准确性并降低离散性。     

预应力高强混凝土矩形支护桩的受弯性能

针对预应力混凝土预制桩在基坑支护中的应用,开发新型的预应力高强混凝土矩形支护桩。通过9根矩形支护桩的受弯性能试验,研究了矩形支护桩的受弯破坏特征、裂缝开展情况和受弯承载力。结果表明:在外荷载作用下,矩形支护桩变形体现了很好的弹性和延性;矩形支护桩截面的应变分布符合平截面假定;矩形支护桩的抗裂弯矩实测值与计算值之比平均为1.33;实测极限弯矩与理论计算值基本接近。基于试验结果,提出对矩形支护桩抗裂弯矩和极限弯矩计算方法的修正建议,计算结果与试验结果吻合较好。对比发现,在相近的成本条件下,矩形支护桩比空心方桩受弯承载力增加10%～20%。     

双钢板-混凝土组合板爆炸后残余承载力试验研究

为探究双钢板-混凝土组合板(Steel-Concrete-Steel Composite Slab,简称SCS组合板)的抗爆后性能,进行了三块SCS组合板爆炸后的残余承载力测定试验.设计了一套可用于SCS组合板加载的试验装置,通过改变爆炸荷载大小及钢板填充物,探究二者对于SCS组合板残余承载力的影响;通过规范中提供的经...     

页岩陶粒混凝土梁的受弯承载力试验研究

通过对16根陶粒混凝土梁和1根普通混凝土梁进行了受弯对比试验,研究了钢筋和陶粒对混凝土梁受弯承载力的影响.结果表明:素陶粒混凝土梁的破坏是由两条贯穿裂缝引起的脆性破坏,其破坏机理是以陶粒破坏为主,破坏断面裂缝贯穿粗集料;混凝土梁的受弯承载力随着陶粒强度和钢筋配筋率的增加呈上升趋势;陶粒的粒径及级配、保护层厚度和钢筋的直径对混凝土梁的承载力也有一定影响.     

中欧钢结构规范受弯构件整体稳定性计算方法比较

结合我国钢结构设计规范(GB 50017—2003)及欧洲钢结构设计规范(EN1993-1-1:2005),从计算公式、临界弯距和整体稳定系数三方面,对两本规范的受弯构件整体稳定性计算方法进行了分析对比,并通过计算实例得到了两本规范之间的一些差异。     

轻钢与泡沫混凝土组合墙体抗剪承载力有限元分析

对轻钢与泡沫混凝土组合墙体应用于建筑结构进行推广,对6面组合墙体进行抗剪承载力试验,对其水平荷载峰值、开裂荷载、极限荷载、破坏形态进行测定,建立了轻钢与泡沫混凝土组合墙体ABAQUS有限元计算模型,有限元计算结果与试验结果吻合度较高,该模型可用于轻钢与泡沫混凝土组合墙体抗剪承载力的计算与分析。     

钢-混凝土组合梁纵向抗剪非线性分析

在钢混凝土组合梁中,栓钉传递的剪力作用在混凝土板上,当横向钢筋配筋率低于一定值时,混凝土板会发生纵向剪切破坏,从而会导致组合梁的极限承载力降低,不能充分发挥组合梁的优势。采用了ANSYS软件对组合梁进行了非线性有限元分析,并结合试验结果探讨了横向钢筋对组合梁极限受弯承载力的影响,同时对组合梁的挠度及滑移进行了分析。计算结果表明,为保证组合梁混凝土板不发生纵向抗剪破坏,横向钢筋配筋率应不小于0.6%,利用给出的模型可反映出栓钉对混凝土板的作用。     

循环软水变换气换热器膨胀节计算

结合原设备破坏的形式,提出直立、高耸设备膨胀节计算时必需考虑地震作用、风载荷与设备其他载荷组合作用,并重新进行了膨胀节合理设计。     

Processing and property of carbon-fiber aluminum-foam sandwich with aramid-fiber composite adhesive joints

Thin tissues (or called webs) of short aramid fibers were added at the adhesive joints between carbon-fiber face sheets and aluminum-foam core to form aramid-fiber ‘composite adhesive joints’ for improving the interfacial bonding strength of sandwich structures and therefore other structural properties. In-plane critical compression loads and failure modes of carbon-fiber aluminum-foam sandwich beams with short aramid-fiber composite adhesive joints are investigated and discussed in this study. Improvements in critical compression loads were achieved for all specimens with aramid-fiber composite adhesive joints of different densities. It is suggested that the composite adhesive joints using low-density short aramid fibers is effective in promoting reinforcements against cracking and delamination at the interface between carbon-fiber face sheets and aluminum-foam core. The underlying interfacial strengthening and toughening mechanisms were discussed and analyzed based on observations from optical image and scanning electron microscopy.     

Bending moment calculation for single lap joints with composite laminate adherends including bending-extensional coupling

This work deals with the analytical determination of section forces and moments in adhesively bonded single lap joints with composite laminate adherends including bending-extensional coupling. The analysis is also valid for unbalanced joints and the adhesive thickness is taken into account in the model. Several types of boundary conditions can be applied, e.g. simply supported ends, fixed ends, bonded doubler and single strap joints. Various configurations are studied and the results are compared to finite element analyses and other analytical approaches. Good agreement is achieved over a wide range of configurations. A closed form analytical solution is given for the section forces and moments at the overlap ends.     

A hybrid bondline concept for bonded composite joints

Based on the experience in the past and the occurrence of in-service damages, the authorities restrict today the application of adhesive bonding of composite structures for aircraft applications. However, certification limitations can be overcome if occurring disbonds within a bond are stopped by implemented design features, so-called disbond stopping features. Consequently, a novel bondline architecture for bonded composite joints is proposed. By implementing a distinct rather ductile thermoplastic phase, a physical barrier for growing disbonds is obtained and thus a fail-safe design, respectively. Moreover, the joint is established by using two different joining technologies, namely adhesive bonding and thermoset composite welding. A sophisticated manufacturing technique is developed for the hybrid bondline concept to achieve a high strength joint. The joint׳s quality is examined by means of several analytical methods like microsections, scanning electron microscopy (SEM), and energy-dispersive X-Ray (EDX) analysis. Additionally, the mechanical performance is evaluated by static Double Cantilever Beam (DCB) and Single Lap Shear (SLS) tests.     

MgO-SiC-C材料的抗渣性能研究

以电熔镁砂、碳化硅、鳞片石墨(w(C)>97%)、铝粉(≤0.088mm,w(Al)>98%)和硅粉(≤0.088mm,w(Si)>98%)为主要原料,按w(电熔镁砂)=81%,w(SiC)=10%,w(鳞片石墨)=4%,w(铝粉 硅粉)=5%的组成配料,以酚醛树脂为结合剂,压制成125mm×25mm×25mm的MgO-SiC-C试样,在220℃干燥24h后采用感应炉法进行了抗转炉终渣试验,并对抗渣试验后试样进行了XRD、SEM和EDAX分析。结果发现熔渣对MgO-SiC-C试样的侵蚀和渗透并不显著,试样的侵蚀速率为0.25~0.3mm·h-1;抗渣试验后试样原质层主要组成为MgO、SiC和MgO·Al2O3;在与熔渣接触后,SiC被氧化成SiO2,由此导致在试样和熔渣间形成一高粘度的液相反应层,有效地减轻了试样受熔渣渗透和侵蚀的程度,提高了试样的抗渣能力。     

The tension failure mechanisms of composite stepped bonding repairs and joints for the aircraft primary load-bearing structures

Stepped and scarf topology are still the preferred choices for repairs and joints of composite primary load-bearing structures. The stepped bonding scheme is easy to be implemented in real engineering process. The precise stress distribution, load capacity, damage mode and failure mechanism are not adequately clear. This paper adopts static stress analysis of FEM (Finite Element Method), experimental studies and CDM (Continuum Damage Mechanics) to reveal the tension failure mechanism for composite stepped bonding structures. In the static stress analysis, the mesoscale FEM model considered the adhesive thickness was created. It investigated the detail stress distribution and concentration of the step topology adhesive. Then seven specimens with tensile load were studied experimentally through relation of load-deformation and the appearance of damage. For more details, the adhesive damage was simulated by using CZM (Cohesive Zone Model) which includes the mix-mode fracture of normal force and sliding shear force. The process of damage propagation evolution can be clearly observed in the simulation results. The damage initiates at the vertical location of steps adhesive and propagates to the horizontal overlaps adhesive. Simulation for predicting the ultimate load capacity coincides with experiments. This paper’s work will be useful for designing and analyzing the full composite materials airframe and wing repaired by stepped bonding technique.     

Review on adhesive joints and their application in hybrid composite structures

Composites have been used extensively in various engineering applications including automotive, aerospace, and building industries. Hybrid composites made from two or more different reinforcements show enhanced mechanical properties required for advanced engineering applications. Several issues in composites were resolved during the last few years through the development of new materials, new methods and models for hybrid joints. Many components in automobile are joined together either by permanent or temporary fastener such as rivets, welding joint and adhesively bonded joints. Increasing use of bonded structures is envisaged for reducing fastener count and riveted joints and there by drastically reducing assembly cost. Adhesive bonding has been applied successfully in many technologies. In this paper, scientific work on adhesively bonded composites and hybrid composites are reviewed and discussed. Several parameters such as surface treatment, joint configuration, material properties, geometric parameters, failure modes, etc. that affect the performance of adhesive bonded joints are discussed. Environmental factors like pre-bond moisture and temperature, method of adhesive application are also cited in detail. A specific case of adhesive joints in hybrid bonded-bolted joints is elaborated. As new applications are expanding in the field of composites joining and adhesive joints, it is imperative to use information on multiple adhesives and their behaviour in different environmental conditions to develop improved adhesive joint structure in mechanical applications.     

Numerical stress analysis of carbon-fibre-reinforced epoxy composite single-lap joints

A numerical strategy based on a finite element method is developed in order to model the stress distribution in single-lap adhesive joints. The joints were manufactured from unidirectional carbon-fibre-reinforced epoxy composites joined by an epoxy adhesive layer. Experimental parameters are used as a reference to allow for the numerical validation of the proposed analysis. Additionally, joints with different types of defects in the lap region were modelled with both two-dimensional and three-dimensional finite elements. The models include defects that vary in format (straight or circular) and position (centred or dispersed). The influenced spew fillets in the adhesive layer were also examined. Although the computational cost is higher, the results of the three-dimensional model are more compatible with the experimental results than those of the two-dimensional model. The effect of defects in the joints was adequately modelled, and the proposed methodology can be used to accurately assess the integrity of the joints since the defect has been successfully detected.     

Corrosion resistance properties of electroless nickel composite coatings

Electroless nickel (EN) composite coatings incorporated with PTFE and/or SiC particles demonstrated significantly improved mechanical and tribological properties as well as low surface energy which are desired for anti-sticking and wear resistant applications. The corrosion resistance of these composite coatings, however, has not been systematically studied and compared. This work aimed to investigate the corrosion characteristics of EN composite coatings using electrochemical measurements which include open circuit potential (OCP), electrochemical impedance spectroscopy and potentiodynamic test. The effects of the co-deposited particles on corrosion behavior of the coatings in 1.0 N H₂SO₄ and 3% NaCl media were investigated. The surface autocatalytic properties and the post-heat-treatment on coating corrosion resistance were also discussed. The results showed that both EN and EN composite coatings demonstrated significant improvement of corrosion resistance in both acidic and salty atmosphere. Ni striking substantially enhanced the corrosion resistance due to the improvement of the surface autocatalytic properties and homogeneity. Proper post-heat-treatment significantly improves the coating density and structure, giving rise to enhanced corrosion resistance.