焊接残余应力对钢结构性能的影响作用研究

钢结构件在冷热焊接加工的过程中不可避免地会存在焊接残余应力,焊接残余应力可影响到钢结构构件的使用寿命,对钢结构结构刚度、疲劳强度、应力腐蚀开裂、焊件稳定性、低温工作性能、结构变形等性能均有着较大的负面影响,因此在实际工程中,应采取恰当的残余应力控制及消除技术,最大限度地减少残余应力,以提高钢结构的安全性。

钢结构焊接残余应力对结构性能的影响研究

在现代工业应用当中,钢结构以其优良的特性得到了广泛应用,但是焊接时产生的残余应力会对结构性能以及安全产生一定的影响。研究目的是深入探究焊接残余应力在钢结构性能中的作用,采用文献综述与数据分析相结合的方法揭示残余应力产生机制,影响因素以及对结构性能具体作用规律。利用盲孔法及其他残余应力检测技术分析焊接参数,材料特性及焊接工艺等因素对残余应力分布规律的影响。研究表明:残余应力水平及其分布不均度显着影响结构的刚度,疲劳强度,承载能力及疲劳寿命。另外还讨论了热处理,振动时效及其他应力释放方法对钢结构整体性能的影响,并对如何通过焊接工艺参数的优化及应力释放技术对钢结构残余应力进行控制进行研究。结论指出:合理的工艺设计及有效的控制残余应力可显著改善钢结构性能及安全性,对钢结构工程发展有一定的理论与实践意义。

高性能结构钢材与钢结构体系研究与应用

城乡建设领域的绿色发展和"十四五规划"对高性能结构材料、结构构件及结构体系的低碳、节能、环保提出了更高要求。对高性能结构钢材(包括高强钢、耐候钢、耐火钢、抗震耐蚀耐火钢)的基本特征和高温力学特性进行了分类和梳理,对高性能钢材基本构件及其连接的高温承载性能研究现状进行了总结和分析,对基于高性能钢材的建筑和桥梁结构体系发展趋势和应用前景进行了展望,对基于高性能钢材的组合结构体系研究提出了相关建议。

焊接残余应力对钢结构疲劳性能影响研究

焊接残余应力在钢结构热冷焊接过程中是不可避免的。焊接残余应力影响钢结构的寿命,对钢结构的结构刚度、疲劳强度、应力腐蚀开裂、焊接施工稳定性、低温运行性能、结构变形等产生重大负面影响。因此,在实际工作中,应采用适当的控制和消除残余应力的技术,以减少残余应力并提高钢结构的安全性。

高性能建筑结构用钢组织性能和强化机理研究

为了研究工业化大生产中的高性能建筑结构用钢的性能稳定性控制机理,使用拉伸试验机、光学显微镜、扫描电镜、透射电镜等设备并结合热力学计算,对高性能建筑结构用钢进行了组织性能、析出规律、强化机制系统研究。研究结果表明,试验钢的显微组织基本上由铁素体和珠光体组成,薄规格珠光体体积分数大于厚规格,铁素体晶粒尺寸、珠光体片层间距小于厚规格。析出物尺寸大部分集中在0~15 nm范围内,其中超过50%的析出物尺寸在5~10 nm范围内,薄规格的析出物尺寸、晶界角度均小于厚规格。强度贡献大小为细晶强化>析出强化>位错强化>固溶强化>晶格点阵强化,其中细晶强化及沉淀强化的强化效果最显著,对强度的贡献超过50%,对于不同厚度钢板而言,细晶强化、位错强化的差别较大。

钢桁架受力性能理论分析与试验研究

为使钢桁架结构能够安全、经济以及合理的应用在建筑工程中,本文从试验的方案、试验数据整理、内力的理论计算以及两组数据的对比等方面来探讨将焊接点看作为理想铰接点时,钢桁架结构受力性能的情况,以及其他因素对钢桁架结构受力性能的影响.

可在线涂装的“碳纤维/钢”复合结构汽车B柱分总成的研发

为提高汽车安全性和轻量化水平,开发了一种可在线涂装的“碳纤维/钢”复合结构B柱分总成,该分总成包括钢制B柱加强板和碳纤维增强复合材料(CFRP)B柱中部支撑板,采用结构胶粘接而成。研究了真空袋压与热压罐成型工艺对CFRP层压板涂装前后性能的影响,并对“碳纤维/钢”的粘接强度、B柱分总成的刚度和强度等力学性能进行了研究,结果表明,复合结构B柱分总成在涂装前后的性能均优于传统钢制总成,CFRP中部支撑板减重64.1%。

长庆油田地面建设钢结构设计阶段工程造价控制

建筑钢结构的经济性能一直是油田地面建设中最受关注的问题之一,工期和成本的互悖性在一定程度上制约了油田产建中钢结构的推广应用。为了设计阶段有效的控制工程造价,提高地面建设建筑经济性能是关键所在。本文在西安长庆科技工程有限责任公司油田地面建设设计门式刚架轻钢结构厂房以及多、高层钢结构建筑的设计逐渐应用基础上,对建筑钢结构的材料选用、结构体系优化等方面进行了分析,对油田工艺水处理间、注水泵房、输油泵房的基础及彩钢部分按照建安工程费、平方米造价等技术经济指标进行了对比分析,探讨了设计阶段控制钢结构工程造价的可行性。

长庆油田地面建设钢结构设计的工程造价控制

建筑钢结构的经济性能一直是油田地面建设最为关注的问题之一，工期和成本的互悖性在一定程度上制约了油田地面建设中钢结构的推广应用。为了在设计阶段有效地控制工程造价。本文在油田地面建设门式刚架轻钢结构厂房以及多、高层钢结构建筑的设计应用基础上。对建筑钢结构的材料选用、结构体系优化等方面进行了分析，对油田工艺水处理间、注水泵房、输油泵房的基础及彩钢部分按照建安工程费、平方米造价等技术经济指标进行了对比分析，探讨了设计阶段控制钢结构工程造价的可行性。

高性能钢结构建筑结构全寿命周期“三元一体化”指标体系研究

建立高性能钢结构建筑结构的全寿命周期结构性能、经济性和绿色可持续发展"三元一体化"指标体系,其中结构性能指标包括设计阶段的初始可靠度指标、时间指标、施工阶段指标、运营维护阶段指标及拆除阶段指标;经济性指标包括全寿命周期各阶段花费成本;绿色可持续指标包括资源利用、环境保护以及社会发展三方面。分析"三元"指标的"一体化"关系,提出各指标体系之间的联系与影响。以某商业综合体钢结构工程为例,验证所述指标体系在实际工程优化中的可行性与有效性。案例表明,该指标体系能够全面反应高性能钢结构建筑的高性能特征,对其全寿命周期分析与评估具有重要指导意义。在"三元一体化"视角下,提出高性能钢结构的设计建议。

Microstructure and mechanical properties of dissimilar resistance spot welded DP1000–QP1180 steel sheets

In this study,the effect of welding parameters on the microstructure and mechanical properties of the dissimilar resistance spot welded DP1000–QP1180 joints was investigated.Heat affected zone(HAZ)width of QP1180 side was smaller than that of DP1000 side.HAZ width and indentation depth increased with increasing welding current and welding time.The nugget size increased with increasing welding current whereas it increased at lower currents and decreased at higher currents with increasing welding time.The lowest hardness was on the DP1000 side.On the QP1180 side,the center of HAZ had the peak hardness.With increasing welding current,hardness values throughout the weld zone decreased and the tensile shear load increased.At lower welding currents,the welding time did not affect the tensile shear load.Tensile elongation decreased with the increase of welding time,whereas there is no relationship between the welding current and elongation.The spot-welded joints having higher strength exhibited a more ductile fracture characteristic.

Electrical resistance stability of high content carbon fiber reinforced cement composite

The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50 °C, increases relatively by 4% when ambient temperature decreases from 15 °C to ?20 °C, and decreases relatively by 13% with temperature increasing by 88 °C. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.

Physical and chemical performances of high Al steels

The effects of acid-soluble Al content on the physical and chemical performances of high Al steels were investigated. The results show that the distribution of acid-soluble Al in steel substrate is uniform. With increasing Al content, the strength and toughness of steels decrease a little but the hardness increases. The average yield strength and tensile strength are 425MPa and 570MPa, respectively, and the Rockwell hardness is 89.7. For non-Al steels the average oxidation rate is up to 0.421mg/(cm2·h) at 1373K. For high Al steels, when the mass fraction of Al is less than 5%, there is a thinner gray oxidized layer on surface and the oxidation rate is high; when the mass fraction of Al is more than 8.0%, the thin, close and yellow glossing film still exists, and the average oxidation rate is only 0.016mg/(cm2·h).

Experimental Study on Seismic Performance of Tall Building with Steel Transfer Trusses Located at a Higher Level

Based on a shaking table experiment of 1 :25 scale frame-shearwall structure model with steel transfer trusses,the dynamic characteristics,seismic responses in elastic and elastic-plastic phases with de- structive forms of the structure were studied.It was observed that cracks were developed with earthquake wave acceleration increasing,but no severe crack was developed in the structure during the experiment.In the seismic responses caused by artificial wave,site wave and E1 Centro wave,that caused by the artificial wave is the most intense one.Displacement angle between steel transfer trusses is large,which means the transfer stories might be weak.However,the seismic performance of the steel transfer trusses is good and the overall structure can satisfy seismic fortification requirements in the region of intensity 6.

Action of Runaway Electron Preionized Diffuse Discharges on Steel： Composition, Structure, and Properties

In the work, we studied the effect of the plasma of a runaway electron preionized （REP） diffuse discharge （DD） on the composition, structure, and properties of ST3PS steel surface layers. Voltage pulses with an incident wave amplitude of up to 30 kV, FWHM of around 4 ns, and rise time of around 2.5 ns were applied to the gap in an inhomogeneous electric field. The ST3PS steel specimens exposed to this type of discharge revealed changes in their defect subsystem, suggesting that the runaway electron preionized diffuse discharge provides surface hardening of the steel.

The Effect of Vanadium Content on Mechanical Properties and Structure of Self-Hardening Steel X 160C rMo 12-1

The aim of this research was to examine the influence of vanadium on the structure, hardness and tensile strength of X I60CrMo 12-1 self-hardened steels. It is known that vanadium affects the process of solidification of this alloy in a way that narrows temperature interval of crystallization. Vanadium, as an alloying element, moves liquidus and solidus lines toward higher temperatures, approximately for 25 to 30 ~C. In addition, vanadium forms V6C5 carbides, which, are partly distributed between present phases in the steel; carbide （Cr,Fe）7C3 and austenite. The presence of vanadium enables the formation of （Cr, Fe）23C6 carbide and its precipitation into austenite during the cooling process. In local areas around fine carbide particles, austenite is transformed into martensite, i.e., vanadium reduces remained austenite and improves steel air-hardening. Vanadium concentration over 2.5% significantly improves the impact toughness. The basic problem in the application of high alloyed Cr-Mo steels is to increase their impact toughness and thereby sustain a relatively high value of hardness. Recent studies, concerning to the chemical composition and heat treatment regime, show that it is possible to get a martensitic structure with a very small amount of retained austenite. Investigations are directed toward the testing of the influence of alloying elements such as molybdenum, manganese and especially vanadium. Vanadium has great influence to the crystallization process. With increasing of its content, the eutectic point moves toward lower carbon concentrations and the temperature interval of solidification is narrowing.

Study on the Structural Performance of Steel Plate Shear Wall with Slits on Both Sides

This paper presents a new type of two sides slotted steel plate shear wall, and carries on the analysis to the finite element elastic buckling, respectively discusses the critical buckling load and the buckling mode. For the steel plate shear wall without stiffening ribs on both sides, the paper given the buckling coefficient formula, and give design proposal and reference value of steel plate shear wall with stiffened on both sides.

Structural Behavior of Repaired Reinforced Concrete Beams with Glued Steel Plate and Carbon Fiber

This paper investigates the strength and deformation characteristics of reinforced normal and high-strength concrete rectangular beams which failed in shear and repaired by external bonding of carbon fiber and steel plate. Five simply supported reinforced concrete beams with shear reinforcement are tested, three of which are made with NSC （normal-strength concrete） and the other two with HSC （high-strength concrete）. The span of the simply supported beams is 0.9 m with 100 mm wide by 200 mm deep cross section. All five beams are tested under four-point bending. Careful repair process is adopted and proved successful. The aim is to restore or increase shear strength of these beams and to monitor their post-repair load-deflection behavior. The effect of concrete compressive strength on the behavior and strength of beams before and after repair is also investigated. Shear cracks patterns and their evolution are observed and discussed.

Assessment of the Seismic Behavior of the Reinforced Concrete Structures Based on the Probabilities

This paper presents an analytical foundation for probability-based formats for seismic design and assessment of structures. These formats are designed to be suitable for code and guideline implementation. The framework rests on non-linear, static seismic analysis. The formats can be used to ensure that the structural seismic design can be expected to satisfy specified probabilistic performance objectives, and perhaps （more novel） that it does so with a desired, guaranteed degree of confidence. Performance objectives are presumed to be expressed as the annual probability of exceeding a structural performance level. Structural performance levels are in turn defined as specified structural parameters （e.g., ductility, strength, maximum drift ratio, etc.） reaching a structural limit state （e.g. onset of yield, collapse, etc.）. The degree of confidence in meeting the specified performance objective may be quantified through the upper confidence bound on the （uncertain） probability. In order to make such statements, aleatory （random） uncertainty and epistemic （knowledge limited） uncertainty must be distinguished. The single seismic design foundation can be formatted into the alternative conventional design methods such as LRFD design and fragility-hazard design. Versions of the new developments reported here are already in place in recently completed seismic guidelines.

Flexural Behavior of FRP-Reinforced Concrete Composite Member

Concrete Filled FRP （Reinforced Polymeric Plastic） Tubes （CFFT） and Reinforced Concrete Filled FRP Tubes （RCFFT） are known to have the capability to enhance structural performance in terms of structural stability, ductility, as well as chemical resistance when compared with conventional concrete members. In this study, the authors evaluate the structural performance of the CFFT and the RCFFT through flexural tests for the purpose of applying the members as flexural ones. Moreover, the compressive behavior of the CFFT and the RCFFT members was investigated to examine their confinement effects. Based on the experimental and analytical results of the compressive behavior of the members, equations for estimating the ultimate compressive strengths of the CFFT and the RCFFT were proposed. In addition, the degree of improvement on the flexural performance of the RCFFT member strengthened by the FRP was analyzed from the flexural tests.