索承式桥梁吊索钢丝腐蚀疲劳寿命评估

根据吊索镀锌钢丝腐蚀疲劳破坏特点，把镀锌钢丝腐蚀疲劳纹形成和扩展过程分解成镀锌层腐蚀失效、蚀坑萌生、蚀坑形成、短裂纹扩展、长裂纹扩展和断裂破坏等阶段，建立各阶段时间表达式，得到镀锌钢丝疲劳寿命表达式，提出基于断裂力学的吊索钢丝腐蚀疲劳寿命评估研究结果方法。通过算例分析复杂运营条件下腐蚀环境和应力幅等因素对吊索钢丝腐蚀疲劳寿命的影响，研究结果表明：吊索钢丝腐蚀疲劳寿命主要由钢丝镀锌层腐蚀、蚀坑发展和短裂纹扩展等3个阶段组成，为了准确地评估吊索腐蚀疲劳寿命，需要掌握大桥的运营环境和交通荷载。     

EFFECT OF HIGH LOADS IN THE BRIDGE LOAD SPECTRUM ON FATIGUE CRACK GROWTH OF 16 Mn STEEL

This paper studies an effect of high loads in Rayleigh distribution random load-ing on fatigue crack growth wi th 16 Mn steel compact tenion specimen,The results show that thehigh loads in the load spectrum close to service load of steel bridges accelerate crack growth and re-duce crack growth life,Lives predicted with constant amplitude da/dn data and equivalent loads arequite in agreement with test lives.     

THE DETERMINATION OF A CRACK IN STEEL FIBRE REINFORCED LIME-SAND CONCRETE

This paper studies the determination of a crack in steel fibre reinforced lime-sand concrete and its precision by acoustic emission(AE).The main AE paramters which influencethe precision of the determination of a crack are introduced,The properties of the lime-sand concretecan be increasted greatly with the steel fibre,The result in this paper can be used in the study of fi-bre re inforced cement concrete.     

A FRACTURE MECHANICS ANALYSIS OF FRACTURE PLANE CONTROL IN FRACTURE CONTROL BLASTING

A procedure of fracture control blasting for achieving directional breaking of rocks by blasting is presented. The criterion for initiating of radial cracks in borehole wall under dynamic load and the method for determining the permissible rang of initial gas pressure (p0) in the charge cavity are developed .and the branching of radial cracks and the effeets of the pressure (p0) and blasthole geometry (R0.a.L3) on final dimensions of directed cracks are studied .with Fracture Mechanics analysis in all three aspects of fracture process including crack initiation .crack propagation and crack arrest.     

A STUDY ON FRACTURE MECHANICS OF BRITTLE MATERIAL WITH PER-CRACKS

In this paper the fracture process of specimen,with single crack, double cracks and triple cracks is observed and analysed. The experimental results show that the fracture process of specimen is different because of the differention of the number, the distance and the type of array of cracks. And the fracture propagation of specimen with triple cracks and double cracks is foundmentally the same.     

Experimental Investigation and Finite Element Analysis on the Hysteretic Behavior of New Steel Beam-to-Column Connections

By the hysteretic experiments and the finite element analysis of the proof-of-concept connections, the mechanical properties and energy dissipation capacity of the new steel beam-to-column connections are investigated. These connections are semi-rigid ones improved by adding threaded rods into the angle connections and can be designed to limit the structural damage only to the angles and threaded rods. It is found, by the comparative analysis of six connections tested with the same loading sequence, that the performance degradation of the connections may be resulted from the plastic damage, crack propagation of the angles and the buckling and fatigue crack of the rods. The rotation capacity and failure modes of the connections with threaded rods depend on the ability of anti-fatigue crack of the rods, and the better ductility the rods have, the better energy dissipation capacity the connections have. In addition, the hysteretic behavior and the deformation modes of the connections prior to the significant strength degradation or the fracture of the rods could be well simulated by the finite element method. Meanwhile, the stiffening effect from pre-stressing the angles, the plastic distribution of the angles and the degradation induced by the rod buckling were strongly verified by the FEA. Finally, the advantages and disadvantages of such new beam-to-column dissipative connections were analyzed, and the proposal for further connection improvement and in-depth study was made.     

The Changes of Underskined Interal Crack of Continuous Casting Billet During Piercing Process

This article studies on the distributional law of underskined internal crack in steel billets of continuous casting billet in additon to the appearance and features of the outer cross crack and outer fold which result from the internal crack during the piercing process.     

Experimental Analysis of Cracking Behavior of ConcreteBeams Reinforced with High Strength Bars

Eight concrete beams reinforced with 500MPa steel bars and four reinforced with 400MPa ultra fine grain steel bars were tested under two point symmetrical concentrated static loading to observe the details of crack pattern development on these beams and investigate their cracking characteristics. It was shown that the cracking behavior of the beams with high strength bars was essentially similar to that of common RC flexural members, whereas the computed crack widths using the formula adopted in the Code for Design of Concrete Structures GB 50010 2002 exceeded that of the experiment under the normal service. Furthermore, the formulas for crack spacing and crack width specified in GB 50010 2002 were evaluated through the experimental results and previous studies of sixty seven concrete beams reinforced with high strength bars. On the basis of the calculation model in GB 50010 2002, revised formulas for crack spacing and crack width were proposed. The values calculated by revised formulas were in good agreement with the test results.     

Study Of Three-Point Bending Marble Beam Elastoplastic Damage

An elastoplastic damage constitutive model based on incremental theory is deduced in strain space.A mesoscopic numerical model to study the progressive failure process and the nonlinear mechanical behavior of heterogeneous rock is established in combination with an elastoplastic damage constitutive for rock mesoscopic element.The failure elements deleting method is used to simulate crack propagation in program.The calculation results achieved by numerical simulation and practical projects application agree well with those of in-situ tests,which illuminates that elastoplastic damage mesoscopic model could reflect local plastic characteristics of fractured rock masses.Three-dimension marble model is more reflect mesoscopic failure than two-dimension model.The failure element deleting method is good at showing explicitly crack propagation.It is proven that the numerical model is right and feasible.The failure elements deleting method solves the difficult problem of FEM to simulate the propagation.The model and method might be valid in practical projects.     

Effect of Reinforcement Beam Sticking Different Layers Steel

This paper constituted the FEM(finite element method) model of sticky steel reinforcement beam and the model was used to analyze the reinforcement effect of the beam sticking different layers'' steel plate. The result shows two layers of steel is better than others, which agrees with theoretic analysis. It illuminate that the FEM model is in point for sticky steel reinforcement beam without crack.     

CFRP筋钢筋混凝土剪力墙自复位性能试验研究

通过对1片钢筋混凝土剪力墙和4片配有碳纤维增强聚合物(CFRP)筋的剪力墙的低周反复荷载试验,在分析试验中测得的裂缝宽度、裂缝的发展和分布形态、侧向变形的基础上,研究了在钢筋混凝土剪力墙的适当位置部分或全部配置CFRP筋对剪力墙的残余裂缝和残余变形等自复位性能的影响规律。研究结果表明:与普通钢筋混凝土剪力墙相比,配有CFRP筋的剪力墙的开裂荷载较低,裂缝较多,裂缝分布分布范围较广,墙体的最大裂缝宽度、残余裂缝宽度和侧向残余变形分别降低了60%、70%和90%,说明在剪力墙中合理配置CFRP筋能使剪力墙具有优异的自复位性能。     

THE THEORETICAL DERIVATION FOR C-M FORMUJA

Form the crack propagation rate and the cyclic stress-strain respon- dence of low cycle fatigue, the C-M formula is theoretically derived by using the correcting factor. The constants in this formula are also estimaled and discussed.     

Concrete with a Crack Treated by Silane Soakage

If a crack appears in marine or concrete structures due to chloride corrosion, it will be a convenient channel for the chloride to penetrate into the concrete and easily corrode the steel bars and damage the concrete. A concrete specimen with a 0.2mm wide crack was prepared. After the specimen was soaked in a silane solution, emulsion and gel, a chloride ion corrosion test was carried out. The analysis of two dimensional chloride content shows that the silane soakage treatment of cracked concrete seals the crack and prevents further corrosion.     

Experimental Analysis for Steel Box Concrete Composite Beam of Arch Bridge

A new steel concrete composite structure was proposed which composed of steel box beam, PC beam and PBH Shear connection. Bend test was carried out for the performance study of deformation and stress. It was found that Material advantages of steel and concrete were fully used and crack of concrete and local instability of steel box were avoided. And the deformation between steel box and concrete can be smoothed with PBH shear connection. As the calculated values showed good agreements with the test results, the proposed formulas can be reliably applied to the practice analysis. With the different parameters analysis, mechanic performance of the composite was obtained.     

Experimental analysis of strengthening effect of corroded reinforced concrete beams strengthened with bolted steel plates

In order to study the mechanical behavior of corroded reinforced concrete beams strengthened with bolted steel plates, this paper designed 12 reinforced concrete beams. These beams were corroded by using accelerated electrochemical corrosion method with a designed corrosion ratio of 10%. The pre-compression experiments were performed for all RC beams before strengthening and the maximum crack width was controlled as 0.2 mm. According to the thickness of concrete cover, the beams were divided into 3 groups. Each group was composed of one comparative beam and three tested beams strengthened by steel plates bolted with study according to the thickness of steel plates which were 3 mm, 4 mm and 5 mm, respectively. It was shown that the strain distributions along the height of the strengthened beams at middle-span were in good agreement with the plain section assumption basically. The serviceability performances of corroded RC beams were significantly improved and these ultimate bearing capacities increased obviously. The steel plate bolted with stud effectively reduced the crack width and the extension height of reinforced concrete beams. It was indicated that an increase of steel plates with 35 mm resulted in a decrease of deflection by 13%51% when beams had the same thickness of concrete cover and corrosion ratio. Influence of the thickness of concrete cover on the ultimate bearing capacity was not obvious.     

Application of Fracture Mechanics in Explosion of Large Iron and Steel Wastes

The ex plosio n process a n d paramete rs in the blast of large iron a nd steel wastesare analysed by using the theory of fracture mechanice.A three-dimensional model is established us-ing pressurised cylinder with multiple semi-elliptical surface cracks.Reasons are given for the expla-nation that the dynamic fracture toughness for iron and steel is generally lower than the correspond-ing static value during the blast.The importance is emphasized of the critical duration time of the dy-namic stress intensity factor for crack extension.     

Temperature-DifferentiaI Drawing of Austenite Stainless Steel

A temperature-differential drawing process is adopted on the basis of structuredeformation characteristics of austenite stainless steel.With this process,the degree of strainhardening,can be effectively controlled.aging crack be prevented and drawing limit be enhanced,thus the number of drawing operations can be reduced.and intermediate annealing and picklingoperations be eliminated. Therefore,an economic benifit is prominent.     

稻谷吸湿裂纹生成与扩展的机理分析

当前对KUNZE湿应力模式的分析有两种模式：一种是基于最大拉应力与裂纹形成的高度相关性,一种则是从吸湿裂纹敏感性与谷粒中存在的微裂纹大小的相关性考虑,两种机制各有适用之处。研究了两种裂纹生成机制随吸湿时间的变化规律,并分析了不同热力学条件下垩白对裂纹生成与扩展的影响,结果表明：稻谷吸湿过程的前期,拉应力机制处于主导裂纹生成的地位,吸湿后期,微裂纹机制处于主导地位,两者间存在一个过渡阶段,在过渡阶段,所有影响因素的作用均会被削弱。     

STABILITY FACTORS OF THREE-POINT BEND ROUND BEAM SPECIMENS FOR FRACTURE TESTING

Crack growth stability is very important for fracture toughness testing of brittle materials. The width of crack for a three-point bend round beam specimen changes continuously during the process of crack extension, so that the analysis of crack growth stability becomes complicated for this kind of specimen. This paper presents a method for calculating its stability factors, and the results of the calculation are compared with those of other specimens.     

EFFECT OF SEMI-RIGID CONNECTIONS ON BEHAVIOR OF STEEL FRAME

Modeling of girder in steel frame with semi-rigid conn-ections as partially restrained beam element is proposed for elastic-plasticanalysis of steel frames with semi-rigid connections.The results whichare obtained from analyses of elasticity,plasticity and stability for steelframes with semi-rigid connections have significant effects on structuralbehavior.It is necessary to consider the influences of semi-rigid conn-ections on the analysis and design for steel frames.