共查询到20条相似文献，搜索用时 703 毫秒
1.
Sheng Guangmin Gong Shihong Zhu Jinfu 《保鲜与加工》1989,(2):67-72
In this paper, the strain fatigue: crack propagation rates of vanadium bearing HSLA steel with different micro-structures are measured under constant load conditions, and the relationship between the crack propagation rate and the microstructures of steel is also studied. 相似文献
2.
The internal force would vary largely with different load ratio for steel arches under combined full-span with half-span loads. However, most relevant formulas on in-plane stability capacity of steel arches were obtained by studying the stability under a single load. Thus, it lacks full considerations of the applicability of bearing capacity formulas under a combined full-span load with half-span load. To overcome this shortcoming, the two-hinged parabolic steel arch was used to compare the results of bearing capacity of arches with different load ratios, rise-span ratios and sections calculated by several methods, The method proposed in the current Chinese design specification of steel arch structure and the finite element method based on the perfect arch and the consistent imperfect arch were included. The results showed that the method in the specification for designing a steel arch would be conservative with a large ratio of the full-span load to the total loads while unsafe with a large ratio of the half-span load to the total loads. 相似文献
3.
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。 相似文献
4.
5.
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. 相似文献
6.
When steel plate-masonry composite structure used in the existing masonry structure with load bearing walls is removed for a large space, composite action should be considered between the beam and the supported masonry wall due to the arch effect formed in the supported wall. In order to investigate the working mechanism, failure mode, and load-carrying capacity, strain distribution in critical sections and mid-span defcection of this type of composite wall-beam, five steel plate-masonry wall-beams were tested under concentrated loads and analyzed, which considered variables of height-span-ratio of supported masonry wall, height-span-ratio of composite beam and thickness of steel plate. The results show that steel plate-masonry composite wall-beam starts failure from the masonry located at the line between loading point and supporting point; strain distribution of steel plate along section height meets the plane section assumption; the height-span-ratio of supported wall can directly influence the failure mode of masonry wall, buckling load corresponding to steel plate experiencing local buckling and ultimate load of tested specimens; the reasonable height of supported masonry wall is beneficial to the formation of composite action between supported masonry wall and composite beam, and the excessive high masonry wall will reduce the ultimate load of the tested specimen. Finally, the reasonable range for height-span-ratio of supported masonry wall was presented, and the proposed value representing the flexural stiffness of the steel plate-composite beam relative to the in-plane stiffness of the supported masonry wall was at least more than 79. 相似文献
7.
Liu Xiaoqiang Wu Huibi 《保鲜与加工》1993,(2)
Displacement of stress-resultants computation technique of semi-rigidly connected steel frames inclucing stiffness matrix method,hand calculation method has been proposed. Hand calculation includes substitute rigid frame method under horizontal loads and moment distribution or decomposed storey method under vertical loads. Connection stiffness for five widely used type has systematically computed and practical values of beam stiffness to column stiffness has been summarized and issued. 相似文献
8.
棉株载铃量对其主要生育性状的影响 总被引：4，自引：0，他引：4
采用 熟性不同 的３ 个陆 地棉 品种 ,在 肥水 充 足的 生 长条 件下 ,研 究了 棉 株不 同载 铃 量对其主要 生育性状 的影响 。结果表 明, 棉株 载铃 量 对株 高、果枝 总长 、果 节总 数均 有 极强 的 影响 ,其影响强 度随载 铃量的增 加而增加 ,累积 影 响量 随棉 株 生长 发 育时 间的 延 长而 增大 ;但 棉株 载 铃量对主茎 节数、果 节平均长 度影响 不显 著。 由此 分析 了 蕾铃 脱 落和 棉株 旺 长之 间的 关 系,以 及 棉株在一定 地力条 件下适宜 的单株载 铃量。 相似文献
9.
以竖向荷载和水平地震作用组合下的钢筋混凝土柱和钢柱为对象,研究了失效方程中荷载相关特性对柱承载力抗震可靠性的影响。根据现行《混凝土结构设计规范》和《钢结构设计规范》分析了不同柱弯矩轴力相关曲线的特性。结合多个框架结构实例,对比了柱失效方程中荷载相关曲线与规范考虑情形的异同。实例分析表明:水平地震和竖向荷载组合作用下,小偏压RC柱和工字型钢柱的荷载相关曲线与规范考虑的情形较为符合,均近似为负相关的直线;水平地震和竖向荷载组合作用下,大偏压RC柱的荷载相关曲线则与规范考虑的情形有较大出入,存在明显的正相关段部分。在此基础上,考虑失效方程复杂特性,依据已有的荷载和抗力变量概率模型,采用Monte Carlo法分析了水平地震和竖向荷载组合作用下柱的可靠性。结果表明:钢柱和小偏压RC柱的承载力抗震可靠度随轴压力荷载效应比值的变化幅度较小,与规范模式计算结果较接近;大偏压RC柱的承载力抗震可靠度随轴压力荷载效应比值的变化会有较大幅度波动,与规范模式计算结果差异较大;当轴压力荷载效应比值为负时,大偏压RC柱的承载力抗震可靠度会低于规范计算值较多,现行柱可靠性设计方法会偏于不安全。 相似文献
10.
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. 相似文献
11.
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。 相似文献
12.
Wang Qizhi Xian Xuefu 《保鲜与加工》1992,(2):13-18
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. 相似文献
13.
Crack growth of drill pipe is a typical discontinuous problem. It is difficult to simulate with conventional finite element method and extended finite element method (XFEM) is developed in recent years for the problem. With the introduction of XFEM, the XFEM model of 5 inch drill pipe was proposed with different depth initial cracks under combined action between torque and tension. Based on the simulation, It is found that the smaller cracks is not easy to grow, whilst the crack of depth more than 2mm could grow under relatively lower external load and larger growth surface, eventually leads to pipe fracture failure. Through this simulation on crack growth of drill pipe, it is showed that the XFEM is appropriate in analysis of fracture failure. 相似文献
14.
Zhou Jiyue Zeng Qingyu 《保鲜与加工》1991,(3)
Through the static tests of five two-span continuous beams with a relatively small steel ratio, the regularity of redistribution of internal forces of continuous beams with moment modulation is studied, and the moment modulation influence on cracking and deflection of continuous reinforced concrete beams under service loads is analyzed in detail. The conclusions obtained may be used as reference materials for drafting of design code considering redistribution of internal forces. 相似文献
15.
By using mixed triangle series,this paper discusses the calculation of rectangular stiffened plates with simply supported edge along direction of stiffeners under several local loads,such as uniform load on local rectangular area,concentrated force,concentrated moment of couple,line loads,line moments of equal and some equivalent concentrated forces acting on a line with equaldistance among them.All analytical solutions of both displacements and internal forces are derived.A numerical example to treat an engineering problem is given. 相似文献
16.
In order to accurately evaluate the aseismic behavior of the seismic damaged masonry pagodas destroyed by Wenchuan earthquake and strengthened after the earthquake, a test was conducted to acquire related parameters on seismic performance from the specimens made by masonry and retrofitted with grouting and steel hoops. Taking a seismic damaged ancient masonry pagoda in Sichuan as a case study, four kinds of primitive specimens are fabricated by simulating the conformation of the masonry pagoda. Then the primitive specimens are destroyed under cycle loads and the damaged specimens are repaired by grouting and steel hoops. Cycle controlling tests are conducted with the specimens and relevant data are acquired. Experimental results showed that grouting combined with steel hoops could improve the ductility and energy dissipation capacity of a seismic damage of brick masonry structure, but it do a little to improve the stiffness of a seismic damage structure. And the cracking load of the repaired masonry is much lower than the original undamaged structure. 相似文献
17.
为了探究ECC/高强钢筋混凝土叠合梁的正截面受弯特征,以及ECC层厚度对叠合梁整体受弯性能的影响,做了两组共5根梁试件的正截面受弯试验。发现与高强钢筋混凝土梁相比,叠合梁的承载力更高,相同荷载下的挠度值和最大裂缝宽度较小。在受弯全过程中其截面应变仍符合平截面假定,钢筋与ECC也可以实现协调变形,说明受拉区使用ECC可以使得高强钢筋的应力得到充分发挥。但ECC层厚度过大可能会使叠合梁发生脆性破坏。进一步地,在此研究的基础上,对已有ECC的本构模型进行简化,忽略其应力强化贡献,并运用叠加原理,提出一种用于计算ECC/钢筋混凝土叠合梁正截面受弯承载力的方法,将计算结果与试验结果及诸多文献结果进行比较,发现吻合度较高。 相似文献
18.
Based on the strain energy considering the effect of dead loads, the general form static equilibrium differential equations were formulated by means of the potential energy principle. The approximate solutions of live load or later load displacement including the effect of dead loads for the clamped rectangular plate and the simply supported rectangular plate were generated by the Galerkin method. These formulas are simple and clear, and their physical concepts are explicit. The correctness of these formulas was verified by the finite element method. The dead loads and other factors that influence the effect of dead loads are shown by these formulas. The effect of dead loads on the two different boundary condition rectangular plate were analyzed by these approximate solutions. The effect of dead loads improves the bending stiffness of plate and minimizes the displacement of live loads or later loads. The key physical factors governing the effects of dead loads on plates are the dead load, the ration of span to thickness and boundary condition etc. This effect of dead loads is not negligible, especial in thinner plates or plates with smaller stiffness, more attention should be paid to the effect of dead load in the calculation and analysis for plates. 相似文献
19.
Analysis on Effect of Traffic Loads on Landslide Stability 总被引：1，自引：0，他引：1
In the design of landslide control engineering,the effect of traffic loads has not been taken into account.The authors simplified the traffic loads as mobile dead loads and traffic dynamic load.The mobile dead load ranges from 2.34 to 6.41 kPa.The impact coefficient was chosen to denote the traffic dynamic load and ranges from 0.1 to 0.4.Using several stability analysis methods widely accepted by engineers,combining two analysis samples,by the contrast of stability tests with and without consideration of the mobile dead load or the traffic dynamic load,the authors found that when the traffic load is not taken into account,the stability coefficient of shallow layer landslide(<8m) is overrated by 4.3-11 percent or 5.8-12.1 percent in comparison with the case when the mobile dead load or traffic dynamic is taken into account respectively,that is,the influence of mobile dead loads and traffic dynamic load is cannot be neglected.In case of medium deep layer landslide or the road is passing through the anti sliding section,the influence of the traffic load is a little and can be neglected. 相似文献
20.
Based on the elastic foundation beam,the control differential equation of tunnel lining is worked out,according to the theory of Saint-Venant,the predominance equation about the center angle to the crack space is established, then the crack space of tunnel lining under the loads can be worked out and according to the crack space,the crack width can be calculated. 相似文献