钢筋混凝土梁弯曲刚度简捷计算

对《混凝土结构设计规范》ＧＢＪ１０－８９的受弯构件弯曲刚度公式进行推导化简，得出矩形截面梁的“短期刚度”和“长期刚度”的实用公式，可供设计参考使用。     

FRP加固钢筋混凝土梁实用刚度模型

为了解决正常使用荷载下FRP加固钢筋混凝土梁的变形预测问题,本文基于刚度解析法建立了该类构件的实用刚度解析模型,模型中引入了β和λ两个参数分别用以考虑FRP使受拉钢筋和受压混凝土变形减小从而对构件刚度的影响。然后利用该模型预测了加固构件的跨中挠度,并与实测结果进行了比较,两者之间吻合很好。研究表明,加固梁的刚度随FRP用量的增加而提高;所提出的刚度模型简单实用并具有较高的预测精度,可以作为工程设计的参考。     

钢纤维对钢筋混凝土梁弯曲韧性与疲劳损伤的影响

通过钢筋混凝土梁弯曲静载和等幅疲劳试验,研究了钢纤维对钢筋混凝土梁挠度、弯曲韧度、刚度以及刚度损伤累积的影响.结果表明:在弯曲静载试验中,梁的挠度随着钢纤维体积率的增加而逐渐减小,弯曲韧度逐渐增大;在疲劳试验中,各梁挠度增长和刚度损伤累积随着荷载循环次数增加均呈现三阶段变化规律,说明钢纤维掺入不会改变钢筋混凝土梁疲劳损伤发展规律,但会改变梁挠度和刚度的大小,随着纤维掺量增加,梁的挠度逐渐减小,刚度逐渐增加,抵抗变形能力增强.     

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。     

玄武岩纤维钢筋混凝土梁弯曲性能试验研究

通过玄武岩纤维钢筋混凝土梁四点弯曲试验,分析其破坏形态和破坏机理.通过四点对称加载方式研究不同玄武岩纤维掺量下梁的承载力、挠度、韧性、混凝土应变、钢筋应变等变化规律.试验结果表明:玄武岩纤维掺入对钢筋混凝土梁的开裂荷载和极限荷载都有一定的提高,开裂荷载最大提高幅度为32％,极限荷载最大提高幅度为6.5％.与普通钢筋混凝土梁相比玄武岩纤维钢筋混凝土梁的挠度、韧性均有所提高.玄武岩纤维对梁的受压区混凝土具有阻止裂缝扩展的能力,当梁上部受压区混凝土被压碎时,混凝土碎块会在纤维的桥接作用下不剥落,梁仍保持较好的整体性.     

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。     

格构腹板式界面增强泡桐木夹芯复合材料梁的弯曲性能试验

复合材料及其夹层结构具有轻质高强、耐腐蚀、节能保温等特点,以玻璃纤维增强复合材料作为面层和格构腹板,以泡桐木为芯材,采用真空导入成型工艺,制备出格构腹板式界面增加泡桐木夹芯复合材料梁。在保持试件总尺寸不变条件下,对木梁、无格构木芯梁、格构木芯梁进行了平面、侧面四点受弯性能试验研究对比。得出如下结论:同一种构造试件平面受压时所受的极限承载力和刚度比侧面受压时所受的极限承载力和刚度高;无格构木芯梁、格构木芯梁试件所受的极限承载力和刚度比木梁试件所受的极限承载力和刚度有明显的提高;格构木芯梁试件所受的极限承载力和刚度比无格构木芯梁试件所受的极限承载力和刚度有一定的提高。     

轮胎断面弯曲刚度分布研究

针对轮胎产品普遍存在的变形过大,特别是胎侧段的屈挠变形过大问题,提出轮胎断面弯曲刚度的概念,研究弯曲刚度的影响因素,得出不同胶料和胎体帘布的截面弯曲刚度计算方法,并对成品轮胎进行分析,为轮胎屈挠变形的评判和改善提供了参考途径。     

整体中空夹层复合材料弯曲刚度研究

基于整体中空夹层复合材料的织物结构特点以及对经纬向弯曲变形现象的分析,建立两种夹层梁模型,分别推导了经向与纬向弯曲刚度的解析表达式。通过理论解、有限元解以及试验值的对比,验证了模型的合理性和准确性。在此基础上,运用本文理论方法探讨了纱线密度对整体中空夹层复合材料弯曲刚度的影响。研究表明,随着纱线密度的增加,整体中空夹层复合材料经纬向弯曲刚度均呈线性增加;经向弯曲刚度的影响因素按影响程度从大到小依次为经纱、绒经、纬纱;纬向弯曲刚度的影响因素按影响程度从大到小依次为纬纱、经纱、绒经;和纬向弯曲相比,绒经对经向弯曲刚度的影响更大。     

CFRP加固钢筋混凝土梁裂缝宽度与刚度的计算方法

科学技术的快速发展给工程建设提供了强大的技术支持,新材料以及新工艺的不断涌现极大地促进了工程建设的发展,在水利工程以及土木工程建设中,纤维复合材料以其轻便、抗腐蚀等优点得到了广泛的运用。如何采用纤维复合材料进行混凝土结构加固一直是国内外的研究热点,有关裂缝宽度与刚度的计算方法也在不断完善与进步。     

Corrosion damage diagnosis of a reinforced concrete beam after 40 years natural exposure in marine environment

A detailed investigation of the chloride induced corrosion damage was performed on a 40 years old reinforced concrete beam exposed in marine environment. Visual observations, electrochemical measurements, carbonation depth, total chloride content were carried out. Half-cell potential measurements were used to locate corrosion areas. It appeared that the interpretation based on gradient of the potential was in good concordance with real state of damage. Complementary destructive methods are applied to observe the real corrosion state of steel rebars and characterize the corrosion products and the steel/concrete interface (optical and electronical microscopy tools (XRD, SEM, EDS and μ-Raman).All these data indicate that on the beam, one may distinguish two types of areas: “high-corrosion zones” and “low-corrosion zones.” Given the fact that the “high corrosion zones” were found to be close to corrosion induced cracks and that they have a different morphology, this contribution concludes that the position of these areas did not shift in time.     

超高压蒸汽管线的强度核算及异径管小端裂纹的成因

对某厂超高压蒸汽（ＳＳ）管线的裂纹进行了强度校核。分别用等值刚度法ＦＡＯＰ及三维有限元法ＳＡＰ５Ｐ计算程序,对该管线进行了应力计算。结果表明,此管线的静强度足够。又用ＳＡＰ５Ｐ程序中８～２１节点等参单元,对在环焊缝处产生长裂纹的异径管进行了详细应力分析。给出了裂纹所在截面的轴向应力数值。并探讨了裂纹形成原因     

蜂窝状钢骨混凝土十字形柱-钢梁连接节点性能

为全面探讨梁柱节点的受力性能与变形特性,进行了蜂窝状钢骨混凝土十字形柱-钢梁节点的单调加载试验研究和有限元分析,重点考察典型强、弱节点的承载能力、破坏形态以及轴压比、配箍率等主要参数对节点承载力的影响。结果表明:影响强节点承载力的主要因素是钢梁尺寸和钢材强度,影响弱节点承载力的主要因素是混凝土强度、节点区型钢腹板强度和高厚比。     

Modified clamped beam bend method for determination of interfacial fracture energy of thermally sprayed Yttria Stabilised Zirconia over steel

A novel modified clamped beam bend method is developed to measure interface fracture energy of metal/ceramic interfaces. Finite element simulations are used to determine the energy release rate as a function of crack length and loading offset. The experimental procedure for the geometry is demonstrated by measuring interface fracture energy of thermally sprayed Yttria Stabilised Zirconia (YSZ) coating on steel. A smaller load offset is used to create the pre-crack. Subsequently, a larger offset is used to propagate the interface pre-crack, with the signature in the load-displacement curve used to determine the corresponding critical load. Interface fracture energy is obtained as critical energy release rate, G_C, using numerically computed values of J–integral. Finite element simulations are further performed for various coating to substrate thickness ratios and modulus ratios, to characterize trends in energy release rate and phase angles and assess the applicability of the geometry across other material systems.     

A comparison of bending strength between adhesive and steel reinforced concrete with steel only reinforced concrete

Cracking of brittle cementitious composites subjected to excessive loading causes a potential reduction in material performance. Steel bars or metal fibers typically act as tensile reinforcing in concrete composites to increase the material's structural capacity in bending and to delay or prevent matrix cracking.The goal of this research is to determine whether the performance in bending strength and material integrity of a typically reinforced cementitious composite may be improved through the release of “healing” chemicals, such as adhesives, from hollow fibers into cracks induced by loading in addition to the metal reinforcing. Adhesive-filled repair fibers are intended to break immediately upon cracking in the concrete thereby activating the healing process with the release of a sealing or adhering substance. This self-repair occurs whenever and wherever cracks are generated.     

Modeling of time to corrosion-induced cover cracking in reinforced concrete structures

Service life of the concrete structures depends on the protective action provided by the cover concrete against the susceptibility of the reinforcement to the corrosive environment. Depending on the level of the oxidation of metallic iron, corrosion products may have much greater volume than the original iron that gets consumed by the process of corrosion. This volume expansion is mainly responsible for exerting the expansive radial pressure at the steel-concrete interface and development of hoop tensile stresses in the surrounding concrete resulting ultimately in the through cracking of the cover concrete. This cover cracking would indicate the loss of the service life for the corrosion-affected structures. In the present paper, an attempt has been made to develop analytical models for predicting the time to cover cracking by considering the residual strength of the cracked concrete and the stiffness provided by the combination of the reinforcement and expansive corrosion products. The problem is modeled as a boundary value problem wherein the governing equations are expressed in terms of the radial displacement and the analytical solutions are presented considering a simple 2-zone model for the cover concrete viz. cracked or uncracked. The analytical models are then evaluated through their ability to reproduce available experimental trends and subsequently a sensitivity analysis has also been carried out to show the influence of the various variable parameters of the proposed models with reference to the experimental trends.     

高强型钢混凝土柱承载力计算的研究现状

目前型钢混凝土柱中的型钢与混凝土越来越多地采用高强材料，形成了三类高强型钢混凝土柱：采用高强型钢的类型、采用高强混凝土的类型、同时采用高强型钢与高强混凝土的类型。目前有关高强型钢混凝土柱承载力的研究可分为两大类：国内外主要规范（规程）中的计算方法，规范（规程）以外的研究及方法。基于对这两大类研究的介绍与对比分析，从正截面偏压承载力、正截面轴压承载力和斜截面受剪承载力三方面分别给出了相应的推荐计算方法或者指明了待完善的研究方向。     

危险废物检测常见误差分析及应对措施

随着工业的不断发展,工业生产过程中产生的危险废物也日益增多,危险废物处置的需求也不断扩大。危险废物不处理或不规范处理处置所带来的大气、水源、土壤等的污染也将会成为制约可持续发展的瓶颈。危险废物处置行业已经成为当前蓬勃发展的行业,如何提高危险废物检测的准确性、避免危险废物检测过程中产生误差也成了各危险废物处置单位重点关注的事情。本文对危险废物检测各个流程可能产生系统误差的点进行了梳理,并给出了问题的解决手段。     

Presumption of shear strength of steel fiber reinforced concrete beam using artificial neural network model

The shear force characteristics of steel fiber reinforced concrete (SFRC) are investigated with varying shapes and mixture ratios. However, because experimental characterization of SFRC is experimentally demanding in terms of time and equipment, the characterized SFRC data are used with limitation. Therefore, for various applications, an easier approach is required to predict the shear force characteristics of unsaturated soils. In consideration of such a situation, a method to ascertain the shear force characteristics of SFRC is suggested and applied to this study as a neural network theory. The backpropagation algorithm is applied as a learning algorithm for a neural network, and learning is performed in order to converge within an error range of 0.001. In addition, a nonlinear function is used as an objective function and the problem of overfitting is resolved with a more generalized method by adopting the Bayesian regularization technique as a generalization process. To identify the reliability of this artificial neural network model, we compare values from the shear strength test of SFRC beams with the values from the model. They show correspondence between them. Therefore, it is concluded that, if many test variables and data are used as input for learning in the neural network model developed in this study, it is possible to attain a much more reliable prediction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2351–2358, 2007     

中欧美标钢筋混凝土梁设计对比分析

详细分析比较了中国标准,美国标准和欧洲标准在混凝土梁设计时的荷载组合和设计基础、材料、混凝土梁计算公式和流程等方面的异同。在此基础上,采用某国外水泥厂的相同设计条件,对比分析采用中欧美国规范时,钢筋混凝土梁的截面和配筋结果存在的差异。三种标准的正截面计算公式相似,只是由于荷载组合的差异造成了最终设计结果的差异,实际设计时应考虑多方面因素的影响。