试论盐及溶液对混凝土及钢筋混凝土的破坏

本文就盐及溶液对混凝土及钢筋混凝土破坏作用的模式、机理及特征进行了论述。并提出了在理论分析及试验研究中区分不同破坏模式的重要意义。     

碳纤维布加固钢筋混凝土梁弯曲破坏模式分析

分析并提出碳纤维布加固混凝土梁可能发生的9种弯曲破坏模式及各种破坏模式之间的相互转化条件,在此基础上给出常见破坏模式下加固梁的抗弯承载力,并通过文献试验数据对提出的结论进行验证。     

火灾后RC及HFRC隧道管片破坏试验研究

为研究火灾后盾构隧道管片的破坏模式,借助火灾试验手段,对钢筋混凝土(RC)及混杂纤维混凝土(HFRC)两种类型的管片在不同工况下的破坏模式进行了研究。根据试验结果,受正弯矩单向加载的钢筋混凝土管片的极限承载力和变形性能均大于混杂纤维混凝土管片。在该工况下,钢筋混凝土管片的破坏模式为弯曲破坏,混杂纤维混凝土管片的破坏模式则为弯曲剪切破坏。而在受负弯矩双向加载的工况下,钢筋混凝土管片为剪切破坏模式,而混杂纤维混凝土管片为受弯破坏模式。由于破坏模式的差别,导致混杂纤维混凝土管片的变形发挥要优于钢筋混凝土管片。基于以上结论,笔者对盾构隧道管片的抗火设计提出了一些相关建议。     

FRP片材加固混凝土梁界面剥离分析

纤维增强复合材料（FRP）片材与混凝土之间的界面剥离破坏是FRP片材加固混凝土梁的重要破坏模式。基于近年来国内外关于FRP片材加固混凝土构件的静载试验结果和力学理论知识,讨论了FRP片材加固混凝土梁界面剥离的破坏模式与破坏形态,分析了加固梁发生端部界面剥离和中部界面剥离两种破坏模式的破坏机理,并提出了预防加固梁发生界面剥离破坏的建议。     

实腹式型钢高强混凝土柱剪切粘结破坏承载力计算

实腹式型钢混凝土(SRC)柱剪切破坏包括剪切斜压破坏和剪切粘结破坏两种破坏模式,因剪切粘结破坏机理复杂、其影响因素较多,目前缺乏较为准确的剪切粘结破坏承载力计算方法。本文在分析已有剪切粘结破坏承载力计算方法的基础上,结合试验研究,提出了一种新的剪切粘结破坏承载力计算方法。采用文献中42个型钢高强混凝土柱压剪试件的试验结果,对日本标准、我国标准、本文建议方法的计算结果进行了分析对比。结果表明,本文建议方法对型钢高强混凝土柱剪切粘结破坏的判别以及对压剪承载力的估计较为准确,有很好的工程应用价值。     

爆炸荷载作用下钢-混凝土组合梁的动力响应及破坏形态分析

本文利用LS-DYNA软件对同冲量不同超压峰值不同时间的三种荷载工况下钢-混凝土组合梁的动力响应及破坏模式进行了研究对比,并对梁的变形过程、关键位置点的位移、速度、支座剪力和跨中弯矩进行了详细的分析。结果表明,在爆炸冲击波下,开始阶段混凝土板对钢梁有很好的保护作用,但混凝土易于破碎,钢-混凝土组合梁容易丧失共同工作的能力,剪切破坏是钢-混凝土组合梁的一种重要破坏形式。     

宁夏盐渍地区混凝土破坏模式与防治研究

本文分析了宁夏盐渍地区水质腐蚀类型、混凝土结构破坏模式及腐蚀机理;提出抗腐蚀混凝土配方,并用此配方混凝土试块在硫酸钠溶液中浸泡试验验证其抗腐蚀性能,经初步试验本配方能抗中等腐蚀作用.     

混凝土植筋破坏形态分析

对几种混凝土植筋破坏形态进行了详细分析,给出并比较了两种粘结破坏假设;均匀剪切模式和弹性剪切模式。提出了求解胶体剪切模量和最大剪应力的简单方法。计算结果与试验结果对比显示,弹性剪切模式公式可以用于混凝土植筋的设计计算。     

接触爆炸荷载下钢-混凝土组合梁的破坏模式研究

运用LS-DYNA软件对接触爆炸荷载下钢-混凝土组合梁的破坏形式进行了数值分析,研究了混凝土板的破坏过程及梁的破坏模式.结果表明,钢-混凝土组合梁以局部变形为主,混凝土易于破碎,钢梁与混凝土板易丧失共同工作的能力,而接触爆炸荷载下钢-混凝土组合梁主要有三种不同的破坏模式,分别为混凝土板的破碎、钢梁的局部大变形和荷载作用区的局部冲切破坏.     

混凝土植筋破坏形态分析

对几种混凝土植筋破坏形态进行了详细分析,给出并比较了两种粘结破坏假设:均匀剪切模式和弹性剪切模式。提出了求解胶体剪切模量和最大剪应力的简单方法。计算结果与试验结果对比显示,弹性剪切模式公式可以用于混凝土植筋的设计计算。     

工业厂房柱钢筋锈胀破坏模式及半电池法现场检测分析

介绍了在室内干燥环境中,某工业厂房排架结构柱的钢筋锈蚀现场调查结果;对半电池方法在实际混凝土工程结构中的应用展开了讨论;指出美国ASTM标准以电极电位为基本评价体系的局限性。采用有限元方法模拟服役构件的真实应力状态,分析得到钢筋混凝土偏心受压柱的受压区钢筋锈蚀后,在锈蚀产物体积膨胀和轴向压应力的联合作用下,构件受压区钢筋周围混凝土中平均拉应力的分布情况。提出在多维应力作用下,混凝土表面锈胀裂缝的开展形式与单纯锈胀力作用时基本一致,但是压应力的存在会明显加速表层混凝土锈胀裂缝的开展,而且一旦开裂,表层混凝土的层状剥落和边角剥落会发展得更快。     

Deteriorating beam finite element for nonlinear analysis of concrete structures under corrosion

A three-dimensional reinforced concrete (RC) deteriorating beam finite element for nonlinear analysis of concrete structures under corrosion is presented in this study. The finite element formulation accounts for both material and geometrical nonlinearity. Damage modelling considers uniform and pitting corrosion and includes the reduction of cross-sectional area of corroded bars, the reduction of ductility of reinforcing steel and the deterioration of concrete strength due to splitting cracks, delamination and spalling of the concrete cover. The beam finite element is validated with reference to the results of experimental tests carried out on RC beams with corroded reinforcement. The application potentialities of the proposed formulation are shown through the finite element analysis of a statically indeterminate RC beam and a three-dimensional RC arch bridge under different damage scenarios and corrosion penetration levels. The results indicate that the design for durability of concrete structures exposed to corrosion needs to rely on structural analysis methods capable to account for the global effects of local damage phenomena on the overall system performance.     

某隧道衬砌混凝土的碳硫硅钙石侵蚀试验分析

针对某隧道衬砌混凝土产生膨胀、剥落和软化的质量问题,通过对混凝土所用原材料、水文地质环境和气候条件的调查,结合原材料试验和腐蚀物的XRD相关数据,分析混凝土腐蚀过程以及侵蚀机理。研究表明,碳硫硅钙石侵蚀是引起混凝土腐蚀的主要原因,应引起高度重视。     

Hydrothermal model for predicting fire-induced spalling in concrete structural systems

A one-dimensional numerical model to predict fire-induced spalling in concrete structures is presented. The model is based on pore pressure calculations in concrete, as a function of time. Principles of mechanics and thermodynamics are applied to predict pore pressure in concrete structures exposed to fire. An assessment of the possibility of tensile fracture is made by comparing the computed pore pressure with temperature-dependent tensile strength. The pore pressure calculations are coupled with heat transfer analysis to ensure that the loss of concrete section, resulting from spalling, is accounted for in subsequent heat transfer analysis. The validity of the numerical model is established by comparing temperature, pore pressure, and concrete spalling predictions with results from fire tests. The computer program is applied to conduct case studies to investigate the influence of concrete permeability, tensile strength of concrete, relative humidity in concrete, and heating rate on fire-induced spalling in concrete members. Through these case studies, it is shown that permeability, tensile strength of concrete, and heating rate have a significant influence on fire-induced spalling in concrete. It is also shown that relative humidity has a marginal influence on fire-induced spalling in concrete.     

基于材料劣化的既有混凝土构件数值建模方法研究

基于ABAQUS,以多龄期混凝土构件为研究对象,在数值建模方面,采用三维实体线性减缩单元C3D8R和两结点三维单元T3D2模拟混凝土材料、内嵌钢筋的力学行为,将指数衰减摩擦模型用于锈蚀钢筋与混凝土间接触问题上,并将Hsich-Ting-Chen四参数强度准则作为混凝土材料的破坏准则;在材料性能退化方面,基于修正斜压场理论,以锈蚀箍筋、纵筋、受压区锈胀开裂混凝土及核心区约束混凝土为对象,综合各既有材料退化模型,预测了材料退化后的力学性能,得到了开裂混凝土、锈蚀钢筋、混凝土及其之间黏结滑移的本构模型。进而,采用多龄期混凝土构件抗震性能试验研究结果,对提出的基于ABAQUS软件平台的锈蚀混凝土构件数值建模理论进行了可靠性验证,结果表明:所建立的数值建模理论可以有效地模拟锈蚀混凝土构件的抗震性能退化规律,为既有混凝土结构的数值建模理论提供了一种有效的研究方法。     

服役桥梁混凝土耐久性试验研究

服役一定年限后,由于结构自然老化、不良环境影响、车辆荷载增加以及养护维修欠缺,钢筋混凝土桥梁往往出现一定程度的病害,如混凝土腐蚀、钢筋锈蚀、梁体开裂,甚至保护层剥落等劣化现象.这势必导致桥梁结构的承载能力和耐久性降低、使用功能减退.通过检测鉴定,对服役桥梁的工作现状作出合理的评价具有重要的工程指导意义.通过现场和实验室试验,对已服役15年的青岛市振华路立交桥主梁混凝土的碳化及氯离子渗透情况进行了定量研究,分析了钢筋锈蚀的可能性,并依此对该桥的混凝土耐久性现状进行了评价,对已面临混凝士碳化威胁的桥梁耐久性提升提出了合理的建议.     

A numerical investigation of the influence of pore pressures and thermally induced stresses for spalling of concrete exposed to elevated temperatures

Although in past years extensive experimental and numerical investigations have been carried out in order to gain better understanding of the phenomenon of spalling of concrete exposed to elevated temperatures, there still exists controversy as to the driving mechanisms of spalling. This paper presents a numerical investigation aimed at determining the significance of pore pressures and thermally induced stresses for spalling of a concrete. A mathematical model for the coupled hygro-thermal-mechanical-damage behaviour of the concrete is briefly presented together with its finite element solution procedure. Although not intended for design purposes at this stage, the model provides insight into the interactions of the physical process that occur when concrete is exposed to elevated temperatures and can provide impetus for further development of numerical solutions for accurate prediction of spalling. The model is here employed to investigate the significance of pore pressures and thermally induced stresses for spalling of concretes with different initial permeabilities and moisture contents through the numerical simulation of a wall and a square column exposed to fire. The numerical results reveal that thermally induced stresses are a primary factor in causing damage and hence spalling in concrete, while pore pressures, at most, play a secondary role.     

氯离子侵蚀环境下基于可靠性的混凝土结构耐久寿命预测

对氯离子侵蚀作用下基于可靠性的混凝土结构耐久寿命预测进行了研究。首先,确定氯离子环境作用下对应的性能水准和结构耐久性极限状态,然后,选择氯离子侵蚀深度模型和钢筋锈胀模型,以极限状态模式建立失效概率方程,在满足规定的失效概率条件下,确定结构的耐久性寿命,并给出不同性能水准的计算实例。结果表明,基于可靠性的混凝土结构耐久寿命预测方法与工程实例调查结果相一致,该方法可以有效地用于氯离子侵蚀环境下结构耐久寿命预测。     

某通廊结构的检测鉴定

某通廊经过50年的使用,已发生不同程度的损伤。结构材料逐渐老化,构件出现不同程度的开裂、钢筋锈蚀、混凝土疏松剥落及碳化,结构的可靠度下降,严重影响了结构的安全和正常使用。通过对通廊结构进行的现场检测、结构计算分析和可靠性鉴定评级,提出了加固处理方案。对该类结构的检测鉴定具有一定的参考。     

The behaviour of reinforced concrete slabs in fire

In this paper a robust model is presented based on the previous layer procedure developed by the author to also take into account the effects of concrete spalling on the behaviour of concrete slabs under fire conditions. In this study, a detailed analysis of a uniformly loaded reinforced concrete slab subject to different degrees of concrete spalling under a standard fire regime is first carried out. Further, a series of analysis of floor slabs with different degrees of concrete spalling is also performed on a generic reinforced concrete building. A total of 16 cases have been analysed using different degrees of spalling on the slabs, with different extents and positions of localised fire compartments. It is clear that adjacent cool structures provide considerable thermal restraint to the floor slabs within the fire compartment. And it is evident that the compressive membrane force within the slabs is a major player in reducing the impact of concrete spalling on the structural behaviour of floor slabs in fire.