波形钢板混凝土界面间粘结滑移力学性能研究

根据压型钢板混凝土组合楼板剪切粘结滑移和型钢混凝土粘结滑移的试验研究成果,分析了两者界面之间的粘结应力、应变的分布规律.基于试验研究成果,对轴心力作用下的波形钢板混凝土粘结滑移力学问题做了合理假定.从弹性力学角度推导了混凝土、波形钢板各自应力和位移的理论公式,并得出两者界面间滑移的理论公式,这为有限元分析波形钢板混凝土提供了理论依据.通过考虑混凝土浇筑方式、波角的影响因素设计了5个波形钢板混凝土推出试件,研究波形钢板与混凝土界面间粘结滑移力学性能.根据试验结果,提出了粘结强度特征值与波角的计算公式,发现波形钢板表面应变沿锚固深度呈指数分布规律.同时,得出了波形钢板等效应变特征值与波角的关系,提出了波形钢板等效应力计算公式.最后,通过对比分析基于弹性力学的粘结应力理论公式解和试验所得等效粘结应力解,发现两者吻合良好.     

型钢混凝土粘结滑移性能试验分析

针对型钢混凝土粘结滑移性能，设计了两种推出试验的试验方案，并研制了一种内置式钢-砼电子滑移传感器，对型钢与混凝土之间的粘结滑移性能进行了试验研究，主要对型钢翼缘和腹板应变、内部滑移进行了试验测量，并根据试验结果，得出了P-S曲线及型钢翼缘和腹板应变及内部粘结滑移的分布规律，分析了粘结破坏的破坏机理和裂缝分布规律，本文可对型钢混凝土粘结滑移性能的进一步试验研究和理论分析提供参考。     

埋入式柱脚粘结滑移性能的试验研究

探讨埋入式柱脚压弯状态下型钢与混凝土的粘结滑移性能。通过自行研制的内置式型钢-混凝土电子滑移传感器对内部滑移进行了测量,解决了型钢混凝土粘结滑移试验研究的一个难题。基于试验结果,得到考虑界面正应力影响的型钢-混凝土的粘结滑移关系,为型钢混凝土受力变形全过程数值分析提供了本构模型。     

L形型钢混凝土柱小偏心压弯性能的研究

L形型钢混凝土柱在实际工程中具有良好的应用前景.对于这一新的结构形式,目前尚未有成熟的研究资料.用ANSYS程序模拟L形型钢混凝土柱在小偏心力作用下的压弯性能,分析加载位置和含钢率两因素对承载力的影响.为进一步分析型钢与混凝土之间粘结滑移特性,建立矩形柱模型做参考.比较不考虑滑移与考虑滑移的L形型钢混凝土柱的模拟结果,表明数值模拟中滑移是不客忽视的.     

湿热环境下粘钢加固混凝土界面的粘结性能

钢板-混凝土界面粘结性能是粘贴钢板加固混凝土结构的关键。通过对湿热环境下27个钢板-混凝土试件进行试验研究,分别进行5、10、15 d的加速湿热老化,然后进行双剪试验,获得了钢板-混凝土界面发生剪切剥离破坏过程中的极限荷载、钢板应变分布及荷载-位移关系。分析了环境温度、湿度耦合作用对钢板-混凝土界面粘结耐久性能的影响,并综合考虑钢板-混凝土的粘结破坏模式、受力过程、粘结界面相对位移发展规律,提出了粘结界面剪应力、滑移与温度和湿度相关的表达式。建立了考虑温度、湿度影响的粘结-滑移本构关系模型,数值模拟结果与试验结果吻合较好。     

型钢混凝土粘结强度的研究

通过假定型钢混凝土粘结滑移层的剪切破坏机构，在考虑节理单元厚度为零的基础上，采用上限理论对型钢混凝土粘结强度进行理论推导，得到了型钢与混凝土粘结剪切强度的上限解，并确定了其主要影响因素，本文可对型钢混凝土粘结滑移性能的进一步试验研究和理论分析提供参考。     

T型钢与混凝土粘结强度的试验研究

通过8个型钢(T型钢)混凝土试件粘结滑移性能的推出试验,分析了荷载与加载端滑移曲线的分布规律,研究了混凝土强度、混凝土保护层厚度、横向配箍率三个因素对型钢混凝土粘结强度的影响.试验结果表明,混凝土强度、混凝土保护层厚度、横向配箍率对粘结强度影响显著,近似呈线性关系,综合考虑这三个因素,统计回归出型钢混凝土特征粘结强度和特征滑移值的计算公式,与试验值对比分析,符合较好;并建立了型钢混凝土平均粘结强度-加载端滑移本构关系的数学模型.     

循环荷载作用下CFRP-混凝土界面粘结-滑移关系研究

循环荷载作用下CFRP-混凝土界面粘结-滑移关系是研究CFRP加固混凝土结构疲劳性能的重要基石.通过对18个双面剪切试件进行静载及疲劳试验,分析探讨了循环荷载作用下CFRP-混凝土界面破坏过程及粘结-滑移关系.结果表明,随着循环荷载次数及应力水平增大,界面粘结性能降低,CFRP片材也更早出现剥离现象,剥离长度和应力水平呈线性关系;端部滑移变化表现为两个阶段,快速增长阶段和稳定增长阶段;应力水平越高,对应的粘结-滑移曲线中最大剪应力就越大.     

具有荷载作用历史的CFRP-钢界面粘结性能试验

为研究荷载作用历史对碳纤维增强复合材料（CFRP）加固钢结构界面粘结性能的影响,开展4种界面剪应力水平、6种持载时间的CFRP-钢双剪试件长期加载试验,对达到规定加载时间的试件进行静力拉伸破坏.根据CFRP轴向应变数据,给出了界面剪应力分布及粘结滑移曲线,考虑到界面蠕变损伤对粘结滑移本构关系的影响,在双线性模型中引入系数β、η、γ,回归分析得到了这3个系数的表达式.结果表明:胶黏剂的蠕变变形会引起界面应力重分布,随着时间的增加CFRP应变增大,界面剪应力峰值减小;加载90 d后,在12.5 mm处B组、C组、D组、E组试件界面剪应力分别减小了26.6%、59.2%、73.8%、85.4%;当界面剪应力水平较高时,应考虑界面蠕变损伤对粘结滑移曲线的影响,界面剪应力水平越高持续时间越长,蠕变损伤越显著;当CFRP粘贴长度大于有效粘结长度时,界面蠕变损伤对极限承载力没有明显影响.     

型钢混凝土基准粘结滑移本构关系试验研究

进行型钢混凝土标准推出试件试验，对型钢混凝土粘结滑移性能和粘结滑移受力机理研究．根据荷载-加载端滑移曲线的试验研究结果，建立型钢混凝土特征粘结强度、特征滑移的统计回归计算公式，并提出型钢混凝土粘结滑移本构关系数学模型．进一步采用所建立粘结滑移基准本构模型对型钢混凝土推出试件进行ANSYS数值模拟分析，数值模拟结果与试验结果吻合较好．研究结果表明，所建立型钢混凝土粘结滑移本构模型简单实用，并且能较全面的反映混凝土强度等级、横向配箍率、型钢埋置长度和型钢保护层厚度等主要影响因素的影响，可为型钢混凝土粘结滑移性能和型钢混凝土结构数值模拟技术研究提供参考．     

Unified analytical stress- strain curve for quasibrittle geomaterial in uniaxial tension, direct shear and uniaxial compression

Considering strain localization in the form of a narrow band initiated just at peak stress, three analytical expressions for stress - strain curves of quasibrittle geomaterial （such as rock and concrete） in uniaxial tension, direct shear and uniaxial compression were presented, respectively. The three derived stress - strain curves were generalized as a unified formula. Beyond the onset of strain localization, a linear strain-softening constitutive relation for localized band was assigned. The size of the band was controlled by internal or characteristic length according to gradient-dependent plasticity. Elastic strain within the entire specimen was assumed to be uniform and decreased with the increase of plastic strain in localized band. Total strain of the specimen was decomposed into elastic and plastic parts. Plastic strain of the specimen was the average value of plastic strains in localized band over the entire specimen. For different heights, the predicted softening branches of the relative stress- strain curves in uniaxial compression are consistent with the previously experimental results for normal concrete specimens. The present expressions for the post-peak stress - deformation curves in uniaxial tension and direct shear agree with the previously numerical results based on gradient-dependent plasticity.     

Shear stress distribution and characteristics of deformation for shear band-elastic body system at pre-peak and post-peak

The distributed shear stress and the displacement across shear band, the evolution of plastic zones, and the load-carrying capacity of rock specimen were investigated in plane strain direct shear test according to Fast Lagrangian Analysis of Continua （FLAC）. And then the shear displacement distribution in normal direction of system composed of localized shear band and elastic rock was analyzed based on gradient-dependent plasticity. The adopted failure criterion was a composite of Mohr-Coulomb criterion, that is, the relation between tension cut-off and postpeak constitutive of rock was linear strain-softening. Numerical results show that shear stress field approximately undergoes three different stages. At first, shear stress is only concentrated in the middle of top and base of specimen. Next, shear stress in the middle of specimen tends to increase, owing to superposition of shear stresses. Interestingly, two peaks of shear stress appear far from the loading ends of specimen, and the peaks approach with the increase in timestep until elements at the center of specimen yield. Finally, relatively lower shear stress level is reached in large part of specimen except in the regions near the two ends. As flow stress decreases, the analytical shear displacement distribution in shear band based on gradient-dependent plasticity becomes steeps outside the band, it is linear and its slope tends to decrease. These theoretical results qualitatively agree with that of the present numerical predicted results. Main advantage of the analytical solution over the numerical results according to FLAC is that it is continuous, smooth and non-linear （except at elastic stage）.     

各向异性砂土剪切带角度的理论分析

针对平面应变条件下各向异性砂土剪切带角度的试验规律,采用传统的3种理论和分叉理论进行对比分析。将平面应变条件下剪切带角度的试验结果按照传统3种理论整理发现,尽管传统3种理论可以估算同种砂剪切带角度的极小、中间和极大值,但无法解释其各向异性规律。砂土在平面应变条件下破坏时会产生明显的剪切带,当剪切带方向和砂土沉积面方向接近时,会较早诱发剪切带的产生,使材料强度降低,造成了平面应变条件下各向异性强度规律明显不同于常规三轴条件下的试验规律,采用分叉理论结合各向异性模型则可以有效解释这个规律。随砂土沉积面角度的变化,模型可以从细观角度解释常规三轴条件下剪切带角度的单调变化的试验规律,结合分叉理论可以描述平面应变条件下其先减小然后增大的规律。通过几种理论对比分析表明,模型结合分叉理论不但能够描述多种应力状态下的平面应变和常规三轴应力条件下剪切带角度表现的不同规律,而且能够从细观角度解释其各向异性成因。     

平面应变含缺陷岩样变形破坏全过程数值模拟

采用拉格朗日元法(FLAC)研究了左边界有缺陷的压缩岩样剪切带的启动及演变规律，峰后本构关系采用线性应变软化模型．计算结果表明，在应力一时步曲线峰值之前，剪切带首先出现在缺陷附近，直到贯通试样右边界；在剪切带传播过程中，塑性区沿切向及法线向外扩展；剪切带内部单元的剪切应变率一时步曲线经历了稳定、线性上升和非线性上升3个阶段．然而，剪切应变增量随时步持续增加．剪切带倾角接近于Arthur倾角，表明数值计算结果是可信的。     

双轴压缩试验中砂土剪切带形成的离散元模拟分析

采用离散单元法软件PFC2D模拟了大量砂土试样双轴试验,分析了砂土剪切带形成机理及发展过程,并通过研究试样剪切带内外应力-应变关系及孔隙比、平均接触数及配位数等参数的变化情况,研究了带内外宏微观性质的差异。研究表明:砂土剪切带的形成过程即为试样内部应变局部化过程,也为试样内部平均转动率(averaged pure rotation rate, APR)的局部化;剪切带开始形成点也为试样剪缩、剪胀分界点;剪切带内外各宏微观参数变化规律上存在明显的差异,主要表现为近剪切带位置土体及带内土表现为应变软化现象,而距带中心较远土体应力应变关系曲线出现‘回滞圈’现象;带内变形量明显大于带外,且带内较带外松散。     

Dynamic analysis of fault rockburst based on gradient-dependent plasticity and energy criterion

Fault rockburst is treated as a strain localization problem under dynamic loading condition considering strain gradient and strain rate. As a kind of dynamic fracture phenomena, rockburst has characteristics of strain localization, which is considered as a one-dimensional shear problem subjected to normal compressive stress and tangential shear stress. The constitutive relation of rock material is bilinear (elastic and strain softening) and sensitive to shear strain rate. The solutions proposed based on gradientdependent plasticity show that intense plastic strain is concentrated in fault band and the thickness of the band depends on the characteristic length of rock material. The post-peak stiffness of the fault band was determined according to the constitutive parameters of rock material and shear strain rate. Fault band undergoing strain softening and elastic rock mass outside the band constitute a system and the instability criterion of the system was proposed based on energy theory. The criterion depends on the constitutive relation of rock material, the structural size and the strain rate. The static result regardless of the strain rate is the special case of the present analytical solution. High strain rate can lead to instability of the system.     

Effect of Relative Stress on Post-Peak Uniaxial Compression Fracture Energy of Concrete

1　IntroductionItisrealizedthatthelinearelasticfracturemechan icsisnownotapplicabletofractureinordinaryconcretestructures .Todescribethesofteningbehaviorofconcrete ,differentmodelsbasedonnon linearfracturemechanicalideaswereproposed ,suchasthefictitiouscrackmodel[1](FCM )byHillerborgetal.(1976 ) ,thecrackbandmodel[2 ] byBazant (1983) ,andthetwo parameterfrac turemodel[3 ] byJenqandShah (1985 ) .ThedifficultywithFCMliesindeterminingtheval uesofthethreeparametersbyexperiments .Toobtaintheval…     

Volume Change of Heterogeneous Quasi-brittle Materials in Uniaxial Compression

The volumetric strain was categorized into elastic and plastic parts. The farmer camposed of axial and lateral strains is uniform and determined by Hooke＇s law ; however, the latter consisting of axial and lateral strains is a fuaction af thickness af shear band determined by grndieat-dependeat plasticity by cansidering the heterngeneity of quasi- brittle materials. The non- uniform lateral strain due to the fact that shear band was farmed in the middle of specimen was averaged within specimen to precisely assess the volumetric strain. Then, the analytical expression for volumetric strain was verified by comparison with two earlier experimental results for concrete and rack. Finally, a detailed parametric study was carried out to investigate effects of constitutive parameters （ shear band thickness, elastic and softening rnoduli ） and geometrical size of specimen（ height and width of specimen ） on the volume dilatancy.     

木-混凝土连接性能试验研究

目的研究木与混凝土间粘结作用,为木-混凝土组合结构的研究奠定前期基础．方法根据设置于木材表面抗剪连接件的形式及抗剪连接件数量的不同设计制作了三组共计九根木与混凝土间抗剪连接件试件和一根无抗剪连接件的对比试件,采用推出试验方法对木材进行加载直至木与混凝土间发生滑移破坏．结果通过推出试验获得了木-混凝土推出荷载的大小、木材在混凝土中滑移量、木材表面抗剪连接件荷载作用下其应力变化等相关实验数据．结论抗剪连接件的存在能够明显抑制木材与混凝土间受力过程中的相对滑移,相对滑移量的减少与抗剪连接件数量成正比,同时也与抗剪连接件形式有关;加载过程中抗剪连接件所受应力与抗剪连接件形式有关,同时也与抗剪连接件距加载点距离有关;研究也表明：抗剪连接件的存在对木与混凝土间粘结力的提高无明显影响。     

分组集聚式斜拉桥索塔锚固区传力机制

为研究新型分组集聚式斜拉桥锚固形式应力安全及钢-混传剪机理,以某公路大桥为背景,选取分组集聚索塔锚固节段为分析对象,运用有限元软件ABAQUS建立锚固区精细的数值模型.根据桥塔等效杆系模型的分析结果确定节段模型准确的荷载及边界条件,分别计算分析了3种工况下锚固区混凝土及钢横梁应力分布;通过对钢-混界面的各向应力及位移分布研究,探讨在不同程度预应力损失和钢-混界面摩擦系数影响下钢横梁与混凝土桥塔的传剪受力机理.研究结果表明:设计荷载工况下,钢横梁梁端剪力主要由界面静摩擦力承担,塔柱与钢横梁未发生相对滑动,具有足够安全储备;当锚杆预应力损失达到60%或接触面摩擦系数减小为0.2时,钢-混界面处于临界摩擦状态,相对滑移增大,结构处于相对不安全状态.