In order to investigate the seismic performance of prestressed concrete rocking frame (PCRF), a theoretical model based on rigid body is established for a one-story single-span PCRF. The PCRF studied in this paper has the connecting interfaces set at the column feet and at the inner faces of the beam–column joints, allowing the columns to be uplifted with the accompanying separation of the beam–column interface and rotation of the beam and column around the interface. The tendons are arranged along the centerline of the beam and columns. The connections between the beam and columns and the anchoring of columns are accomplished by prestressing the tendons. The theoretical model consists of a rigid beam, rigid columns and elastic tendons. The governing motion equation of the PCRF is derived based on the model and a numerical solution of the equation of motion is obtained. The energy dissipation of the PCRF is analyzed and the calculation method for the coefficient of restitution is derived. Time history analysis and parameter analysis of seismic response of the PCRF are conducted and the results show that the PCRF has promising seismic behavior.

针对SHDM结构(由依赖应变历史材料制成的结构)有限元非线性静力平衡方程组动力松弛法(DRM)迭代求解时的积分点应力更新步骤,提出非线性弹性增量算法,即在一个静力增量步内固定材料的加卸载路径,使之在该增量步内成为非线性弹性材料.该应力更新算法能使包括收敛解在内的迭代序列中不含虚假应变历史.此外,该算法还可避免静力解答精度依赖于静力增量步长的局限性.通过三个SHDM结构的数值试验对该算法进行了验证.该算法可望对SHDM结构非线性有限元静力问题DRM分析技术的发展起促进作用.

采用ABAQUS连接器单元模拟钢-混界面黏结滑移特性,并将预应力效应转化为界面法向力作用,建立了考虑法向力作用的钢板-混凝土界面黏结滑移试验的有限元模型,比较了试验和有限元模型的黏结滑移形态和黏结滑移曲线,分析了钢-混界面黏结滑移受力性能,研究了混凝土强度和法向力大小对界面黏结滑移性能的影响.通过有限元模型结果与试验结果,验证了该建模方法的有效性.结果表明:ABAQUS连接器单元能比较合理地模拟钢板-混凝土界面的黏结滑移性能;法向力对界面峰值黏结力和残余阶段黏结力影响显著,但对峰值滑移量影响较小;混凝土强度显著影响峰值黏结力,但对峰值滑移量和残余黏结力影响较小;所得结论可为钢-混界面黏结滑移性能研究的有限元建模及黏结滑移关系选择提供参考.

合理的理论模型对于结构分析至关重要,摇摆结构理论研究中应用最为广泛的模型是摇摆刚体模型.该文对摇摆结构刚体模型进行了较为系统考察与总结,对摇摆刚体模型的研究起源与研究现状进行了介绍,针对经典摇摆刚体模型、其他典型摇摆刚体模型、相关试验研究、有限元模拟及其在结构体系中的应用进行了探讨,指出了已有模型的优点与局限性,提出摇摆结构刚体模型未来研究的关键问题,为建立更完善实用的摇摆结构刚体模型及应用于摇摆结构分析提供了参考.

Taking the steel-concrete interface in prestressed steel reinforced concrete as the background,this paper aims at establishing a bond-slip constitutive relation for the interface including the effect of studs.Therefore,orthogonal bond-slip tests of eighteen steel-concrete interface specimens were conducted with concrete strength,amount of studs,and normal compressive stress as the variables.The tested interface was taken as an element of the prototype interface small enough to represent its behavior as a point in the element region,so that in this sense the bond-slip behavior at a point can be investigated.The bond stress-slip curves were obtained.Results show that,in the later stage of the test,all the studs are sheared off the steel plates causing a sudden drop in bond stress.The increase in concrete strength and normal compressive stress can both improve the yielding,peak and residual bond stresses of the interface.Although the studs show little effects on yielding and residual bond stresses,they can help increase the peak bond stress,the peak point slip,and the slip at the onset of the residual stage,making the interface failure more ductile.Based on the test results,bond-slip constitutive models for steel-concrete interfaces without studs,with one stud,and with two studs were proposed in which the formulas for characteristic bond stresses and characteristic slip values were determined by statistical regression.The proposed model is in good agreement with the experimental dada and therefore can be used to simulate the bond-slip behavior between steel and concrete including the effect of studs.

An experimental study was conducted to investigate the behavior of prestressed steel reinforced concrete (PSRC) frame beams subjected to vertical cyclic loading. Two one-fifth-scale specimens respectively with unbonded (UPSRC) and bonded (BPSRC) tendons were tested. The failure modes, skeleton curves, ductility, deformation restoring capacity and energy dissipation capacity were discussed. Results implied that the PSRC frame beams showed a typical beam hinge failure pattern. The ductility coefficients of UPSRC and BPSRC are 2.91 and 2.84, indicating that prestress tendon form (unbonded/bonded) seems to exhibit little influence on the ductility of PSRC frame beams. The downward deformation restoring capacity of UPSRC was superior to BPSRC and the residual deflection corresponding to service load (260 kN) were respectively -1.2 mm and -3.8 mm. The amount of energy dissipated by UPSRC was equivalent to that by BPSRC under the vertical cyclic loading. Moreover, twenty-six specimens were designed for numerical analysis to investigate the effects of parameters, including the amount of rebar and steel shape, concrete strength, and initial effective prestress, on the vertical seismic performance of PSRC frame beams.

结构静力分析中常因材料应变软化使得相应定解问题失去适定性,从而导致有限元分析不收敛.为解决此问题,在已有的相关研究基础上,采用动力松弛法(DRM)求解结构非线性有限元静力分析的增量步,将其应用于损伤型本构所描述的结构软化问题.本文方法依据两个原理,其一是苏联《数学百科全书》论述的原理——定义于时间域的任何定解问题适定可解,其二是DRM所用的原理——质量系统静力解为相应动力解的稳态部分.且DRM无需进行隐式静力分析时的总体刚度矩阵组装和求逆计算.本文用加荷载增量求解静力平衡路径硬化段,用加位移增量求解极值点和软化段.数值试验表明,本文方法能完成应变软化类结构的静力平衡路径求解.

为了研究预应力型钢混凝土(PSRC)结构在竖向地震作用下的抗震性能,完成了在梁中设置有粘结和无粘结预应力筋的两榀预应力型钢混凝土框架在竖向低周反复荷载作用下的试验研究,并采用ABAQUS有限元模型对试验曲线进行数值模拟.试验所得滞回曲线基本继承了型钢混凝土结构滞回曲线饱满的特点,并且有着预应力混凝土结构滞回曲线的捏拢效应.研究结果表明该结构形式具有较高的承载能力,优异的抗裂性能及裂缝闭合能力,以及较好的耗能能力和变形延性.ABAQUS计算所得滞回曲线与试验结果符合程度较好,模拟得到了滞回曲线的捏拢效应以及荷载下降段,说明了计算模型的可靠性,特别是所采用的损伤因子计算方法的可行性.

In order to deal with the divergence and instability due to the ill-posedness of the nonlinear finite element (FE) model of strain-softening structure in implicit static analysis, the dynamic relaxation method (DRM) was used with kinetic damping to solve the static increments in the incremental solution procedure so that the problem becomes well-posed. Moreover, in DRM there is no need to assemble and inverse the stiffness matrix as in implicit static analysis such that the associated computational cost is avoided. The ascending branch of static equilibrium path was solved by load increments, while the peak point and the descending branch were solved by displacement increments. Two numerical examples illustrated the effectiveness of such application of DRM in the FE analysis of static equilibrium path of strain-softening structures.

According to the assumption that the average strains of steel bars between cracks agreed with the plane section assumption,considering that the prestressing tendons and non-prestressing steel bars were in the same and different horizontal locations respectively,the tensile strain lagging coefficients of post-tensioned bonded prestressing tendons at cracking section were deduced in detail.Combined with the pervious code comparative results of stiffness calculation,referring to the calculating model of stiffness with good precision,and according to lots of deflection test data,the stiffness formula of concrete beams was proposed considering the tensile strain lagging of prestressing tendons.Results show that the values calculated by the suggested stiffness formula all agree well with the test values of reinforced and various prestressed concrete beams,thus the stiffness formulae of reinforced and prestressed concrete beams are unified.Compared with the stiffness formula in the current code for design of concrete structures,the suggested stiffness formula has higher calculating precision especially for the post-tensioned bonded and unbonded prestressed concrete beams,which can provide reference for code modification.

主要研究了梁中施加无粘结预应力的型钢混凝土(UPSRC)框架在竖向反复荷载下的抗震性能.先通过已有试验对本文ABAQUS有限元建模手段进行校准,然后利用该方法模拟得到了11榀UPSRC框架在竖向反复荷载下的荷载-挠度滞回曲线,并从强度、耗能、延性以及刚度退化等方面分析了UPSRC结构竖向抗震性能的特点以及梁中纵筋配筋率、力筋配筋率以及型钢含钢率对各抗震性能指标的影响.

采用基于割线刚度的等效线性化方法拓展了次弯矩概念,使其能够运用于非线性阶段.进行了4根无粘结预应力混凝土两跨连续梁受力全过程试验.研究结果表明,运用等效线性化方法可以将连续梁非线性阶段的支座反力分解成为预应力等效荷载引起的以及外荷载引起的两个部分,从而分离出次弯矩和外荷载弯矩.非线性阶段,无粘结预应力连续梁的次弯矩随预应力筋拉力的增长而增长.次弯矩折减系数随中支座截面受压区相对高度的增大而增大.承载力极限状态,非线性次弯矩在数值上大于初始次弯矩.

非线性阶段次弯矩的演化,以及承载力极限状态下是否考虑次弯矩的问题一直存在争议.为解决这一问题,拓展了预应力次弯矩的概念,使其能够适用于非线性阶段.运用变刚度法数值模拟了初始次弯矩(M2)与弹性最大荷载弯矩(Me)之比为0.15 ～0.36的15根有黏结预应力混凝土两跨连续梁.基于拓展后的次弯矩概念,提出了以混凝土受压区相对高度、初始次弯矩与弹性最大荷载弯矩之比为影响参数的有黏结预应力混凝土连续梁弯矩调幅公式.采用已有文献中受压区相对高度为0.35的试验梁比较了所提公式和现有的弯矩调幅公式.设计制作受压区相对高度为0.18的两跨预应力混凝土连续梁,获取单调加载下支座反力数据,检验了内力重分布程度较大时所提公式的效果.结果表明,给出的弯矩调幅公式的计算结果偏于安全,且更接近试验结果.

The concept of equivalent load has been widely used in research and design process of prestressed structures. According to the classical definition of equivalent loads, the topic was discussed whether the equivalent loads would be changed after linear transformation. It was pointed out that the stiffness of the net section should be used when equivalent load method was applied to calculate the camber value of prestressed concrete flexural members in service stage. To clarify some specious viewpoints in engineering, it was proved that the equivalent load method could be used to calculate prestressing actions for any tendon profile, including the profile of straight line and parabola combinations, and the related limitations of equivalent load method does not exist. In order to answer the question whether the equivalent loads would be changed or not with the increase of tendon stress in unbonded and boned prestressed structures, a new concept called current equivalent load was proposed, and the computational method of current equivalent load in prestressed structures was then established. Equilibrium equations of the ultimate limit state based on the current equivalent load concept were established. The equivalence between these equations and the traditional equilibrium equations in which prestressing tendons were treated totally as resistance material was proved. Finally, the superiority of the current equivalent load method was addressed as it is used to calculate deformation of the prestressed structures in the nonlinear range.

完成4根无黏结预应力混凝土两跨连续梁受力全过程试验,对支座反力及控制截面弯矩重分布程度进行分析.运用非线性阶段的预应力次弯矩定义,将非线性阶段连续梁总弯矩分解成次弯矩和荷载弯矩.研究加载全过程次弯矩和荷载弯矩的演化规律,提出了对初始次弯矩和弹性荷载弯矩分别调幅的无黏结预应力混凝土连续梁弯矩调幅公式.采用已有文献中一组试验梁对所提公式的计算精度进行验证.研究结果表明,无黏结预应力连续梁弯矩重分布的原因可以归结为无黏结筋应力的增长以及连续梁各部分割线刚度比值的改变.承载力极限状态下,次弯矩折减系数随中支座综合配筋指数的增大而增大,荷载弯矩调幅系数随其增大而降低.文中弯矩调幅建议公式较已有公式更接近试验结果,可为设计规范中相关条款的制订提供参考.

The internal forces in a prestressed concrete structure are of special nature due to the existence of tendons. And flaws can be found in the traditional concept of secondary moment such that common computation method of secondary moment may produce unreasonable results. This article aims at getting a better understanding of internal forces in prestressed structures and solving the relevant problems. Starting from the basic principles of internal force analysis, a new system of internal forces is put forward by which the relationship between the compression resultant on concrete cross-section and the sectional internal forces is made clear. On this basis, a definition on the concept of current secondary moment (M-cs) is proposed and its superiority pointed out. Finally, theoretical analyses are carried out on the method for calculating M-cs in the posttentioned continuous beams with unbonded and bonded prestressing tendons.

The influence of several parameters of bonded prestressed concrete beams on its moment-curvature relationship is researched.Through carrying out FEM analysis of bonded prestressed concrete beams with different parameters,the corresponding moment-curvature relationship can be got.Subsequently a simplified trilinear model is obtained specially for the influence of eccentricity combining with theoretical derivation,which is convenient to be used.

This article introduce the applications of the prestressed steel reinforced concrete structure in the engineering in China′s earthquake zone.It synthesizes the existing seismic performance research of prestressed steel reinforced concrete structure,focuses on the existing experimental research phenomenon to investigate the failure mode,carrying capacity,deformation recovery capabilities,ductilitystiffness degradation and energy dissipation capacity and other seismic performance and mechanism of action.It combines the available elastoplastic seismic response analysis of the prestressed steel reinforced concrete structures,discusses structure restoring force model obtained from hysteresis curves and skeleton curves,studies the structure response of the whole process in the earthquake and its failure mechanism to estimate the seismic capacity.

Twelve push-off specimens were designed,constructed,and tested.Test variables included reinforcement ratio of shear reinforcement,interface preparation,loading method and eccentricity of applied load.The failure pattern,hysteretic characteristics and degradation characteristics of bearing capacity and stiffness were analyzed.The effect of each test variable on interfacial shear capacity was studied.Results show that the failure pattern of test specimens under cyclic reversed loading is typical shear failure.The order of main factors influencing interfacial shear capacity is interface preparation,shear reinforcement ratio,loading method and loading eccentricity in turn based on test results.Cyclic reversed loading reduces interfacial shear capacity.The reduction is smaller for monotonic interfacial shear strength.But for new and existing concrete interfaces,the reduction is bigger and can not be neglected.Based on the test results and the available data,a calculation method for interfacial shear capacity of a RC member was proposed.The calculated results show good agreement with the test results on the basis of comparison with test values and calculated values of other calculation formula.

Fourting concrete beams reinforced with 500MPa longitudinal steel bars, of which 6 with skin reinforcement and 8 without skin reinforcement, were tested under two-point symmetrical concentrated static loading to investigate their crack patterns. Crack distributions in constant moment region of beams are compared. The propagation of side cracks along the beam depth is obtained. The results of this study indicate that the concrete cover of longitudinal tensile steel bars and the spacing of skin reinforcement has significant effect on crack distributions; substantial crack control in beams can be achieved if the spacing of skin reinforcement is limited to certain critical values. The curve of d-w(d is the distance between observation points of side cracks and tension face of beams, w refers to crack width at observation points) is approximately characterized by a zig-zag shape and concave-left near longitudinal tensile steel bars.