Discussion of the Stiffness Reduction Factor of Bent-columns

The simplified structural analysis and design method employing stiffness reduction of member bars,has been accepted by Chinese Standard, in which second-order effects already been considered through elastic finite element analysis,and its accuracy mostly depends on the rationality of the stiffness reduction factor.Due to the absence of investigation in the stiffness reduction factor of bent frame,according to the non-linear finite element analysis of several single-story single-span bent frames,the stiffness reduction factor of bent-columns has been suggested.And the rationality of this factor has been proved by comparison of the internal force in bent-columns and displacement of bent frames in second-order elasticity analysis and non-linear finite element analysis.     

An improved method for and error evaluation of modal pushover analysis

Based on evaluation of the basic principle and error of the modal pushover analysis method, an improved method is suggested by selecting rational values of stiffness reduction parameters of beams and columns in a reinforced concrete frame corresponding to the global target displacement ductility ratio. A 10 story and a 16 story reinforced concrete plane frame are designed as examples to investigate the influence of higher modes. Nonlinear seismic responses of the two frames under excitations of seven earthquake waves of varying earthquake intensities are selected to be the reference points for a comparison study. The changing rules of the results of modal pushover analysis and modified modal pushover analysis with respect to various natural fundamental periods and different earthquake intensities are studied. Research results show that the error of modal pushover analysis and modified modal pushover analysis will not increase with a larger fundamental period, which implies that modal pushover analysis can cover the effect of higher modes reasonably. When the degree of nonlinearity of the structure is more severe, the modified modal pushover analysis we suggest could decrease the error of normal modal pushover analysis to a certain extent.     

Numerical Simulations and Design Method of Coupled Wall System with FRC Coupling Beams

Using the software, ABAQUS, accurate simulations of seismic behavior of 2 coupled wall specimens and 2 cantilever structure wall specimens using high performance fiber reinforced concrete (FRC) in plastic hinge under quasi static cyclic loading were carried out. The analysis model proves to be effective with the accordance between results of computation and experiment, then it can be used to analyze the seismic behavior of coupled wall system with FRC coupling beams. By using the verified numerical model, the ability of FRC coupling beams instead of RC coupling beams to provide acceptable performance was discussed. In addition, the impact of coupling ratio on seismic behavior of coupled walls was studied. The results show that coupled walls in which FRC coupling beams are used instead of traditional RC beams have good energy dissipation and ductility, and its initial stiffness is increased and stiffness degradation is slow. And as the coupling ratio of coupled wall structures increases, the stiffness and strength increase. But if the coupling ratio is too large, the ductility and energy dissipation capacity will be significantly reduced.     

基于内聚力模型的锈蚀砼梁抗弯刚度

粘结性能退化是导致锈蚀钢筋混凝土构件力学性能下降的主要因素之一,基于锈蚀构件粘结性能实验研究成果与内聚力模型,建立了有厚度的双线性内聚力单元与分离式钢筋混凝土梁分析模型,引入粘结界面层,研究了粘结性能退化对锈蚀钢筋混凝土梁抗弯刚度的影响。结果表明,双线性内聚力单元可以有效模拟钢筋与混凝土之间的粘结机制,而根据锈蚀深度确定的有厚度的粘结单元能合理描述锈蚀程度对粘结性能的影响。数值分析结果与实验及经验公式对比,表明了文中方法的有效性和合理性。     

Axial Force Stiffness Interaction in Seismic Analysis of RC Double Column Bridges

Earthquake induced dynamic axial force in reinforced concrete (RC) bridge bent columns will not only change the yield strength of the columns but also change their stiffness, which is seldom considered by the common lumped plasticity line model. Based on the fiber element model results that taking into account the influence of dynamic axial force on strength and stiffness simultaneously, the axial force stiffness interaction effect on the seismic responses of RC double column bridges was analyzed. The results show that, axial force stiffness interaction has a large effect on the seismic responses of the double column bridge in the elastic range, and it does not alter the ultimate capacity of the columns. Since the stiffness of the columns under compression and tension dynamic axial forces offset each other, the global displacement of bridge bent with equal columns is relatively unaffected by the axial force stiffness interaction, however, the differences of the column member forces are manifest. For the short column controls the global stiffness, the axial force stiffness interaction has significant influences on both the global displacement and member force responses. The influences become larger as the irregularity of the bridge bent increases, so the interaction between axial force and member stiffness should be sufficiently considered in seismic analyses.     

Elemental Stiffness Matrix of Thin-walled Beam and Its Application

In this paper, according to the conception of rotation of the section orthographic projection around a fixed axis, the element stiffness matrix of thin-walled beam is directly deduced and the direct stiffness method is used to solve the continuous beam problem with different shear centers on one section. It is suggested through an example that when the element flexibility matrix and force method are used to solve the same question, the same answer will be gained, but the method used in this paper is simpler.     

渐变刚度钢板弹簧建模方法对比

为更好地分析钢板弹簧刚度特性,对钢板弹簧建模方法进行了对比研究。依据钢板弹簧国家标准GB/T 19844-2005,针对某型渐变刚度钢板弹簧分别在有限元软件Hypermesh和多体动力学软件Adams中建立其有限元模型和离散梁模型,并进行了仿真,得到刚度特性。将仿真结果与试验值进行了比较。结果表明,在针对该钢板弹簧的刚度分析中,运用离散梁法得到的刚度特性更加接近试验值。     

Analysis on Seismic Capacity for RC Specially Shaped Columns in Different Horizontal Direction

With fiber beam-column element based on flexibility method of finite element, the RC specially shaped columns of different axial compression ratio under cyclic loading have been simulated and the analysis results have been compared in aspects of strength, stiffness and ductility in order to provide some suggestions for seismic-resistant design of specially shaped columns. The strength, stiffness and ductility of L,T-shaped columns are apparently different in different horizontal direction, but those of t-shaped column are close.     

Post-earthquake Residual Deformation Prediction of SDOF System

Accurately predicting the residual displacement of reinforced concrete (RC) structures after an earthquake is of great significance in post-earthquake structural performance evaluation and control. To study the residual deformation of the structure, seismic time-history responses of single degree-of-freedom (SDOF) systems with different parameters were analyzed. Based on the analytical results, simplified models for estimating the likely residual deformations of structures characterized by Takeda and Kinematic hysteretic models were proposed respectively, and the residual deformation was found to be sensitive to hysteretic characteristics, stiffness ratio of structures, peak ground acceleration (PGA), as well as maximum elasto-plastic deformation. A case study for RC single-column bridge pier was provided to illustrate the process of residual deformation calculation and post-earthquake performance evaluation by using the proposed methods. Calculation results indicate that the residual deformation of the single-column pier characterized by the Takeda model often is much larger than that of columns characterized by the Kinematic model.     

Experimental Study on Flexural Behavior of Reinforced Concrete Beams Strengthened With Ferrocement Mortar

Experimental research on flexural behavior of the different grade RC beams strengthened with ferrocement mortar through six RC beams is carried out. The matching of original component concrete to the composite mortar strength rank is studied and its influence on bending strength, the crack-resisting capacity and the bending stiffness of RC beams is analyzed. Based on plane cross-section assumption and the experimental results, the formulas of the theoretical ultimate strength capacity and stiffness are brought forward. The calculated results fit well with the experimental results, to provide a theoretical reference for actual engineering designs.     

The Research on Stiffness of Double Involute Gear with Ladder shape Teeth

The stiffness of the tooth with different profile parameters,meshing stiffness and the coefficients of loading distribution allowing for no error are calculated and analyzed on double involute gear with ladder shape teeth for the first time,and the results are made comparison with traditional involute gear;The stiffness of the double involute gear and the meshing stiffness are both increased,and the coefficients of loading distribution are basically unchanged.The energy integration method is also put forth to solve stiffness approximately by linear approximating the tooth profile curve.     

The Stiffness Analysis and the Design Method of a Kind of Automobile Hydro-Pneumatic Suspensionwith High Lateral Stabiiity

A kind of hydro-pneumatic suspension with high lateral stability was in treducedin this paper.Analysis were made to its vertical linear stiffness properties and laternal angular stiff-ness properties. On the basis of the analysis,the formulas of its design calculation and method werepresented here.     

混凝土密柱石膏复合墙板结构性能及简化分析模型

对混凝土密柱石膏复合墙板的水平剪力传递机理进行分析,发现石膏板肋能有效地在混凝土芯柱间传递水平剪力,对复合墙板结构性能有较大影响。在此基础上,提出混凝土密柱石膏复合墙板的等效带缝剪力墙简化分析模型,剪力墙竖缝布置以保证等效带缝剪力墙与复合墙板具有相同弹性抗侧刚度为原则确定。对混凝土密柱石膏复合墙板及等效带缝剪力墙的结构性能进行比较分析表明,混凝土密柱石膏复合墙板与带缝剪力墙受力机理相似,等效带缝剪力墙弹性及塑性阶段都能很好地反映混凝土密柱石膏复合墙板的结构性能。     

Convergence and Stability of Newmark Method in Case of Negative Stiffness

The convergence and stability of Newmark method has been studied in this paper for the model with the negative stiffness. In the case of negative stiffness, the method is convergent and conditionally stable.     

COMPUTATION OF DISPLACEMENTS AND STRESS-RESULTANTS OF SEMI-RIGIDLY CONNECTED FRAMEWORKS

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.     

大白菜萝卜胞质雄性不育系RC7单株产种量构成因素分析

应用线性回归和相关分析的方法,研究了新育成的大白菜萝卜胞质雄性不育系RC7的单株产量构成因素及其相关性,研究结果表明:不育系RC7的单株有效角果数(r=0.96583**)、二级分枝数(r=0.96419**)、每果粒数(r=0.75701**)、主花序有效角果数(r=0.49024*)及主花序有效长度(r=0.40623*)与单株产种量之间存在极显著或显著的正相关关系。在此基础上,建立了不育系RC7及其保持系单株种子产量的多元线性回归方程。在利用该不育系制种过程中,栽培管理上应以增加分枝数,尤其是二级分枝数,作为高产的主攻方向。     

Design of a Kind of Blood Pressure and Artery Stiffness Measuring Apparatus

Blood pressure and artery stiffness are very important physical parameters and the measure to them is very important in clinic.This paper discribes the design of a kind of blood pressure and arterial stiffness measuring apparatus .The measuring algorithm based on oscillometric method is also discussed.The apparatus inherits the merits of traditional blood-pressure meter,it can measure blood pressure and heart beat rate.Furthermore,it can give the information of the measurer's arterial stiffness and provides reference to doctor to determine the measurer's cirrhosis level .     

Effects of cover displacement functions for the stiffness matrixof the numerical manifold method

Based on basic theory of numerical manifold method, effects of cover displacement functions for the stiffness matrix is analyzed with the relationship between the cover displacement function and the formation of the stiffness matrix. The increasing speed of matrix element value has relation to the values of absolute coordinates in cover displacement function. An improved function is adopted for better solution to solve partial oversize problem of stiffness values in the stiffness matrix with the high order cover displacement function. The validity of the proposed approach is approved with case study.     

软母线刚度对特高压电气设备地震响应影响分析

为研究软母线刚度对特高压电气设备地震响应的影响,建立考虑刚度的软母线位形函数、最大弧垂及软母线最大应力的计算公式。通过软母线连接的特高压设备振动台模型试验与有限元计算的对比分析,验证了笔者给出的考虑刚度的软母线位形函数、最大弧垂计算公式的正确性。有限元分析结果表明:当软母线的刚度增大时,软母线的垂跨比减少,软母线与特高压设备之间的地震耦合作用增强,增强了软母线对设备的拉伸作用,从而使设备的地震反应随着导线刚度的增加而增加。软母线刚度对频率较高的设备其地震反应的影响要大于对设备频率较低设备地震反应的影响。     

预应力CFRP布及预紧螺栓加固RC梁试验研究

为提高碳纤维布加固RC结构的效果及其可靠性,提出了预应力碳纤维布与预紧螺栓联合加固技术。结合在役RC梁的损伤特点及目前的RC梁加固方法,分别采用不同的碳纤维布加固技术对完整梁和破坏梁的抗弯性能进行了对比试验研究。针对目前碳纤维布张拉设备的缺陷,研发了便于现场应用的新型碳纤维布布张拉设备,分析了预应力大小对加固效果的影响。结果表明,预应力碳纤维布及预紧螺栓联合加固技术是一种更可靠的桥梁加固方法,不仅能够提高RC梁正截面的抗弯承载能力及正常使用阶段的截面刚度,而且螺栓预紧锚固碳纤维布能够很好地抑制其在混凝土表面的剥离,提高碳纤维布与混凝土表面之间粘结强度,对碳纤维布施加预应力能够充分发挥其高强性能,有效抑制混凝土裂缝开裂和开展。