Dynamic test methods for natural frequency of footbridge

Using environmental random vibration as the excitation,traditional accelerometer method,non-contact video method and non-contact laser method were employed to determine the natural frequency of Kunyu River footbridge.All the results of these three methods are close to 2.70 Hz,which are concordant with each other and hence credible.

朱熹对邵雍先天象数学的继承和发展

朱熹从探究《易》之本义的角度,继承和发展了邵雍的先天象数学,提出了《周易》本来是卜筮之书的思想,主张“三圣易”和经传相分,探析了河图、洛书及其关系,进而对伏羲画卦的内在机制以及大衍之数五十的来源做了阐释,从而不仅为象数易学增添了新内容,而且为学人提供了一种合理的解《易》方法。

论魏了翁的易学思想

魏了翁继承朱熹,兼重象数义理,以辞、变、象、占为《易》之纲领,力图融会程、邵易学。他深研邵雍易学,提出“性善之义具于《易》”,并对河图洛书、先后天易学源流及有关分歧作了进一步考证,得出图书相通的结论。魏了翁重世教,学术以济世为旨。

Model Reduction Methods for High-Rise Buildings with Active Mass Damper Control Systems

To improve the performance of an active mass damper control system,the controller should be designed based on a reduced-order model. An improved method based on balanced truncation method was proposed to reduce the dimension of high-rise buildings,and was compared with other widely used reduction methods by using a framework with ten floors. This optimized method has improvement of reduction process and choice of the order. Based on the reduced-order model obtained by the improved method and pole-assignment algorithm,a controller was designed. Finally,a comparative analysis of structural responses,transfer functions,and poles was conducted on an actual high-rise building. The results show the effectiveness of the improved method.

与图Zeta函数相关的一个函数的导数值

设G是含有n个顶点和ε条边的图,G的Zeta函数可以表示为ZG(u)=(1-u2)n-ε/f(u),其中f(u)=det(I-u A(G)+u2(D(G)-I)),A(G)与D(G)分别表示G的邻接矩阵与度对角矩阵。分别利用正则图的TU子图的权重ω和二部图的顶点数n和边数ε来表示相应的f'(-1)的值。

Performance Degradation Alarming M ethod Based on Local Flexural Stiffness Identification for Beams

Uncertain local flexural stiffness is recognized as one of the main barriers against the application of existing damage detection and performance degradation alarming techniques to real-world beams.Therefore,damage localization of beams with original uncertainty has been investigated to ensure their safety.For the beam before serving,it should be simply supported and subject to static load.Based on the concept of suppositional partition,a new loading pattern and mid-span displacement data processing method has been proposed.Actual local flexural stiffness value of each partition can be obtained by solving a set of linear equations.The obtained stiffness data can be used to establish the finite element model of beams.Subsequently,dynamic excitation and mode identification should be carried out for the beam in service.Mode shape curvature index is employed to detect the position of damage.It was validated by example that actual damage and original uncertainty of local flexural stiffness can be differentiated by this new method effectively.The combination of static load and dynamic excitation can keep the serviceability of beam.

Non-stationary Buffeting Response Analysis of Long Span Suspension Bridge Under Strong Wind Loading

The non-stationary buffeting response of long span suspension bridge in time domain under strong wind loading is computed. Modeling method for generating non-stationary fluctuating winds with probabilistic model for non-stationary strong wind fields is first presented. Non-stationary wind forces induced by strong winds on bridge deck and tower are then given a brief introduction. Finally,Non-stationary buffeting response of Pulite Bridge in China,a long span suspension bridge,is computed by using ANSYS software under four working conditions with different combination of time-varying mean wind and time-varying variance. The case study further confirms that it is necessity of considering non-stationary buffeting response for long span suspension bridge under strong wind loading,rather than only stationary buffeting response.

Large Deformation Beam/Cable Element with Implicit Kinematic Model

This paper proposes a 3D 2-node element for beams and cables. Main improvements of the element are two new interpolation functions for beam axis and cross-sectional rotation. New interpolation functions employ implicit functions to simulate large deformations. In the translational interpolation function, two parameters which affect lateral deflection geometry are defined implicitly through nonlinear equations. The proposed translational interpolation function is shown to be more accurate than Hermitian function at large deformations. In the rotational interpolation function, twist rate is defined implicitly through a torsional continuity equation. Cross-sectional rotation which is strictly consistent to beam axis is obtained through separate bending rotation interpolation and torsional rotation interpolation. The element model fully accounts for geometric nonlinearities and coupling effects,and thus,can simulate cables with zero bending stiffness. Stiffness matrix and load vector have been derived using symbolic computation. Source code has been generated automatically.Numerical examples show that the proposed element has significantly higher accuracy than conventional 2-node beam elements under the same meshes for geometrically nonlinear problems.

Design Capability Identify under Asymmetric Information

Under the condition of asymmetric information,the Spence 's Job Market Signaling Model is generally applied to inspect the design capability of a designer and his labor and efforts to be invested; however,since the"prior probability"and "posterior probability"have great uncertainties,the practical effect of this model is poor. On the basis of analyzing reverse selection questions,this paper provides a design capability screening model,which can make a designer automatically expose his hidden information so that necessary actions can be taken as required by the owner to realize risk sharing. A calculation example is finally given to demonstrate that the new model is helpful for an owner to select a designer with high professional level and to lead the designer to work hard,so it is of significant application value.

Arc-length technique for nonlinear finite element analysis

Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.

朱熹河洛思想演变历程再认识——兼论朱熹书信编年的相关问题

朱熹的河洛之学存在从“河九洛十”到“河十洛九”的转变历程。以往有研究认为,早在淳熙八年以前,这个转变已经发生。但学界对该认识所依据关键书信的编年尚有不同意见,除淳熙八年前之说外,还有淳熙十三年和十四年两种看法,朱熹河洛思想演变的历程问题仍有待发之覆。作于同一时期的其他书信显示,这通关键书信应作于淳熙十二年,可知此时,朱熹仍对北宋刘牧提出的“河九洛十”之说深信不疑。在蔡元定的影响下,朱熹开始考虑“河十洛九”的可能性。宋椠《晦庵先生文集》后集所收《易学启蒙》草稿中两说并存的情况,显示出淳熙十二年至十三年间朱熹在“河九洛十”与“河十洛九”之间徘徊的思想状态,这也是以往研究较少注意到的内容。淳熙十三年三月《易学启蒙》的序定,标志着朱熹彻底完成了“河十洛九”的转向。淳熙十二年至十三年三月应当是朱熹河洛之学发生转变的重要时期。