This paper is concerned with the design of observers for a linear system with time‐varying delay in the field of structural control. A class of sliding mode observers with state and input time‐varying delays is developed on the basis of the coordinate transformation and free‐weighting matrix methods. The exponential dynamic properties of the observers are introduced to improve the performance of the observer. The delay and delay‐rate dependent conditions formulated by linear matrix inequalities (LMIs) are proposed to obtain the gains of the observers. Then, the bisection method is proposed to obtain the maximum exponential decay rate and allowable time delay. Finally, a numerical example of a fourth‐order system is used to show the feasibility and efficiency of the proposed observer.

Viscoelasticity is an important characteristic of gussasphalt mixtures. The aim of this study is to find the correct viscoelastic material parameters of the novel gussasphalt applied in the 4th Yangtze River Bridge based on the modified Burgers model. This study firstly derives the explicit Prony series form of the shear relaxation modulus of viscoelastic material from Laplace transformation, to fulfill the parameter inputting requirements of commonly used finite element software suites. Secondly, a kind of uniaxial penetration creep experiment on the gussasphalt mixtures is conducted. By fitting the creep compliance, the viscoelastic parameters characterized by the modified Burgers model are obtained. And thirdly, based on the viscoelastic test data of asphalt mixtures, the Prony series formula derived in this study is verified through the finite element simulation. The comparison results of the relative errors between the finite element simulation and the theoretical calculation confirm the reliability of the Prony series formulas deduced in this research. And finally, a stress-correcting method is proposed, which can significantly improve the accuracy of model parameters identification and reduce the relative error between the finite element simulation and the experimental data.

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<p>The stay cables are usually subjected to continuous erosion from the environment in their service period. The protective layer on the cable wire is an important barrier for the cable corrosion resistance. Therefore, the durability of the cable depends greatly on the proper selection of the protective layer, which makes a big difference comparing with the bare cable wires. This paper studies on the corrosion performance of 6 common kinds of cable steels under the same corrosion environment with electrochemical test methods. The corrosion rates of different kinds of steel bars under various covers are tested and obtained. The results can provide more accurate reference for the designers of cable stayed bridges to selecting a proper kind of cable wires during the bridge construction or maintainers to estimate the durability of the stayed cables.</p>

<p>The influence of vehicle load on the force state of the paving layers for orthotropic steel decks in different seasons was studied in the research. To begin with, by applying the fourth Nanjing Yangtze River Bridge as the research object, this research established the model for the half cross-section of steel box beam (MHCSBB) using the ANSYS finite element software. Then, the finite element method was used to calculate the position which is most adverse for the force of the pavement layers under loading at different positions. Meanwhile, the influences of varying temperatures in different seasons and different overload proportions (30%, 50%, 70% and 100%) on the force state of the pavement layers were taken into account. Based on this, this research comprehensively analyzed the characteristics of the varying forces of the orthotropic steel deck under different vehicle loads. Finally, it was obtained that vehicle overloading should be effectively controlled under the conditions of low and high temperatures, so as to improve the force state and thus lengthen the service life of the pavement layer of the steel deck.</p>