This paper develops an improved analytical algorithm on the main cable system of suspension bridge. A catenary cable element is presented for the nonlinear analysis on main cable system that is subjected to static loadings. The tangent stiffness matrix and internal force vector of the element are derived explicitly based on the exact analytical expressions of elastic catenary. Self-weight of the cables can be directly considered without any approximations. The effect of pre-tension of cable is also included in the element formulation. A search algorithm with the penalty factor is introduced to identify the initial components for convergence with high precision and fast speed. Numerical examples are presented and discussed to illustrate the accuracy and efficiency of the proposed analytical algorithm.

Low-coherent fiber-optic sensors combined with neural network algorithms were designed to carry out a load-sensitizing spherical bearing. Four sensing fibers were wound around the outside of the pot support of the spherical bearing uniformly deployed from upper to bottom. The upper three were configured in a distributed way to respond to the applied load as a function of the three strain sensors. The bottom one was employed as a temperature compensation sensor. A loading experiment was implemented to test the performance of the designed system. The results showed that there was a hysteresis in all the three sensors between loading and unloading process. The neural network algorithm is proposed to set up a function of the three sensors, treated as a set of input vectors to establish the input-output relationship between the applied loads and the constructed input vectors, in order to overcome the hysteresis existing in each sensor. An accuracy of 6% for load sensing was approached after temperature compensation.

This paper develops a new symplectic eigenvalue analysis (SEA) method for deriving the symplectic analytical solutions for the bending of Timoshenko beams resting on two-parameter elastic foundations. The SEA method accommodates various beam–foundation models with arbitrary external loads and arbitrary boundary conditions. A generalized Hamiltonian functional is first derived by introducing the Lagrange multipliers into the total potential energy functional, and then the first-order dual equation and its corresponding boundary conditions are obtained. Once the variables are separated, the beam bending is transformed into an eigenvalue problem, and the corresponding eigenvalues and eigenvectors are used to derive the symplectic solutions. In addition, a new hybrid method, which incorporates the singular functions and the variable separation method, is proposed to obtain the particular solutions with respect to arbitrary external loads. The systematic SEA method provides a new general analytical framework for studying beam–foundation interaction problems, and the comprehensive analyses on the symplectic eigenvalues help to deeply understand the characteristics of the symplectic solutions. Three examples are presented to assess the applicability of the SEA method and to validate the accuracy of the symplectic solutions. The differences and similarities between the Pasternak elastic foundation and the generalized elastic foundation are quantitatively and qualitatively investigated by the SEA method.

A fiber-optic low-coherent interferometry sensor was developed to measure the ground settlement (GS) in an accuracy of the micrometer. The sensor combined optical techniques with liquid-contained chambers that were hydraulically connected together at the bottom by using a water-filled tube. The liquid surface inside each chamber was at the same level initially. The optical interferometry was employed to read out the liquid level changes, which following the GS happened at the place where the chamber was put on and, thereby, the GS information was calculated. The laboratory effort had demonstrated its potential in the practical application. Here, the denoising algorithms on the measurement signal were carried out based on the specific environment to ensure the accuracy and stability of the system in field applications. After that, we extended this technique to the high-speed railway. The 5-days continuous measurement proved that the designed system could be applied to monitor the GS of the high-speed railway piers and approached an accuracy of ±70 μm in the field situation with a reference compensation sensor. So the performance of the sensor was suitable to the GS monitoring problem in the high-speed railway. There, the difficulties were to meet the monitoring requirement of both a large span in space and its quite tiny and slow changes.

This paper proposes a new symplectic method for obtaining the natural frequencies and modes of beams resting on elastic foundations. A generalized Hamiltonian functional is first derived via the Lagrange multiplier method, and the first-order dual equation of motion in the time domain and its corresponding boundary conditions are obtained. The time coordinate is separated from the dual equation to yield the natural-frequency-related eigenvalue equation and the first-order dual equation in the frequency domain. Then, the spatial coordinate is separated from the newly derived dual equation to yield the natural-mode-related eigenvalue equation. According to the eigenvalue analyses, this paper obtains a series of eigenvalue spectra: the continuous and discrete eigenvalue spectra that represent the relationships of the two types of dimensionless eigenvalues for infinite and finite beams, respectively; these eigenvalue spectra help to understand the connection between structural vibration and wave propagation. For a finite beam with a specific boundary condition, its mode vectors are composed of transverse deflection, bending rotation, shear force, and bending moment, and they are called the full mode shape vectors (FMSVs) in this paper. These FMSVs were verified to be orthogonal according to the property of the Hamilton matrix. A simply supported and a cantilever beam were used as examples to validate the accuracy and applicability of the symplectic method. Their vibration properties, mainly the discrete eigenvalue spectra and FMSVs, are comprehensively analyzed, and some significant conclusions are drawn.

In view of the first domestic offshore suspension bridge with caisson foundation, this paper mainly studies the bonding properties between underwater pre-filled aggregate grouting bed and anchorage caisson foundation. Through the test, the cohesive force of adding ordinary concrete between the anchorage caisson foundation and the grouting bed, the cohesive force of adding paper base asphalt felt between the anchorage caisson foundation and the grouting bed, and the cohesive force of adding geotextile between the anchorage caisson foundation and the grouting bed are measured, respectively. When the contact surface is concrete and geotextile, the fracture form of the specimen was analyzed by numerical simulation, and the AE variation trend of the two specimens have been studied. The results of this article can provide references for other projects.