The weak parts of shield tunnels are not obvious, so it is urgently necessary to implement distributed monitoring based on an advanced sensing method. As the horizontal loads at both sides of the shield tunnel present a type of symmetric distribution, the deformation parameters under the vertical loads are often selected as the key monitored parameters, such as convergence, settlement, and seam opening. In this paper, the monitoring of the proposed deformation parameters is innovatively implemented with only one sensing technology, namely distributed optical-fiber strain sensing technology. First, the improved distributed optical-fiber sensors are introduced with the sensing performance. Second, a structural health monitoring (SHM) system for operational shield tunnels is proposed, including optical-fiber sensor installation, data logging and saving, key parameter analysis, and structural health assessment. The key monitoring theory and technology are also proposed. The proposed system has been verified by experiments at the Nanjing Yangtze River tunnel. In the experiments, the proposed optical-fiber sensors were installed on the surface of a selected tunnel ring, with a longitudinal span of approximately 90 m long. The experiments were conducted over 55 days to measure the distributed strain and temperature. Then the key parameters were obtained from the measurements, with which the structural health was assessed. The possibility that the shield tunnel SHM system can be constructed with the improved distributed optical-fiber sensors, monitoring theory, and technology is proven.

The interval finite element method based on the element-by-element technique is proved to be a rigorous and efficient method for considering interval uncertainties. The structural internal force of the same accuracy as the interval response displacement can be obtained by combining the variational method and the Lagrange multiplier method. However, the increase of the Lagrange multiplier reduces the efficiency of solving the equation, especially for a large truss system. In addition, the method is mostly used to analyse truss system, and the applications in plane problems are still rare. In this article, an improved method involving modification of the Lagrange multiplier interval equations is proposed to calculate interval displacements and interval internal forces at the same time. In this proposed method, the increase of the unknown Lagrange interval does not affect the solution of the equations. For plane problems, a new method for solving the stress interval of the element is proposed. This proposed method can effectively reduce the expansion of the stress interval of the element. Finally, the correctness and rationality of the proposed method are verified by numerical examples.

Assuming that the baseband OFDM signal is characterized as a band-limited complex Gaussian process,the distribution of the peak-to-average power ratio (PAPR) in band-limited OFDM signals is investigated in this paper.Based on the level-crossing rate theory,a simple closed-form upper bound on the PAPR distribution of a band-limited OFDM signal is proposed.For the 16QAM-OFDM systems with different subcarrier number,the Monte Carlo simulation of the PAPR distribution is performed to test the tightness of the proposed upper bound.The simulation results show that the proposed upper bound matches the simulation results well when the subcarrier number is greater than or equal to 64.However,the upper bound is not tight when the subcarrier number is 32.In addition,instead of the actual PAPR being directly proportional to the subcarrier number,the research indicates that the probability that the PAPR is greater than a given value y is directly proportional to the subcarrier number N. When the subcarrier number is large,the dominant effect is the stochastic behavior of the OFDM signal and also this shows that the stochastic description of PAPR distribution is quite important.

This paper addresses the problem of open gaps caused by differential settlement in the process of constructing sluice buildings in soft soil beach areas, combined with the construction of sluice and supporting facilities in a reclamation project. First, the change rules for the shear strength and compression modulus of soft soil under different consolidation degrees are studied by theoretical analysis. Then, an interaction model for soft soil and pile soil is established using the geotechnical finite element analysis software MIDAS/GTS NX. The change rules for the vertical and horizontal ultimate bearing capacities of a single pile with the degree of soil consolidation are studied. On this basis, a three-dimensional numerical analysis model of drainage sluice, seawall, cofferdam, and foundation soil is established, and the relationship between the degree of soil consolidation and the development of structural gaps caused by differential settlement is obtained. The research results show that the bearing capacity of a single pile increases greatly with the consolidation of soil around the pile and that the gap width between the structures in the project decreases with increasing consolidation. This paper provides a theoretical basis for the prediction of pile bearing capacity in the preliminary design stage and the evaluation and calculation of differential settlement of intersecting buildings in soft soil beach areas.

In this article, the dependency between different elements in solid structures is considered and a substructure-based interval finite element method is used to model the interval properties. The penalty method is applied to impose the necessary constraints for compatibility. In order to obtain the interval stresses, an approximation solution based on the Taylor expansion method is presented. Then, the proposed interval substructure model is expanded to nonlinear problems. In consideration of the nonlinear property of the elasticity modulus, an interval elastoplastic substructure analysis method using constant matrix based on the incremental theory is proposed and the interval expression of the interval stress updated formation is derived. Finally, numerical examples are carried out to demonstrate the reasonability and feasibility of the proposed method and evaluation system.