Graphene nanoplatelets (GNP) is a newly nanomaterial with extraordinary properties. This paper investigated the effect of GNP on the addition on freeze–thaw (F–T) resistance of concrete. In this experimental study, water to cement ratio remained unchanged, a control mixture without GNP materials and the addition of GNP was ranging from 0.02% to 0.4% by weight of ordinary Portland cement was prepared. Specimens were carried out by the rapid freeze-thaw test, according to the current Chinese standard. The workability, compressive strength, visual deterioration and mass loss of concrete samples were evaluated. Scanning electron microscopy also applied in order to investigate the micromorphology inside of the concrete. The results showed that GNP concrete has a finer pore structure than ordinary concrete; moreover, the workability of GNP concrete reduced, and the compressive strength of specimens was enhanced within the appropriate range of GNP addition; in addition, GNP concrete performed better than the control concrete in the durability of concrete exposed to F-T actions. Specimens with 0.05% GNP exhibited the highest compressive property after 200 F–T cycles compared with other samples.

This paper presents comprehensive results on the mechanical behavior of submarine steel pipelines subjected to various strike-slip fault displacement loads. The investigation uses strain-based criteria to estimate pipeline performance based on rigorous numerical modeling and simulation of a soil–pipe system, accounting for nonlinear material behavior and large strain of both pipeline and surrounding seabed soil. Equivalent boundary conditions are derived and applied at both ends of the pipeline to take the effect of pipeline segments far away from the fault into account. Parameters affecting the response of submarine pipelines subjected to active faults (including pipe diameter, diameter-to-thickness ratio, burial depth, soil stiffness, and intersection angles) are studied. A uniform design experiment is also carried out to predict the critical fault displacement. The results show that the segments of the pipe embedded in both blocks near the fault plane are critical locations where buckling or rupture is more likely to occur. The ability of the pipeline to withstand more fault displacements can be enhanced by increasing the diameter and wall thickness. In addition, the choice of proper burial depth and differential pressure can lead to an increase in flexural stiffness and weaker soil–pipeline interaction. Pipe diameter, crossing angles, and burial depth determine the pipeline’s failure modes. An accurate regression derived from finite uniform design experiments is proposed for the performance-based design of future submarine pipelines.

A pulse-like ground motion identification method is proposed based on the Siamese Convolutional Neural Networks (SCNNs). The wavelet coefficient graphs of pulse-like ground motions are used as the input data, and the features extracted by the SCNNs are used for the identification. Based on the time-domain features, pulse-like and non-pulse-like ground motions are classified into several classes. The results indicated that all the identified pulse-like ground motions have similar pulse features to the pre-selected training data. The principal advantage of the method is that the misclassification problem can be minimized by an updating procedure proposed by this paper.

This paper presents a numerical approach to construct the seismic probabilistic capacity models for the transversal lining section of circular tunnels. The influence of the lining dimension, reinforcement ratio, and properties of the concrete, reinforcement steel, and soil are considered. Two capacity measures, the bending moment M and the diametric distortion Δd/d, are considered, and each of them is represented by a separate model. To consider the possible correlation of the two capacity measures, a bivariate moment-distortion capacity model is also proposed. As an application example, the proposed capacity models are used to estimate the fragility curves of a tunnel.