The deployment of a cylinder based on origami with Kresling pattern, whose basic mechanisms are formed by the buckling of a thin cylindrical shell under torsional loading, is studied in this paper. The model consists of identical triangular panels with cyclic symmetry and has a small displacement internal inextensional mechanism. First, geometric formulation of the design problem is presented. Then, assuming that the deployment and folding process is uniform, the bistable behavior of the cylinder is discussed. It can be found that, during the deployment, the dimensionless strain energy increases first and then reduces to zero but followed by another sharp increase. Moreover, the limit condition of geometry parameters for the bistable phenomenon is also discussed. Finally, the bistable behavior is also studied by using numerical simulations for simple and more complex case of the cylinder with multistory. The numerical results agree well with the analytical predictions. Therefore, comparisons with finite element predictions have shown that the analytical solutions given in this paper are accurate and have validated the assumptions made in the derivations.

Calcium silicate hydrate (C-S-H) is the main hydration product of cementitious materials, often experiencing complex stress conditions in practical applications. Therefore, reactive molecular dynamics methods were used to investigate the mechanical response of the atomistic structure of C-S-H under various uniaxial and biaxial strain conditions. The results of uniaxial simulations show that C-S-H exhibits mechanical anisotropy and tension–compression asymmetry due to its layered atomistic structure. By fitting the stress–strain data, a stress–strain relationship that accurately represents the elastoplasticity of C-S-H was developed. The biaxial yield surface obtained from biaxial simulations was ellipsoidal, again reflecting the anisotropy and asymmetry of C-S-H. Four yield criteria (von Mises, Drucker–Prager, Hill, and Liu–Huang–Stout) were further investigated, and it was found that the Liu–Huang–Stout criterion can effectively capture all the major features of the yield surface. During a uniaxial tensile process in the z direction, multi-crack propagation was observed, which was aggravated and weakened by y direction tensile and compressive strains respectively. The results of chemical bond analyses revealed that, for different strain conditions, the Ca_W–O_S and Ca_S–O_S bonds play different roles in resisting deformation.

This article proposes a method for assessing fatigue damage in reinforced concrete bridges based on a train-bridge coupled dynamic analysis system. The analysis system can be used to perform coupled vibration analyses of the bridge’s behavior during train passages. The Palmgren–Miner rule is used to estimate the linear accumulation of fatigue damage based on recommended S–N relationships for reinforced concrete from various codes. The method can be used to evaluate the dynamic performance of a bridge in conjunction with moving load (ML) and moving spring-mass-damper (MSMD) vehicle models. Calculated dynamic stresses are used to evaluate the fatigue damage at critical locations. A case study is presented focusing on the Långforsen Bridge, a railway arch bridge with a span of 89 m in northern Sweden. Fatigue assessments are conducted by combining the presented method with empirical measurements, and the effects of train speed and axle load on fatigue damage are investigated. Train-bridge coupled dynamic analysis using the proposed method provides a feasibly accurate solution for fatigue damage prediction in the four studied load cases. For low speeds and light loads, the two vehicle models yielded identical predictions of cumulative fatigue damage. However, their predictions diverged significantly for higher speeds and/or axle loads.