The mechanical and thermal properties of graphene kirigami are strongly dependent on the tailoring structures. Here, thermal conductivity of three typical graphene kirigami structures, including square kirigami graphene, reentrant hexagonal honeycomb structure, and quadrilateral star structure under uniaxial strain are explored using molecular dynamics simulations. We find that the structural deformation of graphene kirigami is sensitive to its tailoring geometry. It influences thermal conductivity of graphene by changing heat flux scattering, heat path, and cross-section area. It is found that the factor of cross-section area can lead to four times difference of thermal conductivity in the large deformation system. Our results are elucidated based on analysis of micro-heat flux, geometry deformation, and atomic lattice deformation. These insights enable us to design of more efficient thermal management devices with elaborated graphene kirigami materials.

Combined bolted–welded joints use both bolting and welding methods to connect several members, resulting in a versatile and robust solution for structural connections. However, very limited studies have focused on the residual stress distribution and fatigue behavior of these joints. In this paper, a total of eight specimens of double lap joints using bolts and fillet welds were fabricated and tested to measure the residual stress distribution. A finite element model was also developed for predicting the residual stress and residual deformation, and then it was validated against the test results. The effects of different welding parameters on the residual stress and residual deformation were evaluated, including the welding sequence (four different welding sequences) and welding process (welding speeds of 4 mm/s, 6 mm/s and 10 mm/s; welding powers of 5000 W, 6000 W and 7000 W; and post-weld heat treatments of no insulation, insulation at 200 °C and insulation at 300 °C). The fatigue behaviors of combined bolted–welded joints with and without residual stresses were compared in terms of the fatigue life of crack propagation. It was shown that the maximum residual stress was approximately 450 MPa, far exceeding the yield strength of steel plate of 335 MPa, while welding sequence 1 produced the smallest residual stresses. Due to the presence of welding residual stresses, the fatigue life of combined bolted–welded joints was reduced by nearly 40%, which indicated that the fatigue life of the joint would be overestimated without considering the residual stresses.

A rotary nanomotor is an essential component of a nanomachine. In the present study, a rotary nanomotor from wedged diamonds and triple-walled nanotubes was proposed with the consideration of boundary effect. The outer tubes and mid-tubes were used as nanobearing to constrain the inner tube. Several wedges of the diamond were placed near the inner tube for driving the inner tube to rotate. At a temperature lower than 300 K, the inner tube as the rotor had a stable rotational frequency (SRF). It is shown that both the rotational direction and the value of SRF of the rotor depended on the temperature and thickness of the diamond wedges. The dependence was investigated via theoretical analysis of the molecular dynamics simulation results. For example, when each diamond wedge had one pair of tip atoms (unsaturated), the rotational direction of the rotor at 100 K was opposite to that at 300 K. At 500 K, the rotating rotor may stop suddenly due to breakage of the diamond needles. Some conclusions are drawn for potential application of such a nanomotor in a nanomachine.

Owing to the light-transmitting, energy-saving, and load-bearing properties of glass, laminated glass has gradually been adopted as vehicle lane surfaces in scenarios such as multi-storey commercial complexes, glass walkways roads, and underground parking lots. However, currently, a mature design system for vehicle-borne glass bridge decks is still lacking, and the existing design system for pedestrian glass bridge decks cannot be directly applied to vehicle-borne scenarios. Combining domestic and international specifications and research, this study focused on material selection, structural configuration, and structural calculation of vehicle-borne glass bridge decks, proposed a targeted design method, and verified it with engineering examples. The key conclusions are as follows: (1) Laminated glass for bridge decks should preferably use homogenized tempered glass with SGP as the interlayer material; the number of glass layers should be controlled between 3 and 5, the aspect ratio of glass panels should be maintained between 1 and 2, the thickness of a single glass panel should not be less than 8 mm, and the interlayer thickness should be between 0.76 mm and 2.28 mm. (2) This study proposes design loads, load combination methods, calculation models, design criteria, and the equivalent thickness calculation method for vehicle-borne glass bridge decks; meanwhile, it incorporates the adverse working condition of single-layer glass breakage into design considerations. (3) The design method shows good agreement with numerical simulation results: both PVB and SGP-laminated glass can meet the load-bearing capacity requirements, but SGP-laminated glass has a larger safety redundancy under the same thickness; after single-layer glass breakage, the bridge deck still has sufficient load-bearing capacity; the calculation results of the design method are slightly more conservative than the finite element calculation results, but the calculation of stress and deflection for SGP-laminated glass is relatively accurate. (4) Future research will further deepen the study on the impact of the long-term performance of laminated glass on the full-life-cycle of vehicle-borne glass bridge decks and improve this design method.

Post-rotation jacking is a critical construction stage for load-path reconstruction and alignment adjustment in rotation-constructed bridges, particularly for ultra-wide double-deck composite girder systems. Taking a two-span continuous steel truss–concrete composite girder bridge with spans of 2 × 85 m as the engineering background, this study investigates the mechanical behavior during post-rotation jacking through theoretical derivation, finite element simulation, and on-site monitoring. Based on the force method of structural mechanics, a linear relationship between vertical synchronous jacking force and displacement is derived, and an analytical formulation for bearing reaction redistribution under laterally asynchronous jacking is established by considering the coupling effects of vertical bending, torsion, and transverse multi-bearing support. A full-bridge spatial finite element model was developed in MIDAS Civil NX 2024 V1.1 to analyze the redistribution of bearing reactions and the stress response of the concrete crossbeam under different jacking conditions. The results show that, for the investigated bridge, the jacking force–displacement response remains highly linear during synchronous jacking. The B-axis middle bearing is more sensitive to jacking displacement than the two side bearings, with its fitted stiffness being approximately 2.19 times the average stiffness of the side bearings. Eccentric jacking causes reaction concentration at the jacked point and reaction reduction at adjacent supports, and the magnitude of reaction variation increases approximately linearly with jacking displacement. When the transverse non-uniform jacking magnitude reaches 20 mm, a tensile stress of 0.3 MPa appears at the bottom flange of the concrete crossbeam; therefore, a project-specific stroke-difference limit of 20 mm is recommended for this bridge, while the actual construction achieved a stroke control accuracy of ±0.5 mm and a transverse elevation difference within 1 mm. Field monitoring results validate the proposed analytical and numerical methods. The Pearson correlation coefficients of the measured jacking forces with the finite element and theoretical results are 0.9987 and 0.9988, respectively, and the corresponding mean relative errors are 3.84% and 4.23%. For stress responses, the measured and calculated values show a strong correlation, with a Pearson correlation coefficient of 0.9980 and a mean relative error of 12.77%; the critical mid-span monitoring point shows a relative error of only 0.65%. The final bridge alignment deviation is controlled within ±3 cm. The overall mean verification coefficient is 0.968, with a 95% empirical agreement range of [0.888, 1.048], indicating that the proposed mechanical analysis framework and combined force–displacement control strategy can provide a useful reference for refined construction control of similar ultra-wide double-deck composite girder bridges with comparable span arrangement and transverse bearing layout.

The frictional behavior and stability of skid shoe systems are critical to the safety and controllability of walking-type incremental launching for long-span steel truss bridges. Therefore, this study investigates friction control mechanisms and multilayer pad stability through two tests: (1) skid shoe tests to evaluate low-friction performance, sliding stiffness, and the stability of stacked pad assemblies, and (2) interface friction tests to examine the frictional behavior of different material combinations intended to provide high-friction restraint. The results show that Modified Graphene-Enhanced (MGE) plates, when combined with grease and stainless steel, reduce the friction coefficient to 0.017–0.074. High-stack pad assemblies (6–16 layers) exhibited a progressive interlayer slip, with cumulative displacements exceeding the allowable limit, leading to instability; anti-slip measures such as shear keys and segmented restraints were recommended. A load-dependent sliding stiffness relationship, y = 57.46 + 0.00886x, was established to characterize the variation in nominal sliding stiffness with vertical load. The findings provide experimental data and engineering recommendations for the design and operation of skid shoe systems in heavy-load incremental launching applications. The proposed criteria and regression model are applicable to the tested pad geometry, interface configuration, and loading conditions investigated in this study.