Modular steel buildings offer the advantages of time-saving construction, reduced on-site work, and less resource waste. The mechanical behavior of modular connections is complex, depending on the type of connecting method and the load-transferring path. The aim of this paper is to offer an overview of the methods for creating inter-module connections. First, we discuss the existing inter-module connections, including vertical connections, horizontal connections, and module-to-concrete-core-wall connections. Then, the mechanical performance and simplified models of the inter-module connections are reviewed in detail; these have a significant influence on the development of modular steel buildings. Finally, the prospects of module-to-module connection are summarized. Despite the increasing amount of research that explores module-to-module connections, fully modular buildings have not yet been achieved, hindering the further development and use of modular steel buildings. In this context, self-locking connections and laminated double-beam connections are proposed, with the aim of promoting the increased use of modular steel buildings.

To elucidate the relationship between compressive strength and pore structure of the high water grouting material with different water-binder ratios and CaO contents, the compressive strength was tested while pore structure including pore characteristic parameters and pore diameter distribution were investigated by BET, MIP, and 3D-XRM. Moreover, the evolution of hydration products was observed by TGA and SEM, illustrating the reactive mechanism of the material. Furthermore, the grey correlation coefficients between compressive strength and pore structure parameters were illustrated according to the grey correlation theory. The results show that CaO content in lime is proportional to the compressive strength with the water-binder ratio of 1.0 or 1.5, while the inverse trend appears with the water-binder ratio of 2.0. The high water grouting material belongs to the macropore material with the pores mainly within 100 nm to 2 μm. Its hydration products contain ettringite crystals, aluminum gels, and C-S-H gels. The productions of the hydration products are positively correlated with its compressive strength. In addition, the compressive strength of the high water grouting material is closely related to the pore characteristic parameters and the pore size distribution, especially the porosity, the most probable pore diameter, and the pore volumes within 100~500 nm and 10~100 nm.

In this paper, a new type of assembling rivet-fastened rectangular hollow flange beams (ARHFBs) is proposed. The cross-section of the ARHFB consists of two U-shaped and C-shaped components connected by self-locking rivets to form two rectangular hollow flanges. To study the performance and strength of the ARHFB as a flexural member, eight four-point bending tests and more than 40 simulation studies were carried out. The details, results, and comparison of the four-point bending tests, especially the characteristics of the test bench and the lateral support, are presented in this paper. ARHFB sections with varied rivet spacing, web depth, and flange width were experimentally studied. Additionally, a parametric study of ARHFB was conducted using finite element models verified by test results. The influence of span on the loading capacity of ARHFB was discussed. ARHFB can be used in large-span buildings. A more economical ARHFB component selection method was given. The depth of the flange, the strength of the web, and the thickness of the web are important parameters of ARHFB. The loading capacity obtained from the test was compared with the predicted values of the design formulas in the American Iron and Steel Institute (AISI) and the Chinese design standard for cold-rolled steel (GB50018). The calculation and verification of ARHFB flange buckling and lateral torsional buckling were also considered. It is recommended that GB50018 be used to predict the flexural capacity of ARHFBs.

Peridynamic models have demonstrated inherent advantages in modeling dynamic crack propagations. The crack initiation and propagation in peridynamics are realized through the breaking of bonds between material points. However, the breakage of the bonds may lead to weak non-conservation of energy in the system, which may further influence the crack propagation and even lead to an incorrect prediction. This work proposed a modification for the breaking bonds, the purpose of which is to ensure energy conservation and obtain correct energy conversion in the system. Then an energy-based quantitative indicator for the study of the convergence of discrete parameters in peridynamic models was provided. In order to verify the correctness of the modification and the effectiveness of the indicator, cases of a typical benchmark problem under different initial and loading conditions were investigated. The results indicate that the modification performs well in maintaining energy conservation of the system during the updating processes and that the energy-based quantitative indicator has been proven to be a robust enabler for convergence investigations. The contributions of this study refine the treatment of breaking bonds and provide a reliable indicator for convergence investigations.

Propellers are essential aerodynamic components widely used in aerospace engineering, marine vessels, and aerial platforms. With the growing demand for high-thrust electric unmanned aerial vehicles, greater emphasis is being placed on improving propeller aerodynamic performance and efficiency to enhance flight endurance and payload capacity. Traditional design methods, mostly based on blade element theory, simplify the blade into two-dimensional planar elements, making it difficult to accurately capture the three-dimensional streamline characteristics during rotation. This mismatch between geometric design and actual flow limits further improvements in propulsion efficiency. This paper proposes a two-dimensional airfoil body-fitted design method to address this limitation. This method is based on blade element theory and vortex theory to obtain the chord length and pitch angle distribution under specific operating conditions. Based on these distributions, each blade element is bent to fit a virtual cylindrical surface at the corresponding position. This ensures that all points on the two-dimensional airfoil are equidistant from the hub center. The proposed design method is validated through numerical simulations. The results show that the propeller designed with the body-fitted method improves efficiency by 4.2% compared with the one designed using blade element theory. This work provides a new technical approach for propeller design and has practical value for improving propeller efficiency.