The grid structure with bolt–sphere joints is one type of large-span spatial structures. Due to small induced force, light weight, large stiffness, and good seismic performance, such structural system has been widely adopted in industrial plants with suspending cranes. The damage of the grid structure with bolt–sphere joints tends to occur at high-strength bolt joints, with fatigue fracture as the primary failure mode. The alternating and reciprocating action of the suspending crane will cause fatigue problems to the structural components of the grid structure, including rod, cone, sealing plate, bolted sphere, and high-strength bolt. The threads in high-strength bolt result in a significant stress concentration leading to bolt fatigue which is the key issue of fatigue failure. In this study, systematic constant amplitude fatigue tests were conducted for 18 M20 high-strength bolt made of 40Cr material using the developed efficient and smooth loading equipment combined with the Amsler fatigue testing machine, in which the tension condition of the high-strength bolt in the grid structure was simulated, simulation of high-strength bolt in tension works of grid structure. In addition, the signal-to-noise curve and the calculation method of constant amplitude fatigue for the high-strength bolt are proposed in grid structure with bolt–sphere joints.

This article is the second part of the series of the comprehensive review which is related to the outrigger and belt‐truss system design for tall buildings. In this part, by presenting and analyzing as much relevant excellent resources as possible, a guideline for optimum topology and size design of the outrigger system is provided. This guideline will give an explanation and description for the used theories, assumptions, concepts, and methods in the reviewed articles for optimum topology and size design. Finally, this part ended up with a summary for the findings of the reviewed studies, which is useful to understand how different parameters influence the optimum topology and size design of a tall building with outrigger and belt‐truss system.

The ternary blended cement with finer slag and silica fume (SF) could improve the packing density (PD) through the filling effect. The excess water (water more than needed for filling into voids between the cement particles) can be released to improve the fresh properties and densify the microstructure which is beneficial for improving the hardened properties. To verify the hypothesis and reveal how and why (cement + slag + SF) the ternary blends could bring such advantages, the binder pastes incorporating slag and SF with various water-to-binder ratios were produced to determine the PD experimentally. To evaluate the optimum water demand (OWD) for maximum wet density, the influence of the dispersion state of the binder on PD was investigated using the wet packing density approach. The effect of PD of various binary and ternary binder systems on water film thickness (WFT), fluidity, setting time, and compressive strength development of cement paste was also investigated. The results show that the ternary blends could improve the PD and decrease the water film thickness (WFT). The enhanced PD and altered WFT are able to increase fluidity and compressive strength. The ternary blends could improve the compressive strengths by increasing PD and exerting nucleation and pozzolanic effects.

The high-strength bolts of grid structures with bolted spherical joints under the action of suspension cranes are at risk of severe fatigue failure. Thus, this paper studies the variable-amplitude fatigue performance of M60 high-strength bolts. The test results for eight specimens in four loading modes are obtained using an Amsler fatigue testing machine. The fatigue life is also estimated based on Miner and Corten–Dolan’s theories, and the applicability of Corten–Dolan’s theory is verified. The fracture induced by the variable-amplitude fatigue is microscopically analyzed using scanning electron microscopy (SEM), revealing the mechanism of the variable-amplitude fatigue failure. Our findings provide valuable experimental data supporting the fatigue life estimation of grid structures with bolted spherical joints in service.

Strengthening concrete structures with ultra-high performance concrete (UHPC) can both improve the bearing capacity of the original normal concrete (NC) structure and prolong the service life of the structure due to the high strength and durability of UHPC. The key to the synergistic work of the UHPC-strengthened layer and the original NC structures lies in the reliable bonding of their interfaces. In this research study, the shear performance of the UHPC–NC interface was investigated by the direct shear (push-out test) test method. The effects of different interface preparation methods (smoothing, chiseling, and planting straight and hooked rebars) and different aspect ratios of planted rebars on the failure mode and shear performance of the pushed-out specimens were studied. Seven groups of push-out specimens were tested. The results show that the interface preparation method can significantly affect the failure mode of the UHPC–NC interface, which is specifically divided into interface failure, planted rebar pull-out, and NC shear failure. The critical aspect ratio for the pull-out or anchorage of planted rebars in UHPC is around 2. The interface shear strength of straight-planted rebar interface preparation is significantly improved compared with that of the chiseled and smoothened interfaces, and as the embedding length of the planted rebar becomes longer, it first increases greatly and then tends to be stable when the rebar planted in UHPC is fully anchored. The shear stiffness of UHPC–NC increases with the increase of the aspect ratio of planted rebars. A design recommendation based on the experimental results is proposed. This research study supplements the theoretical basis of the interface design of UHPC-strengthened NC structures.