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.

Train-induced dynamic responses and loads in bridge pier systems are not well understood. In this study, five different piers from two separate railway bridges were investigated experimentally. The dynamic responses and loads at the bridge beam ends, pier tops, and pile caps were measured by considering various train speeds. The frequencies of the dynamic loads on pile caps were also analyzed. The results show that the induced dynamic response decreases significantly with the descending pier height. The train-induced vertical dynamic displacements are related to the axle loads and the stiffness of the pile foundation and foundation soils. The accelerations at pier tops and pile caps are very similar but noticeably less than those at beam ends. The train-induced vertical dynamic loads on pile caps increase with the total span length. The measured change of dynamic forces (ÁQ) is approximately 20 À 30% of the measured peak loads (Q). In addition, the results show that the frequency (f) varies linearly with the train speed rather than with the bridge span length.

To meet the ventilation requirement, an engineer needs to design the cantilevered roof of a stadium as a layered one with gaps between the layers. In order to further understand the wind resistance performance of such structures, a wind tunnel test was carried out on a 1:200 scaled stadium model considering two roof inter-layer cases: opened gaps and blocked gaps. The laws of lift force coefficients and net wind pressure coefficients were compared for these two gap conditions. The study results indicate that the roof experiences larger mean lift force on both top and bottom surfaces when the inter-layer gaps are blocked. However, the roof gaps can reduce the fluctuating lift force on top roof surface and the net fluctuating lift force, weakening the vibration of the flexible large-span roof. The negative pressures (suctions) in the inner and middle roof areas on the leeward side decrease for the blocked gap case. The positive pressure in the outer roof area generally increases along the windward direction, while the negative pressure decreases in other wind directions, when the roof inter-layer gaps are blocked. In the highest and transition roof areas, the fluctuating pressures increase for most wind directions, while in the lowest roof area, they decrease when the roof inter-layer gaps are blocked. The test and analysis results provide a valuable basis for the wind design of this kind of roof structures.

A series of tests were carried out on a scaled (1:8) double-deck prestressed concrete box girder in this study, aiming to study the structural response and failure mechanism of the box girder under prestressed axial compression, transverse bending, and torsion. The test results, such as the twist angle, crack development, and distortion of the box girder, were analyzed in detail. The results show that (1) the box girder eventually suffered lateral bending damage, and the cross-section of the support distorted severely; (2) torsional cracking occurred in the pure torsion region at the mid-span, but the longitudinal and transverse rebars did not yield, indicating that the pure torsion section of the box girder was still in the early stage of torsion failure; and (3) after the cracking of the box girder, stress redistribution phenomenon occurred, resulting in obvious nonlinear strain variations. Comparison of the longitudinal and transverse steel strains showed that transverse steel withstood the most shear stress during the early stage of torsion.