Life Assessment of Railway Tunnel Lining Structure Based on Reliability Theory

The reliability of the tunnel lining during its service life has significance for tunnel safety management. To capture the performance of the lining under the effect of deterioration factors, the time-varying reliability theory was applied to predict the service life of the lining. The failure process of the lining structure under an erosion environment was analyzed. The limit state equations of the lining structure were established based on the durability criterion and the bearing capacity criterion, respectively. The time-varying reliability of the tunnel was calculated using the Monte-Carlo method with an engineering example, and the service life of the tunnel under different criteria was predicted based on the target reliability. The results show that the predicted service life of the tunnel is 77.5 years under the durability criterion and 95 years under the bearing capacity criterion, assuming that the tunnel structure is in an erosive environment at the beginning of construction and that no protective measures are taken under the most unfavourable conditions. The durability meets the structural applicability, and the bearing capacity meets the structural safety, which is in line with the actual needs of the project. The study results can provide a basis and reference for the future durability design, life prediction, and maintenance management of similar service tunnels

Two Opposite Sides Synchronous Tracking X-ray Based Robotic Welding Inspection System

For inspecting welding seams of large-scale equipment such as storage tanks and spherical tanks, it usually cost much manpower and material, while automated testing robot can achieve fast and accurate detection. Because X-ray Flat Panel Detector is dependent on specialized automated equipment, it can greatly enhance X-ray inspection technology in large storage tanks that applying the Mecanum Omnidirectional Mobile Robot into automated weld detection. In this paper, an X-ray Flat Panel Detector based wall-climbing robotic system is developed for intelligent detecting of welding seams. The robot system consists of two Mecanum vehicles equipped with either a Flat Panel Detector or an X-ray generator and climbing on both side of the tank wall. Inspection robot can carry detector stably with reliable suction force and adapt to different surfaces. To let the X-ray Flat Panel Detector work properly, dual cameras positioning system is used to ensure synchronous operation of the two robots. Some experiment was conducted and reported

2,2′-Dimethyl-1,1′-[2,2-bis­(bromo­methyl)propane-1,3-di­yl]dibenzimidazole hemihydrate

The title compound, C21H22Br2N4·0.5H2O, contains two benzimidazole groups which may provide two potential coordination nodes for the construction of metal–organic frameworks. The mean planes of the two imidazole groups are almost perpendicular, with a dihedral angle of 83.05 (2)°, and adjacent mol­ecules are linked into a one-dimensional chain by π–π stacking inter­actions between imidazole groups of different mol­ecules [centroid-to-centroid distances of 3.834 (2) and 3.522 (2) Å]

3-Carb­oxy­quinolin-1-ium-2-carboxyl­ate monohydrate

The title compound, C11H7NO4·H2O, contains a 3-carb­oxy­quinolin-1-ium-2-carboxyl­ate (qda) zwitterion and one water mol­ecule. In the crystal, pairs of N—H⋯O hydrogen bonds link the mol­ecules into inversion dimers, and these dimers are further connected by O—H⋯O hydrogen bonds into a three-dimensional supra­molecular architecture. In addition, π–π inter­actions occur between pyridine and benzene rings from different qda ligands [centroid–centroid distance = 3.749 (1) Å] and the dihedral angles of the –CO2H and –CO2 groups to the quinoline system are 8.47 (3) and 88.16 (6)°, respectively