Abstract:Aiming at the problem of floor cracking in the closing process of prestressed concrete box girder in cantilever construction, the failure mechanism and prevention are studied in this paper. Taking a prestressed concrete continuous box girder bridge as an example, the construction process of the box girder is simulated, the cracking process of the bottom plate is simulated by considering the material nonlinearity, and the mechanism of the bottom plate cracking is analyzed. On this basis, the prevention and control measures are proposed for design and application according to the code. The results show that the hole rib is the most disadvantageous area due to the influence of the closing beam, and the inclined crack and tearing crack of the hole rib are the main causes of the failure of the box girder under the action of radial force. In the future design of box girder, the transverse base plate should meet the shear bearing capacity, and the hole ribs should meet the requirements of minimum hole spacing.

Abstract:Based on modal perturbation method and mode superposition method, a calculation method for vertical seismic response analysis of prestressed Bridges is established. Through the analysis of two typical engineering examples, several problems in vertical seismic response analysis of Bridges are discussed. The results show that: (1) The preloading increases the natural vibration frequency of the bridge, and the influence is mainly reflected in the low-order natural vibration frequency. With the increase of the mode order, the influence of the preloading decreases. For prestressed Bridges with 20m and 32m spans, the vertical fundamental frequency increases by 5.3% and 6.3%, respectively, while the fifth vertical frequency increases by only about 1%. (2) The bending moment of the mid-span section of the prestressed beam is reduced by about 30% and 25% under the action of the surface wave, and the earthquake resistance of the bridge is improved by the prestressing force. (3) The contribution of higher order modes in vertical seismic response can be ignored. (4) The vertical seismic effect accounts for 24.56% and 26.15% of the load combination effects of the mid-span bending moment of prestressed Bridges at 7 degrees of fortification intensity, and 38.93% and 41.46% at 8 degrees of fortification intensity, respectively, indicating that the influence of vertical seismic response should be considered in the seismic design of prestressed Bridges.

Abstract:In this paper, the influence of cable slip on the development process of folded cable rod structure is studied. On the basis of a two-node cable element based on catenary analytical solution, the slip stiffness of the cable at the support point is derived. By adjusting the length of the cable segments on both sides of the support point, the cable forces on both sides can meet the coordination relationship, and an analysis method for the motion process of the cable structure is established. In order to verify the correctness of the proposed method, two numerical examples introduced in the literature are analyzed. The analysis results show that the proposed method can simulate cable slip in cable structure correctly and effectively. Finally, the development process of the folding cable-bar structure composed of four-link mechanism and cable is discussed. The results show that the cable slip has a great influence on the structural performance of the cable rod. When the slip of cable is considered, the length of the active cable changes less, and the node coordinates change more.

Abstract:6400t hydraulic compound crane is mainly used for lifting large and overweight equipment in the construction of large coal chemical and petrochemical projects. The maximum rated lifting weight is 6400t, the lifting height is 120m, and the equipment design and manufacturing localization rate is 100%, which solves the shortcomings of the existing large crawler crane such as long installation cycle and large floor area. This paper introduces the hydraulic equipment of the crane.

Abstract:The traditional bridge expansion device has no vertical, torsion and other multi-directional displacement functions, which can not meet the needs of multi-directional displacement in the process of bridge service. The prestressed multi-direction displacement expansion device is a new generation of bridge expansion device developed for the shortcomings of the traditional expansion device. The device is flexible anchored on the beam body through the multi-direction displacement system to meet the vertical, transverse, oblique and other multi-direction displacement needs of the beam end. It has the characteristics of reasonable structural design, durable, stable driving, anti-noise and waterproof performance The problem of frequent damage is solved because the traditional expansion device cannot meet the needs of multi-directional displacement of the bridge.

Abstract:In the existing bridge expansion device. The modular expansion device is widely used in bridge engineering because of its durable structure, good waterproof performance and convenient installation. However, the height of the existing modular expansion device is relatively high, and deep installation notches should be reserved at the end of the beam body before installation. Shallow buried modular expansion device is a new type of practical expansion device designed for the shallow reserved installation slot of the beam body, and the conventional modular expansion device can not be installed.