Ultra-high performance concrete (UHPC) as a joint material for precast bridge decks might reduce the width of the joint and improve its connection performance and durability. This study proposes a type of compact UHPC wet joint based on the mechanical properties of UHPC and the force characteristics of transverse joints in prefabricated bridge decks. The shear behavior of the novel joint was investigated through experimental study and numerical simulation. In addition, the shear properties of compact UHPC wet joints were compared with epoxy joints. The results indicated that the shear resistances of compact UHPC joints are comparable to those of epoxy joints. The failure process of the precast bridge deck with new joint might be divided into three stages: elastic stage, working stage with cracks, and yield stage. No interface cracks or reinforcement slippage was observed throughout the loading process, indicating that the UHPC joint and the epoxy joint exhibited adequate shear resistance. The ultimate load capacity and corresponding mid-span deflection of UHPC joint specimens were respectively increased by 8.6% and 75.0%, when compared with the epoxy joint specimens. Finite element analysis reveals that the transverse shear transfer range of the compact UHPC joints is within 57.1%. Bending failure due to the yielding of the transverse reinforcement at the bottom of the precast bridge deck is the primary failure mode for both specimens. Moreover, the stresses applied to the deck system have good continuity at the joint.
Using the method of emergy analysis, we analyze the input and output of agro-ecological economic system, and select five indicators (net emergy yield ratio, emergy investment ratio, environmental loading ratio, emergy sustainability index, and dominance of emergy yield system) for assessment. The results show that the emergy input-output in Wu'an City is in general on the rise; the emergy investment ratio rises constantly, but the net emergy yield ratio decreases, and the comparative advantage in the prices of agricultural products is gradually lost. At the same time, with increase in the non-renewable industrial support emergy, the environmental pressures are also mounting. In the future agricultural development, it is necessary to pay more attention to the coordination between agricultural development and ecological environment, achieving sustainable development of agriculture.
In order to provide a reliable scientific basis for further experimental study,this paper presents a theoretical study of a linear ion trap composed of arc-shaped electrodes with different radii.Software SIMION and AXSIM were used to calculate and simulate the arcshaped electrode ion trap(AEIT).By analyzing the relationship between the electric field and the ratio of the radii of the AEIT,higher order multipole fields distribution,ion trajectories in the ion trap,shapes of mass spectrometry peak,resolution and ion eject efficiency,AEITs with better performance were separated with others.
The stability and deformation of shallow tunnel faces are hard to predict, and the associated failure mechanisms are also indistinct to date. In this work, we incorporate the softening function and strain-dependent dilation model into a smoothed particle hydrodynamics (SPH) framework to simulate the collapse behaviors of shallow tunnel faces in cohesive–frictional soils under the open-face excavation condition. To this end, the stratum is modeled as a cohesive–frictional soil described by the elastoplastic constitutive model in combination with the Drucker–Prager yield criterion. Softening and strain-dependent dilation behaviors of soils are described by the softening function and the dilation model, which are incorporated into the constitutive model in the framework of the SPH method. For the deformation analysis, the effects of the cover depth variation on face extrusion and ground surface subsidence are investigated. For the face stability analysis, the impacts of the cohesion and the internal friction angle of surrounding soils on the safety factor of shallow tunnel faces are highlighted. Then, comparison is made between the results obtained from the present SPH method and those given by the finite-element method (FEM) and existing centrifuge model tests to verify the proposed SPH procedure. Ultimately, the main outcomes of the current work, including deformation features and safety factors of shallow tunnel faces, are presented.
