This paper develops a novel dry connection utilizing high-strength bolts and introduces the corresponding low-rise precast wall panel structure system. To investigate the seismic performance of the structure system with full bolt connections, monotonic loading tests of the connection joint and cyclic lateral loading tests of three full-scaled precast shear walls are both conducted. Based on the test data, axial and shear mechanical models of the connection are given. Meanwhile, experimental results show that the failure mode of the connection is dominated by anchored rebar ductile rupture, and the precast structure system presents a stable energy dissipation capacity and a good seismic ductility. The numerical model of the precast shear wall is then developed and validated by the cyclic loading test. Also a simplified calculation method to predict the lateral strength of the precast shear wall is proposed. According to the calculation results, the distance between the center of the connection and the edge of the shear wall is suggested to be 150 mm, while the wall thickness is recommended to be 120 mm or 150 mm. Finally, a three-story precast wall panel structure is employed to assess the collapse performance of the proposed precast structure system by using the presented numerical model. The results indicate that the proposed structure system with full bolt connections has high stiffness and high seismic resistance against collapse.
Seismic loads pose a potential threat to the high-speed railway bridges in China, which have been rapidly developing in recent years, especially for those subjected to the near-fault earthquakes. The previous researches on high-speed railway bridges usually concern the far-field earthquake, and the damage of high-speed railway bridge–track system subjected to the near-fault earthquake has not been well studied. In this article, a seven-span high-speed railway simply supported bridge–track system is selected to explore the seismic damage features under the excitation of near-fault earthquake which possesses characteristics of obvious velocity pulse and high-frequency vibration. First, a detailed finite element model of the selected bridge–track system is established and calibrated by the experimental data and design code. Then the low-frequency pulse-type portion and the high-frequency background portion are separated from the selected eight original near-fault records, and a series of nonlinear dynamic analysis is conducted. The results show that the background portion leads to more serious damage of the bridge–track system than the pulse-type portion. Due to the high stiffness of high-speed railway bridge–track system, the background portion with high-frequency vibration characteristic produces the main part of seismic response of system. As for the damage part of system, the weakest component of the bridge–track system is the sliding layer, followed by the shear alveolar.
Development
of efficient and sustainable monolithic catalysts for
NaBH4 hydrolysis remains an important goal for hydrogen
cycling. In this work, the structured catalyst Ru/MgO with an on–off
feature has been prepared by directly growing a nano-Ru-embedded MgO
coating layer on a Mg substrate via an instant high-temperature plasma
oxidation process. The porous MgO framework provides an ideal space
for the access of reactants and diffusion of mass transport, which
facilitates reaction triggering and the expulsion of byproducts to
avoid poisoning the catalyst. Importantly, Ru nanoparticles (NPs)
are monodisperse with ultrasmall particle size deriving from a concurrent
rapid arcing and fast quenching. The hierarchical structured Ru NP
catalysts are highly active for hydrolysis of sodium borohydride by
achieving a high hydrogen generation rate (HGR) of 101,189 mL min–1 g–1 and exhibit attractive stability.
In addition, it is facile to realize the “on–off”
functionality based on simple separation that could accurately control
the hydrogen generation, suggesting the structured catalyst to be
of great potential for practical applications. This simple method
opens valuable opportunities for fast synthesis of the high-quality
structured catalyst and could be extended to various noble metals
on oxides of valve metals with high catalytic performance.
Summary
The asymmetrical high‐rise building investigated in this paper is composed of a 299.1‐m‐high tower and a 235.2‐m‐high tower, which are diagonally and rigidly connected by two steel truss systems with the maximum span of 65.43 m. Given the great structural irregularities and complexities, the structural seismic performance is necessary to be investigated. A shaking table test of a 1/45 scaled model is conducted in this study, by which the structural damage pattern and dynamic responses are analyzed. The results show that the connecting trusses and rigid connection joints behave well during strong seismic excitations. The damages concentrate on the connecting floors, and the whole structural damage is slight. Most of the lateral resistance components remain elastic. The structure presents high seismic resistance against strong ground motions. Subsequently, a three‐dimensional finite element model of prototype structure is established and validated by the experimental results. The analyses indicate that performance of the connecting trusses is capable of coordinating translational and torsional deformation of the two towers and making them resist lateral seismic force together even subjected to maximum considered earthquakes. And this performance is still reliable although the high torsional modes are triggered.
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