Experimental Study on the Damage of Bridge Pier under the Impact of Rockfall

In this paper, a discussion is presented about the impact-induced damage suffered by bridge pier columns during rockfall events through model tests and impact force, column top displacement, stress-strain response, and other parameters in relation to the process of impact. On this basis, the following conclusions are drawn. Firstly, the impact force, as well as the displacement and strain of the column top, increases rapidly after taking a hit, while the displacement is reduced after reaching its maximum. Secondly, at the same falling height, the higher the impact position, the smaller the peak of impact force and the longer the attenuation period. Thirdly, at the same impact height, the impact energy, the displacement of the column top, and the peak of the impact force increase as the falling height of the pendulum ball is on the rise, but the attenuation period remains unchanged. Fourthly, the failure mode of column impacted by the swing ball conforms to shear-flexural failure. Fifthly, it is recommended to strengthen the preventative measures for those weak positions like 1/2 height and 1/4 height of bridge pier, so as to minimize the potential damage caused by rockfalls. Besides, a theoretical formula used to estimate the maximum impact force is proposed. Lastly, under the axial load of bridge deck, the performance of the pier in impact resistance under rockfall is better and the damage is less severe than in the experimental impact test. The axial load applied by the deck imposes some constraints on the pier, thus reducing concrete damage. The research results can contribute to the research on addressing the rockfall-bridge pier collision problem. The experimental research demonstrates its theoretical significance to engineering for the prevention of rockfall

Effects of nanocomposite grain growth inhibitors and multi-walled carbon nanotubes on the microstructure and mechanical properties of ultrafine cemented carbides

Obtaining cemented carbides with smaller WC grain size and better properties is key to their wider application. Ultrafine cemented carbides were prepared by using spark plasma sintering (SPS) with nano VC-Cr3C2 as nanocomposite grain growth inhibitors (NGGIs) and multi-walled carbon nanotubes (MWCNTs) as reinforcing materials. The effects of NGGIs and MWCNTs on the microstructure and mechanical properties of alloys were evaluated. The results indicated that the specimens (0.5 wt % NGGIs and 0.4 wt % MWCNTs) prepared at 1350 °C for 8 min under a pressure of 50 MPa have enhanced mechanical properties (HV 2520.85 kgf/mm2, KIC 13.26 MPa m1/2) and a homogeneous microstructure. The grain size of WC is suppressed (the average grain size is 200–400 nm). NGGIs can prevent the dissolution of W and C in liquid Co, thereby inhibiting the growth of WC grains. The uniform dispersion of MWCNTs in WC matrix mobilizes their fiber-reinforcement effect. The combination of NGGIs, MWCNTs, and SPS can improve the mechanical properties and optimize the microstructure of the alloy

Structure-activity relationships of trimethoxybenzyl piperazine N-type calcium channel inhibitors

We previously reported the small organic N-type calcium channel blocker NP078585 that while efficacious in animal models for pain, exhibited modest L-type calcium channel selectivity and substantial off-target inhibition against the hERG potassium channel. Structure-activity studies to optimize NP078585 preclinical properties resulted in compound 16, which maintained high potency for N-type calcium channel blockade, and possessed excellent selectivity over the hERG (~120-fold) and L-type (~3600-fold) channels. Compound 16 shows significant anti-hyperalgesic activity in the spinal nerve ligation model of neuropathic pain and is also efficacious in the rat formalin model of inflammatory pain