Shear Behaviors of Steel-Plate Connections for Timber-Concrete Composite Beams with Prefabricated Concrete Slabs

To promote the development of timber-concrete composite(TCC)structures,it is necessary to propose the assembly-type connections with high assembly efficiency and shear performances.This article presented the experimental results of the innovative steel-plate connections for TCC beams using prefabricated concrete slabs.The steel-plate connections consisted of the screws and the steel-plates.The steel-plates were partly embedded in the concrete slabs.The concrete slabs and the timber beams were connected by screws through the steel-plates.The parameters researched in this article included screw number,angle steel as the reinforcement for anchoring,and shallow notches on the timber surface to restrict the slip of the steel-plates.Experimental results were discussed in terms of failure modes,ultimate bearing capacities,and slip moduli.It was found that increasing the number of screws could lead to the obvious improvement on the ultimate bearing capacities and the slip moduli at the ultimate state;and the angle steel as the reinforcement showed the slight influence on the ultimate bearing capacities and the slip moduli.The application of the shallow notch can greatly improve the ultimate bearing capacities and the slip moduli.The calculation models for the ultimate bearing capacities and the slip moduli of the steel-plate connections with and without shallow notches were proposed,which showed good accuracy compared with the experimental results.

Facile detection of pesticides using atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry with multi-walled carbon nanotubes-based matrix

A novel atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry(AP-MALDIMS)method was established for the facile detection of pesticides in ambient environment.Four kinds of multi-walled carbon nanotubes(MWCNTs)-based matrix were synthesized and utilized to enhance the ionization efficiency of pesticides.Organophosphorus,anilinopyrimidine,carbamate,triazine,triazole and benzimidazole pesticides were directly desorbed and ionized from MWCNTs-based matrix in ambient environment,showing clear background and good sensitivity.In a comparison,Fe3O4-doped MWCNTs improved the intensity of pesticide ions more than the other three matrices.Moreover,MWCNTs-based matrix exhibited better performance than organic matrix.Quantitative analysis of pesticides using APMALDI-MS was validated to be adequate linearity,repeatability and sensitivity.Overall,AP-MALDI-MS combined with MWCNTs-based matrix enables the directly qualitative and quantitative analysis of pesticides in ambient environment.