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Trzy lignany/neolignany z żywicy benzoinowej

100%

Liang Q.-M. , Zhang Q. , Zhang L. , Wang F.

Przemysł Chemiczny

2020

tom T. 99, nr 2

298--302

Z żywicy benzoinowej wyizolowano 3 nowe lignany/neolignany poprzez ekstrakcję etanolem, chromatografię kolumnową na żelu krzemionkowym i krystalizację z octanu etylu. Następnie zidentyfikowano je na podstawie analizy chemicznej i spektroskopii NMR jako benzoesan 2 -[(4-hydroksy-3-metoksyfenylo)-metoksymetylo] -5-(4-hydroksy-3-metoksyfenylo)-pent-4-enylu (I), benzoesan 2-[(4-hydroksy-3-metoksyfenylo)-metoksymetylo]- 5-(4-hydroksyfenylo)-pent-4-enylu (II) i 1-(3-hydroksy-4-metoksyfenylo)-2-etoksymetylo- 3-winylo-6-metoksyindano-5-ol (III).

Three new lignan or neolignan compds. were isolated from a benzoin resin by EtOH extn., silicagel column chromatog. and crystn. from AcOEt. They were then identified by chem. anal. and NMR spectroscopy as 2-[(4-hydroxy-3-methoxyphenyl)- -methoxymethyl]-5-(4-hydroxy-3-methoxyphenyl)-pent-4- enyl benzoate, 2-[(4-hydroxy-3-methoxy-phenyl)-methoxymethyl]- 5-(4-hydroxyphenyl)-pent-4-enyl benzoate and 1-(3-hydroxy-4-methoxyphenyl)-2-ethoxymethyl-3-vinyl-6 -methoxyindan-5-ol.

Nonlinear finite element analysis of punching shear strength of reinforced concrete slabs supported on L-shaped columns

100%

Zhang Q. , Milligan G. J. , Polak M. A.

Budownictwo i Architektura

2020

tom Vol. 19, no 4

125--138

Most current concrete design codes include provisions for punching shear of reinforced concrete slabs supported on columns with L, T, and cruciform shapes. Reference studies verifying the accuracy of these code provisions are typically not provided. Empirical data of punching failures of slabs supported on columns with L, T, and cruciform shapes are limited due to the cost and time required to test specimens with slab thicknesses and column sizes commonly used in practice. In this paper, the punching shear behaviour of five interior L-shaped slab-column connections, one without a slab opening and four with slab openings, subjected to static concentric loading are analyzed using a plasticity-based nonlinear finite element model (FEM) in ABAQUS. The FEM is similar to models previously calibrated at the University of Waterloo and are calibrated considering nine slabs that are tested to study the impact of column rectangularity on the punching shear behaviour of reinforced concrete slabs. The finite element analysis results indicate that shear stresses primarily concentrate around the ends of the L, and that current code predictions from ACI 318-19 and Eurocode 2 may be unconservative due to the assumed critical perimeters around L-shaped columns.

Analysis of a nonlinear tuned mass damper by using the multi-scale method

88%

Liu J. , Yao J. , Huang K. , Zhang Q. , Ze L.

Journal of Theoretical and Applied Mechanics

2022

tom Vol. 60 nr 3

463--477

A tuned mass damper is a kind of vibration damping device which has been widely used in tall buildings, machinery, bridges, aerospace engineering and other fields. In practical engineering applications, due to large deformation caused by large displacement, errors in engineering constructions and the existence of limit devices, the structure and tuned mass dampers inevitably produce some nonlinear characteristics, but these nonlinearities are often ignored. The results of this study confirm that the nonlinearity of the structure and the mass damper should be considered in the process of optimal frequency design, otherwise there will be a large deviation between the design optimal frequency of the mass damper and the actual optimal frequency. In this paper, nonlinear characteristics of the tuned mass damper and the main structure are considered. The first-order differential equations are obtained by using the complex average method, and the nonlinear equations of the tuned mass damper system are derived by using the multi-scale method. On this basis, the parameters are determined. The numerical results show that the error of the approximate solution method is small in the given example. The nonlinear tuned mass damper with nonlinear design exhibits a better control performance.