Experimental Analyses of Mechanical Performance of CFST Column to Assembled Steel H-Beam Connections
The mechanical performance of a new proposed type of cross-shaped connection with concrete-filled steel tubular (CFST) column and assembled steel H-beam was investigated. Cyclic loading tests on the cross-shaped connections are carried out by using MTS servo loading system. Comparative analyses are conducted based on the experimental results including hysteretic curves, skeleton curves and stiffness degradation curves as well as ductility coefficients of cyclic loading tests. Furthermore, effects of geometric parameters of ring-stiffened plate, axial compression ratio and backing plate on the deformation performance of cross-shaped connections are analyzed. The results show that the increase of width of ring plate and the shape change of ring plate from square to circle can both significantly improve the ductility and the hysteretic characteristics of connection. It is emphasized that the specimen with square ring plates is of better deformation performance but lower bearing capacity than the ones with circular ring plates. Besides, the backing plates always have positive effects on the hysteretic characteristics, ductility and energy dissipation of the CFST column connections. Conversely, the increase of axial compression ratio contributes negatively to both the bearing capacity and deformation performance of the connection specimens. It can be concluded that the presented cross-shaped connection is of good deformation performance relating to hysteretic characteristics, energy dissipation and ductility, which can provide reference towards engineering practice with potential perspective application.
Seismic behaviour of full-scale prefabricated RC beam–CFST column joints connected by reinforcement coupling sleeves
Abstract This study evaluated a new type of joint for connecting reinforced concrete (RC) beams with a concrete-filled steel tube (CFST) column that consists of U-shaped steel end plates and longitudinal reinforcement coupling sleeves. The proposed joint configuration was designed to fully realise the advantages of prefabricated structures, including a short construction period, easy construction control and low environmental impact. Low-cycle reversed loading tests were conducted to evaluate the seismic behaviour of three full-scale joint specimens, namely a cast-in-place joint and two prefabricated RC beam–CFST column joints connected using reinforcement coupling sleeves. The results indicate that the prefabricated joints exhibited plumper load–displacement curves and a good connection behaviour. The prefabricated joints failed in bending, thereby resembling the failure of the cast-in-place RC beam–CFST column joint. The failure region was concentrated in the area outside of the U-shaped end plate. The coupling sleeve connection was reliable, and the plastic hinge at the beam end moved further outward. Compared to the cast-in-place joint, the prefabricated RC beam–CFST column joints exhibited a similar bending capacity. The ductility coefficients of the prefabricated RC beam–CFST column joints increased about 5.2% and 2.6%, respectively. The average energy dissipation coefficient increased by 0.71% and 1.74%. The cumulative energy consumption and working index showed no significant difference.
High-Performance Liquid Chromatographic (HPLC) and HPLC-Mass Spectrometric (MS) Analysis of the Degradation of the Luteinizing Hormone-Releasing Hormone (LH-RH) Antagonist RS-26306 in Aqueous Solution
The kinetics of the degradation of an LH-RH antagonist, RS-26306,1, in aqueous solution from pH 1 to pH 11 were studied by reverse-phase HPLC. The pH–rate profiles at 50, 60, and 80°C were U-shaped with the rate law of kobs = kHaH + kw + kOHaOH. The predicted 25°C shelf life at the pH of maximum stability, pH ∼5, is greater than 10 years. The products from the degradation were analyzed by HPLC-MS using thermospray ionization. Below pH 3, the primary product, 2, forms from the acid-catalyzed deamidation of the C-terminal amide. Above pH 7, epimerization of the individual amino acids is the principal reaction. Between pH 4 and pH 6, intramolecular serine-catalyzed peptide hydrolysis becomes important, yielding a tripeptide, 3, and a heptapeptide, 4. At the pH of maximum stability all three pathways for degradation are observed.