Strength of circular concrete columns under concentric compression

An experimental study, in which six columns were loaded concentrically toinvestigate the behavior of reinforced normal strength and high strength circular columns underconcentric compression, is described. The concrete strengths of the columns were 30 MPa and 60 MPa.The primary variables considered were the concrete strength and the amount of transversereinforcement. Test results indicate that smaller hoop spacing provides higher column capacity andgreater strength enhancement in a confined concrete core of columns. For the same lateralconfinement, high strength concrete columns develop lower strength enhancement than normal strengthconcrete columns. Both the strength enhancement ratio (f'_(cc) /f'_(co)) and the column capacityratio (P_(test)/P_o) were observed to show linear increase variations with rho_s f_(yt)/f'_c incircular columns.

Seismic ultimate bearing capacity of strip footings on slope

The influence of earthquake forces on ultimate bearing capacity of foundations on sloping ground was studied. A solution to seismic ultimate bearing capacity of strip footings on slope was obtained by utilizing pseudo-static analysis method and taking the effect of intermediate principal stress into consideration. Based on limit equilibrium theory, the formulae for computing static bearing capacity factors, Nq, Nc, Nγ, and dynamic bearing capacity factors, Nqd, Ned, Nγd, which are associated with surcharge, cohesion and self-weight of soils respectively, were presented. A great number of analysis calculations were carried out to obtain the relationship curves of the static and dynamic bearing capacity factors versus various calculation parameters. The curves can serve as the practical engineering design. The calculation results also show that when the values of horizontal and vertical seismic coefficients are 0.2, the dynamic bearing capacity factors Nqd, Ned and Nγd, in which the effects of intermediate principal stress are taken into consideration, increase by 4%-42%, 3%-27% and 34%-57%, respectively.

Low cyclic fatigue performance of concrete-filled steel tube columns

Eight concrete-filled steel tubular(CFT) columns were tested subjected to cyclic loading under constant axial load. Experimental parameters included axial compression ratio, loading sequences, and strength of concrete and steel. The seismic performance of CFT columns and failure modes were analyzed. The test results show that different axial load ratios and loading sequences have effects on the load carrying capacity, ductility and energy dissipation capacity of CFT columns, as well as the failure modes of the CFT columns. The failure pattern can be categorized into two types: local buckling failure of steel tube in compression zone, and low cycle fatigue tearing rupture failure of steel tube. The seismic behavior was evaluated through the energy index obtained from each cycle.

Mechanical property of single-bolted composite laminates

In order to investigate the effects of different geometrical parameters and pretightening loads on failure mode and bearing strength,a large number of single-bolted T300/QY8911 composite laminates were tested under static tension load.Box-plot was used to extract the singular testing values of bearing strength and effective statistical values were obtained.T-test method of independent samples was used to study how much pretightening loads influence bearing strength.The results show that the geometrical parameters,such as ratios of width to hole diameter(w/d) and edge distance to hole diameter(e/d),remarkably influence failure mode and bearing strength.Net-section failure will occur when w/d is smaller than 4,and shear-out failure will occur when e/d is smaller than 2.Bearing failure or bearing and shear-out combined failure will occur when w/d is greater than 4 and e/d is greater than 2.There is an optimal combination of geometrical parameters to achieve the highest bearing strength.For most of specimens,pretightening loads do not explicitly influence bearing strength.

拓宽桥梁新旧基础不均匀沉降及其对上部结构影响的研究

随着城市化进程的不断推进,人们在出行中对道路的要求越来越高,出于节约用地、保护环境、节约造价的目的,我国桥梁的发展开始进行拼宽设计,T梁截面存在整体性能好、截面刚度大、承载能力强的特点,在桥梁设计中取得了较好的应用效果。因此,对拼宽桥进行结构分析和性能研究具有重要的理论意义和实际价值。通过对案例进行研究,分析了不同工况下,新桥的主梁变形情况和拼接处内力变化情况,通过以上研究表明:采用弱刚接和强刚接时,新桥主梁和边梁的变形情况、拼接处内力变化情况均不同,本次研究为拼宽桥的应用与发展提供了理论依据和分析方法。