开孔钢板加劲型方钢管混凝土长柱轴压性能试验研究

为研究开孔钢板（PBL）加劲型方钢管混凝土长柱的受力性能,完成了4个PBL加劲型方钢管混凝土长柱轴压试验。分析PBL加劲肋对不同长细比柱破坏模式、纵向应变、环向应变和承载力等的影响。结果表明：设置PBL,既可以发挥加劲肋的作用,有效防止加劲部位钢管的鼓曲,使横向鼓曲波长变短甚至出现“双波”,套箍作用明显;同时,还具有剪力连接件的作用,PBL与混凝土黏结良好,未出现PBL与混凝土剥离现象;基于CECS 159:2004《矩形钢管混凝土结构技术规程》,给出PBL加劲型方钢管混凝土长柱承载力计算式,其计算结果与试验结果比较吻合良好。     

The relation between the state indices and the characteristic features of undrained behaviour of silty sand

The characteristic features of a series of isotropically and K₀-consolidated undrained triaxial compression behaviour of a silty sand were investigated for a range of initial void ratio ($e)$ and mean effective confining stress ($p^{\prime }$). The silty sand used in this study contained about 10% natural fines. The critical state line (CSL) of K₀-consolidated specimens, K₀U was slightly lower than the CSL for isotropically consolidated specimens, CIU. The respective CSLs for K₀U and CIU were used to define state indices, such as state parameter ($\psi )$, state index ($I_s$), state pressure index ($I_p$) and modified state parameter (${\psi }_m$), within critical state soil mechanics (CSSM) framework. It was found that each state index exhibit a unique relation with liquefaction potential, irrespective of consolidation type, however different relationships were observed between state indices and the stress ratio at the triggering of liquefaction, ${\eta }_{\mathit{IS}}$ or the liquefaction resistance, $q_{\mathit{IS}}$. The correlation of characteristic features of undrained shearing (i.e., liquefaction potential, ${\eta }_{\mathit{IS}}$ and $q_{\mathit{IS}}$) and drained shearing (maximum rate of volume change, ${\left(d{\epsilon }_v/d{\epsilon }_a\right)}_{\mathit{m}\mathit{a}\mathit{x}}$) with state indices were compared statistically in terms of root mean square deviations (RMSD). All characteristic features of undrained shearing generally showed the best correlation with $I_p$ in term of RMSDs, however $\psi$ showed comparatively wider scatter for the specimens showing flow and limited flow behaviour.     

Local buckling of steel equal angle members with normal and high strengths

Steel angle sections have been widely accepted with the development of steel structures, and such members made by high strength steel (HSS) sections are also increasingly used in buildings and bridges, and especially in transmission towers and long span trusses. Compared to normal strength steels, HSS exhibits different mechanical properties, which can cause different local buckling behavior. A finite element analysis (FEA) was performed in this paper to investigate the local buckling of steel equal angle members with different strengths under axial compression, where the residual stresses and the initial geometric imperfections of specimens were accurately described. Through this work, the relationship of the ultimate local buckling stress of steel equal angle members under axial compression as a function of steel strength and width-to-thickness ratio was established. By comparing the FEA results with the international design specifications (ANSI/AISC 360-10 and Eurocode 3), a modified design formula was developed and corresponding design suggestions were proposed, to take into account the effects of steel strength.     

Plastic energy evaluation of bilinear SDOF systems with fluid viscous dampers

Current seismic practices are more concerned with dissipating a significant portion of seismic input energy than with lateral load resistance, as well as with determining seismic demands of structures using response spectra. This study aims to improve the knowledge of the plastic energy spectra ( $E_P$) of single-degree-of-freedom systems (SDOF) equipped with fluid viscous dampers (FVDs). This type of dampers is characterized by its supplemental damping ratio ${\xi }_{\mathit{add}}$ and velocity power $\alpha$. Using nonlinear dynamic analyses, the $E_P$ and its ratio to the input energy ( $E_P/E_I$) are determined using near-field-pulse, near-field-non-pulse and far-field ground motions. Parametric studies are conducted to investigate the effect of ground motion types, original system features and FVD characteristics on $E_P/E_I$ spectra. The results show that ground motion types have a considerable influence on the $E_P/E_I$ for systems with FVDs, while they are not effective for systems without FVDs. Increasing FVD nonlinearity (decreasing α) is more effective to reduce the $E_P/E_I$ under near-field-non-pulse and far-field motions than under near-field-pulse ground motions for structures with $T_n$ > 1 s. The paper further developed a prediction equation for estimating $E_P/E_I$for SDOF systems without and with FVDs, which can serve as a useful tool to analyse structural damage for energy-based seismic design.     

Application of generalized regression neural network method for corrosion modeling of steel embedded in soil

In this work, a generalized regression neural network (GRNN) model is used to predict the corrosion potential values and corrosion current densities of ASTM A572-50 steel specimens embedded in nine soils with different physiochemical properties, i.e., pH, moisture content, resistivity, chloride content, sulfate and sulfite contents, and mean total organic carbon concentration. Experiments were conducted, and the corrosion current densities and corrosion potential values of the steel specimens embedded in the different soils were measured. The results obtained with the GRNN model agreed very well with the results of the experiments, suggesting that the proposed model is capable of predicting the corrosion activity of steel specimens embedded in different soils.