白云石循环法生产氧化镁新工艺的研究

介绍了用循环法从白云石中制取氧化镁的新工艺,制得的工业氧化镁达到了ＨＧ／Ｔ２５７３－９４的质量要求。     

Large-scale flow and transport of magnetic flux in the solar convection zone

Horizontal large-scale velocity field describes horizontal displacement of the photospheric magnetic flux in zonal and meridian directions. The flow systems of solar plasma, constructed according to the velocity field, create the large-scale cellular-like patterns with up-flow in the center and the down-flow on the boundaries. Distribution of the largescale horizontal eddies (with characteristic scale length from 350 to 490 Mm) was found in the broad equatorial zone, limited by 60‡ latitude circles on both hemispheres. The zonal averages of the zonal and meridian velocities, and the total horizontal velocity for each Carrington rotation during the activity cycles no. 21 and 22 varies during the 11-yr activity cycle. Plot of RMS values of total horizontal velocity is shifted about 1.6 years before the similarly shaped variation of the magnetic flux.     

纤维增强混凝土异形柱框架抗震性能的试验研究

通过薄弱部位应用纤维增强的混凝土异形柱框架和同条件下无纤维异形柱框架的拟静力试验研究,对比了两榀框架的破坏特征、出铰顺序、承载能力和延性、滞回特性、耗能能力及刚度退化等抗震性能指标。研究表明：应用纤维增强的异形柱框架承载能力和整体刚度显著提高,薄弱部位破坏程度减轻,耗能能力有所增强,纤维可以改善异形柱框架薄弱部位的抗震性能,提高异形柱框架结构的整体抗震能力。     

Influence of deterioration modelling on the seismic response of steel moment frames designed to Eurocode 8

This paper assesses the influence of cyclic and in‐cycle degradation on seismic drift demands in moment‐resisting steel frames (MRF) designed to Eurocode 8. The structural characteristics, ground motion frequency content, and level of inelasticity are the primary parameters considered. A set of single‐degree‐of‐freedom (SDOF) systems, subjected to varying levels of inelastic demands, is initially investigated followed by an extensive study on multi‐storey frames. The latter comprises a large number of incremental dynamic analyses (IDA) on 12 frames modelled with or without consideration of degradation effects. A suite of 56 far‐field ground motion records, appropriately scaled to simulate 4 levels of inelastic demand, is employed for the IDA. Characteristic results from a detailed parametric investigation show that maximum response in terms of global and inter‐storey drifts is notably affected by degradation phenomena, in addition to the earthquake frequency content and the scaled inelastic demands. Consistently, both SDOF and frame systems with fundamental periods shorter than the mean period of ground motion can experience higher lateral strength demands and seismic drifts than those of non‐degrading counterparts in the same period range. Also, degrading multi‐storey frames can exhibit distinctly different plastic mechanisms with concentration of drifts at lower levels. Importantly, degrading systems might reach a “near‐collapse” limit state at ductility demand levels comparable to or lower than the assumed design behaviour factor, a result with direct consequences on optimised design situations where over‐strength would be minimal. Finally, the implications of the findings with respect to design‐level limit states are discussed.     

配置630 MPa级高强钢筋的混凝土柱抗震损伤指数模型修正

为了验证各种Park-Ang损伤指数修正模型能否对630 MPa级超高强钢筋混凝土柱的地震损伤进行准确评估。在配置630 MPa级高强钢筋的混凝土柱拟静力试验现象和实测数据的基础上,首先利用6种模型分别计算了8根典型试件的损伤指数,并与试验实测损伤指数范围进行了对比,分析了6种模型的适用性;然后在试验实测数据的基础上,对计算结果存在较大偏差的4种模型进行了参数拟合和模型修正。研究结果表明:Kunnath模型、Chai模型、修正的傅剑平模型、修正的王东升模型和修正的付国模型均能准确模拟630 MPa级高强钢筋柱的损伤指数发展规律,而修正后的Kumar模型计算结果反而偏小,效果较差。     

装配式H型钢柱框架-复合墙结构抗震性能试验研究

提出了一种装配式H型钢柱框架-复合墙抗震结构。为研究结构的抗震性能,进行了1榀足尺装配式H型钢柱框架与1榀足尺装配式H型钢柱框架-复合墙试件的低周反复荷载试验。对比分析了各试件的强度、刚度、延性、滞回特性、耗能能力及破坏特征。研究表明:内嵌复合墙破坏时被分割成多条条型复合墙板,在弹塑性变形后期对框架的支撑作用较为稳定;内嵌复合墙使框架的极限承载力提高了68%,使框架的初始刚度提高了394%;H型钢柱框架-复合墙试件的滞回曲线饱满,未出现捏拢现象;条型复合墙板企口连接的水平条带存在往复咬合错动,对结构耗能能力的提升有明显贡献。     

Energy dissipation models for RC members and structures

The unloading parameters of hysteretic models for RC members are given in terms of their shear-span-to-depth ratio and the viscous damping used to model other energy dissipation sources. They reflect the energy dissipation in full post-yield load cycles in 534 tests of rectangular or circular members. Pre-yield hysteretic energy dissipation—ignored if the model is elastic till yielding—amounts in the tests to a mean viscous damping around 8.5% and can be considered in nonlinear response-history analysis through a new model which combines constant elastic stiffness in virgin loading with hysteretic energy dissipation both before and after yielding. Models with linear behavior till yielding and hysteretic energy dissipation only after it come closer to the results of the new model if viscous damping is 5%.     

Numerical investigation of the resistance of precast RC pinned beam‐to‐column connections under shear loading

In precast technology, the effective design and construction are related to the behaviour of the connections between the structural members in order to cater for all service, environmental and earthquake load conditions. Therefore, the design and detailing of the connections should be undertaken consistently and with awareness of the desired structural response. In the research presented herein, an analytical expression is proposed for the prediction of the resistance of precast pinned connections under shear monotonic and cyclic loading. The proposed formula addresses the case where the failure of the connection occurs with simultaneous flexural failure of the dowel and compression failure of the concrete around the dowel, expected to occur either when (i) adequate concrete cover of the dowels is provided (d > 6 D) or (ii) adequate confining reinforcement (as defined in the article) is foreseen around the dowels in the case of small concrete covers (d < 6 D). The expression is calibrated against available experimental data and numerical results derived from a nonlinear numerical investigation. Emphasis is given to identifying the effect of several parameters on the horizontal shear resistance of the connection such as: the number and diameter of the dowels; the strength of materials (concrete, grout, steel); the concrete cover of the dowels; the thickness of the elastomeric pad; the type of shear loading (monotonic or cyclic); the pre‐existing axial stress in the dowels; and the rotation of the joint. In addition, recommendations for the design of precast pinned beam‐to‐column connections are given, especially when the connections are utilised in earthquake resistant structures. Copyright © 2017 John Wiley & Sons, Ltd.     

Evaluation of horizontal stiffness of fibre‐reinforced elastomeric isolators

Unbonded fibre‐reinforced elastomeric isolator (U‐FREI) is relatively new seismic base isolator in which fibre layers are used as reinforcement to replace steel shims as are normally used in conventional isolators. Further, the top and bottom end steel connector plates of conventional isolators are also removed. In general, the horizontal response of U‐FREI is nonlinear because of reduction in contact area due to rollover deformation and reduction in shear modulus of isolator under large deformation. Thus, evaluation of horizontal stiffness of U‐FREI is a challenging problem. Most previous studies were focused on the investigation of horizontal response of scaled models of U‐FREIs with low shape factors. A few analytical approaches were suggested for predicting the horizontal response of U‐FREI; but their results were not in good agreement with experimental observations. In the present study, the horizontal responses of prototype U‐FREIs are evaluated under a constant vertical pressure and cyclic loading using both experiments and finite element analysis. Prototype U‐FREIs with different shear moduli and with different shape factors are considered. Finite element simulations of corresponding bonded FREIs are also performed under the same loadings as in U‐FREIs. A rational analytical approach including the influence of rollover deformation and simultaneous reduction in shear modulus is proposed as a basic analytical tool for predicting the horizontal stiffness of FREIs (both bonded and unbonded). It is in reasonably good agreement with the results obtained from experiments and numerical analysis. Copyright © 2017 John Wiley & Sons, Ltd.     

循环荷载作用下海床结构粉质土的液化渗流机理定性研究

通过对黄河三角洲海床粉质土的基本性质和循环荷载作用下的喷水冒砂现象的分析,认识了海床粉质土的结构性。利用岩土破损力学原理,建立了海床结构粉质土的二元介质模型。定性分析了结构带土体在加荷、卸荷、液化渗流过程中的变形破损和在液化渗流过程中有效应力和超孔隙水压力的相互转化,指出在液化深度内,土体恢复后的固结强度应提高。这与试验结果相一致。用二元介质模型对解释试验中液化渗流差异是结构带内出现喷水冒砂和结构体上出现遍地冒水现象。