Controlling interstory drift ratio profiles via topology optimization strategies

An approach to control the profiles of interstory drift ratios along the height of building structures via topology optimization is proposed herein. The theoretical foundation of the proposed approach involves solving a min–max optimization problem to suppress the maximum interstory drift ratio among all stories. Two formulations are suggested: one inherits the bound formulation and the other utilizes a p-norm function to aggregate all individual interstory drift ratios. The proposed methodology can shape the interstory drift ratio profiles into inverted triangular or quadratic patterns because it realizes profile control using a group of shape weight coefficients. The proposed formulations are validated via a series of numerical examples. The disparity between the two formulations is clear. The optimization results show the optimal structural features for controlling the interstory drift ratios under different requirements.     

Probabilistic stability of uncertain composite plates and stochastic irregularity in their buckling mode shapes: A semi-analytical non-intrusive approach

In this study, the mechanical properties of the composite plate were considered Gaussian random fields and their effects on the buckling load and corresponding mode shapes were studied by developing a semi-analytical non-intrusive approach. The random fields were decomposed by the Karhunen−Loève method. The strains were defined based on the assumptions of the first-order and higher-order shear-deformation theories. Stochastic equations of motion were extracted using Euler–Lagrange equations. The probabilistic response space was obtained by employing the non-intrusive polynomial chaos method. Finally, the effect of spatially varying stochastic properties on the critical load of the plate and the irregularity of buckling mode shapes and their sequences were studied for the first time. Our findings showed that different shear deformation plate theories could significantly influence the reliability of thicker plates under compressive loading. It is suggested that a linear relationship exists between the mechanical properties’ variation coefficient and critical loads’ variation coefficient. Also, in modeling the plate properties as random fields, a significant stochastic irregularity is obtained in buckling mode shapes, which is crucial in practical applications.     

沿海非传统农区县域聚落空间演化研究 —— 以浙江省宁海县为例

县域是城乡融合发展的重要载体。随 着中国城镇化进程的加快,沿海非传统农区县 域聚落空间也发生了剧烈变化。本研究以浙江 宁海县为例,综合运用中心地理论、位序规模法 则、分形维数等理论方法,分析1990—2020年 浙江宁海县域聚落空间演化特征。结果发现：宁 海县域聚落空间演化规律与典型农作区差异明 显,趋向于城市发展规律,但因为县域人口和经 济发展的局限性,与城市特征仍有差距;聚落规 模沿中心轴线高核聚集,三门湾区点状高核突 出,镇乡职能明确,形成了较为稳定的多中心网 络等级结构;同时宁海县域聚落通过四种演化 方式向外扩张。探究非传统农区县域聚落规模 分布的演变规律,构建聚落等级体系,对县域聚 落体系的优化和城乡融合发展具有重要意义。     

景感生态学研究进展及其对人居环境科学的启示

面对中国城镇化中后期的发展需求,中 国人居环境科学亟需建立科学共同体,探寻基 于共性科学问题解决的认知方法和技术解决方 案。景感生态学（landsenses ecology）作为近年 来生态学发展较快的分支之一,以生态学基本 原理为基础,继承了中国传统人居营建优良传 统,对我国人居环境科学的发展具有重要借鉴 意义。首先,明确了景感生态学具有学科融合、 技术支撑与多尺度空间实践引导的基本特征, 将景感生态学的核心思想归纳为人感尺度的生 态特征与以人为本的景感营造。其次,解构了景 感生态学的技术方法,总结了物联网、趋善化模 型、生态信息数据系统等多种技术方法在土地 利用规划、建设与管理中的应用途径。进而,探索了景感生态学对我国人居环境科学的重要启示：生态过程与人类感知的全尺度交互;从分散到 融合的多源数据信息优化;从景观到景感的空间营造思维转变。     

文化资本视角下历史街区再生理念、框架和策略 ——以日本高山城下町和南京小西湖历史街区为实证

历史街区拥有保护和发展的双重要义, 历史街区再生需要平衡好利用好城市中的文化 力、经济力和社会力,在人文价值、当代需求和 持续发展之间找到可操作的秩序路径。基于 此,论文回归历史街区活态遗产的人文社会属 性,从“作为城市文化资本的历史街区”切入研 究,重点围绕街区遗产资源的价值潜力,架构了 历史街区再生解释框架,并在此框架下结合对日 本高山和南京小西湖两个历史街区再生案例的 审视分析,探讨了文化资本增量积累下的历史街 区再生策略。研究明晰了建成遗产作为可持续再 生驱动力的价值作用,为本土实践提供了新的思 想和方法借鉴。     

填海造地区域绿地系统存量修补策略研究 ——以天津市滨海新区绿地系统为例

国内多数滨海城市的填海造地历程 曲折,均经历过粗放式的“野蛮生长”过程, 到如今填海造地区域土地已渐趋饱和状态。 但是,由于过去的土地错位发展,其绿地系 统普遍存在规模不连续、开放共享性不足、 生态脆弱、防灾性能差这四类问题。以天津 市滨海新区填海区域土地利用与绿地系统为 例,提出建立“存量绿色土地库”,对填海造 地区域的存量土地进行生态修补。     

城市绿色空间健康效益的社会生态调节因素研究

城市绿色空间是城市生态系统服 务的重要载体。既往人—境交互视角下的 大量研究基本证实了绿色空间的健康效 益,但对影响二者间效益转化的调节因素 缺乏深入研究。根据社会生态理论与相关 研究,从社会人口和物质环境两方面定性 分析了调节因素及其作用机制,即社会生态 调节因素通过影响使用动机、使用机会或 易用性来影响绿色空间使用并由此调节健 康效益。进一步,基于城市游园研究案例对 此予以实证。结果显示,游园使用具有一定 的情绪健康改善作用,但此过程受到使用 者年龄、教育程度、收入水平、家庭结构以 及游园使用距离等因素的调节。面对不断 凸显的公共健康问题和愈发紧缺的绿色空 间,未来相关研究的焦点有必要从“绿色空 间是否影响健康”的基础研究转向包括调 节过程在内的“绿色空间如何影响健康”的 应用研究,以有效提升应用实践效率。     

Particle loss: An initial investigation into size effects and stress-dilatancy

Drained triaxial tests have been performed to explore the effect of particle loss on shearing behaviour and critical states in granular mixtures. The mixtures comprise Leighton Buzzard sand (d₅₀ = 0.8 mm), to which was added 15% by mass of salt particles of different nominal sizes: 0.063 mm, 0.25 mm and 0.5 mm. Shearing behaviours before and after particle loss (by dissolution) were compared. A good fit is observed between the test data and a stress-dilatancy relationship for the post-dissolution tests, highlighting the ability of the stress-dilatancy analysis as a means to interpret the effects of particle loss on shearing. It was noted that critical state strength parameter M is determined by the post-dissolution grading regardless of size of removed particle. However, the duration of contractant volumetric strain increased with the larger removed particles (0.25 mm & 0.5 mm) even when initial specific volumes were virtually identical. It is suggested that a loose volumetric state is reached if the sand particle network is initially disrupted by the amount and/or size of salt particles, which following dissolution results in structural or fabric phenomena that are not reflected in scalar volumetric measures such as specific volume.     

Characterizing the effects of fines on the liquefaction resistance of silty sands

Recent earthquakes in New Zealand and Japan indicate that evaluating the liquefaction potential of silty sands remains an area of difficulty and uncertainty in geotechnical engineering. This paper presents a comprehensive experimental study along with analysis and interpretation in the framework of critical state soil mechanics, with the aim to address the complicated effects of fines. Two series of sand-silt mixtures, formed by mixing two different base sands with the same type of non-plastic silt, were tested under a range of packing density, confining pressure and silt content, and a unified correlation was established between the cyclic resistance and the state parameter that collectively accounts for the effect of packing density and confining pressure. The proposed correlation is independent of packing density, confining pressure, fines content and base sand, and allows prediction of the cyclic resistance of silty sands under different states. Furthermore, the mechanism of the fines-content induced reduction of cyclic resistance and the mechanism of the base-sand effect observed from the tests are elaborated in the sound theoretical context. The present study suggests that the critical state soil mechanics is a rational and appealing framework for liquefaction analysis of both clean and silty sands.     

英国乡村规划空间尺度的经验与启示

英国拥有完善的城乡规划体系,关于乡村规划空间尺度的研究成果与实践经验非常丰富。文章从英国乡村问题与规划尺度之关系出发,系统梳理了英国乡村规划发展演变的几个阶段和几种类型,总结了英国乡村规划空间尺度的特征,一是乡村问题有多个层次,二是乡村问题的空间尺度决定了规划尺度,三是英国乡村规划已经形成体系。通过分析中英乡村问题的共同特征,得出英国经验对我国乡村规划的参考和启示,建议扩大乡村规划的对象,扩大乡村规划作为区域规划的特征,深入分解乡村问题、制定规划目标,以及依据乡村问题尺度选择合适的规划尺度,以解决目前我国乡村规划的困境。