Mexico City as a peripheral global player: The two sides of the coin

This article considers the effects of globalization on Mexico City, as well as whether this urban area, one of the largest in the world, can be considered a global city. We base our arguments on a number of scales of analysis suggested in the literature on these topics. At the international scale, we look at the increased concentration of corporate headquarters and air traffic flows in the city. In terms of its role in the national urban system, we argue that while domestic migration patterns have shifted toward other destinations, the majority of domestically produced merchandise continues to find its way to the capital. At the metropolitan scale, our analysis suggests increasing spatial segregation, as well as longer commutes. At the intraurban level, we find that the sectoral composition of jobs has shifted toward commercial and service sectors, the informal sector has expanded, the labor force is polarizing, and that high-level service sector growth is spatially concentrated. In view of these findings, we suggest that the effects of globalization on Mexico City are mixed, as it consolidates its position as a second-tier global city. We also argue that, in spite of welcome steps toward democratization, pre-existing income inequalities in the country have accentuated the socio-economic polarization predicted by the literature on global cities and globalization, giving rise to a megacity with two very distinct sides. The authors would like to recognize Emelina Nava and Raul Lemus at El Colegio de México and Irma Escamilla and Josefina Hernández at the Institute of Geography, UNAM, for their participation in data management and producing tables and maps.     

计算四边支承圆管式空心楼板的两种简化方法

采用ANSYS有限元软件分析几种不同规格的空心板,阐述空心板是正交各向异性(等效刚度)板.采用两种简化方法求解四边支承圆管空心板,一种方法求解出正交各向异性板单元的刚度矩阵中各项参数,采用有限元对空心板进行分析;另一种方法采用SAP2000软件依据两方向刚度相等原则将空心板等效成井字梁分析,从而求出两方向梁的内力.两种方法均具有较高精度,并列举实例说明.     

Optimum design of the sides of a railroad car

The paper describes the application of a general purpose optimization code, PARS to the design of the sides of a 100 ton high side gondola car. PARS (Program for Analysis and Resizing of Structures), a companion code to the SPAR finite element package, is used for optimizing structures modelled by finite elements. The optimization algorithm uses an extended $\text{interior}$ penalty function and Newton's method for unconstrained minimization.The sides of the gondola car are modelled by beam and plate finite elements. Manufacturing requirements are accounted for by design variable linking and the side are designed subject to stress buckling and displacement constraints. The design is according to the specifications for design, fabrication and construction of freight cars recommended by the Association of Americal Railroads.     

业主方在工程管理中的目标控制

通过协调各工程参与方关系、调动监理工程师作用、做好材料认质认价、加强安全管理等四种管理方法,以做到合理缩短工期、降低工程投资、安全文明生产,最终达到提高工程建设水平,充分发挥投资效益的总体目标。     

装载机双向侧卸工作装置

装载机双向侧卸工作装置是在装载机前端配置既可正向也可左右侧向卸料的多功能新型机具，文章主要对其结构组成、工作原理、操作使用和日常保养等几方面做了详细介绍。     

浅谈基坑侧壁安全等级的确定方法

基坑侧壁安全等级的划分是对支护设计、施工的重要性认识及计算参数的定量选择,是一个难度很大的问题。根据基坑安全等级并结合地区经验及相关规范,可以初步选定基坑支护方法,并为基坑监测项目选用提供依据。     

双侧壁向CRD转换施工工艺浅析

分别对双侧壁导坑法及CRD法的施工特点、施工工序进行了介绍,并对双侧壁与CRD开挖方法进行了分析对比,结合工程实例,对双侧壁向CRD工法的成功转换方案及过渡施工步骤进行了阐述,从而对施工进度和施工成本的有效控制具有重要的意义。     

重视瑞赣高速公路路侧安全

从1988年我国大陆第一条高速公路正式通车到现在,我国的高速公路建设取得了举世瞩目的成就."十五"期间我国共建成高速公路2.47万千米,是"八五"高速公路的总和和"九五"的1.5倍.全国高速公路通车总里程先后跃上了2万千米、3万千米、4万千米3个大台阶.到2005年底,高速公路总里程达到4.1万千米,位居世界第二位.     

反观木在中国传统建筑文化中的情结

主要是针对"木"在中国传统建筑文化中的反面探讨,从五个方面分析了"木"存在的缺点,然后指出要辨证地看待"木"在中国传统建筑中的作用,以便更好地继承与发展"木"在现代建筑设计中的应用与实践。     

高填方加筋边坡中竹筋的应用初探

简要介绍了加筋土的特征,并结合攀枝花学院内高填方土质加筋边坡中采用加竹筋的工程实例,介绍了加竹筋边坡的施工工艺及质量控制要点,对已建成的边坡进行沉降观测,并同普通挡墙、普通加筋挡墙的经济性进行了对比分析,最后对加竹筋边坡的应用前景进行了展望。     

浅谈线路两侧山体崩塌后的防护整治

根据工程施工中线路两侧山体崩塌的现象,对崩塌原因进行了分析,从地形地貌、地质因素、人为因素等方面进行了论述,提出了整治方法,进行了防护墙的研究,达到了防护山体崩塌的效果,解决了山体崩塌的整治问题.     

钱塘江两岸深基坑突涌问题分析

结合多个钱塘江两岸地下三层(及以上)的基坑项目,探讨了杭州地区深基坑的突涌问题。分析了土体抗剪强度在抗突涌中的作用,提出了相应的技术处理措施,其中详细分析了采取满堂加固形式处理突涌的措施。计算结果表明,土体抗剪强度在抗突涌中发挥了较大作用,挖土中采用分块施工可有效提高抗突涌能力。     

Blind bolted moment connection to sides of hollow section columns

This paper presents the results of an experimental programme for a new blind bolted connection to unfilled hollow section (HS) columns under static loading. In this connection, channels with side plates connect beam flanges to the side face of HS columns. This is a simple alternative connection to typical face connections, i.e. the extended endplate connection or the T-stub connection (with T-stubs connecting the top and bottom flanges of the beam to the face of the column). The channel side plate connection was found to be much stiffer than a typical face connection and has the potential to achieve a rigid connection status for braced frames according to the EC3 classifications. Comparison of the test results and three dimensional finite element (FE) modelling indicates that the FE analyses can be used to predict the connection behaviour with sufficient accuracy. The preliminary investigation for the channel side plate connection shows promising results and forms the basis for the development of other blind bolted side connections for applications in the low rise construction industry.     

Blind bolted moment connection to sides of hollow section columns

This paper presents the results of an experimental programme for a new blind bolted connection to unfilled hollow section (HS) columns under static loading. In this connection, channels with side plates connect beam flanges to the side face of HS columns. This is a simple alternative connection to typical face connections, i.e. the extended endplate connection or the T-stub connection (with T-stubs connecting the top and bottom flanges of the beam to the face of the column). The channel side plate connection was found to be much stiffer than a typical face connection and has the potential to achieve a rigid connection status for braced frames according to the EC3 classifications. Comparison of the test results and three dimensional finite element (FE) modelling indicates that the FE analyses can be used to predict the connection behaviour with sufficient accuracy. The preliminary investigation for the channel side plate connection shows promising results and forms the basis for the development of other blind bolted side connections for applications in the low rise construction industry.     

建筑工地制订各方共同制度问题研究

结合自身工作实践,对建筑工地各方共同制度的制订进行了研究,分析了制定各方共同制度的作用及必要性,分别阐述了制定各方共同制度的做法及内容提要,对保证工程有序进行具有积极意义。     

如何规避合同风险搞好工程结算

从建设工程合同风险的识别方法、风险类别、风险表现形式等问题的分析入手,着重探讨了防范或规避合同风险的对策,为做出公平公正的工程竣工结算提供了有效的方法与措施.     

关于穿变形缝两侧的通风管道防火阀设置问题的探讨

针对相关设计规范对风管穿变形缝处设置防火阀的规定,认为应根据变形缝两侧防火分隔的不同情况及防火阀在火灾时的作用合理设置。     

Static strength of axially loaded EHS X-joints with braces welded to the narrow sides of the chord

Experimental tests and finite element (FE) studies have been carried out to investigate the static behaviour and strength of axially loaded X joints between elliptical hollow sections (EHSs) with braces welded to the narrow sides of the chord. The numerical results are in agreement with those obtained from the experiments. Based on the results of a numerical parametric study, an equation is derived to estimate the static strength. The equation is formulated in a similar way to that currently adopted for circular hollow section (CHS) joints for chord plastification. The design strength can be determined according to the procedures used in the IIW and CIDECT recommendations.     

无机保温材料的六面全自动切削加工

伴随社会发展及科学技术的进步,针对目前保温包装材料切削加工中现有的加工工序存在的繁琐和不足,进行综合设计与改进。经过优化设计的新型机床能够全自动、快速实现立方体工件六个表面的切削加工,以满足机械加工需求。文章同时重点阐述了该切削机床的核心机构—自动翻转装置的工作原理,可推广用于类似机床的设计。     

木柱四面受火后力学性能的试验研究

木柱受火后截面演化为三个区域:外侧为漆黑的炭化层,承载力完全丧失;中间为深灰的高温分解层,承载力明显劣化;内部为颜色不变的正常层,承载力无变化。通过5组24根木柱四面受火后力学性能的对比试验研究,了解不同受火时间后木柱剩余承载力、延性、破坏形态和炭化速度的变化过程。研究结果表明,受火后木柱剩余承载力显著降低,受火木柱的初始刚度均明显低于对比试件,部分截面较小的受火木柱发生偏压破坏。四面受火后木柱承载力下降原因主要包括:受火使木柱表面炭化,木柱有效面积减小;受火后靠近炭化层的高温分解层木材强度明显劣化;随着受火时间增加,木柱截面长细比增加导致其稳定系数降低;部分木柱由于局部裂缝使炭化不均,使受火后木柱的破坏形态由轴压转变为偏压破坏。受火木柱表面有裂缝处及角部的炭化速度加大;随着含水率降低,炭化速度有所增加;随着受火时间增加,炭化速度有所降低。