Research on newly urbanized towns and districts in China

Since the last decade the central government endeavors to promote large scale of urbanization in China. Lots of new urban towns and districts are taking shape. Outline of the 12th Five-year Plan released by the central government points out that the new towns and districts are to be regulated. But few researches are considering the new towns and districts especially in the spatial distributive pattern and status in China. Given this situation this paper, after sorting out the world-wide research and development of new urban towns and districts, gives definitions of broad and narrow meanings. Based on the broad meaning definition, the database of new towns and districts in China is established. This paper then conducts a preliminary analysis of the new towns and districts. Then the two-step work plan and the advices are also proposed to further improve the research and practice of its kind in China.     

珠江黄埔大桥北汊主桥设计

广州珠江黄埔大桥北汉桥主桥采用独塔双索面钢箱梁斜拉桥,跨径组成为383 m+322 m,锚跨与主跨跨径比为0.840 7,主跨跨度在同类桥型中居国内第一、世界第三.独塔斜拉桥结构采用半漂浮支承体系;主梁采用单箱三室扁平流线形栓焊钢箱梁,主梁横隔板在国内大跨径斜拉桥中首次采用整体性好、抗扭刚度大的整体板式结构;索塔采用门形索塔、钢筋混凝土结构;斜拉索采用热挤聚乙烯高强钢丝拉索,在粱端设外置黏性剪切阻尼器防风雨振.     

对美国桥梁规范"体外预应力筋极限应力计算公式"的改进意见

修订后的美国AA SHTO LRFD桥梁设计规范和AA SHTO阶段预制混凝土桥梁设计与施工规范,采用基于变形的体外预应力筋极限应力计算公式代替了原来的基于粘结折减系数的体外预应力筋极限应力计算公式。本文剖析了这一转变的原因,并针对美国桥梁规范体外预应力筋极限应力计算公式中,较为繁琐的中性轴高度计算进行了简化。在此基础上,建议了与我国现行公路桥梁规范材料分项系数相适应的体外预应力筋极限应力计算公式,并给出了计算示例。     

珠江黄埔大桥北汊斜拉桥稳定性分析

珠江黄埔大桥北汉桥为独塔双索面钢箱梁斜拉桥.斜拉桥总体上届于缆索承重结构,但其主要组成部分中的索塔以及加劲梁是以受压为主的压弯构件,特别是薄壁钢箱梁斜拉桥,它们的稳定性对其结构的安全是至关重要的.考虑非线性影响后的稳定分析将强度和稳定两方面联系起来考虑,能真实地描述结构实际受力特性.同时考虑材料非线性与几何非线性对斜拉桥的稳定性影响最大,其稳定安全系数约为弹性稳定安全系数的35%～38%.     

装配式预应力混凝土箱形连续梁桥通用设计图成套技术

结合新版通用图,分析装配式预应力混凝土箱形连续梁桥通用图目前设计、施工以及应用中存在的主要问题,研究装配式箱梁的计算分析方法,对比分析横向分布系数法和梁格法计算结果的差别,研究分析了箱梁的合理梁高和腹板尺寸,系统地剖析了现行通用图在钢束设计、断面设计、其他构造处理等方面的技术改进.     

Evolution assessment of china’s three mega-city regions based on entire-array-polygon method

Mega-city region is the mainstream of global urban development and also the dominant model of the neo urbanization process in China. The Beijing-Tianjin-Hebei area, Yangtze River Delta area and Pearl River Delta area are China＇s three largest and most mature mega-city regions, the status of which represents the general level of the urban and regional development in China. Based on entire-array-polygon method, this paper makes a comprehensive evolution assessment of the three mega-city regions in terms of urban population index, urban economy index, urban life index, urban culture index and urban primacy index. In terms of general developing level, the three mega-city regions have progressed to optimize the structure. With their respective advantages and disadvantages, the three mega-city regions initially realize a ＂diversified＂ regional layout. The difference and gap among the three mega-city regions are obviously decreasing, which contributes to the regional balance of China metropolitan development. The rankings of the three mega-city regions will be in a continuous adjustment. The Beijing-Tianjin-Hebei area is possible to catch up and take the lead.     

大跨径混凝土梁桥体外预应力加固技术

跨中长期下挠和梁体开裂是大跨径混凝土梁桥的常见病害,病害的存在与发展导致桥梁维修养护费用的大幅增加、破坏桥梁美观、严重影响交通和结构安全。采用体外预应力加固技术受力明确、安全,对抑制跨中下挠、控制裂缝,能起到明显的作用。在分析病害特点及成因基础上,通过对两座主跨超过200 m的刚构桥加固实践的总结,提出了针对性措施和体外预应力体系使用建议,供同行参考。     

文化城市与中国城市发展方式转型及创新

新中国的政治型城市化,在本质上是一种以政治理念和意识形态需要为中心、一切服从于国家政治需要与政治利益、带有浓郁"逆城市化"特点的城市化模式.经济型城市化是以GDP为中心、一切服从于发展经济生产力的城市发展模式,社会主义市场经济模式的确立、城市经济的改革开放、城市商业与服务功能的全面复兴以及城市建制与城市人口的迅速扩张,构成了经济型城市化进程的基本特征.以城市文化为核心的文化城市是最能体现人类文明发展高度的新型城市,是兼顾了传统与未来、最适合人居需求的科学与全面发展的城市模式.     

世界著名大跨径桥梁一览

篇中汇集了截止1998年完成或在建的世界著名大跨径桥梁的有关资料.下表按结构体系和建筑材料予以排列.     

预制节段拼装混凝土桥墩力学性能研究进展

预制拼装桥墩具有质量有保证、施工速度快、干扰小、环保等优点,是装配式桥梁进一步发展的方向。分别从试验研究、理论研究和实际工程应用三个方面进行归纳总结,对预制拼装桥墩的抗震性能、节段接头、后张预应力系统、桥墩断面、耗能装置和塑性铰区设置的研究结果和实桥应用进行了分析,进而对亟待研究的问题和进一步研究的方向进行了展望。