Numerical evaluation of wind effects on a tall steel building by CFD

A comprehensive numerical study of wind effects on the Commonwealth Advisory Aeronautical Council (CAARC) standard tall building is presented in this paper. The techniques of Computational Fluid Dynamics (CFD), such as Large Eddy Simulation (LES), Reynolds Averaged Navier-Stokes Equations (RANS) Model etc., were adopted in this study to predict wind loads on and wind flows around the building. The main objective of this study is to explore an effective and reliable approach for evaluation of wind effects on tall buildings by CFD techniques. The computed results were compared with extensive experimental data which were obtained at seven wind tunnels. The reasons to cause the discrepancies of the numerical predictions and experimental results were identified and discussed. It was found through the comparison that the LES with a dynamic subgrid-scale (SGS) model can give satisfactory predictions for mean and dynamic wind loads on the tall building, while the RANS model with modifications can yield encouraging results in most cases and has the advantage of providing rapid solutions. Furthermore, it was observed that typical features of the flow fields around such a surface-mounted bluff body standing in atmospheric boundary layers can be captured numerically. It was found that the velocity profile of the approaching wind flow mainly influences the mean pressure coefficients on the building and the incident turbulence intensity profile has a significant effect on the fluctuating wind forces. Therefore, it is necessary to correctly simulate both the incident wind velocity profile and turbulence intensity profile in CFD computations to accurately predict wind effects on tall buildings. The recommended CFD techniques and associated numerical treatments provide an effective way for designers to assess wind effects on a tall building and the need for a detailed wind tunnel test.     

弦杆轴力作用下不等宽K型间隙方管节点性能研究

利用非线性有限元法对不等宽K型方管间隙节点进行了数值计算 ,揭示了此类节点在弦杆轴力作用下的极限承载力、变形、刚度等随各几何参数的变化规律 ,得出了轴向拉力和压力及相关几何参数对节点承载性能的影响的相关结论 ,可供工程设计参考     

厦门市区域地震地质特征

系统地探讨了厦门市的区域地震地质特征，调查分析了区域地震的时空分布及邻区地震活动及其对厦门的影响，详细考察了近场断裂带活动情况。研究表明，厦门岛内主要断层自第四纪晚更新世以来处于相对稳定状态；对厦门威胁最大的震害主要来自邻区海域的强震，历史上最大曾达Ⅷ度；台湾强震在厦门引起的影响迄今尚未超过Ⅵ度。     

燃气行业涨价行为的经济学视角分析

用经济学理论对燃气涨价这一经济现象进行了实证分析.文章论述了燃气涨价无法有效地达到既定目标;而且它会损害全社会的福利总量,降低了燃气行业对其目前的低效率改革创新的动力,不利于中国的经济发展.     

挥发性组分对熟料生产工艺的影响

本文综合研究了挥发性组分对熟料生产工艺的一系列重要影响及应有对策。过渡相的过量形成是预热系统内结皮和窑筒内结块的根本原因。含碱过高且熔体不足是飞砂料形成的根本原因。碱还严重地浸蚀通用的耐火材料。因此在使用挥发性组分含量很高的原、燃料时,应兼顾巧配熟料中的主要组分和次要组分,严格控制熟料中碱的硫酸盐化度和熔体含量,选用一系列耐碱侵蚀的耐火材料,使所制熟料和水泥的各项性能良好稳定。     

负温高强泵送混凝土配合比设计要点与方法

研究了负温高强泵送混凝土的负温硬化限及其配合比的设计要点与方法，并确定出Ｃ５０～Ｃ６０级负温高强泵送混凝土强度试配公式及其防冻剂掺量值计算公式，可供施工单位进行高强泵送混凝土冬期施工时参考。     

润扬大桥悬索桥索塔结构动力特性实测

润扬长江公路人桥是我国在建规模最大的索支承结构，索塔作为其中一个重要的结构组成部分，掌握其结构动力特性，可以完善理论分析模型，从而为全桥模型的建立和进一步建立润扬大桥结构安全健康监测系统提供最原始的指纹数据。本次测试是在严格符合各项操作规程的条件下，采用环境激励法完成的，在对测试数据进行统计分析后，获得了索塔结构动力特性，并在此基础上，修正了理论模型。然后，对模型进行了有限元模态分析，所得结果与测试结果比较，相当接近，误差极小，证实了理论模型的正确性和可靠性。并在实测结果和理论模型分析结果的基础上，建立了索塔的有限元杆系模型，通过对其进行模态分析，结果进一步论证了理论实体模型的精确性。     

Fatigue crack growth analysis of a square hollow section T-joint

Stress concentration sites are always found at the brace and chord intersection corners of any rectangular welded tubular joint. As a result, fatigue cracks are liable to be initiated and propagated from these corners. In this paper, the 3D fatigue crack growth under the weld toe of a square hollow section welded T-joint is simulated using boundary element method. In accordance with the 3D analyses, fatigue crack growth is predicted using a model based on the Paris’ law and stress intensity factors. Good agreement between the experimental and predicted crack growth and crack shape development is obtained. Based on this crack growth analysis, the fatigue life of a specimen is predicted and compared with the standard S-N curve for hollow section joints. It is found that the standard S-N curve is safe and slightly conservative.     

双排桩支护软粘土基坑开挖的有限元分析

双排桩支护结构是基坑围护结构的一种形式,但目前的分析方法无法考虑其与土体的共同作用。采用平面应变有限元方法研究了软粘土地基基坑开挖双排桩支护结构的性状,重点分析了桩土界面特性、前后排桩间距等因素对支护结构的内力和变形的影响。分析表明,当双排桩排距过小时,围护结构类似于悬臂式单排桩性质;当排距过大时,后排桩对前排桩起到类似拉锚桩的作用;只有当排间距为4d左右时,双排桩围护结构才能达到最好的效果。     

不同支杆轴力系数下空间KK型方管相贯节点的承载力研究

应用有限元法分析了不同支杆轴力系数的空间KK型方管相贯节点的承载力和变形,揭示了节点承载力和变形与支杆轴力系数间的关系,提出了空间KK型与平面K型节点承载力的比值随支杆轴力系数的不同而变化的观点,即支杆轴拉(压)力系数越大,空间节点承载力相对平面节点承载力的比值越小.