Influence of Structural Design on the Aeroelastic Stability of Brancusi’s Endless Column

Brancusi’s Endless Column (Targu-Jiu, Romania) is an interesting case study in bluff body aeroelasticity. It has been referred to as aeroelastically indifferent owing to its remarkable aeroelastic stability. This stability has been attributed to its unconventional shape. Calculations are presented which show that this strictly aerodynamic view of the column behavior is incomplete, and that the structural dynamics characteristics of the column have a powerful role in ensuring its aeroelastic stability. The calculations show that the column’s design, which provided for significant damping and mass, would assure its aeroelastic stability even if the column had a conventional and aeroelastically less favorable shape, i.e., if it were a circular cylinder (a shape that is unfavorable from the point of view of vortex-induced response) or a square cylinder (a shape that is unfavorable from the point of view of galloping).     

Exact Solution for Buckling of Columns Including Self-Weight

In this technical note, analytical solutions for the elastic buckling of heavy columns with various combinations of end conditions are derived, for the first time, in terms of generalized hypergeometric functions. The benchmark solutions may be used to assess the accuracy of approximate formulas and numerical solutions.     

Effects of State Legal Loads on Bridge Rating Results Using the LRFR Procedure

The main objective of this research was to study the effects of different specified trucks on bridge rating with the load and resistance and factor rating (LRFR) procedure. Twelve specified trucks were selected for this study, which include one AASHTO design truck, three AASHTO legal trucks, and eight state legal trucks. These rating trucks were applied on 16 selected Tennessee Dept. of Transportation bridges to obtain the LRFR ratings. The selected bridges covered four commonly used bridge types, including prestressed I-beam bridges; prestressed box beam bridges; cast-in-place T-beam bridges; and steel I-beam bridges. The research results revealed that (1) LRFR AASHTO legal load ratings factors were enveloped by the LRFR HL-93 truck ratings factors, thereby confirming the validity of the LRFR tiered approach with regard to AASHTO legal loads; (2) the lighter state legal trucks were enveloped by the HL-93 loads, whereas the heavier state trucks with closer axle spacing typically resulted in load ratings that governed over the HL-93 loads; and (3) the bridges with both high average daily truck traffic and short spans were more likely to be governed by state legal load ratings instead of HL-93 load ratings.     

Analysis of a simplified calibration procedure for 18 design-phase building energy models

This paper evaluates the accuracy of 18 design-phase building energy models, built according to LEED Canada protocol, and investigates the effectiveness of model calibration steps to improve simulation predictions with respect to measured energy data. These calibration steps, applied in professional practice, included inputting actual weather data, adding unregulated loads, revising plug loads (often with submetered data), and other simple updates. In sum, the design-phase energy models underpredicted the total measured energy consumption by 36%. Following the calibration steps, this error was reduced to a net 7% underprediction. For the monthly energy use intensity (EUI), the coefficient of variation of the root mean square error improved from 45% to 24%. Revising plug loads made the largest impact in these cases. This step increased the EUI by 15% median (32% mean) in the models. This impact far exceeded that of calibrating the weather data, even in a sensitivity test using extreme weather years.     

组焊圆柱壳在轴向载荷和局部热载荷共同作用下屈曲数值研究

对大型直立设备安装过程中的现场焊接热处理过程中在轴向载荷和局部热载荷共同作用下的屈曲问题进行数值研究。研究结果表明,在焊后热处理过程中加热部位的边缘附近区域存在很大的温度梯度,导致该部位有很大的热应力。在热处理过程中焊缝部位的热应力很小,与加热部位边缘附近区域相比几乎可以忽略不计。组焊圆柱壳在轴向载荷和局部热载荷共同作用下屈曲最先发生在加热部位的边缘附近区域;热处理过程中加热部位边缘存在的局部热应力是导致组焊圆柱壳发生屈曲的关键因素。最后分析了热处理过程中几个关键参数对组焊圆柱壳,临界屈曲载荷的影响。     

Characterisation of diffuse pollutions from forested watersheds in Japan during storm events - its association with rainfall and watershed features

Forest areas have been identified as important sources of nonpoint pollution in Japan. The managers must estimate stormwater quality and quantities from forested watersheds to develop effective management strategies. Therefore, stormwater runoff loads and concentrations of 10 constituents (total suspended solids, dissolved organic carbon, PO(4)-P, dissolved total phosphorus, total phosphorus, NH(4)-N, NO(2)-N, NO(3)-N, dissolved total nitrogen, and total nitrogen) for 72 events across five regions (Aichi, Kochi, Mie, Nagano, and Tokyo) were characterised. Most loads were significantly and positively correlated with stormwater variables (total event rainfall, event duration, and rainfall intensity), but most discharge-weighted event concentrations (DWECs) showed negative correlations with rainfall intensity. Mean water quality concentration during baseflow was correlated significantly with storm concentrations (r=0.41-0.77). Although all pollutant load equations showed high coefficients of determination (R(2)=0.55-0.80), no models predicted well pollutant concentrations, except those for the three N constituents (R(2)=0.59-0.67). Linear regressions to estimate stormwater concentrations and loads were greatly improved by regional grouping. The lower prediction capability of the concentration models for Mie, compared with the other four regions, indicated that other watershed or storm characteristics should be included in the prediction models. Significant differences among regions were found more frequently in concentrations than in loads for all constituents. Since baseflow conditions implied available pollutant sources for stormwater, the similar spatial characteristics of pollutant concentrations between baseflow and stormflow conditions were an important control for stormwater quality.     

Survivability of steel frame structures subject to blast and fire

The lesson learned from the terrorist attacks on buildings is the need to assure structures’ ability to sustain local damage without total collapse. Some of the terrorist attacks take the form of blast followed by fire which may cause catastrophic failure of the structure. This paper presents a numerical model for analyzing steel frame structures subject to localized damage caused by blast load and subsequently investigating their survivability under fire attack. The proposed numerical method adopts a mixed-element approach for modeling large-scale framework and it is proven to be sufficiently accurate for capturing the detailed behaviour of member and frame instability associated with the effects of high-strain rate and fire temperature. Design implications related to the use of various numerical models for separate assessment of blast and fire resistance of steel structures and their components are discussed. Fire–blast interaction diagrams are generated to determine the fire resistance of columns considering the initial damage caused by the blast loads. A multi-storey steel building frame is analyzed so that the complex interaction effects of blast and fire can be understood and quantified. The frame is found to be vulnerable, as it possesses little fire resistance due to the deformation of key structural elements caused by the high blast load.     

南京地区部分空调负荷设计土壤源热泵U形垂直地埋管的研究

根据南京地区空调负荷的特点介绍了南京地区土壤源热泵部分负荷设计地下垂直U形地埋管的可行性,改善土壤与U形管换热的情况,平衡冬夏季大地的得热与失热情况.介绍了地埋管与辅助冷却塔联合运行的方式,并将不同空调负荷设计U形地埋管时的初投资与地埋管占地面积进行了比较,得出在南京地区根据夏季空调最大负荷的50%～60%设计U形地下垂直埋管,并根据空调运行方式选择合理的辅助冷却塔容量匹配与运行方式是合理的.     

A quasi-correspondence principle for Quasi-Linear viscoelastic solids

In this paper we show that the correspondence principle that allows one to obtain solutions to boundary-initial value problems for Linear viscoelastic solids from solutions to that for a linearized elastic solid can be extended, in many circumstances, to the case of the Quasi-Linear viscoelastic solids introduced by Fung. We illustrate the ability to generalize the correspondence principle by considering a variety of problems including torsion, transverse loading of beams and several problems that involve a single non-zero stress component. This extension is however not possible for certain classes of problems and we present a specific example where the correspondence principle breaks down. The correspondence principle between Linear elasticity and Linear viscoelasticity also breaks down under certain conditions, however the correspondence between the solutions for Linear viscoelasticity and Quasi-Linear viscoelasticity is even more fragile in that it breaks down while the classical correspondence works, and hence we refer to the correspondence as a quasi-correspondence principle.     

岩石动静组合加载力学特性研究

 根据深部岩石力学研究的需要,在分析深部开挖中岩石受力特点的基础上,提出岩石动静组合加载问题。通过对多载荷凿岩机、INSTRON系统、SHPB装置的不断改进和尝试,研制出中高应变率段岩石动静组合加载试验系统,该系统可实现岩石轴向静压0～200 MPa、围压0～200 MPa和冲击动载0～500 MPa的同时加载。基于新研制的试验系统,对岩石在不同动静组合加载下的强度特性、破碎规律及吸能效率进行研究。结果表明：冲击动载一定,轴向静压从0增大到其单轴静压强度70%时,岩石的组合加载强度大于其纯静载强度或纯动载强度。轴向静压不变,随着冲击动载的增大,岩石的组合加载强度逐渐增大,表现出率相关性。动静组合加载下,岩石的破坏呈拉伸破裂模式,岩石的破碎块度在冲击动载或轴向静压增大时都向细粒端发展。岩石的吸能率随着动静组合加载的不同而不同,通过选择合适的动静组合加载,可使岩石的吸能率最大。