Improved Effective Width Method Considering Distortional Buckling for Cold-Formed Thin-Walled Steel Members with Lipped Channel Section

The local buckling, distortional buckling, and overall buckling would occur for cold-formed thin-walled steel members with lipped channel section. The effective width method is used to considering the effect of local and distortional buckling on load-carrying capacity of member in Chinese code. Especially, a very conservative stability coefficient of partially stiffened elements used to considering the local buckling and distortional buckling of flange of lipped channel sections. In this paper, the half-wave length, the elastic buckling stress of distortional-buckling of cold-formed thin-walled steel members with lipped channel section and the corresponding stability coefficient of partially stiffened elements were developed based on the energy method. With comparison among the calculated results of elastic buckling stress and half-wave length using the improved method and the Finite Strip Method, suitability and precision of the improved method were illuminated. Then, a uniform formula for the stability coefficient of partially stiffened elements considering both local and distortional buckling effect was established based on the proposed method. Finally, with comparison on lipped channel sections in the appendix of Chinese code and existing test results conducted by many researchers and the proposed method, it is shown that the proposed uniform formula had higher precision to calculate the stability coefficient of partially stiffened elements and the ultimate load-carrying capacity of cold-formed thin-walled steel members with lipped channel section

Shear Behavior of Screw Connections for Cold-formed Thin-walled Steel Structures

Self-drilling screws are the primary mean s to fasten cold-formed thin-walled steel members in construction. There are several failure modes for shear connections with self-drilling screws, including screw tilting, hole bearing, edge tearing, tensile fracture in net s ection of connected elements and shear fracture of screws. Meanwhile, the “g roup effect” will exist when a large number of screws are used in a shear connection. A series of tests (75 specimens) on single lap shear connections with self-drilling screws has been carried out and the results report ed in this paper. The end distance, screw spacing, pattern of screws arra ngement and number of screws was varied to determine their influence on shear connection strength. The study focused on the analysis of factors af fecting the shear connection strength, the shear strength estimation of self-drilling screw connections based on different failure modes and the influence of group effect. Finally, a proposed design method and recommendations for Chinese specification GB50018 are presented

Load-carrying Capacity Estimation on Cold-formed Thin-walled Steel Columns with Built-up Box Section

The use of cold-formed thin-walled steel structural members has increased in recent years, and most of their sections are open section with only one symmetrical axis, which would likely fail by twisting and interaction with the others buckling mode, such as local buckling and distortional buckling. To improve the ultimate strength of columns, built-up box section can be used. In this paper, a series of loading capacity tests on high-strength cold- formed steel columns with built-up bo x section are presented, including 21 axially-compressed columns and 19 eccentrically-compressed columns sub- jected to bending moments about weak axis as well as strong axis. The test specimens are built up by two channel sections with two intermediate stiffeners in the web, and they connect at their flanges using self-drilling screws. It was shown that distortional buckling and twisting do not occur and the ultimate load-carrying capacity is 10 to 20 percent higher than the sum of the ultimate load-carrying capacity of each lipped channel section columns. According to the test results and theoretical analysis, an improved method based on the suggestion of current China code ‘Technical code of cold-formed thin-walled steel struct ures’ (GB50018-2002) considering the plate-coupling effect was proposed to estimate the ultimate load-carrying capacity of built-up box section column. With the proposed method, the calculated results are close and conservative to the test results

Estimating Population Exposure to Fine Particulate Matter in the Conterminous U.S. Using Shape Function-Based Spatiotemporal Interpolation Method: A County Level Analysis

This paper investigates spatiotemporal interpolation methods for the application of air pollution assessment. The air pollutant of interest in this paper is fine particulate matter PM2.5. The choice of the time scale is investigated when applying the shape function-based method. It is found that the measurement scale of the time dimension has an impact on the quality of interpolation results. Based upon the result of 10-fold cross validation, the most effective time scale out of four experimental ones was selected for the PM2.5 interpolation. The paper also estimates the population exposure to the ambient air pollution of PM2.5 at the county-level in the contiguous U.S. in 2009. The interpolated county-level PM2.5 has been linked to 2009 population data and the population with a risky PM2.5 exposure has been estimated. The risky PM2.5 exposure means the PM2.5 concentration exceeding the National Ambient Air Quality Standards. The geographic distribution of the counties with a risky PM2.5 exposure is visualized. This work is essential to understanding the associations between ambient air pollution exposure and population health outcomes

Estimating Population Exposure to Fine Particulate Matter in the Conterminous U.S. using Shape Function-based Spatiotemporal Interpolation Method

This paper investigates spatiotemporal interpolation methods for the application of air pollution assessment. The air pollutant of interest in this paper is fine particulate matter PM2.5. The choice of the time scale is investigated when applying the shape function-based method. It is found that the measurement scale of the time dimension has an impact on the quality of interpolation results. Based upon the result of 10-fold cross validation, the most effective time scale out of four experimental ones was selected for the PM2.5 interpolation. The paper also estimates the population exposure to the ambient air pollution of PM2.5 at the county-level in the contiguous U.S. in 2009. The interpolated county-level PM2.5 has been linked to 2009 population data and the population with a risky PM2.5 exposure has been estimated. The risky PM2.5 exposure means the PM2.5 concentration exceeding the National Ambient Air Quality Standards. The geographic distribution of the counties with a risky PM2.5 exposure is visualized. This work is essential to understanding the associations between ambient air pollution exposure and population health outcomes

trans-Bis(5,5-diphenyl­hydantoinato-κN 3)bis­(propane-1,2-diamine-κ2 N,N′)nickel(II)

The asymmetric unit of the title complex, [Ni(pht)2(pn)2] (pht is 5,5-diphenyl­hydantoinate and pn is propane-1,2-diamine) or [Ni(C15H11N2O2)2(C3H10N2)2], contains one-half [Ni(pht)2(pn)2] mol­ecule. The NiII atom is situated on a crystallographic center of inversion and shows a distorted octa­hedral coordination geometry. A three-dimensional network structure is assembled by inter- and intra­molecular N—H⋯O=C inter­actions

Distortion Buckling Test and Design Method of Cold-Formed Thin-Wall Steel Built-Up Members Under Axial Compression

The objective of this paper is to research the distortion buckling performance and capacity of cold-formed thin-walled steel built-up I-shaped section column. 12 built-up columns connected by self-drilling screws were conducted under the axial compression. The test members includes four different sections and the specimen length is 1000mm. Test results show that the local buckling and distortion buckling occur for all built-up sections. The finite element software ABAQUS was used to analysis the test specimens. The finite element results were in good agreement with the experimental results about the buckling mode and load-carrying capacities. The direct strength method is used to calculate the load-carrying capacities of the specimens. The calculation results show that the direct strength method is unsafe, so the direct strength method to calculate distortional buckling strength is modified on the basis of the test results. 1The author gratefully acknowledgements the financial support provided by National Natural Science Foundation Projects of China(No:51868049), Department of Education Science and Technology Projects of Jiangxi Province in China (No:GJJ180932, GJJ170983),Natural Science Foundation Projects of Jiangxi Province in China (No:20181BAB206040),Nanchang Institute of Technology 2019 Postgraduate Innovation Program (No:YJSCX20190012) and Academic and Technical Leaders in Major Subject Areas projects of Jiangxi Province in China(No: 0172BCB22022)