摘要:

The effects of land use on the chemical composition of urban stormwater runoff and its subsequent acute toxicity to the aquatic invertebrateDaphnia pulexhave been investigated in the Brunette drainage basin of Burnaby, British Columbia. Both land use and interval between rainfall events influenced the chemical composition and toxicity of the stormwater. The industrial and commercial land use sites were the major source of those trace metals most often considered toxic to aquatic invertebrates, with runoff from the commercial sites proving most frequently toxic to the test organism. Toxicity followed the sequence commercial > industrial > residential > open space. A detailed study of a single storm event indicated that while the “first-flush” of the storm contributed to toxicity—through the physical scouring of insoluble pollutants—some soluble pollutants, which were washed out of the watershed later in the storm event, also proved to be toxic. This finding has implications for the collection and treatment of stormwater runoff. Laboratory bioassays with synthetic stormwater composed of the trace metals Cu, Fe, Pb, and Zn at concentrations observed in field samples demonstrated that pH and suspended solids helped to regulate the toxicity of trace metals, and implicated the importance of these factors in natural stormwater toxicity.Key words: stormwater, street surface sediments, land use, buildup time, trace metals, toxicity,Daphniabioassays, pH, suspended solids effects.

ISSN:0315-1468    

DOI:10.1139/l88-011

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

This paper describes the interactive buckling behaviour of thin-walled columns by means of a simple engineering analysis. After a brief review of individual column and plate buckling phenomena, the effect of one upon the other is investigated in the presence of initial imperfections. Estimates of the ultimate load capacity of such columns and the effects of material yielding are obtained. The results are compared with published experimental data, yielding good correspondence. The work clearly demonstrates that the interactive presence of Euler buckling, plate buckling, imperfections, and material yielding in thin-walled columns has a serious detrimental effect on their ultimate strength.Key words: buckling, stability, interaction, imperfections, yield, plates, columns, thin-walled, cold-formed, steel, experiments.

ISSN:0315-1468    

DOI:10.1139/l88-012

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The rotational behaviour of clipped end plate connections was studied by subjecting nine clipped and three conventional or “unclipped” specimens with varying connection geometry to combined shear and moment and obtaining the corresponding moment–rotation characteristics. It was found that the clipped end plate connections in this investigation had more than adequate rotation capacity to permit an interior beam connected to a supporting member by this type of connection to achieve its full plastic moment, provided the length-to-depth ratio of the beam does not exceed 20. For the range of rotations that would be experienced by clipped end plate connections in a practical structure, a model originally developed to predict the moment–rotation behaviour of conventional shear end plate connections was modified so as to be applicable to clipped end plate connections. Good agreement was obtained between the test values and those predicted by the modified model. No adverse effect on the rotational behaviour of the connections was observed to result from the asymmetry caused by clipping the end plate.Key words: beams, bolts, columns, connections, fillet welds, limit states design, moment, rotation, shear tests, steel construction.

ISSN:0315-1468    

DOI:10.1139/l88-013

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The purpose of this study is to examine the effect of rigid diaphragms in reducing warping and distortion stresses developed in box girders due to deformation of the cross section. Tests were conducted for two Plexiglas box girder models to determine effect of diaphragms on the behaviour of box girder sections. The results of the tests were compared with values obtained from the so-called “beam on elastic foundation (BEF) analogy,” an analytical procedure that permits the calculation of warping and distortion stresses in box sections due to deformation of the cross section.Each box girder model was tested as a simply supported beam with a 1168.4 mm (46 in.) span. Six separate loading positions were used for each of the three predesigned diaphragm spacings. Thus, 18 separate loading tests were conducted for each model in order to obtain sufficient data to determine the amount of reduction in both warping and distortion stresses. Test measurements included the applied load, deflections, and strains at various locations on the webs and bottom flanges.The results indicate that deformation of a box girder cross section due to eccentric loading may cause substantial warping and distortion stresses, and that these stresses can be effectively controlled by judicious installation of rigid diaphragms along the span of the girder. Also, experimental warping and distortion stresses obtained from both tests compare reasonably well with those predicted by the BEF analogy.Key words: warping, torsional, stresses, deformations, box girder bridges, diaphragms.

ISSN:0315-1468    

DOI:10.1139/l88-014

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l88-015

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l88-016

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l88-018

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0315-1468    

DOI:10.1139/l88-019

出版商:NRC Research Press    

年代:1988

数据来源: NRC