Application of HEC-HMS Model for Evaluation of Rainwater Harvesting Potential in a Semi-arid City

Water Resources Management - With many countries facing water scarcity and the demand for water ever-increasing, more people are turning to rainwater harvesting (RWH) as a feasible way of...     

Design approach of cold-formed steel portal frames

A structural arrangement of a portal frame that is easy to fabricate and assemble is developed. The rafter and column members are formed from single cold-formed channel sections, which are bolted, back-to-back at the eaves and apex joints, and connected to the foundation through angle irons. Variables in the frames include the span, width of the channel flanges and the strength of the channels. The design of the frame members follows the traditional approach of applying the effective width method to control local buckling, followed by an assessment of cross-sectional and buckling requirements. However, the yield and overall buckling requirements are modified by a factor of 0.8 to account for stress concentrations, shear lag and bearing deformations in the connections. All deflections of the frames considered are found to be within the limits provided in the literature and by the two codes of practice. It is proposed that the frames of the structure should be provided in a kit form and erected in “meccano” fashion     

Strength requirements of single cold-formed channels connected back-to-back

Tests to determine the failure modes and capacity of the eaves region of steel portal frames are presented. This was part of a major research project to establish the overall behaviour of steel portal frames, constructed from single channels and bolted back-to-back at the eaves joint. Variables in the 4 tests include the number of bolts in the connection, the points of contraflexure, the width of the channel flanges and the strength of the channels. Three modes of failure were observed, namely: local buckling of the compression zone of the flange and web of the channels, lateral torsional buckling of the channels between points of lateral support, and bolts in bearing. The final failure mode in all structures was local buckling of the compression flange and web. Local buckling was made more critical by stress concentrations, shear lag and bearing deformations caused by back-to-back bolted connections. It is proposed to apply a factor of 0.8 to the yield moment and the buckling moment of resistance to account for stress concentrations, shear lag and bearing deformations.