Lift-and-project ranks of the stable set polytope of joined a-perfect graphs

In this paper we study lift-and-project polyhedral operators defined by Lov?asz and Schrijver and Balas, Ceria and Cornu?ejols on the clique relaxation of the stable set polytope of web graphs. We compute the disjunctive rank of all webs and consequently of antiweb graphs. We also obtain the disjunctive rank of the antiweb constraints for which the complexity of the separation problem is still unknown. Finally, we use our results to provide bounds of the disjunctive rank of larger classes of graphs as joined a-perfect graphs, where near-bipartite graphs belong

Recent Research and Developments in Cold-formed Steel Design and Construction

Unstiffened Elements - Some Interesting Features - Tests of Profiled Steel Decks with V-Stiffeners - Bending Strength of Beams with Non-Linear Analysis - Local and Distortional Buckling of Thin-Walled Beams - Design of C-Sections Against Deformational Lip Buckling - Lateral Buckling of Singly Symmetric Beams - Flexural Capacity of Discretely Braced C\u27s and Z\u27s - The Buckling Behaviour of Hollow Flange Beams - Experimental Investigations of I-Beams - Tests of Continuous Purlins Under Downwards Loading - Tests of Full-Scale Roofing Systems - Profiled Sheet Behaviour Under Concentrated Load - On Design of Profiled Sheets with Varying Cross Sections - Properties for Cellular Decks in Negative Bending - Contrasting Behaviour of Thin Steel Roof Claddings Under Simulated Cyclonic Wind Loading - New ASCE Standards for Cold-Formed Steel Deck Slabs - Composite Slabs Analyzed by Block Bending Test - Repeated Point Loading Tests on Composite Slabs - Thermal Shielding Near Intermediate Supports of Continuous Span Composite Slabs - Design of Channels Against Distortional Buckling - Distortional Buckling of Cold-Formed Steel Z-Section Columns - Shah Alam Sports Complex: Design and Construction of Unistrut Space-Frame Roof Structure - Flexibly Connected Thin-Walled Space Frame Stability - Test of a Full Scale Roof Truss - Down-Aisle Stability of Rack Structures - Racking Performance of Plasterboard-Clad Steel Stud Walls - An Experimental Study of Shear Wall Units - Some Applications of Generalized Beam Theory - Calibration of a Bending Model for Cold-Formed Sections - Recent Development in Cold-Formed Steel - The 1989 Edition ofthe Canadian Cold-Formed Steel Design Standard - Observations and Comments Pertaining to CAN/CSA-S136-M89 - Prediction of Corner Mechanical Properties for Stainless Steels Due to Cold Forming - Stainless Steel Tubular Beams - Tests and Design - The Lateral Torsional Buckling Strength of Cold-Formed Stainless Steel Lipped Channel Beams - Testing and Design of Bolted Connections in Cold-Formed Steel Sections - Behavior of Arc Spot Weld Connections in Tension - The Bi-Axial Behaviour of Shear Connectors in Composite Slabs and Beams - Influence of Deformed Metal Decking Composite Floors to Beam-Column Connections - Education in Cold-Formed Steel Structures - Lifelong Learning - Activities of the Center for Cold-Formed Steel Structure

Development of an approach and tool to improve the conceptual design process of the wing box structure of low-subsonic transport aircraft

To produce a better airframe design, it is imperative to investigate the problems of design and manufacturing integration early on at the conceptual design stage. A new design approach and support tool is required which will aid the designer in future product development. This is a particular necessity in the current context of increasing complexity and challenging economic situations. The present work focuses on the development of a design approach and design aids for designing metallic wingbox structures of low-subsonic transport aircraft with small wing sweepback angles. Its aims are two-fold: to assist in producing alternative structural concepts, and to capture the effects of new materials and manufacturing processes on weight and cost. It will form the basis for selecting the structural concept at the early stage of the design process. The target users of this design approach and tools are relatively inexperienced structural designers and students. The developed process and tools are quite general in their application as they use stand-alone modules which can be employed separately or jointly with existing techniques and tools used by industry, research centres and academia. A comparison of the result from the developed analytical tools against a detailed study undertaken by an aircraft company on the original configuration was made. It showed stress analysis and sizing results that were within a 10% margin. A case study was performed to investigate the reduction of Direct Operating Cost (DOC) of a turboprop transport aircraft by redesigning the wingbox structure. Weight reductions of wing box structure of 16% were achieved using new configurations and advanced metallic materials. The purchase price of the aircraft could also be reduced through use of cheaper labour and new manufacturing processes. These cost savings, if converted into DOC reductions, are only 0.36% of DOC due to fuel saving and 0.25% of DOC due to manufacturing cost reduction for the wingbox structure only. It is obvious that the overall DOC reduction is the result of the total impact of relative DOC effects due to fuel cost saving, material prices, labour rates, and manufacturing process improvements. Within the range of the calculated parameter values, the overall DOC reductions could be as much as 0.61% relative DOC. It appears that fuel prices, material cost and labour rates give greater impacts on DOC than high speed machining processes. Due to the use of advanced aluminium, maintenance cost is also predicted to be less. It has better fatigue life and fracture toughness than the standard aluminium and therefore will increase the aircraft maintenance periods for inspection and repair due to slower crack damage growth. This cost saving will contribute in reducing the life cycle cost of the aircraft. In addition, the number of crack stoppers could be reduced, therefore minimising weight and manufacturing cost. These benefits however have not been analysed

Buckling curves of hot rolled H steel sections submitted to fire

Report of the research work at the base of the design equation introduced in Eurocode 3 (EN 1993-1-2) for the stability of steel columns under axial loading or combined axial and bending loading