Shear Strength of Hollow Flange Channel Beams with Stiffened Web Openings

This LiteSteel beam (LSB) is a new cold-formed steel hollow flange channel section produced using a patented manufacturing process involving simultaneous cold-forming and dual electric resistance welding. The LSBs are commonly used as floor joists and bearers with web openings in buildings. Their shear strengths are considerably reduced when web openings are included for the purpose of locating building services. Shear tests of LSBs with web openings have shown that there is up to 60% reduction in the shear capacity. Hence there is a need to improve the shear capacity of LSBs with web openings. A cost effective way to eliminate the shear capacity reduction is to stiffen the web openings using suitable stiffeners. Hence numerical studies were undertaken to investigate the shear capacity of LSBs with stiffened web openings. In this research, finite element models of LSBs with stiffened web openings in shear were developed to simulate the shear behaviour and strength of LSBs. Various stiffening methods using plate and LSB stiffeners attached to LSBs using both welding and screw-fastening were attempted. The developed models were then validated by comparing their results with experimental results and used in further studies. Both finite element and experimental results showed that the stiffening arrangements recommended by past research for cold-formed steel channel beams are not adequate to restore the shear strengths of LSBs with web openings. Therefore new stiffener arrangements were proposed for LSBs with web openings. This paper presents the details of this research project using numerical studies and the results

Finite Element Analyses of Lipped Chanel Beams with Web Openings in Shear

Cold-formed steel members are increasingly used as primary structural elements in buildings due to the availability of thin and high strength steels and advanced cold-forming technologies. Cold-formed lipped channel beams (LCB) are commonly used as flexural members such as floor joists and bearers. Shear behaviour of LCBs with web openings is more complicated and their shear capacities are considerably reduced by the presence of web openings. However, limited research has been undertaken on the shear behaviour and strength of LCBs with web openings. Hence a numerical study was undertaken to investigate the shear behaviour and strength of LCBs with web openings. Finite element models of simply supported LCBs with aspect ratios of 1.0 and 1.5 were considered under a mid-span load. They were then validated by comparing their results with test results and used in a detailed parametric study. Experimental and numerical results showed that the current design rules in cold-formed steel structures design codes are very conservative for the shear design of LCBs with web openings. Improved design equations were therefore proposed for the shear strength of LCBs with web openings. This paper presents the details of this numerical study of LCBs with web openings, and the results

The Total Open Monophonic Number of a Graph

For a connected graph G of order n >- 2, a subset S of vertices of G is a monophonic set of G if each vertex v in G lies on a x-y monophonic path for some elements x and y in S. The minimum cardinality of a monophonic set of G is defined as the monophonic number of G, denoted by m(G).  A  monophonic set of cardinality m(G) is called a m-set of G. A set S of vertices  of a connected graph G is an open monophonic set of G if for each vertex v  in G, either v is an extreme vertex of G and v ˆˆ? S, or v is an internal vertex of a x-y monophonic path for some x, y ˆˆ? S. An open monophonic set of minimum cardinality is a minimum open monophonic set and this cardinality is the open monophonic number, om(G). A connected open monophonic set of G is an open monophonic set S such that the subgraph < S > induced by S is connected. The minimum cardinality of a connected open monophonic set of G is the connected open monophonic number of G and is denoted by omc(G). A total open monophonic set of a graph G is an open monophonic set S such that the subgraph < S > induced by S contains no isolated vertices. The minimum cardinality of a total open monophonic set of G is the total open monophonic number of G and is denoted by omt(G). A total open monophonic set of cardinality omt(G) is called a omt-set of G. The total open monophonic  numbers of certain standard graphs are determined. Graphs with total open monphonic number 2 are characterized. It is proved that if G is a connected graph such that omt(G) = 3 (or omc(G) = 3), then G = K3 or G contains exactly two extreme vertices. It is proved that for any integer n  3, there exists a connected graph G of order n such that om(G) = 2, omt(G) = omc(G) = 3. It is proved that for positive integers r, d and k  4 with 2r, there exists a connected graph of radius r, diameter d and total open monophonic number k. It is proved that for positive integers a, b, n with 4 <_ a<_ b <_n, there exists  a connected graph G of order n such that omt(G) = a and omc(G) = b

Effect of silicate solubilizing bacteria and fly ash on silicon uptake and yield of rice under lowland ecosystem

A field experiment was conducted in sandy loam soils of eastern farm, Agricultural Engineering College and Research Institute, Kumulur, Tamil Nadu, India to study the effect of silicon on yield and uptake of rice (var. BPT 5204) during Kharif season of 2010-11 by taking the treatment combinations based on graded levels of Fly Ash (FA), Silicate Solubilizing Bacteria (SSB) and Farm Yard Manure (FYM) at fixed fertilizer schedule. The experimental soil (0-15 cm) had pH 7.22; organic C 1.4 %; available Si 66.0 mg kg-1; available N 266.0 kgha-1; available P 14.42 kgha-1 and available K 107.50 kgha-1. The results of graded levels of FA show that all the growth and yield attributes were significantly influenced by silicon uptake. The mean silicon uptake at panicle initiation, straw and grain at harvest varied from 53.8 - 98.7, 105.5 - 197.2 and 21.4- 62.3 kgha-1 respectively, in rice. Number of filled grains per panicle and grain yield displayed conspicuous relationships with content of Si in grains. The highest mean grain yield of 3622 kg ha-1 was recorded by the addition of SSB+FYM followed by FYM (3530 kg ha-1), SSB (3310 kg ha-1) and control (3240 kg ha-1). The combined application of 25 t ha-1 FA with SSB+FYM was recorded the highest grain yield of 3710 kg ha-1 which was 16.3 per cent moreover yield of control. The results further show that 25 t ha-1 FA and SSB+FYM have been proved to be superior treatments for best management of silicon in coastal loamy sand soils under irrigated rice ecosystem

Numerical Studies of Rivet-Fastened Rectangular Hollow Flange Channel Beams

The rivet-fastened rectangular hollow flange channel beam (RHFCB) is a new cold-formed hollow section proposed as an alternative to welded hollow flange beams. It is a monosymmetric channel section made by rivet-fastening two torsionally rigid rectangular hollow flanges to a web plate. This method will allow the designers to develop optimum sections, with affordable rivet connection between their web and flange elements. In addition to this unique geometry, the rivet-fastened RHFCBs also have unique characteristics relating to their stress-strain characteristics, residual stresses, initial geometric imperfections and hollow flanges that are not encountered in conventional hot-rolled and cold-formed steel channel sections. Therefore detailed experimental and numerical studies were conducted to study the section moment capacities of rivet-fastened RHFCBs. This paper presents the details of the numerical study of rivet-fastened RHFCBs and the results. Finite element models of rivet-fastened RHFCBs were developed by including all the significant effects that influence their ultimate section moment capacities, including material inelasticity, and geometric imperfections. The results from finite element analyses were then compared with corresponding experimental results and the predictions from the current design rules. Test results showed that the developed finite element models were able to predict the behaviour and section moment capacities of RHFCBs. The validated model was then used in a detailed parametric study that produced additional section moment capacity data of the rivet-fastened RHFCBs

New Web Crippling Design Rules for Cold-Formed Steel Beams

Lipped channel beams (LCBs) and SupaCee sections are commonly used as floor joists and bearers in the construction industry. SupaCee section is one of the cold-formed steel members, which is increasingly used in the building construction sector. It is characterized by unique ribbed web and curved lip elements, and is claimed to be more economical with extra strength than the traditional channel sections. These thin-walled LCBs and SupaCee sections are subjected to specific local and global failures, one of them being web crippling. Several experimental and numerical studies have been conducted in the past to study the web crippling behaviour and capacities of different cold-formed steel sections under different concentrated load cases. However, due to the nature of the web crippling phenomenon and many factors influencing the web crippling capacities, capacity predictions given by most of the cold-formed steel design standards are either unconservative or conservative. Hence both experimental and finite element studies were conducted to assess the web crippling behaviour and strengths of LCBs and SupaCee sections under ETF, ITF, EOF and IOF load cases. New equations were proposed to determine the web crippling capacities of LCBs and SupaCee sections based on the results from experiments and finite element analyses. Suitable DSM based web crippling design equations were also developed

Behaviour of LiteSteel Beams Subject to Combined Shear and Bending Actions

This paper presents the details of a numerical study of a cold-formed steel beam known as LiteSteel Beam (LSB) subject to combined shear and bending actions. The LSB sections are produced by a patented manufacturing process involving simultaneous cold-forming and electric resistance welding. They have a unique shape of a channel beam with two rectangular hollow flanges. To date, however, no investigation has been conducted into the strength of LSB sections under combined shear and bending actions. Hence a numerical study was undertaken to investigate the behaviour and strength of LSBs subject to combined shear and bending actions. In this research, finite element models of LSBs were developed to simulate the combined shear and bending behaviour and strength of LSBs. They were then validated by comparing their results with test results and used in a parametric study. Both experimental and finite element analysis results showed that the current design equations are not suitable for combined shear and bending capacities of LSBs. Hence improved design equations are proposed for the capacities of LSBs subject to combined shear and bending actions

Design of Rivet Fastened Rectangular Hollow Flange Channel Beams Subject to Local Buckling

The innovative, rivet fastened Rectangular Hollow Flange Channel Beam (RHFCB) is a new type of cold-formed steel section, proposed as an extension to the widely researched hollow flange beams. The hollow flange beams have garnered much interest in the past due to the sections having capacities more typically associated with hot-rolled steel sections. Various researches have been carried out to investigate the behavior of continuously welded hollow flange beams but little is known on the behavior of RHFCBs. The structural behaviour of the RHFCB is unique compared to other conventional cold-formed steel sections and its moment capacity reduces with rivet spacing. The current cold-formed steel design standards do not provide a calculation method to include the effects of intermittent fastening. In this research an extensive parametric study was conducted using validated finite element models to investigate the section moment capacity of RHFCBs. This paper presents the findings from the parametric study and proposes new design equations for the section moment capacity of RHFCBs in the Direct Strength Method format. The parametric study considers various slenderness regions, section dimensions and rivet spacing. In the new design equations, a reduction factor parameter is included to calculate the section moment capacity of RHFCBs at any rivet spacing up to 200 mm

Section Moment Capacity Tests of Rivet-Fastened Rectangular Hollow Flange Channel Beams

The rivet-fastened rectangular hollow flange channel beam (RHFCB) is a new cold-formed hollow section proposed as an alternative to welded hollow flange steel beams. It is a mono-symmetric channel section made by rivet fastening two torsionally rigid rectangular hollow flanges to a web plate. This method will allow the designers to develop optimum sections, with affordable rivet connection between the web and flange elements. The new rivet-fastened RHFCB has unique characteristics that are not encountered in conventional hot-rolled and cold-formed steel channel sections. Therefore an experimental study consisting of 15 section moment capacity tests was conducted with different rivet spacings to investigate the flexural behaviour and strength of rivet-fastened RHFCB members. The ultimate moment capacities from the tests were compared with the capacities predicted by the current design rules for steel structures, and their suitability to predict the section moment capacities of RHFCBs was investigated. The applicability of the Direct Strength Method based design rules was also investigated. This paper presents the details of this experimental study and the results

Improvement in Millet Soaking by Way of Bubbled Cold Plasma Processed Air Exposure; Phytic Acid Reduction Cum Nutrient Analysis Concern

Pearl millet is one of the high-grown and underutilized grain crops. It is confined to traditional foods due to its anti-nutritional and functional properties. The present study investigated the influence of plasma processed air bubbling and soaking on phytic acid content, total and HCl extractable iron, physicochemical, techno-functional, and pasting properties of pearl millet. Exposure of pearl millet to plasma processed air bubbling at 180 V with an airflow rate of 10 liters /h for 1 h and 2 h reduced phytic acid content by 60.66 % and 39.27 % respectively. Whereas soaking for 12 h reduced phytic acid by 21.6 % in contrast with the untreated sample. The total iron content reduced from 39.9 to 29.8 mg/100g and HCl extractable iron content increased from 12 % to 69.49 % with the given treatments. Obtained data were noticed with significant changes (p < 0.05) and are in line with its exposure to the selected variable treatments. This work points to the potentiality of plasma processed air pre-treatment in the food industry to improve nutrition and mineral availability accompanied by modifying pasting, techno-functional properties of pearl millet