Intermediate Columns Research Articles

Shape optimization of cold-formed steel columns

The objective of this paper is to demonstrate the application of formal optimization tools towards maximizing the compressive strength of an open cold-formed steel cross section. In addition, in the work presented here the cross section shape is not limited by pre-determined elements (flanges, webs, stiffeners, etc.), as is commonly required to meet the necessity of conventional code-based procedures for design that employ simplified closed-form stability analysis. Instead, by utilizing the finite strip method for stability analysis and the Direct Strength Method for the strength calculation, the full solution space of cold-formed steel shapes may be explored. In the analysis herein, a given width of sheet steel is allowed to be bent at 20 locations along its width, thus providing the ability to form nearly any possible shape. Three optimization algorithms are explored: the gradient-based steepest descent method and two stochastic search methods, genetic algorithms and simulated annealing. Compared with a standard cold-formed steel lipped channel the final optimized capacities are found to be more than double the original design. Steepest descent solutions are shown (as expected) to be highly sensitive to the initial guess, but they provide symmetrical and conceptually clean solutions. The stochastic search methods require significantly more computational capacity, explore the solution space more fully, and generate solutions that are largely insensitive to the initial guess. For long and intermediate length cold-formed steel columns the optimization methods identify two non-conventional alternative designs that maximize capacity. The future of this work lies in further integrating the optimization methods with additional manufacturing and construction constraints; for now, the method suggests several interesting alternative cross sections that are worthy of future study.

Experiments on cold-formed steel columns with holes

The objective of this paper is to observe and quantify the relationship between elastic buckling and the tested response of cold-formed steel columns with holes. Compression tests were conducted on 24 short and intermediate length cold-formed steel columns with and without slotted web holes. For each specimen, a shell finite element eigenbuckling analysis was also conducted such that the influence of the boundary conditions and the hole on local, distortional, and global elastic buckling response could also be captured. Slotted web holes may modify the local and distortional elastic buckling half-wavelengths, and may also change the critical elastic buckling loads. Experimentally, slotted web holes are shown to have a minimal influence on the tested ultimate strength in the specimens considered, although post-peak ductility is decreased in some cases. Tangible connections are observed between elastic buckling and load–displacement response during the tests, including mode switching between local and distortional buckling. The columns are tested with friction-bearing boundary conditions where the columns ends are milled flat and parallel, and bear directly on steel platens. These boundary conditions, which greatly speed specimen preparation, are determined to be viable for evaluating the tested response of short and intermediate length columns, although the post-peak response of intermediate length specimens must be considered with care.

A Study on the Design Curves for Pultruded Composite Columns

The strengths of PFRP thin-walled columns are determined according to the modes of buckling which consist of local mode for short columns, global mode for long columns, and interaction mode between local and global modes for intermediate columns. Unlike the local and global buckling, the buckling strength of interaction mode is not theoretically predictable. Refined theoretical approaches which can account for different elastic properties of each plate component consisting of a PFRP thin-walled member are used. Based on both the analytical buckling loads and the experimentally measured buckling loads from literatures, the accuracies of Ylinen’s equation and modified AISC/LRFD column design equation for isotropic steel columns were compared. From the comparison, it was found that the modified AISC/LRFD column design equation is more suitable for the prediction of the buckling loads of PFRP thin-walled members than Ylinen’s equations.

Differential distribution and regulation of galanin receptors- 1 and -2 in the rat lumbar spinal cord

The expression of the galanin receptor-1 and -2 (Gal 1 and Gal 2) messenger ribonucleic acids (mRNAs) was studied in the lower spinal cord of rat by means of in situ hybridization, using ribonucleic acid probes (riboprobes). Naïve rats as well as rats with unilateral axotomy of the sciatic nerve or unilateral inflammation of the hindpaw were analyzed. In naïve rats, numerous Gal 1 mRNA-positive (+) neurons were detected in lamina (L) I–III. In addition, several Gal 1 mRNA + neurons were seen in deeper layers, including the ventral horns, area X, and the lateral spinal nucleus. In contrast, few and comparatively weakly labeled Gal 2 mRNA + neurons were observed, mostly in the ventral horns and in area X, with fewer in the dorsal horn and in the sympathetic and parasympathetic intermediate lateral cell columns. Axotomy induced a strong increase in intensity and number of Gal 2 mRNA + motoneurons ipsilateral to the lesion. In contrast, nerve cut or hindpaw inflammation did not alter the expression of Gal 1 or Gal 2 in the dorsal horn. The present (and previous) results suggest that galanin, acting through Gal 1 and Gal 2 receptors, has a modulatory role on spinal excitability, not only via interneurons in superficial dorsal horn, but also on neurons in deep layers and area X, as well as on the sympathetic and parasympathetic outflow. Furthermore, the nerve injury-induced Gal 2 upregulation in motor neurons suggests a role for galanin in survival/regeneration mechanisms.

The Tribolium columnar genes reveal conservation and plasticity in neural precursor patterning along the embryonic dorsal–ventral axis

The Drosophila columnar genes are key regulators of neural precursor formation and patterning along the dorsal–ventral axis of the developing CNS and include ventral nerve cord defective ( vnd), intermediate nerve cord defective ( ind), muscle segment homeodomain ( msh), and Epidermal growth factor receptor ( Egfr). To investigate the evolution of neural pattern formation, we identified and determined the expression patterns of Tribolium vnd, ind, and msh, and found that they are expressed in the medial, intermediate, and lateral columns of the developing CNS, respectively, in patterns similar, but not identical, to their Drosophila orthologs. The pattern of Egfr activity suggests that the genetic regulatory mechanisms that initiate Tc-vnd expression are similar in Drosophila and Tribolium, whereas those that initiate Tc-ind have diverged. RNAi analyses of gene function show that Tc-vnd and Tc-ind promote the formation of medial and intermediate column neural precursors and that vnd-mediated repression of ind establishes the boundary between the medial and intermediate columns. These data suggest that columnar gene expression and function underlie neural pattern formation in Drosophila, Tribolium, and potentially all insects, but that subtle spatiotemporal differences in expression of these genes may produce species-specific morphological differences.

CNS midline cells contribute to maintenance of the initial dorsoventral patterning of theDrosophila ventral neuroectoderm

Dorsoventral patterning of the Drosophila ventral neuroectoderm is established by the expression of three evolutionarily conserved homeodomain genes: ventral nervous system defective (vnd), intermediate neuroblasts defective (ind), and muscle segment homeobox (msh) in the medial, intermediate, and lateral columns of the ventral neuroectoderm, respectively. It was not clear whether extrinsic factor(s) from the CNS midline cells influence the initial dorsoventral patterning by controlling the expression of the dorsoventral patterning genes. We show here that the CNS midline cells, specified by single-minded (sim), are essential for maintaining expression of the dorsoventral patterning genes. Ectopic expression of sim in the ventral neuroectoderm during the blastoderm stage repressed expression of the three homeodomain genes in the ventral neuroectoderm. This indicates that the identity of the CNS midline cells is established by a series of repressions of the three homeodomain genes in the ventral neuroectoderm. Ectopic expression of sim in the ventral neuroectoderm during initial neurogenesis induced ectopic ind expression in the medial column in addition to that in the intermediate column via EGFR signaling between the ventral neuroectoderm and midline cells. In contrast, it repressed the expression of vnd and msh in the medial and lateral columns, respectively. Our findings demonstrate that the CNS midline cells provide extrinsic positional information via EGFR signaling that maintains the initial subdivision of the ventral neuroectoderm into three dorsoventral columns during initial neurogenesis.

New approach to improving distortional strength of intermediate length thin-walled open section columns

This paper describes a method which can be adopted to improve the torsional and also distortional strength of thin-walled cold-formed steel columns used in pallet racking systems. Elastic buckling analysis on two different types of column sections of intermediate length was done first in our study, after finding the buckling strength and mode of failure, the column sections were made distortionally stronger by adding simple spacers. Spacers are simple concentric tubes which are used to connect the flanges of open thin walled column sections (Fig. 3.). More than 22 laboratory experiments were carried out with different spacer spacing to asses the strength and behavior of these two different column sections. All these columns tested were investigated using finite element analysis software ANSYS [1]. The experimental results were verified with finite element analysis results obtained by solving the sections using ANSYS [1] software. Details of the experimentation and finite element analysis are presented here.

Shape-selectivity in diisopropylnaphthalene synthesis or analytical errors?

Possible analytical errors in GC analysis of diisopropylnaphthalene (DIPN) isomeric mixtures and their influence on investigation of the shape selectivity effect, reported in the literature, are discussed. Independently of a catalyst tested, the 2,6-DIPN to 2,7-DIPN ratio was reported considerably higher in researches if non-polar GC columns were applied for DIPN analysis than in researches in which intermediate or polar columns were used.

Distal Radius Fracture Treated with Two Small Fragment Plates

Purpose: To analyze functional and radiological results and early motion after the stable fixation of fractures of the distal radius by using two small fragment plates. Materials and Methods: Thirty cases were analyzed clinically and radiographically. Internal fixation was achieved using two 2.7 mm stainless steel small fragment plates on the radial and intermediate columns angled 60 apart in all cases. For functional evaluation, Green and O'Brien scores were analyzed. For radiological evaluation, volar tilting angle, radial inclination, and ulnar variance were analyzed. Arthroscopy was performed in all cases concomitantly. Results: Functional results were excellent or good in 24 patients (80%) according to the modified system of Green and O'Brien. Radiological analysis showed that volar tilting angle, radial inclination or ulnar variance during the immediate postoperative to bony union period had no significant difference. Complications occurred in two wrists, namely reflex sympathetic dystrophy (1) and delayed union (1) needing an additional palmar plate and a bone graft. No case experienced implant failure or extensor tendinitis. Conclusion: Two 2.7 mm small fragment plates fixations provided good stability, and allowed early function. We report a series of 30 fractures treated by this method of internal fixation with satisfactory results.

Evaluation of Bacillus subtilis and coliphage MS2 as indicators of advanced water treatment efficiency

The assessment of water treatment facilities for their efficiency using alternate indicators is of paramount importance. Current methods for assessing efficiency are limited by the specific characteristics of the microorganisms, such as their different sensitivities to disinfectants. A pilot study was carried out to compare different treatment scenarios for the future upgrade of the Sergio Cuevas Water Treatment plant (the largest in the Caribbean) in San Juan, Puerto Rico. The treatment units under investigation included a coagulation-flocculation-sedimentation unit, dual-media filters, micro-filtration units, intermediate ozone injection and contact columns as well as a biological filtration unit. The plant was challenged at different stages of treatment with Bacillus subtilis spores and MS2 coliphages in an attempt to test them as possible alternate indicators of treatment plant performance. These organisms were chosen because of their resistance to disinfection and desiccation, their low analysis costs and ease of detection. The removal of spores and coliphages by each treatment unit tested was calculated by seeding a known concentration (5-7 log10) of spores and coliphages and following the removal or disinfection rates. The seeded indicators were detected using traditional culture techniques. Ballasted clarification was shown to be highly efficient at removing 99.1% (approximately 3 log10) of the spores and 85.1% (approximately 0.86 log10) of MS2. Ozone treatment inactivated 80.37% (approximately 1.4 log10) spores and 99.95% (approximately 3.07 log10) coliphages. The coliphage inactivation rate obtained confirmed data obtained by previous studies indicating that MS2 was less resistant to ozonation than B subtilis spores. The membrane technology had the best efficiency in terms of physical removal of spores achieving over 99.9% (> 3 log10) removal. Coliphage removal mechanisms remain to be determined and will be a future focus of the study. Preliminary results indicate that aerobic spores and coliphages may be useful as indicators to determine the efficiency of different drinking water treatment technologies.

Localization of heparanase in normal and pathological human placenta.

Degradation of extracellular matrix (ECM) components is critical for invasion. Heparan sulphate proteoglycans are abundant in the ECM of the placenta and the decidua, hence their degradation may disassemble the matrix and facilitate placentation and trophoblast invasion. This study investigates the expression of heparanase in normal and pathological placentation using RT-PCR, in-situ hybridization and immunohistochemistry analysis to detect heparanase in specific cells of the placenta and at the fetal-maternal interface throughout pregnancy. Heparanase was observed in villous cytotrophoblasts (CT), syncytial trophoblasts (ST) and in intermediate trophoblast cell columns in normal first trimester, molar and ectopic pregnancies. The heparanase protein was preferentially expressed in the endothelium of fetal capillaries, and to a much lesser extent in larger fetal vessels. Extravillous trophoblasts (EVT) invading the decidua and the maternal vessels were also heparanase positive. In the second and third trimesters, villous CT remained heparanase positive whereas ST showed variable heparanase expression. EVT invading the placental implantation site were also positively stained. A similar pattern was observed in samples obtained from pre-eclamptic placentae and from placenta accreta. Our results indicate consistent expression of heparanase in normal and abnormal placenta, in small fetal vessels and in a variety of trophoblast subpopulations with different invasive potentials.

Column Tests of Cold-Formed Steel Channels with Complex Stiffeners

This paper presents an experimental investigation of cold-formed steel channels with complex stiffeners subjected to pure axial compression for fixed-ended columns. The complex stiffeners of the channel sections consist of simple lips with return lips. A total of 30 column specimens were tested. The specimens were brake pressed from high strength zinc-coated structural steel sheets. Four different cross sections with different flange slenderness were tested over a range of column lengths. Detailed measurements of material properties, geometric imperfections, and local buckling loads of the specimens were conducted. Interaction of local and overall buckling was observed in the tests. Failure modes include local buckling, distortional buckling, and flexural-torsional buckling. The test strengths of the columns are compared with the design strengths predicted by the American Specification and the Australian/New Zealand Standard for cold-formed steel structures. Design column curves are also plotted. It is shown that the design strengths predicted by the American Specification are generally unconservative for short and intermediate columns, whereas the design strengths predicted by the Australian/New Zealand Standard are generally conservative for all column lengths. This is because the Australian/New Zealand Standard has a separate check for distortional buckling of singly symmetric sections.

The Sox-domain containing geneDichaete/fish-hookacts in concert withvndandindto regulate cell fate in theDrosophilaneuroectoderm

In the Drosophila embryonic central nervous system, neural stem cells, called neuroblasts, acquire fates in a position-specific manner. Recent work has identified a set of genes that functions along the dorsoventral axis to enable neuroblasts that develop in different dorsoventral domains to acquire distinct fates. These genes include the evolutionarily conserved transcription factors ventral nerve cord defective and intermediate neuroblasts defective, as well as the Drosophila EGF receptor. We show that the Sox-domain-containing gene Dichaete/fish-hook also plays a crucial role to pattern the neuroectoderm along the DV axis. Dichaete is expressed in the medial and intermediate columns of the neuroectoderm, and mutant analysis indicates that Dichaete regulates cell fate and neuroblast formation in these domains. Molecular epistasis tests, double mutant analysis and dosage-sensitive interactions demonstrate that during these processes, Dichaete functions in parallel with ventral nerve cord defective and intermediate neuroblasts defective, and downstream of EGF receptor signaling to mediate its effect on development. These results identify Dichaete as an important regulator of dorsoventral pattern in the neuroectoderm, and indicate that Dichaete acts in concert with ventral nerve cord defective and intermediate neuroblasts defective to regulate pattern and cell fate in the neuroectoderm.

Review of resistance factor for steel: resistance distributions and resistance factor calibration

Changes in the Canadian steel industry warrant a review of the steel resistance factor in CSA Standard S16 (formerly S16.1) "Limit states design of steel structures", originally calibrated in the landmark study by Kennedy and Gad Aly in 1980. This paper presents statistical parameters for the bending, compression, and tension resistances of W, WWF, and HSS components produced since 1999 that have been derived from geometric and material properties presented in a companion paper. The resistance factor for steel was recalibrated for the live and dead load combination in the 1995 National Building Code of Canada. A resistance factor of 0.95 is suitable for laterally supported beams, stocky columns, and tension members failing by yield of the gross section, whereas the current value of 0.90 is appropriate for intermediate columns and tension members failing by fracture of the net section.Key words: code calibration, member resistance, reliability, resistance factor, safety, structural steel.

Development of an analytical method for the simultaneous determination of 15 carcinogenic polycyclic aromatic hydrocarbons and polycyclic aromatic nitrogen heterocyclic compounds. application to diesel particulates.

A new method enabling the determination of 15 priority carcinogenic polyaromatic compounds (PAC) proposed by the US National Toxicology Program (NTP) has been developed and applied to diesel exhaust particulates (DEP). The clean-up procedure consists of solid-phase extraction (SPE) and HPLC fractionation on silica phases followed by liquid-liquid extraction and chromatography on a polyvinylbenzene copolymer column. The method gives good recoveries for all PAC studied except dibenzo[a,j]acridine and dibenzo[a,h]pyrene, for which recovery values are below 80%. The use of GC-MS ion trap and its capacity to achieve single-ion storage enhanced the sensitivity of the method, enabling the detection of high-molecular-weight PAH in the low ng g(-1) concentration range. Intermediate polarity GC columns, e.g. BPX-50 or equivalent, enabled better separation, when applied to DEP analysis, than the generally used DB-5 apolar phase. This is observed mainly for separation of isomeric compounds belonging to the benzofluoranthene and dibenzopyrene families. The application of this method to DEP sampled from the exhaust of a diesel engine and in confined locations such as a tunnel has shown that all PAH of the NTP list could be detected, except dibenzo[a,h]pyrene. No dibenzacridine or dibenzocarbazole could be detected in such matrices. The method is sufficiently sensitive to be applicable to environmental exposure measurements in occupational health surveys.

Restoration of Cold Storage Factory Building

This paper deals with the renovation of a factory building in Nellore, India. The plan dimensions of this building are 25.7 × 52.5 m. It has concrete columns and the roof is made up of Pratt trusses with hot-rolled steel sections. Because the building is used as a cold storage facility, it is covered with a 130-mm-thick slab, which consists of the following four layers: (1) Roladeck trapezoidal sheeting; (2) one layer of 50-mm-thick concrete; (3) a layer of 40-mm-thick polyurethane foam; and (4) another layer of 40-mm-thick reinforced cement concrete (RCC). A significant amount of deflection was noticed when the scaffolding for the concrete was removed. The reason for this deflection was that most of the members of the trusses were overstressed due to the error of assuming that the truss would support traditional asbestos concrete sheet roofing. The rehabilitation measures included welding of additional steel plates to the members of the trusses. Proper precautions were not taken during welding repairs, which resulted in local buckling of the main members of the trusses. This buckling was mainly due to implementing the welding of the extra plates without providing temporary supports for the trusses, which were already carrying heavy loads. Finally it was decided to introduce intermediate columns that will reduce the force in some truss members. These remedial measures are discussed.

Convergence of Dorsal, Dpp, and Egfr Signaling Pathways Subdivides the Drosophila Neuroectoderm into Three Dorsal-Ventral Columns

An important question in neurobiology is how different cell fates are established along the dorsoventral (DV) axis of the central nervous system (CNS). Here we investigate the origins of DV patterning within the Drosophila CNS. The earliest sign of neural DV patterning is the expression of three homeobox genes in the neuroectoderm—ventral nervous system defective (vnd), intermediate neuroblasts defective (ind), and muscle segment homeobox (msh)—which are expressed in ventral, intermediate, and dorsal columns of neuroectoderm, respectively. Previous studies have shown that the Dorsal, Decapentaplegic (Dpp), and EGF receptor (Egfr) signaling pathways regulate embryonic DV patterning, as well as aspects of CNS patterning. Here we describe the earliest expression of each DV column gene (vnd, ind, and msh), the regulatory relationships between all three DV column genes, and the role of the Dorsal, Dpp, and Egfr signaling pathways in defining vnd, ind, and msh expression domains. We confirm that the vnd domain is established by Dorsal and maintained by Egfr, but unlike a previous report we show that vnd is not regulated by Dpp signaling. We show that ind expression requires both Dorsal and Egfr signaling for activation and positioning of its dorsal border, and that abnormally high Dpp can repress ind expression. Finally, we show that the msh domain is defined by repression: it occurs only where Dpp, Vnd, and Ind activity is low. We conclude that the initial diversification of cell fates along the DV axis of the CNS is coordinately established by Dorsal, Dpp, and Egfr signaling pathways. Understanding the mechanisms involved in patterning vnd, ind, and msh expression is important, because DV columnar homeobox gene expression in the neuroectoderm is an early, essential, and evolutionarily conserved step in generating neuronal diversity along the DV axis of the CNS.

Experimental verification of buckling-mode interaction in intermediate-length composite columns

Column buckling is a major design concern for pultruded composite columns. Interaction between the local (flange) and global (Euler) buckling modes occurs in intermediate length thin-walled columns with near coincident buckling loads. The interaction of more than one buckling mode induce an unstable tertiary post-buckling path, causing imperfection sensitivity and premature failure. In this work, the existence of buckling-mode interaction is experimentally verified for intermediate length pultruded wide-flange columns subjected to uniaxial compression. Characterization of the interaction mode is done using both conventional testing techniques and the shadow moiré optical technique, allowing for non-contact, full field measurement of the buckling modes.

Fractures of the distal radius treated by internal fixation and early function

Stable fixation of fractures of the distal radius can be achieved by using two 2.0 mm titanium plates placed on the radial and intermediate columns angled 50 degrees to 70 degrees apart. We describe our results with this method in a prospective series of 74 fractures (58 severely comminuted) in 73 consecutive patients. Early postoperative mobilisation was possible in all except four wrists. All of the 73 patients, except two with other injuries, returned to work and daily activities with no limitations. The anatomical results were excellent or good in 72 patients and fair in one. Our discussion includes details of important technical considerations based on an analysis of the specific complications which were seen early in the series.

Fractures of the distal radius treated by internal fixation and early function

Stable fixation of fractures of the distal radius can be achieved by using two 2.0 mm titanium plates placed on the radial and intermediate columns angled 50° to 70° apart. We describe our results with this method in a prospective series of 74 fractures (58 severely comminuted) in 73 consecutive patients. Early postoperative mobilisation was possible in all except four wrists. All of the 73 patients, except two with other injuries, returned to work and daily activities with no limitations. The anatomical results were excellent or good in 72 patients and fair in one. Our discussion includes details of important technical considerations based on an analysis of the specific complications which were seen early in the series.