Structural Design Study on a Light - Gauge Steel Portal Frame with Cold-formed Sigma Sections

Design study is conducted on a thin-gauge cold-formed steel portal frame with compound double (back-to-back) sigma sections in columns and rafters. Experimental study on the sem-irigid rafter-to-column connection behaviour is first carried out for two special bolted connection types based upon specific thin connection plates between the double sections. First connection plate studied was a compact corner plate bolted between double sigma sections of rafter and column end parts. Other connection plate type studied was composed of four together layered thin plates with the edges of two outer plates outwardly lipped at the free side of the corner plate. Connection behaviour in the ridge joint of the portal frame also constructed with using a connection plate between double sigma sections of rafter ends was experimentally studied in a similar way as the rafter-to-column connection behaviour. Analytical models are developed for the semi-rigid connection behaviour in the corners and in the ridge of the portal frame and these models are then used in design calculations for the whole portal frame. One design case study for a 12 m span portal frame is completed by using the newest version of Eurocode 3

Study on the Load-bearing Capacity of Cold-formed Sigma Purlins

Experimental investigations conducted on the structural behaviour and ultimate load carrying capacity of cold-formed sigma purlins are reported. Three different purlin systems, i.e. the double spanning, the sleeved and the overlap system, were investigated. In addition to the full- scale tests on 2-span purlin - sheeting system with screw fastening and with continuous, sleeved and overlapped central supports, tests on single span purlins were also conducted for finding out bending moment and shear capacity values at the central support of a multiple span sigma purlin. Analytical considerations for modelling the cross-sectional behaviour of the sigma purlin itself and the local deformation of the connection at supports are carried out mainly according to the draft of Eurocode 3 (Part 1.3). Test results are used to compare and to confirm the calculation models based both upon elastic (Eurocode 3) and plastic behaviour of the purlin. A new plastic design proposal is presented/or multiple span sigma purlins

Optimum Design of Cold-formed Steel Z-shape Purlins Using a Genetic Algorithm

In this paper, a genetic algorithm is applied to optimize the dimensions of cold-formed Z-shape purlins continuous over two spans under gravity load. The optimization criterion is to maximize the load resistance per cross-section and the design variables are chosen from the discrete values based on the manufacturing requirements. Purlins are designed in accordance with Eurocode 3, Part 1.3. In addition, the modified Eurocode 3 method, in which the elastic local buckling stress and distortional buckling stress calculated using Finite Strip Method (FSM) are integrated into the design process, is used to determine the effective section properties. The results are compared with those obtained using Eurocode 3 method

Study on Light-gauge Steel Roof Trusses with Rosette Connections

This paper describes the Rosette-joining system and its possibilities in roof-truss structures in the span range of 8 to 12 meters (26 to 39 ft). The test programme that was carried out to verify the behaviour of the Rosette-joint and the thin-walled sections is described. The test results are given and analysed where they currently exist. The results are compared with values calculated according to the 1996 U.S. (AISI) [3] code supported by a distortional buckling analysis according to the Australian / New Zealand Standard (AS) [4] and FE Analysis results

Abnormal Appearance of the Area Centralis in Labrador Retrievers With an ABCA4 Loss-of-function Mutation

Purpose: To study retinal appearance and morphology in Labrador retrievers (LRs) heterozygous and homozygous for an ABCA4 loss-of-function mutation.Methods: Ophthalmic examination, including ophthalmoscopy and simple testing of vision, was performed in five ABCA4(wt/wt), four ABCA4(wt/InsC), and six ABCA4(InsC/InsC) LRs. Retinas were also examined with confocal scanning laser ophthalmoscopy (cSLO) and optical coherence tomography (OCT). Infrared and fundus autofluorescence (FAF) images were studied, and outer nuclear layer (ONL) and neuroretinal thickness were measured in the central and peripheral area centralis.Results: Clinical signs in young ABCA4(InsC/InsC) LRs were subtle, whereas ophthalmoscopic findings and signs of visual impairment were obvious in old ABCA4InsC/InsC LRs. Retinal appearance and vision testing was unremarkable in heterozygous LRs regardless of age. The cSLO/OCT showed abnormal morphology including ONL thinning, abnormal outer retinal layer segmentation, and focal loss of retinal pigment epithelium in the fovea equivalent in juvenile ABCA4(InsC/InsC) LRs. The abnormal appearance extended into the area centralis and visual streak in middle-aged ABCA4(InsC/InsC) and then spread more peripherally. A mild phenotype was seen on cSLO/OCT and FAF in middle-aged to old ABCA4(wt/InsC) LRs.Conclusions: Abnormal appearance and morphology in the fovea equivalent are present in juvenile ABCA4InsC/InsC. In the older affected LRs, the visual streak and then the peripheral retina also develop an abnormal appearance. Vision deteriorates slowly, but some vision is retained throughout life. Older heterozygotes may show a mild retinal phenotype but no obvious visual impairment. The ABCA4InsC/InsC LR is a potential model for ABCA4-mediated retinopathies/juvenile-onset Stargardt disease in a species with human-sized eyes.Translational Relevance: The ABCA4(InsC) mutation causes juvenile-onset abnormal appearance of the fovea equivalent in affected dogs that slowly spreads in the retina, while only a mild phenotype is seen in older carriers. This is the first non-primate, large animal model for ABCA4-related/STGD1 retinopathies in a species with a fovea equivalent

Erratum to: Home-range use patterns and movements of the Siberian flying squirrel in urban forests : effects of habitat composition and connectivity

Erratum to: Home-range use patterns and movements of the Siberian flying squirrel in urban forests: effects of habitat composition and connectivity The original article was published in Movement Ecology 2016 4:5Non peer reviewe

An experimental investigation of properties of Q345 steel pipe at elevated temperatures

This paper presents the results of an extensive experimental investigation of the thermal and mechanical properties of Q345 steel pipe at elevated temperatures using both the steady-state and transient-state test methods. Under these two test conditions, the thermal expansion coefficient, yield strength and elastic modulus of the specimens at different temperatures were measured. The tested results indicate that both the yield strength and elastic modulus decrease gradually with increasing temperature. However, at the same temperature, both the yield strength and elastic modulus tested using the steady-state test are higher than those tested using the transient-state test. Hence, it is less safe to use the material properties tested using the steady-state test for fire resistance design of the steel structure. Based on the transient-state test results, the models of the mechanical properties of Q345 steel pipe at elevated temperatures were proposed. These models can be used for the design and analysis of Q345 steel pipe structures under fire conditions.2012 Specialized Research Fund for the Doctoral Programme of Higher Education of China (Grant No. 20120095110027)