Ultimate Failure Behaviour of Second-generation Sheeting Subjected to Combined Bending Moment and Concentrated Load

Second-generation sheeting is widely used for cladding and roof construction. At interior supports, it is subjected to combined bending moment and concentrated load. Unfortunately, design rules for this loading are complicated and do not provide insight in the sheeting\u27s failure behaviour. This means there is a need for a new, insight providing design rule. For first-generation sheeting, a similar problem did exist. The Technische Universiteit Eindhoven (TUE) carried out three research projects [Bakk92a,Vaes95a,Hofm00a] that provided insight in the first-generation sheeting behaviour and resulted in a new, insight providing design rule. The TUE now uses the strategy of these three research projects for a new project on second-generation sheeting [Kasp01a], with the final aim of a new design rule for second-generation sheeting. In this new project, experiments on commonly used (in the Netherlands) second-generation sheeting were carried out. Second-generation sheeting behaviour was compared with first-generation sheeting behaviour. For sheeting with only stiffeners in flange, load falls occur before ultimate load. Stiffeners in the web only result in load falls after the ultimate load. For an experiment with only stiffeners in the web, a finite element simulation was made. The simulation predicts the sheeting behaviour fairly well and indicates how a stiffener affects the sheeting behaviour

Composite Behaviour of Steel Frames with Precast Concrete Infill Panels

This paper presents preliminary experimental and numerical results of an investigation into the composite behaviour of a steel frame with a precast concrete infill panel (S-PCP) subject to a lateral load. The steel-concrete connections consist of two plates connected with two bolts which are loaded in shear only. The connections are designed for a failure mechanism consisting of ovalisation in the bolt holes due to bearing of the bolts to avoid brittle failure. Experimental pull-out and shear tests on individual frame-panel connections were performed to establish their stiffness and failure load. A full scale experiment was performed on a onestorey one-bay 3 by 3m infilled frame structure horizontally loaded at the top. With the known characteristics of the frame-panel joints from the experiments on individual connections, a numerical analysis was performed on the infilled frame structure taking nonlinear behaviour of the structural components into account. The finite element model yields reasonably accurate results and indicates a connection failure sequence similar to experimental failure

Experimental Research on the Behaviour of Combined Web Crippling and Bending of Steel Deck Sections

At an interior support, sections of cold-formed steel are subjected to a concentrated load and a bending moment Existing design rules describing the section failure at an interior support are subject to improvement and are not based on the section\u27s physical failure behaviour. In the last decade, several analytical models have been developed that predict the section ultimate concentrated load and directly include the influence of the bending moment, so that an empirical interaction method is not needed. However, the authors believe that these models are correct only for a concentrated load and a small bending moment In practice large bending moments occur. Therefore, the aim of the current research project is to develop an analytical model for trapezoidal hat sections subjected to a concentrated load and a bending moment as occurring in practice. The development of this model will be based on both experimental and numerical research will be carried out. In this article, a part of the experimental research will be presented

Experimental Research on the Behaviour of Combined Web Crippling and Bending of Steel Deck Sections

At an interior support, sections of cold-formed steel are subjected to a concentrated load and a bending moment Existing design rules describing the section failure at an interior support are subject to improvement and are not based on the section\u27s physical failure behaviour. In the last decade, several analytical models have been developed that predict the section ultimate concentrated load and directly include the influence of the bending moment, so that an empirical interaction method is not needed. However, the authors believe that these models are correct only for a concentrated load and a small bending moment In practice large bending moments occur. Therefore, the aim of the current research project is to develop an analytical model for trapezoidal hat sections subjected to a concentrated load and a bending moment as occurring in practice. The development of this model will be based on both experimental and numerical research will be carried out. In this article, a part of the experimental research will be presented

Numerical and Analytical Modelling of Hat-section Web Crippling Behaviour

Hat-sections of thin-walled steel are subject to a concentrated load and a bending moment at an interior support. For a large concentrated load and a small bending moment, two failure mechanisms can occur: the yield-arc and the rolling mechanisms. Research indicated that the corner radius has a strong influence on the failure mechanism to occur [1-2}. It has been investigated whether small strips of the hat-section cross-sections can be used to gather insight into the differences of the two failure mechanisms. For small corner radii, strip behaviour and section behaviour are comparable. For large corner radii, this is not the case. Finite element models have been used to describe the cross-sectional behaviour of hat-sections for varying corner radii. Relatively simple analytical models have been derived which determine the location of first yield in the cross-section's web and the cross-section's rigid-plastic behaviour. Except for the largest corner radius, analytical models and finite element models give comparable results

New research directions in flexural member failure at an interior support (Interaction of web crippling and bending moment)

Design rules describing failure at an interior support of cold-formed steel flexural members are of an empirical nature. This is probably due to the complex character of the failure mechanisms, which makes an analytical approach difficult. An overview of research on this subject has been made. The Bakker model is reviewed. This is the first analytical model accurately describing one of the failure mechanisms occurring for a concentrated load and a small bending moment. A new research project is introduced for extending the Bakker model for a concentrated load and a medium or large bending moment

FE Models for Sheeting under Interaction Load

Experiments show that, after ultimate load, sheeting may fail by three distinct post-failure modes. In this paper, three finite element models are presented, one for each post-failure mode. One of the finite element models was difficult to develop. A spring model explains this. The finite element models show that, at ultimate load, only two different ultimate failure modes exist. This is important for the development of mechanical models for sheeting failure

Fluctuating Nonlinear Spring Model of Mechanical Deformation of Biological Particles

We present a new theory for modeling forced indentation spectral lineshapes of biological particles, which considers non-linear Hertzian deformation due to an indenter-particle physical contact and bending deformations of curved beams modeling the particle structure. The bending of beams beyond the critical point triggers the particle dynamic transition to the collapsed state, an extreme event leading to the catastrophic force drop as observed in the force (F)-deformation (X) spectra. The theory interprets fine features of the spectra: the slope of the FX curves and the position of force-peak signal, in terms of mechanical characteristics --- the Young's moduli for Hertzian and bending deformations E_H and E_b, and the probability distribution of the maximum strength with the strength of the strongest beam F_b^* and the beams' failure rate m. The theory is applied to successfully characterize the $FX$ curves for spherical virus particles --- CCMV, TrV, and AdV

Design imperfections for steel beam lateral torsional buckling

To perform geometrically and materially nonlinear analyses including imperfec-tions for steel beam lateral torsional buckling, the size and shape of the geometric imperfec-tion can be obtained from EN 1993-1-1. The shape is prescribed as an initial bow along the weak axis of the section, excluding torsion of the cross-section. The shape of the imperfection can alternatively be taken equal to the lateral torsional buckling mode, including torsion. Sev-eral tables and formulas exist to determine the size of the imperfection. Different imperfection approaches were applied in finite element simulations to evaluate the lateral torsional nonlin-ear buckling resistances and to compare them to the results obtained with design rules

The SARS-coronavirus nsp7+nsp8 complex is a unique multimeric RNA polymerase capable of both de novo initiation and primer extension

Uniquely among RNA viruses, replication of the ∼30-kb SARS-coronavirus genome is believed to involve two RNA-dependent RNA polymerase (RdRp) activities. The first is primer-dependent and associated with the 106-kDa non-structural protein 12 (nsp12), whereas the second is catalysed by the 22-kDa nsp8. This latter enzyme is capable of de novo initiation and has been proposed to operate as a primase. Interestingly, this protein has only been crystallized together with the 10-kDa nsp7, forming a hexadecameric, dsRNA-encircling ring structure [i.e. nsp(7+8), consisting of 8 copies of both nsps]. To better understand the implications of these structural characteristics for nsp8-driven RNA synthesis, we studied the prerequisites for the formation of the nsp(7+8) complex and its polymerase activity. We found that in particular the exposure of nsp8's natural N-terminal residue was paramount for both the protein's ability to associate with nsp7 and for boosting its RdRp activity. Moreover, this ‘improved’ recombinant nsp8 was capable of extending primed RNA templates, a property that had gone unnoticed thus far. The latter activity is, however, ∼20-fold weaker than that of the primer-dependent nsp12-RdRp at equal monomer concentrations. Finally, site-directed mutagenesis of conserved D/ExD/E motifs was employed to identify residues crucial for nsp(7+8) RdRp activity