Fire performance of cold-formed steel sections

Thin-walled cold-formed steel (CFS) has exhibited inherent structural and architectural advantages over other constructional materials, for example, high strength-to-weight ratio, ease of fabrication, economy in transportation and the flexibility of sectional profiles, which make CFS ideal for modern residential and industrial buildings. They have been increasingly used as purlins as the intermediate members in a roof system, or load-bearing components in low- and mid-rise buildings. However, using CFS members in building structures has been facing challenges due to the lack of knowledge to the fire performance of CFS at elevated temperatures and the lack of fire design guidelines. Among all available design specifications of CFS, EN1993-1-2 is the only one which provided design guidelines for CFS at elevated temperatures, which, however, is based on the same theory and material properties of hot-rolled steel. Since the material properties of CFS are found to be considerably different from those of hot-rolled steel, the applicability of hot-rolled steel design guidelines into CFS needs to be verified. Besides, the effect of non-uniform temperature distribution on the failure of CFS members is not properly addressed in literature and has not been specified in the existing design guidelines. Therefore, a better understanding of fire performance of CFS members is of great significance to further explore the potential application of CFS. Since CFS members are always with thin thickness (normally from 0.9 to 8 mm), open cross-section, and great flexural rigidity about one axis at the expense of low flexural rigidity about a perpendicular axis, the members are usually susceptible to various buckling modes which often govern the ultimate failure of CFS members. When CFS members are exposed to a fire, not only the reduced mechanical properties will influence the buckling capacity of CFS members, but also the thermal strains which can lead additional stresses in loaded members. The buckling behaviour of the member can be analysed based on uniformly reduced material properties when the member is unprotected or uniformly protected surrounded by a fire that the temperature distribution within the member is uniform. However if the temperature distribution in a member is not uniform, which usually happens in walls and/or roof panels when CFS members are protected by plaster boards and exposed to fire on one side, the analysis of the member becomes very complicated since the mechanical properties such as Young’s modulus and yield strength and thermal strains vary within the member. This project has the aim of providing better understanding of the buckling performance of CFS channel members under non-uniform temperatures. The primary objective is to investigate the fire performance of plasterboard protected CFS members exposed to fire on one side, in the aspects of pre-buckling stress distribution, elastic buckling behaviour and nonlinear failure models. Heat transfer analyses of one-side protected CFS members have been conducted firstly to investigate the temperature distributions within the cross-section, which have been applied to the analytical study for the prediction of flexural buckling loads of CFS columns at elevated temperatures. A simplified numerical method based on the second order elastic – plastic analysis has also been proposed for the calculation of the flexural buckling load of CFS columns under non-uniform temperature distributions. The effects of temperature distributions and stress-strain relationships on the flexure buckling of CFS columns are discussed. Afterwards a modified finite strip method combined with the classical Fourier series solutions have been presented to investigate the elastic buckling behaviour of CFS members at elevated temperatures, in which the effects of temperatures on both strain and mechanical properties have been considered. The variations of the elastic buckling loads/moments, buckling modes and slenderness of CFS columns/beams with increasing temperatures have been examined. The finite element method is also used to carry out the failure analysis of one-side protected beams at elevated temperatures. The effects of geometric imperfection, stress-strain relationships and temperature distributions on the ultimate moment capacities of CFS beams under uniform and non-uniform temperature distributions are examined. At the end the direct strength method based design methods have been discussed and corresponding recommendations for the designing of CFS beams at elevated temperatures are presented. This thesis has contributed to improve the knowledge of the buckling and failure behaviour of CFS members at elevated temperatures, and the essential data provided in the numerical studies has laid the foundation for further design-oriented studies.School of Marine Science and Engineering, Plymouth University; China Scholarship Counci

Offensive Advertisements Influence You More Than Me: An Examination of the Third-Person Effects in the Chinese Cultural Context

This study examined the third-person effect (TPE) hypothesis (Davison, 1983) in offensive advertising in the Chinese cultural context. Based on a survey of 1,539 Chinese Internet users about the third- and firstperson effects among offensive ads, neutral ads, and public service ads, the study inquires into the relationship between the TPE and respondents’ levels of acceptance toward advertising. Besides confirming the TPE existence in an Eastern cultural context, the results suggest that the TPE predict wordof-mouth (WOM) spreading for both offensive and neutral product ads, but not for PSAs. Theoretical contributions and managerial implications of these findings are discussed

Delineating Structural Characteristics of Viral Capsid Proteins Critical for Their Functional Assembly.

Viral capsids exhibit elaborate and symmetrical architectures of defined sizes and remarkable mechanical properties not seen with cellular macromolecular complexes. The limited coding capacity of viral genome necessitates economization upon one or a few identical gene products known as capsid proteins for shell assembly. The functional uniqueness of this class of proteins prompts questions on structural features critically important for their higher order organization. In this thesis, I develop the statistical framework and computational tools to pinpoint the structural characteristics of viral capsid proteins exclusive to the virosphere by testing a series of hypotheses, providing understanding of the physical principles governing molecular self-association that can inform rational design of nanomaterials and therapeutics. In the first chapter, I compare the folds of capsid proteins with those of generic proteins, and establish that capsid proteins are segregated in structural fold space, highlighting the geometric constraints of these building blocks for tiling into a closed shell. Second, I develop a software program, PCalign, for quantifying the physicochemical similarity between protein-protein interfaces. This tool overcomes the major limitation of current methods by using a reduced representation of structural information, greatly expanding the structural interface space that can be investigated through inclusion of large macromolecular assemblies that are often not amenable to high resolution experimental techniques. As an application of this method, I propose a computational framework for template-based protein inhibitor design, leading to the prediction of putative binders for a therapeutic target, the influenza hemagglutinin. In silico evaluations of these candidate drugs parallel those of known protein binders, offering great promise in expanding therapeutic options in the clinic. Lastly, I examine protein-protein interfaces using PCalign, and find strong statistical evidence for the disconnectivity between capsid proteins and cellular proteins in structural interface space. I thus conclude that the basic shape and the sticky edges of these Lego pieces act concertedly to create the sophisticated shell architecture. In summary, the novel tools contributed by this dissertation work lead to delineation of structural features of viral capsid proteins that make them functionally unique, providing an understanding that will serve as the basis for prediction and design.PHDBioinformaticsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/110375/1/sscheng_1.pd

PCalign: a method to quantify physicochemical similarity of protein-protein interfaces

Abstract Background Structural comparison of protein-protein interfaces provides valuable insights into the functional relationship between proteins, which may not solely arise from shared evolutionary origin. A few methods that exist for such comparative studies have focused on structural models determined at atomic resolution, and may miss out interesting patterns present in large macromolecular complexes that are typically solved by low-resolution techniques. Results We developed a coarse-grained method, PCalign, to quantitatively evaluate physicochemical similarities between a given pair of protein-protein interfaces. This method uses an order-independent algorithm, geometric hashing, to superimpose the backbone atoms of a given pair of interfaces, and provides a normalized scoring function, PC-score, to account for the extent of overlap in terms of both geometric and chemical characteristics. We demonstrate that PCalign outperforms existing methods, and additionally facilitates comparative studies across models of different resolutions, which are not accommodated by existing methods. Furthermore, we illustrate potential application of our method to recognize interesting biological relationships masked by apparent lack of structural similarity. Conclusions PCalign is a useful method in recognizing shared chemical and spatial patterns among protein-protein interfaces. It outperforms existing methods for high-quality data, and additionally facilitates comparison across structural models with different levels of details with proven robustness against noise.http://deepblue.lib.umich.edu/bitstream/2027.42/110905/1/12859_2015_Article_471.pd

Mechanical Behavior of Fiber-to-concrete Interface in Textile Reinforced Concrete: Theoretical Model

This paper presents a theoretical solution of a reinforcement-to-concrete interface model under pull-push loading. Expressions for the interfacial shear stress distribution and load-displacement history are derived for different loading stages. The full debonding propagation process is discussed in detail and the analytical solutions are verified by comparing with existing theoretical models. Results of the analytical solution are presented to illustrate how the bond length and local bond-slip law affect the interfacial bond behavior. While the case study in this paper is on textile reinforced concrete, the analytical solution is equally valid to similar mechanical cases such as rebar reinforced concretes

PCalign: a method to quantify physicochemical similarity of protein-protein interfaces

Abstract Background Structural comparison of protein-protein interfaces provides valuable insights into the functional relationship between proteins, which may not solely arise from shared evolutionary origin. A few methods that exist for such comparative studies have focused on structural models determined at atomic resolution, and may miss out interesting patterns present in large macromolecular complexes that are typically solved by low-resolution techniques. Results We developed a coarse-grained method, PCalign, to quantitatively evaluate physicochemical similarities between a given pair of protein-protein interfaces. This method uses an order-independent algorithm, geometric hashing, to superimpose the backbone atoms of a given pair of interfaces, and provides a normalized scoring function, PC-score, to account for the extent of overlap in terms of both geometric and chemical characteristics. We demonstrate that PCalign outperforms existing methods, and additionally facilitates comparative studies across models of different resolutions, which are not accommodated by existing methods. Furthermore, we illustrate potential application of our method to recognize interesting biological relationships masked by apparent lack of structural similarity. Conclusions PCalign is a useful method in recognizing shared chemical and spatial patterns among protein-protein interfaces. It outperforms existing methods for high-quality data, and additionally facilitates comparison across structural models with different levels of details with proven robustness against noise.http://deepblue.lib.umich.edu/bitstream/2027.42/134734/1/12859_2015_Article_471.pd