Flexural rigidity

About: Flexural rigidity is a research topic. Over the lifetime, 3829 publications have been published within this topic receiving 56780 citations.

The continuum of connection rigidity in timber structures

Abstract: The use of timber in rigid frames has been hampered by the debate surrounding the rigidity of the moment connections. Joint stiffness is a function of beam flexural stiffness, as well as of the rotational stiffness of the connection. The level of joint rigidity, which is predictable from joint stiffness, significantly affects the bending moments and forces that are transferred through the connection. We used joint-test data from the literature and computer models to assess the effect of various parameters on joint stiffness. There is a continuum of joint stiffness for moment-resisting connections where the deformed shapes of the beams in beam-to-column connections are described by pinned, semi-rigid, and rigid behavior. Engineers can assess the level of joint rigidity during the design process so that the resulting connections and frames meet performance expectations. It seems unlikely that a fully rigid joint can be designed for use in timber portal frames because of stiffness orthotropy. However, moment-resisting joints that are less than 50% rigid can be used in timber frames to develop frame-like behavior.

FABRIC MECHANICAL AND PHYSICAL PROPERTIES RELEVANT TO CLOTHING MANUFACTURE —: Part 2: Structural Balance, Breaking Elongation and Curvature of Seams

Abstract: In Part 1 of this series of papers, we investigated the importance of fabric overfeed in the sewing operations during tailoring. It was also shown how fabric bending rigidity, formability, shear and hygral expansion are important in clothing manufacture. The present paper is concerned with the measurement and experimental study of seam balance, breaking elongation and bending properties of seams. The aim is to evaluate quantitatively the consumption of sewing thread and the relationship between the degree of fabric overfeed during sewing and the curvature of the seam in the garment. Balanced seams have much higher breaking elongation and more symmetrical bending properties than unbalanced seam structures. A natural curvature and curling couple result from fabric overfeed during sewing. The value of the curvature is time‐dependent because of fabric viscoelastic effect and also depends on the level of fabric overfeed, the tensile and longitudinal compressive module of the component fabrics and the structure of the seamed composite. The natural curvature of the seam may be derived quantitatively from the relative lengths of overfeed fabrics using a modified theory for a bimetallic themostatic strip.

Experimental Tests on the Composite Foam Sandwich Pipes Subjected to Axial Load

Abstract: Compared to the composite thin-walled tube, the composite foam sandwich pipe has better local flexural rigidity, which can take full advantage of the high strength of composite materials. In this paper, a series of composite foam sandwich pipes with different parameters were designed and manufactured using the prefabricated polyurethane foam core-skin co-curing molding technique with E-glass fabric prepreg. The corresponding axial-load compressive tests were conducted to investigate the influence factors that experimentally determine the axial compressive performances of the tubes. In the tests, the detailed failure process and the corresponding load–displacement characteristics were obtained; the influence rules of the foam core density, surface layer thickness, fiber ply combination and end restraint on the failure modes and ultimate bearing capacity were studied. Results indicated that: (1) the fiber ply combination, surface layer thickness and end restraint have a great influence on the ultimate load bearing capacity; (2) a reasonable fiber ply combination and reliable interfacial adhesion not only optimize the strength but also transform the failure mode from brittle failure to ductile failure, which is vital to the fully utilization of the composite strength of these composite foam sandwich pipes.

Studies on the key parameters in segmental lining design

Abstract: The uniform ring model and the shell-spring model for segmental lining design are reviewed in this article. The former is the most promising means to reflect the real behavior of segmental lining, while the latter is the most popular means in practice due to its simplicity. To understand the relationship and the difference between these two models, both of them are applied to the engineering practice of Fuzhou Metro Line I, where the key parameters used in both models are described and compared. The effective ratio of bending rigidity η reflecting the relative stiffness between segmental lining and surrounding ground and the transfer ratio of bending moment ξ reflecting the relative stiffness between segment and joint, which are two key parameters used in the uniform ring model, are especially emphasized. The reasonable values for these two key parameters are calibrated by comparing the bending moments calculated from both two models. Through case studies, it is concluded that the effective ratio of bending rigidity η increases significantly with good soil properties, increases slightly with increasing overburden, and decreases slightly with increasing water head. Meanwhile, the transfer ratio of bending moment ξ seems to only relate to the properties of segmental lining itself and has a minor relation with the ground conditions. These results could facilitate the design practice for Fuzhou Metro Line I, and could also provide some references to other projects with respect to similar scenarios.