Design of Partially or Fully Composite Beams, with Ribbed Metal Deck, Using LRFD Specifications
A Hindu saying states, "One picture is worth a thousand words (numbers)." With this optic in mind, the design aspects of steel-concrete composite beams using the recently adopted LRFD specifications 1 are analyzed critically and the significance of several parameters is brought out clearly. Charts are then constructed to facilitate the design of partially or fully composite beams using rolled-steel, wideflange sections of A36 steel or A572 Gr. 50 steel. The slab may be a composite metal deck slab with ribs perpendicular to the beam, a haunched slab or, simply, a flat soffit concrete slab. The charts cover both adequate and inadequate slabs. The charts provided are a valuable tool from the practical standpoint, and also familiarity with them should contribute to the student's and young engineer's overall feel of the composite beam design problem. The design charts given here complement the composite beam design tables provided in the LRFD manual.
Structural fire resistance of partially restrained, partially composite floor beams, I: Experiments
Abstract This paper is Part 1 of a two-part investigation of the structural fire resistance of a partially composite, one-way spanning steel floor beam assembly with partial translational and rotational end restraint provided by shear tab connections to a supporting frame. The goal of this study is to provide experimental data and validated numerical models that can aid the implementation of performance-based design and evaluation approaches for structural fire resistance of steel-framed composite floor systems that are typical of North American building practice. This paper describes a pair of experimental tests on structurally identical composite floor specimens that are subjected to fire via a large modular furnace. A subsequent companion paper (Part 2) presents the numerical studies. One specimen was designed to conform to a 2-h fire rating as prescribed by UL Design No. D902 – the other was tested with no passive fire protection (i.e. as bare steel). Both specimens were flexurally loaded and tested to structural failure under exposure to the ASTM E119 standard fire, and the experimental results are evaluated using the ASTM E119 thermal and structural failure criteria. The test results show similar correlations of midspan deflection to beam temperature for both specimens. The shear tab connections experienced permanent deformation but maintained adequate structural integrity to allow the specimens to reach flexural failure. Neither shear slip nor localized cracking could be visibly detected at the composite stud locations during post-test inspection, indicating that composite action was maintained up to flexural failure.
Growth and Characterization of β-RDX Single-Crystal Particles
1,3,5-Trinitrohexahydro-s-triazine (RDX) single-crystal particles crystallized in the β phase have been successfully grown by sublimation–recrystallization. Synchrotron X-ray diffraction results confirm that the recrystallized products are β-RDX single crystals. Compared to the traditional solution deposition methods, the sublimation method used in this work breaks through the mass limitations during the growth of β-RDX. The distribution of α- and β-RDX on different substrates reveals that hydrophilic substrates are prone to grow β-RDX single crystals and that hydrophobic substrates prefer α-RDX single crystals. The sublimation rate dominates the growth of pure β-RDX. The mechanisms of the phase transition from β-RDX to α-RDX during the process of sublimation–recrystallization have been studied. The current results can promote the potential application of β-RDX in the propellant, explosives, and military fields.