Analysis of steel I-beams with rectangular web openings: experimental and finite element investigation

Steel I-shaped beams with web openings of shapes like hexagonal, circular and rectangular at regular intervals have been used since last 60–70 years. Therefore aim of this paper is to examine the behaviour of steel I-beams with rectangular web openings by performinganexperimental and parametric study. A parametric study based on finite element analysis consists of effect of fillet radius, aspect ratio of rectangular openings, stiffeners position around the openings and effect of positions of openings on load carrying capacities of steel beam with rectangular web openings was carried out by using a commercial finite element software ANSYS v.12. An overall study of such type of beam was carried out and results shows that rectangular openings having fillet radius either 2 times thickness of web or 25 mm (whichever is minimum), aspect ratio of 1.6 and reinforcement either in the form of horizontal or vertical stiffeners around the web openings found to be very effective. The fillet radius and stiffeners also affect the stress distribution around the corner regions of openings. Load carrying capacities of perforated beams are almost equal to plain-webbed beams, when openings are placed within middle two-third(neutral zone) of the span

Flexural impact resistance of steel beams with rectangular web openings

This paper focuses on the flexural impact behaviour of steel I-beams with rectangular web openings. Published studies on impact resistance and design requirements of perforated steel beams are limited. To shed light such a topic, detailed non-linear three-dimensional finite element models (FEMs) were developed using ABAQUS. Rigorous validation process was employed to verify the FEMs built against published experimental tests in terms of force and displacement time histories. Reasonably good agreement was obtained between the numerical results and the corresponding experimental ones. Then, the validated FEMs were exploited to investigate the flexural impact resistance of perforated steel beams with rectangular openings. The factors examined in the current study were the area, depth, number and reinforcement of web openings under different impact velocities ranged between 2.214 to 7 m/s to provide comprehensive understanding on the flexural impact response of steel beams perforated with rectangular openings. It was observed that increasing the number of narrow web openings negligibly effected the flexural impact resistance of steel beams. Moreover, using wide openings significantly reduced the dynamic flexural resistance of such beams. Besides, slight effect on the flexural impact resistance and mid-span deflections were obtained if the depth of openings increased. Moreover, a considerable improvement was observed by providing perforated beams by horizontal steel reinforcement particularly for those with wide openings. The perforated steel beams showed similar mode of failure by generating four plastic hinges around the edges of an opening, which is the failure mode produced for perforated beams under quasi-static loading

Evaluation of gum mastic (Pistacia lentiscus) as a microencapsulating and matrix forming material for sustained drug release

In this study, a natural gum mastic was evaluated as a microencapsulating and matrix-forming material for sustained drug release. Mastic was characterized for its physicochemical properties. Microparticles were prepared by oil-in-oil solvent evaporation method. Matrix tablets were prepared by wet and melt granulation techniques. Diclofenac sodium (DFS) and diltiazem hydrochloride (DLTZ) were used as model drugs. Mastic produced discrete and spherical microspheres with DLTZ and microcapsules with DFS. Particle size and drug loading of microparticles was in the range of 22–62 µm and 50–87%, respectively. Increase in mastic: drug ratio increased microparticle size, improved drug loading and decreased the drug release rate. Microparticles with gum: drug ratio of 2:1 could sustain DLTZ release up to 12 h and released 57% DFS in 12 h. Mastic produced tablets with acceptable pharmacotechnical properties. A 30% w/w of mastic in tablet could sustain DLTZ release for 5 h from wet granulation, and DFS release for 8 h and 11 h from wet and melt granulation, respectively. Results revealed that a natural gum mastic can be used successfully to formulate matrix tablets and microparticles for sustained drug release