A nonlinear macroelement formulation for the seismic analysis of masonry buildings

A macroelement is presented for the nonlinear dynamic analysis of masonry structures under seismic actions. The macroelement, developed in the framework of the equivalent frame model, has a force-based formulation and accounts for flexural and shear failure mechanisms, by means of two flexural hinges at the ends and a shear link, respectively. The flexural hinges are formulated according to the Bouc-Wen model to describe the progressive development of cracks and the hysteresis loops under load reversals. The shear link, in addition to the aforementioned effects, accounts for the strength/stiffness decay and is formulated adopting the Bouc-Wen-Baber-Noori model. Numerical comparisons with experimental tests on masonry piers are presented, showing the suitability of the presented macroelement

Flexural vibrations of the prestressed toroidal shell

Numerical analysis of flexural vibrations of prestressed toroidal shel

Nonlinear flexural vibrations of thin-walled circular cylinders

Nonlinear flexural vibration analysis using Galerkin method in thin-walled circular cylinder

Preparation and characterisation of polyethylene-octene grafted maleic anhydride-toughened 70:30 PA6/PP/MMT nanocomposites

A series of nanocomposites consisting of a polyamide 6 (PA6) and polypropylene (PP) matrix (70:30) with a maleated polyethylene-octene elastomer (POEgMAH) and organophilic modified montmorillonite (MMT) were prepared by melt compounding in a co-rotating twin-screw extruder followed by injection moulding. The weight fraction of organoclay was adjusted from 2 - 10 wt% by increments of 2 wt% and the weight fraction of POEgMAH was fixed at 10 wt%. POEgMAH was used as an impact modifier as well as compatibiliser in the nanocomposites. Mechanical properties of the blends were investigated by tensile, flexural and impact testing. X-ray diffraction (XRD) was used to characterise the nanocomposites. The thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Addition of 4 wt% organoclay showed the highest tensile and flexural strengths for the blends. The Young's and flexural moduli were also improved with increasing the organoclay concentration but with a corresponding reduction in impact strength and elongation at break. XRD result revealed that the organoclay was dispersed uniformly (exfoliated) although the degree of exfoliation decreased with increasing organoclay content. The DSC analysis showed that the crystallinity of the blends decreased with increasing organoclay concentration. It was shown from the TGA analysis that the thermal stability of the PA6/PP nanocomposites was significantly improved in the presence of impermeable silicate layers in the blends

Flame retardancy and mechanical properties of poegmah compatibilized rice husk filled polypropylene composites

Flammability of Polypropylene, PP has restricted its usage as a versatile synthetic polymer. The addition of flame retardants will lower the flammability of PP. However, it will lower the mechanical properties. In this study, the flame retardancy of PP composite has been enhanced by the addition of intumescent flame retardant. Four formulations have been prepared, without flame retardant and with increasing concentration of flame retardant which are 20phr, 25phr and 30phr. The flammability of the composites has been measured using the Limiting Oxygen Index based on ASTM D2863. Two types of mechanical testing have been done to determine the mechanical properties, which are flexural test (ASTM D790) and impact test (ASTM D256). The thermal analysis has been done by thermogravimetry analysis (TGA) to determine the thermal stability of the composites prepared. Morphological study by scanning electron microscopy (SEM) has been done to study the filler distribution. Results obtained from the flammability test indicate that the addition of flame retardant has strongly improved the flame retardancy. The flexural strength and impact strength decreases as the concentration of flame retardant increases while the flexural modulus increases. The thermal analysis has proven that the composites with flame retardant have better thermal stability as compared to the composite without flame retardant. The morphological study has shown that the addition of flame retardant did not affect the filler distribution. The filler remain well distributed as the flame retardant introduced to the composites

Flexural–torsional behavior of thin-walled composite box beams using shear-deformable beam theory

This paper presents a flexural–torsional analysis of thin-walled composite box beams. A general analytical model applicable to thin-walled composite box beams subjected to vertical and torsional loads is developed. This model is based on the shear-deformable beam theory, and accounts for the flexural–torsional response of the thin-walled composites for an arbitrary laminate stacking sequence configuration, i.e. unsymmetric as well as symmetric. The governing equations are derived from the principle of the stationary value of total potential energy. Numerical results are obtained for thin-walled composites under vertical loading, addressing the effects of fiber angle and span-to-height ratio of the composite beam