Correction to: On inner constraints in plane circular arches

Archive of Applied Mechanics - The series expansions in Eq. (16) of [1] for trigonometric functions depending on a small evolution parameter shall be corrected.     

On inner shearing constraints for a direct beam model coarsely describing warping

We investigate inner shearing constraints for a direct one-dimensional beam model coarsely describing warping. In particular, we study how they affect the field equations for the elastic buckling of open thin-walled beams. We show that the distinction between the axes of the shear centres and of the centroids is crucial for the kinematics of the beam, and to derive expression of reactive actions, hence of buckling critical conditions. We also show how a suitable definition of the warping inertial action and properly introduced inner shearing constraints yield the field equations of the literature for the beam in a general dynamic setting.     

Effect of local stiffeners and warping constraints on the buckling of symmetric open thin-walled beams with high warping stiffness

Meccanica - Local stiffeners affect the behaviour of thin-walled beams (TWBs). An in-house code based on a one-dimensional model proved effective in several instances of compressive buckling of...     

Synthesis of fused dihydro-pyrimido[4,3-d]coumarins using Biginelli multicomponent reaction as key step

A new efficient approach for the synthesis of functionalized dihydro-pyrimido[4,3-d]coumarins is described. Use of benzyl- or tert-butyl acetoacetate and various salicyl aldehydes in typical Biginelli multicomponent reactions provides esters that can be easily deprotected to yield the corresponding hydroxy acids. Annelation of the latter leads to the target dihydro-pyrimido[4,3-d]coumarins. Formation of some unexpected oxo-bridged tetrahydro-pyrimidines is also described. Spectral properties of the synthesized dihydro-pyrimido[4,3-d]coumarins indicate the necessity to revisit some compounds previously reported as products of direct one-pot Biginelli condensation involving 4-hydroxycoumarin as dicarbonyl component.     

A study of molybdenum catalysts in the polymerization of 2,5-didodecyl-1,4-dipropynylbenzene

The reaction of 2,5-didodecyl-1,4-dipropynylbenzene with different molybdenum sources (Mo(CO)₆, norbornadiene-Mo(CO)₄, cyclooctadiene-Mo(CO)₄, cycloheptatriene-Mo(CO)₃, (PhCCPh)₃Mo(CO), (acac)₂MoO₂/AlEt₃) was investigated in the presence of 4-chlorophenol or 2-fluorophenol. Upon heating to 105-130 °C, the formation of didodecyl-PPE resulted. The degree of polymerization of the PPE is dependent on the used phenol and to the utilized molybdenum precursor. The most active catalyst forms from (acac)₂MoO₂, AlEt₃ and 2-fluorophenol. This catalyst combination gives high molecular weight PPEs after 6 h at 105 °C.     

Generalized Poynting Effects in Predeformed Prismatic Bars

We use the Signorini expansion method to determine second-order Saint-Venant solution for an infinitesimally bent and stretched bar. The bar in the unstressed reference configuration is straight, prismatic, isotropic, homogeneous and made of a second-order elastic material. These solutions and those found earlier for a pretwisted bar give generalized Poynting effects. A bar when bent stretches and the elongation is determined by the first and second-order elasticities, area of cross-section, torsional rigidity, bending vector and the inertia tensor. When an infinitesimally twisted bar is deformed, there is a second-order bending deformation even when there is no resultant bending moment applied on the end faces. This revised version was published online in August 2006 with corrections to the Cover Date.     

A review of the problem of the shear centre(s)

The problem of defining and determinating the shear centre is present in the literature since the first decades of this century. It soon interlaced with the definition of the twist centre and their ways became unextricable in the following decades. A number of researchers dealt with this subject meeting with variable issues, yet in the authors' opinion it seems of some interest to run through it again. In this paper a general survey of the literature is performed and the two definitions of the shear centre (here named kinematic and energetic) are compared. It is remarked how the energetic definition for the shear centre makes it coincide with a suitably chosen twist centre. An example is given to show that the two definitions generally fail to provide the same place even for simple cross sections. It is shown that the two definitions provide the same place, using standard approximate formul?, in the case of thin-walled mono-connected sections with regularly varying thickness and two-connected sections with constant thickness. As a new result, it will be shown that the two definitions of shear centre do not provide the same place for thin-walled sections with connection higher than two even in the trivial case of uniform thickness; an example is given. Received November 25, 1997     

On the Flexure of a Saint-Venant Cylinder

The flexure of a Saint-Venant cylinder is defined from a kinematic point of view. A complete solution for the field equations is provided and the gauge choices to define the center of shear and rotation are made consequently. This seems to eliminate some ambiguities present in the literature. This revised version was published online in August 2006 with corrections to the Cover Date.