Optimization of the design of the cooling duct of thin!walled heat-stressed structures

The results of modeling of the stressed state of a thinwalled profiled ribbed shell of the cooling duct of heatstressed structures with additional hollow bridges made on the shell ribs with an increased surface for soldering are presented. It is shown that the implementation of the bridges makes it possible to reduce the stresses arising in the inner shell, or to increase the pressure of the cooler in the duct. Keywords: cooling duct, rib, milled inner shell, outer jacket [email protected]

Melanopsidae (Caenogastropoda: Cerithioidea) from the eastern Mediterranean: another case of morphostatic speciation

Melanopsidae were collected from 23 localities in central and south-eastern Europe, the Aegean Islands and Israel. This study considered Melanopsis from the Aegean Islands, the Peloponnese and Israel, and Esperiana esperi, Holandriana holandrii and Microcolpia from continental Europe. Shells and radulae were described and illustrated, showing continuous variation of shell characters and differences in radulae among genera. Phylogenetic analyses were conducted on single-locus datasets (COI, 18S, 28S, ITS2 and H3) and on a concatenated dataset. Molecular data showed a differentiation not paralleled in morphology, reflecting morphostatic evolution. In all species with ribbed shell-forms, the ribbed and unribbed forms did not differ genetically. Within Melanopsis, four clades representing five species were distinguished. Melanopsis buccinoidea is found in Khios and Lesbos Islands, M. astropaliae in Naxos, Samos and Tinos Islands, M. wagneri in Rhodes Island and the Peloponnese, and M. costata and M. saulcyi in Israel. Molecular results and the ICZN rule of priority restrict the range of M. buccinoidea to the North Aegean Islands. ‘Melanopsis’ parreyssi belongs to the genus Microcolpia. Esperiana esperi belongs to a clade separate from Microcolpia.

Quasi-static stability of a ribbed shell interacting with moving load

Loss of stability of thin-walled structural elements of aircraft is the most common type of destruction. In this work, the definition of the critical velocity of a pressure wave moving over the surface of an acclivous, ribbed cylindrical shell, which is the most common design element of all aviation and rocket systems, is considered. The article takes into account the discreteness of the location of stiffeners (stringers), in contrast to other works, where ribbing is taken into account only within the framework of a constructive orthotropic model. In the quasi-static formulation, the problem of the stability of a shallow shell with a discrete arrangement of stringers under the action of a moving radial load has been solved. The range of critical speeds of movement of the load is defined. An example is considered.

Dynamic Stability Analysis of Steel-Concrete Composite Ribbed Shell under Vertical Step Loads

The steel-concrete composite ribbed shell is a kind of novel space structure. In this paper, using space beam element and shell element, based on the nonlinear FE theory, considering the elastic-plastic material and geometric nonlinear, in view of the system dynamic response of identifying method, dynamic stability of steel-concrete composite ribbed shell under vertical step loads are studied. Setting up the relationship, it is between load amplitude and dynamic response of the structures, comparing rigid joint with hinge joint on the edge of structure, Critical load conditions of dynamic stability are defined.

Dynamic Stability Analysis of Steel Concrete Composite of Ribbed Shell under Stepped Loads

A systemically study on the new space structure steel - concrete composite ribbed shell is made, which is loaded by stepped load. The ultimate bearing capacity and failure modes are investigated based on the characteristic response indicators. In the foundation of large number of parameters analysis, the influence of the span ratio, span, boundary conditions and initial imperfection on the ultimate bearing capacity and instable dynamic failure are discussed in details. All the results will provide mass of data to the investigation of failure mechanism and the property under complex dynamical loads.

Dynamic Stability Analysis of Steel-Concrete Composite Ribbed Shell

Steel-concrete composite ribbed shell is a kind of shell structure based on the thin concrete shell, which has the advantages of two different materials, at the same time with steel nets shell and thin concrete shell structure. In this paper, the seismic performance of steel concrete composite ribbed shell is analyzed, in which the elastoplastic time-history analysis method is used to analyze internal force and deformation. Furthermore a parameter analysis is made to discuss the seismic performance, which considering different high-span ratio, section dimension, boundary conditions and structure division frequency. The influence on structure seismic performance and some structure dynamic response characteristics are obtained, which can be resulted for structural seismic design and referenced in steel-concrete thin shell design specification modification.