Global Stability Behavior Research Articles

Frame structures: global performance, static and stability behaviour: General Report

A review is made of the development of methods used to examine the response of steel frame structures to statically applied loads. The various possible alternatives in terms of rigor and complexity are defined and key effects — especially the role of connections — discussed. Both multistorey and low-rise frames are considered. A section of the paper contrasts the relative lack of attention paid to a number of “neglected features” with the plethora of publications devoted to the analysis of 2-dimensional, bare steel, rigid jointed structures.

Design of Multiple Level Retaining Walls

Retaining walls are structures that prevent retained soil from assuming its natural slope. The use of multiple level retaining walls becomes necessary when the height of the backfill soil is greater than what can be retained efficiently and economically by a single-tier retaining wall. Each tier of multiple retaining walls should be safe against sliding, overturning, and bearing capacity failure. In addition, the global slope stability behavior should also be checked. This paper presents details of the design methodology of multiple level retaining walls as used in residential construction.

Transient combustion response of homogeneous solid propellant to acoustic oscillations in a rocket motor

Interactions between acoustic waves and the transient combustion response of a double-base homogeneous propellant in a rocket motor have been analyzed numerically. The analysis extends the previous work on gas-phase flame dynamics to include the coupling with condensed-phase processes. Consequently, a more complete description of propellant combustion response to imposed acoustic oscillations can be obtained. Emphasis is placed on the near-surface flame-zone physiochemistry and its coupling with unsteady propellant burning in an oscillatory environment. The formulation treats complete conservation equations and the finite-rate chemical kinetics in both the gas-phase and subsurface regions. The instantaneous propellant burning rate is predicted as part of the solution. Various distinct features of unsteady heat release arising from propellant combustion response in a motor with forced oscillations are studied systematically. As in the pure gas-phase dynamics of the previous case, the dynamic behavior of the luminous flame plays a decisive role in determining the motor stability characteristics. However, the propellant combustion response may qualitatively modify the temporal evolution of heat-release distribution in the luminous flame and as a result exerts a significant influence on the global stability behavior. The primary flame structure adjacent to the propellant surface is usually little affected by flow oscillation. This may be attributed to the large thermal inertial of the condensed phase, which tends to restrain the temperature variation in the near-surface zone in the present study of laminar flows. The situation with a turbulent flow may be drastically different, as turbulence may penetrate directly into the, primary flame and substantially change the local flame dynamics and transport phenomena.

Disulfide Mutants of Barnase II: Changes in Structure and Local Stability Identified by Hydrogen Exchange

The hydrogen exchange behaviour of two stabilised disulfide mutants of barnase has been examined using NMR H/ 2H exchange measurements. The choice of experimental conditions is crucial in experiments to study the effects of mutations on local and global stability and dynamic behaviour of proteins. If exchange conditions allow both local and global unfolding events to be examined, then a comparison of three proteins (two mutants and wild-type) allows the effect of a mutation on the folded state to be ascribed to specific increases or decreases in local stability. This method was used to examine the effect of an introduced crosslink on the folded state of two different disulfide mutants of barnase, and the results are related to structural studies. It is found that disulfide bonds can stabilise or destabilise local structures as well as having an effect upon global stability. The effects of the mutations on exchange rate constants of protons are compared with the effects on the structure upon the introduction of the disulfide bonds. In the protein with a disulfide bond between residues 43 and 80, some local exchange rate constants are higher, reflecting local destabilisation at the site of the disulfide bond, associated with small structural rearrangements. In the protein with a disulfide bond between residues 85 and 102, amide protons of the adjacent loop are protected to a considerable extent. This is not associated with a structural rearrangement yet indicates that this disulfide bond has an effect on the stability of this loop.

Combined micro‐ and macromechanical considerations of layered composite shells

AbstractThis contribution deals with a computational treatment of the non‐linear behaviour of composite sandwich shells with extremely thin face layers and a relatively thick orthotropic core, and multi‐layered fiber reinforced polymer or metal matrix composite shells. Special emphasis is laid on algorithms which allow the consideration of local effects, like face layer wrinkling in sandwich shells and progressive damage or microplasticity in fibre composites, by semi‐analytical approaches implemented into a finite element formulation. This leads to the advantage that the shell structure must be discretized only up to an element mesh density which is sufficient for describing the global deformation and stability behaviour.

Hard self-excited vibrations occurring in a poppet valve circuit.

In this paper, the global stability and nonlinear behavior of a poppet valve circuit with a pipeline are studied by the digital simulation method. First, the local stability, or the stability of the steady state, is examined analytically, assuming that the pipeline is a lossless distributed-parameter element, and it is clarified that the instability of small valve lift is due to the effect of the pipeline. Second, it is shown that hard self-excited vibrations occur when disturbances beyond a certain critical value are imposed on the valve, and they can occur even for supply pessures lower than the setting pressure of the valve.

Theory of electrical instabilities of mixed electronic and thermal origin

Switching phenomena in amorphous semiconductors have been analyzed in a thermoelectric model. We have been able to obtain current-voltage characteristics from very general mathematical considerations concerning existence, uniqueness, local and global stability, bifurcation, and asymptotic behavior of the non-linear equations for temperature and field. Similar considerations show taht switching proceeds by the nucleation and growth of a hot spot in the interior. Detailed quantitative results are presented for simple models.