Eccentric compression

Load-Carrying Capacity at Eccentric Compression Load... 

Experimental research on the eccentrically compressed elements capacity was carried out on samples measuring 100 x 100 x 500 mm, reinforced by longitudinal rods of 08 mm and stirrups of 05 mm. 

The analysis of Formula (2.25) shows that the increase in initial eccentricity of loading drastically reduces the loading capacity of an eccentrically compressed element of RubCon on the equation of power function. It is possible to note the weak dependence of the loading capacity on the reinforcing percent. 

A design model for eccentric compressed elements from RubCon (Figure 2.18) was based on the following ... 

FIGURE 2.18 Model of stress-strain state of eccentrically compressed element. (Reprinted from Yu. Potapov, O. Figovsky, Yu. Borisov, S. Pinaev, and D. Beilin, Stress-Strain State of Compressed Elements from Polymer Concrete, J. Scientific Israel Technological Advantages 4, nos. 3-4 (2002) 20-24. With permission.)... 

Let s write down the equilibrium equations for a normal section of an eccentrically compressed RubCon short column (without buckling) at loading that approaches destruction ... 

Supposing that loss of load capacity of an eccentrically compressed element is determined by the maximal bending moment, we shall add a third equation, describing the condition of a maximum ... 

The structural members studied by the French group were trusses made of polyester reinforced by long uni directional glass fibres. These trusses are used as masts, either cantilevered or guyed. This latter situation, in which they are subjected to eccentric compression, was chosen and was simulated by compression tests in a hydraulic press. 

Three short trusses (consisting of three modules) were loaded to failure under eccentric compression applied either in a plane of symmetry, or in a perpendicular plane (Figure 3). A fourth long truss (consisting of seven modules) was loaded to failure with the same load position as one of the short trusses, to study the effect of overall buckling. 

Apparently, dispersed fibres do not appreciably modify the behaviour of cement-based elements subjected to creep. There have been few experimental studies of this problem and the results obtained are inconclusive. As mentioned above for shrinkage, modification of the internal structure of composite materials causes quite complex results and comparisons are difficult. In several reports, similar behaviour of plain and fibre-reinforced elements was observed under creep conditions, both qualitatively and quantitatively. However, extensive studies executed by Swamy et al. (1977) proved that fibre-reinforcement decreased creep considerably. Similar conclusions were formulated by Brandt and Hebda (1989) who tested elements under eccentric compression in long periods of time. The creep was small for reinforced specimens. The most important factor relating to the final creep values was the level of load with respect to the material s strength and that factor was also influenced by the volume of fibre reinforcement. That was the reason why the creep recovery measurements carried out by different authors did not furnish consistent results. 

Brandt, A. M., Hebda, L. (1989) Creep in SFRC element under long-term eccentric compressive loading, in Proc. Int. Conf. Composite Structures, I. H. Marshall ed., London Elsevier Applied Science pp. 743-54. 

FIGURE 5.9 Schematic representations of nonhomogeneous stressed states pure bend (a) three-point beam bend (b) eccentric compression (c) the loss of elastic resistance (d) indentation by a rigid sphere (e). 

JFIGURE 3 Plain concrete prism subjected to eccentric compressive load. 

We have applied our model to plain concrete prisms sxabjected to uni axial eccentric compressive load (Fig.3). At any time, the damage factor gains the value D(M) due to the local stress history at each location M belonging to a damaged cross-section. Taking Eq.9 into account, the following expressions are easily derived from the equations of equilibrium ex pressed in terms of actual stress (see (1) for more details) ... 

Rotation of the pump rotor, which Is mounted eccentrically In the pump cylinder, traps entering vapor between rotor vane segments. As rotation continues, vapor is compressed then discharged into the exhaust box. Vapors then pass through four stages of Internal oil and smoke eliminators to remove 99.9% of lubricating oil from the exhaust. Oil is then returned to the recirculating oil system. 

For higher pressures, rotary compressors of the sliding vane type will give delivery pressures up to 1 MN/m2. In a compressor of this type, as illustrated in Figure 8.35, the compression ratio is achieved by eccentric mounting of the rotor which is slotted to take sliding vanes which sub-divide the crescent-shaped space between the rotor and... 

A scroll vacuum pump uses two interleaved Archimedean spiral-shaped scrolls to pump or compress gases (see Fig. 1.9). One of the scrolls is fixed, while the other orbits eccentrically without rotating, thereby trapping and compressing gases between the scrolls and moving it towards the outlet. 

Fig. 29. A rotary-plate pump a—schematic view 6—diagram of operation f—system being evacuated I—eccentric rotor 5—stator 2—space where gas is compressed 5—movable plates d—discharge opening 7—discharge valve ...

During the compression process on an eccentric press, there are other pressure ratios at the upper and lower punches. The pressure at the upper punch is usually higher than the pressure at the lower punch. A part of the pressure is lost in the material and in the resulting radial friction force against the die wall during the compression [1,2],... 

On a rotary press the filling of the die and the following compression process is done at the same time at different stations. The compression is carried out in the simplest case with two rolls touching the upper and lower punches and compressing the powder mixture. In contrast to the eccentric press, the upper and lower punches exert pressure on the tablet mixture from both sides at the same time. 

Tablets compressed on a rotary press generally show a more consistent hardness when the upper and lower sides of the tablets are compared, where the upper side of tablets compressed on an eccentric press is usually harder than the lower side [3],...

Figure 2 illustrates the difference in compression profiles of the upper and lower punches and the punch movement with fictitious rotary and eccentric presses. 

Another reason, to use a rotary press rather than an eccentric press for tablet compression is the dwell time is usually shorter on a rotary press (see Figure 3). 

Binary mixtures were prepared with varying drug contents (60, 70, 80, 90, and 95%) keeping constant the drug and excipient particle size. Table 24 gives the composition of the studied batches as well as the tablet thicknesses. The mixtures were compressed on an eccentric machine (Bonals A-300) without any further excipient. Cylindrical tablets with a mean dosage of 500 mg and a diameter of 12 mm were prepared at the maximum compression force accepted by the formulations. 

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