Shahin Nayyeri Amiri

Analytical Solution of Interface Shear Stresses in Externally Bonded FRP-Strengthened Concrete Beams

AbstractThe fiber-reinforced polymer (FRP) plate or sheet debonding or cover delamination (concrete cover separation) failure mode in externally strengthened reinforced concrete beams has attracted a lot of attention. In this paper, a closed-form analytical solution is developed to determine the nonlinear shear stress distribution along the laminate interface and cover area for any load stage assuming a perfect bond. Trilinear moment-curvature and moment-extreme compression fiber strain is assumed to realize the analytical results. By differentiating the FRP axial tension force with respect to position along the beam, closed-form derivatives in terms of curvature and extreme compressive fiber strain are obtained. The results show three distinct regions of constant or stepwise linear shear distribution in each. These correspond to the uncracked, postcracked, and postyielded zones of the shear span. The results are shown to yield an exact match to those numerically obtained by dividing the shear spans into ...

A Realistic Theory of Soils Consolidation

The consolidation behavior of soils is usually predicted by making use of the convectional theory of consolidation proposed by Terzaghi.Laboratory observations of the consolidation behavior exhibit discrepancies between the theory and the results. These discrepancies are usually attributed to the secondary effects that occur during primary consolidation. On the other hand, Terzaghi’s theory presupposes the constancy of permeability and compressibility of the soil. In this study, the effect of variable permeability and compressibility on the consolidation behavior is investigated. For this objective, mathematical treatment of the behavior is presented. Subsequently, laboratory consolidation tests with mid-plane pore pressure measurements are conducted on soft, remolded, pre-consolidated and undisturbed samples of clay. The test results, when compared with the theoretical findings, indicate that most of the inherent discrepancies may be explained via the use of the theory developed in this study.

Effects of Different Pressure Increment Ration on One Dimensional Consolidation

In this paper, an experimental program was carried out to investigate the effect of the pressure increment ratio on the shape of compression time curves and secondary compression characteristics. Therefore, one dimensional consolidation tests on remodeled soft clay using different pressure increment ratios of one or less, with load increment duration of one week, were performed. Five different methods were used to evaluate the coefficient of consolidation v C which yielded reasonably close values. The secondary compression effects have been found to increase as the pressure increment ratio is reduced. The v C values and the end of primary void ratio effective stress relationship appear to be independent of the pressure increment ratio. INTRODUCTION The influence of the pressure increment ratio ⎟ ⎠ ⎞ ⎜ ⎝ ⎛Δ 0 σ σ on the results obtained from one-dimensional consolidation tests have been studied by a number of researchers including Newland and Allely (1960), Leonards and Girault (1961), Wahls (1962), Madhav and Sridharan (1963), and Lun and Parkin (1985). The results indicate that the rate of excess pore pressure distribution can not be reliably predicted from the Terzaghi theory if the load increment ratio is small. The compression versus the logarithm of time curves lose their characteristics shapes with an inflection point for ⎟ ⎠ ⎞ ⎜ ⎝ ⎛Δ 0 σ σ less than about 3 1 with the result that the Casagrande time fitting method becomes inapplicable. The time required for the development of the linear secondary compression part of the compression log time curves and 100 t have been stated to increase with decreasing ⎠ ⎞ ⎜ ⎝ ⎛Δ 0 σ σ . The relative 2794 Geo-Frontiers 2011