Based on attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy and principal component analysis (PCA), four kinds of asphalt (two kinds of matrix asphalts, TPC70# and JL70# and two kinds of modified asphalts, SBS-1 and SBS-2) were aged using the rolling thin-film oven test (RTFOT). The multiple stress repeated creep recovery test (MSCR) was carried out on an AR1500ex dynamic shear rheometer (DSR). The PCA was carried out on the attenuated total reflection infrared spectrum of a pretreated aged asphalt, the principal component factors (oxidation factor and component change factor) were determined, the comprehensive index F was calculated, and a prediction model of aging time history was established and verified. A prediction model for the aging asphalt recovery rate R was established based on the functional group index. The relationship between the recovery rate R and aging time history of each aging asphalt was analyzed and the fatigue life of each aging asphalt based on the rate of dissipated energy change (RDEC) was compared. The correlation between the comprehensive index F and fatigue life of asphalt was also analyzed. The results show that the order of resistance to the high-temperature deformation of each aging asphalt is as follows: SBS-2 > SBS-1 > TPC70# > JL70#; the prediction model of aging asphalt recovery rate R based on functional group index has good reliability. Taking the loading cycle corresponding to the sudden increase of the inflection point of the curve, i.e., the fatigue life NRDEC, as the evaluation index, the fatigue life order of each aging asphalt is SBS-1 > SBS-2 > JL70# > TPC70#. There is a positive correlation between the fatigue life of aged asphalt and the comprehensive index F of asphalt. The correlation degree R2 is 0.85; i.e., with the increase of the comprehensive index F of asphalt, its fatigue life also increases. It was found that it is feasible to analyze the aging time history and fatigue life of asphalt by infrared spectroscopy, and it can provide a rapid and non-destructive prediction method for the practical engineering application of asphalt.
Assembled skewed hollow slab bridge can improve the line shape of the road and adapt to the complex and changing urban street conditions, making the whole route smooth, thus shortening the route and bridge length and improving economic benefits. Assembled skewed bridges are more complicated due to their forces, which leads to more prominent problems in the hinged joints of inclined bridges. When lateral prestressing is applied to the two straight sides of the skewed bridge, it is difficult to achieve the effect of prestressing at the ends. Aiming at this problem, a scheme of reinforcement with transverse prestressed carbon fiber slabs is proposed, and a solid model of fabricated oblique slab bridges is established by ABAQUS finite element software. The results show that the method of transverse prestressing CFRP plate reinforcement is effective for Assembled Skew Hollow Slab Bridge.
With the continuous development of image technology, the quality of image processing has also been greatly improved. But its evaluation index is limited to objective evaluation, which results in high image quality but poor visual quality. However, subjective evaluation does not have specific indicators, it cannot be quantitatively detected, and it is poorly informatized and highly dependent on the observer’s knowledge background and emotions. Therefore, this study has conducted research on subjective evaluation, and proposed to use three-dimensional volume rendering and reconstruction as the auxiliary index of subjective evaluation to achieve the effect of stereoscopic image and reduce the degree of subjective dependence on the observer. The experimental analysis shows that the method has high practical application value and obvious effect, and can be used as an auxiliary index for subjective evaluation.
The relationship between natural frequency and prestress-force is built to evaluate effective prestress-force of beams based on the theory. Two corresponding test mode beams are built up to verify the theory, the experiment results show that the natural frequency will decrease along with prestress-force decreasing, which is coincident with the result of theory. As a result, effective prestress-force is predicted by using the measured natural frequencies. Therefore, the research result demonstrate it is feasible to assess the effective prestress-force with dynamical method.
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