Styrene-butadiene-styrene (SBS) is widely used in asphalt modification to obtain superior high-temperature performance. Nevertheless, studies on the low-temperature properties of SBS-modified asphalt are not satisfactory. Orthogonal tests are valid in analysing the results. In this paper, the main factors (SBS content, sulfur content, and the addition of rubber processing oil) for improving the low-temperature performance of SBS-modified asphalt were analyzed base on the orthogonal tests. Firstly, the frequency sweep test, bending beam rheometer (BBR) test, and force-ductility test were conducted to evaluate the low-temperature properties of SBS-modified asphalt. Investigation of low-temperature parameters obtained through these tests was conducted base on the orthogonal analysis method. The G-R parameter was abandoned in the analysis of the orthogonal method for the result that the increase of SBS content was negative to the low-temperature properties by the Glover-Rowe (G-R) parameter, which were contrary to the results of BBR and force-ductility tests. Moreover, the other parameters (ΔTc and toughness) sorted according to the orthogonal analysis method indicated the effect on low-temperature performance of the SBS-modified asphalt as SBS content > rubber processing oil > sulfur. As shown above that both SBS and rubber processing oil play a critical role in improving the low-temperature properties of SBS-modified asphalt, for SBS could resist the generation and subsequent propagation of cracks while the rubber processing oil could supplement the maltene loss.
Because of their excellent structural performance, strong plasticity, and attractive appearance, cast-steel joints have gradually become a new type of joint for long-span steel-pipe modern architectural structures. Landscape bridges whose shapes are especially attractive have emerged; many have new and unique shapes and complicated structures. Some large-scale steel-pipe intersecting joints are designed in such structures. An innovative approach is presented: the use of cast-steel joints as two large-scale pipe intersecting joints of a special-shape tower in the design of a landscape cable-stayed bridge crossing over an expressway. The design methods for cast-steel joints that can be used on similar projects are also discussed.
Urban space condition is a limitation for social economic development, and new space should be investigated. Expressway resolves the problem in one way, which makes the urban spatial extension multi-poled, organized and form a new urban system by improving the accessibility of area along the expressway. Nowadays, urban expressway becomes an important mean that resolves the city transportation problem. Transverse section types of urban expressway include integral highway and separated highway or a combination of these two types. This research explored the method of using traffic simulation technology to evaluate the operation quality using index such as average delay, travel time, and minor roadway left-turn time. Applying computer simulation, traffic operation was simulated under the condition of future traffic flow. The evaluation index and their differences were obtained.
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