Guojin Tan

Pavement performance evaluation of asphalt mixtures containing oil shale waste

Oil shale ash (OSA) is a waste or by-product material, which may cause hazards for human health and environment. The objective of this paper is to evaluate the potential of OSA as partial replacement of mineral powder in asphalt mixture. For this aim, asphalt mixtures were prepared by two types of OSA wastes as partial filler replacement and compared with the control mixtures prepared with traditional mineral filler in this paper. Marshall tests were performed to investigate the volumetric and mechanical properties of asphalt mixtures. Moreover, the pavement performance including high-temperature dynamic stability, low-temperature cracking resistance and moisture stability were conducted. Results show that all required properties and pavement performance of asphalt mixture containing OSA at the optimum asphalt content (OAC) are satisfied or even improved in comparison with ordinary asphalt mixture in accordance to Chinese standard specification. The performance of asphalt mixture containing OSA was also evaluated based on a test road. In terms of environmental and economic as well as pavement performance points of view, OSA can be used instead of partial mineral filler in asphalt mixtures.

Design Optimization of SBS-Modified Asphalt Mixture Reinforced with Eco-Friendly Basalt Fiber Based on Response Surface Methodology

This paper investigates the effects of basalt fiber content, length and asphalt-aggregate ratio on the volumetric and strength properties of styrene-butadiene-styrene (SBS)-modified asphalt mixture reinforced with eco-friendly basalt fiber. An experimental scheme was designed to optimize three preparation parameters for the Marshall test indices based on response surface methodology (RSM). The results showed that basalt fiber content presents a more significant effect on air voids, voids in mineral aggregates and voids filled with asphalt. Basalt fiber length is more related to Marshall stability, and flow value exhibits a significant variation trend with asphalt-aggregate ratio. The optimization of preparation parameters is determined as follows: basalt fiber content is 0.34%, length is 6 mm, asphalt-aggregate ratio is 6.57%, which possesses favorable and reliable accuracy compared with experimental results. Furthermore, basalt fiber reinforced asphalt binder and mixture were also studied, and it was found that basalt fiber can enhance the performance of asphalt binder and mixture in terms of cone penetration, softening point, force ductility, as well as pavement performance tests.

Analysis of Aggregate Morphological Characteristics for Viscoelastic Properties of Asphalt Mixes Using Simplex Lattice Design

Morphological characteristics of aggregates have direct impacts on performances of asphalt mixes. This paper aims to investigate the effects of the morphological characteristics of fine and coarse aggregates on the high-temperature viscoelastic properties of asphalt mortars and mixtures. For this purpose, an experimental proportion scheme was designed for asphalt mixes prepared with three different types of aggregates (basalt, andesite and pebble/river sand) based on the simplex lattice design (SLD) method. Three morphological parameters were chosen to characterize shape, angularity and texture of aggregates. Afterwards, the uniaxial compression creep test was conducted for asphalt mixes and the high-temperature viscoelastic properties were obtained based on Burgers model. The effects of fine and coarse aggregates on the viscoelastic properties are analyzed through asphalt mortars and mixtures, respectively. The results showed that aggregate morphological characteristics correlate with the high-temperature viscoelastic properties of asphalt mixes, especially for fine aggregates. Aggregates with complex morphological characteristics are conducive to improving the deformation recovery and anti-deformation of asphalt mixes. Furthermore, coarse aggregates can enhance the anti-deformation of asphalt mixture effectively due to its skeleton effect.

Dynamic Response of a Nonuniform Timoshenko Beam with Elastic Supports, Subjected to a Moving Spring-Mass System

This paper is concerned with the dynamic response of a nonuniform Timoshenko beam with elastic supports subjected to a moving spring-mass system. The modal orthogonality of nonuniform Timoshenko beams and the corresponding overall matrix of undetermined coefficients are derived. Then the natural frequencies and mode shapes of nonuniform Timoshenko beams are obtained by the Runge–Kutta method and cubic spline interpolation method. By using the Newmark-β method and the mode summation method, the vibration equation of Timoshenko beams subjected to a moving spring-mass system was established. A comparison of results between the proposed method and finite element method reveals that this method possesses favorable accuracy for dynamic response analysis. In numerical examples, the effects of the support spring and moving spring-mass system on Timoshenko beams have been examined in detail.

Creep characteristic analysis of asphalt concrete based on the modified Burgers model

The external viscous component of Burgers model was improved based on the creep test data of asphalt mixture. And the constitutive equations of the modified Burgers model were obtained. This modified Burgers model was verified with the dynamic indirect tensile test. The parameters of modified model has been identified by nonlinear fitting of the indirect tensile strain curves. It proved that the modified Burgers model can be used to characterize the all creep stages of asphalt concrete.

Vibration Analysis of Reinforced Concrete Simply Supported Beam versus Variation Temperature

It is well known that temperature has great influence on modal characteristics of bridges. The relationship between them has been studied by using statistical mathematics, numerical analysis, and field’s monitoring methods, which have relatively narrow applicability. Therefore, it is necessary to analyze their relationship theoretically. In this paper, the relationship between temperature and modal characteristics of the simply supported beam is investigated based on theoretical calculation method. Firstly, the temperature field is analyzed to find out the main factors that lead to the changes of modal characteristics. Secondly, the dynamic equations of simply supported beam under the effect of temperature are established. Next, a test beam is constructed to validate the proposed calculation method experimentally. The calculated results are in good agreement with those from the experiment. Finally, the proposed method is successfully applied to real engineering.

Monitoring system for cable force state of steeve arch in cold area

The cable force state of steeve arch is one of the key factors which determine the safety of operation of the steeve arch. In order to master the cable force state of steeve arch, a cable force monitoring system has been established, and in this monitoring system, the cable force state can be real-time monitored by using random vabration response of suspenders under ambient excitation. In order to improve the data transmission efficiency, firstly, in the monitoring system, the collected massive data can be discriminated and screened, and then only the screened effective data will be transferred. The single cable force and the full bridge cable force with short length can be analyzed exactly. And the cable force monitoring system has high immune function in the influence of ambient temperature difference on cable force. By the analogue debugging of this monitoring system, the effectiveness and reliability of this monitoring system in the cable force state monitoring application of steeve arch in cold area are verified.

Prediction method for the deformation of deep foundation pit based on neural network algorithm optimized by particle swarm

Prediction of the deformation is an important means of the construction parameter adjustment and the construction safety of deep foundation pit. Combining particle swarm optimization with neural network algorithm, The prediction method for the deformation of deep foundation pit based on neural network algorithm optimized by particle swarm is established. In order to improve the prediction accuracy and prediction efficiency of the neural network algorithm, The initial weights and the initial threshold value of neural network model are optimized by using particle swarm optimization. In the neural network model, the deformation of foundation pit is predicted by the optimized initial weights and the optimized initial threshold value. Relying on the practical engineering, the effectiveness and practicality of the method proposed in this paper are verified.

Theoretical and Experimental Analysis on Bending Creep Characterizations of Asphalt Concrete Using Modified Method

The analytical solution of asphalt concrete bending creep test was established based on bars mechanics theory. The beam end slope was solved using numerical method, and the calculating method of strain rate in bending creep which is based on small deformation theory was modified. The equations of strain rate and correction factors were obtained for bending creep test. The changing in the effective span of the beam resulted in creep strain changing. This improved theory can be used to explain strain rate variation with the temperature effect. It reduced the limitations of small deformation theory and has more accuracy in calculating strain rates for large deformation bending creep at medium temperatures. It provides a theoretical basis for accurately analyzing the bending creep behaviors of asphalt concrete.