Advanced Materials Research Vol. 831

Abstract: The contraction ratio of lower bucket is an important parameter of the series jet characteristics of the allotypic hybridtype flip bucket (AHFB). Due to the effect of contraction in lower bucket and diffused in upper bucket, the jet flows cross and impact in the space domain. Systematic hydraulic model tests were developed to describe the rule of water-diversion and pressure distributions. This paper presents the variation of jet trajectory length and the local scour of this combined bucket. Based on these, the variation laws and estimation equations for hydraulic characteristics with different contraction ratio are proposed.

Abstract: The dynamic performance of large-span steel-concrete composite bridges with external tendons is investigated by deriving the formula of equivalent damping ratios of composite bridges, and by considering the influence of shear connectors stiffness of composite girders, external tendons, and pile-soil dynamic interactions on the dynamic properties of steel-concrete composite bridge. Finite element analysis indicates that the equivalent damping ratio has a significant influence on the dynamic response and damping coefficient adjusted must be conducted in structural dynamic analysis.

Abstract: A direct 3D finite element (FE) modeling of fracture processes in reinforced concrete bridge structures is considered with account of the macrocracks initiation and propagation, real geometry of reinforcing elements, discontinuity in the bond-slip behavior, using elastic-plastic-damage constitutive equations for concrete. The comparison of obtained FE results with experimental data is presented and discussed for the pulling ribbed bars out of concrete blocks, the spalling of concrete cover at the automobile bridge and cracking of ballastless deck at the railway bridge.

Abstract: This article filled up the blank between risk management in design stage and construction stage of bridge engineering, and proposed the concept of carrying out safety risk management through making prevention measures in construction organization plan. Based on the intrinsic safety theory, five elements, i.e. human, object, environment, system and method in bridge engineering construction management plans were analyzed by analytic hierarchy process and systemic analysis method. Fifteen crucial sub-elements were summarized and index system method was established for the safety risk assessment of sub-elements in construction management plans. Based on the research of the transformation of risk sources in construction management plan to risk events in construction period, expert survey method was established for the safety risk assessment of sub-elements in construction management plans.

Abstract: Semi-rigid pavement, which mitigates the drawbacks of cement concrete and asphalt concrete pavements, is being widely used, but the body of research on enhancing the performance of cement grout remains limited. This paper discusses basic research on the development of a rapid hardening cement grout for semi-rigid pavement that meets chloride resistance, rheological property, and strength requirements. Evaluation results indicate that with up to 10% addition of expansive additive, in terms of the weight fraction of cement particles, the rheological property and strength requirements were satisfied. Examination of the chlorine ion penetration resistance revealed that an increase of expansive additive content yielded lower numbers of charged chlorine ions, resulting in 75.5 times higher resistance over a plain mix designed without expansive additive. In contrast, it was found that excessive addition of expansive additive, that is, beyond 10% in terms of the weight fraction of cement particles, was detrimental to achieving the desired rheological property.

Abstract: Based on the analysis of corrosion mechanism, combining with the characteristics of bridge structure, aiming at the existence of corrosive medium and complex physical environment, such as the freezing thawing, corrosion and chlorine salt as well as dry wet, freeze-thaw cycle [, This paper expounds the research and construction practice of the additional anti-corrosion measures of bridge pier caps concrete in Beijing-shanghai high speed railway. It has a certain guiding significance to the similar Bridges in corrosion protection construction.

Abstract: In this paper, the relationships between the high temperature performance of two different kinds of asphalt modified by Trinidad Lake Asphalt and the different amounts of the Trinidad Lake Asphalt were investigated,The results showed that: Trinidad Lake Asphalt could increase the-softening points of the modified asphalts, reduce penetration and enhance the viscosity. However, the variation trends of each index in two modified asphalts were different; among the high-temperature dynamic rheological performance indexes, complex modulus became larger, phase angle became smaller, and rut factor increased. These results indicated that Trinidad Lake Asphalt can effectively improve the high temperature stability and the modified asphalt had higher resistance stability to rutting. The complex modulus of modified asphalt with different amount of the Trinidad Lake Asphalt had the similar variation trends with frequency, The asphalt modified by Trinidad Lake Asphalt should be delayed elastic body, and its sensitivity to the frequency had no obvious improvement.

Abstract: It has become one of the focus topics that using CT (Computer Technology) to obtain asphalt internal microstructure, but combining CT scan cross-sectional different characteristics to carry out digital image processing is rare at this stage, technical means that distinguishing internal material are still relatively rough and arbitrary large, can not be combined between digital image processing and mixture not damage test together effectively. This paper carried out image segmentation based on EM algorithm of Gaussian mixture model (GMM), analysis microstructure uniformity quality of asphalt mixture, and explores internal volume composition case by testing deeply. The results show that Gaussian Mixture Model (GMM) used in this paper can handle CT scan tomographic images better , judge aggregate distribution of asphalt mixture by sector scan method, and evaluate uniformity distribution of asphalt mixture aggregates through aggregate particles area ratio statistical analysis, the research results of this paper can provide reference significance for asphalt microscopic field study .

Abstract: In order to research the development of the internal cracks and the evolution of damage in asphalt mixture under loads, German Compact-225 type industrial X-ray computerized tomography (X-CT) was used to scan the specimen of asphalt mixture and the visualization of the internal damage process could be achieved, the damage under loads in various stages could be described accurately. Then, the damage evolution process was analyzed by calculating CT numbers, and a curvilinear relationship between the damage variable and the strain-stress was established. The results indicate that X-CT technology can be used as an effective way to detect and analyze the meso-damage of the asphalt mixture and that it further provides an important basis for quantitatively describing the evolution rule of the meso-damage.

Abstract: Transportation agencies have recently been struggling to carry out rapid roadway construction and repair work with minimal disruption to the motoring public, and they are pursuing sustainable and perpetual roadway systems with minimal maintenance over their service life. This study sought to develop a roadway joint system as a part of research on a sustainable-perpetual-modular (SPM) roadway system. In this study, two boundary conditions were considered with varying support offsets. Dead load, live load, and temperature load were considered and the corresponding displacements were computed. Roller supports at both ends produced larger displacements compared to hinge supports at both ends. Analysis results exhibited that a support offset equal to 0.0 m produced the smallest displacement. The results of this study will provide valuable information for the design of modular roadway joint systems.