Applied Mechanics and Materials Vols. 638-640

Abstract: This test took dynamic strain detection method depending on time history curve of the dynamic deflection or the dynamic strain analysis of moving load in the control section to obtain impact factor. Using the method of environmental random vibration testing tested vibration response signals of L / 4 section of bridge test span , the cross section and 3 L / 4 section to identify the dynamic characteristics parameters of the overall vibration of Bridge, so that to determine current situation of application , assess the carrying capacity of bridge and test design load bearing capacity. According to the results of load test,the bearing capacity of Tiansheng bridge meets the requirements of "road - grade I" load level.

Abstract: The static load test schemes of Tiansheng bridge are briefly discussed . Through the comparative analysis of the theory values and the measured values , understand the actual work condition of bridge structure under test load and evaluate the bearing capacity of bridge structure .Through comparison of modeling datas and the measured values , test correctness of testing program, providing a scientific basis for the bridge safety and research in great depth.

Abstract: In order to determine the mix proportion with better anti-cracking performance of lime and fly-ash stabilized coal gangue roadbase materials, anti-cracking performance of lime and fly-ash stabilized coal gangue influenced by quality ratio of lime to fly-ash was studied based on the same aggregate gradation and the same aggregate ratio. And then crack of test road with different mix proportion was observed. Results show that both temperature shrinkage anti-cracking coefficient and drying shrinkage anti-cracking coefficient vary along parabola rule with the decrease of the quality ratio of lime to fly-ash. The mixture have the best anti-cracking performance when the quality ratio of lime to fly-ash is 5:15, which was test and verify in the transverse crack observations of test road. Lime and fly-ash stabilized coal gangue roadbase materials have a good anti-cracking performance and suitable for base in the pavement structure. The reasonable ratio of lime and fly-ash stabilized coal gangue roadbase materials in the engineering should be 5:15:80.

Abstract: Urban traffic link tunnels (UTLT) have a complex design and are a significant fire hazard. Due to the circular nature of the tunnels, smoke can easily spread through the tunnel during a fire and form a circulation loop, severely hampering safe evacuation and rescue. In this paper, the 2.8km long UTLT in Sichuan, China's Dayuan central business district (CBD) was the study subject. Fire dynamics and similarity theory were employed to perform theoretical calculations and numerical simulations targeting four different mechanical smoke extraction methods under typical fire conditions. Smoke movement was quantitatively analyzed, thus determining which of the four plans was the optimal smoke control technique: semi-transverse ventilation combined with sinking-courtyard air compensation, with ventilation beginning in the fire zone and the two flanking smoke control zones at a rate of 20 ventilations/hour. Our result provides a theoretical basis for designing and running a smoke control system in relevant projects at home and abroad, and serves as both a theoretical and a constructive practical ground for formulating regulations related to UTLT.

Abstract: Wheel-rail contact stress is foundation of the relationship between wheel and rail, and also an important basis for investigating further wear, surface damage and other problems of wheel and rail system. A three dimension elastic-plastic wheel/rail contact model is established using non-linear finite element method. The changes of wheel/rail normal contact stress, Mises stress and elastic-plastic deformations are analyzed under different conditions in heavy haul railway. A method is provided for a foundation of the future study of wheel-rail contact wear, fatigue and cracks germination and development in this paper.

Abstract: Since twentieth Century, the middle of 80's, our country highway enters the building climax. By the end of 2011, our country highway traffic mileage of 85000 kilometers, accounting for about 80% of the asphalt concrete pavement. Along with the age increasing and the mileage of highway's growth, has long suffered from the traffic load and environmental effects of the asphalt pavement will have varying degrees of damage, repair workload of asphalt pavement will be bigger and bigger, more and more complex. In this situation, has the important meaning of preventive maintenance of Expressway Asphalt pavement. This paper introduces the present situation of preventive maintenance of highway at home and abroad, and points out the significance of preventive maintenance on highway and economic development, discusses the measures and preventive maintenance of asphalt pavement.

Abstract: Asphalt pavements form an integral part of any transportation system. The structural capacity of the hot mix asphalt concrete layers depends on many factors including its temperature. Moreover, temperature can be a major contributor to several types of distresses. Therefore, temperature is a significant factor that affects the performance and life span of a pavement. The Libyan road network expanded at a phenomenal pace from approximately 1500 km of paved roads in 1970 to morethan 100,000 km in 2008. Brak region is located on the southern east of Libya at latitude (27°31'N) in the desert. With the recent SHRP and LTTP research findings, it was necessary to investigate the applicability of the models developed from these research studies to Brak's environmental conditions and more generally to the rest of Libyan desert reigions. This paper presents the research undertaken to develop models to predict high and low asphalt pavement temperatures in the Brak region . A pavement monitoring station was set-up in Brak to monitor air and pavement temperatures in different depth, wind speed and solar radiation. Data were collected for 365days. Daily minimum and maximum temperatures were recorded. A regression analysis was used to develop the minimum and maximum pavement temperature models, using air temperature, wind speed and solar radiation. This paper presents a new model for predicting maximum and minimum surface pavement temperature based on data collected by installed pavement monitoring station set-up at the Brak region.

Abstract: To get more information of changes in modified asphalt rheological performance before and after aging at different temperature, we did a very comprehensive study with DSR test method. In the different temperature ranges, the abilities to resist fatigue cracking and rutting, temperature sensibility of Cariphalte before and after aging have different changing rules respectively.

Abstract: In view of the condition that there has been few investigation on the fatigue damage mechanism of cement concrete under sulfate corrosion, based on coupled function experiment of magnesium sulfate corrosion and fatigue loads, the flexural strength, the relative dynamic elasticity modulus and the water absorption of the dry saturation surface were detected and the microstructures of concrete hydrates at different corrosion age were analyzed. The results show that the corrosion fatigue factor of cement concrete decreases rapidly with the increase of time. The main reasons for corrosion fatigue damage of cement concrete are the microcracks caused by expansion products and the cracks produced by fatigue load. The mutually reinforcing effect between magnesium sulfate corrosion and fatigue load is revealed.

Abstract: In order to provide scientific basis for the design parameters’ selection of sunken greenbelt of urban road, computational formulae of critical sunken depth and sunken greenbelt plant’s submergence time were derived based on the storage-infiltration analysis of sunken greenbelt. And then the influence of various factors on the sunken greenbelt design of urban road were computed and analyzed. Results show that: soil infiltration coefficient, design recurrence interval of storm and sunken greenbelt plant’s submergence time are the key influencing factors on the sunken greenbelt design. Under the same condition, critical sunken depth decreases linearly with the increase of soil infiltration coefficient, and increases nonlinearly with the increase of design recurrence interval of storm. Sunken greenbelt plant’s submergence time is proportional to sunken depth of sunken greenbelt, and it is inversely proportional to soil infiltration coefficient. When the value of soil infiltration coefficient is greater than 10^-6 m/s and the sunken depth range from 0 to 0.25 meters, submergence time of sunken greenbelt plants is all within 70h, and the sunken greenbelt can most infiltrate the rainfall storage in 1d. Considering all the influencing factors, soil infiltration coefficient of sunken greenbelt of urban road should be greater than10^-6 m/s and the appropriate sunken depth should be range from 0 to 0.25 meters.