Applied Mechanics and Materials Vols. 744-746

Abstract: RPC(Reactive Powder Concrete) is a kind of high performance concrete which has many excellent mechanical properties, e.g. ultra-high-strength, high tenacity and good durability, and it has been applied in engineering practice. However, at present the economic research about RPC bridge is few at home and abroad, which has hindered the development of RPC bridge to some extent. By means of the mechanical analysis and economic research about NC(normal concrete ) beam bridge of pre-stressed steel strand (the span is 40m), RPC beam bridge of pre-stressed steel strand and RPC beam bridge of pre-stressed CFRP(Carbon Fiber Reinforced Polymer) tendon after the sectional optimization has been done, this paper reach the conclusion that the RPC beam bridge can greatly reduce the sectional size of beam bridge and reduce the weight by 23.7% , besides, the total cost of RPC beam bridge of pre-stressed steel strand is almost same with the total cost of NC beam bridge during the entire service period of bridge. Therefore, considering the long-term perspective, the integrated economy of RPC beam bridge of pre-stressed steel strand is good.

Abstract: To research the impact of inner concrete filled steel tubular (CFST) on the reinforced concrete (RC) pier confined by stirrups, a Matlab program based on fiber model was written to calculate the moment-curvature (M-ϕ) relationship. The program was utilized to compute the M-ϕ relationships of three piers with same longitudinal bars and stirrups, and the three piers were an ordinary RC pier confined by stirrups、a high strength reinforced concrete (HSRC) pier confined by stirrups and a steel tube-reinforced concrete (ST-RC) pier respectively. The rules about bearing capacity of section and curvature ductility along with axial load N were deliberated by comparing the numeral results of three piers. The ratio of peak moment M_k to yield moment M_y was defined as super coefficient λ_s, and the disciplinarian of λ_s along with N was discussed. Participation factor ξ referred to the ratio of the moment provided by inner CFST to the total moment of ST-RC pier, and the laws of ξ affected by ϕ and N were researched. The results show that ST-RC pier has higher ductility and higher bearing capacity of section, and ductility decreases more slowly than other piers with the increase of N. λ_s of ST-RC pier is highest among three piers in most cases. On conditions of different N, ξ shows different variation trend with curvature ϕ up, and the maximum of participation factor ξ_max is reckoned to be not affected by N basically.

Abstract: The finite element method model of a 670.56m span cable-stayed bridge was established and the dynamic characteristic and nonlinear earthquake-responses of it under uniform and traveling-wave excitations were systematic studied. Results show that: 1) its former 10 rank frequency are located very dense which shows that more modes shape should be considered when dealing with the dynamic analysis. 2) The traveling-wave excitation has greater effect on long-span cable-stayed bridge, especially on the more flexible component and great attention should be paid to the design of such kind of bridge.

Abstract: The object of this paper analyzes the reliability level of pre-stressed concrete continuous girder bridges designed with the Chinese codes including the code for design of highway reinforced concrete and pre-stressed concrete bridges and culverts of JTG D62-2004 and JTJ 023-85 using cantilever construction method. Typical cross-sections used in the example bridge are considered at service stage. Load and resistance parameters are treated as random variables. The statistical parameters are based on the available literature, test data and survey results. Reliability indices are calculated by iterations using the first-order second-moment method. The calculated results indicate that the reliability indices on the code of D62-2004 vary considerably to the code of JTJ 023-85. And it could provide the references for the reinforcement of old bridges and the design of new bridges using the cantilever construction.

Abstract: Destruction of bridge expanded joint is a serious problem for concrete bridge. Based on 5 years measured data, the temperature in the different positions of the concrete box girder was systemically analyzed to illuminate the cause of the bridge expanded joint damage. A method for predicting the extremum value of the temperature difference of concrete girder was proposed by use of the extrema analysis and curve fitting based on the temperature in the different positions of the concrete box girder. The relationship is quite useful in estimating the destruction of bridge expanded joint by effective temperature difference in concrete box-girder.

Abstract: In order to control the degree of comfort in vibration caused by human in a steel aerobridge of Shenzhen T3 terminal building, the theory of structural vibration control and TMD (Tuned Mass Damper) was used to control the vibration caused by human and conduct comfort design. At first, 3D analysis model of the structure was developed through general finite element analysis software MIDAS / GEN. And time-history analysis was carried out in different working conditions of human walking or jumping to analyze the dynamic response before and after the TMD was installed. Then, vibration test was conducted in-situ to determine its dynamic property and record its peak acceleration before and after the TMD were installed. Test data was then compared with data from the analysis model of the structure based on analysis software. The results show that the installing of TMD and making adjustment of the stiffness of the TMD based on the actual test make the structure meet requirements of degree of comfort in vibration caused by human. The effect of the vibration control is good.

Abstract: Relative displacement method is considered to be one of the most direct methods used for rapidly and conveniently evaluating the deterioration of hinged joints in fabricated hollow slab bridges. Based on the relative displacement method, a statistical analysis on the results from the measured 265 diseased hinge joints in 11 bridges was conducted in this paper. The status of hinge joints can be classified into four regimes of perfect, micro damage, damage and failure according to a dimensionless damage evaluation index η, whose value was also presented in the paper. Finally, the reasonable strengthening time and strategies for hinged joints and corresponding strengthening strategies were proposed based on the parameter η.

Abstract: The distribution of the temperature gradient and temperature change of the pre-stressed concrete box girder are extremely complicated because of the multiplex environment. Temperature load has attached great importance in the field of engineering, and it has a great influence on the bridge’s structure, especially the box structure. The engineering background of this paper is a typical three-dimensional pre-stressed concrete continuous box girder bridge with variable cross section, comprising five spans in one continuous unit. Experiment on it and research the change rules of the temperature distribution, as well as the influence of the structure’s internal force resulted by temperature. Finite element software-Midas/FEA is used to model and calculate the bridge in order to analyze the temperature influence on structure’s stress in contrast to the measured data from the experiments

Abstract: In order to study the stress distribution law of simply-supported box girder bridge deck pavement under the effect of triangular concrete cushion, finite element analysis program is used to analyze distribution regularity of stress among asphalt and cement concrete cushion at the thinnest thickness of concrete cushion and transverse slope degree under the action of eccentric load which is applied in the most critical position. The result indicates that the first principal stress in asphalt pavement, the interface normal tensile stress and interface shear stress will reduce when the cushion layer thickness and transverse slope degree increase, however, the thinnest thickness of cushion should not be less than 3 cm. Considering the total weight of structure, cushion thickness should not be too large either. The thinnest cushion thickness of simply supported box girder bridge pavement layer is recommended for 3-4cm while transverse slope for 2-3%.

Abstract: Contraposed the hydration heat of large volume concrete, based on the introduces of raw material, the effect of fly ash mix amount in large volume pile cap concrete was mainly analyzed combined with project case of Yellow River Bridge in Baotou-Shulinzhao Highway. Moreover the temperature and temperature stress in different mix amounts were analyzed by the finite element software to confirm the appropriate mix amount of fly ash and the mix proportion of concrete. Finally, the consequence of the large volume pile cap temperature control was certified by the practice of construction.