Applied Mechanics and Materials Vols. 90-93

Abstract: The fractional dynamics equation of a viscoelastic two-member truss system, in which fractional derivative model introduced to simulate the materials’ characteristics, is proposed. The simplified single DOF differential equation is developed combined with boundary conditions and symmetry. Dynamic behaviors of the fractional single DOF system with harmonic loads are discussed by numerical calculations. The results show that: the system may lead to chaotic motion via period-doubling bifurcations or intermittent routes; the dynamical character is greatly inflected by the varying of excitation amplitude or damping coefficient or fractional order.

Abstract: In the process of steam curing to high-speed railway’s simply-supported box girder, there are some problems must be faced such as the difficulty to determine steam curing system and to achieve automatic temperature control. With the construction site conditions of simple-supported box girder in Longwang beam field which is located on Shijiazhuang-Wuhan (Shi-Wu) section of Beijing-Guangzhou high-speed railway, the paper proposes the appropriate steam system for simply-supported box girders, determines the appropriate equipments, explores the temperature control system in the process of steam curing to the simply-supported box girder's concrete, and takes the temperature test of steam curing in the field. Results show that, the steam curing technology in this paper can increase the production efficiency of beam in production site, and effectively guarantee the prefabricated quality of simply-supported box girder.

Abstract: Due to the usage of high-strength concrete, excessive hydration heat is generated in the whole span box girder of high-speed railway. The maximum allowable temperature should not exceed 60°C according to the Technical Guide on Railway Bridge Construction of Passenger Dedicated Line. However, according to the field measurement and simulation to the maximum temperature of box girder concrete, we find that the maximum hydration temperature of concrete is generally more than 60°C which is the limited value of the specification. The research results show that the limited value of maximum hydration temperature for box girder concrete can be relaxed to 65°C.

Abstract: Longtan River Bridge, which the length of the main span is 200m and the height of the main pier is 178m, is a long span continuous rigid frame bridge. Temperature field of the box-pier and the box-girder due to solar radiation were measured. Regression analysis of the temperature difference has been done by using the least square method, and the fitting curve of the vertical and the transverse non-linear temperature difference distribution of box-pier and box-girder are obtained in this paper

Abstract: Taking Wuhan Erqi Yangtze River Bridge as an example, based on link element, shell element, and beam element, a double beam nonlinear finite element model is purposed using popular finite analyzing software ANSYS. The internal force and deformation characteristics of composite beam cable-stayed bridge with three towers is analyzed by double beam model, and compared to the single beam. The results show that the double beam nonlinear FE model, which have less freedom and conveniently calculate, can be used to well analyze the nonlinear of composite beam cable-stayed bridge with three towers.

Abstract: The several familiar ice-structure interaction models were established according to collision dynamics theory. The numerical simulations of the ice-structure interactions were implemented by using the explicit dynamic analysis software ANSYS/LS-DYNA, according to the concrete reduction model and bi-axial strength criterion established by indoor test after freezing-thawing damage. The simulated ice force and structure displacement response were presented using ice sheet with a certain constant speed moving to the structure. What more, the effect of super bridge system is taken into consider in simulation models. The simulated results show that the ice forces applied on structure are insensitive to alteration by ice velocity, and the circular structure and the rectangular one are unlikely to generate ice-induced vibration because of the effect of super bridge system.

Abstract: Soil condition is a major impact factor on the strength of cemented soil. In order to study the relationship between the soil conditions and the strength of cemented soil in deep mixing column under the circumstance of thick soft clay in the Nansha area, the uniaxial and unconfined compressive strength tests were carried out, from which stress-strain curves of the cemented soil and strength-depth curves of column body were obtained under three different soil conditions. Analyzing these curves, conclusions can be made that the strength of different parts of cement soil from deep mixing pile varies greatly in the Nansha area. Among the samples, the cement mixed with silty clay has the highest strength, while the lowest one is the cement mixed with mud. Besides the above results, compressive strength values(fcu)of cement soil is determined, which can be of great significance to calculate the bearing capacity of deep mixing piles.

Abstract: Steel-concrete composite plates are formed using steel plates connected to a concrete slabs by means of welded stud shear connectors. The flexibility of connection between the steel plates and concrete gives rise to interface slip and additional deflection. An analytical model considering slip effect for composite plate is presented in this paper. Analytical solutions for deformation of composite plate under lateral load and elastic critical buckling load of composite plate under axial compressive load are deserved. The model and the solutions are then validated by means of finite element analysis. According to the parametric study, when impact factor greater than 5, the critical buckling load of simply composite plate is close to the superposition of the critical buckling loads of steel and concrete slabs and the interaction of both slabs can be ignored.

Abstract: Because of good mechanical properties of the fiber composites, the fiber bundles without the resin curing process and with the features of high modulus, high strength and good performance of creasing resistance etc, can be used in prestressed structures. According to the strength properties of the fiber, the tensile characteristic function of the fiber bundles is derived. The tensile test is designed and the parameters of the weibull distribution are estimated based on the result of the test. The ultimate strength of fiber is inversely proportional to the length of fiber. The calculating strength should be reduced in design, because the discreteness of the strength of the fiber bundle in test is much larger than the calculated values.

Abstract: nchor is the key component for force transmission of prestressed structure. It is difficult for the current sealing technology of anchor to ensure the normal performance of strand. And it will directly affect the bearing capacity and durability of the whole prestressed structure. The advanced method abroad smears anti-corrosion grease at the end of anchor, and then covers it with plastic cap. Based on the national patent: the method of using heat shrinkable material to protect prestressed anchor(patent number: ZL200710304303.2), some experiments of using heat shrinkable material to protect anchor are carried out, such as the construction technology verification, the electrical insulation and the sealing experiment, and anti-stripping experiment. The results show that the method of using heat shrinkable material to protect anchor has the advantages of simple and reliable construction technology, short construction period, low cost, good electrical insulation, high sealing property and anti-stripping strength. This method can protect the anchor of prestressed system very well, and has wide application value.