Advanced Materials Research Vols. 255-260

Abstract: It is well known that shear lag effect exists in wide flange concrete slabs. Traditionally, the effective flange width method is employed for considering the shear lag effect in a steel/concrete composite beam. The limitation of this method is that the load types and constraint conditions are generally ignored. In this paper, an analytical method using full flange width has been proposed by introducing shear warping shape function and intensity function of the shear warping displacement. By mean of two unknown functions: the vertical displacement of the whole cross section and the intensity of the warping, a variational balance condition which involves equilibrium equations with relevant boundary condition is imposed by the virtual work theorem. As a result, the shear-lag effect is considered by additional virtual external load, expressed as “additional bending moment”. The performance of this method dealing with elastic problem has been verified by finite element method using solid elements. Finally, the method is applied to investigate the long-term behavior of a beam fixed at two ends. It has been found that the results yielded from the code based on the effective flange width method are intervenient between those obtained from the current model with elastic and viscoelastic problem; the result errors of beam finite element model considering shear-lag effect can be modified by the method proposed in this paper.

Abstract: In view that dynamics research for self-anchored suspension and cable-stayed combination system bridge lags behind the practical application, this thesis analyzed its dynamic properties and seismic responses. By means of constructing a dynamic finite element model of the bridge for the dynamic properties and seismic response analysis, the thesis discovered the dynamic properties and the seismic responses laws of self-anchored suspension and cable-stayed combination system bridge. The dynamic finite element model was constructed based on the dynamic analysis theory and method, under the background of the first self-anchored suspension and cable-stayed combination system bridge in the world, and it was verifyed by on-site vibration test. The dynamic properties and the seismic responses laws provides a valuable reference for the design and maintenance of this type of bridge.

Abstract: The existence of center towers is the origin of performance difference between multi-tower suspension bridge and the traditional one, and longitudinal stiffness of the center tower is a decisive factor. Based on the finite element theory, the paper establishes numerical calculation model of multi-tower suspension bridge, and analyzes it’s static and dynamic performance variation by using different longitudinal flexural stiffness. Moreover, the factors that affect center tower stiffness are determined. Referring to judgment standards about usability and structure security given by existing research, the reasonable range of center tower stiffness is established. Besides, the paper tries to ascertain reasonable center tower stiffness by using the static mechanic performance of service phase as judgment standards.

Abstract: Taken the Chongqing PC composite box girder with corrugated steel web for background , spatial finite element calculation model is set up by adopting the mixed unit, the influence about geometric parameters of corrugated steel perforation is analyzed by used linear and nonlinear finite element calculation of steel box girder .It shows that bending stress and warping stress was reduced by increasing the bending angle of corrugated steel webs of composite beams, while the buckling strength improved obviously; the ratio of the top slab and the floor slab maximum thickness of box girder to the corrugated steel perforation should be about 20; the mechanical properties of composite beams will be improved by reducing the length of straight slabs of corrugated steel webs.

Abstract: Based on the finite element method, the seepage field of reinforced dykes of a reservoir is analyzed from hydro geological nature and characteristics of the impermeable wall. According to the typical cross-section of the reinforced dyke, performance-parameters of the dyke such as total water head, seepage velocity, seepage gradient are compared with the counterparts of the original dyke. Results in steady seepage are obtained. Generally seepage quantity decreases 45% from the original dyke. Permeability coefficients and defects of the impermeable wall are the most factors of affecting effectiveness of dyke reinforcement. Because piezometric tubes work well, measured dada are reliable, both measured and calculated data also coincide with each other well. The results show that the impervious reinforcing plan of the dyke is fit, the reinforced dyke can reach predeterminate impervious effects and meet the technical specifications. Safety of the reservoir is guaranteed.

Abstract: Taking an engineering design case about a city elevated curved box girders bridge, the dynamic calculating model of the curved box girders bridge is created by the finite element analysis program ANSYS. The analysis of curved box girders bridge with space seismic response are discussed, and a time history analysis is conducted for the curved box girders bridge subjected to the E1 Centro earthquake waves in two conditions.The internal force and the displacement time history response curve of the curved box girders bridge are obtained. The results indicate that the seismic response of curved box girders bridge with three-dimensional earthquake are bigger than two-dimensional, and consider the vertical seismic have considerable influence on the axial force of bridge piers, the internal force and displacement of box girders.

Abstract: Ha Shuang Bridge is located in Harbin city within Heilongjiang province in the east north of China. The purposes of this study are to monitor the damage in structural members of Ha Shuang prestressed concrete box girder oblique bridge before strengthening and to evaluate the dynamic performance of the bridge structure by adopting dynamic load test. Monitoring process of damage of the bridge structure shows that the web of box girder in the quarter of the second span (about 10.5m from the pier) suffers from serious shear cracks. These cracks extend from the top to lower flange of box girder. The width of cracks rang from 0.5mm to 2mm and the angle is 45 degree. There are 6 bending cracks. The spacing between these cracks rang from 20cm to 30cm and the width is 035mm. In the span No. 3 near the pier, the web of box girder appears 12 diagonal cracks have width rang from 0.1mm to 0.12 mm. The results of dynamic load test analysis show that the values of measured vertical natural frequency is w1 = 3.616Hz and horizontal natural frequency w2 = 4.492Hz less than the values of theoretical natural frequency which is 3.863Hz and 4.848Hz, indicating that the actual stiffness of the bridge structure is less than the theoretical stiffness. Therefore the dynamic working state of bridge structure is not good. Therefore the working state of bridge is not good and it need to repair and strengthening.

Abstract: Effects of stiffness, carrying efficiency and fatigue of the end anchor cable on the mechanical behavior of long span cable-stayed bridge, were discussed respectively. Firstly, the concept of the effective stiffness and the stress ratio were introduced to discuss the effects of the dead load stress level and the stress ratio on the effective stiffness of the end anchor cable. Secondly, the effect of the cable material on the vertical carrying efficiency of the structure was analyzed. Finally, the main influential factors on the fatigue performance of the end anchor cable were analyzed in detail. It is shown that improving the dead load stress level and keeping the low stress ratio would increase the effective stiffness of the end anchor cable. The section of the end anchor cable effects on stiffness of the structure under high stress level. It can be drawn that as a novel material, The CFRP end anchor cable will increase the load carrying level of the long span cable-stayed bridges. It can also be concluded that the length of side span and main span, the height of pylon, the area of the cable section and the live load collection degree are all the main effective factors to the stress amplitude of the end anchor cable. It is suggested that in the practical design of large span cable-stayed bridge, all the effective factors together with the global state of the structure should be taken into account comprehensively.

Abstract: Bridge constructions of crossing wider sea straits allow the span of suspension bridge to move forward unceasingly, but the self-weight stress of the traditional high-strength steel as the material of main cable accounts for the ratio of allowable stress will be increasing with the growth of main span.That will limit the main span and load-carrying efficiency.Due to its high tensile strength,small mass density,excellent corrosion and fatigue resistant ability,the carbon fiber reinforced polymer(CFRP) is the ideal material for the main cable of suspension bridge.In this paper, the feasibility of applying CFRP materials in the suspension bridges was proved and the applicable spans for the suspension bridges with CFRP cables were also provided.

Abstract: The choice of closure order of long span prestressed concrete continuous rigid frame bridge is the key part on its construction procedure, which has a big influence on the gross force and alignent of the whole structure. On the Basis of the Hanjiang bridge, the paper studies the closure order of long span prestressed concrete continuous rigid frame bridge and its system transformation procedure as well as the effect of jacking force etc. It shows that the technique of the midspan and the sidespan close at the same time not only meets the requirement of allowable internal force, but also has the benefit of shorten the construction period as well as reducing the degree of construction difficulty.