Advanced Materials Research Vols. 255-260

Abstract: In order to mitigate the seismic response of twin-tower structure linked by a steel truss platform bridge, as well as to reduce temperature force in the steel truss, eight groups of combined isolation system, each consisting of one pot-type bearing and four rubber bearings, were designed to connect the upper platform bridge to the lower supporting reinforced concrete towers. The features and working principles of the high-position isolation system were described. Then the seismic responses, including displacement, story drift and floor acceleration, of the structure with the isolation systems were calculated and compared with those of the structure with hinge joints in lieu of isolation. It is found that both the structural seismic responses and the temperature forces in the large-span mega-truss structure can be reduced by the high-position isolation system.

Abstract: A static and dynamic load test is carried out on the constructed Hanjiang Super-major Railway Bridge in Laohekou to ensure the reliability of the bridge and test the carrying capacity and working condition of the bridge structure. The static load test is divided into three kinds of loading conditions, each of which tests the stress and deflection of the key sections of the bridge. The transverse vibration displacement of the piers and mid-span section is measured in the dynamic load test when the train is crossing the bridge at different speeds, and the vertical dynamic deflection of the mid-span section is also tested. The natural vibration frequency, the vibration types and the damping ratio of the whole bridge are measured in the pulsating experiment. Through the comparative analysis of the experimental results and the theoretical calculation results and standard, it can be concluded that the strength, the vertical and lateral stiffness of the bridge meet the requirements of both the design and specifications, and that the bridge is in a good working condition. The test and the analysis of the experimental results of the bridge can serve as a reference to the bridges of the same type.

Abstract: The webs of Continuous Rigid Frame Bridge suffer from cracking generally. In this paper, the mechanical characteristics of the box girder with cracked webs were studied. With reference of ChongQing JiangJin bridge, the 3-D solid FEM that employed with the smeared crack model was used to analysis the crack distribution. The law of reduced local stiffness and global stiffness on box girder with cracked sections was studied. At the same time, A sensitive analysis was performed to assess the effects of the effective prestress and reinforcement ratio on the cracking resistance and the reduced stiffness.

Abstract: Based on a nationwide survey and deck inspection in Michigan, the phenomenon of more severe corner cracking on skewed bridge decks was commonly observed. A series of FEA by DIANA were carried out to identify the possible causes and viable cures for such cracking. Prior to the FEA, the accuracy of FEM modeling was calibrated by two skew bridge decks instrumented using temperature and strain sensors for the deck concrete and the ambient environment. Test and FEA results found that the cracking has been mainly caused by thermal and shrinkage stress, and that possibly propagated and worsened by repetitive truck wheel loading. According to current Michigan practice of skew deck design and construction, additional reinforcement in the corner areas is therefore recommended to reduce concrete stresses. Further research is also recommended to develop solutions using optimal combinations of ingredients in concrete and to minimize the constraint between the deck and the supporting superstructure.

Abstract: Based on FEA for three bridge models with varying skew angles, the effect of skew angle on the design moment and shear of skewed bridge structures was studied and also compared to AASHTO specifications. The results show that, generally, ASSHTO-LFD covers FEM in moment distribution factor, but a little less in shear distribution factor, and that, however, AASHTO-LRFD reduces moment distribution factor below AASHTO-LFD and near to FEM, but increases shear distribution factor a lot beyond AASHTO-LFD and FEM.

Abstract: In order to study the impact of reforcement stress and concrete cracking of concrete bridge deck caused by the difference of reforcement diameter and spacing, the sub-model analysis was adopted, the bottom horizontal reforcement stress and concrete cracking affected by different diameter and spacing were analysised. The analysis results indicated that When the reforcement spacing was greater than 10cm, the concrete under the most unfavorable position of load would crack; in the vehicle the most unfavorable position, the concrete would crack; When the reinforcement specing was not more than 10cm, if the bar diameter was greater than a certain value, the concrete would not crack. Meanwhile, with the increase of reforcement diameter, steel stress decreased, the possibility of concrete cracking reduced. Combined with the analysis results, the reasonable diameter and spacing of underlying transverse reinforcement of concrete bridge deck were given, the diameter and spacing of other reinforcements of the bridge deck were recommended.

Abstract: Dynamics response of suspended cable structure is studied in this paper. It is difficult to analyze this type of structure because of non-linear behavior. VFIFE is an efficient method to solve non-linear problems and applied to calculate movement of cable on wide range. Some results are obtained from time history of cable vibration, such as galloping and characteristic frequency. A case of cable movement under wind shows that low frequency in wind speed is main fact impacting on wave of cable.

Abstract: This essay is to obtain the optimal parameter of building structure with turned mass damper(TMD)based on the constraint of comfort and power reliability under random wind loads. Firstly, the analytical solution for the acceleration of wind-induced response of the structure of the first-order model associated with the comfort r is got. Secondly, according to Extreme Value Theory of random process, the average maximum wind-induced displacement of the cont of the stucture with TMD or without TMD as the sign of the result of reducing vibaration.dntrolled structure is acquired. Thirdly, define the average ratio of the maxium wind-induced displacemeampers of the structure with TMD or without TMD as the index of the result or reducing vibaration. Finally, the improved genetic algorithm is used to gain the optimal parameters of TMD.Therefore, a general method for the optimal design of TMD dampers structure based on the constraint of comfort and dynamic reliability are established. The research studies have shown that the method can be used to obtain effectively the optimum parameters of TMD devices.

Abstract: A four span curved HcontinuousH HboxH-girder bridge is used as an engineering example to investigate the effect of radius of curvature on the seismic response of curved bridge. Numerical models with different radii of curvature are created using the finite element analysis program Midas/Civil. The calculation results obtained from response spectrum method show that radius of curvature is an important parameter to curved bridge. When the radius of curvature is large enough, the relationship between seismic response of main girder and radius is approximately linearity, while nonlinear variation is obtained when the radius is not too large. Finally, conclusions are made that seismic design of Hstraight bridgeH unHfoldHed from curved bridge which radius of curvature is specified could Hsatisfy the engineering Hrequirement.

Abstract: A new equivalent modulus of elasticity of stay cables is derived based on previous research works. The result of the proposed formula is close to Ernst’s formula and can be regarded as a theoretical supplement of existing works. Compared with the preset formula and other related works, Ernst’s formula is a proper choice for the equivalent modulus of elasticity of stay cables.