New Monitoring and Assessment Method for the Joints of Steel and Concrete Connection in Large span Bridge

The joints of steel and concrete (JSC) is the key substructure to composite bridge, the method of condition monitoring and safety assessment were carried out for JSC with perfobond shear connectors (PBL) and local prestressed tendon in large span bridge. According to the damage mechanism of JSC, new monitoring parameters were proposed. The sensor location layout and the assessment thresholds of PBL were addressed with the consideration of the disadvantage influences of environment, load and concrete creep to local prestressed loss assessment and validated by the static load experiment. Compared the experimental results with field monitoring data, it was found that the new monitoring parameters and new assessment method were feasible and can be used as reference to the same type connectors in large span bridges.     

Nonlinear Analysis Technique of Refined Plastic-hinge Method for Steel Frame Structures

The refined plastic-hinge method is one of the simplified advanced analysis methods. The second order effects of the whole structure and its members, geometric imperfections and residual stress as well as the feature of semi-rigid connections can be taken into account in this method. The refined plastic-hinge method can be used in advanced analysis and design of planar steel frames, while its use in the advanced analysis of space frames needs to be developed. The technique associated with the dealing of different inelastic factors in advanced analysis of both the planar and space steel frames with practical refined plastic-hinge method and the available way to extend planar frame analysis to space frame analysis are reviewed in detail. The problems of the refined plastic-hinge method for advanced analysis are discussed in this paper.     

Appropriate Technology and Corresponding Design Strategies for the Steel Construction Congregated Apartments

In this paper,notions on appropriate technology for the Steel Construction Congregated Apartments are proposed in order to deal with the technical impediment that arises from applying steel structural techniques to the congregated apartments.The appropriate technology for the steel construction congregated apartments is defined as systematic technologies that are in harmony with the status quo of Chinese productive force level,social culture and building technology,and as the strategies of choosing or balancing technology according to sustainable development principle.The principal design and constructing strategies of appropriate technology are as follows:(1) organization of residential space combined with steel construction techniques,(2) suitable structural system,(3) a new idea of fire resistance,and(4) kit building technique etc.A technological concept analysis about an ideal model of a steel construction system congregated apartment combined with the appropriate technology is also presented.     

Mechanical Behavior of Bolt weld Joints between Square Concrete filled Tubular Column and Reduced Beam Section

With the actual three dimension element, the nonlinear finite element analytic models were established for bolt weld joints between square concrete filled tubular (CFT) column and reduced beam section with inner separates, considering geometric large deformation, materials nonlinear and contact nonlinear. Compared with finite element model and experimental model, it was in good agreement in principle. And the characteristics of load displacement(P Δ) curves, the stresses distribution of beam, the dissipating energy ability and destruction form were made with numerical analysis for bearing behavior of bolt weld joints between square CFT column and reduced beam section . It was shown that the initial stiffness of joint with reduced beam section was close to that of non reduced beam section joint. The bearing capacities of joints with reduced beam section were a little bit lower than those of non reduced beam section joint. The plastic hinge in the joint with reduced beam section moved to the reduced beam region. The studied joints displayed a better ductility, energy dissipation and good seismic behavior.     

Comparison on Shrinkage Effects at Concrete Interfaces in Long Span Girder Bridges between Chinese and American Codes

Stress, due to shrinkage characteristic difference resulting from different concrete age at typical interface parts in long span rigid frame bridges, was analyzed based on Chinese and American codes. Reasons for large discrepancy between results under the two codes were also discussed. It was shown that shrinkage stress level calculated under AASHTO was more reasonable than that under Chinese code (JTGD 622004) for concrete members with large thickness. Concrete at interface parts was easy to crack when casting time interval was long. According to JTGD 622004, stress at interfaces was always small under different casting time intervals, while stress at position with mutation section was more significant. It was necessary to set an upper limit to theoretical thickness in JTGD 622004, and 300 mm was recommended. Finally, some design and construction approaches were put forward.     

Determination Method and Criterion for Voids by Dynamic Deflection Difference in the Same Cement Slab

Aiming at the lack of the current determination method for voids in practical engineering applications, in order to accurately quantify the voids beneath cement slab, the determination method was proposed with slab edge slab center deflection difference and slab corner slab center deflection difference in the same cement slab for voids.Three dimensional models were set up using the ANSYS finite element method for voids beneath slab corner and slab edge.And the load was simulated with FWD test results.Thereafter, the deflection values were calculated in slab center, slab corner, slab edge under different void depth, void area and load transfer capacity.And the range of deflection diffidence was obtained.With Yantai Weihai expressway, detection data for deflection using Falling Weight Deflectometer were statistically analyzed.And the criteria and correction factors of load transfer capacity were given with simulation and samples analysis.The feasibility of criteria was verified by actual test data.It is found that the simulation values and the test values are in good agreement.The accuracy of void determination by lab edge slab center deflection difference and slab corner slab center deflection difference are 88.5% and 84.6%, respectively, which meet the engineering requirements.The voids were determined under the same conditions with the elimination of deflection variability.