Multimodal Response Spectrum Method Analysis of Integral Abutment Curved Box Girder Bridge
In order to simplify analysis of the dynamic characteristics and seismic response of the integral abutment curved box bridge(IACBB), automatic iteration of the multimode modal response spectrum(MMRS) is realized by APDL language of the structure analysis software ANSYS according to the IACBB's structural characteristics. The realization flow of iterative MMRS in Ansys were presented. and the availability and precision of the iterative MMRS were examined by the time-history analysis. The result shows that 1）the iterative MMRS is a efficient simplify method, and can be used as an estimating method of seismic analysis for the bridge. And the method provides a reference for future similar structures. 2）several conclusions of earthquake response are given. The research results are helpful for the knowledge of mechanics property of the type of the bridges.
STATE-OF-THE-ART OF INTEGRAL ABUTMENT BRIDGES: DESIGN AND PRACTICE
The superstructure for integral abutment bridges is cast integrally with abutments that are supported by a single row of piles. Thermal expansion or contraction and concrete creep and shrinkage induce bending stresses in the piles. Very limited design and construction guidelines are available and no unified design procedures exist nationwide; hence, there is a lack of enthusiasm to adopt integral abutment bridges for long spans. Current design and construction practices of integral abutment bridges have been reviewed. Important design parameters are identified with an emphasis on temperature, creep, and shrinkage effects of concrete bridge decks, varying soil strata, and the pile-soil interaction. A parametric study is described regarding the effects of a predrilled hole, the type of fill in the predrilled hole, elevation of the water table, soil type, and pile orientation. The results from the parametric study should aid in the selection and design of piles for integral abutment bridges.
Vertical Vibration of Floating Piles
An approximate analytical solution is presented for the vertical dynamic response of a floating pile. The dynamic stiffness and damping of the soil-pile system are also obtained. The results are compared with experiments. It appears that the motion of the tip cannot be neglected unless the pile is extremely long or the tip rests on rigid bedrock. The motion of the tip reduces the stiffness and increases the damping. With increasing length, the stiffness of a floating pile increases, while stiffness of an end bearing pile decreases. The damping of a floating pile is larger than that of an end bearing pile of equal length. Consequently, the dynamic response of a footing can be much smaller with floating piles than with end bearing piles. The relaxation of the tip improves the agreement between the theory and experiments.