Study On Stability And Vibration Of Long Span Profiled Arch Bridge

The double X—arch bridge is a new type alienation arch bridge, which is developed on the basis of the X—arch bridge in past over 20 years. The double X—arch bridge, with novel, artistic and unique shape and wide bridge deck, is made up of four arch ribs which have two vertical arch ribs and two inclined arch ribs, and it is more competitive of wide city bridges. In this paper, the author choose a double X—arch bridge as an example which is a concrete-filled steel tube arch bridge to analyze the stability^ the dynamic performance and its influence factors, and the seismic response characteristics of such bridge. The author has made some main conclusions of this text, as follows:1) The results of stability analysis of double X—arch bridge:① When the ratio of rung spacing to main arch span is changed from 6/110 to 55/110, the safety factor of the arch bridge present a tendency of cubic parabolic reduced with the increase of the ratio of rung spacing to main arch span;② The rungs layout position show that:the arch near rungs has stronger impact on the arch stability safety factor than the rungs near L/3 and vault;③ When the camber angle of the auxiliary arch is between 18 and 27, the safety factor of the arch bridge shows a four parabolic trend increased with the increase of the inclination angele;④ When wide-to-span ratio is changed from 38.5/110 to 52.5/110, the safety factor of the arch bridge present a tendency of three parabolic reduced with the increase of the wide-to-span ratio;⑤ When the ratio of rise to span is changed from 1/7 to 1/4.5, the safety factor of the arch bridge present a tendency of cubic parabolic increased with the increase of the ratio of rise to span.2) The results of dynamic analyses of double X—arch bridge:① When the camber angle of the auxiliary arch is between 18 and 27, the arch rib’s auto-oscillated frequency out of plane increase obviously with the augmentation of the auxiliary arch rib’s sloping angle, however the change of the auxiliary arch rib’s sloping angle has little effect on the auto-oscillated frequency of plane and torsion;② When the ratio of rise to span is changed from 1/7 to 1/4.5, the arch rib’s auto-oscillated frequency plane、out of plane and torsion increase obviously with the decrease of the ratio of rise to span;③ With considering the effect of pile and soil, the arch rib’s auto-oscillated frequency is reduced. and the in-plane vibration mode of the arch rib’s is ahead of time, while the outer mode is relatively backward.3) The analyses of seismic response of the double X—arch bridge:① Displacement reponse results show that:under the combined E1-citations of the earthquakes in different directions, the transverse deformation changes maximum, the vertical deformation takes second place, and the longitudinal deformation changes minimum;② The results of axial force and shear force shows that:under the combined El-citations of the earthquakes in different directions, the axial forces and shear forces of main arch become the strongest at the abutment, meanwhile the axial forces and shear forces of main arch are under the control of seismic forces in the longitudinal direction;③ The results of bending moment:under the combined E1-citations of the earthquakes in different directions, In-plane bending moment will produce a small spike in L/8 span、in middle span and near 7L/8, and the Out of plane bending moment will produce the maximum in middle span. Besides middle span moment is controlled by seismic forces in the longitudinal+2/3 direction of the bridge, and the out of plane bending moment is controlled by seismic forces in the transverse direction of the bridge.