| Considering the shortcomings of the continuous girder bridges with single column pier usually used in city,2-span T-frame bridges are put forward in this paper,and the structural properties,static properties and dynamic properties of them are studied respectively.The main research work covers the following aspects:1.By comparing of structure construction,it can be known that the T-frame has little expansion at the terminal of the beam,which decreases the requirements of supports and expansion joints.2.By use of the static models of different systems,kinds of characters,such as longitudinal force,prestressed bars effect,longitudinal rigidity,transverse force and anti-overturning property are analyzed in this paper.And the results show that force conditions of the two systems are close,but the consolidation of pier and beam of T-frame can avoid the tendency of turnover due to the short space between the supports in continuous girder bridge.And compared with 3-span continuous girder bridge,2-span T-frame is more economical.3.Based on the simplified model,the analytical expressions of the force and moment of the pier produced by horizontal seismic wave are deduced for the two systems under the condition that the bottom of piers are fixed and the section of piers are unchanged along their heights.And the seismic responses of the two systems with different periods are analyzed in detail.The results demonstrated that:if T1<1.5Tg,the horizontal earthquake load of rigid piers H2 is less than that of fixed piers H1,if T1＞1.5Tg,the horizontal earthquake load of rigid piers H2 is more than that of fixed piers H1,the maximum ratio of the two is 1.633;while the bending movement at the bottom of rigid piers M2,which is caused by the horizontal earthquake load,is less than that of fixed piers M1 and the maximum ratio of the two is 0.816.4.By using the results of response spectrum analysis,the moment strength,shear strength and the ductility capacity of the piers are studied for different height,and the calculated results of the longitudinal bar ratio,stirrups ratio and displacement ductility ratio are presented.The results show that at the aspect of pier bending-resistant,piers of continuous girder bridge need more longitudinal bars than that of T-frame,at the aspect of pier shear-resistant,the stirrups of continuous girder bridge's piers are more in lower pier height,and less in higher height,and at the aspect of ductility,T-frame is also better than continuous girder bridge. 5.According to the elastic time history response analysis of two systems,it can be found that the effect tendency of pile-soil and the change tendency of structural internal force with the increasing of pier height are similar to the results of response spectrum analysis,and the values are near.6.The bearing capacity formulas of reinforced concrete eccentric compression member with elliptic section are derived.In summary,the general behaviors of T- frame bridges are better than that of continuous girder bridge.
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