Aiming at the fact that BJ Bridge is a four-line high-speed railway cable-stayed bridge which is restricted by the construction conditions, only two main trusses can be arranged, two orthotropic plate monolithic floor systems were presented: A1 (full width monolithic floor system) and A2 (reduced width monolithic floor system with two main trusses, side stringer and horizontA1 K-shaped brace). Using finite element method, the verticA1 stiffness of the bridge, the level of the floor system working together with the main trusses and the relative deformation between the two trucks of one line within 3 m were studied. The ratios of deflection to span of A1 and A2 under the worst-case load are 1/1060 and 1/1082 respectively. The orthotropic plate monolithic floor system contributes a lot to the stiffness of the main truss of cable-stayed bridge. Under the action of live load, A1 and A2 increase 88% and 114% of the stiffness of the lower chords respectively, or 29% and 34% of the stiffness of the main trusses, respectively. The relative deformations between the two trucks of one line of A1 and A2 are A1l less than 0.25 mm, and A2 is smA1ler than A1 for 30%-40%, and the maximum vA1ue appears at the locations of 1/4 and 3/4 of one panel.%针对BJ桥属四线高速铁路专用斜拉桥、建桥条件受限制,只能采用两主桁结构的问题,提出2种正交异性板整体桥面系方案:全宽整体桥面结构(A1)和两主桁+边纵梁+水平K撑的减宽整体桥面结构(A2).采用空间有限元方法,对桥梁整体竖向刚度、桥面系参与主桁共同作用的程度、同一线两根轨道3m内相对变形量等进行对比研究.结果表明:最不利活载作用下方案A1和方案A2主跨的挠跨比分别为1/1 060和1/1 082;正交异性整体桥面对斜拉桥主桁刚度的贡献相当大,活载作用下,方案A1和方案A2相当于把主桁下弦杆刚度分别增大88％和114％,或把整个主桁刚度增大29％和34％.同一线两根轨道的相对变形量在节间1/4和3/4处达到最大值；方案A1和方案A2同一线两根轨道的相对变形量均小于0.25 mm,但方案A2比方案A1小30％～40％.
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