关键词: 混凝土结构, 压力线, 轴线, 吻合, 压力线包络图, 八字型刚架拱桥

Abstract: It?is?well?acknowledged?that?the?rationality?of?force?of?arch?ring?can?be?measured?by?the?level?of?concord?between?the?pressure?line?and?arch?axis?concerning?traditional?concrete?arch?bridges.?So?this?concept?is?further?applied?to?all?concrete?structures?like?concrete?beam?bridges?（bending?members）,?multi-line?rigid?frame?bridges?（compression-flexure?members）,?and?soon.?It?is?proved?that?on?the?premise?of?proper?prestress?to?all?concrete?structures,?the?extent?of?eccentricity?of?pressure?line?and?axis?can?always?be?brought?under?control?so?as?to?make?full?section?compressed.?On?this?basis,?an?advantageous?kind?of?eight-shaped?prestressed?concrete?rigid-frame?arch?bridge?is?created?under?certain?circumstance,?and?its?control?area?of?enveloping?curve?of?line?of?pressure?also?applicable?to?all?concrete?structures?is?deduced?to?be?-Ks≤E≤Kx.

Key words: concrete structure , pressure line , axis , concord , enveloping curve of line of pressure , eigh-shaped rigid-frame arch bridge ;