EN1993-2: Design of Steel Structures - Steel Bridges

[Ally_S]

Hi

I am currently working through the Appendices within Eurocode 3:Steel Bridges. I am calculating the out of plane buckling factors for a tied arch with vertical hangers. Within Table D.1 the ratio of h/hr (height of end portal to average hanger height) buckling curves varies from -2 to +2. I am unsure to how the ratio can become negative? I am inclined to think that one h< hr (as shown in diagrammatic representation) is a positive ratio; when the height of end portal h> hr then that would signify a negative ratio inferring that as the height of portal is much greater than the hangers this will increase the instability? Essentially, what signifies a negative h/hr ratio?

 

[HTURKAK]

Look for the definition of hr

D.3.4 Out of plane buckling of arches with wind bracing and end portals,

(3) The value hr in Table D.1 may be taken as the mean of all lengths multiplied by 1/SIN αk

and sin α will be positive or negative acc. to position of deck relative to the support level ..

Pls look Figure D.5: Buckling of portals for arches