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Figure 5.36. Criteria for ignoring second order effects in beams according to ENV and EN in comparison with numerical results [7]

Figure 5.36. Criteria for ignoring second order effects in beams according to ENV and EN in comparison with numerical results [7]

In the final version, a distinction between persistent and transient design situations has been introduced, together with an additional criterion for h/b; this is based on national comments.

5.10 Prestressed members and structures

See example 6.15

5.11 Analysis for some particular structural members

No specific comment on this part.

Appendix 1. Verification of new model for slenderness limit Variables covered:

Concrete grade: C20, C40, C80

Reinforcement ratio: ro = 0,1 and 0,5 (for C40 also ro = 0,3) Effective creep ratio: yef = 0 and 2 (for C40 and ro = 0,3 also yef = 1)

Explanations to diagrams:

Horizontal axis: relative normal force n

Vertical axis: slenderness limit Alim

Full curves: 10%-criterion, alternative 1

Dashed curves: 10%-criterion, alternative 2

Thick grey curves: new proposal for slenderness limit

Concrete C20

Concrete C40

Concrete C80

Appendix 2. Calibration of simplified methods A2.1 Main calculations and results

Calculations have been made for isolated columns with the following variables:

| Cross section

Rectangular1

Reinforcement

Symmetrical, concentrated to tensiLe and compressive edges, edge distance 0,1ft

First order moment:

Constant (equal end eccentricities)6

Boundary conditions

Pin-ended

ilendemess ratio  = ¡0 / i

(0) 35 70 105 140

Relative eccentricity ey'h

(0) 0.1 0.2 0.4 0.6 0,8 1.2 \.l 3.0 6,0

Reinforcement ratio û) = AJy^A^i

0 0

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