Web Buckling & Crippling - Design of Steel Structures Questions and Answers

This set of Design of Steel Structures Multiple Choice Questions & Answers (MCQs) focuses on “Web Buckling & Crippling”.

1. Which of the following is correct?
a) web in rolled section behaves like a column when not placed under concentrated loads
b) web in rolled section behaves like a column when placed under concentrated loads
c) web in rolled section does not behave like a column when placed under concentrated loads
d) web in rolled section cannot be compared with column
View Answer

Answer: b
Explanation: The web in rolled section behaves like a column when placed under concentrated loads. The web is quite thin and is therefore, subjected to buckling.

2. The effective depth when top flanges are restrained against lateral deflection and rotation is
a) d/3
b) d
c) 2d
d) d/2
View Answer

Answer: d
Explanation: Bottom flange is assumed to be restrained against lateral deflection and rotation. for top flanges, the end restraints and effective depth of the web are to be considered. The effective depth when top flanges are restrained against lateral deflection and rotation is d/2, where d is depth of web.

3. The effective depth when top flanges are restrained against lateral deflection but not against rotation is
a) 2d/3
b) d
c) 2d
d) d/2
View Answer

Answer: a
Explanation: The effective depth when top flanges are restrained against lateral deflection but not against rotation is 2d/3, where d is depth of web. Bottom flange is assumed to be restrained against lateral deflection and rotation. for top flanges, the end restraints and effective depth of the web are to be considered.

4. The effective depth when top flanges are restrained against rotation but not against lateral deflection is
a) 2d/3
b) 2d
c) d
d) d/2
View Answer

Answer: c
Explanation: Bottom flange is assumed to be restrained against lateral deflection and rotation. for top flanges, the end restraints and effective depth of the web are to be considered. The effective depth when top flanges are restrained against rotation but not against lateral deflection is d, where d is depth of web.

5. The effective depth when top flanges are not restrained against rotation and lateral deflection is
a) 2d/3
b) 2d
c) d
d) d/2
View Answer

Answer: b
Explanation: The effective depth when top flanges are not restrained against rotation and lateral deflection is 2d, where d is depth of web. Bottom flange is assumed to be restrained against lateral deflection and rotation. for top flanges, the end restraints and effective depth of the web are to be considered.

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6. The maximum diagonal compression in plate girder simply supported occurs
a) does not occur
b) above neutral axis
c) below neutral axis
d) at neutral axis
View Answer

Answer: d
Explanation: The maximum diagonal compression in plate girder simply supported occurs at neutral axis . It will be inclined at 45˚ to the neutral axis.

7. Web buckling strength at support of simply supported plate girder is given by
a) F_wb =B_twf_cd
b) F_wb =t_wf_cd
c) F_wb =B_tw
d) F_wb =Bf_cd
View Answer

Answer: a
Explanation: Web buckling strength at support of simply supported plate girder is given by F_wb =B_twf_cd , where B is length of stiff portion of bearing plus additional length given by dispersion at 45˚to the level of neutral axis, t_w is thickness of web, f_cd is allowable compressive stress corresponding to assumed web strut according to buckling curve c.

8. Slenderness ratio when ends are assumed to be fixed for a plate girder is
a) 2.45 d
b) 8.5 d/t
c) 2.45 d/t
d) 8.5 t
View Answer

Answer: c
Explanation: When ends are assumed to be fixed, effective length = d√2/2 = d/√2, minimum radius of gyration = t/√12. Therefore slenderness ratio = (d/√2)/( t/√12) = 2.45d/t, where d = depth of web, t = thickness of web.

9. What is web crippling ?
a) web is of large thickness
b) flange near portion of stress concentration tends to fold over web
c) web near portion of stress concentration tends to fold over flange
d) flange is of large thickness
View Answer

Answer: c
Explanation: Webs of rolled section are subjected to large amount of stresses just below concentrated loads and above reactions from support. Stress concentration occurs at junction of web and flange. As a result, large bearing stresses are developed below concentrated load. Consequently, the web near portion of stress concentration tends to fold over flange. This type of local buckling phenomenon is called crippling or crimpling of web.

10. Which of the following is true?
a) web crippling is buckling of web caused by compressive force delivered through flange
b) web crippling is buckling of flange caused by compressive force delivered through web
c) web crippling is buckling of web caused by tensile force delivered through flange
d) web crippling is buckling of flange caused by tensile force delivered through web
View Answer

Answer: a
Explanation: Web crippling is buckling of web caused by compressive force delivered through flange. To keep bearing stresses within permissible limits, the concentrated load should be transferred from flanges to web on sufficiently large bearing areas.

11. The most critical location for failure due to web crippling is
a) flange cross section
b) middle of web
c) start of fillet
d) root of fillet
View Answer

Answer: d
Explanation: The most critical location for failure due to web crippling is root of fillet since resisting area has the smallest value here.

12. The angle of dispersion of load for web crippling is assumed to be
a) 2:1
b) 1:2.5
c) 4:5
d) 2:3
View Answer

Answer: b
Explanation: The angle of dispersion of load for web crippling is assumed to be 1:2.5 .With reference to this, bearing length is calculated.

13. The crippling strength of web at supports is given by
a) F_crip = (b+n₁)f_yw
b) F_crip = (b+n₁) t
c) F_crip = (b+n₁)/f_ywt
d) F_crip = (b+n₁)f_ywt
View Answer

Answer: d
Explanation: The crippling strength of web at supports is given by F_crip = (b+n₁)f_ywt, where b+n₁ is length obtained by dispersion through flange, t is thickness of web, f_yw is design yield strength of web.

14. The crippling strength of web at interior point where concentrated load is acting is given by
a) F_crip = (b+2n₁)f_yw
b) F_crip = (b+2n₁) t
c) F_crip = (b+2n₁)f_ywt
d) F_crip = (b+n₁)/f_ywt
View Answer

Answer: c
Explanation: The crippling strength of web at interior point where concentrated load is acting is given by F_crip = (b+2n₁)f_ywt, where b+2n₁ is length obtained by dispersion through flange, t is thickness of web, f_yw is design yield strength of web.

15. Which off the following will be a remedy to web crippling?
a) spreading load over small portion of flange
b) provide stiffeners which bear against flanges at load points
c) provide web of small thickness
d) web crippling cannot be prevented
View Answer

Answer: b
Explanation: Web crippling can be prevented by spreading load over large portion of flange. The other remedy is provide stiffeners which bear against flanges at load points and are connected to web to transfer force to it gradually. The other remedy is to make the web thicker.

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