Test 32 - Steel Column Bases

Question 1 ప్రశ్న 1

Which statement correctly describes the present IS 800 design requirement for a structural-steel column base?

A It is required to transfer only axial compression and may ignore shear and moment B It should have sufficient stiffness and strength to transfer axial force, bending moment and shear to the foundation without exceeding the support capacity C Its design is governed only by the gross area of the steel column D It is designed only by the reinforced-concrete column provisions of IS 456

Question 2 ప్రశ్న 2

What is the principal structural function of a steel column base plate under axial compression?

A To concentrate the column load onto the smallest possible concrete area B To spread the concentrated steel-column force over a sufficiently large foundation area and provide the required load-transfer mechanism C To increase the yield stress of the column section D To prevent all possible column buckling without any other structural checks

Question 3 ప్రశ్న 3

According to IS 800:2007, what maximum nominal bearing pressure is permitted between a column base plate and the supporting concrete or bedding material?

A 0.25fck B 0.45fck C 0.60fck D 1.00fck

Question 4 ప్రశ్న 4

A steel column base bears on M30 concrete through bedding material having characteristic cube strength 25 MPa. What maximum nominal bearing pressure should be used according to IS 800:2007?

A 12 MPa B 15 MPa C 18 MPa D 25 MPa

Question 5 ప్రశ్న 5

A concentrically loaded column transmits a factored axial compression of 1800 kN. If the allowable nominal bearing pressure under the base plate is 15 N/mm^2, what minimum bearing area is required?

A 90000 mm^2 B 120000 mm^2 C 150000 mm^2 D 180000 mm^2

Question 6 ప్రశ్న 6

A column carries a factored axial compression of 2250 kN and the permissible nominal bearing pressure is 15 N/mm^2. Which is the smallest square base plate among the following that satisfies the bearing-area requirement?

A 350 mm × 350 mm B 375 mm × 375 mm C 400 mm × 400 mm D 450 mm × 450 mm

Question 7 ప్రశ్న 7

A steel column base carries a vertical compressive force of 1200 kN. Using the IS 800 steel-to-concrete or grout interface friction coefficient of 0.45 and assuming full compression contact, what horizontal shear could theoretically be resisted by friction alone?

A 270 kN B 450 kN C 540 kN D 1200 kN

Question 8 ప్రశ్న 8

When are anchor bolts or shear keys particularly relevant in the design of a steel column base?

A Only when the base carries perfectly concentric compression and no other force B Where necessary to resist actions such as uplift, significant horizontal shear or other forces not safely transferable through bearing and friction alone C Only to increase the compressive strength of concrete D They are prohibited when a base plate is used

Question 9 ప్రశ్న 9

How may the nominal bearing pressure beneath a steel column base plate be represented according to IS 800 when axial force and moment produce non-uniform compression?

A It must always be assumed uniform B It may be determined on the basis of a linearly varying pressure distribution C It must always be assumed parabolic D Bearing pressure is ignored whenever a bending moment exists

Question 10 ప్రశ్న 10

A rectangular base plate is 600 mm wide and 800 mm long in the direction of pressure variation. It carries P = 1200 kN and M = 80 kN·m about the centroidal axis parallel to the 600 mm side. Assuming full contact and linear pressure, what are qmax and qmin?

A 3.75 N/mm^2 and 1.25 N/mm^2 B 5.00 N/mm^2 and 0 N/mm^2 C 2.50 N/mm^2 and 2.50 N/mm^2 D 6.25 N/mm^2 and 1.25 N/mm^2

Question 11 ప్రశ్న 11

For the base plate in the previous question, the load eccentricity is e = M/P = 66.7 mm. The plate dimension in the direction of pressure variation is 800 mm. What does comparison with the middle-third limit show?

A Because e is greater than 400 mm, the whole base is in tension B Because e is less than 800/6 = 133.3 mm, the linear elastic pressure distribution remains compressive over the full base C Because e exceeds 800/12, the base automatically fails D The eccentricity has no influence on bearing pressure

Question 12 ప్రశ్న 12

If a simple full-contact linear-pressure calculation for a steel base gives a negative minimum bearing pressure, what is the correct engineering interpretation?

A Concrete beneath the plate is assumed to carry unlimited tension B The base should be analysed for partial compression contact and any required tension or uplift resistance through anchors and associated components C The negative pressure should simply be replaced by an equal positive pressure without further calculation D The column axial force may be ignored

Question 13 ప్రశ్న 13

Which statement correctly describes an IS 800 slab base?

A It must always contain gusset plates B It need not have gussets, but sufficient fastenings are required to secure the parts and resist moments and forces other than direct compression C It can transfer direct compression only and is not permitted to have fastenings D Its base plate has no structural bending action

Question 14 ప్రశ్న 14

A rectangular slab base is 540 mm × 440 mm and the rectangle circumscribing the column is 300 mm × 280 mm, concentrically positioned. What are the larger and smaller projections a and b used in the IS 800 slab-base thickness equation?

A a = 240 mm and b = 160 mm B a = 120 mm and b = 80 mm C a = 100 mm and b = 60 mm D a = 540 mm and b = 440 mm

Question 15 ప్రశ్న 15

Which expression gives the IS 800 minimum thickness ts of a rectangular slab base supporting a column under axial compression, where a is the larger projection and b the smaller projection?

A ts = sqrt[2.5w(a^2 - 0.3b^2)gamma_m0/fy], with the column-flange-thickness requirement also satisfied B ts = 2.5w(a + b)fy/gamma_m0 C ts = sqrt[fy/(2.5wab)] D ts = w(a^2 + b^2)gamma_m0

Question 16 ప్రశ్న 16

For a slab base, take w = 10 N/mm^2, a = 120 mm, b = 80 mm, fy = 250 MPa and gamma_m0 = 1.10. Using the IS 800 slab-base equation, what plate thickness is calculated before selecting a practical plate thickness?

A 27.0 mm B 31.6 mm C Approximately 37.1 mm D Approximately 45.8 mm

Question 17 ప్రశ్న 17

A 500 mm × 500 mm slab base carries a concentric factored axial load of 2000 kN. The circumscribing column rectangle is 300 mm × 300 mm, fy = 250 MPa and gamma_m0 = 1.10. What bearing pressure and calculated slab-base thickness are obtained?

A w = 4 N/mm^2 and ts = 17.6 mm B w = 8 N/mm^2 and ts = approximately 24.8 mm C w = 10 N/mm^2 and ts = approximately 31.6 mm D w = 16 N/mm^2 and ts = approximately 49.6 mm

Question 18 ప్రశ్న 18

When only the effective area of an oversized base plate is used in accordance with the IS 800 effective-projection concept, what substitution may be made in the slab-base thickness equation?

A The term a^2 - 0.3b^2 may be replaced by c^2 for the applicable equal effective projection c B The yield strength fy is replaced by the concrete strength fck C The bearing pressure w is taken as zero D The base-plate thickness becomes independent of its projection

Question 19 ప్రశ్న 19

Using the IS 800 effective-area form, take w = 9 N/mm^2, effective projection c = 90 mm, fy = 250 MPa and gamma_m0 = 1.10. What calculated base-plate thickness results from ts = sqrt[2.5wc^2gamma_m0/fy]?

A 18.9 mm B 22.5 mm C Approximately 28.3 mm D Approximately 40.5 mm

Question 20 ప్రశ్న 20

Which statement most accurately describes the structural action of an IS 800 gusseted column base?

A Only the base plate carries load and all gussets are decorative B Gusset plates, angle cleats, stiffeners and fastenings, together with the bearing area of the column shaft, are proportioned to transfer loads, moments and reactions to the base plate C A gusseted base cannot carry axial compression D Gusseted bases are designed without considering bearing

Question 21 ప్రశ్న 21

What does IS 800 require for the bearing surfaces of a gusseted base?

A They must intentionally be left uneven to develop friction B All bearing surfaces are to be machined to ensure proper contact C They are never permitted to contact the base plate D Only the anchor bolts are allowed to transfer compression

Question 22 ప్రశ్న 22

In a gusseted base, the ends of the column shaft and gusset plates are not faced for complete bearing. What is then required of the welds or fastenings connecting them to the base plate?

A They need carry only 10 percent of the column load B They must be sufficient to transmit all forces to which the base is subjected C They are required only during transportation and may be ignored in design D They need resist only the dead weight of the base plate

Question 23 ప్రశ్న 23

If the end of a steel column is connected directly to the base plate by full-penetration butt welds, how does IS 800 treat that connection?

A It is assumed to transfer compression only B It is deemed capable of transmitting to the base all forces and moments to which the column is subjected C It must always be supplemented by gusset angles before carrying any force D It is treated as having zero bending resistance

Question 24 ప్రశ్న 24

Which statement correctly describes the IS 800 machining requirements associated with a slab base?

A The underside of a base bearing on concrete must always be machined, irrespective of connection type B A base bearing on concrete need not be machined on its underside; where a cap or base is fillet welded directly to a column without boring and shouldering, the steel contact surfaces are machined for perfect bearing, whereas full-strength butt welds remove that contact-machining requirement C Neither bearing contact nor weld type has any influence on machining requirements D Full-strength butt welding requires more bearing-surface machining than fillet welding in every case

Question 25 ప్రశ్న 25

Which engineering-selection statement best distinguishes a slab base from a gusseted base without treating either choice as an absolute code rule?

A A simple slab base is commonly efficient for moderate predominantly axial loads, while a gusseted base can be advantageous for heavier load transfer or where a simple plate would otherwise become inefficiently large or thick B Gusseted bases are compulsory for every steel column C Slab bases may be used only for tension members D The choice of base type is unrelated to load magnitude, moment, fabrication or load-transfer requirements

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