Test: Steel Design- 1 - SSC JE MCQ

A joint in the web plate provided to increase its length is known as web splice. The plates are manufactured up to a limited length. When the maximum manufactured length of the plate is insufficient for full length of the plate girder, web splice becomes essential. They are mainly used in Bridges. Splices in the web of the plate girder are designed to resist the shear and moment at the spliced section. The splice plates are provided on each side of the web.

Polar section of modulus (Z_p) is high for hollow sections and Box type sections is a type of hollow section, that’s why it is used at a location where torsion occurs.

As per IS 800 : 2007, Effective length of a fillet weld should not be less than four times the weld size.

As per IS 875, the design wind speed at any height z is given by:

Where,

V_b = Basic Maximum wind speed

K₁ = Probability factor or risk coefficient

K₂ = Terrain, height and structure size factor

K₃ = topography factor

Risk coefficient is dependent on:

a) Mean probable design life of structures

b) Basic wind speed

Example: For Important buildings and structures such as hospitals, communication buildings/towers for 100 years of design life of structure and wind speed of 33 m/s, Risk coefficient is 1.05.

Minimum Spacing of vertical Stiffeners = 0.33 d

Maximum Spacing of vertical Stiffeners = 1.5 d

Where d = clear depth of web between flange angles.

Connection such as riveted, bolted and welded can be design as flexible, semi-rigid or rigid connections. Flexible connections are known as simple connections. Rigid design is done to resist both shear and bending moment at the connections whereas Semi rigid connections resist the bending moment in between flexible and rigid connections. While Plastic design method does not take into consideration the effect of impact, fatigue, creep and shrinkage etc.

Maximum allowable tensile strength = 

Reduction in the allowable stress in steel chimney Construction is necessary if the temperature exceeds 100°C

Angle sections are more resistant towards buckling than plate sections. Connections between angles are simple, and fabricated with ease, whether they’re bolted or welded. Angles offer a wide range of variety as you can use them singly, back to back and star shaped.

It is quite possible for a truss to experience ever changing loading in terms of both magnitude and directions. Under any given loading condition, a set of truss members remain in compression while others remain in tension. For one loading condition, a group of truss members remain loaded in compression while for a different loading condition, a different set of truss members remain loaded in compression. Although plate members perform very efficiently in tension, but they perform poorly under compression as they buckle under insignificant load (reason: very small radius of gyration). So, in place of plate members angle section members are used which can significantly resist buckling in comparison to their plate counterparts. (reason: large radius of gyration). For the above two reasons, angle sections are used in steel trusses so that when applied load reverses its direction and causes the tension members turn into compression members, the new set of compresses members don’t fail by buckling and cause catastrophic failure of the structure.

Four angle sections are used in Compression members.

The rolled steel beams are designated by the series to which beam sections belong (abbreviated reference symbols), followed by depth in mm of the section and weight in kN per metre length of the beam, e.g., MB 225 @ 0.312 kN/m.

As per IS 808:1989, Hot rolled I sections are classified in to 5 series:

i) Indian Standard Joist/junior Beams (ISJB)

ii) Indian Standard Light Beams (ISLB)

iii) Indian Standard Medium Weight Beams (ISMB)

iv) Indian Standard Wide Flange Beams (ISWB)

v) Indian Standard Heavy Beam (ISHB)

Young's modulus of steel is approximately three times as that of aluminium, that's why its strength to unit weight ratio is high. In situations where high deformations are not acceptable aluminium can't be used. Aluminium is increasingly used for structural purpose because it requires less maintenance. The biggest disadvantage of aluminium is that the deformations are high for a given load and it is costlier than mild steel.

As per IS 800 Design specifications are:

1. The angle of inclination of the lacing with the longitudinal axis of the column should be between 40° to 70°.

2. The slenderness ratio of the lacing bar should not exceed 145.

3. Minimum width of lacing in riveted connections should be:

Which is approximated to 3 times the nominal diameter.

For Bolted or welded lacing system, L/r_min ≤ 50 or ≤ 0.7 times KL/r of the member as a whole, whichever is less.

Where r_min = minimum radius of gyration of the components of the compression member.

In case of standard bolts of diameter ‘d’, the cross sectional area at the thread is approximately taken as 78% of the gross area i.e. 

According to IS: 800 (2007), in an industrial building with brittle cladding, vertical deflection of beams should not exceed  for elastic cladding it should not exceed 

Correct Answer :- b

Explanation : Filler plates are used when two column sections having unequal sections. In above condition just milled ends are provided.

Spandrel beam: Supporting load from exterior wall and slab and spanning from column to column.

In the case of high rise buildings, the masonry walls are usually not able to withstand their self-weight and the slab weight. In such cases, the beams are provided with exterior walls at each floor level to support the wall load and perhaps some roof load also. These beams are termed as spandrels.

Stringer beams: These are secondary beams (typically used in truss bridges) to carry the load from the slab till the cross beams located at truss nodes. You can see them in roof systems supported by trusses too. Basically, their purpose is to convert distributed loads to point loads (at truss nodes).