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The correct answer is (b) slender sections are preferred in hot rolled structural steelwork

The best I can explain: Only PLASTIC SECTION can be used in intermediate frames which form collapse mechanism. Compact sections can be used in simply supported beams which fail after reaching Mp at one section. Semi-compact sections can be used for elastic designs where section fails after reaching My at EXTREME fibres. Slender sections are not preferred in hot rolled structural steelwork, but they are extensively used in COLD formed members.

The CORRECT option is (d) in case of rolled section, high THICKNESS of plate is adopted to PREVENT local buckling

For explanation: In case of rolled section, higher thickness of plate is adopted to prevent local buckling. Local buckling cannot be prevented by limiting width-thickness RATIO. For built-up section and cold formed section, longitudinal stiffeners are PROVIDED to reduce width to smaller sizes.

Correct OPTION is (c) changing material

The best explanation: Local BUCKLING of compression members of beam causes loss of INTEGRITY of beam cross SECTION. It is a function of width-thickness RATIO and can be prevented by limiting width-thickness ratio.

The CORRECT answer is (a) Angles and T section are strong in bending

The best explanation: Angles and T section are WEAK in bending. CHANNELS can be used only for light loads. I sections (rolled and built-up) are most efficient and economical shapes. I section with cover plates are provided when large section MODULUS is required. Generally, ISLB or ISMB are provided in such CASES.

Right choice is (c) loading plane coincides with one of the principal planes of doubly symmetric section

To EXPLAIN I would say: Simple bending takes place if loading plane coincides with one of the principal planes of doubly symmetric section such as I-section or in case of singly symmetric OPEN section such as channel section, the loading passes through SHEAR centre and is parallel to the principal plane. Unsymmetrical bending OCCURS if loading does not PASS through shear centre.

Right ANSWER is (a) loads are inclined to principal axes

For explanation I WOULD say: Complex stresses may arise when loads are inclined to principal axes, when UNSYMMETRICAL SECTIONS are used or when large values of shear and bending moment OCCUR at section.

Right option is (c) BEAMS are TERMED as fixed beams when ends are rigidly connected to other members

The explanation: Beams may be termed as simply supported beams when end condition do not carry any end moments from any continuity DEVELOPED by connection.A beam is called continuous beam when it extends CONTINUOUSLY across more than two SUPPORTS. A fixed beam has its ends rigidly connected to other members, so that moments can be carried across the connection.

The correct ANSWER is (b) stringers

For explanation I would say: Stringers are members used in bridges PARALLEL to traffic to carry the deck SLAB. They will be connected by transverse floor BEAMS.

Correct answer is (a) EXTERIOR BEAMS at floor LEVEL of buildings

Best EXPLANATION: Spandrels are exterior beams at floor level of buildings, which carry PART of floor load and exterior wall.

Correct option is (c) BENDING and shear

Explanation: The LOAD TRANSFER by BEAM is primarily by bending and shear. The MODE of deflection of beam is primarily by bending.

Right OPTION is (d) lintels

Best EXPLANATION: Lintels are beam members used to CARRY wall loads over wall openings for doors, windows, etc.

Correct OPTION is (C) beam-COLUMN

To elaborate: Structural members subjected to bending accompanied by large axial compressive loadsat the same time are known as beam-column. A beam-column differs from column only by presence of eccentricity of load application, END moment, TRANSVERSE load.

Right answer is (b) horizontal BEAM spanning between WALL column of industrial buildings

Easiest explanation: Girt is horizontal member FASTENED to and spanning between peripheral column of industrial buildings. It is used to support wall cladding such as corrugated METAL sheet.

Correct CHOICE is (c) Z = M/(1.33×0.66xfy)

The EXPLANATION is: The modulus of SECTION required for angle section purlin is given by Z = M/(1.33×0.66xfy), M = maximum bending moment = wl^2/10, w = unfactored uniformly distributed load, l = span of purlin, fy is yield stress. The gravity and wind LOADS are determined to calculate bending moment and both loads are assumed to be normal to roof TRUSS.

The correct choice is (a) 25˚

For explanation I would say: Angle sections are unsymmetrical about both the axes. Angle sections can be used as purlin SECTION. provided SLOPE of the ROOF TRUSS is less than 30˚.

Correct option is (b) (Mz/Mdz) + (My/Mdy) ≤ 1

To EXPLAIN I WOULD say: The local capacity of the SECTION is checked by interaction equation. It is given by (Mz/Mdz) + (My/Mdy) ≤ 1 , where Mdz and Mdy are design moment capacity about Z and Y AXES, respectively, and Mz and My are factored bending moments about Z and Y axes, respectively.

Correct option is (d) Mdz ≤ 1.2Zezfy/γm0, MDY ≤ γfZeyfy/γm0

Easy explanation: The CHECK for design capacity of channel/I-section purlin is GIVEN by Mdz ≤ 1.2Zezfy/γm0 , Mdy ≤ γyZeyfy/γm0 , where Mdz and Mdy are design moment capacity about Z and Y axes, respectively, Zez and Zeyare elastic section modulus about Z and Y axes, respectively and fy is yield stress of steel. Since in y-direction, the SHAPE factor Zp/Ze will be greater than 1.2, γf is used instead of 1.2. If 1.2 is used the onset of YIELDING under unfactored loads cannot be prevented.

The correct choice is (c) these RODS increase the momentMyy

To EXPLAIN I WOULD say: Sag rods are provided midway or at one-third points between roof trusses to take up the sag in the direction of sloping roof by purlins. These rods provide lateral support with resprct to y-axis bending. Consequently, moment Myy is reduced and thereby RESULT in smaller purlin section. they are useful in keeping the purlins in PROPER alignment during erection until roofing is installed and connected to purlins.

The correct choice is (b) M = Zpγm0fy

To explain: The design capacity of channel/I-section purlin is given by Mdz = Zpzγm0/fy and Mdy = Zpyγm0/fy , Mdz and Mdy are design moment capacity about Z and Y axes, respectively, Zpz and Zpyare plastic section modulus about Z and Y axes, respectively and fy is yield stress of STEEL. For SAFETY, design moment capacity should be ALWAYS GREATER than or equal to factored bending MOMENTS.

The CORRECT option is (a) one-third points between roof trusses

Easiest explanation: PURLIN sections have tendency to sag in the direction of SLOPING roof . So, sag rods are PROVIDED midway or at one-third points between roof trusses to TAKE up the sag.

Right option is (d) REDUCES by 75%

To elaborate: If sag rods are not used, the maximum MOMENT about web AXIS would be wl2/8. When one sag rod is used, the MOMENTS are reduced by 75% and when TWO sag rods are used at one-third points, the moments are reduced by 91%.

Correct choice is (a) Wl/10, where W= concentrated load

The best explanation: The gravity load, P1 and load DUE to wind component, H1 are computed. The loads are multiplied by load factors. Thus, P = γfP1, H = γfH1 . The maximum bending MOMENT are calculated as Mz = Pl/10 and My = Hl/10, where P= factored load along z-axis, H = factored load along y-axis, l= span of purlin (c/c distance between adjacent trusses).

The correct answer is (d) wl^2/8

Easy explanation: Purlins can be DESIGNED simple, continuous or cantilever BEAMS. If purlins are assumed to be SIMPLY supported, the moments will be wl^2/8. If they are assumed to be continuous, the moments will be slightly less and taken as wl2/10. IS 800 recommends the purlins to be designed as continuous beams.

Correct answer is (b) FACING up slope

To explain I WOULD say: While erecting angle, CHANNEL or I- section purlins, it is desirable that they are erected over rafter with their flange facing up slope. In this POSITION, the TWISTING moment does not cause any instability. The twisting moment will cause instability if the purlins are kept in such a way that the flanges face the downward slope.

Right option is (a) only at panel points

The BEST I can explain: Theoretically, it is DESIRABLE to place PURLINS only at panel points. They are placed at panel points to AVOID bending in the top chords of roof trusses. For large trusses, it is more economical to SPACE purlins at closer intervals.

The correct option is (c) beams provided over trusses to support roofing

Easiest explanation: Purlins are beams provided over trusses to support SLOPING roof system between adjacent trusses. CHANNELS, angle sections, and old FORMED Z-sections are WIDELY used as purlins.

The CORRECT option is (a) rectangular load

To explain: When the slab over lintel is below APEX of equilateral triangle formed on lintel, the load of MASONRY in the rectangle is considered. The load of masonry in the rectangle is assumed to act over by taking length equal to span of lintel and HEIGHT equal to CLEAR height of slab above the lintel.

Correct choice is (b) triangular load

For explanation: When the slab over LINTEL is above apex of equilateral triangle formed on lintel, the load of MASONRY in the triangle thus formed is ASSUMED to act over it. When the design load is from triangular portion of masonry , the maximum moment will beWl/6, where W =triangular load from masonry and L = effective span of lintel.

Correct ANSWER is (a) when more span to be covered than rolled section

Easy explanation: The section of castellated beam will have more depth and section modulus than original rolled section. This allows the beam to span further than parent rolled section. Castellated beams may not be desirable when beam is SUBJECTED to substantial concentrated loads, or when castellated beam is used as a continuous beam across several supports. Castellated beams are LESS attractive when very high requirements for fire resistance are required because the fire resistant coating has to be around 20% thicker than for rolled SECTIONS in order to obtain the same fire resistance as rolled section.

Correct answer is (d) beams above openings in wall

To explain: Beams provided above the openings in WALLS to support masonry that comes in between the opening and slab above are called as LINTELS. It is DESIRABLE that LINTEL is built flush from both the sides of the walls.

Right option is (b) openings can be made close to neutral axis

Explanation: Shear CAPACITY of castellated beams can be improved by making openings close to neutral axis and making cuts in a wavy manner. Stiffening can be PROVIDED at LOAD concentrations and reaction points to improve its shear CARRYING capacity.

Right choice is (d) high fire RESISTANCE than original rolled section

Explanation: CASTELLATED beams are LIGHT in weight, cheaper, they have relatively high resistance and can be assembled fast at the construction site. They are less fire resistant than NORMAL rolled sections. Castellated beams can very easily be CAMBERED and cranked.

The CORRECT answer is (d) reduced

Explanation: CASTELLATED beams have reduced SHEAR capacity. It has reduced shear capacity due to stress concentrations near the OPENINGS.

Correct answer is (a) 50% more than ORIGINAL section

To explain: The new rolled section of castellated BEAM will have depth at least50% more and its section modulus increases by 2.25 times the original section. This ALLOWS the beam to span further than PARENT rolled section.

Correct answer is (c) beam with number of regular openings in WEB

Easy explanation: A beam with number of regular openings in its web is CALLED castellated beam. A castellated beam is formed by flame cutting a single ROLLED wide FLANGE beam in a definite predetermined pattern and then rejoining the segments by WELDING to form a regular pattern of holes in the web.

Right option is (C) both moment and shear

Explanation: The STRENGTH of the beams with openings may be GOVERNED by plastic DEFORMATIONS due to both moment and shear at the openings. The strength realised will depend upon the INTERACTION between moment and shear. The reduction in moment capacity at the openings is small while the reduction in shear capacity may be significant.

The correct CHOICE is (d) low SHEAR, low bending moment

To explain: Holes in beam WEBS have less effect on flexural strength than holes in the FLANGES. Holes in beam webs should be placed only at sections of low shear. In the flanges, the holes should be cut at points of low bending moment. If this is not possible, the effect of the holes should be accounted for design.

Correct answer is (c) height/400

For explanation I would say: The maximum LATERAL deflection of column/frame in industrial buildings SUBJECTED to CRANE load plus WIND load and for brittle cladding (pendant operated)is height/400 and for ELASTIC cladding (cab operated) is height/200.

Correct choice is (a) increase in stress

To explain: A hole in flange of beam causes an increase in stress. If the hole in COMPRESSION flange CONTAINS rivet or bolt, the strength REDUCTION is LESSENED as fastener can transmit compression.

The correct answer is (a) span/150

Best EXPLANATION: The maximum vertical deflection for a cantilever member in other BUILDINGS (other than industrial buildings) subjected to LIVE LOAD and elements not susceptible to cracking is span/150 and for elements susceptible to cracking is span/180.

Right option is (d) height/500

Easiest explanation: The maximum lateral deflection in other buildings (other than industrial buildings) subjected to wind LOAD and for BRITTLE cladding is height /500 and for ELASTIC cladding is height/300.

Correct answer is (b) span/360

To explain I would say: The MAXIMUM deflection in other buildings (other than industrial buildings) for floor subjected to LIVE load and ELEMENTS SUSCEPTIBLE to cracking is span/360.

The correct choice is (b) span

The best explanation: BEAM deflection is a function of loading, span, modulus of elasticity and geometry of cross SECTION. Small deflections of beams do not cause structural problems in general except for DISCOMFORT to the users. But excessive deflections may LEAD to crack in plaster or ceilings and may damage material attached to or supported by beams.