undefined | unit 5 design strength using shear moment interaction

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Unit – 5

Design strength using shear-moment interaction

Q1) Write a short note on moment interaction.

A1) The moment interaction diagram is created for a specific axial force, and is used to show the interaction of the applied moments compared to the moment interaction failure envelope.

The resultant moment angle (both applied and resistance) and neutral axis angle are then measured anti-clockwise from this zero position.

Q2) What is Built up beams?

A2)

A built-up beam is likewise referred to as compound beam.

The built-up beams are used whilst the span, load and corresponding bending second are of such magnitudes that rolled metal beam segment will become insufficient to offer required segment modulus.

Built-up beams also are used whilst rolled metal beams are insufficient for restricted intensity.

In constructing construction, the intensity of beam is restricted with the aid of using an area furnished with the aid of using the architect.

Q3) Give design procedure for built up beams.

A3) Here are the simple steps that are to be followed for the design of Built-up Beams.

Step one

The effective span and load required to be carried by the built-up beam are known.

Maximum bending moment and shear force in built-up beams are calculated.

Step two

Value of yield stress (fy) for structural steel is to be assumed.

The permissible bending stress (sigma bc) is calculated.

Step three

The required section modulus (Z) for the given beam section is calculated.

Step four

From the steel table, a trial section for a beam is adopted having the modulus of section (Z) about 25% to 50% in excess of that requirement. The geometrical proportion of beam sections are noted.

Step five

When the depth of the beam is noted, then the usually the practice is to select from ISI handbook No.1 (Steel tables).

The strongest Rolled steel beam that will allow for necessary thickness of power plates at top and bottom.

Step six

The area of power plate required is found out by trial-and-error method are by;

I = Ibeam + 2(Ap)(h/2) (h/2)

For finding the area, divide the whole equation by h/2.

Step seven

Width of cover plate and thickness are decided with the restriction of outstands.

Step Eight

Check for bending stress/Actual bending compressive stress

(Sigma bc) calculated = (maximum bending moment/Gross MI) x Distance of extreme fibre in compression from Neutral Axis= (M/Ixx) x y1

Actual bending tension stress sigma bt, cal = (sigma bc) cal x (gross area of tension flange/Net area of tension flange) = Value should not exceed the permissible bending stress (sigma bc) or (sigma bt) = 0/66fy

Step nine

Check for shear and Deflection

Q4) What is meant by shear strength?

A4)

In engineering, shear strength is the strength of a material or component against the type of yield or structural failure when the material or component fails in shear.

A shear load is a force that tends to produce a sliding failure on a material along a plane that is parallel to the direction of the force. When a paper is cut with scissors, the paper fails in shear.

In structural and mechanical engineering, the shear strength of a component is important for designing the dimensions and materials to be used for the manufacture or construction of the component (e.g., beams, plates, or bolts).

Q5) Write a short note on plate girders.

A5) A plate girder is a metal beam this is broadly utilized in bridge production. Depending at the layout necessities and as according to the character of the structure; steel thicknesses for internet, flanges, stiffness, and many others are decided.

The use of the right cloth (metal) having the desired electricity and doing the welding are the 2 major elements to be attended to while growing the plate girder.

Types of Plate Girders

There may be exclusive classifications relying at the requirements used or relying on the character of the manufacturing of the girders.

There varieties of plate girders.

1. Reverted Plate Girder

2. Welded Plate Girder

Q6) What Is Riveted type plate girder?

A6) It is an aggregate of flanges, internet, and different vital stiffness. There are related via way of means of a mechanical method, revert, and plates aren't welded collectively.

Generally, 90% of the shear is carried via way of means of the internet.

Connection of the internet and the flange is stabilized via way of means of the angel sections reverted to the flange. Reverts want to be designed for the horizontal shear.

Angle sections are used as internet stiffness in revert girders.

Q7) What is welded plate girder?

A7)

Welded plate girders are maximum broadly utilized in production because of the convenience of manufacturing and its miles a far extra green sort of girder.

These sections are specifically utilized in bridge production. The plate girder bridge could be very stiff and it is able to retain very excessive hundreds even as resisting the lateral movements.

There are empirical or approximation strategies to decide the general peak of the plate girder and thickness of the flange and internet.

Q8) Enlist the parts of plate girder.

A8)

Web Plate

Flange

Stiffeners (bearing, longitudinal, and intermediate)

Splices for flange and internet

End Connection

Q9) Write a short note on Web plate.

A9) The vertical plate of the girder is called the internet plate.

Its thickness is primarily based totally at the layout necessities and the peak can also be determined primarily based totally at the web page condition and as according to the hundreds carried out at the internet.

The internet typically includes the carried-out hundreds at the flange as shear forces. The impact of the internet isn't always usually taken into consideration while the layout for the bending.

Q10) Define stiffeners and their types.

A10) Stiffeners are furnished to enhance structural potential heading off the nearby buckling failures. In addition, they may be used to hold the hundreds carried out to the beam till it allotted into the beam.

The following varieties of stiffeners can be found in those varieties of metal elements.

Bearing stiffeners

Longitudinal stiffeners

Intermediate stiffeners

Q11) What are the Applications of plate girder?

A11)

In addition, field girder bridges, beam bridges, navy girder composite bridges, and half – thru plate girder bridges are taken into consideration because it uses.

Ships

Gantry beams

Oil and fueloline platforms

Load testing

Cranes

Lifting systems

Q12) What are the advantage of plate girder?

A12)

They may be used to hold heavy hundreds

Speed production

Grater balance

High resistance to fatigue failures

Easy to assemble while as compared with truss kind bridges

Easy for maintenance

Q13) What are the disadvantage of plate girder?

A13)

They cannot be used to assist big spans

Less architectural appearance

A bit tough to deal with in the course of the placement

Production will be finished strictly according with the layout.

Q14) Design bearing stiffeners.

A14) Bearing stiffeners are provided where forces, applied through a flange by loads or reaction, are in excess of the local capacity of the web at its connection to the flange, F, calculated as follows:

Fw = 0.909 (b1 +n2) twfyw …………….7.15

where bw is the stiff bearing length, n2 is the length obtained by dispersion through the flange to the web junction at a slope of 1 :2.5 to the plane of the flange, tw is the thickness of the web, and fyw is the yield stress of the web.

Q15) Design load carrying stiffeners.

A15) Load carrying stiffeners are checked for their buckling and bearing resistances. For buckling check, Fx < Fxd ……………………………………. 7.16

where Fx is the external load or reaction and Fxd is the buckling resistance. In the event that the load carrying stiffeners also act as intermediate transverse web stiffeners, the bearing strength should be checked for the combined loads as given in Eqn (7.14). The bearing strength of the stiffener Fbsd is obtained as follows:

Fbsd = 1.136 Aqfyq ………………... 7.17

where A, is the area of the stiffener in contact with the flange in mm2

{the actual area A is generally less than the full cross-sectional area of the stiffener as the corners of the stiffener are often coped to clear the web-to flange fillet weld (see section 1-1 of Fig. 7.18)) and

Aq as the yield stress of the stiffener in N/mm2.

The bearing strength of the web stiffener Fbsd as calculated above should be greater than or equal to Fyq the load transferred.

Q16) What is longitudinal stiffeners?

A16)

In order to obtain greater economy and efficiency in the design of plate girders, slender webs are often stiffened both longitudinally and transversely.

The longitudinal stiffeners are generally located in the compression zone of the girder.

The main function of the longitudinal stiffeners is to increase the buckling resistance of the web. The longitudinal stiffener remains straight, thereby, subdividing the web and limiting the web buckling to smaller web panels

Q17) Write note on lateral torsional buckling.

A17) The lateral torsional buckling is the deformation of the beam due to the applied loads away from its longitudinal axis. Further, it causes steel beams failures.

The deformation could occur as translational and rotational movement of the section, and these types of movements are identified as lateral torsional buckling. Figure 1 indicates the deformations that can be seen as a result of lateral torsional buckling.

Figure: Lateral Torsional Buckling

Q18) What are the effect of restraints on beam?

A18)

Continuity effects may restraint the thermal expansion of those members within the fire compartment and this effect can also change the distribution of forces in the structure.

This restraint often results in an additional compressive force in columns therefore increases its load ratio and reduces its fire resistance.

Variation of the horizontal end-restraint level has a major effect on the behaviour of the beam at high deflection, and the loading on a beam at large displacement can be carried effectively by catenary behaviour. An increase of axial horizontal stiffness helps the catenary action to prevent run-away at lower deflections.

Q19) Write a note on connections of load carrying stiffeners.

A19) Stiffeners which are subjected to load or reaction applied through a flange have to be connected to the web adequately. This connection is designed to transmit a force equal to the lesser of

(a) the tension capacity of the stiffener or

(b) the sum of the forces applied at the two ends of the stiffener when they act in the same direction or the larger of the forces when they act in different directions.

It should also be ensured that the shear stress in the web due to the design force transferred by the stiffener is less than the shear strength of the web. The stiffeners which resist tension should be connected to the flange with continuous welds or non-slip fasteners.

Q20) Give design procedure for torsional stiffeners.

A20) Torsional stiffeners provide torsional restraint at the supports and they should satisfy the following: (a) the local capacity of the web is exceeded as calculated in Eqn (7.15) (b) second moment of area of the stiffener section about the center line of the web Is should satisfy the following relation

and D is the depth of the beam at support (in mm), tcf is the maximum thickness of the compression flange of the girder (in mm), KL is the effective length of the laterally unsupported compression flange of the girder (in mm), and ry is the radius of gyration about minor axis (in mm).

Q21) Write a short note on end connection.

A21)

End connection is the maximum tough a part of the structural detailing of a metal beam.

When there is continuation or if we are assisting the girder to a few assists, the relationship desires to be designed accordingly.

However, maximum of the time, plate girders are saved as definitely supported on the stop assist. In such situations, we must offer the stiffeners on the stop connection.

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