design of steel structures

Building Materials | Use of Carbon-negative Cement in Building Construction

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Carbon-negative cement | New revolutionary Building material

Carbon-negative cement…?? Sound different, doesn’t it?

Have you ever realized how much carbon is emitted because of using concrete in the construction of buildings, highways, dams, bridges etc?

Well, here’s an answer to that. It is found that out of the 100% carbon dioxide emissions, 5% of the emissions are caused by human activities. Majority of the carbon emission is caused by usage of concrete in the constructions. How? Cement is an indispensible ingredient used for making concrete. Cement is made by baking limestone and clay powders under intense temperatures (high temperature). The intense heat which is required for the production of cement is achieved by burning of fossil fuels which in turn release large amount of carbon dioxide into the atmosphere.

Building Construction | We can just imagine to what extent the carbon dioxide would be released into the atmosphere
Building Construction | We can just imagine to what extent the carbon dioxide would be released into the atmosphere.

Carbon dioxide is also released when the conversion of limestone takes place in the kilns. This conversion is called “Calcination”. It has been observed that the amount of carbon dioxide emitted during calcination is much higher than that which is released due to burning of fossil fuels.

Recently, a British company called “Novacem” came up with this concept of manufacturing ‘carbon-negative’ cement that absorbs more carbon-dioxide than it emits over its entire life cycle.

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Guide to Design of Simple Beam | Design of Steel Structures

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Design of Simple Beam

A member carrying loads perpendicular to its axis is defined as a beam.

For a simple floor beam, I-sections are used.

M/I = (sigma) /y

M = (I/y)(sigma)

I/y = Z (section modulus)

Therefore, M = z(sigma)

When beams are loaded, bending stresses are developed at all sections.

The bending stresses developed in beams can be determined by the equation theory of simple bending.

For laterally supported beams, the permissible bending stress in tension as well as in compression should not exceed (sigma)bc or (sigma)bt = 0.66fy

For laterally unsupported beams, the permissible stress in bending compression is calculated by using tables from the the IS code book (IS:800).

Load carrying capacity of the Beam

From structural steel tables for the given beam, the section modulus (Zxx) is obtained.

Depending upon whether the beam is laterally restrained or unrestrained; the value of permissible stress in bending compression ((sigma)bc) is calculated.

The moment of resistance of the beam is found out.

MR = Zxx .(sigma)bc

Equating the moment of resistance to the maximum bending moment equation, the total load (w) the beam can carry is calculated.

Guide to Design of Built-up Beams

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Design Procedure of the Built-up Beams design

In my earlier articles, we discussed in detail about the “Theory of Built-up Beams“. In this article, we will move a step ahead and understand the concept of the design of Built-up beams.

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.

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Guide to designing a Rolled Steel Beam

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Six Step Guide to Designing a Rolled Steel Beam

Here are a few simple steps that are to be followed for the design of Rolled Steel Beam:

Step one

Calculate the maximum Bending Moment and Shear Force

Step two

Depending upon whether the beam is laterally restrained or unrestrained, calculate the permissible stress in bending compression (sigma bc) using the equation;

sigma bc = 0.66fy

Step three

Find the required Section Modulus (Zreq)

Zreq = M/sigma bc

Step four

From the structural tables, choose a suitable section such that the section modulus is slightly more than the required section modulus.

Step five

Check for shear.

Calculate the maximum Shear force in the beam. Calculate the average shear stress in the web and this should be less than 0.4fy.

Tv = (Shear Force)/HLw

where = H = height of the web

Lw = length of the web

Step six

Check for deflection

Ymax < 1/325 of span

Structures and Classification of Structures | Design of Steel Structures

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What is a Structure?

When any body is subjected to a system of loads and deformation takes place and the resistance is set up against the deformation, then, the body is known as structure. The structure are means of transferring forces and moments. The structures may be classified as statistically determinate structures and statistically indeterminate structures. When the equations of statistics are enough to determine all the forces acting on the structures, in the structures, then, the structures are known as statistically determinate structures.

Design of Steel Structures
Design of Steel Structures

When the equations of statistical equilibrium are not sufficient to determine all forces acting on the structure and in the structures, then the structures are known as Statistically Indeterminate Structures. The equations of consistent deformations are added to the equations of equilibrium inorder to analyse the Statistically Indeterminate Structures.

Classification of Structures

The structures are categorised by their supporting systems. There are one dimensional, two dimensional and three dimensional supporting systems.

  1. When a supporting system is subjected to only one type of stresses, then, it is known as basic system.
  2. When a system is subjected to simultaneously several types of stresses, then it is known as mixed system.

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Relationship between Structural and Architectural Design

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  • Structural Engineering and Architecture are two different sciences that are inter-related. Structural Designing deals with the study of design of steel in a structure i.e., the internal skeleton of the structure that helps to keep the structure durable, sound and stiff.
  • Whereas Architectural Design deals with design of spaces meant for a particular function. It helps to create ambient environment that is pleasing to eye. The Architect designs the building keeping all the functional aspects in mind that are to be incorporated into the design and then they are executed by a Civil or Structural Engineer.
Inter-relationship of Architectural Design and Structural Design
Inter-relationship of Architectural Design and Structural Design
  • The structures and structural members are designed to meet the functional and structural aspects. Both the aspects are inter-related. The functional aspect takes into consideration the purpose for which the building or the structure is designed. The functional aspect includes the determination of the amount and arrangement of space necessary for the structure.

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Column Bases | Design of Steel Structures

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Column bases are structural elements used in the design of steel structures to transfer the column load to the footings.

Types of Column bases

  1. Slab base
  2. Gusseted base

Slab Base

Slab Base

Slab bases are used where the columns have independent concrete pedestals. A thick steel base plate and two cleat angles connecting the flanges of the column to the base plate. In addition to these, web cleats are provided to connect the web of the column to the base plate. These web cleats guard against the possible dislocation of the column during erection. The ends of the column and also the base plate should be mechanized so that the column load is wholly transferred to the base plate.

Area of base plate= (load of column)/(permissible bearing stress in concrete)

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