How to build up an earthquake-resistant structure

Earthquake means quick shaking of the ground due to the shift of rock and tectonic plates underground. The ground appears as solid, but the topmost crust of earth is deep and long periods of time produce pressure to develop among plates and fissures.

When the pressure is applied, seismic vibrations and fierce shaking reverberate to the surface which instantly impact miles of land. Once the initial quake hits, aftershocks happen to create further damage.

The buildings should withstand radical movement and foundation shifts so as to reduce damage and safeguard the people inside and around them. Earthquake-resistant building designs should be created based on the following characteristics which impact their structural integrity: stiffness and strength, regularity, redundancy, foundations, and load paths.

Stiffness and Strength: While creating design for earthquake-resistant buildings, safety professionals suggest sufficient vertical and lateral stiffness and strength – specifically lateral. Structures are likely to deal with the vertical movement resulting from quakes superior to the lateral, or horizontal, movement.

Devoid of taking earthquakes into consideration, professionals still concentrate on a building’s vertical stiffness and strength since it has to support itself. However, earthquakes present new directional forces and owing to these, buildings will shift left and right, and, if not constructed perfectly, will rapidly destabilize.

Regularity: This characteristic pertains to the movement of the building if pushed in lateral directions. According to safety professionals and building designers, the building should move uniformly in order to disperse the energy devoid of placing extra force on one side or another. When a building is uneven, then flaws will be detectable while the building shakes. The flaws will be settled and the structure will experience concentrated damage – which settles the structure completely.

Redundancy: It is a vital safety characteristic while designing for safety. Redundancy assures that there exist several strategies in place whether one fails. These can possibly be add to the building cost, but redundancies become vital if/when a natural disaster like an earthquake happens. Safety professionals suggest to uniformly allocate mass and strength during the structure so strength isn’t entirely dependent on one factor.

Foundations: A steady foundation is a vital characteristic of constructing a large structure irrespective of natural disaster risks. It is important for a building’s long-term existence, and a robust foundation is required to withstand an earthquakes powerful forces. Different areas have unique foundational characteristics that define how a structure’s base needs to be reinforced. Professionals should stringently monitor reactions of the ground and movement prior to starting of construction. The buildings developed to withstand fierce earthquakes contain deep foundations and driven piles. To settle these radical measures, the foundations should be joined properly to facilitate moving as a unit.

Continuous Load Path: Binding into the stable foundation characteristic, structural and nonstructural elements of a building should be interlinked in order that inertial forces are dispersed. Numerous points of strengths and redundancies distribute the force rather than the quake partitioning the foundation apart. It refers to the continuous load path characteristic that safety professionals, architects, and engineers should be aware of at the time of creating the design. When the structure is not entirely fastened jointly, elements fail to shift separately and collapsing can occur. The incessant load path is the journey of earthquake through the building – laterally and vertically. The path should be intact so that it can disperse an earthquake’s powerful shudders.



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How to erect a bridge – some vital guidelines

Given below, some necessary stages to construct a bridge in the public works sector.

Step One: The Foundations - The purpose of foundation is to disperse different types of loads of the bridge (mass, weight, overload, forces …) perfectly based on the type of the ground of the structure.

The foundations are categorized as the following two types :-

• The superficial foundations: These foundations are ideal for the bridges with level adjacent to the ground since the structures are susceptible to reduced constraints in comparison with the wind and their gravity. It is also necessary that the rocks within the structure should be strong, undecomposed and not greatly cracked.
• Deep foundations: This type of foundation is effective while the bridge starts to obtain the height. Under this situation, it occurs consistently that the soil exposes a layer more stable in depth. At the time of construction, there are three situations which produce the following three types of foundation:

a. Referred to as “good” soil, when it allows to set the foundations directly on a durable ground, is known as flat foundation.
b. Referred to as “bad then good” soil, when it is required to place four piles in the unsteady ground unless they attain the steady ground.
c. The soil becomes “unsettled”, when the quality of soil in the ground is not good. Under this circumstance, lots of piles should be installed to provide good resistance capacity severe compression.

Without resistance at depth, the support should be provided with “floating” piles.

Second Step: Construction of Supports - The number of supports (abutments and piles) required for the construction of the bridge should be affixed concurrently on both sides of the shores. These supports are generally formed with concrete and either cast in place, or prefabricated in a factory and then assembled on site.

Third Step: Assembly and Start-Up of the Superstructure - Due to the final weight of the structure, the greater or smaller spacing among every pile and the final objective of the structure, it becomes complicated to apply the concrete for the construction of the deck which, over great distances, fall down even because of its own weight and of its traffic. For this reason, the elements of metal beams are used. These are assembled jointly to build up the structure of the deck.

On every shore, the beam elements are set up through a crane and the elements are then reconstructed with welding on site (Welded I-Beams). The deck is then provided with a launching nose, finished with a ballast at the back to resist tipping. Normally, the piles are driven with winches, cables and pulleys, the deck advances at a speed of about 9m / h. Also, this solution is substituted with restraint systems to stop runaway.

Fourth Step: Pouring the Slab - The beams are provided with connectors in the factory so that the steel structure is secured to the concrete slab of the latter. As soon as the beams are installed on their final supports, the lost formwork is arranged on them along with reinforcement prior to pouring a layer of concrete with thickness of about 25cm that will be the slab of the structure.

Step Five: Finishes - To complete the work, after several months, even years of construction, the final step is to provide asphalt on the road. Asphalt stands for a very specialized type of bitumen to resist expanding of deck. Thus, even with some deformations of steel, the bitumen will not crack and retain the quality to adapt the road traffic.

Several sensors are arranged on each strategic part (deck, cable stay, piles, pylons …) and facilitate to constantly follow the state of the bridge.



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Advantages of microsillica in concrete

Microsilica alias silica fume or condensed silica fume stands for is a mineral admixture that is formed with very fine solid glassy spheres of silicon dioxide. Most microsilica particles remain under 1 micron (0.00004 inch) in diameter, normally 50 to 100 times finer as compared to average cement or fly ash particles. Microsilica belongs to a by-product of the industrial manufacture of ferrosilicon and metallic silicon in high-temperature electric arc furnaces.

Microsilica may be suitable in managing heat formation in mass concrete. It can also be combined with fly ash to provide superior result.

If pozzolanic materials are integrated with concrete, the existent silica in these materials makes a reaction with the calcium hydroxide produced throughout the hydration of cement and develops supplementary calcium silicate hydrate (C – S – H) that enhances the strength and the mechanical properties of concrete.

Types of Microsilica: Microsilica is categorized as follow -

1. Powdered microsilica, 2. Condensed microsilica, 3. Slurry microsilica

Impacts of Microsilica on Concrete

1. Fresh Concrete

a. It decreases the scope of segregation, so it is applied as pumping aid.
b. It almost reduces bleeding, as a result finishing work commences before time.
c. Workability and uniformity of concrete reduces.

2. Hardened Concrete: The inclusion of microsilica enhances the following characteristics of hardened concrete -

a. Improves compressive strength that leads to improve flexural and tensile strength.
b. Bond strength
c. Abrasion resistance
d. Lessens permeability; consequently, it safeguards reinforcement steel against corrosion.
e. Impact and cavitations resistance.
f. Sulphate Resistance
g. Heat Reduction
h. Chemical Resistance

Properties of Microsilica:

1. Microsilica belongs to a grey; almost white to black powder.
2. Spherical particles remain under 1mm in diameter.
3. The mass density of microsilica is dependent on the degree of densification and differs from 130 to 600 kg/m3.
4. The specific gravity of microsilica differs among 2.2 to 2.3

Benefits:

a. Minimizes thermal cracking resulting from the heat of cement hydration.
b. Enhance the strength to resist against sulphate and acidic waters.
c. Minimizes the growth of temperature in preliminary stage.
d. Silica fume is cheap; therefore, it is inexpensive.
e. It minimizes the entire slab weight and cost.
f. Inclusion of microsilica reduces efflorescence caused by the refined pore structure and increased consumption of the calcium hydroxide.



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Design of Beam

1. Estimation of constants. -For the specified set of stresses, determine KC, JC and RC.

2. Kc= M~cbc/M~cbc+~st

3. Jc= 1-(Kc/3)

4. Rc= 0.5*L*Kc Jc

5. Estimation of bending moment. Suppose appropriate values of overall depth and breadth of beam, and find out the effective span. Work out the self-weight and total U.D.L. and maximum bending moment in the beam.

6. Design of the section. Workout the effective depth of the beam with the following expression:

7. d= [(M)/ (RC*b)] 0.5

8. Reinforcement. Workout the area with the formula.

9. Shear Reinforcement. Workout the maximum shear force in the beam.

10. Verify for Development length at the end.

11. Ld<= (M1/V) +L0.

Design of column:

1. Find out the allowable stresses in concrete, longitudinal bars and ties.
2. Determine the super impose load that should be borne by the column.
3. Find out the area from the following expression - P= ~cc *Ac+~sc*Asc.
4. After getting details about the area, find out the dimensions of column. If it is a square of side b, then b=Ag.
5. For the specified end conditions, find out the effective length of column. Measure lef/b ratio to determine whether the column is short or long.
6. If lef/b ratio<12 it will be designed as short column or else as long column; define the area of steel Asc.
7. Determine the diameters of bars utilized as ties and find out its pitch according to the rules.

DESIGN OF FOOTING: The width B of the footing will obviously be equivalent to [W+W‟]/qo. The thickness is measured based on the bending moment as well as punching shear.

1. Depth for bending moment.
d= [M/B*Rc] 0.5
2. Depth for shear.
3. tv=V/B*d
4. Steel Reinforcement. Ast=M/tjcd

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Steel Buildings and their various benefits

Steel buildings are eco-friendly. Any steel structure integrates the organic material and for this reason mould and mildew infestations are not occurred. The steel buildings are 100% recyclable and can be used further.

Steel building construction is mostly recognized for their flexibility and stability. Steel buildings are designed for both permanence and impermanence i.e. they are utilized for storage throughout project execution or for long term preservation of machinery or goods. The steel building can provide the following benefits :-

1. Easy Set Up: The steel frames are fabricated perfectly to adapt collectively with one end skidding into the other. No special fasteners are necessary as well as cutting, retaining, and hammering concurrently long, immense and bulky planks.

2. Cost effective: As the steel is perfectly slashed at the time of manufacturing, no waste occurs in construction site. Less salary is disbursed due to requirement of fewer employees.

3. Environmentally Friendly: The steel buildings are environmentally friendly and they provide good benefits for construction. Steel is the most reprocessed material and several manufacturers utilize recycled steel in all of their steel building materials.

4. Energy Savings: Energy efficiency is another good aspect of an environmentally friendly building. In steel buildings, there are window placement, Tinted Windows, Insulated Frames, Vapor Retarders between the foundation and concrete slab.

5. Safe and stable: Steel frame buildings have strong resistance strength against flame as compared to wood framed constructions. Steel can also resist the attack from termites, bugs or rodents as well as mold or fungi.

It does not require any type of chemical to maintain it’s longevity. A steel frame building is efficiently grounded and less likely to be hit or damaged by lightning.

6. Superior construction quality: A steel frame building does not deteriorate in due course and weaken like wooden structures become over time. So, no need to worry about fragile spots. Steel has also good resistance capacity against corrosion. It is dimensionally steady and there is no distortion with climate changes.

7. Longevity: Steel contains heaviness ratios of any building material. It never buckles, divides, distorts, rotates, chinks, rots or splinters. It’s weight is less as compared to timber. It is can be handled easily and built up with specifically when lifting partitions and roofs.



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How to examine verticality of structure throughout building construction

The verticality works should be examined at the time of building up construction at various stages like during setting up vertical formworks of columns and transmitting levels up successive floors of multi storey structures.

Some useful processes to check verticality of structure throughout building construction
1. Plumb-bob technique
2. Spirit level
3. Theodolite
4. Optical plummet

1. Plumb-Bob Technique: The purpose of this technique is to make sure that constructions are plumb or vertical. It’s application is also found in surveying to set up the nadir regarding gravity of a point in space.

Plumb-bob comprises of a weight with pointed tip on the bottom that is tied to the end of a string. The heavy weight will cling under gravity and produce a precise vertical line that is known as plumb line.

This method is very effective for examining or managing vertical line of structural elements especially indoors like lift shaft. Besides, it is also utilized to check the verticality of foundation, walls, and columns.

The plumb line or vertical line of plumb-bob is affected by wind force and the perfectness is not maintained. It is possible to minimize small to medium lateral movement of plumb-bob efficiently by moistening it in oil or water.

In case the height of structural member is broad, then the string can be substituted with a long wire, but precautions should be plasticized to get rid of imposing risks to the personals functioning under.

2. Spirit Level Method: This tool is used for managing verticality of small scale works; as for instance inspection of formworks and door frames. If spirit level is applied for guess verifications, then it is necessary to examine the verticality with more precise method.

3. Theodolite Method: Theodolite is considerably robust instrument that is utilized to examine verticality works throughout construction providing proper preciseness.

It is useful for examining or managing verticality of towers, wall, foundation and columns specially large number of columns along a one grid line.

The slope can be calculated out of plumb line of the member with Theodolite in conjunction with a tape.

The following methods are utilized to examine column verticality:

Install the digital Theodolite to the center on a peg that is set up 500 mm from the column grid.
Once the Theodolite is installed perfectly the laser beam will be activated and put it to the steel tape that is retained to the formwork.
The reading of the steel tape is captured via the telescope.
Capture the readings of two positions at the equivalent level on both top and bottom levels of the formwork. Any curvature on the surface is easily found by capturing two readings at the same level.

4. Optical Plummet Method: It belongs to an instrument that sight directly down or directly up. Optical plummet contains an automatic compensator that considerably enhances its perfectness with regards to other methods which are applied for managing verticality.



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Different types of beam section in RCC structures

In this construction video tutorial, you will gather information on different types of beam section in RCC structures. Usually, there are three types of beam sections which range from balanced beam section , under reinforced beam section and over reinforced beam section.

It is known that a beam comprises of two components i.e. reinforcement and concrete.

Balanced Beam Section: If the ratio of steel to concrete in a section prevails in such a manner that the strain in steel and strain in concrete attain their maximum values all at once, the section is identified as a balanced or critical section and the percentage of steel in this section is defined as critical steel percentage.

Under-Reinforced Beam Section: Under-reinforced section: A section that contains steel percentage below the critical percentage is called as under-reinforced section. As steel lacks to adjust compression in concrete, the tensile strain in steel attains yield value whereas the highest compressive strain in concrete is under its ultimate crushing value.

The section undertakes large rotational deformations from the preliminary phase of yielding of steel to the final stage of crushing of concrete, providing adequate warning of impending failure.

Given below, an extensive lists of different types of basic geometry formulas :-

Yielding of steel in under-reinforced beam section does not signify that the structure has failed, because if steel yields, extreme deflection and cracking in beam will happen prior to failure which provides sufficient time to occupants to escape ahead of the section fails.

The failure in under-reinforced beam section occurs as the concrete attains its ultimate failure strain of 0.0035 prior to steel attains its failure strain which is greater than 0.20 to 0.25.

Over-Reinforced Beam Sections: Reinforced concrete beam sections, in which the failure strain in concrete is attained sooner than the yield strain of steel is obtained, are known as over-reinforced beam sections.

If over-reinforced beam is designed and loaded to complete strength then the steel in tension zone will not yield much prior to the concrete attains its ultimate strain of 0.0035. It happens because of little yielding of steel, the deflection and cracking of beam does not happen and provide enough warning prior to failure.

Failures in over-reinforced sections happen suddenly. This type of design is not approved in practice of beam design.

To get more in-depth information, go through the following video tutorial.

Video Source: Tutorials Tips

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Published By
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www.constructioncost.co
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How to calculate the quantities for steel, cement, sand & aggregates in a flat slab

This construction video tutorial will produce some useful tips on how to find out bar bending schedule of flat plate slab as well as work out the quantities of different materials like steel, cement, sand & aggregates inside a slab.

In this video a sample slab drawing is taken and it’s length and width are 2 meters and 5 meters. Clear cover for this slab is 25 mm. Main bar as well as distribution bar contain the size of 12 mm. Center to center distance is 150 mm. The density of the slab is 125 mm.

The mix grade used in the slab is M15 in the proportions 1:2:4.

The quantities will be calculated on the basis of the above dimensions.

To learn the complete process, watch the following youtube video.

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Published By
Rajib Dey
www.constructioncost.co

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