Showing posts with label Structural analysis. Show all posts
Showing posts with label Structural analysis. Show all posts

Tuesday, 9 January 2018

Tests on Bricks

The following laboratory tests may be conducted on the bricks to find their suitability:

(i) Crushing strength                     

(ii) Absorption

(iii) Shape and size and

(iv) Efflorescence.

(i) Crushing Strength:

The brick specimen are immersed in water for 24 hours. The frog of the

brick is filled flush with 1:3 cement mortar and the specimen is stored in damp jute bag for 24 hours and then immersed in clean water for 24 hours. The specimen is placed in compression testing machine with 6 mm plywood on top and bottom of it to get uniform load on the specimen. Then load is applied axially at a uniform rate of 14 N/mm2 . The crushing load is noted. Then the crushing strength is the ratio of crushing load to the area of brick loaded. Average of five specimen is taken as the crushing strength.

(ii) Absorption Test:

 Brick specimen are weighed dry. Then they are immersed in water for a

period of 24 hours. The specimen are taken out and wiped with cloth. The weight of each specimen in wet condition is determined. The difference in weight indicate the water absorbed. Then the percentage absorption is the ratio of water absorbed to dry weight multiplied by 100. The average of five specimen is taken. This value should not exceed 20 per cent.

(iii) Shape and Size:

 Bricks should be of standard size and edges should be truely rectangular with sharp edges. To check it, 20 bricks are selected at random and they are stacked along the length, along the width and then along the height. For the standard bricks of size 190 mm × 90 mm × 90 mm.

IS code permits the following limits:

Lengthwise: 3680 to 3920 mm

Widthwise: 1740 to 1860 mm

Heightwise: 1740 to 1860 mm.

The following field tests help in ascertaining the good quality bricks:

(i) uniformity in size

(ii) uniformity in colour

(iii) structure

(iv) hardness test

(v) sound test

(vi) strength test.

(i) Uniformity in Size:

 A good brick should have rectangular plane surface and uniform in size.

This check is made in the field by observation.

(ii) Uniformity in Colour:

 A good brick will be having uniform colour throughout. This observation may be made before purchasing the brick.

(iii) Structure:

 A few bricks may be broken in the field and their cross-section observed. The

section should be homogeneous, compact and free from defects such as holes and lumps.

(iv) Sound Test:

 If two bricks are struck with each other they should produce clear ringing sound.

The sound should not be dull.

(v) Hardness Test:

 For this a simple field test is scratch the brick with nail. If no impression is marked on the surface, the brick is sufficiently hard

(vi) Efflorescence:

The presence of alkalies in brick is not desirable because they form patches of gray powder by absorbing moisture. Hence to determine the presence of alkalies this test is performed as explained below: Place the brick specimen in a glass dish containing water to a depth of 25 mm in a well ventilated room.

 After all the water is absorbed or evaporated again add water for a depth of 25 mm. After second evaporation observe the bricks for white/grey patches. The observation is reported as ‘nil’, ‘slight’,

‘moderate’, ‘heavy’ or serious to mean

(a) Nil: No patches

(b) Slight: 10% of area covered with deposits

(c) Moderate: 10 to 50% area covered with deposit but unaccompanied by flaking of the surface.

(d) Heavy: More than 50 percent area covered with deposits but unaccompanied by flaking of

the surface.

(e) Serious: Heavy deposits of salt accompanied by flaking of the surface.

Damages in Earthquake

Damages Due To Earthquakes

Earthquake is a natural catastrophe that may instantly kill or incapacitate a large number of people, cause huge destruction to structures, and weaken the buildings reducing their useful life. The damage is the maximum close to the epicenter, the point from where the vibrations are initiated. Different types of damages can occur due to earthquakes, and these are discussed in succeeding paragraphs.

Liquefaction

Liquefaction starts with the forceful shaking of the soft wet soils, and rearrangement of its grains, due to which the soils start functioning as liquids. The load of structures is transmitted to the wet soils that may be changed into quicksand. The material that has been liquefied, may loose its bearing strength due to the excessive weight of the structures above it, and produce landslides. Consequently, the fluid pressure of the liquefied region may cause tilting or breaking of walls, failure of basement floors, and if the foundations are weak severe damage to the structures may occur. Any items or materials above the liquefied soil may be submerged into the soft soil. The liquefied region may itself also go downwards into the earth, and in the process bury anything on it.

Ground Shaking

The magnitude of ground shaking at a particular location will determine the earthquake damage. The extent of ground shaking will depend upon the scale of an earthquake, distance from the epicenter, and nature of the material. When the earthquakes are great, the amplitude is large, duration is more, and the area is vast. The amplitude of ground shaking at a site depends upon its distance from the epicenter of the earthquake, and it decreases with the increase in distance. Similarly, motions are of low frequency when these are located at greater distances. The ground motion frequency is a significant feature that determines the extent of damage to the structures, and the nature of construction that can be affected.

Structural Hazards

Earthquakes are a severe structural hazard that causes vibrations in the structures due to the ground shaking. If the structures are weak, or extremely rigid to withstand severe vibrations, then these may collapse. The tall buildings may experience extreme vibrations due to their height, and may fall down or into each other. Other destructive effects on structures due to an earthquake are sliding away from their foundations, and their horizontal or vertical movements that may make the structures unsafe.

Other Hazards

Other hazards that may cause earthquake damage include fire that can be started on the rupturing of power or gas lines, and severe losses may occur. In addition, bricks, rocks, trees may fall, sewage may enter water supplies and drinking of such water can cause serious diseases, and failure of transportation and means of communication may hinder rescue efforts. Furthermore, valuable records held by business concerns and governmental offices may be lost creating serious difficulties.

Preventive Measures

Preventive measures may reduce the destructive effects due to earthquakes, but may not completely eliminate the risk of damages. If a building is not properly designed to withstand earthquakes, it will be exposed to greater risks of structural damage. Suitable fixing of the structure with the foundation, and among the different constituents of the structure, is important for earthquake resistance. Structures that are not properly connected with the foundations may be shifted during an earthquake.

 

Friday, 17 June 2016

Slope deflection method sway portal frame numerical probleam

Analysis the portal frame shown in following fig. by Slope deflection method and draw bending moment diagram.


Answer:-

Slope deflection method is help to determine the bending moment of sway portal frame.

Step 1:-  At fixed support the angle is zero i,e it and the deflection in beam as a delta is shown in fig. All loads are applied on it.





Step 2:- Very 1st the calculation of fixed end moment is determine by using simple fixed end formulas. And the sign convension are placed -ve & +ve respectively.

Wednesday, 15 June 2016

Types of Stairs


The stairs may be built with wood, concrete masonry or with cast iron. Wooden stairs are not safe, because of the danger of fire. However they are used in buildings to access to small areas in the upper floors.

 Cast iron or steel stairs in the spiral forms were used commonly to reduce stair case area. In many residential buildings masonry stairs are also used. Reinforced concrete stairs are very commonly used in all types of buildings.

CELLULAR CONCRETE


It is a light weight concrete produced by introducing large voids in the concrete or mortar. Its density varies from 3 kN/m3 to 8 kN/m3. It is also known as aerated, foamed concrete.

Properties of cellular concrete
1. It has low weight.

2. It has good fire resistance.

Tuesday, 2 February 2016

Moment Distribution Method Portal Frame Numerical

In this video i completely explained the procedure for solving the MDM of portal frame. This method is very important for analysis of any building. We can solve this method by fallowing steps:-

1_ Determination of Fixed End Moments
2_ Determination of stiffness factor
3_ Determination of Distribution factor
4_ Solving sway and non sway MDM table to get joints moments
5_ Determination of sway correction factor
6_Simple bending moments
7_Final bending moments diagram

                                      Watch the video to learn Moment Distribution Method


Friday, 9 October 2015

Clapeyron's three moment theorem by parag pal Part-2

                               
This video is all about Clapeyron's three moment theorem. In this video the detail solution is given by mi that how to solve the TMT. This type of nums important to analysis the beam.

Clapeyron's three moment theorem by parag pal Part-1


This video is all about Clapeyron's three moment theorem. In this video the detail solution is given by mi that how to solve the TMT. This type of nums important to analysis the beam.

Fixed beam by three moment thm


This video is all about Clapeyron's three moment theorem. In this video the detail solution is given by mi that how to solve the TMT. This type of nums important to analysis the beam.

Non sway portal frame analysis by Kani's method


Kanis method is important to analysis the portal frame as well as the beam. In this method the more number of interations are important. The kanis method having sway and non-sway portal frame which comes in some little difference that is the story moment. Solve the nums by this method as I listed in video. ENJOY

Sway analysis by Kani's method


Moment distribution method