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Effect Of Eccentricity On Analysis and Design Of Isolated Footings

PAPER ON EFFECT OF ECCENTRICITY ON ANALYSIS & DESIGN OF ISOLATED FOOTINGS
(A CASE STUDY OF Jammu and Kashmir)

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ABSTRACT
Footings are often subjected to moments from columns in addition to the axial loads. The presence of certain amount of eccentricity of loading in the footing induces moment on footing. A careful consideration has to be given to the presence of eccentricity, while performing the analysis and design of such footings, as an increase in eccentricity beyond certain limit renders a considerable area of footing ineffective to resist the stresses due to development of tension. Under these circumstances, the conventional flexural equation becomes inapplicable, thereby imparting more complexity in the analysis.

In this Thesis an attempt has been made to understand the behaviour of footings subjected to Uniaxial and biaxial eccentricity.

Two cases of uniaxial eccentricity are considered, Case I with column placed away from centre of footing, load being concentric with the column and Case II with column at centre of footing and load placed at certain eccentricity. For each case three conditions of eccentricity are considered ie e=0, eL/6. Complete analysis has been performed using Limit State Method for SBC = 40, 50, 65 and 100 KN/Sq m which are prevalent in the region under consideration. For biaxial cases two eccentricity conditions with eL/6 and SBC = 100 KN/Sq m have been analyzed. The analysis of footing subjected to biaxial eccentricity was carried out manually and as per charts and tables prevalent in literature.

A comparative study was conducted for both cases with reference to the design parameters and permissible values. The effect of eccentricity on quantity, cost and various other parameters were studied. The analysis was also carried out using SAP – 2000 Software for both Uniaxial and Biaxial Cases. The results obtained manually and by the use of software have been compared and difference analyzed. A computer program was developed for Analysis and Design of footing for Uniaxial and Biaxial cases in M.S. Excel to reduce the iterative work and to save time.

It was observed that there is a remarkable increase in quantity of concrete and steel when the loads are eccentric, the increasing factor being more in case of column placed away from the centre of footing as compared to the column placed at centre of footing. The results also highlight that the foundations become highly uneconomical if the geotechnical investigation reveals incorrect values of safe bearing capacities.
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Cement And Water Saving With Water Reducers

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

In India 0.93 kg of CO2 is emitted in the production of one kg of cement. In the financial year 2009-10 India produces 200 million tonnes of cement. In the production of this cement 186 million tonnes of CO2 was emitted in the atmosphere during financial year of 2009-10.

The availability of water in India per person per year in 1950 was 5177 cu.m. In the year 2009 it is reduces to 1700 cu.m.

If 50 million tonnes cement in making concrete uses water reducers 7500000 tonnes of cement can be saved. 3750000 kl of potable water will be saved and the saving of Rs. 3300 crores per year to construction industry. This amount is worked out after adjusting the cost of water reducers. Less cement used means less cement required to be produce by the cement factories resulting 6975000 tonnes of CO2 will be prevented to be emitted to the atmosphere. These are worked out with an average saving of 15% cement and 15% water.

CO2 emission is word problem, but for India in addition to CO2 it has problems of Air, Water, Soil, Food and Noise pollutions. Less densily populated countries may cope with these problems but for India it is of the top concern. The population figures of 2009 is, India 350 person per sq.km, China 132 person per sq.km and USA only 34 person per sq.km. The figures of 2006 CO¬2 emissions are USA 658.60 tonnes per sq.km, China 611.76 tonnes per sq.km and India 459.35 tonnes per sq.km. Every one should contribute his or her efforts to save the environment from pollution. Those involve in the construction activities can contribute their share by proper design of concrete Mixes. This is best illustrated by the following examples.
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Mix Design For Concrete Roads As Per IRC-15-2002

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

Check out the Mix Design For Concrete Roads As Per IRC:15-2011

ABSTRACT:
The stresses induced in concrete pavements are mainly flexural. Therefore flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. A simple method of concrete mix design based on flexural strength for normal weight concrete mixes is described in the paper.

INTRODUCTION:
Usual criterion for the strength of concrete in the building industry is the compressive strength, which is considered as a measure of quality concrete. however, in pavement constructions, such as highway and airport runway, the flexural strength of concrete is considered more important, as the stresses induced in concrete pavements are mainly flexural. Therefore, flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. It is not perfectly reliable to predict flexural strength from compressive strength. Further, various codes of the world specified that the paving concrete mixes should preferably be designed in the laboratory and controlled in the field on the basis of its flexural strength. Therefore, there is a need to design concrete mixes based on flexural strength.

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Fly Ash Determination In The Supplied Portland Pozzolana Cement

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

There is no direct method for the determination of Fly Ash content in the PPC. However, based on the past test results of insoluble Residue in the PPC, Fly Ash content in the supplied PPC may be obtained.

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Simple Testing Of Admixtures And Surface Coating For Permeability To Water.

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

This method of test describes the procedures for determining concrete permeability to water by capillary absorption method for comparison between controlled specimens and the specimens containing admixtures having surface coatings. This method gives the waterproofing efficiency of admixtures and coating, thus also of the greatest interest for durability of concrete offers protection to reinforcement from corrosion.

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