Question

Recall the difference between working stress (WSD) and ultimate strength (USD) design procedures for reinforced concrete.

Answer 1

* WORKING STRESS METHOD

-THIS WAS THE MOST COMMONLY USED TRADITIONAL METHOD OF DESIGN FOR REINFORCED CONCRETE.

-THE MAIN ASSUMPTION OF THIS METHOD IS THAT THE MATERIAL IS ASSUMED TO BE AS LINEAR ELASTIC.

-WORKING LOADS ARE TAKEN INTO CONSIDERATION DURING THE DESIGN AND IT RESULTS IN RESTRICTING THE STRSSES IN THE MATERIAL.

-THE ASSUMPTION OF LINEAR ELASTIC BEHAVIOUR IS JUSTIFIED AS THE PERMISSIBLE STRESSES ARE BELOW THE MATERIAL STRENGTH.

-FOR THE SAFTEY PURPOSE FACTOR OF SAFTEY IS CONSIDERED DURING THE DESIGN. WHICH IS THE RATION OF STRENGTH OF MATERIAL TO THE STRENGTH OF PERMISSIBLE STRESSES.

-MAIN DISADVANTAGE OF THE DESIGN METHOD IS RESULTING IN LARGE SIZE OF THE STRCTUTAL MEMBERS SUCH BEAMS, COLUMNS ETC MAKING IT UNECONOMICAL.

*ULTIMATE STRENGTH DESIGN.

-IN PRESENT DAYS WITH IMPROMENT IN TECHNOLOGY AND BETTER UNDERSTANDING OF THE MATERIAL PROPERTY THE SHORCOMINGS OF THE WORKING STRESS METHOD ARE OVERCOME .

-IN THIS ULTIMATE LOAD IS TAKEN INTO CONSIDERATION IN THE DESIGN, WHICH INDICATE THAT UPTO THE FAILURE CAPCITY THAT IS COLLAPSE OF THE STRUCTURE IS ANALYSED.

-IN THIS METHOD THERE IS AN INDICATION OF FAILURE OF THE STRUCTURE BEFORE IT FAILS.

-THE NON LINEAR STRESS-STRAIN CURVE OF CONCRETE IS TAKEN INTO CONSIDERATION.

-IN WORKING STRESS METHOD FACTOR OF SAFTEY IS TAKEN WHERE AS IN ULTIMATE DESIGN LOAD FACTOR IS TAKEN WHICH IS THE RATION OF ULTIMATE LOAD TO THE WORKING LOAD.

-IN THIS CASE THE DIFFERENT LOADING PATTERNS CAN BE TAKEN INTO AND ALSO THE COMBINED LOADING CONDITIONS CAN ALSO APPLIED BUT THIS IS NOT POSSIBLE IN WORKING SRESS METHOD.-

-THIS METHOD RESULTS ECONOMICAL SECTION OF THE STRUCTURAL MEMBERS SUCH AS BEAM, COLUMN AND ARE SLENDER SECTIONS.

-DUE TO THE SLENDERNESS SECTION DEFLECTION AND CRACKS DEVELOP UNDER SERVICE LOADS.

-ANALYSIS OF THIS METHOD IS STILL BASED ON LINEAR ELASTIC THEORY