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Analysis of Truss

Defination,Analysis of frames,stresses in frame,convention,
assumptions, solutions(analytical), Learning outcomes

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Analysis of Truss

1. 1. ANALYSIS OF TRUSS
2. 2. Syed Raheel Zafar
3. 3. WHAT IS TRUSS? • A truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints. • If all the bars lie in a plane, the structure is a planar truss. • The main parts of a planar truss.
4. 4. ANALYSIS OF FRAME • A FRAME IS A STRUCTURE MADE OF SEVERAL BARS/ RODS WELDED / RIVETTED TOGETHER • THE BARS ARE ANGLE IRONS/ CHANNELS OF “I” OR “T” SECTIONS. THESE ARE CALLED MEMBERS • ON APPLICATION OF LOAD ON TO THE STRUCTURE, THE MEMBERS REMAIN LOADED WITH TENSILE/ COMPRESSIVE LOAD • MEMBERS UNDER TENSION • MEMBERS UNDER COMPRESSION • THE STRUCTURE FORMED BY THE MEMBERS IS CALLED “TRUSS” • EXTENSIVELY USED IN ROOF, BRIDGE, SHEDS ETC.
5. 5. STRESSES IN A FRAME • UNDER APPLICATION OF LOAD THE STRUCTURE TENDS TO DEFORM. THE MATERIAL OF THE FRAME TENDS TO KEEP THE FRAME RIGID ( PREVENTS DEFORMATION) • AN INTERNAL RESISTIVE FORCE IS SET IN IN THE MATERIAL . THIS INDUCES STRESS. • σ = INTERNAL RESISTANCE / AREA • LOAD CAN BE PULL / PUSH (TENSILE/ COMPRESSIVE) • FOR JOINTS TO BE IN EQUILIBRIUM THE MEMBERS MAY CARRY ZERO LOAD/ TENSILE/ COMPRESSIVE LOAD.
6. 6. CONVENTIONS • ANALYST HAS TO IDENTIFY THE SITUATION , MAKE A MENTAL PICTURE OF THE FORCES AND DECIDE THE ARROWS. • A LOAD WITH ARROW AWAY FROM THE JOINT IS TENSILE • A LOAD WITH ARROW TOWARDS THE JOINT IS COMPRESSIVE
7. 7. ASSUMPTIONS MEMBERS ARE RIGIDILY JOINT (Every member of the truss is then in pure compression or pure tension – shear, bending moment, and other more complex stresses are all practically zero. ) •LOADS ACT ON THE JOINTS ONLY •WEIGHT OF THE MEMBER AS COMPARED TO THE EXTERNAL LOADS IS NEGLIGIBLE AND NOT CONSIDERED FOR CALCULATIONS.
8. 8. SOLUTIONS ANALYTICAL • USE OF TRIGONOMETRY/ GEOMETRY/ ALGEBRA • TWO METHODS (JOINT & SECTION METHODS) • THE METHODS CAN BE CUMBERSOME AND LENGTHY AND LEAD TO ERRORS • A COMPARISON ON NEXT SLIDE GRAPHICAL • USE OF CONCEPT OF ENGG DRG • USE OF SPACE, VECTOR DIAGRAM AND A LOAD TABLE • VECTOR DIAGRAM OF EACH JOINT (MAXWELL DIAGRAM) AND COMPOSITE VECTOR DIAGRAM GIVES THE SOLUTION • SELECT THE 1ST JOINT WITH 2 UNK FORCES AND THEN PROCEED TO THE NEXT JOINT • IT IS SIMPLE , EASY AND FULL PROOF • INITALLY ANALYTICAL METOD TOBE USED FOR CALCULATION OF REACTIONS
9. 9. ANALYTICAL SOLUTIONS JOINT METHOD • FORCES OF EA JOINT IS ANALYSID ONE BY ONE • SELECT A JOINT WITH 2 UNK FORCES • ANALYSE THE FORCES AT THAT JOINT MATHEMATEICALLY AND THEN PROCEED TO THE NEXT • FOR COMPLEX FRAME THIS METHOD IS VERY LONG AND CAN LEAD TO MATHEMATICAL ERRORS SECTION METHOD • THE FRAME IS CUT INTO SECTIONS • EA SECTION IS THEREAFTER ANALYSED USING FBD • MOMENTS OF EACH MEMBER W.R.T. A REF POINT IS CALCULATED AND THE FORCES ARE BVDETERMINED • SECTION LINE MUST NOT CUT MORE THAN 3 MEMBERS • IT IS VERY TEDIOUS FOR COMPLEX STRUCTURES
10. 10. LEARNING OUTCOME • Types of joints and supports • Zero force members • Material choice • Factor of safety • Design analysis • Trial and error

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Defination,Analysis of frames,stresses in frame,convention, assumptions, solutions(analytical), Learning outcomes

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