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THE ENGINEERING OF FOUNDATIONS A BOOK BY RODRIGO SALGADO POWERPOINT RESOURCES FOR CHAPTER 2 Contains copyrighted material.

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Presentation on theme: "THE ENGINEERING OF FOUNDATIONS A BOOK BY RODRIGO SALGADO POWERPOINT RESOURCES FOR CHAPTER 2 Contains copyrighted material."— Presentation transcript:

1 THE ENGINEERING OF FOUNDATIONS A BOOK BY RODRIGO SALGADO POWERPOINT RESOURCES FOR CHAPTER 2 Contains copyrighted material

2 THE DESIGN PROCESS

3 DESIGN GOALS Safety Serviceability Economy The optimum foundation solution transfers the superstructure loads to the ground in a way that minimizes cost (construction and maintenance) over the life of the structures without sacrificing safety or performance

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5 RELIABILITY-BASED DESIGN

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7 LIMIT STATES DESIGN AND WORKING STRESS DESIGN

8 TYPES OF LIMIT STATES ULTIMATE LIMIT STATES (ULS) : states at which a potentially unsafe/dangerous condi tion is reached (typically structural failure, collapse, etc.) SERVICEABILITY LIMIT STATES (SLS) : states at which the structure or facility ceases to p erform as intended without loss of safety

9 Limit State Nature of Limit StateConsequences IA-1Classical bearing capacity failure (ULS) Excessive movement/collapse of foundation causes serious damage, partial collapse or complete collapse of structure IA-2Structural failure of foundation element (ULS) Column is inadequately supported by foundation element, punching through it; this causes serious damage, partial or complete collapse of superstructure IBExcessive differential foundation settlement (ULS) Excessive differential settlements create excessive additional loads in the structure, leading to structural damage IIExcessive settlement (total or differential) (SLS) Excessive settlements lead to serviceability problems, such as access problems, damage to architectural finishings, etc. IIIStability failure of the whole foundation system or a subset thereof Collapse mechanism develops that encompass the foundations for the building or structure or a part of the foundations (a classical example would be stability failure of a slope on top of which is founded a building) Limit states for shallow foundation design

10 Working Stress Design Ultimate load: the load that would lead to an ultimate limit state Factor of Safety (FS) Ultimate load Allowable load Design load All load and resistance uncertainities are lumped in this single factor Design or working load: the sum of the loads under consideration (unfactored)

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12 ULTIMATE LIMIT STATES: LOAD AND RESISTANCE FACTOR DESIGN

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14 TOLERABLE FOUNDATION MOVEMENTS

15 Uniform Total Settlement Non-Uniform Settlement Tilting Types of Settlement

16 Uniform Total Settlement No structural damage Damage at interface with utilities Access problems Drainage problems

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18 Non-Uniform Settlement Structural –Cracking of beams/slabs/column Architectural –Cracking of panel walls –Door/window jamming –Uneven Floors Damage at interface with utility lines Access and drainage problems Excessive Tilting

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22 Cracks Caused by Foundation Movement May have any direction, depending on the direction of the tensile strain (cracks are  to the tensile strain) At a specific point of the structure, cracks have the same direction (contrast that with the web pattern observed in the case of shrinkage and drying) Appear on both sides of an element

23 Typical Building Structures Load Bearing Walls Frames

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