👉 ኣሁን ደሞ ስለ Foundation (መሠረት) ትንሽ እንበል...
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✔Shallow Foundation-እነዚህን ፋውንዴሽኖች የምንጠቀመው አፈሩ ብዙም ሳይቆፈር በቅርብ ጥልቀት ጠንካራ የአፈር ሁኔታ ካለ ነው፡፡ ለመገንባት ትልልቅ ማሺኖች አያስፈልጉም ብዙ ችሎታም አይጠይቁም::
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Spread/ Pad/ Isolated Footing - አንድ ኮለን ብቻ ነው
support የሚያደርጉት- የሚመጣውን ፎርስ eccentricity መሰረት በማድረግ circular/ rectangular or square የሆነ ቅርፅ ሊኖራቸው ይችላል፡፡ ያለፌሮ ሊገነቡ ይችላሉ ለምሳሌ ፓዱን slopped በማድረግ::
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Combined Footing - ሁለትና ከዛ በላይ ኮለኖችን በአንድ ፓድ
support ለማድረግ ነው የምንጠቀምባቸው፡፡ እነዚህን
የምንጠቀመው ሁለት ተቀራራቢ Isolated Footing ካሉ ሁለቱን
አንድ ላይ combine በማድረግ ኮንክሪትም ፌሮም ሴቭ ማድረግ
እንችላለን፡፡ በተጨማሪም isolated ለመጠቀም property
limit ካለ እነዚህን መጠቀም እንችላለን:: 2 አይነት Combined
Footing አሉ- እነርሱም ፡-
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1. Rectangular Combined Footing – ይህንን የምንጠቀመው ሁለቱም ኮለኖች የሚሸከሙት ሎድ ተቀራራቢ
ወይም እኩል ከሆነ ወይም ትራፖዞይዳል ለመጠቀም የስፋት
ገደብ ካለ ነው።
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2. Trapezoidal Combined Footing - ሁለቱ ኮለኖች የሚሸከሙት ሎድ ልዩነት የተጋነነ ከሆነ ነው።
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Strap/ Cantilever Footing - ሁለት ፓዶችን በቢም በማያያዝ
ሎድ ከአንዱ ፓድ ወደሌላው እንዲተላለፍ ማድረግ እንችላለን፡፡
ቢሙ በራሱ ሎድ አይሸከምም ሎድ ያስተላልፋል
እንጂ…….እነዚህን የምንጠቀመው ኮለኖቹ ከ7 ሜትር በላይ ከተራራቁ combined footing ብንጠቀም ኢኮኖሚካል ስለማንሆን ፓዶቹን በቢም በማያያዝ እንደ combined footing
ልንጠቀምባቸው እንችላለን፡፡
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Mat/ Raft foundation - እነዚህን የምንጠቀመው መሬቱ
የመሸከም አቅሙ ትንሽ ከሆነና spread footing ስንጠቀም
የህንጸውን ስፋት ከ50 ፐርሰንት በላይ ከሸፈኑት ነው ….. አንዳንዴ
ግን spread footing ከ50 ፐርሰንት በላይ ቢሸፍኑትም ለ
spread footing negative reinforcement ስለማንጠቀም ከ Mat ይልቅ ኢኮኖሚካል ሊሆኑ ይችላሉ - ምክንያቱም Mat
negative & positive reinforcement ይጠቀማሉ፡፡ ማን ኢኮኖሚካል እንደሆነ ቼክ ማድረግ የኢንጅነሩ ድርሻ ነው፡፡
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👉ሼር በማድረግ ለሁሉም ያጋሩ።

✔Points...
The d/n b/n spacer and concrete cover is that,,
Spacer is used to know the thickness of concrete cover It produced before concrete work of column,beam or slab starts or during reinforcements work.
No more attention given to Quality and mix ratio.
Care only given to thickness of the spacer.
But concrete cover is amass of concrete used to cover the reinforcement bar.
Quality, mix ratio and other important considerable measures taken during concrete covering work.

👉Mat(raft) foundation

➡️Commonly two types of mat foundation are available.

✅Ribbed mat( beam and slab mat)

✅solid mat ( flat slab mat )

➡️ Ribbed mat can be described simply as an inverted solid slab subjected to bearing pressure as load.

➡️ solid mat( uniform depth mat ) can be described as a flat slab subjected to bearing pressure as load.

ѕнєαя ƒαιℓυяє

👉shear failure is sudden and brittle failure. The failure is with diagonal cracks occuring some distance from the face of support.

👉on any given section shear and flexure occur at the same time( except point with either shear or moment is zero). The interaction of the two stresses, if the principle of stress transformation is followed, develop tension and shear at an angle different from 0 or 90°.

👉The diagonal tension resulting from interaction of shear and flexure is responsible for shear failure.

👉beams without shear reinforcement faile in one of the five modes:

☑️diagonal tension

☑️shear compression

☑️shear tension

☑️web crushing and

☑️arch rib failure.

👉The failure mode likely to occur depends on:

☑️moment to shear ratio( M/V),

☑️ type of loading(concentrated or distributed)

☑️beam cross section.

👉 concrete without shear reinforcement resists shear by the contribution of:
☑️concrete uncracked section,

☑️aggregate interlock and

☑️due to dowel action of longitudinal reinforcement.