👉Soil Pressures During Seismic Events

🚧Essential Insights for Structural & Geotechnical Engineers

⏺As structural engineers, we often concentrate on forces from above, such as gravity loads, wind, and seismic forces. But what about the soil pressures acting on our structures during earthquakes and throughout a building's life? It's vital to understand how soil interacts with structures, especially when dealing with retaining walls and basements connected to the main building.

In this post, we'll look at the different types of earth pressures (at-rest, active, and passive) and explain Mononobe-Okabe method for calculating seismic soil forces on flexible walls. We'll also discuss whether this method works for so-called "stiff" walls.

Understanding Earth Pressures

• At-Rest: This happens when a structure retains soil and is stiff enough to prevent soil from moving. The pressure increases with depth, reaching its maximum at the base of the wall.

• Active: Occurs when a wall moves away from the soil, which reduces the pressure on the wall. The pressure still increases with depth, forming a triangular shape.

• Passive: Occurs when a wall moves into the soil, significantly increasing pressure. This is important for soil-structure interaction and often requires advanced analysis using nonlinear soil springs that consider the soil's different behaviour depending on load direction.

⭐️Seismic Forces due to Soil: Flexible vs. Stiff Walls

During earthquakes, soil pressures on retaining structures can increase significantly. The design approach varies depending on the wall's flexibility:

• Flexible Walls (Drift ≥ 0.4%): For walls that can move more, we assume active earth pressures behind the wall. The Mononobe-Okabe (M-O) equations expand classical earth pressure theories to include seismic forces using KₐE.

• Stiff Walls (Drift < 0.4%): For stiff walls, seismic pressures are higher than those calculated by the M-O equations. Research by Wood and Elms in the 90s shows that as wall deflection increases up to 0.4%, the earthquake pressure decreases linearly to the M-O value. The pressure distribution shifts from uniform to triangular (maximum at the base) during this range of movement.

🏷Practical Tips for Engineers

• Always consider seismic soil pressures in your load combinations during seismic design. Ignoring them can lead to underestimating loads and potential structural issues.

• How the soil and structure interact can greatly affect the forces experienced during earthquakes.

For those looking to learn more, I recommend "Seismic Design of Bridge Abutments and Retaining Walls" by Wood and Elms (1990).

Stay tuned for a future post on soil-structure interaction, where we'll cover how the relationship between soil and structure affects seismic performance.

Via Yonatan Tadesse PMP®

@etconp

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ታምራት  ፕሌት እና ጄቦልት አቅራቢ

👉ሁሉን በአንድ ቦታ የሚያገኙበት እና ለሁሉም ቅርብ

🔰ምን ይፈልጋሉ?

📌ፕሌትና ጄቦልት በፈለጉት አይነት የተዘጋጀ አለን

✂️ላሜራ ማስቆራረጥ ማስበሳት ወይንም ማሳጠፍ ከፈለጉ  እንዳያስቡ ሁሉንም ማሽኖች አስገብተናል

🔗ፌሮ (ቶንዲኖ) ጥርስ ማስበጀት ወይንም ማሳጠፍ ካሰቡ ለሱም ማሽኑ በጃችን ነዉ

📐ማንኛዉንም የሞደፊክ ስራዎችን የሚሰሩ ብቁ ባለሙያዎችም አሉን

☎️ይደዉሉልን ያማክሩን

📍ኢትዮጵያ ዉስጥ የትም እንልክሎታለን

አድራሻችን፦ 1. መርካቶ
                   ቁ.1 አየር ጤና
                    ቁ.3 ተክለሀይማኖት

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👉Sources Of Cracking In Concrete

1. Use of low-grade materials: One of the major sources is the use of lower quality materials which include both concrete and steel in reinforced concrete structures.

2. Shrinkage: Shrinkage can cause cracking if not controlled during mix design and curing stage. Shrinkage can become critical in high strength concrete because of low water/cement ratio and also because of use of Mineral Admixtures.

3. Quality and Type Of Aggregate: The quality of aggregate used in concrete determines the overall strength of concrete. If the aggregate is of poor quality it will not make a proper bond with cement.

4. Overloading of structure: Overloading of structure especially at younger age is a common source of cracking. This can happen if formwork is removed before time or more construction load is present.

5. Mistakes at design stage in office: If there are errors at design stage then it is obvious that problems will occur at site. concrete cracking is one of them.

6. Improper Curing: Another major cause of concrete cracking. If curing is not done appropriately for given time span then one should expect cracking.

7. Early Formwork Removal: If formwork is removed before concrete has achieved strength, there will be cracking.

8. Use of Congested Reinforcement in Lean Concrete: If you use heavy reinforcement in average quality concrete then stress distribution between steel and concrete can become non-linear causing cracking.

9. Mistakes at Site or during erection: Proper and trained labour and workmanship are necessary for any site work. Lack of it during concreting can cause cracking.

@etconp

👉This is how the staircase formwork will be prepared

🚧የ ደረጃ ፎርም ወርክ እንዴት እንደሚዘጋጅ ይመልከቱ

@etconp

👉የፌዴራል ቤቶች ኮርፖሬሽን ግዙፍ የግንባታ ግብዓት ማምረቻ ማዕከል አስመረቀ

የፌዴራል ቤቶች ኮርፖሬሽን በዛሬው ዕለት ጥቅምት 23 ቀን 2017 ዓ.ም ግዙፍ የግንባታ ግብዓት ማምረቻ ማዕከል አስመረቀ።

የጠቅላይ ሚኒስትር ጽ/ቤት ኃላፊና የፌዴራል ቤቶች ኮርፖሬሽን የሥራ አመራር ቦርድ ሰብሳቢ ክብርት አለምፀሐይ ጳውሎስ ፣ የፌዴራል ቤቶች ኮርፖሬሽን ዋና ሥራ አስፈፃሚ ክቡር አቶ ረሻድ ከማል እና ከፍተኛ የመንግሥት ሥራ ኃላፊዎች በተገኙበት ማዕከሉን በይፋ መርቀው ሥራ አስጀምረዋል፡፡

ማዕከሉ፣ ኮርፖሬሽኑ የጀመረውን ስኬታማ የቤት ልማት መርኀ ግብር ለማስፋፋትና አስተማማኝ ግብዓት አቅርቦት ለመፍጠር፣ የኮንስትራክሽን ዘርፉ ጥራት ያለው ግብዓት እንዲያገኝ ለማስቻልና የግብዓት ዋጋን ለማረጋጋት ታሳቢ በማደረግ የግብአት ማምረቻ ማእከሉ በአጭር ጊዜ፣ በጥራት እንዲሁም በተመጠነ በጀት በመገንባት ለምርቃት በቅቷል፡፡

በዛሬው እለት ለምረቃ የበቃው ግዙፍ ፋብሪካ አንድ ዓመት ባልሞላ ጊዜ ውስጥ ግንባታው የተጠናቀቀ ሲሆን፣ ይኸም የኮርፖሬሽኑን ፕሮጀክትን በአጭር ጊዜ አጠናቆ ወደ ሥራ የማስገባት ሂደት እየዳበረ ያለ ባህል ማሳያ እንደሆነም ተገልጿል፡፡

በራስ ገቢ ብቻ ያለምንም ብድር በአንድ ቢሊዮን ብር ወጪ ሙሉ ለሙሉ ተገንብቶ ወደ ምርት ሥራ እንዲገባ የተደረገ ፕሮጀክት መሆኑም ተጠቁሟል፡፡

የተገጠሙት ማሽኖች ቱርክ ሰራሽ ሲሆኑ፣ የፋብሪካው ተከላውም በቱርካውያን ባለሙያዎች ሲከናወን፣ ኢትዮጵያዊያን ባለሙያዎች አጭር ስልጠና አግኝተው ሙሉ በሙሉ የማምረቻ ማሽኖችን ኦፕሬት እያደረጉ መሆኑ ታውቋል፡፡

አንጋፋው አዲስ አበባ ዩኒቨርሲቲ በአማካሪነት የተሳተፈበትና ሀገር በቀሉ በኤም ቴክኖሎጂ  ደርጅት በተቋራጭነት የተከላውን ሥራ ያከናወነበት ታሪካዊ ፕሮጀክት ነው፡፡ 

ሁለት የኮንክሪት ሬዲ ሚክሰር ፋብሪካዎች እያንዳንዳቸው 100 ሜትር ኪዩብ የኮንክሪት ውህድ በሰዓት የማምረት አቅም ያላቸው ፋብሪካዎች ወደ ምርት ገብተዋል፡፡

በቀን 8 ሰአት ምርት ቢያመርት እንኳ ከዓመታዊ ምርት ሽያጭ ከ 2.29 ቢሊዮን ብር በላይ ገቢን ማግኘት ያስችላል፡፡

የብሎኬትና የመንገድ ንጣፍ ታይልስ ማምረቻ ፋብሪካ ደግሞ  የኩሊንግ ሲስተም ስላለው ለ24 ሰአት ያለማቋረጥ በፈረቃ መሥራት ይችላል፡፡

ማሽኑ በቀን ለ8 ሰአት ብቻ እንኳ ቢሰራ 9 ሺህ 072 ብሎኬቶችን በአመት ደግሞ ከ2.6 ሚሊዮን በላይ ብሎኬቶችን የሚያመርት ሲሆን በቀን ለ 8 ሰዓት (በአንድ ፈረቃ) የተመረተ ምርት ለገበያ በማቅረብ ከዓመታዊ ምርት ሽያጭ ከ182 ሚሊዮን ብር በላይ ማግኘት ያስችላል፡፡  የምርት ፈረቃውን ሁለት በማድረግ አመታዊ ሽያጩንም በእጥፍ የማሳደግ ዓቅም አለው፡፡

ይህ ፋብሪካ ለመንገድ ንጣፍ የሚሆኑ ታይልሶች በብዛት እና በጥራት የማምረት ተጨማሪ አቅም ያለው ነው፡፡

አስተማማኝ የጥሬ እቃ አቅርቦቱ እንዲኖር  የጠጠር ምርት እና የጥቁር ድንጋይ ካባ ከኦሮሚያ ክልል ሰሜን ሽዋ ዞን አሌልቱ አካባቢ እንዲሁም የፑሚስ ማምረቻ ካባን ደግሞ በምስራቅ ሸዋ ዞን አደአ ወረዳ የማምረቻ ፈቃድ ከኦሮሚያ ክልል ወስዶ ለፋብሪካው አስተማማኝ ግብዓት እያቀረበ ነው፡፡

የዚህ ማእከል ይዞታ ስፋት ከ4 ሄክታር ወደ 14 ሄክታር በማሳደግ በየቦታው ተበታትኖ የሚገኙትን የኮርፖሬሽኑ የእንጨት፣ የብረት፣ የመስታወት የአልሙኒየም እና የሊፍት ወርክሾፖቻችን ወደዚህ ማእከል ጠቅለው እንዲገቡ ተደርጓል፡፡

ከዚህም ባሻገር ከኮርፖሬሽኑ አልፎ ለሀገራችን የግንባታ ኢንዱስትሪ ትልቅ ለውጥ ያመጣል ተብሎ የታመነበት በጣሊያን ሀገር እና በሌሎች ሀገሮች ተሞክሮ ረዣዥም እና ወጥ ህንፃዎችን በጥራት መገንባት የሚያስችለው ‹‹የ pre-fab›› ማምረቻ ፋብሪካ በዚሁ ማእከል ለመትከል አስፈላጊው የቅድመ ዝግጅት ሥራ እየተከናወነ ነው፡፡

@etconp

👉Project Control Techniques for Successful Project Management

💫In the world of project management, having the right control techniques can make all the difference between a project that meets goals and one that veers off track. Here are some of the top techniques to ensure projects stay on schedule, within budget, and aligned with quality standards:

1️⃣ Earned Value Management (EVM): Evaluate project performance by comparing planned work vs. actual progress and costs.

2️⃣ Critical Path Method (CPM): Identify the essential tasks impacting project timelines to prioritize resources effectively.

3️⃣ Gantt Charts: Use visual timelines to track task progress and spot any delays.

4️⃣ Work Breakdown Structure (WBS): Break down projects into manageable tasks for clear assignments and better cost estimation.

5️⃣ Risk Management: Proactively identify and manage risks to mitigate issues before they impact the project.

6️⃣ Change Control: Keep the project aligned by managing scope, schedule, and budget changes systematically.

7️⃣ Cost Control: Monitor expenses and adjust to prevent budget overruns with variance analysis and forecasting.

8️⃣ Quality Control: Regular testing, audits, and inspections to ensure deliverables meet defined standards.

9️⃣ Resource Allocation & Leveling: Optimize resource usage to avoid overload and maintain efficiency.

🔟 Milestone Tracking: Track key milestones to ensure significant project stages are completed on time.

Project control techniques are essential for staying on track and delivering value. By combining these methods, project managers can make informed adjustments and ensure project success!

Via Yonatan Tadesse PMP

@etconp

👉በአዲስ አበባ ከፍተኛ የእግረኞች ዝውውር ከሚታይባቸው ቦታዎች መካከል የመገናኛ አደባባይ በቀዳሚነት ይጠቀሳል።

🚧በዚህ አደባባይ በተለይ በሠራተኛ መግቢያና መውጪያ ሰአቶች በአደባባዩ ለመተላለፍ አዳጋች የሚሆኑባቸው ጊዜያት ብዙ ነው።

💫ይህንን ችግር ለመቅረፍ መገናኛን እና የአካባቢውን መልክን የሚቀይር የእግረኞች የመሬት ውስጥ ለውስጥ መሸጋገሪያ መንገድ ግንባታ እየተካሄደ ነው።

@etconp