1.3 - Site Selection and Building Composition
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Importance of Site Selection
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Today, let’s talk about **site selection**, which is crucial when we approach construction in areas that are prone to disasters. What are some of the things we need to consider?
Maybe we should look at the ground stability? Like, if it’s on a hill or steep slope?
Exactly! **Avoiding steep slopes** is vital to mitigate risks of landslides. Now, what about the type of soil we're building on?
We shouldn't use filled soil, right? It’s not stable enough for foundations?
Correct! Building on filled soil can lead to foundation collapse during earthquakes. Let’s remember that: Safe Foundations Save Lives! What else should we think about?
How about the distance from other buildings? If they're too close, there could be serious damage!
Absolutely right! That’s why maintaining adequate separation between structures is a significant guideline. Great job, everyone. Reiterate: Stability, Separation, Safety!
Building Composition Considerations
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Now let's shift our focus to **building composition**. What do you think about building shapes in earthquake-prone areas?
We should avoid asymmetrical buildings since they can twist or turn during earthquakes, right?
Exactly! Symmetrical structures are generally safer. Can anyone describe what happens to slender buildings during an earthquake?
They’re more likely to topple over because they swaying too much, aren’t they?
Great point! Slender buildings lack stability and should be avoided. Now, remember the saying: **'Short, Sturdy, and Symmetrical** for safety! What about building features like overhangs?
Those can attract more force during an earthquake—so smaller overhangs are better?
Correct! Larger overhangs can cause instability. So, let’s summarize: **Shape, Size, Strength!**
Guidelines for Construction Material and Design
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Finally, let's look at construction materials and reinforcement design. What do you think is important regarding building reinforcements?
They need to be strong enough to withstand seismic forces, right? Like steel is often used.
Exactly! For instance, **RCC frames** require specific gap maintenance to prevent collision. What’s that minimum gap?
I think it’s 20 mm for RCC frames?
Spot on! And for steel frames, it's even more: 30 mm. Now, how about the mass distribution at the top of a building?
Heavy masses should be avoided since they can shift the center of gravity and cause collapse.
That’s a fantastic point! **Remember**: Heavy additions above can lead to heavy consequences. Overall, balance in design is key!
Introduction & Overview
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Quick Overview
Standard
The section discusses various guidelines for site selection, building composition, and structural integrity in disaster-prone areas. It highlights the importance of considering factors such as building asymmetry, soil types, and environmental conditions to ensure safety and functionality in the built environment.
Detailed
Site Selection and Building Composition
In addressing disaster recovery and resilience, effective site selection and appropriate building composition are critical components. This section emphasizes guidelines that must be adhered to for construction in disaster-prone areas.
Key Guidelines for Site Selection
- Avoid Steep Slopes: Buildings should be located sufficient distance away from steep slopes to reduce risks associated with landslides.
- Foundation Stability: The use of filled soil for foundations poses risks that can lead to collapse during an earthquake, thus caution is advised.
- Avoid Slender Structures: Buildings with a height-to-width ratio greater than four are encouraged to be avoided, especially those resembling inverted pendulums which are inherently unstable.
Essential Building Composition Principles
- Plan Form Symmetry: Asymmetrical buildings experience torsion during seismic events; hence, symmetry is crucial.
- Managing Overhangs: Large projections or overhangs on buildings attract significant earthquake forces.
- Gap Maintenance: When constructing dissimilar structures, adequate separation must be maintained to avoid collision during seismic movement (e.g., at least 15 mm for load-bearing and up to 30 mm for steel frame structures).
- Mass Distribution: Avoid heavy masses at the top of structures to prevent instability during seismic activity.
These principles aim to ensure the safety of structures and the people occupying them when faced with various natural disasters, advocating for a consensus between regulatory building bylaws and seismic safety guidance.
Audio Book
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Guidelines for Earthquake Resistance
Chapter 1 of 5
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Chapter Content
For example, this was a kind of guidelines which have been developed for earthquake resistant design and detailing... they are recommending that try to avoid the asymmetrical compositions in earthquake-prone areas.
Detailed Explanation
This chunk discusses guidelines provided to architects and engineers for designing earthquake-resistant structures. One major recommendation is to avoid asymmetrical arrangements of buildings. Asymmetrical buildings can become unstable during an earthquake because they may experience torsion, causing stress at the corners where many past earthquake damages have occurred. The chunk emphasizes the importance of stable building composition to enhance safety.
Examples & Analogies
Imagine trying to balance a pencil on your finger. If the pencil is perfectly straight, it’s easier to keep it balanced, just like a symmetrical building. But if you tilt it to one side, it becomes much harder to balance—much like an asymmetric building during an earthquake.
Site Selection Considerations
Chapter 2 of 5
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Chapter Content
Some of the other guidelines they talk on the site selection... try to avoid the steep slopes and also in many cases what they do is; when you are cutting down and filling the soil...
Detailed Explanation
This chunk highlights the importance of careful site selection for buildings, particularly in areas prone to earthquakes. It advises against constructing near steep slopes to avoid potential landslides. Furthermore, it warns against using filled soil for foundations because it can lead to instability. The guidance suggests maintaining proportional ratios between height and breadth to prevent slender, unstable structures that can't effectively handle earthquake forces.
Examples & Analogies
Think about building a tower of cards. If you place it on a wobbly surface or near a steep edge, it’s likely to fall. The same applies to buildings; choosing a stable, secure site is crucial for safety.
Building Composition and Proportions
Chapter 3 of 5
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Chapter Content
they also suggest that very slender building should be avoided so, they also talk about the ratio... height and breadth should be less than four and also the inverted pendulum type buildings are unstable...
Detailed Explanation
The guidelines specify that buildings should not be too tall and slender. A ratio of height to breadth greater than four can lead to instability. Instead, it is recommended to design buildings with a more pyramidal shape, distributing weight effectively and resisting lateral forces from winds and earthquakes. For instance, inverse pendulum shapes are not suggested because they increase the risk of tipping over.
Examples & Analogies
Picture a tall, skinny flagpole; it sways easily in the wind, increasing the risk it may break. Meanwhile, a wider, shorter pole is more stable. This mirrors how building proportions can affect stability during earthquakes.
Lateral Stiffness and Building Features
Chapter 4 of 5
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similarly, when we say about the sudden change of lateral stiffness should be avoided... large overhangs and projects attract large earthquake forces.
Detailed Explanation
This section explains that sudden changes in a building’s stiffness (how resistant it is to bending) should be avoided to prevent structural failure during earthquakes. It warns against features such as large overhangs that can create imbalance and attract greater forces during seismic events. Ensuring a uniform distribution of support and resistance is essential for maintaining building integrity.
Examples & Analogies
Imagine a seesaw. If one side suddenly has much more weight than the other, it tips and could cause someone to fall off. Similarly, buildings need to manage weight and strength equally across their structures to withstand earthquakes.
Separation of Dissimilar Buildings
Chapter 5 of 5
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Chapter Content
the separation of dissimilar buildings... at least 15 mm gap should be left because in order to avoid the collision between these dissimilar buildings.
Detailed Explanation
The guidelines advise leaving appropriate gaps between buildings of different structural types to prevent them from colliding during an earthquake. The recommended minimum gaps vary based on the type of structures involved—this is crucial to ensure that if one building begins to sway, it does not directly impact its neighbor. This separation is key in reducing potential damage during seismic events.
Examples & Analogies
Think of two people dancing next to each other. If they don’t leave some space between them, they might accidentally bump into each other, which could lead to a fall. Likewise, buildings need space to move independently, especially during an earthquake.
Key Concepts
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Site selection should prioritize safety regarding geological conditions and proximity to hazards.
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Asymmetrical buildings are more vulnerable to torsion during seismic events.
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Foundation stability is crucial; using filled soil for foundations is discouraged.
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Proper mass distribution in buildings prevents collapse during earthquakes.
Examples & Applications
In designing buildings in earthquake zones, utilizing symmetrical shapes can significantly reduce the risk of structural failure.
Building near a steep slope can lead to increased risks of landslides during tremors, necessitating distance from such areas.
Memory Aids
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Rhymes
For a sturdy structure, shape should be symmetric, to resist the quake's dynamic.
Stories
Imagine a building that stands tall and proud, but oh no! The earthquake comes and it wobbles, crumbles, falls. If only it was built square and not like an uneven wall!
Memory Tools
S.O.S. for site selection: Stay Away from Steep slopes.
Acronyms
F.A.S.T. for building design
Foundation
Asymmetry
Stability
Torsion.
Flash Cards
Glossary
- Asymmetrical Buildings
Buildings lacking symmetry and balanced proportions, which are more prone to torsional movements in earthquakes.
- Site Selection
The process of evaluating and choosing a location for construction based on various risk factors.
- Foundation Stability
The ability of a building's foundation to support its structure without risk of failing or collapsing.
- LoadBearing Structures
Structures designed to support loads from above, ensuring stability against natural forces.
Reference links
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