1. Prestressed and Reinforced Masonry Design-CE 434/534-Spring 2006
Instructor: Mohamed ElGawady, Ph.D.
Lectures: Tu, and Th Noon:1:15
Office: Sloan Hall, Room 117
Office hours: 1:15 - 2:15 pm Tu and Th
1:30 – 2:30 pm F
TA: 2 – 3 pm M and W
Homework policy: Two late assignments without penalty
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2. 1- Introduction Masonry is a widespread construction material. USA
Canada
USA
Europe
Australia
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3. Masonry is one of the oldest construction material
Masonry is one of the oldest construction material. Masonry structures have been in existence since the earliest days of mankind. Clay units have been in use for over 10,000 years.
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4. The tallest structure in the world until the 20th century
The tallest structure in the world until the 20th century
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5. Use of sun-dried mud in Ziggurat, Ur, Iraq 2600 B.C.
Use of sun-dried mud in Ziggurat, Ur, Iraq 2600 B.C.
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6. Use of sun-dried mud in Ziggurat, Ur, Iraq 2600 B.C.
Use of sun-dried mud in Ziggurat, Ur, Iraq 2600 B.C.
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7. Use of stone lintel in Lion, Greece 1250 B.C.
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8.
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10.
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11. Now, the question is why arches?
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12. The last thing is to talk about thrust line in walls
The last thing is to talk about thrust line in walls. Under vertical loads only, the thrust line will be approximately the wall centerline. Under lateral loads (e.g. wind), the thrust line will move and there are 3 possibilities: the wind is small and the wall is safe; the wind moves the thrust line outside the wall and it turnover; the thrust is too much and masonry at the base has a compression failure.
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13. 17-Story, Park Mayfair East, CO
In the 20 century, multistory masonry structures have been built in Europe and the US
18-Story, Zurich
16-Story, Grenchen
14-Story, Lucerne
17-Story, Park Mayfair East, CO
8-Story, D.C.
11-Story, MI
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14. ©Doug Abel, Leonard Masonry Inc
Masonry can be used as the main structural element (photo on the right) either reinforced or unreinforced as we will see later. Masonry also can be used to fill steel or reinforced concrete frames. In this case the main structural element is the frame. However, the masonry modify the structure characteristics such as stiffness, frequency, etc.
©Doug Abel, Leonard Masonry Inc
URM
Infill
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15. Masonry can be used as nonstructural element as in the case of veneer walls. In this case, masonry is “covering” for another wall. During earthquake such “cover” may fall down causing significant losses.
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16. 1.1- Advantages
The versatility and visual appeal (Texture, colors, and patterns)
Masonry has a high thermal inertia. That means masonry wall is slow either to heat up or cool down. This is an ideal choice for places where there is a mild change in day and night temperatures.
Brick typically will not require painting and so can provide a structure with reduced life-cycle costs.
The appearance, especially when well crafted, can impart an impression of solidity and permanence.
Good fire protection (noncombustible).
Good sound insulation (rough surface, high porosity)
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17. 1.2- Disadvantages
Moisture (ground water can soak and rise up by capillary action, water vapor in the air can infiltrate, rain penetration under high wind). These phenomena are accompanied by efflorescence.
Dry/wet cycles
Extreme weather may cause degradation of the surface due to frost damage (specially with clay).
Masonry must be built upon a firm foundation to avoid cracking due to potential differential settlement.
The high mass increases seismic demand.
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18. 2- Masonry Components
In general, masonry elements are consisting of masonry units and mortar. (Nowadays, there exist dry joints). In the next slides we will have a general idea about materials that have been used for fabricating masonry units, typical dimensions for units, and mortar fabrication.
Brick unit
Mortar Joint
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19. 1.3- Masonry Common Materials
Clay Units
Clay units are made of mud or clay mixed with water and pouring in a mold. Now the manufacture is completely mechanized
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20. BIA Technical note # 41
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22. The units are available based on a 4 x 4 in. module.
With increasing units size and using reinforcement, hollow clay brick units were developed.
Hollow brick have a void area between % of the gross cross-sectional area of the unit.
The units are available based on a 4 x 4 in. module.
The actual size is 3/8’’ smaller than the nominal dimensions WHY?
If area of a “void” is less than 1.5 in2, then it is called core, otherwise called cell. If Anet greater than 75% Agross then Anet=Agross why?
1-keying
2-uniform drying and shrinkage
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23. 1.3.2- Concrete Masonry Units
Concrete masonry units CMU were made of high quality cement. However, it was heavy to handle and unpopular. Nowadays, they are made of Portland cement, sand, and aggregate.
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24. 1.3.3- Calcium Silicate Units
3- Calcium silicate were made of sand, lime, and water pouring in a mold and allowing them to dry in air, steam, pressurized steam.
Stone Masonry Units
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25. Stone was the first type of masonry units
Stone was the first type of masonry units. It was started with crude units; then, polygonal and squared unites was developed. Currently, most of the stonework is a thin nonstructural veneer.
1.4- Mortar
Mortar is used to bond masonry units together as well as steel reinforcement to masonry units so a composite assemblage is created that will resist the imposed loads and weather.
It provides uniform bearing between units.
Accommodate size variance in masonry units
Seal joints to slow down moisture/air penetration
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