Structural project construction FROM A TO Z

 

Structural project construction FROM A TO Z

1.     1. Introduction

In this project, you will learn all the steps of construction of “Chamsine Bakery” starting from the soil tests and site excavation to the construction of the slabs. During any construction project, you will face many problems and learn how to think in a smart way to find the best solution to all these problems.

·       Presentation of the project:

It is a construction of 2 buildings:

The first one (Block A) has 3 floors + 1 roof.

The second one (Block B) has 2 floors + 1 roof + 1underground.

·       Project location: The project is located in Tripoli, north of Lebanon, Kalamoun highway (Kal 1692) (Fig.1, fig.2).

Figure 1: 3D view of the project

Figure 2: 3d view 2 of the project.

·       First, take the drawing from the architect.

Figure 3: Cad drawing from an architect.

·       Then draw, using AutoCAD, the columns and the beams that should be built up.

·       The next step is to import the modified cad file (fig.4) and all the given data into the "ETABS" software then export each slab to the “SAFE” software to obtain the reinforcement in each structural element (fig.5). You can see the "Structural Project" blog post, for more information about structural analysis.

Figure 4: Modified cad file containing only the columns and beams.

Figure 5: Safe file.

Figure 6: Site excavation. You can see the high depth of excavation because there is an underground in block B. You can also see the good strata (Hight strength soil).

           2. Site investigation and excavation:

2.1.Soil tests were made before starting the excavation, at Sana Engineer in Beirut, and the results were: good soil type.

2.2. A surveying engineer was responsible to:

    - Take the borders and specify the limitation points of the building.       

    - Plot the points of excavation on the ground.

    - Take the level of the road and of the ground and make them of the same level in blocks A and B.

            2.3. Take the underground level in block B.

2.4. Excavation:

-  In block B: excavation of the underground that is = 530 cm = 5.35 m (underground floor = 4.8m = 480cm + mat foundation = 45cm + cleanness concrete layer = 10cm) and 1m more than the borders of the underground from left and right in 4 sides.

- In block A: footing excavation = 115cm (footing depth=50cm + 40cm tie beam + 15cm floor + cleanness concrete layer=10cm)

Figure 7: Mat reinforcement and dowels reinforcement…

You can see in this figure that the mat reinforcement is 2-way steel, top, and bottom, 14mm diameter, and it is above the ground of a concrete cover = 50 mm. This steel is put after casting a 10 mm cleanness concrete. You can also see the blue waterproof that is between the 2  reinforcement bars of the wall.

Figure 8: Mat foundation and waterproof in the underground of block B. You can see in this figure the wood contour that must be done for safety and to specify the boundary that should be cast.

Figure 9: The connection between the elevator and the strip footing.

Figure 10: Waterproof between wall and strip footing reinforcement.

Figure 11: Stairs reinforcement in the strip footing.

Figure 12: Column reinforcement in strip footing (Block B). You can see the spacers of 5 cm that allow a good concrete cover, and the seats that allow spacing between top and bottom steel layers.

Figure 13: Soil fill after the concrete curing of the foundation in block A.

Figure 14: The soil fill depth should covers the column neck.

Figure 15: Soil fills after concrete curing in the footing. We can see the column reinforcements that are ready to be put in the column place in the next step.

Figure 16: Tie beam. It will be cast after soil fill. Then fill the voids with soil before casting the floor.

Figure 17: New continuous footings in block A. These footings are done after casting all the other footings, because of a modification in the construction after that the contractor decided to remove a column from block A due to architectural causes.

Figure 18: New footings in the same place as the casted footings to increase the capacity of the columns.

Figure 19: Tie beam in the footing.

Figure 20: The beginning of casting the continuous footings.

Figure 21: Continuous footing in block A ,after removing the middle column, to increase the capacity of the other columns.

Figure 22: Casting the underground floor.

3.  Steps of construction:

3.1. The first step is the cleanness concrete layer = 10 cm in blocks A and B

3.2. 2^nd step: axis of columns in blocks A and B

3.3. 3^rd step: Foundation reinforcement:

§  In block A: isolated footing, use 2-way bottom steel.

§  And mat foundation in block B is 2-way steel, top and bottom of 14mm diameter.

You can see a comparision between the mat foundation and the isolated foundation in the "Footing design" blog post.

3.4.Then add in block B, a waterproof of 20cm: 10 cm in the mat foundation and 10 cm in the wall.

Figure 23: Shear wall reinforcement in block B.

3.5. Add retaining walls along the contour of the underground of block B because the soil is around the building. These walls have a height of 4.8m= height of underground. They are subjected to soil load from the outside and are connected to the slab at the top (simply supported) and to the strip foundation at the bottom (fixed). So the main reinforcement is on the inside (in the side of the building not on the side of the soil) and add also reinforcement at support using fixed connection because of the negative moment.

3.6. Add shear walls in blocks A and B on the perimeter of the elevator.

3.7. The column reinforcements are calculated using “Etabs”. And the slab reinforcements are calculated using “Safe”. All the columns are square so use square foundations for isolated footings in block A.

3.8. When putting the column reinforcements in their place, the column must be vertical so it should be leveled using the suitable tool containing mercury.

3.9. Put each column in its place then put a wood cover to cast the columns.

4.     Types of slabs:

a.      In block A, and because of removing a column from the middle, there is a large span, so use the post-tension 2-way solid slab to have a small beam section with a big capacity.

Post-tensioning is done onsite by installing post-tensioning tendons within the concrete form-work in the same method of installing rebar, then tension the bars using a special tool (Fig. 27).

When the steel is tensioned before concrete placement, the process is called pre-tensioning. When the steel is tensioned after concrete placement, the process is called post-tensioning.

The main advantages of post-tensioned reinforced concrete slab are:

- Increasing clear spans.
- Thinner slabs.
- Lighter structures.
- Reducing cracking and deflections.
- Reducing story height.
- Rapid construction.

Figure 24: Post tension cover steel.

Figure 25: Post tension steel.

Figure 26: 2-way post-tension slab.

Figure 27: Tensioning the steel.

 b. In block B, use the 1-way solid slab only in the part of the underground that is subjected to cars load. And in all other slabs of block B, use the 1-way ribbed slab.

Figure 28: 1-way ribbed slab in block B.

Figure 29: Last photo taken for block A.

Figure 30: Last photo taken for block B.

5.     Conclusion:

This project is one of the best and most important experiences in which you can learn how to deal with new problems, and how to use your known information correctly to solve all the difficulties. And to be a good and special engineer you have to follow new projects to gain as much as possible of experiences.