A wide array of reinforced concrete design examples

This construction article is based on various reinforced concrete design examples. You will be familiar with flexural analysis of beam.

Given below, various examples and their solutions :-
Make proper calculation for the following reinforced concrete sections :-

Example 1 : The balanced steel reinforcement: The maximum steel reinforcement area for a tension-controlled and transition section per ACI code 318-11.

The location of the neutral axis and the depth of the equivalent compressive Whitney stress block for the tension-controlled section in B.

Here, the compressive strength is given as f'c = 4 ksi and yield strength is given as Fy = 60 ksi

ACI code 318-11 is followed

Example 2 : Examine the adequacy of a rectangular tension controlled section on the basis of dead and live loads.

A 10 ft long cantilever beam contains a rectangular section and reinforcement. The beam bears a dead load of 2 k/ft (along with self weight) and a live load of 1 k/ft.

The compressive strength is provided as f'c = 4 ksi and yield strength is fy = 60 ksi, verify if the beam has sufficient strength to bear the provided loads with ACI Code 318-11.

Example 3 : Work out the design moment strength and the location of the neutral axis of a rectangular section containing two rows of tension reinforcement.

b (width) is given as 13 inches
d is given as 23.5
h (through depth of the section) is given as 27 inches
dt (distance from the extreme compression fibre to the location of the extreme tension reinforcement) is given as 24.5

f'c (the compressive strength) is given as 4 ksi
fy (the yield strength) is given as 60 ksi

Example 4 : Work out the design moment strength and the position of the neutral axis of a rectangular section with compression reinforcement that yields.

The following properties are included in the rectangular section :-
Width = b = 12"
Effective depth = d = 22.5"
Tension reinforcement = (6) no. 9 bars
Compression reinforcement = (2) no. 6 bars

Compute the design strength of the beam if f'c = 4 ksi and fy = 50 ksi with ACI Code 318-11.

To get the solutions of the above-mentioned problems, go through the following link. www.engineeringexamples.net

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Published By

Rajib Dey

www.constructioncost.co

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Post-tensioning and its phases

The ducts for the tendons (or strands) are arranged together with the reinforcement prior to the casting of concrete in post-tensioning systems.

The tendons are arranged in the ducts as soon as the casting of concrete is completed. The objective of duct is to avoid connection among concrete and the tendons throughout the tensioning operation.

Contrary to pre-tensioning, the tendons are pulled with the reaction that operates against the hardened concrete. It is defined as bonded post-tensioning when the ducts are filled with grout. The grout belongs to a neat cement paste or a sand-cement mortar that comprises of proper admixture.

In unbonded post-tensioning, the ducts are not at all grouted and the tendon is set in tension individually with the end anchorages. In the sketch given below, there is a schematic illustration of a grouted post-tensioned member. The profile of the duct is based on the support conditions. For a simply supported member, the duct contains a sagging profile among the ends. For a continuous member, the duct bends in the space and hogs over the support.

The following figures demonstrate the assessment of ducts in a box girder of a simply supported bridge. The second image demonstrates the end of the box girder as soon as the post-tensioning of some tendons is completed.

Given below, the different phases of the post-tensioning operation :-

1) Casting of concrete.
2) Arrangement of the tendons.
3) Arrangement of the anchorage block and jack.

4) Use tension to the tendons.
5) Seating of the wedges.
6) Cutting of the tendons.

The stages are demonstrates schematically in the following figures. Once a tendon is anchored at one end, the tension is employed at the other end with a jack.

The tensioning of tendons and pre-compression of concrete happen concurrently. A system of self-equilibrating forces forms once the tendons are expanded.

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Published By
Rajib Dey
www.constructioncost.co
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