For the section shown, use Whitney's rectangular block to calculate a, ß1 and c, determine the values of &t and 9, and ■ calculate the flexural design strength oMn Use normal weight concrete with f'c = 4000 psi and Ec = 3600 ksi, and Grade 60 steel (fy = 60,000 psi, Es=29,000 ksi). 25 in. 30 in. 6 #9 -16 in.- 2 in. 2in.

Structural Analysis
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ISBN:9781337630931
Author:KASSIMALI, Aslam.
Publisher:KASSIMALI, Aslam.
Chapter2: Loads On Structures
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### Structural Engineering Problem: Calculating Flexural Design Strength

#### Objective:

For the section shown, use Whitney’s rectangular block to:
- Calculate \( a \), \( \beta_1 \), and \( c \),
- Determine the values of \( \epsilon_t \) and \( \phi \),
- Calculate the flexural design strength \( \phi M_n \).

#### Given Parameters:

- Use normal weight concrete with \( f'_c = 4000 \text{ psi} \) and \( E_c = 3600 \text{ ksi} \),
- Grade 60 steel (\( f_y = 60,000 \text{ psi} \), \( E_s = 29,000 \text{ ksi} \)).

#### Diagram Description:

A rectangular cross-section is illustrated as follows:
- The width of the section is 16 inches.
- The overall height of the section is 30 inches.
- There are 6 reinforcement bars depicted as circles, each labeled as #9.
- The depth of concrete cover from the top and the bottom of the section to the reinforcement is \( 2 \frac{1}{2} \) inches.
- The depth to the centroid of the reinforcement steel bars is specified as 25 inches from the top.

#### Detailed Steps for Calculation:

1. **Determine the depth parameters \( a \), \( \beta_1 \), and \( c \):
   - Use the given concrete and steel properties and refer to the respective codes or standards to determine these values.

2. **Calculate \( \epsilon_t \) and \( \phi \):
   - Utilize strain compatibility and force equilibrium methods to determine the tensile strain \( \epsilon_t \).
   - Use appropriate design codes to find the strength reduction factor \( \phi \).

3. **Compute the flexural design strength \( \phi M_n \):
   - Apply the calculated values into the design equations to find the nominal moment capacity and multiply by \( \phi \) to obtain the flexural design strength.

#### References:
- Structural engineering design codes (e.g., ACI 318).

This problem helps in understanding how to apply fundamental principles of reinforced concrete design, particularly in calculating the flexural strength of a concrete section with reinforcement. The figures provided alongside the mathematical approach help visualize and solve the problem effectively.
Transcribed Image Text:### Structural Engineering Problem: Calculating Flexural Design Strength #### Objective: For the section shown, use Whitney’s rectangular block to: - Calculate \( a \), \( \beta_1 \), and \( c \), - Determine the values of \( \epsilon_t \) and \( \phi \), - Calculate the flexural design strength \( \phi M_n \). #### Given Parameters: - Use normal weight concrete with \( f'_c = 4000 \text{ psi} \) and \( E_c = 3600 \text{ ksi} \), - Grade 60 steel (\( f_y = 60,000 \text{ psi} \), \( E_s = 29,000 \text{ ksi} \)). #### Diagram Description: A rectangular cross-section is illustrated as follows: - The width of the section is 16 inches. - The overall height of the section is 30 inches. - There are 6 reinforcement bars depicted as circles, each labeled as #9. - The depth of concrete cover from the top and the bottom of the section to the reinforcement is \( 2 \frac{1}{2} \) inches. - The depth to the centroid of the reinforcement steel bars is specified as 25 inches from the top. #### Detailed Steps for Calculation: 1. **Determine the depth parameters \( a \), \( \beta_1 \), and \( c \): - Use the given concrete and steel properties and refer to the respective codes or standards to determine these values. 2. **Calculate \( \epsilon_t \) and \( \phi \): - Utilize strain compatibility and force equilibrium methods to determine the tensile strain \( \epsilon_t \). - Use appropriate design codes to find the strength reduction factor \( \phi \). 3. **Compute the flexural design strength \( \phi M_n \): - Apply the calculated values into the design equations to find the nominal moment capacity and multiply by \( \phi \) to obtain the flexural design strength. #### References: - Structural engineering design codes (e.g., ACI 318). This problem helps in understanding how to apply fundamental principles of reinforced concrete design, particularly in calculating the flexural strength of a concrete section with reinforcement. The figures provided alongside the mathematical approach help visualize and solve the problem effectively.
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