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What is the effective moment of inertia denoted as in the ACI 318 code?
Ie
In ACI 318, what does the effective moment of inertia account for?
Observations on Ie computation
According to ACI 318, which factors are independent of the loading on the beam?
Icr, Ig, and Mcr
How does the effective moment of inertia change with an increase in load on the beam?
Ie will decrease
What is the relationship between load increase and the development of cracks in the beam according to ACI 318?
As load increases, more cracks will develop leading to reduced Ie
What is staged loading in structures?
Staged loading is the application of Dead load D and live load L in stages on a structure.
How is a concrete beam subjected to staged loading?
A concrete beam is first subjected to dead load and then further loaded by dead load plus live load in stages.
What is the purpose of applying live load in staged loading?
The live load is applied to compute the deflection due to live load only, as some portion of the live load can be sustained for a period of time.
What is the concept of staged loading in structures?
Staged loading is the application of Dead load (D) and live load (L) in stages, where the structure is first subjected to dead load and then further loaded by dead load plus live load.
How can we determine the deflection caused by only load 3 in staged loading?
To determine the deflection caused by only load 3 in staged loading, we need to consider the loading history and the sequence of loading stages, such as 3-123-12-3, and analyze the deflection due to each stage of loading.
Why is it challenging to compute the deflection caused by load 3 directly in staged loading?
It is challenging to compute the deflection caused by load 3 directly in staged loading because the beam never sees load 3 by itself, as it is subjected to a sequence of loading stages.
What is the solution to computing the deflection due to live load only in staged loading?
To compute the deflection due to live load only in staged loading, the loading history and the sustained portion of the live load for a period of time need to be taken into account during the analysis of the beam's behavior under different loading stages.
What are deflection limits in the ACI 318 code often based on?
Live load
When is live load typically applied in relation to dead load in structural analysis?
After dead load is applied
How can live load deflection be computed according to the text?
By using load factors (LL, DL, LL)
Untitled Flashcards
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What is the Service Limit State Check for Deflection in a beam?
It involves determining the deflection under different loading conditions including immediate deflection due to live load, long-term time-dependent deflection due to creep and shrinkage of concrete, and total deflection.
How is immediate/instantaneous deflection due to live load denoted in the expression for service limit state check for deflection?
It is denoted as L_DL_D in the expression.
What additional deflection develops under sustained load in the service limit state check for deflection?
Under sustained load, the dead load portion of the live load contributes to additional deflection due to creep.
What is the design load for a storage warehouse?
100% of its design load over its design life
How is the total long term deflection computed?
Total long term deflection = Immediate deflection due to live load + Immediate deflection due to dead load + Immediate deflection due to sustained live load
What does SL represent in the computation of long term deflections?
Sustained live load multiplier for infinite duration
What is the time dependent factor used in the computation of long term deflections?
Duration multiplier for the duration of sustained live load
What is the sustained load (w) on the beam?
40 kipft
What is the duration of the sustained load on the beam?
12 months
What is the distributed load (w_L) on the beam?
25 kipft
What is the span length (L) of the beam?
24 ft
What is the moment of inertia (I_g) of the beam?
18000 in^4
What is the cracked moment of inertia (I_cr) of the beam?
9600 in^4
What is the critical moment (M_cr) on the beam?
50 ft-kips
What is the modulus of elasticity (E_c) of the beam material?
4030 ksi
What is the total long term deflection of the beam shown below?
To be determined.
What is the value of Ig for the beam?
18000 in^4
What is the value of Icr for the beam?
9600 in^4
What is the value of Mcr for the beam?
50 ft-kips
What is the value of Ec for the beam?
4030 ksi
Are ACI service limit state requirements met for the beam?
To be determined.
What is the value of wd for the beam?
10 kip/ft
What is the value of wl for the beam?
25 kip/ft
What is the length of the beam (L)?
24 ft
