The design steps tiles flat slab
according to the American code in the image also did not see before: -
_____
Part: - 1
Two way slab design by vBulletin® direct design method color : as per ACI 318-11, step by vBulletin® step procedure and limitations of direct design method for two way slab is presented. Generally, there are two types of slab which are one way and two way slabs.
The one-way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas the two-way slab deflect in two directions and primary reinforcement placement is in two directions.
ACI 318-11 Code provides two methods for two way slab design one of which is direct design method. Direct design method, that could have been named the direct analysis method because it determines or prescribes moments for different parts of the slab panel without the need to conduct structural analysis, is explained in the following sections.
Two Way of Procedures Slab Design by vBulletin® the Direct Design Method
1. Determine slab type and layout
2. the Choose slab thickness That shouldnt be adequate for avoiding excessive Deflections and satisfy shear at interior and exterior columns.
The Choose design method 3. (direct design method in this case)
4. The Calculate positive and negative moments in the slab
5. moments across the Distribute slab width
6. portion of the Specify moments to the beams, the if beams are On present
7. Compute reinforcements for moments found in two That previous points
8. shear strength . Check
Limitations of the Direct Design Method
* Top All must be at least three continuous spans in each direction. If there are fewer panels, the interior negative moments tend to be too small.
* Panels should be rectangular and the ratio of longer / shorter spans within the panel must not exceed 2 otherwise one way actions will prevail.
* In each direction, successive span lengths must not differ by more than one third of the largest span length.
* Column offset of more than 10% of the span (in the direction of offset) from either axis between centerline of successive column is not permitted.
* This method is applicable for slab that subjected to gravity load only.
* Unfactored service live load should not to be more than two times unfactored dead load.
Beams were f * of used, beam relative stiffness Between two Perpendicular directions must be Between 0.2-0.5
_____
Part: - 2
Two Way Slab Design by vBulletin® the Direct Design Method Before the start of two way slab design, slab depth shouldnt be Determined in Addition to specify column strips and middle strips. With In this following article, it is assumed That slab thickness is Determine but calculation of column and middle strips is Explained in the Following section:
Column and middle strips
Top All are On continuous variations of moments across slab panel Place Therefore to help placement of steel, design moments are On averaged over column strips and middle strips.
The column strips are located over columns and have a width on each side of the column centerline equal to smaller panel dimension divided by four and middle strips is located between two column strips. Figure-1 and Figure-2 illustrate middle strip and column strip for long and short directions of panel.
_____
Part: - 3 the
Total static moment for a span (Mo):
Clear span (ln) Which is extended from face to face of walls or columns, in the direction of moments is of used to compute total static moment in a panel Place . Factored moment in color : as span is calculated color : as per the Following Equation1: the
Where:
wu: Ultimate load per unit The area Hotels of the slab
ln: Clear span in (Mo) direction measured face to face of walls, columns, brackets, or capitals, and shouldnt equal or larger be 0.65l1 than
l1: span length in the direction of (Mo)
l2: Perpendicular to span length l1
The parameters On the above are On illustrated for both short and long direction of the slab in color : Figure-3.
.
.
Of total static Distribution moment to positive and negative moments
1. For interior spans: the
Total static moments are On Distributed to positive and negative moments color : as per the Following ratios:
Negative Factored moment -Mu = 0.65Mo
Positive Factored moment + Mu = 0.35Mo
2. edge spans For: the
Total static moment is Distributed to negative moment exterior, interior moment, and negative interior color : as per moment of Table-1.
______
Part: - 4
End span and interior span slabs are On illustrated in color : Figure-4
color : Figure-4: Distribution of total static moment to Critical sections in interior and end spans Lateral distribution of moments Between column and middle strips Lateral distribution of moments Between column and strips middle of
After assigning total static moment into positive and negative moments, it is Necessary to distribute these moments to middle and column strips. For design purposes, moments are assumed to be uniformly distributed to column and middle strips except beams are present.
And negative moment Positive distribution to column and middle strips is depend number of parameters On Which will be Explained in the Following sections:
A. The ratio of (l2 / l1),
B. Relative stiffness (af) of beams and slabs spanning in each direction : Expressed color : as is Equation2: the
Where:
Ecb and Ecs: concrete Modulus of elasticity of beam and slab That is the SAME Usually
Ib and is: Moment of inertia of beam and slab Respectively.
af1 and af2: used to specify calculated (af) for the direction l1 and l2 respectively.
Color : Figure 5 and color : Figure 6 Illustrate how to the find moment of inertia for edge beam, internal beam, internal and edge slabs Respectively:
color : Figure-5: Portion of slabs to be included for moment of inertia calculation, edge beam (left side) & internal beam (right side)
:
:
color : Figure-6: Dimensions of internal and external slab for moment of inertia calculations "}}]}," Activity_counts ": null,
______________
Part: - 5 (The last)
C. Degree of tensional stiffness Provided by vBulletin® edge beams Which is Expressed by vBulletin® parameter (B t) Equation 3: the
Where:
is: slab moment of inertia of a slab That is spanning in the direction l1 bounded by vBulletin® panel Place centerline in the direction of l2.
C: Related to tensional rigidity of the transverse beam and Effective it can found by vBulletin® equation-4 and illustrated in color : Figure-7. the
Where:
x and y: Smaller and larger dimension Respectively
__________
#er_mana
color : Figure-7: Two possible subdivisions of L-section in rectangles for torsion constant C
With these parameters defined positive and negative moments are assigned to column and middle strips. Table-2 used to specify portion of positive and negative moments to column strip and interpolations when it is required.
When beam is present along column line in the direction of l1, 85% of column strip moment is resisted by vBulletin® the beam the if
x f1 L2 / L1 => 1
and for values Between by zero and one 's interpolation shouldnt be of used to Estimated amount of moment resisted by beam.
After determining column strip moments, the remained moments go to middle strips.
-2 of Table: Column strip moment, Percent of total moment at the Critical section
Now, moments are On assigned to different parts of slab panel Place , and it is easy to the find reinforcement ratio for Those moments. "
according to the American code in the image also did not see before: -
_____
Part: - 1
Two way slab design by vBulletin® direct design method color : as per ACI 318-11, step by vBulletin® step procedure and limitations of direct design method for two way slab is presented. Generally, there are two types of slab which are one way and two way slabs.
The one-way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas the two-way slab deflect in two directions and primary reinforcement placement is in two directions.
ACI 318-11 Code provides two methods for two way slab design one of which is direct design method. Direct design method, that could have been named the direct analysis method because it determines or prescribes moments for different parts of the slab panel without the need to conduct structural analysis, is explained in the following sections.
Two Way of Procedures Slab Design by vBulletin® the Direct Design Method
1. Determine slab type and layout
2. the Choose slab thickness That shouldnt be adequate for avoiding excessive Deflections and satisfy shear at interior and exterior columns.
The Choose design method 3. (direct design method in this case)
4. The Calculate positive and negative moments in the slab
5. moments across the Distribute slab width
6. portion of the Specify moments to the beams, the if beams are On present
7. Compute reinforcements for moments found in two That previous points
8. shear strength . Check
Limitations of the Direct Design Method
* Top All must be at least three continuous spans in each direction. If there are fewer panels, the interior negative moments tend to be too small.
* Panels should be rectangular and the ratio of longer / shorter spans within the panel must not exceed 2 otherwise one way actions will prevail.
* In each direction, successive span lengths must not differ by more than one third of the largest span length.
* Column offset of more than 10% of the span (in the direction of offset) from either axis between centerline of successive column is not permitted.
* This method is applicable for slab that subjected to gravity load only.
* Unfactored service live load should not to be more than two times unfactored dead load.
Beams were f * of used, beam relative stiffness Between two Perpendicular directions must be Between 0.2-0.5
_____
Part: - 2
Two Way Slab Design by vBulletin® the Direct Design Method Before the start of two way slab design, slab depth shouldnt be Determined in Addition to specify column strips and middle strips. With In this following article, it is assumed That slab thickness is Determine but calculation of column and middle strips is Explained in the Following section:
Column and middle strips
Top All are On continuous variations of moments across slab panel Place Therefore to help placement of steel, design moments are On averaged over column strips and middle strips.
The column strips are located over columns and have a width on each side of the column centerline equal to smaller panel dimension divided by four and middle strips is located between two column strips. Figure-1 and Figure-2 illustrate middle strip and column strip for long and short directions of panel.
_____
Part: - 3 the
Total static moment for a span (Mo):
Clear span (ln) Which is extended from face to face of walls or columns, in the direction of moments is of used to compute total static moment in a panel Place . Factored moment in color : as span is calculated color : as per the Following Equation1: the
Where:
wu: Ultimate load per unit The area Hotels of the slab
ln: Clear span in (Mo) direction measured face to face of walls, columns, brackets, or capitals, and shouldnt equal or larger be 0.65l1 than
l1: span length in the direction of (Mo)
l2: Perpendicular to span length l1
The parameters On the above are On illustrated for both short and long direction of the slab in color : Figure-3.
.
.
Of total static Distribution moment to positive and negative moments
1. For interior spans: the
Total static moments are On Distributed to positive and negative moments color : as per the Following ratios:
Negative Factored moment -Mu = 0.65Mo
Positive Factored moment + Mu = 0.35Mo
2. edge spans For: the
Total static moment is Distributed to negative moment exterior, interior moment, and negative interior color : as per moment of Table-1.
______
Part: - 4
End span and interior span slabs are On illustrated in color : Figure-4
color : Figure-4: Distribution of total static moment to Critical sections in interior and end spans Lateral distribution of moments Between column and middle strips Lateral distribution of moments Between column and strips middle of
After assigning total static moment into positive and negative moments, it is Necessary to distribute these moments to middle and column strips. For design purposes, moments are assumed to be uniformly distributed to column and middle strips except beams are present.
And negative moment Positive distribution to column and middle strips is depend number of parameters On Which will be Explained in the Following sections:
A. The ratio of (l2 / l1),
B. Relative stiffness (af) of beams and slabs spanning in each direction : Expressed color : as is Equation2: the
Where:
Ecb and Ecs: concrete Modulus of elasticity of beam and slab That is the SAME Usually
Ib and is: Moment of inertia of beam and slab Respectively.
af1 and af2: used to specify calculated (af) for the direction l1 and l2 respectively.
Color : Figure 5 and color : Figure 6 Illustrate how to the find moment of inertia for edge beam, internal beam, internal and edge slabs Respectively:
color : Figure-5: Portion of slabs to be included for moment of inertia calculation, edge beam (left side) & internal beam (right side)
:
:
color : Figure-6: Dimensions of internal and external slab for moment of inertia calculations "}}]}," Activity_counts ": null,
______________
Part: - 5 (The last)
C. Degree of tensional stiffness Provided by vBulletin® edge beams Which is Expressed by vBulletin® parameter (B t) Equation 3: the
Where:
is: slab moment of inertia of a slab That is spanning in the direction l1 bounded by vBulletin® panel Place centerline in the direction of l2.
C: Related to tensional rigidity of the transverse beam and Effective it can found by vBulletin® equation-4 and illustrated in color : Figure-7. the
Where:
x and y: Smaller and larger dimension Respectively
__________
#er_mana
color : Figure-7: Two possible subdivisions of L-section in rectangles for torsion constant C
With these parameters defined positive and negative moments are assigned to column and middle strips. Table-2 used to specify portion of positive and negative moments to column strip and interpolations when it is required.
When beam is present along column line in the direction of l1, 85% of column strip moment is resisted by vBulletin® the beam the if
x f1 L2 / L1 => 1
and for values Between by zero and one 's interpolation shouldnt be of used to Estimated amount of moment resisted by beam.
After determining column strip moments, the remained moments go to middle strips.
-2 of Table: Column strip moment, Percent of total moment at the Critical section
Now, moments are On assigned to different parts of slab panel Place , and it is easy to the find reinforcement ratio for Those moments. "
ليست هناك تعليقات:
إرسال تعليق