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Ultimate forces on columns are calculated according to based on tributary analysis. Load take down is the transferring process of the loads cumulatively to the vertical members below.
Load Take Down
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based on Tributary Analysis
Area Loads
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on Slabs
Load take down of area loads which are in the same load class is calculated as follows;
→ The loading area within the boundaries of the tributary area of column is determined at each floor ( if exists )
→ This intersection areas are area is multiplied by the loading value at each floor (in psf)
→ The lumped forces calculated loads on each floor(in kips) are reported cumulatively at each floor depending on their load class in Tributary Forces spreadsheet
Line Loads
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on Slabs
Load take down of line loads which are in the same load class is calculated as follows;
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→ This length is multiplied by the loading value at each floor (in k/ft)
→ The lumped forces calculated loads on each floor(in kips) are reported cumulatively at each floor depending on their load class in Tributary Forces spreadsheet
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Live loads which are classified as “L,L_Heavy or L_Passenger” are permitted to be reduced in the alternative method.
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Figure 4
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Live loads not exceeding 100 psf and are other than public assembly or parking vehicle garages are classified as “L” live load.
The design live load of any structural member supporting 150 square feet or more is permitted to be reduced.
Live load reduction along column design line Reducible live load area is calculated as followsdescribed below;
→ The tributary area of each column at column design line is determined.
→ The live load area/ tributary area ratio of each live load class (if any) at each column is determined.→ Each tributary area is multiplied by the live load area ratio of each live load class (if any) to determine the intersection area of the column tributary and the reducible load area is calculated at each floor.
→ Cumulative reducible area is calculated at each floor.
→ Reducible area of the transfer column ( if exists ) is multiplied by the distribution factor and added to cumulative reducible live load area at each floor along the the transfer floor.
Live load reduction along column design line .is calculated as follows;
→ Cumulative Total reducible area of live load classesclass L (if any) at each column is determined along the column design line as described before.
→ Reduction in percent is a function of cumulative tributary area wherecalculated based on the following equation;
R= 0.08*(At -150)
→ For one way slabs, tributary area, At, shall not exceed the product of slab span and a width normal to slab span of 0.5 times slab span.
→ Maximum reduction in percent for columns can not be more than %60 or %23.1*(1+D/L) where D is dead load per square foot of area supported and L is unreduced live load per square foot of area supported.
L Load Reduction
Live loads not exceeding 100 psf and are other than public assembly or parking vehicle garages are classified as “L” live load.
→ Maximum reduction in percent for columns can not be more than %60.
→ Live load reduction factor is equal to (100maximum of (0.6, 1- Rmax)/100).
L_Heavy Load Reduction
Live loads exceeding 100 psf are considered to be heavy live loads. Live load reduction for L_Heavy is calculated as follows;
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→ If column supports two or more floors, live load reduction factor is the maximum of ( 0.8, 1-Rmax/100 )
L_AssemblyGroupA Load Reduction
Live Loads which are classified as “L_AssemblyGroupA “ are not permitted to be reduced in alternative method. Thus live load reduction factor for L_AssemblyGroupA is always 1.0.
L_ParkingVehicleGarages Load Reduction
Live loads which are classified as “L_ParkingVehicleGarages” are permitted to be reduced as following;
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→ If column supports 2 or more floors, live load reduction factor is the maximum of live load reduction factor explained in “L” class live loads and (0.8, 1-Rmax/100).
Lr Load Reduction
Roof live loads which are classified as ”Lr” is considered to be unreducible live loads.
Column Schedule
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Figure 4
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Figure 4’de görülen “Run Tributary Analysis” butonuna tıklanarak tributary analizi gerçekleştirilir. |
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If there is discontinuity in colum design lines, a red point is created on the cell in spreadsheet. Move cursor over the red point to see load distribution factors fractions of load bearing vertical members near neighboring to discontinuous the discontinous column as illustrated demonstrated in Figure 6.The distribution factors are calculated by assuming the total force supported by the column as point load.
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Düşey yönlü bir süreksizlik olması durumunda spreadsheet’deki tabloda süreksizliğin olduğu kolona ait hücrede kırmızı bir nokta belirir. Bu nokta üzerine imleç götürüldüğünde kolonun yükünün hangi kolonlara veya perde duvara ne oranda dağıtıldığı bilgisi şekil-3’deki gibi görünür. |