Lecture 17 – Page 1 of 17

Lecture 17 – Concrete Analysis/Design using “RAM” Software RAM is a commercially available software package used for analysis and design of structures. It is very powerful and accurate. We will be using it to analyze and design the flexural reinforcing for a simply-supported reinforced concrete beam. EXAMPLE 1 GIVEN: A simply-supported 12” x 20” concrete beam uses f’c = 4000 psi and Grade 60 bars. All loads shown are factored, and includes beam weight. REQUIRED:

1) Draw and label the complete shear + moment diagrams. 2) Determine the minimum required area of tensile steel, assuming “d” = 18”. 3) Using RAM software, determine the support reactions and maximum moment. 4) Using RAM software, determine the minimum required area of tensile steel.

Step 1 - Draw and label the complete shear + moment diagrams.

1’-0”

R2= 14.0 Kips R1 = 22.0 Kips

22 kips 17 kips

1 kips

5’-0” 15’-0”

wu = 1000 PLF (incl. beam wt.)

16 Kips

0

-14 kips

0

98.0 Kip-ft 97.5 Kip-ft

Mmax = 98.0 Kip-ft

0 0

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Step 2 – Determine the minimum required area of tensile steel, assuming “d” = 18”.

Using Mmax = Mu, use 2bdM u

φ from Lecture 4:

where: Mu = 98 Kip-ft = 1,176,000 lb-in φ = 0.9 b = 12” d = 18”

2bdM u

φ = 2)"18)("12)(9.0(

1176000 inlb −

= 336.1 psi

Use ρ = 0.0059

12”

18” 20”

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Recalling bdAs=ρ

Solve for As = ρbd = (0.0059)(12”)(18”) Required As = 1.27 in2

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RAM Software

Step 1 – Create a model of the beam as shown below:

“Y” a

xis

“X” axis

16 Kips

5’-0” 20’-0”

Node 2 – Coordinates = 20’,0’ Roller end support

Node 1 – Coordinates = 0’,0’ Pinned end support

wu = 1000 PLF

Member 1

Nodes Tab

Members Tab

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Step 2 – Input coordinates for “Nodes” 1 and 2:

Step 3 – Define member 1 between Nodes 1 and 2:

“Nodal coordinates”

Type in coordinates here

Nodes Tab

Members Tab

“Connectivity and description”

Type in node numbers here

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Step 4 – Define support types at Nodes 1 and 2:

Nodes Tab

“Restraints”

Click on Node 1

Click on “Pinned, no translation”

Node 1

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Nodes Tab

“Restraints”

Click on Node 2

Click on “Pinned, translate in X”

Node 1

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Step 5 – Define member 1 “Section”:

Members Tab

“Sections”

Member 1

RcBeam

Double-click 12x20in

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Step 6 – Define member 1 “Materials”:

Members Tab

“Materials”

Member 1

Click “RC” (Reinf. Conc.)

Double-click C4-60.Mat (f’c = 4 ksi, grade 60 bars)

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Step 7 – Define member 1 “Loads on members”:

Members Tab

“Loads on members”

Member 1

Click “Distributed force (downward –y direction)”

Distributed forces

See “Distributed load” dialog box, next page

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Enter 1.0 here – notice that the units are [Kip/ft]

Click OK

See next page for input of point load on member

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Input concentrated load here:

Members Tab

Member 1

Concentrated forces

Click “Concentrated forces on members”

See “Concentrated loads” dialog box, next page

Additional concentrated loads may be added (or edited) here

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16 Kips point load

(see loading diagram)

Load is located 5’-0” from left end of member (see loading diagram)

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Step 8 – Save file, then “Analyze structure…”:

Click “Process”

Click “Analyze structure…”

Click “Analyze”

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Step 9 – View and print “Force Diagrams”:

NOTE: Shear diagram is shown upside-down relative to the convention we are used to.

Use slider bar to scroll along length of member dynamically see numeric results

Verify Mmax = 98 Kip-ft = same as hand analysis!!

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Step 10 – View and print “Reinforced concrete design…”:

See reinforced concrete analysis results, next page

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Flexure As = 1.32 in2 → compare with hand-

calculations As = 1.27 in2 → VERY CLOSE!!!