Aprendizaje basado en casos de arquitectura 1. Principios generales del ABC-arq

Training Session

In this section you will create, analyze and design your first EngSolutions RCB building structure. You will be guided step by step through a simple example. The basic steps you take in processing the example building will show you principles that you will use with every other building that you design.

The Structure

The example structure is a 10-story building located in a high seismic risk zone. The structural system is a dual system, consisting of special reinforced concrete moment resisting frames and special reinforced concrete shear walls. The floor system is a two- way slab with beams. The columns and shear walls have constant cross-sections throughout the height of the building. The floor beams and slabs also have the same dimensions at all floor levels. Although the dimensions of the structural elements in this example are within practical range, the structure itself is hypothetical and has been chosen mainly for illustrative purposes.

Structural elements are designed according to ACI-318-05. Seismic forces, in this example, are defined according to ASCE 7-2005. However, the procedure for generating seismic forces according to other seismic codes such as UBC-97, NSR-98, RCDF-04, CFE-93, GUAD-97, REP-04, E030-03, and CEC-01, is similar. Story drift ratio amplified for the deflection amplification factor Cd, is limited to 0.02.

Other pertinent design data are as follows:

Load data:

Slab self-weight: 87.5 psf (7” two-way slab) Superimpossed DL*: 50 psf

Live load: 50 psf

Roof live load: 30 psf * Partitions, ceiling and mechanical

68 Elements: Interior columns: 20” x 20” Exterior columns: 16” x 28” Beams: 16” x 20” Walls: 12” Slab: 7” two-way Materials: Concrete: f’c = 4.0 ksi w = 150 pcf Reinforcement: fy = 60 ksi

Occupancy category: II (Importance factor. I =1)

Foundation soil:

Site class S = C (Very dense soil, ASCE 7, IBC)

Mapped Spectral Accelerations* Ss = 1.0, S1 = 0.4 (Equivalent to UBC-97 Z= 0.3)

* Maximum considered earthquake

Figure 5.1. Building considered in training example: Roof plan, typical floor framing plan (Floor levels 3-10), floor plan floor level 2 and a longitudinal elevation

Creating the Structure

• Run EngSolutions RCB and in the Starting window select the option 3D Frame/Wall in the group Create New Structure, to create a new three-dimensional model.

• In the story information window input 10 stories and press ENTER. • Input the first story height equal to 15 ft and press ENTER:

• In the second entry, type 10 and press ENTER.

• Press the ENTER key several times to repeat the previous value, until reaching the story height for the upper story.

The Building Wizard window should look as follows:

• Press ENTER or click the Next> button.

• Accept the proposed grid type (default), corresponding to an orthogonal system of architectural axes.

• Press ENTER or click the Next> button.

• For number of longitudinal axes type 4 and press ENTER.

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• Press ENTER twice to repeat the previous value. The Building Wizard window should look as follows:

• Press ENTER or click Next>.

• For Number of transversal frames type 7 and press ENTER.

• For spacing between transversal axes. Enter 25, 12.5, 12.5, 12.5, 12.5, and 25, pressing ENTER after each entry. The Building Wizard window should look as shown below:

• Press ENTER or click Next>.

• In the Reentrant corners window do not do any editing. In the case of buildings with re-entrant corners, such as buildings with floor plans shaped as “L”, “T”, “U”, etc., in this step of the creation process the engineer may permanently remove slab panels that do not exist. However, this can be done more conveniently later, after the 1st story has been created.

• Click the Next> button

• In the Local Axes Coordinates is possible to edit coordinates of axis intersections, in cases the architectural axes are not rectangular. The edition of axis intersections can also be done after the model has been created.

• Click the Create button to create the first floor plan of the model.

• A window is shown, asking for the type of floor system. Select 4, which correspond to a 2-way slab.

• Change the slab thickness to 7” and click OK

Based on the previous data, EngSolutions RCB creates a first story, which we can edit and use as basis for defining the rest of the model.

Change the current 3D view to a plan view by clicking the Plan View button (View

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button , to enlarge, reduce or move the floor plan to the center of your screen. The floor plan should look as shown in Figure 5.2.

Figure 5.2 Preliminary Floor Plan

In order to define the wall boundaries it is necessary to insert an axis between axes B and C, which for demonstration purposes we did not include when entering the axis information.

To insert an Axis

• Activate the Axes edition command , in the Elements toolbar

• In the Edit frames window (active command window) select the option Insert a

frame.

• Along transversal axis 7, click with the left mouse button a point, intermediate between axes B and C.

• A window is displayed asking for the relative distance, from B to the new Axis. • Type a relative distance equal to 0.5 to insert an axis in the middle of axes B and

• Click the OK button.

• The program creates a new axis B’.

The next step is to create the shear walls of the elevator core.

To add shear walls

• Activate the Wall edition command in the Elements toolbar

• In the Edit walls window (active command window) select option Add wall

• In the Wall property window enter a wall thickness equal to 12 in.

• Point the mouse cursor and click with the left mouse button to the intersection defining the first end of the shear wall (for instance C-2)

• Move the mouse cursor to the other end of the wall and click the left mouse button (for instance B-2). The program automatically connects the interior axis B’ creating two wall segments

• Using the same procedure add all shear walls of the elevators core. The configuration after adding the walls should look as shown in Figure 5.3.

To remove a wall segment activate the Wall edition command (if it is not active), select the wall segment and click the Remove button in the Property window.

In the next step, we will edit beams. We can remove the beams embedded within the walls and inexistent beams along transversal axes 3 and 5, add the longitudinal beam along axis B’, and assign beam properties.

To remove beams

Note:

• Activate the Beam edition command , in the Elements toolbar.

• In the Edit beams window (active command window) select option Existing

beams. This is the default option when the command is activated.

• Select a beam by pointing at it with the mouse cursor and clicking the left mouse button. For instance, mark the longitudinal beam C(2-3)

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• In the window properties click the Remove button.

• To remove various beams in a single step, press and maintain down the SHIFT key and select the following beams: 2(B-B’), 2(B’-C), A(2-3), A(5-6), C(5-6) • Click the Remove button.

• Use the same procedure to remove transversal beams 3(A-B), 3(C-D), 5(A-B) y 5(C-D)

Figure 5.3 Configuration after adding structural walls To add beams

• In the Edit beams window (active command window) select the option Add beams • Point and click the intersection that defines the first end of the beam (e.g. B’-3) • Move the mouse cursor to the other end of the beam and click the left mouse button

(e.g. B-5). The program automatically connects the intermediate axis 4 creating two beam segments.

Figure 5.4 Configuration after adding beams

To edit beam properties

• In the Edit beams window (active command window) select the option Existing

beams

• In the Edit beams window, in the selection options group, click the mini-button All

beams. With this button, all beams are selected in a single step. The property

window shows the properties that are common to all selected beams. All have section property: Beam1.

• Click in the Property window the name Beam1

• A table is displayed showing the properties of section Beam1. • Click the beam width (b), type 16 in and press ENTER. • Click the depth of the beam (h), type 20 in and press ENTER.

• The program automatically computes area and inertia properties of the section. • Click OK so that Beam1 become a rectangular beam section 16” x 20”. In this

example all beams will have this section. In a real project, we need to add various beam sections to this table.

• Click in the Property window the name of the material Rconcrete1 (reinforced concrete 1)

• Edit the compressive strength of concrete (f’c = 4 ksi) and enter modulus of elasticity E and shear modulus G (~0.4 E) corresponding to the specified concrete quality

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• Click OK

In the following step we will remove the slab panels in the elevator area.

To remove slab panels

• Activate the Slab edition command in the Elements toolbar.

• Point the mouse cursor to the center of the panel to be removed and click the left mouse button

• Click the Remove button in the property window

• To remove various panels in a single step, press and keep down the SHIFT key, mark all panels to be removed and click the Remove button. Use this procedure to remove all panels in the elevator area.

The configuration after removing slab panels should look as shown in Figure 5.5

Figure 5.5 Configuration after removing slab panels

To re –add slab panels previously removed, select option Add slab panel in the

Edit slabs Window. Then select the panels to be added and click the Add

button in the Property window. Note:

In the next step we will edit columns. We will remove the inexistent columns in axes 3 and 5. We will also remove columns at the ends of shear walls. If due to seismic

considerations boundary zones are required at the ends of shear walls, the program will automatically detect that condition and add them.

To remove columns

• Activate the Column edition command en the Elements toolbar

• In the Edit columns window (active command window) select the option Existing

columns

• Point at the column to be removed and select it by clicking the left mouse button. For instance select column A-3

• Click the Remove button in the Property window (or press the Del key)

• To remove various columns in a single step press and hold down the SHIFT key, mark the columns and click the Remove button. Use this procedure to remove columns from axes 3 and 5, and columns B-2, C-2, B-6, C-6

• Click the Refresh button in the View toolbar to redraw the floor plan.

To edit column properties

• In the Edit column window, in the Selection options group, click the mini-button All

columns to select all columns

• In the Column properties window click property Column1

• In the Table of sections, change the section dimensions to b=20 in, h = 20 in. • In the property Name, in the Table of sections, click at Column1 and change this

name to 20x20 • Click OK

• Click the Assign button to assign these changes

• Click at any point in the screen without pointing at any column

To change properties of exterior columns

• In the selection options of the Edit columns window, select the option Story L-Frame

cols.

• Select column D-1. All columns along axis D are selected • Press and hold down the SHIFT key

• Select column A-1. All columns along axis A are selected

• Change the selection option to Single column and release the SHIFT key To add a new section

• In the Column properties window click at the name of the section C20x20 • In the table of sections, click the Add button to add a new section. • Select a rectangular section and click the Next> button.

• Edit the size of the new section to b = 16 in, h = 28 in • Click OK.

• In the table of sections, change the name of the new section to C16x28. • Click OK.

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Figure 5.6 Column sections

To modify column properties • Select column B-1.

• Pressing and holding down the SHIFT key, select also columns C-1, B-7 y C-7. • In the Column property window click the name of the section C20x20.

• In the sections list (left side of the table of sections) select section C16x28 and click OK.

• In the Column properties window, in the property corresponding to orientation edit the property value entering 90 degrees (to rotate the selected columns) and press ENTER.

• Click the Assign to apply these changes.

The configuration to edit columns should look as shown in Figure 5.7. As an additional exercise, it is suggested to change the section of column A-4, for a new circular section 24 in diameter (Oval: 24 in x 24 in)

When the intermediate Axis B’ was inserted new nodes were created in axes 1 and 7. Node B’-1 segments beam 1(B-C) into segments 1(B-B’) and 1(B’-C). These fictitious nodes have no effect on the final analysis and design results. In designing beams, the

program recognizes that the above two segments correspond to beam 1(B-C) and designs it as a single element. However, these fictitious nodes increase unnecessarily the size of the model, increasing the number of degrees of freedom and the solution time. For this reason and other reasons, it is convenient to remove any fictitious nodes so that beams and walls are not segmented unnecessarily.

Figure 5.7 Final configuration of first aerial slab.

To remove fictitious nodes

• Activate the Nodes edition command in the Elements toolbar.

• In the Edit nodes window (active command window) select the option Existing nodes • Pressing and holding down the SHIFT key, mark nodes B’-1, B’7, A-3, A-5, D-3 y D-5 • Click the Remove button.

To add previously removed nodes, select the option Add node in the Edit node window. Then select the nodes to be added and click the Add button in the Node properties window.

Note:

The final configuration of the first floor plan should look as shown in Figure 5.7. It is recommended to save periodically the model to avoid loosing information.

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To Save the model

• In the File menu or in the Standard toolbar activate the command Save and save the model assigning a file name.

We will use the first story created as basis to created the additional floor levels.

To create next level

• Change the current plan view to a 3D View clicking the 3D View button in the

View toolbar.

• Click the Next Floors button in the main 2 12500iwhA

• In the displayed 00iwhA, indicate that you just want to create up to floor level 3 (the default is 11, which is the upper level)

• Click OK

The program creates a n125story. If there are plan changes we can edit the n125floor plan, preferably in a plan view

To edit the typical floor plan

• Change again to a plan view clicking the Plan 2 125button . The program shows the current Floor level in the selection box n1ar the V 12 5buttons5(in this5case5floor level 3)

• Activate the Slab edition command.

• Select the lower left panel pointing at its center and clicking the left mouse5button. • Remove the slab panel clicking the Remove5button in the Slab properties window. • Activate the Column edition command.

• Select column A-7 and remove it by clicking the Remove button. • Activate the Beam edition command

• Select an remove beams A(6-7) y 7(A-B)

The final configuration of the typical floor plan should look as shown in Figure 5.8

To create the additional floors

• Click the Next Floors5button.

• In the Create additional stories windows accept the defaults by clicking OK • Change the current view for a 3D view to see the complete model

• If necessary, enlarge, reduce or move the model to see the whole model in the main view window, using the commands Zoom(+), Zoom(-) and Move .

Figure 5.8 Typical floor framing plan

To edit the roof (roof of elevators and machine room)

• Change the current 3D View for a plan view (Floor level 11) • Activate the Slab edition command

• In the Selection options group of the Edit slabs window (active command window) select the option Floor panels

• Select any slab panel. All slab panels in the active floor are selected. • Click the Remove button to remove all slab panels of the upper floor level • In the Edit slabs window select the option Add slab panel

• In the Slab properties window click at the slab name: Slab type 1.

• In the Table of slab sections click at the Add button to add a new slab type. • Select a two-way slab and click OK.

• Enter a slab thickness of 6 in and live load 30 psf. Then click OK.

• Press and hold down the SHIFT key and mark the slab panels corresponding to the elevators and the central machine room

• Click the Add button to add these panels

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The beams and columns of the exterior axes could be removed individually. However, it is much easier to remove the nodes, which will automatically remove the framing elements.

Figure 5.9 Roof plan after re-addition of slabs

• Activate the Node edition command in the Elements toolbar. Note that the Node edition command should not be confused with the Axis Intersection edition

command .

• In the Edit nodes window (active command window) select the option Floor L-Frame. • Mark any on axis D. All nodes along D are selected.

• Click the Remove button. Nodes, beams and columns along D axis are removed. • Select any node on axis A.

• Click the Remove button. All nodes and elements along Axis A are removed. • In the Edit nodes window select the Single node selection option.

• Press and hold down the SHIFT key and mark the exterior nodes B-1, C1, B-7, C-7. • Click the Remove button.

• Close the Edit nodes window to deactivate the command. The final roof configuration should look as shown in Figure 5.10.

• Change the actual view for a 3D view using the 3D View button in the View toolbar. • Save the model.

The final configuration of the 3D model should look as shown in Figure 5.11.

Figure 5.10 Roof floor framing plan

Making visible selected parts of the structure

To make visible a particular floor framing plan

• Click the Plan View button in the View toolbar

• In the selection box located near the View buttons, select the desired floor level. For instance select floor level 10.

To make visible a particular frame of the model

• Click the Elevation view button in the View toolbar.

• In the selection box located near the View buttons, select the desired frame. For instance select frame B.

To make visible part of a model in 3D

• Change the current view to a 3D view clicking the 3D View button in the View toolbar. • In the View menu, select the command: View > Visible > Floor.

• The Visible window is displayed. To make visible floors 1 to 3, floor 3, and floor 9, select the option Floors and input the following text: 1-3, 7, 9

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• Click OK. After examining the result, make visible the complete structure, activating the command: View > Visible > All.

Figure 5.11 3D configuration

Interactive commands, such as printing command and design commands, operate only on the elements that are visible. Therefore, when a certain region of the structure, such

as a particular frame, and a design command is activated, the program only designs the elements of that frame.

In this example the geometry is perfectly regular. If in the real structure, the axes do not conform an orthogonal grid, we can edit the individual axes intersections to model the actual geometry.

To Edit Axis intersections

• Activate the Axis intersection edition command in the Elements toolbar.

• Change the current view to a plan view corresponding to floor level 10. Edition of axis

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