HW #$8$ Concrete Slab Formwork

Module $20$

Due Date: $11$:$59$ PM EST on the date given in on Canvas Schedule

Refer to the course schedule to find the exact date.

Point Value: Max. $50$ points

This assignment counts towards your homework grade.

Purpose

You will

T$\mathrm{.}3$ Design and economize the components of concrete forming systems.

a$.$ Understand the components of concrete and concrete formwork.

b$.$ Calculate the concrete rate of pour based on varied placement methods and equipment.

c$.$ Calculate liquid concrete lateral pressures on vertical formwork.

e$.$ Design and economize the components of concrete slab formwork.

Task & Criteria for Assessment

Use the Chapter $13$ reference I provided in the Module $17$ folder; the resources and

information on Canvas; my lectures $($videos have now been made available to all sections$)$ and

the spreadsheets that accompany this homework assignment.

The available points for each part are given in $($yellow highlighting$).$

Design the wall form work using the Concrete Slab Form Design spreadsheet provided. Only change

cells on the spreadsheet that are shaded grey or have red text. You should be locked out of all

other changes. All your input text should be in red and should be entered as a number without

units except where noted otherwise. The green shaded cells are the intermediate results, and the

blue shaded cells are the final conclusions at the end of each design step.

$1.$ In Step $1$ enter all the following starting criteria:

$1)$ Concrete unit weight $=150$ pcf$.$

$2)$ Slab thickness, t $=8\mathrm{.}0$ in$.$

$3)$ Assume a formwork dead load of $6$ psf for now. You will need to come back and

verify this assumption against the calculated valued that will later be added up in

cell N$8.$

$4)$ Live load required $=50$ psf

$5)$ Wood unit weight $($density$)=40$ pcf $($we are using Southern Pine$).$

$6)$ Top of concrete elevation above the shoring support elevation $=10\mathrm{.}00$ ft$.$

$7)$ Slab pour area is $80$ ft x $40$ ft$.$ Enter the longer dimension above the shorter one.

$8)$ in cell E$23$ we need to enter the elevation of the top of the brace, h$=7\mathrm{.}5$ ft$.$ This is

the height of the top of our brace. We will come back to this in Step $7.$

$1\mathrm{.}1.$ Confirm that you got a total design load $=156$ psf and the space below the stringers

should initially say $9\mathrm{.}26$ ft in cell E$21.$ These will change. Also, do not worry that the

actual dead load of the design starts out saying $$#DIV$/0!.$ You do not have any decking,

joist, or stringer sizes in yet so the spreadsheet can$$t estimate the actual weight of

your design. This step is just to confirm you got the basic input in correctly.

Indiana State University

CNST $418$ Design of Temporary Structures

Course CRNs: All

$2.$ In Step $2$ you will be optimizing the design of the sheathing which sets the spacing of the

joists. In this step Plyform or flat lumber can be used as sheathing. $(8$ points total$)$

We must first decide which system to use. If lumber is used, then design lines $32$ to $55$

will be used in the spreadsheet. If Plyform is used, then design lines $56$ to $70$ will be

used in the spreadsheet.

You will need to enter the following additional criteria:

$9)$ Allowable deflection, allowable $=$ span$/360.$ To the right of the cell, you will notice I have given

a little arrow for a short menu of options. Choose the $360$ option in H$28.$

$10)$ You will be using $$Plyform$$ so enter $$P$$ in cell G$30.$ There is a menu option here

too. $($Skip lines $32$ to $55$ in the spreadsheet since we do not need to design lumber

sheathing now.$)$

$11)$ Use $7/8$ thick Plyform decking. There is a menu option here too. Choose $7/8$ from

among the thickness options. Enter this in cell H$56.$

$2\mathrm{.}1.$ Choose the exact description of the nominal plywood thickness and grain direction

into the space provided for it$.$ To facilitate this there are pull down menus in cells J$56$ and

K$56$ to help you choose the proper descriptions for the class and orientation. Choose

the Plyform from Table $13-6$ that is the least expensive that allows for a joist

spacing of $16$ to $24$ inches on center. Remember in order of lowest to highest cost

the options are Plyform Class II$,$ then Class I, then Structural I. $(2$ points total, $1$ point for

the correct class and $1$ point for correct reference to the direction of the grain$)$

$2\mathrm{.}2.$ To reflect the properties of your decision, enter the three section and material

properties given in Table $13-6$ in the spreadsheet $($EI$,$ F b KS$,$ and F s Ib$/$Q$).$ The three

properties are required for deflection, bending and shear calculations respectively.

There is a calculation for the allowable plywood span as governed by the Plyform$$s

capacity for resisting deflection, bending, and shear respectively. The minimum

allowable Plyform span is the governing dimension in cell H$69.$ That dimension

should not be less than $16$ in or greater than $24$ inches. Acceptable spacings are

$16,19\mathrm{.}2$ and $24$ on center because all of these are even spacings for a $4$ x $8$ sheet of

Plyform. $(3$ points, $1$ each$)$

$2\mathrm{.}3.$ Verify that the joist spacing