Draft

12.1Introduction 201

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h

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f

y

fc

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2f =2f 0

t c

c

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2fc

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f

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0

Midspan

Ends

Midspan

Q

Ends

f

Figure12.4:Alternative SchemesforPrestressinga RectangularConcreteBeam,(Nilson1978)

P sinq P sinq

P cosq P cosq

P

P cosq

P cosq

P sinq P sinq

P cosq

P sinq

P

2

P sinq P sinq

P cosq

M

P cosq

P sinq P sinq

P cosq

P sinq

P q

q

P

P e

P

P P

P e P e

e

P

qM

P P

None

P

P

P

2

None

P P

(a)

(b)

(d)

(f)

(g)

(e)

P

(c)

Member Equivalent load on concrete from tendonMoment from prestressing

Figure12.5:Determinationof Equivalent Loads