1350

0.5 in. rebar

1300

Rod 6

1250

Rod 5

1200

1150

23 Sep

3 Sep

14 Aug

25 Jul

5 Jul

15 Jun

26 May

6 May

16 Apr

Period of Test

Table 16, in which a very small trend of increas-

Findley's general theory of creep behavior of

ing strain could be observed, the values of *m *and

viscoelastic polymer (1960) is represented by

ε *= *ε0 + p (t/t0)q

(12)

values closely match Mosallam and Chamber's

(1995) published values for commercially avail-

where ε = the total strain

able pultruded FRP WF beams: *p *= 9.72 and *q *=

ε0 = stress dependent strain

0.298. Findley's equation, when plotted over the

Table 16 data points is shown in Figure 64, but the

which is dependent on stress level

match is not very clear because of the scatter in

the data. If the tests had been continued over a

longer time, a more discernible creep strain might

have developed. The data at room temperature

of stress.

and low temperature had not shown any trend of

increasing; therefore, they were not analyzed with

Parameters *p *and *q *are known as creep param-

Findley's equation. It must be noted that Findley's

eters. To obtain the particular values of *p *and *q,*

theory applies very well to viscoelastic polymers,

eq 12 can be rearranged and written in the fol-

but in FRC composites rebars, when the stress is

lowing form:

applied in the fiber direction, the behavior is not

totally viscoelastic. In fact, with a higher volume

log (*e * *e*0 ) = log (*p*) + *q *log (*t*/*t*0)

(13)

fraction of glass fibers oriented in the loading

Equation 13 represents a straight line of slope

direction, creep in FRP composites is not expected

to be a problem.

1300

1280

1260

1240

1220

1200

1180

1160

Data Points

1140

Findley's Eq.

1120

1100

0

500

1000

1500

2000

2500

3000

3500

4000

Number of Hours

46