effective prestress

effective prestress

The stress remaining in concrete due to prestressing after loss of prestress; includes the effect of the weight of the member, but excludes the effect of any superimposed load.
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where [alpha] is the ratio of the prestress at the critical section to the fully effective prestress of the strands, which can be estimated as the distance ([l.sub.c]) from the member end to the critical section divided by the transfer length ([l.sub.t]) as shown in Figure 2.
Since [f.sub.pc] is a function of the combinations of several random variables, such as the effective prestress ([f.sub.pe]), sectional area of tendon ([A.sub.ps]), and sectional area of the PHC slab ([A.sub.g] = [b.sub.w][d.sub.p]), this study assumed a normal distribution of these variables ([f.sub.pe], [b.sub.w], [d.sub.p]) and then generated 1.0 x [10.sup.6] random numbers for each random variable through a Monte Carlo simulation to determine the COV and bias factor of [f.sub.pc].
According to equations (7), (8) and (9) coefficient a depends on the initial prestress, the effective prestress transferred to the pretensioned member and Poissons effect of the concrete and pretensioned strand, which causes radial tensile stresses.
According to AASHTO limitations, the target effective prestress force in external pre-stressing strands was 60% of the breaking strength.
No external point load was applied in the first load step, the initial prestrain due to prestressing was applied to the girders, and the initial strains for real constant for prestressing strands were determined from effective prestress ([f.sub.pe]) and the modulus of elasticity ([E.sub.ps]).
Prestressed concrete (PSC) beams have been widely used in highway and railway bridges, in which the effective prestress is one key factor influencing the bridge serviceability and safety.
(3) For the internal prestressed tendons of widespread PSC box girder bridges, the EM sensors installed in the construction stage can be used for the real-time monitoring of effective prestress force in the service process of bridges, which would provide the basis for the long-term performance assessment of the structures.
Finally, the effective prestresses [[sigma].sub.pe] can be expressed by
The effective prestresses are converted into the temperature loads, and the temperature loads are applied to the anchor cable elements [21].
There are two load steps in the model; the first step only counts the response of beam under the effective prestressed force and its own weight; the second step is gradually applying displacement on the mid of the beam span.

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