The cracks in the specimens with bonded tendon
initiated at the center and propagated toward the ends.
A bonded tendon
, however, is made of multiple post-tensioning strands and, by design, forms a continuous bond along its length with the surrounding concrete slab, beam, or girder.
where [[epsilon].sub.xx] and [[epsilon].sub.xxt] are the horizontal normal strains of concrete and bonded tendon, respectively; [E.sub.con] and [E.sub.tend] denote Young's modulus of concrete and tendon; and [V.sub.con] and [V.sub.tend] denote the volumes of concrete and tendon.
As the bonded tendon has a much smaller mass compared to the concrete bridge, its kinetic energy can be neglected, and the kinetic energy of the bridge can be expressed by
However, the application of EM sensing in bonded tendons requires further investigation due to the possible influence of plastic duct and cement grouts on measurement results.
In this paper, the feasibility of elastomagnetic (EM) sensors in monitoring the long-term prestress loss in bonded tendons is experimentally investigated, and the influence of ambient temperature, water, eccentricity ratio, plastic duct, and cement grouts on the test results is discussed.
The beam cross-section is shown in Figure 1, and the designed strength grade of concrete was C40; the prestressing steel was [[phi].sup.s] 15 steel strand, the tensile strength of which was [f.sub.ptk] = 1860 N/[mm.sup.2], the inner diameter of corrugated duct was 50 mm, and initial tensile stress [[sigma].sub.con] = 0.75/ptk; bonded tendons
were used; the material grade of H-steel (H x B x [t.sub.1] x [t.sub.2] = 100 mm x 100 mm x 6 mm x 8 mm) was Q235, and H-steel was symmetrically arranged in beam cross-section; stirrups are [[phi]12@100 and material was HPB235; the tendon profile is shown in Figure 2.
* Un-bonded tendons which reduce labor costs as compared to bonded tendons
, which require a separate labor crew.
The perfect bond is applicable to the analysis of reinforced concrete and posttensioned concrete with bonded tendons
. The same degrees of freedom were assigned to concrete and reinforcement nodes occupying a single location.
An analytical model, based on the stress field theory, is developed and proposed here, which can be helpful for understanding the actual behaviour of externally prestressed concrete girders, by comparing it to structures with bonded tendons
. A numerical example is developed and interaction domains are given for an example of common box sections.
Traditionally, prestressing of deflected pieces of wood has been carried out using bonded tendons. These tendons are made using steel bars or plates [1-5] or by using FRP fibre-reinforced polymer [2, 6-10].
One of the main problems arising from tensioning systems using bonded tendons is the delamination in the anchorage area due to the high stresses concentration [11, 12].