The experimental results are summarized in Table 5 and include (1) tensile strength, (2) tensile strain, (3) average crack width at 0.2% tensile strain, and (4) average bond strength (u) determined by summing the forces parallel to the reinforcement axis, assuming that the

bond stress levels are distributed uniformly over this length [3], as follows:

Therefore, the three parameters, as shown in Figure 10, the initial stiffness, the value of the softened contact relationship slope, and the maximum

bond stress need calibrating against experiments in order to define the contact model.

The force transferred from the concrete to the reinforcing steel was calculated using Equation (1), while the

bond stress which occured in the reinforcing steel element was obtained by Equation (2).

The most recent consolidated third party cash flow statements which incorporate various Fitch interest-rate and bank

bond stress scenarios, demonstrate a minimum asset parity ratio of 114.3% for the remaining life of the bonds.

The

bond stress was determined using the detachment method or pull-out of the fiber in tension (Valadez, 1999), according to equation 1.

The dimensions arisen during stressing operations, and the

bond stress along the tendon bond length were determined in next steps (Stefanak 2013):

where: [[lambda].sub.1] is the expected pull-out length ratio; [[lambda].sub.2] is the fibre orientation factor; [[lambda].sub.3] is the group reduction factor associated with the number of fibres pulling out per unit area; [tau] is the average

bond stress of a single fibre embedded in the concrete; [V.sub.f] is the fibre volume percentage; [beta] is the bond factor, accordingly to Campione (2008), can be assumed being equal to 0.5 for round fibres, 0.75--for crimped fibres, 1.0--for hooked fibres; [l.sub.f] and [b.sub.f] are the length and the diameter of fibre, respectively.

The

bond stress and the shear resistance in the pre-existing crack portion are assumed to be zero.

Stresses predicted by

bond stress analysis and lap shear strength as a function of adhesive modulus.

where A is the contact area between the inner wall of the steel tube and the core concrete; A = 4(B - 2t)[l.sub.a], where [l.sub.a] is the interface length of the

bond stress between the steel tube and the core concrete.

The

bond stress can be calculated assuming a uniform

bond stress distribution along the embedded length of the bar in concrete using

However, the intensity of the stress is less than the

bond stress.