Performance of in situ stitches in precast segmental bridges

Abstract

In situ concrete stitching with subsequent prestressing is often used in construction to join together precast concrete segments. An example of an application is the stitching of the approaching decks of precast segmental bridges constructed using the balanced cantilever method. The relatively narrow stitches used in segmental bridges are often provided with nominal reinforcement only. Therefore, the in situ stitch is a location of potential weakness, but relatively little work has been done in this area. In light of this, extensive experimental and numerical studies on the behaviour of precast concrete members with in situ concrete stitches have been conducted. The effects of stitch width, prestressing force, concrete strength, bonding of tendon and provision of shear keys on the performance of such members are presented in this paper. Unlike members that are continuously cast, cracking initiates along the construction joint between the precast segment and the stitch at low load levels for members with in situ stitches, while no cracking is observed elsewhere. The cracks widen extensively as the load level increases and can become detrimental to the serviceability of the members. Such members should be designed so that the joints are subject to no tension under service load. Notation G c pre-crack shear modulus G c,cr post-crack shear modulus q bond stress u slip of tendon β shear retention factor

Influencing Factors and Shear Capacity Formula of Single-Keyed Dry Joints in Segmental Precast Bridges under Direct Shear Loading

“…Obviously, R Av of the proposed formula Equation (20) is 0.998, which is the closest to 1.0 compared with other formulas. It indicates the calculated results obtained by Equation (20) are highly consistent with the existing experimental results. In the second place, calculated results obtained according to AASHTO also showed decent consistency with test results.…”

“…All the specimens are the same as in Table 4. Different from AASHTO overestimating the shear capacity of the keyed dry joint, the predicted results of Equation (20) showed perfect consistency with both tests and the FE simulation results.…”

“…Through regression analysis, the relation between experimental and predicted joint shear strength of different formulas is presented in Figure 18, values of R 2 are also listed in Table 6, which reflects the prediction accuracy of the formulas. Similarly, R 2 of Equation (20) proposed in this paper is the 0.982, which showed higher accuracy in predicting the shear capacity of single keyed dry joint than other existing formulas.…”

Experimental and Analytical Study on Pull-out Force of Steel Fiber-Reinforced Concrete Blocks

“…In addition, the fibers adding might improve the bonding of reinforcement bars and improve some other characteristics of RC [3]. Generally, the bonding of reinforcement bars in concrete is necessary in areas subject to shearing and concentration of stress such as narrow stitches in bridges, concentrated load bearings and beam column joints in buildings [4][5][6][7]. The strength of bond for the reinforcing bars during the final strength process must also be taken into account.…”

Shear performance of single-keyed dry joints between reactive power concrete and high strength concrete in push-off tests

“… 5 Nevertheless, shear-keyed joint specimens, subjected to pure bending moment, pure shear force, or a combination of moment and shear, would appear different fracture phenomena. 6 Jointed concrete structures might also be damaged as a result of the tearing model of fracture. 7 – 9 …”