Experimental Study on the Reinforcement of Prestressed Concrete Cylinder Pipes with External Prestressed Steel Strands

Abstract

The prestressed concrete cylinder pipe (PCCP) suffers from cracks and degrades due to the prestress loss which is induced by wire breakage. Reinforcement with external prestressed strands is an option to return the deteriorating pipe’s ability to withstand internal pressures. This reinforcement contributes to actively compensating for the prestress loss caused by broken wires at an economic price. The crack propagation in the core is constrained by the strands. Moreover, the high tensile strength of strands does not decrease with an increase in the bending angle. It is also unnecessary to dewater the pipes during construction. To evaluate the reinforcement effect, a prototype test of a PCCP was performed in an assembled apparatus. The apparatus was mainly constituted by two PCCPs whose internal diameter is 2000 mm. The status of each component of the pipe was measured by resistance strain gauges in three sections along the axial direction at inverted (360°), crown (180°), and spring-line (90°, 270°) orientations. The maximum width of the cracks in the outer concrete core at spring-line reduced from 1.2 to 0.1 mm after strengthening. The cracks of the core concrete changed slightly when the internal water pressure increased to the design pressure of 0.9 MPa. The strengthened pipe was capable of sustaining the design internal water pressure and the water tightness property was in a good state. The strains of the steel strands were all below the tensile strain level. The reinforcement of the PCCP with external prestressed steel strands is able to meet the strengthen requirement of the test.

Damage evaluation of a PCCP joint with a localized soil void and broken wires

“…Due to the destruction of the stress balance, the stress concentration and damaged regions of mortar coating appeared near the broken point, which was in agreement with the observation in the prototype test (Zhao et al, 2019).…”

A century on diameter measurement techniques in cylindrical structures

“…These developments had impact in topics not directly linked to diameter measurement but which need the assessment of this parameter. A classic example is the monitoring of pipes subjected to a wide pressure range that will induce changes in their diameters, which may be within certain limits [20][21][22][23]. Among a relatively large number of optical techniques devised to perform such measurement the ones based in optical fibers are particularly appellative due to the favorable characteristics of these structures, well known in the context of optical fiber sensing [24][25][26][27][28][29].…”

Theoretical Study and Application of the Reinforcement of Prestressed Concrete Cylinder Pipes with External Prestressed Steel Strands

“…Key parameters of the adopted strand are given in Table 3. For the utilized split wedge without jacking force, ∆l re = 6 mm (measured in the prototype test [29]). Given µ = 0.1, the calculated radius of the strand wrapped outside the pipe, r st , and the retraction length, l re , can be known as follows:…”

“…A prototype test of ECP reinforced by steel strands with the fixed spacing calculated in Section 3.2 was performed in an assembled apparatus (Figure 7). The apparatus was mainly constituted by two ECPs, whose internal diameters were 2000 mm [29]. The adopted pipes were exactly the same as those given in Section 3.1.…”

“…The entire test process involved five load stages, namely, (1) increasing the internal water pressure to the working pressure (0-0.6 MPa), (2) cutting the prestressing wires manually until the cracks propagated in the concrete core (0.6 MPa), (3) decreasing the internal water pressure to the artesian pressure (0.6-0.2 MPa), (4) performing the tensioning operation after wrapping the strands externally around the pipe (0.2 MPa), and (5) increasing the internal water pressure to the original level (0.2-0.6 MPa). In most of the actual pipe failures modes, most pipes failed at 4 or 8 o clock, not at the invert, crown, or spring-lines [29]. The position of 8 o clock was chosen in this test for convenience (Figure 8).…”