Effect of the location of broken wire wraps on the failure pressure of prestressed concrete cylinder pipes

Abstract

1 Introduction and backgroundPrestressed concrete cylinder pipe (PCCP) has been used for large-diameter water transmission and distribution mains in the United States as lined cylinder pipe (LCP) since 1942 and as embedded cylinder pipe (ECP) from 1952 onwards. Many classes of ECP have been standardized by the industry based on their internal fluid pressure capacity and backfill earth pressure capacity. The concrete core and prestressing wire are the main structural components, while the steel cylinder acts primarily as a water barrier. The prestressing wire wraps generate a uniform compressive force in the core that offsets the tensile stresses developed in the concrete due to the internal fluid pressure. A mortar or concrete coating surrounds the prestressing wire, embedding the wraps in an alkaline environment to protect them from external corrosive influences and physical damage such as corrosion. Breakage of prestressing wire wraps is a common occurrence in PCCP and is a result of damage due to corrosion, hydrogen embrittlement, overloading or manufacturing defects. Corrosion in immersed concrete structures can be due to earlyage cracks that leave paths for aggressive media, thus compromising the durability of the element [1], [2]. Corrosion and the subsequent breakage of an individual prestressing wire wrap reduces the strength of the pipe at that location [3]. If corrosion continues, multiple wire wrap breaks may occur in the same region, further reducing the strength of the pipe and leading to failure. Since this wire breakage is the primary cause of the structural deterioration of PCCP water mains, it is important to understand the effect of its length and location. The class of prestressing wire with its corresponding ultimate tensile strength is also an important factor for the overall strength of the pipe. Understanding the behaviour of PCCP under combined internal and external loading has gradually developed since the mid 1950s, and the evolution of the standards has been a direct result of investigations into PCCP failures [4], [5]. Although there have been significant improvements in the design and manufacture of PCCP, understanding damaged PCCP, which is intrinsic to this, is still under investigation. A study performed by Zarghami et al. [6], which compared experimental hydrostatic pressure test results with results from numerical FEM, found that the final failure mode for large-diameter PCCP was caused by increased stress in the prestressing wire wraps rather than crushing of the concrete. Liu et al.[2] presented a constitutive model for concrete hardening which considered the degree of hydration concept. The approach allowed the effects of both age and temperature on hydration to be taken into account simultaneously when modelling the early-age behaviour of underground precast concrete pipes. The study used the proposed numerical model to investigate the influences of mix design, casting scheme and curing conditions on the early-age behaviour of the pipes [2].Ojdrovic et al. [7] used finite ele...

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

“…Additionally, it is not practical to fully model the actual condition of each damaged joint. To simplify the modeling details and reduce computational costs, in previous studies the joints were assumed to conservatively have no interaction or full interaction between the bell end and spigot end (Alavinasab et al, 2013;Alavinasab and Hajali, 2014;Hajali et al, 2015). In this paper, the interactions between the PCCPs were defined by normal behavior (hard contact) and tangential behavior (contact algorithm).…”

“…As the number of broken wires increases, the bearing capacity of the PCCP sharply decreases, and the risk of pipe burst increases. Moreover, the wire break damage of the bell-and-spigot joint can decrease the overall strength of the PCCP more than that in the barrel of the pipe (Alavinasab et al, 2013;Hajali et al, 2015Hajali et al, , 2016b. Few studies available in the literature have thoroughly investigated the possible coupling disaster of PCCP pipelines in service.…”

Mechanical responses of bell‐and‐spigot joints in buried prestressed concrete cylinder pipe under coupled service and surcharge loads

“…Sun et al 7 analyzed the key factors affecting the rotation angle of PCCP on soft soil foundation based on field tests and numerical calculations, and proposed some measures to control the rotation angle of joint. Hajali et al [8][9][10] studied the effect of wire broken position and number on the ultimate internal pressure of PCCP through a three-dimensional (3D) nonlinear finite element model, and the interaction between bell and spigot was considered, the results of which showed that the occurrence of wire broken at joint can influence the performance of PCCP mostly. Hu et al 11 analyzed the relationship between settlement and rotation angle at joints through laboratory tests, and studied the strain distribution at joints.…”

Using Externally Bonded CFRP to Repair a PCCP with Broken Wires under Combined Loads

“…They suggested that broken wires do not have a significant impact on a PCCP with good mortar adhesion. Hajali et al [24][25][26] considered the pipe-soil interaction, the interaction between neighboring pipes, and internal and external loads in modeling the effects of the position and number of broken wires on a PCCP using a three-dimensional finite element model.…”