Earthquake response and rehabilitation of critical underground lifelines reinforced with cured in place pipe liner technologies under transient ground deformations
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Seismic vulnerability and extensive damage to underground lifeline network, causing significant life and economic losses, have been observed and documented in past earthquakes. Seismic retrofit of critical underground pipelines has become an urgent need of our society to improve the performance and serviceability of these critical lifeline systems as well as to enhance public safety. The cured in place pipe (CIPP) liner technology consists of installing flexible polymeric liners with thermosetting resin inside existing pipelines. Compared with traditional expensive and disruptive excavation and replacement of aging and structurally unsound pipelines, CIPP liner technology provides an economic and environmentally friendly alternative for pipeline rehabilitation. However, the lack of verification and quantification of the seismic performance of CIPP liner-reinforced pipelines under transient ground deformations (TGD) remains a critical deficiency in current practice. Full-scale quasi-static and dynamic tests were performed on nine water-pressurized ductile iron (DI) pipelines (6.0 in. nominal diameter and 30 ft. nominal length) utilizing the two re-locatable shake tables at the NEES Site of University at Buffalo (UB). The DI pipeline specimens were divided into two groups and retrofitted with two types of CIPP liners, the InsituMain ® liner and the Starline ® 2000 liner, respectively, which are commonly used in underground pipeline construction and rehabilitation in the U.S. The primary objective of the experimental program is to investigate the behavior of the DI pipelines with weak joints or circumferential cracks under quasi-static loading and their seismic performance under TGD. Numerical joint models were developed to simulate the nonlinear hysteretic axial response of the push-on joints strengthened by two different types of CIPP liners under cyclic loadings. The joint models were subsequently incorporated into the simplified pipeline models to simulate the CIPP liner-reinforced joints or cracks in a buried straight continuous or segmental pipeline. Parametric studies were performed to investigate the influence of different components in the pipeline models to the response of the liner-reinforced joint under seismic loadings. Moreover, incremental dynamic analyses (IDA) were performed on straight buried pipelines using an ensemble of 28 pairs of near-fault ground motion records to evaluate and quantify the seismic performance of the CIPP-liner reinforced pipelines under TGD. Both the experimental results and numerical analyses indicate that CIPP liners provide substantial longitudinal stiffness and strength to the joints of DI pipelines and improve significantly their seismic behavior under high intensity of TGD.