Seismic Repair of Severely Damaged Precast RC Bridge Columns Connected With Grouted Splice Sleeves

Abstract eng:
A repair technique for severely damaged precast reinforced concrete (RC) bridge columns with grouted splice sleeve (GSS) connections has been developed that utilizes a carbon fiber-reinforced polymer (CFRP) shell and epoxy anchored headed bars to relocate the column plastic hinge. Four original specimens were built using an Accelerated Bridge Construction (ABC) technique with two different GSS systems and were tested to failure using cyclic quasi-static loads. One GSS system was used to connect a precast RC bridge pier cap to a precast column. This GSS system consists of mild steel bars that are threaded into the sleeve at one end and grouted at the other. The second GSS system consists of mild steel bars that are grouted at both ends of the sleeve and is used to connect a RC footing and a precast column. Failure of the four original specimens occurred at drift ratios between 5.6% and 8.0% with longitudinal bar fracture or pullout from the GSS connections. Structural components with this type of damage usually require replacement. However, using the repair method developed, repair of precast RC columns connected using GSS with severe damage is possible. The damaged plastic hinge of the columns was repaired by increasing the column cross section from a 53 cm octagonal section to a 76 cm diameter circular section over a column length of 46 cm. The repair was constructed using prefabricated CFRP shells to provide confinement and also act as concrete formwork. Inside the prefabricated CFRP shells, headed mild steel bars were epoxy anchored into the pier cap and footing to increase the flexural capacity of the plastic hinge region of the damaged columns. Subsequently, nonshrink or expansive concrete was used to fill the void between the original columns and CFRP shells. The use of expansive instead of nonshrink concrete converts the confinement provided by the CFRP shell from passive to active by pre-tensioning the CFRP shell. The repair method successfully relocated the plastic hinge in the original column section adjacent to the repair and was capable of restoring the diminished load and displacement capacity. Results of the tests conducted on the repaired column assemblies in terms of load capacity and displacement ductility are presented and compared with the original. Strut-and-tie models (STM) were also developed for the original and repaired precast RC bridge specimens. Generic modeling parameters were established for the STM procedure, enabling the models to be adapted to new repair applications. Special attention is focused on the struts within the CFRP shell. All specimens were modeled using sectional analysis using the predicted STM load to estimate a bilinear force-displacement response envelopes; these predictions show satisfactory agreement with the experiments of the original and repaired bridge specimens in terms of initial stiffness, lateral load and displacement capacity. The repair method is a viable and cost-effective technique for rapid seismic repair of severely damaged precast bridge assemblies.

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