PSI - Issue 64

Tom Argyle et al. / Procedia Structural Integrity 64 (2024) 1376–1385 Argyle et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 10. (a) Stage 1: one steel plate left at each zone; (b) Stage 2: complete CFRP rods installed

The final design was composed of 12 mm pultruded carbon fibre rods at spacings ranging from 85 to 150 mm spacing, with characteristic tensile strength and modulus of elasticity of 2000 MPa and 155 GPa, respectively. The rods were designed to be placed into 20 x 20 mm grooves cut on top of the deck and filled with an epoxy adhesive. As part of the detailed design the following construction sequence was proposed: • Closure of one lane to all public traffic and works area protected with traffic management. • Removal of surfacing and waterproofing. • Steel plate removal leaving a minimum of one effective steel plate at each zone to ensure residual capacity. • Undertake saw cutting grooves for the NSM CFRP rods and concrete repair, including reinstatement of any damaged concrete and repair of any cracking present from previous overstress. • Installation of the NSM CFRP strengthening. • Remove remaining steel plates upon cure of the epoxy resin and install the CFRP rods over the remaining area. • Application of compatible waterproofing system and re-surfacing following the prescribed sequence. • Shift to the other lane and repeat above sequence. From the results of the offsite trial on surfacing effects on resin performance, described in Section 5, and a 2D transient heat transfer analysis using a finite element analysis package Abaqus (2019), a sequenced approach to application of surfaced was proposed to ensure that the bridge remained adequate for the temporary loading condition. The binder course was installed in sequenced strips, such that a minimum quantity of CFRP rods were below 50ºC at all times – this ensured sufficient structural capacity during the works. The insulation of the binder then allowed the full surface course to be applied without loss of strength of the CFRP system. The design was subject to an Independent Category 3 check by WSP due to its complexity. 7. Construction The strengthening works to Swanley I/C East by Octavius commenced in July 2023 and completed in November 2023. A total of 180 CFRP rods were installed totalling circa of 2.2 km, and 1.4 tonnes of resin were used to bond the rods to the deck slab. Fig. 11 shows a summary of the strengthening construction sequencing.