An experimental study was undertaken to investigate the cyclic behaviour of earthquake- and corrosion-damaged rectangular reinforced concrete (RC) columns. Nine un-corroded columns and nine columns corroded using an external current method were tested to evaluate the effects of reinforcement corrosion level, initial earthquake damage degree (EDD), retrofit method and loading pattern on their cyclic behaviour. The test results indicate that reinforcement corrosion deteriorated the cyclic behaviour of RC columns in terms of strength, ductility, low-cycle fatigue life, secant stiffness and cumulative energy dissipation capacity, while retrofitting with carbon fibre reinforced polymer wraps and high-strength grout greatly improved the cyclic behaviour of both the un-corroded and corroded columns. For columns with an initial EDD of less than about 30%, regardless of whether they were first corroded or not, their strength, fatigue life and cumulative energy dissipation capacity after retrofit were fully restored to the levels prior to earthquake damage, whereas the level of improvement in the initial secant stiffness of damaged columns after retrofit was affected by the reinforcement corrosion level and the initial EDD. The influence of loading pattern on the cumulative energy dissipation capacity of un-corroded and corroded columns was also studied.

This paper aims to contribute to a better understanding of the axial behaviour of rectangular reinforced concrete (RC) columns with large cross-sectional aspect ratios (section depth to width ratios) confined by carbon-fibre-reinforced polymer (CFRP). Three series of rectangular RC columns with cross-sectional aspect ratios of 2·25, 2·0 and 1·8 were tested under monotonic uniaxial compressive loads until failure. The effects of aspect ratios and CFRP anchors on the confinement effectiveness of CFRP wraps for rectangular RC columns were evaluated. The test results indicate that CFRP wraps enhanced the compressive strength of CFRP-confined rectangular RC columns even with a large aspect ratio of 2·25; however, the strength enhancement levels decreased with an increase in aspect ratio. CFRP anchors were effective in restraining concrete from bulging out and thus improved the confinement effectiveness of the CFRP wraps. Based on the test results regarding medium- and large-scale CFRP-confined rectangular RC columns available in the literature and this study, some existing confinement models for rectangular RC columns were assessed and a new analytical model was developed through regression analysis of the database. The proposed analytical model was found to be in good agreement with the test results in the database.

To improve the deformation and energy dissipation capacities of conventionally reinforced coupling beams with low shear span to beam depth ratios, a new method for seismic retrofitting coupling beams using carbon-fibre-reinforced polymer (CFRP) composites is proposed and studied. Experiments are conducted to test four large-scale coupling beams with identical geometries and reinforcement layouts but with different retrofitting schemes. The effects of the arrangement of CFRP sheets and CFRP anchors on the seismic behaviour in terms of strength, stiffness, ductility, energy dissipation capacity and failure modes are evaluated. The study indicates the proposed retrofitting technique is well suited to improving the seismic behaviour of low-slenderness coupling beams in moderate seismic zones. The use of CFRP U-wraps can significantly improve the deformation and cumulative energy dissipation capacities of coupling beams while the beam stiffness can remain nearly constant. By using diagonal CFRP sheets, the strength, stiffness and energy dissipation capacity of coupling beams can be increased. The delamination of CFRP U-wraps can be delayed by using CFRP anchors, but sufficient insertion depth of the anchors is required to avoid their pull-out failure.

This paper investigates the seismic damage behavior of steel pipe pile wharves after pitting corrosion. The seismic intensity is treated as random, and a probabilistic strength model for randomly pitting corroded steel is utilized to assess the seismic response of a typical steel pipe pile wharf. By analyzing the internal force response of each pile and the deformation response of the deck and soil slope, the process of seismic failure in steel pipe pile wharves with different pitting corrosion ratios is investigated. The results demonstrate that pitting corrosion amplifies the internal force within the steel pipe piles, leading to more severe seismic damage. Additionally, probabilistic seismic demand functions are established for the most vulnerable row of piles affected by random pitting corrosion, and the seismic fragility of the pipe pile wharves considering different pitting corrosion ratios is evaluated. These findings provide valuable insights for the design and strengthening of steel pipe pile wharves.

This paper presents experimental and analytical studies on the punching shear behavior of concrete-filled steel-tube (CFT) bridge column to pile-foundation connections. Five CFT bridge column to reinforced-concrete (RC) four-pile cap connections were constructed and tested under monotonic downward vertical loads to the columns, and the effects of the connection details, including embedment depths of CFT columns, shear studs, face annular rings, and headed shear reinforcement, on punching shear behavior were evaluated. Test results indicate that the connection details significantly affected the cracking patterns of pile caps and the failure modes of connections. The use of shear studs, face annular rings, headed shear reinforcement, and reduced embedment depths of CFT columns can substantially enhance the punching shear strength of CFT column to RC-pile cap connections. The tested specimen with a face annular ring welded onto the CFT column base showed the most favorable punching shear behavior with the highest loading capacity and the most ductile failure mode. On the basis of the experimental observations, the effective depths of pile caps for CFT columns under punching were proposed, and then the punching shear strength of the tested connections was predicted using current design codes for the design of RC footings. A modified empirical strength model was also developed on the basis of experimental and finite-element analysis results.

An experimental investigation on the seismic behavior of deep reinforced concrete coupling beams was conducted by testing six large-scale coupling beams with different reinforcement layouts. The reinforcement layouts included using concealed beams similar to wall boundary elements, U-shaped steel, through-slits, diagonally embedded steel plates and diagonal rebar bundles without confining ties. Test results indicate that coupling beams with diagonal steel plates or diagonal rebar bundles without confining ties showed the most desirable deformation and energy-dissipation capacities under cyclic loading, and thus are viable alternatives for coupled wall systems in seismic zones.