Cross-river bridges located in seismically active areas are exposed to two major natural hazards, namely earthquakes and flooding. As the scour depth increases, more parts of the bridge substructure will inevitably be exposed to unfavorable conditions such as chloride ion (${\mathrm{Cl}}^{-}$) corrosion. To investigate the seismic performance of highway bridges under the action of scour and ${\mathrm{Cl}}^{-}$ corrosion, a spatial finite element dynamic model of a continuous rigid bridge was established and a ${\mathrm{Cl}}^{-}$-accelerated electrochemical corrosion test and quasi-static test were carried out. The results showed that a reasonable scour depth and the combination sub-factors under the joint probability density of scour action and seismic action can be obtained to establish the combined expression of the action effect. ${\mathrm{Cl}}^{-}$ corrosion can cause a reduction in displacement ductility, load-bearing, and energy dissipation capacity, and increase inequivalent viscous damping coefficient of the columns. Seismic damage of the columns grows linearly to twice the ultimate displacement under ${\mathrm{Cl}}^{-}$ corrosion, which becomes more significant with the increase of the reinforcement ratio.

The paper focuses on the material mechanics properties of reinforced concrete and steel casing composite concrete under pseudo-static loads and their application in structure. Although elevated pile-group foundation is widely used in bridge, port and ocean engineering, the seismic performance of this type of foundation still need further study. Four scale-specimens of the elevated pile-group foundation were manufactured by these two kinds of concrete and seismic performance characteristic of each specimen were compared. Meanwhile, the special soil box was designed and built to consider soil-pile-superstructure interaction. According to the test result, the peak strength of strengthening specimens is about 1.77 times of the others and the ultimate displacement is 1.66 times of the RC specimens. Additionally, the dissipated hysteric energy capability of strengthening specimens is more than 2.15 times of the others as the equivalent viscous damping ratio is reduced by 50%. The pinching effect of first two specimens is more obvious than latter two specimens and the hysteretic loops of reinforced specimens are more plumpness. The pseudo-static tests also provided the data to quantitatively assessment the positive effect of steel casing composite concrete in aseismatic design of bridge.

Grouted sleeve connections are widely employed in the substructures of prefabricated bridges. After installation, the grout filling condition inside the sleeves cannot be directly inspected, while grouting defects may significantly compromise the mechanical performance of the piers. This study investigates the feasibility of using the non-destructive impact-echo method to detect grouting defects in sleeves. Finite element simulation was conducted to analyze the influence of the distance between the impact point and the signal acquisition point on detection accuracy, revealing that a distance of 40–60 mm yields optimal results. Experimental findings demonstrate that the method can effectively identify grouting defects in double-row sleeves, although it cannot precisely locate the defective sleeve. A novel analytical approach is proposed, using the thickness frequency and its modes of fully grouted specimens as a benchmark. By comparing thickness frequencies at different measurement points, grout quality can be intuitively evaluated. Validation using a six-sleeve model with varying grouting densities confirmed the method’s effectiveness in detecting grouting defects in non-boundary sleeves and its practical applicability in engineering.

Ultra high performance concrete (UHPC) is a new type of cement based composites with high strength and excellent durability. Firstly, this paper introduces the development history and technical performance of UHPC, then application of UHPC in lifeline engineering is summarized: the UHPC application examples of 18 bridges abroad; the application of UHPC in bridge joints and bridge deck pavement; advantages of its anti-permeability and frost resistance in combination with the durability of UHPC in pipeline transportation. Based on this, the paper makes an improvement on the UHPC concrete formula, which makes it easier to be popularized in China, and 2 sets of UHPC-ECC composite pipe specimens were designed and tested for the first time. Experiments showed that the composite pipe has advantage of high strength, corrosion resistance, no leakage, and it can be widely used in the field of petroleum and hazardous chemicals transportation and so on.