The excavation of pits will induce the vertical displacement of tunnels and lead to engineering problems. The shape as well as size of a pit, and the complex spatial position relationship between the pit and tunnel will induce different deformation responses of tunnel structures; however, the degree to which each factor influences tunnel structure deformation is still unclear. This paper studied the impact of excavation on the deformation of tunnels via a combination of numerical simulation and orthogonal tests. The deformation of tunnels induced by excavation was studied using a numerical method, after which the sensitivity of influencing factors to tunnel deformation was studied by means of range and variance analyses through a four-factor and three-level orthogonal test. The results show that, for a foundation pit with a long side perpendicular to the tunnel longitude, the excavation has the least influence on tunnel deformation. Tunnel deformation increased with an increase in the excavation depth and decreased with an increase in tunnel–pit vertical and horizontal distance. As the plane shape of the foundation pit is 20 m × 45 m, the depth of excavation is 4 m, the pit tunnel vertical distance is 13 m, and the pit tunnel horizontal distance is 28 m, the tunnel has the least deformation. Based on the results of this study, the position relationship between the pit and the tunnel can be optimized in terms of design and construction, and the aim of controlling tunnel deformation can be achieved.
The bond performance of CFRP to concrete plays a vital role in CFRP strengthening on concrete structures. In this paper, an experimental study was carried out to investigate the bond performance of CFRP to concrete with a convex-circular arc interface. The main factors were the curvature of the concrete surface and the bond length and the layers of the CFRP laminate. Based on the experimental results, the failure mode of the bond specimens, the variation of the bond capacity, the CFRP strain, and the bond–slip constitutive model are analyzed. The results showed that most of the specimens failed to peel off the interface concrete, and the bond capacity tended to increase with the increase in bond length when the bond length was within an effective value. When the interface curvature increased to 1/0.8 m, the bond capacity tended to increase due to the CFRP exerting a certain pressure on the concrete surface. The prediction formula of the bond capacity between the CFRP and concrete is proposed considering the influence of the interface curvature. The bond–slip curves are given out based on the finite differential analysis of the strain distribution of CFRP laminates. The accuracy and applicability of the proposed model are verified with a comparison to the test results and other existing models.
The novel precast hybrid coupled wall structure system considers convenience requirements for the production and construction of prefabricated components. In this study, to determine the ultimate shear strength of embedded beam-to-wall connections, four full-scale specimens were meticulously designed using the “weak connections and strong components” methodology. Under low-cycle loading on a coupling steel beam, the experimental results indicated that the shear strength of the specimen was approximately twice that predicted by the Mattock–Gaafar mechanical model employed in Seismic Provisions for Structural Steel Buildings (ANSI/AISC 341-16). Therefore, a mechanical model was established to analyze the force transfer between the steel beam and concrete wall. Finally, design formulas for the shear strength were proposed, in addition to corresponding suggestions for construction reinforcement in the embedded area and adjacent zones.