Shen Li

Steel-reinforced concrete (SRC) frame-bent hybrid structures are widely used in conventional island buildings of nuclear power plants because of their favorable seismic performance and economic efficiency. However, the seismic fragility of these structures has not been adequately investigated. In this study, the main turbine building of the CAP1400 nuclear power plant in Rongcheng, Shandong Province, China, was selected as the prototype. A three-bay frame-bent substructure was extracted, and a 1/7-scale model was designed for pseudo-dynamic testing to investigate the evolution of seismic damage and the failure mechanisms of the structure. Based on the experimental results, a refined numerical model was developed in OpenSees. Incremental dynamic analysis (IDA) was subsequently conducted to evaluate the seismic fragility of the SRC frame-bent main turbine building under far-field and near-fault ground motions. The results indicate that the structural stiffness progressively decreases with increasing seismic demand because of concrete cracking and cumulative damage. Damage is primarily concentrated in the short columns, beam-column joints, and column bases. The fragility response also exhibits pronounced directional dependence. Because of the lower lateral stiffness in the X direction, the structure develops larger interstory drift demands and higher probabilities of exceeding the prescribed damage states in the X direction than in the Y direction. For the selected ground-motion suites, near-fault records generally produce slightly higher exceedance probabilities than far-field records at the same peak ground acceleration (PGA), with a maximum difference of 3.68%. However, the magnitude of this difference varies with the damage state, excitation direction, and ground-motion intensity. These findings indicate that pulse-like near-fault ground motions may have a measurable but moderate effect on the seismic fragility of SRC frame-bent main turbine buildings. This study establishes an experimentally validated framework for assessing the seismic fragility of SRC frame-bent structures in nuclear power plants and identifies their vulnerable components, dominant damage mechanisms, and fragility characteristics under different types of ground-motion input.

Polymer concrete (PC) refers to the use of a polymer as a replacement for cement, enhancing the mechanical and durability properties of traditional concrete. Introduced in the late 1950s and gaining prominence in the 1970s, the use of PCs has been rapidly increasing across various industries. This paper provides a comprehensive review, beginning with a brief historical overview of polymer concrete. It examines key review papers and books related to PC, summarizing the various materials commonly used in its formulation, such as resins, fillers, fibers, and nanofillers. Additionally, the paper explores the diverse applications of polymer concrete, ranging from structural repairs and architectural cladding to advanced uses in electrical insulation and 3D printing, with special attention given to sustainability aspects. Through this review, the paper highlights the growing importance of polymer concrete in modern construction and infrastructure projects.

This paper introduces a beam–column joint with an L-shaped component formed by combining two traditional semi-rigid connection methods, namely top and bottom angle steel connections and end-plate connections. Test studies and finite element simulations are performed on two designed specimens (LJD-1 and LJD-2). The reliability of the finite element model is confirmed, and the hysteresis curves are found to be relatively full, indicating excellent energy dissipation capacity. Moreover, it is revealed that the larger the joint length, the better the improvement in load-bearing capacity and ductility. Based on this, a finite element simulation is conducted considering the joint configuration, thickness of the vertical and horizontal plates, length of the horizontal plate, thickness of the end-plate, and the number of haunches. The optimal ranges for each parameter are determined.

The present study proposes a variable replaceable link for high-strength steel frames with Y-eccentric braces designed to effectively dissipate earthquake energy by confining plastic deformation to its central zone. This unique feature allows for easy post-earthquake recovery or replacement. To investigate the seismic performance of such structures, a comprehensive finite element numerical parametric analysis is conducted using ABAQUS software. Various parameters, including the length of the central zone, replaceable link length, span, and steel grade are considered to optimize the structural design. This study examines the failure modes, hysteretic behavior, bearing capacity, plastic rotation of the replaceable link, and ductility of structures under cyclic loading. The results indicate that reducing the span and utilizing high-strength steel significantly enhance the ductility and ultimate bearing capacity of the structure. This approach also reduces the cross-sectional dimensions, saves steel material, and limits the development area of plasticity, thereby facilitating post-earthquake repair of links after rare earthquakes. An optimal length of the link improves the structural stiffness and energy dissipation capacity. However, if it is too short or too long, it complicates post-earthquake repairs and impairs energy dissipation performance. The conclusions drawn from this research aim to provide valuable insights and theoretical foundations for future structural designs.

This paper proposes a new type of variable-cross-section replaceable link that can isolate the plastic deformation. The link and the frame beam connect with the expanding section by a bolt along the flange and web separately. It is easy to design an elastic bolt, reduce bolt slippage, and facilitate link replacement after an earthquake. Considering the large elastic deformation range of high-strength steel and the superior plastic deformation of the new type of replaceable link, a high-strength eccentrically braced steel frame with a variable-section replaceable link is raised by setting a new type of variable-section replaceable link in the eccentrically braced steel frame. Then, the existing end plate connection replaceable link test specimen is simulated and verified by using ABAQUS software. The finite element model of the high-strength eccentrically braced steel frame with a variable-cross-section replaceable link is established, and the bearing capacity, stiffness, plastic rotation, plastic distribution, and other bearing mechanisms of the structure are studied by cyclic loading. The length of the energy-consuming region (e), the steel strength of the link and other components, and the length of the replaceable link (e’) are compared and analyzed with regard to the seismic performance of the structure. The results are of great significance for understanding and exploring the force mechanism, energy dissipation characteristics of the new variable-section replaceable link, and the seismic performance of the high-strength eccentrically braced steel frame, and it also provides a reference for subsequent research.