This study introduces an alternative approach to the assessment of the earthquake resistance of existing buildings and the evaluation of the requirements for seismic retrofit through external stiffening. Instead of assessing individual structural components, we evaluate the entire building using a nonlinear static pushover analysis. Earthquake resistance of the building is defined as a ratio between the total energy that the existing structure can absorb and the energy at its ideal (upgraded) state estimated using the capacity curves obtained from the pushover analysis. The required retrofitting can then be assessed as the stiffness needed to be added to achieve the desired resistance. The study establishes the definition for the ideal capacity of an existing structure, safe displacement limits, and a procedure for deriving the target capacity curves and earthquake-resistance factors. The proposed procedure is applied to a benchmark example, demonstrating that upgrading sub-standard RC structures can be achieved by adding external stiffening members without strengthening individual components. The study also shows that traditional assessment procedures have limited capability to evaluate earthquake resistance in existing buildings with low ductility. The developed procedure provides an essential tool for comparative assessments of retrofitting scenarios and profitability evaluations.

Corrosion-induced degradation in concrete and reinforced concrete (RC) structures, often initiated within the first few decades of their lifespan, significantly challenges seismic resistance. While existing research tools can assess performance, they fall short in predicting changes in seismic resistance resulting from alterations in the core properties of RC structures. To bridge this gap, we introduce a numerical seismic resistance prediction method (SRPM) specifically designed to predict changes in the seismic resistance of structures, including those reinforced with carbon-fiber-reinforced polymer (CFRP), known for its non-corrosive properties. This study utilizes classical models to estimate corrosiveness and employs these models alongside section strength predictions to gauge durability. The nonlinear static pushover analysis (POA) model is implemented utilizing SAP-2000 and Response-2000 software. A comparative analysis between steel-reinforced and carbon-fiber-reinforced polymer concrete (CRC) structures reveals distinct differences in their seismic resistance over time. Notably, steel-reinforced structures experience a significant decrease in their ability to dissipate seismic energy, losing 54.4% of their capacity after 170 years. In contrast, CFRP-reinforced structures exhibit a much slower degradation rate, with only 25.5% reduction over the same period. The discrepancy demonstrates CFRP’s superior durability and ability to maintain structural integrity in the face of seismic stresses.

Rigid reinforced concrete (RC) frames are generally adopted as stiff elements to make the building structures resistant to seismic forces. However, a method has yet to be fully sought to provide earthquake resistance through optimizing beam and column performance in a rigid frame. Due to its high corrosion resistance, the integration of CFRP offers an opportunity to reduce frequent repairs and increase durability. This paper presents the structural response of CFRP beams integrated into rigid frames when subjected to seismic events. Without any design provision for CFRP systems in extreme events, multiscale simulations and parametric analyses were performed to optimize the residual state and global performance. Macroparameters, represented by the ductility ratio and microfactors, have been analyzed using a customized version of the modified compression field theory (MCFT). The main parameters considered were reinforcement under tension and compression, strength of concrete, height-to-width ratio, section cover, and confinement level, all of which are important to understand their influence on seismic performance. The parametric analysis results highlight the increased ductility and higher load-carrying capacity of the CFRP-reinforced tested component compared to the RC component. These results shed light on the possibility of designing CFRP-reinforced concrete components that could improve ductile frames with increased energy dissipation and be suitable for applications in non-corrosive seismic-resistant buildings. This also shows reduced brittleness and enhancement in the failure mode. Numerical simulations and experimental results showed a strong correlation with a deviation of about 8.3%, underlining the reliability of the proposed approach for designing seismic-resistant CFRP-reinforced structures.

Reinforced concrete structures are increasingly vulnerable to deterioration by steel reinforcement corrosion, resulting in severe loss of fracture strength and service life, particularly in severe environmental exposure. Carbon fiber reinforced polymers (CFRPs) are a corrosion‐resistant alternative with high‐strength performance for construction in seismic and corrosive environments. This work studies the structural behavior of CFRP‐reinforced concrete (CRC) frames through numerical simulation and validates them against experimental results. Five full‐size CRC frames, with four beams and four columns in a grid arrangement, were loaded monotonically and reversed laterally under constant gravity loads. CFRP bars were used as longitudinal and transverse reinforcement. Parametric analysis was conducted using nonlinear pushover analysis (POA) in SAP2000 (v2014) based on reinforcement area and cross‐section member variations. The result shows that CRC frames have sufficient strength, energy dissipation, and deformation capacity, which justifies using CFRP as a long‐term alternative to steel in seismically active and corrosive environments. The study's findings confirm the feasibility of designing large‐scale ductile structures by driving key structural parameters, such as concrete compressive strength and beam‐column rotational stiffness. Additionally, doubling the rotational stiffness caused the ductility ratio to be fourfold. Additionally, enhancing concrete confinement, particularly with lateral confinement stress being four times greater than vertical stress, resulted in a nearly 187% ductility increase under unconfined circumstances. These results emphasize joint stiffness and confinement's crucial role in achieving optimum seismic performance.