| Abstract: |
The P-Delta (P-Δ and P-δ) effect represents a critical second-order phenomenon influencing the stability, strength, and serviceability of steel frames subjected to combined gravity and lateral loads. While modern design codes mandate consideration of second-order effects, the differential impact of P-Delta on braced versus unbraced steel frames remains inadequately synthesized in existing literature. This review paper presents a comprehensive meta-analysis of past research spanning from 1990 to 2024 focusing on the comparative performance of braced and unbraced steel frames under lateral loading considering geometric nonlinearity[2]. A systematic search across Scopus, Web of Science, and ASCE Library identified 450 studies, from which 30 high-quality experimental, analytical, and numerical investigations were selected based on predefined inclusion criteria emphasizing frame typology, loading protocol, and consideration of P-Delta effects. Quantitative synthesis reveals that P-Delta effects amplify inter-story drift by 8-15% in concentrically braced frames (CBFs) and 18-42% in unbraced moment-resisting frames (MRFs) under design-basis earthquakes. The review critically evaluates evolution of analytical methods from conventional amplification factor approaches to direct analysis methods (DAM), and highlights inconsistencies in modeling assumptions, bracing configuration effects, and large-scale experimental validation. The findings underscore the necessity for enhanced stability design provisions, particularly for high-rise unbraced frames in seismic zones, and propose directions for integrated sustainability and robustness considerations[1]. |
