Yielding brace system as a next-generation lateral load mechanism for seismic resilient cities

Abstract

India's building stock remains highly vulnerable to seismic hazards, with conventional retrofitting strategies often limited in their applicability under varying earthquake intensities. This study investigates the effectiveness of the Yielding Brace System as a novel lateral load-resisting mechanism for improving the seismic resilience of mid-rise reinforced concrete buildings. A six-storey special moment-resisting frame was analysed in bare and Yielding Brace System (YBS)-integrated configurations using a comprehensive multi-analysis framework, including nonlinear static pushover analysis, nonlinear time history analysis, incremental dynamic analysis, and probabilistic fragility assessment. Results demonstrate that the incorporation of YBS significantly reduces inter-storey drift demands by 30-53% and increases normalized base shear capacity from 0.30 in the bare frame to 0.75 in the YBS frame. Ductility improved from 3.20 to 3.98, while residual drift ratios consistently remained below the FEMA P-58/ASCE 41 threshold of 0.5%. Fragility analysis revealed that the bare frame reached a 50% probability of collapse at 5.1 m/s², whereas the YBS-equipped frame required 15 m/s², highlighting a threefold enhancement in collapse safety margin. By reducing collapse probability and ensuring functional recovery after earthquakes, Yielding Brace System advances resilient infrastructure development and aligns with global sustainability objectives under UN SDG 9 (Infrastructure), SDG 11 (Sustainable Cities), and SDG 13 (Climate Action).

Keywords: Incremental dynamic analysis; Seismic fragility assessment; Yielding brace system.

Fig. 1

Seismic hazard, exposure, and risk indicators for India based on the Global Earthquake Model (GEM) open-source assessment. [adapted from GEM Foundation, India Seismic Risk Profiles, 2023, CC BY-NC-SA 4.0 (https://www.globalquakemodel.org/product/seismic-risk-profiles)]⁶.

Fig. 2

Proposed YBS Details with Dimensions.

Fig. 3

Workflow for Yielding Brace System (YBS) design and Hollow Structural Section (HSS) selection.

Fig. 4

Force-displacement behaviour of the YBS system, with (a) showing experimental results and (b) numerical model outcomes.

Fig. 5

Methodology adopted for generating seismic fragility curves using nonlinear static and dynamic analysis approaches.

Fig. 6

Six-story, plan-symmetric RC frame: (a) plan layout, and (b) elevation with member sizes and adopted YBS configuration.

Fig. 7

Ground motion scaling and compatibility: (a) normalized response spectra of selected records compared with target spectrum, and (b) median spectrum aligned with the fundamental period of the six-story building.

Fig. 8

Comparative maximum drift ratios of six-story bare and YBS-equipped frames showing improved performance and delayed damage progression with YBS incorporation.

Fig. 9

Pushover curves of six-story bare and YBS-equipped frames showing comparative lateral load behavior in terms of normalized base shear ratio (V/W).

Fig. 10

IDA results of six-story RC frames: (a) bare frame and (b) YBS frame, showing drift ratios with IO, LS, and CP limits.

Fig. 11

Storey drift ratio distribution for six-story RC frames: (a) bare frame and (b) frame with 2% YBS.

Fig. 12

Residual drift ratio distribution of the six-story RC building under Northern Calif-03 ground motion (RSN 7) scaled to 4 g.

Fig. 13

Roof acceleration time histories of the six-story RC building: (a) bare frame and (b) frame with 2% YBS, under Northern Calif-03 ground motion (RSN 7) scaled to 4 g.

Fig. 14

Storey-wise hysteresis loops of the six-story RC frame with 2% YBS under Northern Calif-03 ground motion (RSN 7) at 4 g intensity.

Fig. 15

Pushover-based seismic fragility analysis of the selected 6-storey RC frame building: (a) bare frame; (b) frame with 2% YBS.

Fig. 16

Collapse probability versus intensity measure IM = S_a ​(T1​, ζ = 5%) and corresponding fragility functions derived from traditional IDA for the 6-storey RC frame: (a) bare frame; (b) frame with 2% YBS.