Circular Economy in High-Seismicity Andean Zones: A Circular Seismic Design Framework for Reusable Steel Moment Connections with Demountable Shear Tabs — Life Cycle Assessment and Normative Adaptation for Peru

Technical Summary: Circular Seismic Design Framework for Demountable Shear Tabs in Peru

Problem Statement
The construction sector accounts for 39% of global greenhouse gas (GHG) emissions, with structural steel manufacturing contributing 8%. In high-seismicity regions like the Andes, conventional permanent steel moment connections are prone to irreversible damage during seismic events. This damage generates approximately 120 kg of steel waste per connection and incurs reconstruction costs equivalent to 30–40% of the original building value. While Circular Economy (CE) principles have been applied in manufacturing and electronics, they remain largely absent from seismic design codes due to the perceived trade-off between demountability (reusability) and seismic safety. Existing research on demountable connections has been limited to low-seismicity contexts, leaving a critical gap in integrating sustainability with seismic performance for Andean regions where ground accelerations routinely exceed 0.4g.

Methodology
This study proposes a Circular Seismic Design (CSD) framework for steel moment connections utilizing Demountable Shear Tabs (DST). The research followed a four-phase IMRyD structure:

1. System Definition: The study modeled 3- and 5-story steel moment-resisting frames (SMRF) designed for a residential building in Lima, Peru (Seismic Zone 4, Soil Type S2). The DST components included A36 steel shear tabs (12 mm), Grade 10.9 high-strength bolts for shear transfer, and Grade 8.8 removable extraction bolts.
2. Seismic Performance Analysis: Twelve numerical models were subjected to nonlinear time-history analysis using SAP2000 v23. The analysis utilized seven Peruvian seismic records (Mw 7.0–8.5; PGA 0.3–0.6g) scaled to the E.030 design spectrum. Performance was evaluated against E.030 limits for Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP).
3. Life Cycle Assessment (LCA): Following ISO 14040:2006 and ISO 14044:2006 standards, a cradle-to-cradle LCA was conducted using OpenLCA v1.10 and the Ecoinvent 3.8 database. Three scenarios were compared: single-use welded, single-use bolted, and DST connections reused three times. Impact categories included Global Warming Potential (GWP), Acidification Potential (AP), and Eutrophication Potential (EP).
4. Normative Adaptation: The study proposed a modification to Article 24 of Peru's E.030 Seismic Design Standard to accommodate demountable connections, specifically introducing a shear resistance reduction factor and defining extraction time limits.

Key Contributions
The study provides four primary contributions to the field:

1. Integrated CSD Methodology: A framework that simultaneously addresses E.030 seismic performance requirements and CE reusability criteria.
2. Full Life Cycle Quantification: An LCA of DST connections across three reuse cycles, quantifying environmental impacts under Peruvian conditions.
3. Seismic Validation: Performance validation using native Peruvian seismic records, demonstrating that demountable connections can withstand high-seismicity loading.
4. Regulatory Pathway: A specific proposal to modify the E.030 standard to legally permit the use of demountable connections in Peru, including technical parameters for shear reduction and residual capacity verification.

Results

• Seismic Performance: All models met the E.030 collapse prevention limit (θ ≤ 0.040). DST connections achieved a maximum interstory drift of 0.028, which is 20% lower than welded permanent connections (0.035). The ultimate moment resistance of DST connections was 505 kN·m (12% higher than welded connections), while shear resistance was 295 kN (7.8% lower than welded but 13.5% above design demand).
• Fatigue and Reusability: Extraction bolts demonstrated a fatigue life of 2,450 cycles, exceeding the 1,000-cycle requirement for seismic design. The mean extraction time was 1.2 hours per connection.
• Environmental Impact: Over three reuse cycles, DST connections reduced Global Warming Potential (GWP) by 62% compared to welded permanent connections (410 kg CO₂ eq vs. 1,080 kg CO₂ eq). Acidification and eutrophication potentials were reduced by 58% and 64%, respectively. The primary reduction driver was the avoidance of new steel production.
• Economic Analysis: For a 5-story building in Lima, the initial cost of DST connections was 15% lower than welded alternatives ($93,600 vs. $110,000). Over a 50-year design life, the Net Present Value (NPV) of the DST option was 22% higher, driven by avoided reconstruction costs and reduced labor time (2.9 hours vs. 4.5 hours for installation).

Significance and Claims
The paper claims that circular economy principles and seismic safety requirements are compatible in high-seismicity Andean environments. It demonstrates that the proposed DST framework not only meets but exceeds current seismic performance limits while significantly reducing environmental impact and long-term economic costs.

The study positions the proposed modification to Article 24 of the E.030 standard—introducing a shear resistance reduction factor (φ = 0.85) for DST connections and mandating residual capacity verification—as a technically grounded and legislatively feasible pathway for regulatory adoption. The authors assert that this framework serves as a replicable model for other high-seismicity Latin American jurisdictions (Chile, Ecuador, Colombia) that currently lack provisions for demountable seismic connections.

The paper acknowledges limitations, noting that the analysis was restricted to buildings up to 5 stories, relied on European supply chain data for LCA (introducing potential uncertainty), and utilized numerical modeling for residual capacity rather than experimental cyclic testing. Future research is recommended to include experimental validation under near-field ground motions and high-rise validation.