Seismic design considerations for masonry across South America
The Pacific Ring of Fire runs along the western edge of South America, exposing cities in Chile, Peru, Ecuador, and Colombia to frequent ground shaking. Across the Andean highlands and Chilean coast, unreinforced masonry remains one of the most common building typologies for low-income housing and heritage structures. Engineers must reconcile traditional construction with modern performance objectives, a task that resonates with practitioners monitoring seismic risk elsewhere.
Delegates in São Paulo for the XIII International Conference on Building Materials and Components will find the technical sessions reflect this tension between vernacular practice and advanced engineering. A look through the gallery from previous editions shows the range of wall typologies, test rigs, and damaged buildings featured in past events. For Australian researchers accustomed to the 1989 Newcastle earthquake, the South American experience offers a much larger empirical base of post-event observations.
The sections below explore dominant material choices, code frameworks, and detailing strategies, and where Australian researchers have begun to engage with South American counterparts.
Tectonic setting and masonry typologies
South America's hazard is concentrated along the subduction zone where the Nazca Plate slides beneath the continent. Chile has seen events above magnitude 8 several times in the last sixty years, while Peru and Ecuador have each experienced destructive quakes within the past three decades. The result is a built environment where confined, reinforced, and unreinforced masonry sit side by side, often in the same street.
Confined masonry, where clay brick or concrete block walls are framed by reinforced concrete tie-columns and tie-beams, dominates low-rise construction in Colombia and Peru. Reinforced masonry with vertical and horizontal steel grouted into hollow units is more common in Chile for buildings of three or more storeys. For Australian designers, the comparison is instructive: AS 3700 covers both reinforced and unreinforced masonry, but Australia's modest hazard has limited detailed seismic provisions. Observing Chilean detailing of vertical reinforcement, bond beams, and slab-to-wall connections provides lessons for community buildings in higher hazard parts of Australia, including the Pilbara.
Material behaviour and wall testing
Full-scale wall tests remain the benchmark in South American laboratories for validating reinforcement schemes and calibrating design equations. Researchers in Santiago, Lima, and Bogotá routinely test walls under in-plane shear, out-of-plane pressure, and combined gravity load, generating data sets other regions can rarely match in volume.
A key finding is the importance of mortar joint quality. Walls with poor mortar tend to fail along bed joints in a sliding mode, while stronger mortar shifts failure into the units. This mirrors laboratory work at the University of Adelaide and RMIT, where researchers have tested Australian clay brick and concrete block walls to inform revisions to AS 3700 and the National Construction Code. A further shared theme is recycled aggregates and supplementary cementitious materials in grouted cores, with Brazilian and Chilean groups publishing results on walls incorporating fly ash and silica fume that complement Australian investigations at CSIRO.
Codes, standards and design philosophy
Code development in South America follows a similar trajectory to that of Australia, but the documents are more prescriptive about seismic detailing. Chile's NCh433, Peru's E.070, and Colombia's NSR-10 each prescribe minimum reinforcement ratios, maximum tie-column spacing, and specific requirements for openings in shear walls. Performance-based alternatives exist but are rarely used in housing projects.
AS 3700 focuses on the strength and serviceability of masonry under gravity, wind, and earthquake actions, leaving the broader seismic framework to AS 1170.4. The two-tier structure is elegant but places a heavy burden on the engineer to interpret capacity reduction and regional hazard factors across separate documents. Australian engineers visiting São Paulo will recognise the same navigation challenges. Cross-referencing the two systems highlights opportunities for harmonisation, with Chile's minimum vertical reinforcement rules potentially informing a more explicit Australian position in moderate seismic zones.
Detailing, retrofitting and resilience
Detailing determines whether a well-designed wall survives a major event. South American practice emphasises continuous bond beams at every floor level, well-anchored vertical reinforcement at wall intersections, and careful detailing around window and door openings. Post-earthquake surveys consistently show that buildings following these rules perform significantly better, even when the masonry units are of modest quality.
Retrofitting unreinforced buildings remains a major challenge. In Lima, where thousands of older homes line hillside districts, engineers have trialled steel mesh overlays, carbon fibre strips, and selective replacement of damaged wall panels. Partial interventions targeting ground-floor weaknesses have become common because full retrofit is often too costly. This experience informs discussions about heritage brick buildings in Sydney and Melbourne, where facade retention and adaptive reuse are popular but seismic upgrading is sometimes neglected. A direct Australian parallel is the post-Newcastle program of bond beam installation, with engineers from firms including GHD, Arup, and Aurecon now working on similar projects across New South Wales.
A practical comparison of regional approaches
| Aspect | Chile (NCh433) | Peru (E.070) | Colombia (NSR-10) | Australia (AS 3700, AS 1170.4) |
|---|---|---|---|---|
| Dominant typology | Reinforced and confined masonry | Confined masonry | Confined masonry | Reinforced and unreinforced masonry |
| Seismic hazard level | High | High | Moderate to high | Low to moderate |
| Vertical reinforcement rule | Required in most walls | Required at wall ends and intersections | Required at wall ends and intersections | Specified by AS 1170.4 |
| Wall test requirement | Mandatory for new unit types | Required for new schemes | Required for novel systems | Project-specific validation |
| Retrofit emphasis | Common, documented | Active, subsidised | Common in heritage districts | Limited, project driven |
This is a working reference, not a ranking. It flags where a familiar Australian assumption may not hold in a South American context.
Recommendations for practitioners and researchers
- Present South American comparative work at Australasian Earthquake Engineering Society conferences, where cross-jurisdictional learning is welcomed.
- Adopt the higher of the two minimum vertical reinforcement ratios between AS 3700 and the relevant South American code when designing confined masonry.
- Specify full-scale wall testing for any project using non-standard units, including recycled aggregate blocks used in São Paulo and Santiago.
- Encourage Standards Australia committees reviewing AS 3700 to incorporate lessons from Chilean minimum detailing rules for bond beams.
- Build retrofit cost models that account for partial intervention, following the Peruvian model of targeted ground-floor strengthening.
- Support joint PhD supervision between Australian universities, such as the University of Melbourne, and partners including the Pontifical Catholic University of Chile.
A useful next step is to download the DBMC 2014 proceedings when available and compile a briefing note comparing AS 3700 with the project code.