Study the existing city
Document building configurations, earthquake damage, materials and connections through field surveys, measurements and non-destructive testing in Zagreb.
Project overview
Developing Retrofit Strategies for Historical Masonry Building Aggregates in Zagreb
ZAGGREGATE investigates how neighbouring historic buildings influence one another during earthquakes — and how they can be assessed and retrofitted without shifting risk from one building to the next.
What the project actually does
From earthquake evidence to practical retrofit guidance.
Most assessment methods consider one building at a time. ZAGGREGATE instead studies the full masonry row: buildings of different heights, materials and floor systems that share walls, touch one another and respond together during an earthquake.
Test and model the interactions
Use laboratory experiments, a large-scale shake-table test and calibrated numerical models to understand how damage develops within an individual building and across the row.
Develop safer retrofit strategies
Compare interventions and identify solutions that reduce seismic risk across the aggregate while remaining compatible with Zagreb’s historic architecture.
Field evidenceDamage, geometry and materials
→
ExperimentsComponents and shake-table tests
→
Validated modelsBuildings and complete rows
→
Risk assessmentVulnerability and fragility
→
Retrofit guidanceTools for engineering practice
Core project outcome
Practical guidance for engineers to model, assess and design seismic retrofits for buildings within historical masonry aggregates.
See how the six work packages deliver this outcome →Why one-building assessment is not enough
Connected buildings create a different seismic problem.
Historical urban blocks are heterogeneous systems, not repeated copies of one structural unit. Their seismic safety depends on what happens within each building and across the entire row.
Interaction
Adjacent buildings influence one another during earthquakes.
Irregularity
Heights, floor layouts, materials and openings vary from unit to unit.
Connections
Wall–wall and wall–floor connections are often weak or uncertain.
Failure modes
In-plane and out-of-plane mechanisms may develop simultaneously.
Retrofit effects
Interventions in one building can alter the risk of its neighbours.
The evidence behind the project
The 2020 earthquakes exposed a city-scale challenge.
The Zagreb (ML 5.5) and Petrinja (ML 6.2) earthquakes caused severe damage across Croatia. In Zagreb’s historic centre, many affected buildings are unreinforced masonry units connected in rows and urban blocks.
Post-earthquake inspections showed why the individual-building view is not enough: geometry, floor levels, openings, materials and connections change from one unit to the next, while damage can propagate across the aggregate.
2020Zagreb & Petrinja earthquakes
URMHistoric unreinforced masonry
Block scaleAssessment beyond one building
From city to block
Block 19 as a model for evidence-based investigation.
Spatial damage records and three-dimensional building data connect observed earthquake performance with typology, position in the row and interaction between adjacent structures.
Project objectives
Science that leads to safer engineering decisions.
ZAGGREGATE links fundamental research with practical outcomes for engineers, authorities and custodians of historic urban fabric.
Understand and predict aggregate behaviour.
- Understand the seismic behaviour of masonry aggregates
- Develop and validate aggregate-level numerical models
- Quantify vulnerability and fragility
- Identify governing damage mechanisms and retrofit effects
- Establish an evidence-based retrofit framework
Turn evidence into usable retrofit guidance.
- Provide validated aggregate-level retrofit strategies
- Reduce seismic risk beyond isolated buildings
- Deliver practical engineering tools
- Support decisions with experiments and verified models
- Ensure heritage-compatible interventions
From science to engineering practice
Research designed to become usable guidance.
Validated models and tools
Methods that represent aggregate-level behaviour and can be tested against evidence.
Seismic risk and vulnerability
Quantified performance of historical masonry rows and their constituent units.
Heritage-compatible retrofit strategies
Interventions that improve safety while respecting historic fabric.
Open knowledge transfer
Datasets, publications, workshops and practical recommendations.
Continue exploringSee the research programme →