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Publications

Journal articles, conference papers, reports, and theses, alongside mini-symposia and invited talks. Use the arrow on each publication to explore its background, methodology, and impact.

Journal Articles

2026 Accepted

Quantifying the influence of adversarial knowledge on the robustness of systems under attack

Cao, A. S.; Iannacone, L.
Structural Safety, 102773 DOI
Key contributions: Quantifying the influence of adversarial knowledge on the robustness of systems under attack
Background and motivation
An informed attacker can select vulnerable components, while the defender may be uncertain about the attacker’s knowledge. Physical system properties alone therefore provide an incomplete description of robustness under attack.
Methodology and novelty
An entropy-based formulation combines the attacker’s choice of targets with the defender’s beliefs about the attacker’s knowledge. A value-of-information measure quantifies the resulting change in robustness, extending assessments based on a specified knowledge state.
Impact, significance, and practical relevance
In the illustrative brittle–ductile system, adversarial knowledge matters most for attacks of moderate size, where target selection can determine survival. Physical strengthening and limiting adversarial knowledge therefore address different aspects of the system’s vulnerability.

Code and data

2027 Published online 2026

Probabilistic modelling of buildings as networks

Cao, A. S.; Kumalic, A.; Thöns, S.
Structural Safety, 125, 102783 DOI
Key contributions: Probabilistic modelling of buildings as networks
Background and motivation
Reliable compartments can still form a building that is vulnerable to spreading damage. Segmentation requires quantitative criteria that account for both the structural layout and the probability of failure propagation.
Methodology and novelty
Compartments and their interactions are represented as a probabilistic network. The formulation connects collapse to bond percolation and derives a risk-equivalence criterion for segmentation, with an analytical approximation for regular three-dimensional lattices.
Impact, significance, and practical relevance
In the lattice examples with small spontaneous failure probabilities, improving compartment reliability cannot compensate for insufficient segmentation. The criterion gives a quantitative reference for comparing layouts and measures that contain damage.

Code and data

2026

Dynamic properties of glued laminated timber beams with finger-joints subjected to impact loading

Montalbetti, G.; Cao, A. S.; Frangi, A.
International Journal of Impact Engineering, 214, 105727 DOI
Key contributions: Dynamic properties of glued laminated timber beams with finger-joints subjected to impact loading
Background and motivation
Impact assessments of finger-jointed glued laminated timber require information on both rate-dependent strength and energy dissipation. Static resistance alone does not describe the energy absorbed during failure.
Methodology and novelty
Thirty-six full-scale pendulum tests on finger-jointed spruce beams are combined with published experiments to calibrate a strain-rate-dependent strength model. Separate evaluations of resistance and energy dissipation capture behaviour beyond peak load.
Impact, significance, and practical relevance
The tested beams dissipated five to eight times their elastic strain energy after peak load. An elastic–brittle representation therefore omits a substantial part of the measured energy dissipation, which matters when assessing members intended to absorb impact energy.
2026

On the quantification of robustness and its thresholds

Cao, A. S.; Beck, A. T.
Structural Safety, 120, 102688 DOI
Key contributions: On the quantification of robustness and its thresholds
Background and motivation
A reliable system can remain sensitive to initial damage or abnormal loading. Quantitative robustness assessment also requires thresholds that give the calculated index an interpretable meaning.
Methodology and novelty
An entropy-based index describes coherent systems whose failure depends on the sequence of damage. Derived thresholds distinguish low, medium, and high robustness, with corresponding interpretations for reliability- and risk-based indices.
Impact, significance, and practical relevance
The thresholds turn a calculated index into an interpretable robustness level. Examples involving redundant systems, frames, and networks show why a low failure probability alone does not establish resistance to damage propagation.
2025

Dynamic amplification factors in instantaneously loaded structures

Cao, A. S.; Palma, P.; Frangi, A.
Engineering Structures, 345, 121464 DOI
Key contributions: Dynamic amplification factors in instantaneously loaded structures
Background and motivation
Equivalent static assessments often assume that sudden loading amplifies the response by at most a factor of two. Impact calculations also require a loading pulse that is mechanically compatible with the structural response.
Methodology and novelty
Energy balance and the pseudo-static method establish amplification bounds with and without initial velocity. A compatibility criterion links linear response to triangular pulses and rigid-plastic response to rectangular pulses.
Impact, significance, and practical relevance
Amplification can exceed two without initial velocity and has no universal upper bound under impact. Combining a linear response with a rectangular pulse can underestimate dynamic effects, making both the amplification and pulse assumptions consequential for assessment.
2025

Experimentally validated bending capacity models for strip-reinforced timber beams

Cao, A. S.; Steiger, R.; Frangi, A.
Wood Material Science & Engineering, 20(4), 828–844 DOI
Key contributions: Experimentally validated bending capacity models for strip-reinforced timber beams
Background and motivation
Reinforcement can increase the load-carrying capacity of timber beams and reduce the timber volume required. Whether these material savings also reduce environmental impacts depends on the reinforcement used.
Methodology and novelty
Analytical bending-capacity models are validated against full-size beams reinforced with carbon-fibre strips. Reliability analyses and a cradle-to-gate comparison evaluate timber savings and environmental impacts.
Impact, significance, and practical relevance
At comparable reliability in pure bending, the reinforced designs used 44% less timber than unreinforced beams. However, the carbon-fibre design had a higher cradle-to-gate global warming potential, showing that timber savings alone do not establish an environmental benefit.
2025

Rate-dependency and hysteresis of timber connections with a single laterally-loaded dowel and a slotted-in steel plate

Sroka, K.; Cao, A. S.; Palma, P.; Frangi, A.
Wood Material Science & Engineering, 20(4), 845–865 DOI
Key contributions: Rate-dependency and hysteresis of timber connections with a single laterally-loaded dowel and a slotted-in steel plate
Background and motivation
Timber connections provide much of a structure’s ductility and energy dissipation. Behaviour measured under slow monotonic loading may not represent cyclic loading or impact.
Methodology and novelty
Single-dowel connections in laminated veneer lumber are tested under cyclic loading and monotonic displacement rates from 0.05 to 150 mm/s. Different load-to-grain angles reveal how loading direction interacts with rate-dependent resistance and deformation.
Impact, significance, and practical relevance
Cyclic loading causes pinching and strength and stiffness degradation. Faster monotonic loading increases yield resistance but reduces ductility parallel to the grain, showing why a strength increase cannot be treated as an equivalent gain in deformation capacity.
2024

Impact loading of glued laminated timber beams without finger-joints

Cao, A. S.; Houen, M.; Frangi, A.
Computers & Structures, 296, 107278 DOI
Key contributions: Impact loading of glued laminated timber beams without finger-joints
Background and motivation
Impact data from small clearwood specimens do not directly describe the response of structural-sized engineered timber. Full-scale evidence is needed to represent member failure and debris impact in collapse analyses.
Methodology and novelty
Ninety-five full-scale pendulum tests cover glued laminated timber without finger-joints and laminated veneer lumber. Energy-based equations relate the measured response to peak impact force and dynamic strength increase under different boundary and impact conditions.
Impact, significance, and practical relevance
The experiments identify five failure modes and show that toughness values from small clearwood specimens can overestimate full-size member performance. Impact assessments therefore require evidence at the member scale, with energy absorption distinguished from peak resistance.

Code and data

2024

A pressure-sensitive rheological origin of high friction angles of granular matter observed in NASA–MGM project

Cheng, X. H.; Xiao, S. Z.; Yang, S.; Zhao, N. F.; Cao, A. S.
Chinese Physics B, 33, 068301 DOI
Key contributions: A pressure-sensitive rheological origin of high friction angles of granular matter observed in NASA–MGM project
Background and motivation
NASA–MGM microgravity experiments measured unusually high peak friction angles in sand. Explaining these observations requires accounting for the very low confinement of the tests.
Methodology and novelty
A unified constitutive model couples pressure-sensitive and rate-dependent granular behaviour. Its predictions are compared with the NASA–MGM sand experiments to examine whether a rheological transition explains the unusually high apparent friction angles.
Impact, significance, and practical relevance
The model reproduces the high apparent friction angles through the interaction of low confinement and loading rate. Interpreting the measurements as friction alone would miss the viscous contribution to shear resistance under these conditions.
2024

Modelling progressive collapse of timber buildings

Cao, A. S.; Esser, L.; Frangi, A.
Structures, 62, 106279 DOI
Key contributions: Modelling progressive collapse of timber buildings
Background and motivation
Progressive collapse involves changing structural geometry, member separation, and impacts from falling debris. These processes must be represented to follow damage beyond the initial failure.
Methodology and novelty
A parametric nonlinear dynamic framework integrates member separation, debris tracking, mechanically derived impact loads, connection hysteresis, and incremental damping. Ground-floor column-loss scenarios demonstrate their combined use in a moment-resisting timber frame.
Impact, significance, and practical relevance
The simulations continue beyond initial member failure to follow falling debris and subsequent impacts. This makes it possible to assess how an initial column loss develops into further damage and to compare configurations using the resulting collapse extent.
2023

Catenary action in strip-reinforced wood and timber beams

Cao, A. S.; Grönquist, P.; Frangi, A.
Construction and Building Materials, 385, 131422 DOI
Key contributions: Catenary action in strip-reinforced wood and timber beams
Background and motivation
Catenary action can provide an alternative load path after substantial bending damage. The brittle failure modes of timber limit its ability to develop this mechanism without reinforcement.
Methodology and novelty
Analytical expressions track bending, plastic response, and catenary action while accounting for damage accumulated along the loading path. Tests on reinforced beech specimens validate the formulation, followed by an application to glued laminated timber.
Impact, significance, and practical relevance
Tension-side reinforcement allows an axial load path to remain after bending damage. Because the available catenary resistance depends on prior damage, its contribution to collapse resistance must be assessed through the transition from bending to axial action.

Code and data

2022

Lateral stiffening systems for tall timber buildings – tube-in-tube systems

Binck, C.; Cao, A. S.; Frangi, A.
Wood Material Science & Engineering, 17(4), 309–316 DOI
Key contributions: Lateral stiffening systems for tall timber buildings – tube-in-tube systems
Background and motivation
Tall timber buildings require sufficient lateral stiffness to control wind response while accommodating architectural choices. The stiffness available from timber beam–column joints is a central design consideration.
Methodology and novelty
A braced timber core works together with a semi-rigid perimeter frame. More than 500,000 simulations examine wind response for building heights from 50 to 147 m and different layouts and beam–column joint stiffnesses.
Impact, significance, and practical relevance
The analyses identify feasible configurations and the connection stiffness they require within the investigated range. These requirements connect the choice of a tube-in-tube layout to the joint performance needed to control wind response.
2021

Self-camber of timber beams by swelling hardwood inlays for timber-concrete composite elements

Müller, K.; Grönquist, P.; Cao, A. S.; Frangi, A.
Construction and Building Materials, 308, 125024 DOI
Key contributions: Self-camber of timber beams by swelling hardwood inlays for timber-concrete composite elements
Background and motivation
Casting concrete onto timber elements causes construction-stage deflection in timber–concrete composite floors. Introducing camber before casting can compensate for this deformation.
Methodology and novelty
Oven-dried beech inlays are inserted into transverse cuts in spruce beams. Moisture-induced swelling generates curvature, and a predictive model is validated against an experimental test series.
Impact, significance, and practical relevance
The experiments demonstrate predictable camber without externally applied prestressing forces. Swelling can therefore be used to introduce an upward curvature before concrete casting and compensate for construction-stage deflection.
2021

A unified constitutive model for pressure sensitive shear flow transitions in moderate dense granular materials

Cheng, X. H.; Xiao, S. Z.; Cao, A. S.; Hou, M. Y.
Scientific Reports, 11, 19669 DOI
Key contributions: A unified constitutive model for pressure sensitive shear flow transitions in moderate dense granular materials
Background and motivation
Granular models must describe both the change from quasi-static to flowing behaviour and the evolution from transient to steady flow. Treating these transitions separately leaves their common dependence on pressure and shear conditions unresolved.
Methodology and novelty
A unified constitutive model uses two dimensionless physical variables to couple frictional and viscous behaviour. Predictions are compared with triaxial shear experiments over different pressure and loading conditions.
Impact, significance, and practical relevance
At very low pressure, viscous effects can dominate even during slow shearing. A low shear rate therefore does not by itself justify a purely frictional model, and confinement must be considered when selecting a constitutive description.
2021

A theoretical study of the dynamic response of planar timber frames with semi-rigid moment-resisting connections subjected to wind loads

Cao, A. S.; Stamatopoulos, H.
Engineering Structures, 240, 112367 DOI
Key contributions: A theoretical study of the dynamic response of planar timber frames with semi-rigid moment-resisting connections subjected to wind loads
Background and motivation
Wind-induced acceleration and displacement can govern the serviceability of flexible timber frames. Connection stiffness and mass distribution affect the response and the suitability of simplified prediction methods.
Methodology and novelty
More than one million frame configurations are analysed using gust-factor and dynamic time-domain methods. Regression expressions estimate acceleration, displacement, and fundamental frequency, while additional comparisons examine the effect of mass distribution.
Impact, significance, and practical relevance
The gust-factor approach underestimates acceleration in most investigated cases. The study also demonstrates that changing mass distribution can reduce top-floor acceleration, making both the analysis method and the placement of mass relevant to serviceability design.
2019

A review and analysis of granular shear experiments under low effective stress conditions

Cheng, X. H.; Xiao, S. Z.; Cao, A. S.; Hou, M. Y.
Granular Matter, 21, 104 DOI
Key contributions: A review and analysis of granular shear experiments under low effective stress conditions
Background and motivation
Granular constitutive descriptions are commonly informed by experiments at relatively high confinement. Their transfer to very low effective stress is limited by sparse evidence and changes in shear behaviour.
Methodology and novelty
Experiments under terrestrial gravity and microgravity are examined using limit-equilibrium and rheological models. The analyses address foundation bearing capacity, high peak friction angles, and nonlinear rate-dependent shear response.
Impact, significance, and practical relevance
Low-confinement experiments require both strength-based and rate-dependent interpretations. The combined analysis connects bearing-capacity observations with granular shear behaviour and identifies why high-confinement assumptions can fail when effective stress becomes very small.

Conference Papers

2026

Inconsistency between the load-carrying capacity according to the European yield model and the empirical ultimate slip modulus in EN 1995-1-1

Cao, A. S.; Aquino, C. D.; Branco, J. M.; Palma, P.
INTER 2026, Ås, Norway
Key contributions: Inconsistency between the load-carrying capacity according to the European yield model and the empirical ultimate slip modulus in EN 1995-1-1
Background and motivation
Connection capacity and slip stiffness are often taken from separate design expressions. Combining them assumes that the predicted resistance can be mobilised at the displacement implied by the stiffness.
Methodology and novelty
A beam-on-foundation reference model examines laterally loaded fasteners with different strength definitions. The resulting force–displacement behaviour is compared with the yield-model capacity and empirical stiffness relation.
Impact, significance, and practical relevance
The assumed yield-model resistance can require unrealistically large displacements, while changing a single slip-modulus factor does not restore mechanical consistency. Capacity and stiffness must therefore be derived from a compatible force–displacement description.
2026 Forthcoming

Reliability-based design of glued laminated timber beams subjected to impact loading

Montalbetti, G.; Vuffray, A.; Cao, A. S.; Frangi, A.
INTER 2026, Ås, Norway
Key contributions: Reliability-based design of glued laminated timber beams subjected to impact loading
Background and motivation
Constant strength-increase and load-duration factors do not explicitly represent strain-rate effects during impact. Design must also distinguish maintaining structural integrity from dissipating energy through controlled failure.
Methodology and novelty
Rate-dependent material models are combined with probabilistic resistance and vehicular-impact models. Reliability analyses calibrate partial factors for complementary resistance-based and energy-based design checks.
Impact, significance, and practical relevance
In the calibration, energy-based checks require larger partial factors because energy dissipation is more uncertain than resistance. Impact velocity and bending resistance dominate the uncertainty, identifying the inputs that most strongly influence the vehicular-impact design checks.
2026

Reliability-based capacity design of timber connections comprising glued-in steel plates

Vuffray, A.; Cao, A. S.; Frangi, A.
ESREL 2026, Braga, Portugal DOI
Key contributions: Reliability-based capacity design of timber connections comprising glued-in steel plates
Background and motivation
Glued-in steel plates provide stiff, strong timber connections, but timber pull-out failure is brittle. Ductility requires steel yielding to occur before that failure mode.
Methodology and novelty
System reliability and inverse reliability analysis calibrate the hierarchy of failure modes. Steel-plate dimensions are selected to favour ductile yielding while limiting the reduction in connection capacity.
Impact, significance, and practical relevance
Lower variability in steel properties allows a yielding steel weak link to provide ductility with limited loss of connection capacity in the model. Applying the calibrated hierarchy requires experimental confirmation of the timber-strength and pull-out models.
2026

Low-velocity impacts on steel structures: role of beam-column connection modelling in finite element analyses

De Iasio, A.; Cao, A. S.; Montalbetti, G.; Milani, G.; Ghiassi, B.; Fabbrocino, G.
MOTEMOES 2026, Piacenza, Italy
Key contributions: Low-velocity impacts on steel structures: role of beam-column connection modelling in finite element analyses
Background and motivation
Detailed beam–column joints increase the effort required for impact simulations. The necessary detail depends on whether the assessment concerns overall structural response or local damage.
Methodology and novelty
Finite-element models with different levels of connection detail are compared against full-scale impact experiments. The comparison considers global force and displacement together with local stress and plastic deformation.
Impact, significance, and practical relevance
Simplified joints reproduce global response in the studied impact cases, while detailed joints better resolve local deformation. Global force and displacement agreement therefore does not establish that a model can also predict local joint damage.
2026

Quantifying the robustness of networks using methods from system reliability

Cao, A. S.; Byun, J.-E.; Beck, A. T.
ICONHIC 2026, Chania, Greece
Key contributions: Quantifying the robustness of networks using methods from system reliability
Background and motivation
Threat-dependent network risk assessments provide limited guidance for comparing sensitivity to notional component loss. A probabilistic robustness measure can complement these assessments.
Methodology and novelty
Tensor-based system reliability calculations evaluate the intact network and scenarios in which one edge is lost. An entropy-based index measures the resulting change and compares robustness with quantitative acceptance thresholds.
Impact, significance, and practical relevance
Comparing intact and damaged states identifies edges whose loss has the greatest effect on network performance. This separates the probability of initial failure from its consequences for the network and directs attention to components where damage containment matters most.

Code and data

2026

Non-stationary societal willingness-to-pay and value of a statistical life

Cao, A. S.
ICONHIC 2026, Chania, Greece
Key contributions: Non-stationary societal willingness-to-pay and value of a statistical life
Background and motivation
Life-safety investments can deliver benefits over periods in which income, mortality, and population age distributions change. A stationary valuation can therefore misrepresent the conditions relevant to those benefits.
Methodology and novelty
Societal willingness-to-pay and the value of a statistical life are extended to account for economic growth, changing mortality, and population ageing. Comparisons examine valuations across countries and over time.
Impact, significance, and practical relevance
Economic growth, mortality improvement, and population ageing produce different time-averaged valuations across the country examples. A stationary value can therefore misrepresent the benefits of a long-term safety intervention as the affected population and its economic conditions change.

Code and data

2026

Decision-value analysis of risk mitigation strategies for bridges subjected to climate change

Castro-Giraldo, S.; Friis, T.; Cao, A. S.; Thöns, S.
IABSE Symposium 2026, Copenhagen, Denmark DOI
Key contributions: Decision-value analysis of risk mitigation strategies for bridges subjected to climate change
Background and motivation
The value of a bridge intervention depends on future flood risk and the climate scenario assumed. Choosing an action requires combining these uncertain benefits with intervention costs.
Methodology and novelty
A decision-theoretic formulation values alternative actions using flood-related system reliability, intervention costs, and avoided consequences. Probabilistic forcing exceedances connect climate scenarios to the comparison of expected benefits.
Impact, significance, and practical relevance
The preferred intervention changes across climate scenarios in the bridge example. Evaluating expected benefits across scenarios makes the overall choice explicit and shows why an action preferred under one future climate may not be preferred overall.
2026

Dynamische Vergrösserungsfaktoren für das Szenario Stützenausfall

Cao, A. S.
S-WIN 2026, Zurich, Switzerland
Key contributions: Dynamische Vergrösserungsfaktoren für das Szenario Stützenausfall
Background and motivation
Sudden column loss produces a dynamic response that simplified static checks must represent. A constant amplification factor does not capture changes between bending and catenary resistance.
Methodology and novelty
An energy-based procedure relates a structure’s static resistance curve to its maximum displacement after column loss. The contribution develops a calculation sequence for different structural response types.
Impact, significance, and practical relevance
The calculation derives amplification from the resistance available as displacement increases, including changes between bending and catenary action. It translates the energy balance into a practical column-loss calculation and exposes when a constant factor of two is inadequate.
2025

Modelling Vehicular Impact for Threat-Dependent Progressive Collapse Assessments

Montalbetti, G.; Cao, A. S.; Frangi, A.
ICPS7 2025, Abu Dhabi, UAE DOI
Key contributions: Modelling Vehicular Impact for Threat-Dependent Progressive Collapse Assessments
Background and motivation
A vehicle penetrating a building can damage several columns in succession. An isolated notional column removal does not represent the sequence and timing of that damage.
Methodology and novelty
An energy-based impact model accounts for variable vehicle stiffness and energy dissipation. The remaining vehicle velocity determines the time between successive column losses, linking vehicle penetration to the evolving structural response.
Impact, significance, and practical relevance
The example building withstands isolated column loss but undergoes extensive collapse after successive impacts. Passing a single-column removal check therefore does not establish resistance to a vehicle that penetrates the building and damages several columns.
2025

System effects of timber connections comprising multiple fasteners

Cao, A. S.; Thöns, S.; Jockwer, R.; Palma, P.
ICOSSAR 2025, Los Angeles, USA DOI
Key contributions: System effects of timber connections comprising multiple fasteners
Background and motivation
The capacity of a fastener group depends on load sharing and variability among its components. The displacement needed to mobilise that capacity also depends on the assumed connection stiffness.
Methodology and novelty
Mechanical and probabilistic models examine multiple-fastener connections governed by ductile yielding. The analysis quantifies group capacity, its variability, and the relation between ultimate slip stiffness and mobilised resistance.
Impact, significance, and practical relevance
Adding fasteners reduces capacity variability in the modelled ductile connections. However, the commonly assumed ultimate slip stiffness can be too high and underestimate the displacement needed to mobilise group resistance, limiting its use for predicting connection deformation.
2025

Influence of attacker’s prior knowledge on the performance of redundant systems

Iannacone, L.; Cao, A. S.
ICOSSAR 2025, Los Angeles, USA DOI
Key contributions: Influence of attacker’s prior knowledge on the performance of redundant systems
Background and motivation
Redundancy does not provide the same protection against informed attacks as against uninformed damage. An attacker’s knowledge affects which components are selected and the consequences of their loss.
Methodology and novelty
Probabilistic and combinatorial analyses examine attacks on systems with brittle and ductile components. Reliability and robustness are compared for different attack sizes and levels of prior knowledge.
Impact, significance, and practical relevance
For equal component reliabilities, brittle systems are less robust than ductile systems in the examples. In mixed systems, the most damaging attack often removes both component types, showing why protective measures must consider target combinations as well as individual weaknesses.
2025

Development of a technical specification on numerical design of timber structures – verification and validation of numerical models, analyses, and results

Töpler, J.; Cao, A. S.
CompWood 2025, Vienna, Austria
Key contributions: Development of a technical specification on numerical design of timber structures – verification and validation of numerical models, analyses, and results
Background and motivation
Numerical design requires evidence that a model is implemented correctly and represents the relevant physical behaviour. These are distinct requirements within the development of a timber-design technical specification.
Methodology and novelty
The contribution discusses verification of numerical implementation and convergence alongside validation against physical evidence. Sensitivity and uncertainty are considered when interpreting models, analyses, and results.
Impact, significance, and practical relevance
Agreement with a numerical reference establishes a different claim from agreement with physical experiments. Making that distinction explicit helps define which evidence is required for a particular timber-design application and prevents numerical correctness from being mistaken for physical validity.
2025

Progressive collapse of a timber frame building subjected to single- and multi-column damage scenarios

Cao, A. S.; Frangi, A.
PROTECT 2024, Singapore (proceedings published 2025) DOI
Key contributions: Progressive collapse of a timber frame building subjected to single- and multi-column damage scenarios
Background and motivation
Abnormal hazards can damage multiple columns and produce consequences that extend beyond material loss. A collapse assessment must connect the extent of damage to the societal consequences of fatalities.
Methodology and novelty
Nonlinear simulations assess a five-storey timber frame under single- and multi-column damage. Collapsed area is translated into material losses and life-quality-based societal consequences, with sensitivity analyses of the consequence assumptions.
Impact, significance, and practical relevance
Societal consequences dominate material losses in the studied scenarios, and estimated fatalities strongly influence the total. Evaluating collapse prevention through repair or replacement costs alone would therefore omit the dominant consequence in this case.
2024

Case study of a tall timber building subjected to ground-floor column-loss scenarios

Cao, A. S.; Ullmann, S.; Frangi, A.
10th Forensic Engineering Congress, ASCE, Seattle, USA DOI
Key contributions: Case study of a tall timber building subjected to ground-floor column-loss scenarios
Background and motivation
Knowledge of progressive-collapse resistance in tall timber buildings remains limited compared with steel and concrete construction. Ground-floor column-loss scenarios provide a means of examining alternative load paths.
Methodology and novelty
A ten-storey timber building with a trussed core and dowel-type connections is designed for wind and gravity loading. Nonlinear dynamic analyses then examine its response to selected ground-floor column losses.
Impact, significance, and practical relevance
The ten-storey building resists progressive collapse under the selected ground-floor column losses despite being designed for wind and gravity loads. This demonstrates the available alternative load paths in the case study, with connection behaviour remaining a consequential modelling uncertainty.
2023

Dynamic strength increase of glued laminated timber beams subjected to impact loading

Cao, A. S.; Frangi, A.
INTER 2023, Biel/Bienne, Switzerland DOI
Key contributions: Dynamic strength increase of glued laminated timber beams subjected to impact loading
Background and motivation
Dynamic strength increase can be inferred from force measurements or from the energy released during beam failure. These interpretations differ when post-peak behaviour dissipates substantial energy.
Methodology and novelty
Forty-seven pendulum tests examine spruce beams with and without finger-joints. Dynamic strength increase is inferred separately from reaction forces and energy release, then compared with results from other impact and simulated blast tests.
Impact, significance, and practical relevance
For the finger-jointed beams, the mean factor is 2.1 from reaction forces and 3.0 from energy release. The discrepancy shows that these factors describe different aspects of failure and cannot be interchanged without considering post-peak energy dissipation.
2023

The influence of damping on progressive collapse

Cao, A. S.; Frangi, A.
COMPDYN 2023, Athens, Greece DOI
Key contributions: The influence of damping on progressive collapse
Background and motivation
Progressive collapse changes a structure’s mass, stiffness, and vibration modes. Damping formulations established for an intact structure can therefore produce inappropriate forces as failures accumulate.
Methodology and novelty
Initial and incremental versions of Rayleigh and modal damping are compared in simulations of a collapsing structure. The comparison distinguishes response before and after the first failure.
Impact, significance, and practical relevance
Damping choice has little influence before the first failure but produces large differences in the subsequent collapse. A formulation suitable for checking initial failure can therefore be unsuitable for predicting damage propagation as the structure’s mass, stiffness, and vibration modes change.
2023

Multi-scale hysteretic model of laterally loaded timber connections with dowel-type fasteners

Cao, A. S.; Palma, P.; Frangi, A.
ICEM 20, Porto, Portugal DOI
Key contributions: Multi-scale hysteretic model of laterally loaded timber connections with dowel-type fasteners
Background and motivation
Timber connections often provide the ductility and energy dissipation of a structure. Equivalent viscous damping based on elastic behaviour does not explicitly represent cyclic connection damage.
Methodology and novelty
A semi-analytical model builds connection hysteresis from the behaviour of individual dowel-type fasteners. Cyclic degradation is included explicitly, and fastener responses are assembled for different connection arrangements within a lumped-plasticity model.
Impact, significance, and practical relevance
The formulation ties energy dissipation to connection deformation and damage. This permits inelastic structural analyses to represent cyclic losses mechanically instead of assuming that damping inferred from elastic vibration also describes damaged connections.
2023

A nonlinear dynamic model for collapse investigations in tall timber buildings: preliminary results

Cao, A. S.; Esser, L.; Glarner, B.; Frangi, A.
WCTE 2023, Oslo, Norway DOI
Key contributions: A nonlinear dynamic model for collapse investigations in tall timber buildings: preliminary results
Background and motivation
Assessing timber-building robustness requires models that follow member failure and subsequent impact. The capacity available in individual members does not necessarily remain accessible after connections fail.
Methodology and novelty
A parametric three-dimensional collapse model combines the mixed element method with stress- and energy-based failure criteria. Timber-frame examples examine column-loss scenarios with different member capacities.
Impact, significance, and practical relevance
Connection failures prevent the extra beam capacity from being mobilised in the investigated frames. Increasing member strength alone therefore fails to improve column-loss resistance when the connections interrupt the alternative load path first.
2023

Pendulum impact hammer tests on timber beams: experimental setup

Cao, A. S.; Frangi, A.
WCTE 2023, Oslo, Norway DOI
Key contributions: Pendulum impact hammer tests on timber beams: experimental setup
Background and motivation
Full-scale timber impact testing requires sufficient impact energy and measurements that resolve a rapid failure process. The apparatus and interpretation of its measurements determine which material-response quantities can be recovered.
Methodology and novelty
A 3,475 kg pendulum hammer is instrumented with accelerometers, an angular encoder, and high-speed cameras. The measurement procedure recovers energy release, peak impact force, and failure timing from tests on structural-sized beams.
Impact, significance, and practical relevance
The apparatus connects the rapid failure process to measurable force and energy quantities at member scale. Its documented instrumentation and interpretation allow impact behaviour to be investigated across engineered timber products using a common experimental procedure.
2023

Mixed element method for progressive collapse analysis: method description and verification

Cao, A. S.; Frangi, A.
Eurasian OpenSees Days 2022, Torino, Italy (proceedings published 2023) DOI
Key contributions: Mixed element method for progressive collapse analysis: method description and verification
Background and motivation
Progressive-collapse models must represent discontinuities when members separate after failure. Resolving these discontinuities can be computationally demanding in conventional finite-element formulations.
Methodology and novelty
The mixed element method uses standard finite-element components to represent separation and large movements. Modal, static, and transient responses are verified against reference finite-element models.
Impact, significance, and practical relevance
The verification cases show small deviations from the reference finite-element solutions. Standard element types allow separation and subsequent member motion to be represented within existing software, establishing a numerical foundation for later collapse applications.
2022

Pendulum impact hammer tests on spruce glued laminated timber – preliminary results

Cao, A. S.; Lolli, M.; Frangi, A.
CST 2022, Montpellier, France DOI
Key contributions: Pendulum impact hammer tests on spruce glued laminated timber – preliminary results
Background and motivation
Experimental evidence on impact failure of structural-sized engineered timber is needed for collapse simulations. Results from small wood specimens cannot directly establish that response.
Methodology and novelty
Three full-scale spruce glued laminated timber beams are tested with a pendulum impact hammer. Pendulum motion and high-speed imagery provide estimates of impact force, failure time, and dissipated energy.
Impact, significance, and practical relevance
The three specimens failed in approximately 10–12 ms through combinations of tension and shear cracking. These initial observations establish the timescale and failure mechanisms that member-impact models must resolve, while the small sample limits inference about material variability.
2022

Column removal analyses of timber structures – framework to assess dynamic amplification factors for simplified structural design methods

Cao, A. S.; Palma, P.; Frangi, A.
WCTE 2021 (proceedings published 2022) DOI
Key contributions: Column removal analyses of timber structures – framework to assess dynamic amplification factors for simplified structural design methods
Background and motivation
Sudden column removal produces dynamic effects that quasi-static robustness checks must account for. Timber’s limited plasticity makes the assumed amplification particularly consequential.
Methodology and novelty
A set of 216 nonlinear dynamic analyses examines small planar timber frames after column removal. Variations in connection stiffness and damping quantify their influence on the relationship between static and dynamic response.
Impact, significance, and practical relevance
Amplification factors range from 1.9 to 2.0 in the investigated frames, with connection stiffness and damping having the greatest influence. These results identify the assumptions behind the simplified checks without establishing a universal upper bound for other structural responses.
2021

Theoretical studies of tall timber buildings subjected to service-level wind loads

Cao, A. S.; Stamatopoulos, H.
WCTE 2021 (Online) DOI
Key contributions: Theoretical studies of tall timber buildings subjected to service-level wind loads
Background and motivation
The low mass and flexibility of tall timber buildings make wind-induced vibration a central serviceability concern. Bracing and semi-rigid moment connections offer different ways of controlling this response.
Methodology and novelty
Planar moment-resisting and braced timber frames are analysed under service-level wind loading. Gust-factor and dynamic time-history approaches are compared through their predicted peak accelerations.
Impact, significance, and practical relevance
The braced frames have peak accelerations about 50% lower than the moment-resisting frames in the study. Differences between gust-factor and time-history predictions also vary with building height, showing that structural layout and analysis method both affect the serviceability assessment.

Reports & Theses

2024

Modelling progressive collapse of timber buildings and its applications

Cao, A. S.
Doctoral Thesis, ETH Zurich (Diss. ETH No. 30572) DOI
Key contributions: Modelling progressive collapse of timber buildings and its applications
Background and motivation
Robustness measures developed for conventional structural materials do not directly resolve the behaviour of timber buildings. Decisions about collapse prevention require a connection between failure mechanics and the resulting consequences.
Methodology and novelty
The thesis integrates nonlinear analysis, analytical models, and impact experiments with assessments of fatalities and material losses. Applications compare risk- and damage-based robustness measures and evaluate human-error and malicious-action scenarios for a timber building.
Impact, significance, and practical relevance
Loss of life dominates material losses in the case study, and the risk assessment favours directing most mitigation resources towards reducing human errors. The thesis connects collapse mechanics to the allocation of safety resources under explicitly defined hazards and consequences.
2022

Pendulum impact hammer tests on glued laminated timber beams

Cao, A. S.; Houen, M.; Lolli, M.; Frangi, A.
Report / Institute of Structural Engineering ETH Zurich, Vol. 2022-01 DOI
Key contributions: Pendulum impact hammer tests on glued laminated timber beams
Background and motivation
Impact models for structural-sized timber require experimental records of failure and energy dissipation. Documenting the test conditions is necessary for interpreting and reusing those measurements.
Methodology and novelty
The report records a full-scale pendulum impact test programme on glued laminated timber beams. It documents the experimental arrangement and measured response.
Impact, significance, and practical relevance
Documented test conditions allow the measured failure response and energy dissipation to be interpreted alongside the associated impact studies. The report preserves the experimental evidence needed to examine modelling assumptions and reuse the observations in further analyses.

Mini-symposia

Accepted

Climate uncertainty in engineering design, assessment, and decision-making

Organisers: A. S. Cao; Y. Li; M. Broccardo; N. Meinen; P. G. Morato; O. Tieleman; D. Straub

15th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP15)

Melbourne, Australia Conference listing
Accepted

Climate Change on Infrastructures: Probabilistic Assessment, Standardisation, and Decision Support

Organisers: E. Bastidas-Arteaga; S. Thöns; A. O’Connor; L. Iannacone; A. S. Cao

15th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP15)

Melbourne, Australia Conference listing
Accepted

Uncertainty Quantification, Reliability and Robustness of Interdependent Systems, Systems-of-Systems and Hierarchical Networks

Organisers: A. T. Beck; A. S. Cao; J.-E. Byun; R. Ghanem

7th International Conference on Uncertainty Quantification in Computational Science and Engineering (UNCECOMP 2027)

Crete, Greece Conference listing

Latest advancements on structural and infrastructure robustness

Organisers: L. Iannacone; A. S. Cao; F. Parisi; A. T. Beck

Engineering Mechanics Institute 2026 International Conference (EMI 2026-IC), University of Naples Federico II

Naples, Italy

Invited Talks

From Random Failures to Strategic Attacks: Quantifying Robustness in Complex Systems

Department of Civil and Environmental Engineering, Princeton University

Princeton, NJ, USA

Modelling progressive collapse of timber buildings

SARAH 2025 – International Advanced School on Structural Robustness and Resilient Infrastructure against Extreme Hazards, University of Naples Federico II

Naples, Italy

Aspects of modelling progressive collapse

9th International Course on Seismic Analysis of Structures using OpenSees, EPFL

Lausanne, Switzerland