Infrastructure Resilience to Natural and Manmade Hazards

long-term resiliency of infrastructures to hazards is crucial for public safety and wellbeing of our society. In our research group we devise on cross-disciplinary frameworks to design for and respond to extreme environments while taking into account inherent uncertainties.
Damping and Thermalizing in structural dynamics
Structural damping is one of the most complex systems’ inputs required for the design of engineering structures. It is a crucial element of structural analysis specially in tall buildings that are characterized as flexible and are sensitive to resonant wind effects. We have rationalized damping–the presence of a velocity dependent dissipative term in the equation of motion–as a thermalization process between a structure and an outside bath. The solid foundation of the thermalization models in statistical physics provides new insights into stability and instability for engineering structures. Specifically, since two systems are considered in thermodynamic equilibrium when they have the same temperature, we show in the case of dynamic buckling that a persistent steady-state difference in kinetic temperature between structure and bath is but indicative of the instability of the system. This shows that the kinetic temperature can serve as a structural order parameter to identify and comprehend failure of structures.
Direct shear in beams subjected to impulse
Protecting important structures against blast loading is vital. Most engineering practitioners use either a Single Degree of Freedom (SDOF) approximation of the dynamic response to blast loading or a computationally expensive numerical model. We have proposed a modal approach that provides a more accurate and less conservative estimate of direct shear, the transient dynamic shear response developed within a few milliseconds of pressure wave arrival, than the estimate based on SDOF. The estimates from the proposed closed-form expression agree closely with the results of refined finite element modeling using LS-DYNA. The proposed approach, thus provides an efficient and accurate estimate of the direct shear to be used in structural design.

Sustainable Design and Maintenance: A Path to Low-Impact Civil Infrastructures

To face the challenges such as climate change and spikes in greenhouse gas emissions, it is necessary to built frameworks for design and development of sustainable and resilient structural systems. Our research integrates engineering mechanics, computational modeling, and novel techniques from stochastic analysis and data analytics, to investigate civil infrastructures at both component and network level, and minimize their environmental impact. We develop frameworks that link structural and material scale characteristics to the network scale environmental impact. These methods are crucial for making sustainable design and maintenance decisions.
Pavement vehicle interaction models, component to system level estimate
In our research we develop mechanics-based models that quantify the carbon footprint of road transportation systems, and relate this footprint to the structural and surface characteristics of pavements, traffic and climatic conditions. The total GHG emission can be evaluated by integrating these models with Life Cycle Assessment tools. To devise fully integrated frameworks for sustainable development, the mechanistic models that we develop must be integrated with real world observations via data analytics. To achieve this goal, we use data available to different federal and state agencies such as the data base of Long Term Pavement Performance (LTPP) Program of FHWA and other available data bases.
Damage, fracture and fatigue due to environmental stressors
There is an inverse relation between the durability of structures and their maintenance cost and environmental impact. Durability of civil infrastructures depends on the properties of construction material as well as the design characteristics. One focus of our research is to study the impact of environmental stressors and thermo-chemo-mechanical evolutions across multiple scales on fracture, damage and durability.