REsearch

The capacity of a thin shell depends on the shape and size of the imperfections present in it. As a result, predicting the buckling capacity of shells is difficult, expensive, and time-consuming, if not impossible, as it requires prior knowledge about the imperfections. Our group is developing a novel procedure for accurately predicting the buckling capacity of thin shells without measuring the underlying imperfections, by probing loaded shells. Computational and experimental implementation of the procedure yields accurate results when the probing is done at the location of the highest imperfection amplitude. Our study highlights the crucial role played by the probing location and demonstrates that predicting the buckling capacity of imperfect cylinders is possible if probing is done at the proper location. 

The presence of imperfections significantly reduces the load-carrying capacity of thin cylindrical shells due to their high sensitivity to such imperfections. To counteract this unfavorable characteristic, the conservative knockdown factor method, developed by NASA in the late 1960s, is utilized in the design of thin cylindrical shells. This approach is widely followed in almost all design codes, either explicitly or implicitly. Our current study is exploring the behavior of wavy cylinders under bending, and our findings indicate that wavy thin cylinders are insensitive to imperfections during inelastic material behavior under bending. Our research also shows that the wave parameters play a critical role in the response of thin wavy cylinders to imperfections during bending. 

The quest for high-fidelity estimates of buckling capacity has regained significant attention due to renewed interest in space-flight and thin, soft materials. The stability landscape, a generic representation of the stability of thin shells, is the key to this renewed interest. Buckling in thin shells can be characterized by the topographical features of the stability landscape. Our studies are focusing on the features of stability landscapes for various types of thin shell structures to develop high-fidelity estimates of their buckling loads.  

Bridges are aging and a large number of them are deemed structurally deficient. Despite this, they still see a significant amount of daily traffic, creating serious safety concerns. The issue of infrastructure safety has become increasingly pressing and urgent. Our goal is to address this challenge by providing precise capacity assessments for deteriorated and structurally deficient bridges. Additionally, we are also investigating the development of a comprehensive protocol for inspecting and assessing aging bridges. 

Traditionally, wind turbine towers are constructed using thin steel cylindrical shells due to their structural efficiency and ease of assembly. However, these thin shells are highly susceptible to imperfections, and even minor imperfections can significantly reduce their capacity. Thus, current design practices for thin cylindrical wind turbine towers are overly conservative, hindering the cost-effectiveness of wind turbines, which have seen increased demand due to their clean energy source. Our group proposes using wavy wind turbine towers, as we have found their sensitivity to imperfections to be much lower compared to circular towers, offering a promising solution for efficient design of taller towers. This has the potential to revolutionize wind turbine tower design.  

The presence of long-period pulses in the near-fault pulse-type ground motions increases the damage potential of such ground motions, particularly for flexible structures like bridges. It is necessary to carry out nonlinear analyses of structural systems for ensuring their safety in the near-source regions.  We developed the technique for the simulation of fling-step motions under the assumption that a fling-step accelerogram can be decomposed into a pulse component and a component without any pulse.  We found through a numerical study that the proposed method of simulation works well provided the amplitude parameter of the pulse is chosen with care.