Structural Engineering

Professor P. Benson Shing

In spite of recent changes, the seismic design specifications of the California Department of Transportation (Caltrans) on the development of longitudinal column reinforcement in enlarged (Type II) CIDH shafts are still very conservative. For large-diameter bridge columns, #14 and 18 bars are common. With the older specifications that were recently replaced, these large-diameter bars would call for very long development lengths, which could significantly drive up the construction costs.

Professor Hyonny Kim

The largest source of damage to a commercial aircraft is caused by accidental contact with ground service equipment (GSE). The cylindrical bumper typically found on GSE distributes the impact load over a large contact area, possibly spanning multiple internal structural elements, which can lead to widespread damage that is difficult to visually detect, particularly for resilient composite fuselage skin. To better understand internal damage formation versus visual detectability, stiffened composite panels of various size and complexity have been tested at UCSD's Powell Labs.

Professor Gilbert A. Hegemier

The UC San Diego blast simulator characterizes the response of civilian and military components and systems to terrorist explosive attack and high impact scenarios. It identifies threat mitigation and hardening optimization strategies using both retrofit and new construction methods and materials.

The hydraulic/high pressure nitrogen based blast simulator simulates full-scale explosive loads up to 12,000 psi-msec without live explosives and without a fireball permitting structural responses to be seen as they occur.

Professor Michael Todd

Ultrasonic guided wave interrogation using both coherent-phase arrays and sparse arrays (sparsity defined as arrays whose average sensor-to-sensor distance is significantly longer than the interrogating wavelengths) has evolved into a very active research area. This research focuses on the detection, classification, and prognosis of damage using elastic waves as the interrogation mechanism.

The novel approach in this work is the embedding of stochastic models to account for uncertainty of model/physical parameters, in order to derive an optimal detection process that supports predictive modeling with quantified uncertainty.

Professors Falko Kuester and Maurizio Seracini

Leonardo da Vinci's mural, The Battle of Anghiari, has not been seen in nearly 500 years. It was painted in the Palazzo Vecchio's Hall of the 500, and disappeared when the hall was remodeled by Giorgio Vasari starting in 1563. Was Anghiari destroyed? Or did Vasari build a brick wall in front of Leonardo's work before painting his own fresco over it? IGERT-TEECH PI Falko Kuester and co-PI Seracini undertook detailed LIDAR and multispectral scans of the Hall of the 500 to produce a detailed, 3D computer model to aid in the search-and-discovery effort, and graduate students affiliated with the Center of Interdisciplinary Science for Art, Architecture and Archaeology (CISA3) spent extended periods of time in Florence.

Professor David Benson

Traditional finite element methods use low degree, piecewise continuous polynomials to model the geometry of a structure. Modern computer aided design uses non-uniform rational B-splines (NURBS) to represent the geometry of a structure exactly. Isogeometric analysis is an extension of the finite element method that also uses NURBS and related functions. Among the advantages are few equations to solve than traditional finite element methods combined with better accuracy.

Professors Joel. P Conte and John B. Kosmatka

UC San Diego has developed a methodology for predicting and updating the Remaining Fatigue Life (RFL) of monitored aerospace structures and/or structural sub-components. According to this framework, NDE inspection results and Bayesian inference are used to (a) assess the current state of damage of the system and (b) update the probability distribution functions of the damage extents and damage evolution model parameters.

Professor Yu Qiao

Stress wave mitigation in porous materials, such as silica monoliths and PTFE foams, are investigated. As shown in Figure 1, a hat-shaped setup on the SHPB testing system is used to induce force on the porous silica monoliths with different average pore sizes, from a few nanometers to a few hundreds of microns. Under the same shear rate and the same shear displacement, if the pore size is as large as 100 microns, the local softening caused by cell collapse will promote the formation of shear banding along the direction of shear force, and the influence area encircled by orange line will be localized. Whereas if the pore size is small enough like tens of nanometers, local hardening ahead of the shear banding will happen, leading a large influence area and thus more energy will be absorbed by the porous materials.

Professor Robert J. Asaro

The cell wall of S. cerevisae serves to protect the cell from thermal, oxidative and mechanical stresses and it is the target for anti-fungal drugs in pathogenic strains. It also serves as a model for cell wall formation in higher eukaryotes. Little is known about its mechanical properties due to the complex nature of its protein and polysaccharide components, and their interconnections. A multi-scale model describing the cell walls nano-mechanical response to AFM tip indentation and the whole cell's response to high hydrostatic pressure, nano-indentation and micro-manipulation compression experiments is under development.

Professor John B. Kosmatka

Typical Ground Vibration Tests of flight vehicles are performed by attaching a moderate number (10 to 100) of discrete accelerometers to a free-free flight vehicle where the excitation is provided using one or more electro-mechanical shakers. A new approach involves using a noncontacting scanning laser vibrometer on the free-free flight vehicle.

The SLV has the advantage over discrete accelerometers in that a near infinite number of data points can be measured without altering the mass configuration of the flight vehicle. This large number of data points makes it easy to: (a) correlate the experimental data with analytical (finite element) results, (b) investigate local modes, and (c) investigate the affects of subtle vehicle configuration changes on the modal properties.