Seismic Response of a Tall Building to Recorded and Simulated Ground Motions

Seismological modeling technologies are advancing to the stage of enabling fundamental simulation of earthquake fault ruptures, which offer new opportunities to simulate extreme ground motions for collapse safety assessment and earthquake scenarios for community resilience studies. With the goal toward establishing the reliability of simulated ground motions for performance-based engineering, this paper examines the response of a 20-story concrete moment frame building analyzed by nonlinear dynamic analysis under corresponding sets of recorded and simulated ground motions. The simulated ground motions were obtained through a larger validation study via the Southern California Earthquake Center (SCEC) Broadband Platform (BBP) that simulates magnitude 5.9 to 7.3 earthquakes. Spectral shape and significant duration are considered when selecting ground motions in the development of comparable sets of simulated and recorded ground motions. Structural response is examined at different intensity levels up to collapse, to investigate whether a statistically significant difference exists between the responses to simulated and recorded ground motions. Results indicate that responses to simulated and recorded ground motions are generally similar at intensity levels prior to observation of collapses. Collapse capacities are also in good agreement for this structure. However, when the structure was made more sensitive to effects of ground motion duration, the differences between observed collapse responses increased. Research is ongoing to illuminate reasons for the difference and whether there is a systematic bias in the results that can be traced back to the ground motion simulation techniques

Discontinuous fiber-reinforced composite for dental reconstructions - Studies of the fracture resistance and the mechanical properties of the material used for extensive direct restorations

Earlier developed low aspect ratio dental discontinuous-FRC are micrometer-scale discontinuous-FRCs, which lack sufficient strength and fracture toughness to reinforce structures reinforced with them. The aim of this thesis was to evaluate the fracture resistance, the bonding properties as well as some mechanical properties of newly developed millimeter-scale discontinuous-FRC. Fiber- and matrix related properties were also analyzed. Four studies were designed to evaluate the fracture resistance and the failure mode of anterior restorations reinforced with millimeter-scale discontinuous-FRC, to assess the shear bonding strength between incrementally placed layers of this fibrous composite, to measure the thickness and the effect of the oxygen inhibition layer (OIL) on the interlayer bonding characteristics as well as to determine various physicomechanical properties. In addition, fiber related properties, including fiber volume fraction, fiber length, critical fiber length and fiber diameter, and matrix related properties, fiber orientation were computed. The results of these studies show that the use of millimeter-scale discontinuous-FRC post-core-crown structure was advantageous in terms of both provided reinforcement and failure mode. Furthermore, it was found that OIL presence improves the interlayer connection. The protruding fibers ends at the interface between the fibrous composite layers and the semi-IPN were considered to promote the durable adhesion upon OIL removal. Millimeter-scale fibers substantially improved the fracture toughness owing to the fibers ability to bridge the crack, blunt the crack tip and carry the load, accompanied with the semi-IPN aided plasticity. However, fibers shorter than 0.4 mm most likely behave as reinforcing filler particles instead of reinforcing fibers. Furthermore, fiber orientation was found to be important for impeding the crack progression. These studies suggest that millimeter-scale discontinuous-FRC should accompany the individually FRC post insertion and should fill the pulp chamber and extend coronally as core material, to provide retention and to strengthen the cervical portion of the tooth. Alternatively, it could be used as post-core structure. In both cases homogenous unit is assumed, due to the identical composition of the materials. Upon curing, the OIL should be left on the surface of the composite and should not be contaminated. This could improve the bonding and improve the inherent fracture resistance of the material. This was observed also in the ability of the material to resist the fracture propagation, which approached the toughness value of dentin. These studies indicate that the benefits of using millimeter-scale discontinuous-FRC are especially the improved fracture toughness and resistance to fracture, as well as improved interlayer bonding compared to conventional composites. Moreover, using of millimeter-scale discontinuous-FRC changes the fracture pattern and more reparable fractures were found for this material.Siirretty Doriast

Benchmarking Image Sensors Under Adverse Weather Conditions for Autonomous Driving

Adverse weather conditions are very challenging for autonomous driving because most of the state-of-the-art sensors stop working reliably under these conditions. In order to develop robust sensors and algorithms, tests with current sensors in defined weather conditions are crucial for determining the impact of bad weather for each sensor. This work describes a testing and evaluation methodology that helps to benchmark novel sensor technologies and compare them to state-of-the-art sensors. As an example, gated imaging is compared to standard imaging under foggy conditions. It is shown that gated imaging outperforms state-of-the-art standard passive imaging due to time-synchronized active illumination

A Benchmark for Lidar Sensors in Fog: Is Detection Breaking Down?

Autonomous driving at level five does not only means self-driving in the sunshine. Adverse weather is especially critical because fog, rain, and snow degrade the perception of the environment. In this work, current state of the art light detection and ranging (lidar) sensors are tested in controlled conditions in a fog chamber. We present current problems and disturbance patterns for four different state of the art lidar systems. Moreover, we investigate how tuning internal parameters can improve their performance in bad weather situations. This is of great importance because most state of the art detection algorithms are based on undisturbed lidar data

Thermoforming of Thin-Ply Composite Structures via In-Situ Heating

This thesis investigates thermoforming of thin-ply thermoplastic composites via in-situ heating for in-space manufacturing applications. The proposed composite concept is based on combining conductive carbon nanotube (CNT) films and high-temperature thermoplastic matrix. The CNT film is made of randomly aligned carbon nanotubes, which possesses outstanding electrical, thermal, and mechanical properties. When combined with polymer matrix, it becomes a multifunctional composite structure. The thermoplastic chosen is polyether ether ketone (PEEK), which is a semicrystalline high-performance thermoplastic that has exceptional physical and mechanical properties at high temperatures. The composite structure studied is consists of a layer of CNT film sandwiched between two thin films of PEEK. The CNT acts as an in-situ conductive heater when a voltage difference is applied, and a mechanical reinforcement. The PEEK polymer impregnated with reinforcement fibers and CNT is capable of reforming by repeating the thermoforming process. The focus of this study is on developing and characterizing the manufacturing process suitable for in-space manufacturing, where CNT/PEEK can be treated as a composite prepreg capable of being reformed into different shapes on demand via thermoforming. The thermoforming of thin-ply composite structures is achieved solely via in-situ electrical heating

Conscience in Crisis: The Need for a Better Understanding of Conscience

Thesis advisor: James KeenanThesis advisor: Dominic DoyleThesis (STL) — Boston College, 2022.Submitted to: Boston College. School of Theology and Ministry.Discipline: Sacred Theology