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Thunderstorm (TS) downburst is a type of extreme wind event that are statistically non-stationary with rapid variation in time. Therefore, they cannot be regarded as the same as the stationary boundary layer wind for the purposes of engineering design. In this research, a framework to evaluate the influence of TS downburst wind load on structures has been established. Firstly, a theoretical model, named the vortex model, is introduced and shown to be capable of simulating the process of six full-scale TS downburst events. These six sets of full-scale TS downburst data were recorded by the Texas Tech University Wind Engineering Research Field Laboratory (WERFL) and the Joint Airport Weather Study (JAWS). The simulations of the vertical distribution of horizontal wind speed are validated with the data from WERFL and JAWS and demonstrate good consistency. Secondly, a combination of the quasi-steady (QS) theory and concepts from the partial turbulence simulation (PTS) method has been applied to estimate the wind load on generic building shapes arising from downburst types of events. Using this approach, the wind-induced pressures arising from an isolated downburst-like flow on the building surface can be estimated by the dynamic pressures of a specific downburst event and a database of pressure coefficients for wind flows with a range of azimuths, elevation angles and turbulence intensities; the latter was measured during the experimental part of this study, using a standard, atmospheric boundary layer wind tunnel (WT). In these experiments, the building models were positioned on a rotational support in uniform flow which was produced by a passive turbulence generator located at different upstream positions to obtain different turbulence intensities. As preliminary validation of the technique, velocity data from the University of Birmingham Transient Wind Simulator (TWS) has been combined with these pressure coefficients to predict the wind pressure time series, which is compared to those measured directly in the TWS. The results demonstrate that the predicted pressure time series have a similar tendency compared with the TWS measurements; and the root-mean-square (RMS) errors of pressure time series between these are less than 50 Pa which is less than one-third of the maximum pressure of TWS. Thirdly, the concept of the design spectrum is adopted subject to thunderstorm downburst. The present investigation builds on previous research to develop wind design spectra (WDS), addressing the potential occurrence of TS downbursts and their effect on structures. This algorithm revisits random vibration theory for assessing the dynamic response of the oscillators that filters input acceleration induced by wind, to then conform design spectra of structures exposed to TS downbursts. A parametric analysis was completed to establish the variability of outflow velocity, structural dimensions, mass, and natural frequency, and their influence on the design spectra, in addition to variations induced by different damping ratios and terrain categories. The outcome of the referred spectral technique is then used to estimate the dynamic performance of a benchmark building. The results are further validated by comparing them with their equivalent calculation based on numerical integration methods, fed with simulated wind time series. The simulated wind field is also applied to the benchmark building whose modelling enhances with finite element software. The superiority of the characteristics of this technique enables the effective and rapid application for the engineering structural design with variable mechanical and aerodynamic properties. According to the built algorithm for the thunderstorm downburst wind design spectra (TWDS), the generalisation of the spectra is carried out through non-linear regression modelling, which can be regarded as an alternative to estimate the dynamic response of structures subjected to transient non-stationary winds. Finally, this research presents a computational method for investigating the ductility demands imposed by transient non-stationary wind loads induced by TS downburst to steel building structures that have been previously damaged during natural hazard events (earthquakes, winds). The new numerical framework enables an inter-phase between the finite element (FE) analysis software ABAQUS and MATLAB reverse optimisation subroutines. A nonlinear static pushover analysis is initially performed to impose the ductility demands due to the primary hazard event. The relationship between the base shear force and lateral roof drift is obtained from the linear elastic range up to a target plastic deformation. The method uses the pushover analysis to bring the structure to any pre-defined ductility level, including the descending branch of the load-deformation curve, thus allowing for a better control on the initially imposed damage. Then, the transient wind loads can be subsequently applied as an externally applied dynamic loading and the new displacement ductility demand can be directly determined. Accordingly, the global plastic deformation mechanism that leads to collapse can be identified. The proposed computational algorithm is applied to a tall steel building structure subjected in its damaged stage to eleven downburst synthetic records. The results demonstrate the non-negligible effects of such wind events on the ductility demands.

There is the diverse range of disciplines studying various topics using x-ray techniques. Now, with the development of third-generation synchrotron sources, we can conduct experiments which require special properties of x-ray beam, such as coherence and polarization for studying materials characterization, structural changes, molecular or spin dynamics and so on. In this thesis, we would present the results of structural and dynamic studies by synchrotron-produced x-ray sources. First, the lipid phase-separated bilayers are studied by resonant soft x-ray scattering. In the novel finding, we find the domains of the so-called liquid ordered phase in the phase-separated mixed lipid-cholesterol multilayers constitute sub-domains which are three-dimensionally ordered. This is one of the few examples of ordered liquid phase within another liquid phase. This offers the possibility for the development of novel materials. We also discuss the utilization of coherent x-ray beams to study the dynamics of nanoparticles in polymer melts and magnetic spins in spin glass systems. The nanoparticles show different diffusive and often novel behaviors depending on the entanglement and the heat treatment. Studying the spin structures of spin glass is always interesting and challenging. Up to now, the detailed observation of spin glass phase transition associated critical behaviors have elucidated experimental studies, such as neutron scattering. Using coherent x-rays, we have been able to couple directly to the critical fluctuations of the so-called Edwards-Anderson (EA) order parameter and have observed the dynamical critical behaviors for the first time.

Fiber reinforced polymer (FRP) deck has some significant advantages compared to concrete deck in use of bridges, such as light self-weight, high stiffness and strength, good durability and easy to install. FRP deck has already been used in some bridge rehabilitation and short span bridges. But for widely used in bridges, FRP deck bridges still need further research. Currently many research efforts focus on the filed tests of FRP deck bridges. Compared to field tests, Finite element analysis also has great advantages, such as low cost and convenient to conduct. Therefore, in this thesis finite element analysis is conducted by ABAQUS on the Boyer Bridge in Pennsylvania. The finite element model is verified by the static field test result. Then a simplified moving truck load is applied on the bridge model in order to analyze the dynamic responses of the FRP deck bridge, including the displacements and stress of each girder at the middle span. The dynamic effect is shown by comparing the dynamic responses and the static responses of the bridge. The connection between the FRP deck and girder is very important to the behavior of the bridge. In this thesis shear studs serve to connect the FRP deck and girder. This thesis also analyzes the effect of shear studs to the dynamic responses of the bridge by changing the number of the shear studs.

The interplay between proteases and protease inhibitors during plant-pathogen interaction represents a common strategy for defense and counter-defense. The plant pathogens Phytophthora infestans and Phytophthora mirabilis secrete effectors such as protease inhibitors that facilitate host colonization through a defense-counterdefense mechanism. The P. infestans serine protease inhibitors EPI1 and EPI10 physically bind and inhibit the tomato serine protease P69B. On the other hand, the P. infestans cysteine protease inhibitor EPIC2B targets PIP1, a papain-like protease that has close similarity to another tomato cysteine protease Rcr3, which is required for the fungal resistance and Avr2 hypersensitivity in Cf-2 tomato. The objective of this research is to characterize these protease inhibitors and their association with specific targets in the host. We studied the structure and activities of these protease inhibitors and their target proteases using recombinant proteins expressed in Escherichia coli and Nicotiana benthamiana. PIP1-His was pulled down using coimmunoprecipitation with anti-FLAG resin from N. benthamiana apoplast by recombinant protein FLAG-EPIC2B, suggesting physical interaction of EPIC2B and PIP1. Similarly, tomato protease Rcr3pim was shown to be a common target for both the Cladosporium fulvum effector Avr2 and P. infestans effector EPIC2B using pull down assays and DCG-04 activity profiling. However, unlike Avr2, EPIC2B is a reversible inhibitor of Rcr3pim and does not trigger hypersensitivity on Cf-2/Rcr3pim tomato. We also found that the rcr3-3 mutant of tomato that carries a premature stop codon in the Rcr3 gene exhibits enhanced susceptibility to P. infestans, suggesting a role for Rcr3pim in basal defense. It appears that relative to C. fulvum, P. infestans evolved a cunning effector that carries virulence activity without triggering plant innate immunity. Like EPIC1, PmEPIC1, an EPIC1 homolog from P. mirabilis, was also found to bind Rcr3pim but not PIP1. Unlike EPIC2B, neither EPIC1 nor PmEPIC1 binds or inhibits PIP1. This work was possible by the ability to express and purify proteins in the apoplast of N. benthamiana. Three tomato proteases with C-terminal 6XHistidine tag were successfully expressed in N. benthamiana apoplast. Our findings suggest that C-terminal His-tagging of proteins in N. benthamiana apoplast is efficient enough to enable purification of functional proteins.