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As we all know that Taiwan is an island surrounded by oceans. Around the island are many international commercial harbors, domestic fishery harbors and harbors for industrial purposes. However, these harbors are facing safety challenges from the strong wind induced waves during monsoon seasons and typhoon due to tropical depressions. The material degradation, fatigue induced from vibrations and the forced deformation of the whole structural system can not usually be observed until serious damages are realized. It is too late to do the fixing job or to replace the damaged components for the harbor while spending multi-million dollars on rebuilding the damaged facilities is the left choice. If we may find the gradual damages of the harbor in advance and establish a procedure to do the minor fixing or correcting works then during the hash environmental situations the serious damages may be prevented and lots of money can be saved also. There are many ways to do a routine inspection on the structures. However, for the structures in the harbor usually it is not quite easy to do this due to the fact that most structures are under the water. Therefore how to find the efficient and economic methods to investigate the harbor damages corresponding to various material constructions and based on the examination results to establish an alert system and to grade the damage-state will be important. The investigation methods may generally be divided into a general method and method of more detailed. The general methods usually need more experiences but less equipment. However, for the more detailed examination, more advanced equipment and scheme are required. After the inspection how to coordinate the raw data and find the relationship between the data and the damage-state of the structure will be one of the tasks. It is the purpose of this project to find efficient means for the inspection and set up a standard procedure to inspect the harbor structures routinely. In terms of the method, timing, schedule, frequency and appropriateness the evaluation standard for the structural damage is suggested and based on the evaluated results the damage grade is defined quantitatively for the harbor structures. Thus the harbor bureau may effectively manage the harbor structure and maintain the operational safety for the harbor.

Cave (Petrochelidon fulva) and cliff swallows (Petrochelidon pyrrhonota) were collected along the Rio Grande and evaluated as potential indicators of environmental contamination. The Rio Grande receives toxic substances from agricultural, industrial, municipal, and non-point sources; consequently, high levels of contaminants have been detected in birds, mammals, fishes and sediments. Swallows were obtained from 8 sites between Brownsville and El Paso, as well as from a reference site in Burleson County, 320 miles north of the nearest site of the Rio Grande. Blood samples were analyzed by flow cytometry, a technique that allows the detection of DNA damage in blood and other tissues. Plasma samples were analyzed for thyroid hormones using a radioimmunoassay technique. Organochlorines and trace metal analysis was limited to a few samples. DDE and PCB levels were below levels known to cause reduced hatching, embryo mortality, and deformities, Hg, Pb, and As were below detection, and Se, Ni and Cr concentrations were lower than levels known to cause harm in birds. Neither species showed sex-related differences in chromosome damage. Cave swallows from the Del Rio area had the highest levels of DNA variation, which may be indicative of DNA damage, possibly from PAHs exposure. Previous studies indicate that sediment samples from tributaries near Del Rio have high levels of chromium compared to other sites along the Rio Grande. A significant increase in DNA variation between sampling years was detected in cave swallows from Llano Grande Lake. Wildlife samples collected from Llano Grande Lake have recorded high levels of DDE and PCBs; in addition, this urban/agricultural contaminant sink appears to be affected by PAH exposure. T3 levels were below the detection limit of the radioimmunoassay. There were no gender related differences in T4 levels in cave swallows. Cave swallows sampled from Laredo had significantly higher T4 levels than those from birds at other sites during 1999. It was not possible to determine thyroid hormone disruption in plasma samples. Thyroid hormone and flow cytometry data were useful in establishing baseline data. Areas of concern based on genotoxic data include Llano Grande Lake, Del Rio, and El Paso.

Asphalt pavements experience damage due to traffic loading under various environmental conditions. Damage can be caused by viscopl microcracks, fracture due to fatigue cracking, or fracture due to thermal cracking. Asphalt pavements have the capability to remedi s damage depending on binder surface and rheological properties, filler surface properties, and length of rest periods. Asphalt mastic (asphalt and fine aggregates) properties play an important role in controlling damage and healing. This dissertation development of a comprehensive methodology to characterize damage and healing in asphalt mastics and mixtures. The methodology reli ctive imaging techniques (X-ray CT), principles of continuum damage mechanics, and principles of micromechanics. The X-ray CT yield meter that quantifies the percentage of cracks and air voids in a specimen. The continuum damage model parameters are derived from p between applied stress and pseudo strain. The micromechanics model relates the damaged mastic modulus to a reference undamaged mo ationship is a function of internal structure properties (void size, film thickness, and percentage of voids), binder modulus, aggr and bond energy between binder and aggregates. The internal structure parameters are all obtained using X-ray CT and correlated. The developed methodology was used to characterize damage in asphalt mastic and mixture specimens tested using the Dynamic Mechanic A) and dynamic creep test. The damage parameter measured using X-ray CT correlated very well with the predictions of the continuum ics models. All damage parameters were able to reflect the accumulation of damage under cyclic loading and were also able to captur of moisture conditioning on damage. Although this dissertation focused on fatigue cracking at room temperatures, the methodology d used to assess damage due to different mechanisms such as permanent deformation and low temperature cracking.

Hot mix asphalt (HMA) is a granular composite material stabilized by the presence of asphalt binder. The behavior of HMA is highly influenced by the microstructure distribution in terms of the different particle sizes present in the mix, the directional distribution of particles, the distribution of voids, and the nucleation and propagation of cracks. Conventional continuum modeling of HMA lacks the ability to explicitly account for the effect of microstructure distribution features. This study presents the development of elastic and visco-plastic models that account for important aspects of the microstructure distribution in modeling the macroscopic behavior of HMA. In the first part of this study, an approach is developed to introduce a length scale to the elasticity constitutive relationship in order to capture the influence of particle sizes on HMA response. The model is implemented in finite element (FE) analysis and used to analyze the microstructure response and predict the macroscopic properties of HMA. Each point in the microstructure is assigned effective local properties which are calculated using an analytical micromechanical model that captures the influence of percent of particles on the microscopic response of HMA. The moving window technique and autocorrelation function are used to determine the microstructure characteristic length scales that are usedin strain gradient elasticity. A number of asphalt mixes with different aggregate types and size distributions are analyzed in this paper. In the second part of this study, an elasto-visco-plastic continuum model is developed to predict HMA response and performance. The model incorporates a Drucker- Prager yield surface that is modified to capture the influence of stress path direction on the material response. Parameters that reflect the directional distribution of aggregates and damage density in the microstructure are included in the model. The elasto-visco-plastic model is converted into a numerical formulation and is implemented in FE analysis using a user-defined material subroutine (UMAT). A fully implicit algorithm in time-step control is used to enhance the efficiency of the FE analysis. The FE model used in this study simulates experimental data and pavement section.

The presence of moisture in hot mix asphalt (HMA) causes loss of strength and durability of the mix, which is referred to as moisture damage. This study deals with the development of experimental methods for measuring total suction in HMA, which can be defined as the free energy state of water in HMA mixes. The total suction is related to the ability of moisture to get into the mix under unsaturated conditions; it is also related to the ability of the mix to retain moisture. Soil suction has been studied extensively. However, suction in HMA as a porous material and its relationship to moisture damage have not been studied. The development of a procedure to measure the total suction in HMA mixes is the first objective of this research. The second objective is to relate suction measurements to physical and chemical properties of the mixtures. The objectives were achieved in two phases. In the first phase, the total suction was measured in HMA specimens with different types of aggregates (limestone and granite), and with different air void distributions and aggregate gradations. The results of this phase showed that the drying test using a 60 oC temperature-controlled room is the proper setup for measuring the total suction in HMA using thermocouple psychrometers. The characteristics of suction-moisture content curves were found to be related to the air void distribution in HMA. In the second phase, total suction was measured in sand asphalt specimens. These specimens had different combinations of aggregates and binders with different bond energies and exhibited different field performance in terms of resistance to moisture damage. The suction measurements in sand asphalt specimens were used to calculate the moisture diffusion coefficient. The results revealed that water diffused into sand asphalt specimens that are known to have poor resistance to moisture damage faster than those that are known to have good resistance to moisture damage

In polymer matrix composites (PMCs) manufacturing processes can induce de- fects, e.g., voids, fiber misalignment, irregular fiber distribution in the cross-section and broken fibers. The effects of such defects can be beneficial or deleterious de- pending on whether they cause failure suppression or enhancement by localized de- formation processes e.g., crazing, shear yielding and fiber-matrix debonding. In this study, a computational approach is formulated and implemented to develop solu- tions for general boundary-value problems for PMC microstructures that accounts for micromechanics-based constitutive relations including fine scale mechanisms of material failure. The defects considered are voids, and the microstructure is explic- itly represented by a distribution of fibers and voids embedded in a polymer matrix. Fiber is modeled as a linearly elastic material while the polymer matrix is mod- eled as an elastic-viscoplastic material. Two distinct models for the matrix behavior are implemented: (i) Drucker–Prager type Bodner model that accounts for rate and pressure-sensitivity, and (ii) improved macromolecular constitutive model that also accounts for temperature dependence, small-strain softening and large-strain harden- ing. Damage is simulated by the Gearing-Anand craze model as a reference model and by a new micromechanical craze model, developed to account for craze initiation, growth and breakdown. Critical dilatational energy density criterion is utilized to predict fiber-matrix debonding through cavitation induced matrix cracking. An extensive parametric study is conducted in which the roles of void shape, size and distribution relative to fiber in determining damage initiation and evolution are investigated under imposed temperature and strain rate conditions. Results show there are significant effects of voids on microstructural damage as well as on the overall deformational and failure response of composites.

<p>The exploitation of sandwich structures as a means toachieve high specific strength and stiffness is relatively new.Therefore, the knowledge of its damage tolerance is limitedcompared to other structural concepts such as truss bars andmonocoque plate solutions.</p><p>Several aspects of the damage tolerance of sandwichstructures are investigated. The influence of impact velocityonresidual strength is investigated. Sandwich panels withfaces of glass fiber reinforced vinylester are impacted bothwith very high velocity and quasi static. The residual strengthafter impact is found to be similar for both cases of impactvelocity.</p><p>Curved sandwich beams subjected to opening bending momentare studied. Faceñcore debonds of varying size areintroduced between the compressively loaded face sheet and thecore. Finite element analysis in combination with a pointstress criterion is utilized to predict the residual strengthof the beams. It is shown that it is possible to predict thefailure load of the beams with face-core debond.</p><p>Using fractography the governing mode of failure ofcompressively NCF-carbon is characterized. Sandwich panelssubjected to compression after impact are shown to fail byplastic micro buckling.</p><p>The residual compressive strength after impact of sandwichpanels is investigated. Sandwich panels with face sheets ofnon-crimp fabric (NCF) carbon are subjected to different typesof impact damages. Predictions of residual strength are madeusing the Budiansky, Soutis, Fleck (BSF) model. The residualstrength is tested, and the results are compared topredictions. Predictions and tests correlate well, and indicatethat the residual strength is dependent on damage size and notthe size of the damaged panel.</p><p>A study of the properties of a selection of fiberreinforcements commonly used in sandwich panels is conducted.The reinforcements are combined with two types of core materialand three types of matrix. Also the influence of laminatethickness is tested. Each combination materials is tested inuni-axial compression, compressive strength after impact andenergy absorption during quasi static indentation. Thespecimens which are tested for residual strength are eithersubjected to quasi-static or dynamic impact of comparableenergy level. Prediction of the residual strength is made andcorrelates reasonably whith the test results. The tests showthat if weight is taken into account the preferred choice offiber reinforcement is carbon.</p>

<p>The air gap method is a modification of the common way of building indoor walls and floors. The aim of the method is to make a construction, less fragile to water damage, with air gaps where moisture can be removed with a thermally driven air flow, caused by a heating cable. The thesis includes a number of experimental studies of this method.</p><p>Temperature and convective air flow in a vertical air gap was studied and it was noted how air flow increased with raised power of the heating cable. The air flow for one meter of wall varied between 50 m3/day (13 air changes per hour) and 140 m3/day (36 air changes per hour). The lower value was caused by a temperature difference in the range 0.2-0.3 oC. Without heating no air flow was found.</p><p>In studies of moisture and RH in wet “slab on ground” constructions, it was noted how the slab in the room with the air gap method dried to a much higher extent than the slab in the room built in an ordinary way. It was also noted that moisture was transported from the air gap in the floor and up through the air gap in the wall. In the room with the air gap construction, the RH values beneath the floor was at a lower level (and below 75 % RH) than the RH values beneath the floor of conventional construction. Mould does not grow below 75 % RH.</p><p>In the study of a flooded intermediate floor it was noted how the thermally driven convective air flow evidently speeded up drying of the construction. Mould growth was only noted in the case where the heating cables were turned off.</p> / <p>Spaltmetoden är en modifiering av det reguljära sättet av att bygga innerväggar och bjälklag. Syftet med metoden är att skapa en byggnadskonstruktion som är mindre skör med avseende på fuktskador. Detta görs med spalter där fukt kan avlägsnas genom ett termiskt drivet luftflöde som orsakas av en värmekabel. Denna avhandling innehåller ett antal experimentella studier på metoden. Spaltmetoden har studerats med avseende på 1. Samband mellan temperatur och luftflöde, 2. Uttorkning och RF nivåer i golvkonstruktioner samt 3. Översvämning av ett mellanbjälklag</p><p><strong>1. Samband mellan temperatur och luftflöde</strong></p><p>Temperatur och konvektivt luftflöde har studerats i en vertikal spalt och resultatet visar att luftflödet ökar med ökad effekt hos värmekabeln. Luftflödet i en vägg med en meters bredd varierade mellan 50 kubikmeter/dag (13 luftväxlingar per timme) och 140 kubikmeter/dag (36 luftväxlingar per timme). Det lägre flödet orsakades av en temperaturskillnad på 0,2-0,3 oC mellan luftspalt och rum. När värmekabeln var avstängd så registrerades inget luftflöde.</p><p><strong>2. Uttorkning och RF nivåer i golvkonstruktioner ovan betongplatta</strong></p><p>Detta experiment visade att fukt har transporterats från spalten i golvet genom spalten i väggen ut i rumsluften. I spaltkonstruktion var RF inuti golvkonstruktionen lägre (och understeg 75 % RF), jämfört med den konventionella konstruktionen, (mögel växer inte under 75 % RF). Det har också registrerats att betongplattan som hörde till spaltmetoden torkade ut snabbare än betongplattan som var inbyggd i ett gängse rum.</p><p><strong>3. Översvämning av ett mellanbjälklag</strong></p><p>I studien där ett mellanbjälklag blev översvämmat noterades att spaltmetoden förkortade torktiden från 21 dagar till 13 vid den fuktigaste mätpunkten. Mögelväxt noterades endast då värmekabeln hade varit frånslagen.</p><p> </p><p> </p>

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.