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Articles 1 - 10 of 10
Full-Text Articles in Civil and Environmental Engineering
A Nonlocal Model For Coupled Damage-Plasticity Incorporating Gradients Of Internal State Variables At Multiscales, Robert J. Dorgan
A Nonlocal Model For Coupled Damage-Plasticity Incorporating Gradients Of Internal State Variables At Multiscales, Robert J. Dorgan
LSU Doctoral Dissertations
The thermodynamically consistent formulation and the subsequent numerical implementation of a gradient enhanced continuum coupled damage-plasticity model as a constitutive framework to model ill-posed localization problems is presented. By the introduction of "nonlocal," gradient-enhanced measures in the plasticity potential function and yield criterion and in the damage potential function and damage criterion, the proposed model introduces microstructural characteristic material length scales which allows the size of localized zones to be predicted based on material constants, as opposed to local models where the loss of ellipticity causes the localized zones to be mesh dependent.
The gradient model proposed introduces non-linear functions …
Theoretical And Experimental Study On Cable Vibration Reduction With A Tmd-Mr Damper, Wenjie Wu
Theoretical And Experimental Study On Cable Vibration Reduction With A Tmd-Mr Damper, Wenjie Wu
LSU Doctoral Dissertations
Stay cables are vulnerable to dynamic excitations because of their low intrinsic damping. Excessive cable vibrations cause frequent maintenance and are detrimental to the safety of the entire bridge. Targeting the severe cable vibration problem, in addition to using the existing Magnetorheological (MR) damper, the current study proposes a new type of damper, called the Tuned Mass Damper-Magnetorheological (TMD-MR) damper. Theoretical and experimental investigations for the damper performance on the cable vibration reduction are conducted, which provides the necessary research support for practical implementation. Experiments on the individual MR damper are carried out first to gain some experience on the …
Use Of Polyhydroxyalkanoates For Denitrification In Recirculating Aquaculture Systems, Maria Teresa Gutierrez-Wing
Use Of Polyhydroxyalkanoates For Denitrification In Recirculating Aquaculture Systems, Maria Teresa Gutierrez-Wing
LSU Doctoral Dissertations
Increasing demand of aquacultural products is driving the industry toward more intensive culture practices. Aquacultural operations are constrained by limitations on the availability high quality waters and regulatory pressures on the discharges. Recirculating systems can address these issues by reducing the amount of water required in the operation. Closed systems are especially suited where biosecurity is important. In closed systems, nitrate accumulates, limiting the time the water can be reused. In marine inland systems, water reuse reduces the cost of salt for make up water. To increase the water reuse time, some form of nitrate removal process must be incorporated …
Spectral Analysis Of Total Suspended Solids Mixtures For Solids Composition Determination, Curtis W. Sutherland
Spectral Analysis Of Total Suspended Solids Mixtures For Solids Composition Determination, Curtis W. Sutherland
LSU Doctoral Dissertations
Total Suspended Solids (TSS) analysis provides an initial and very basic measure for study and characterization of water quality. The present tedious procedures used for the identification of different solids constituents present in TSS and for the classification or insight into the origins of those solids are time-consuming and expensive. The research reported herein investigates the use of instrumental analysis using reflectance spectra of TSS as an attractive alternative to sufficiently characterize and identify TSS in a more rapid and economical method that could be used to study TSS transport and to identity TSS points of origin. For this investigative …
A Stochastic Mesoscopic Cell-Transmission Model For Operational Analysis Of Large-Scale Transportation Networks, Ciprian Danut Alecsandru
A Stochastic Mesoscopic Cell-Transmission Model For Operational Analysis Of Large-Scale Transportation Networks, Ciprian Danut Alecsandru
LSU Doctoral Dissertations
The cell transmission model (CTM), developed by Daganzo in 1994 was not fully exploited as an operations model for analysis of large-scale traffic networks. Because of its macroscopic / mesoscopic features, CTM offers calibration and computational advantages over microscopic models. This study presents a series of enhancements to the original form of CTM. These enhancements show potential to increase the model’s accuracy and realism of traffic flow representation. For example, topological enhancements and modifications to the flow advancing equation are introduced to allow variable cell lengths and non-discrete movements of vehicles between cells. In addition, implementation of lane-changing behavioral logics …
Design And Evaluation Of Automated, Continuous Culture Techniques For Brachionus Rotundiformis, Zhengzhong Zhang
Design And Evaluation Of Automated, Continuous Culture Techniques For Brachionus Rotundiformis, Zhengzhong Zhang
LSU Doctoral Dissertations
A 40-L recirculating rotifer turbidostat (RRT) pilot system consisting of a rotifer reactor, biofilter, foam fractionator, feed container, harvester, and two air-lift pumps was designed to produce B. rotundiformis, a small (S-type) rotifer, that is increasingly demanded for production of small-gape marine finfish larvae. The system’s automatic monitoring (turbidity, pH, conductivity and temperature) and controlling (turbidity, pH, feeding and harvesting) were performed by a Rugid™ computer. A 4 (temperature) x 3 (salinity) study indicated that a 30oC/15 ppt treatment is the most favorable to the growth of B. rotundiformis. Under these conditions, the effect of harvest rate on rotifer system …
Structural Performance Of Approach Slab And Its Effect On Vehicle Induced Bridge Dynamic Response, Xiaomin Shi
Structural Performance Of Approach Slab And Its Effect On Vehicle Induced Bridge Dynamic Response, Xiaomin Shi
LSU Doctoral Dissertations
Differential settlement often occurs between the bridge abutment and the embankment soil. It causes the approach slab to lose its contacts and supports from the soil and the slab will bend in a concave manner. Meanwhile, loads on the slab will also redistribute to the slab ends, which may result in faulting (or "bump") at the slab ends. Once a bump forms, repeating traffic vehicles can deteriorate the expansion joint in turn. In this case, the vehicle receives an initial disturbance before it reaches the bridge. This excitation introduces an extra impact load on the bridge and affects its dynamic …
Development Of A Mix Design Methodology For Asphalt Mixtures With Analytically Formulated Aggregate Structures, Khalid Salim Alshamsi
Development Of A Mix Design Methodology For Asphalt Mixtures With Analytically Formulated Aggregate Structures, Khalid Salim Alshamsi
LSU Doctoral Dissertations
This research documents an extensive study on the design and characterization of asphalt mixtures for use as road pavement material. Several aspects of asphalt mixtures were addressed using the state of the art laboratory test equipment and technical literature from different information sources. The research was divided into two phases. Phase one included the design and detailed analysis of compaction and performance characteristics of asphalt concrete mixtures with aggregate structures that were designed using an analytical method of aggregate blending. Three aggregate types were considered in this study: limestone, sandstone, and granite. All the aggregates were crushed aggregates. Three different …
An Adaptive Multi-Scale Computational Method For Modeling Nonlinear Deformation In Nanoscale Materials, Wenming Wang
An Adaptive Multi-Scale Computational Method For Modeling Nonlinear Deformation In Nanoscale Materials, Wenming Wang
LSU Doctoral Dissertations
In this dissertation a coupled multi-scale computational model for simulating nonlinear deformation processes in crystalline metals at finite temperatures is developed. The computational model uses the finite element method to model the coarse scale response of the material. The constitutive response in the finite element will be modeled through interatomic potentials acting on the underlying homogeneous crystal lattice that characterizes its nanostructure. An adaptive remeshing technique is proposed to automatically delineate regions of severe deformation where homogeneity of the microstructure/deformation is violated. In these regions the finite element will be replaced by a set of deformed atoms which interact with …
A Plasticity-Damage Model For Plain Concrete, Umit Cicekli
A Plasticity-Damage Model For Plain Concrete, Umit Cicekli
LSU Doctoral Dissertations
A plastic-damage model for plain concrete is developed in this work. The model uses two different yield criteria: one for plasticity and one for damage. In order to account both for compression and tension loadings, the damage criterion is divided into two parts: one for compression and a second for tension. The superscripts (+) and (-) in this work are used to represent tension and compression cases, respectively. The total stress is decomposed into tension and compressions components. The total strain is decomposed into elastic and plastic parts. The strain equivalence concept is used such that the strains in the …