Arockiasamy, Madasamy

Artificial reefs are coastal structures built to improve marine life and prevent beach erosion. During earlier days artificial reefs were constructed for recreational fishing using discarded scraps and waste materials. Later on, ships were scuttled for constructing artificial reefs. Artificial reefs dissipate the energy of the wave by making the wave break over the reef. The artificial reefs used for coastal protection are usually in submerged condition as this condition does not affect the aesthetic beauty of the beach. Wave transmission decides the efficiency of submerged-detached artificial reef in protecting the beach from the incoming waves. The efficiency of submerged detached coastal protection structures in protecting the beach is usually measured in terms of wave transmission coefficient.
The experimental investigation in the present study is carried out for submerged two-dimensional impermeable and permeable reefs for three water depths. The crest width of the reefs considered for the experimental studies are 60 cm and 20 cm. The permeable artificial reefs are made up of oyster shells in Nylon bags and biodegradable bags. The water levels considered for the study are 35 cm, 34 cm, and 33 cm. The effect of pore space between the oyster shells, crest width, water depth and wave parameters on the wave transmission coefficient for submerged impermeable and permeable artificial reefs are studied experimentally. The wave transmission coefficient is calculated for submerged impermeable and permeable reefs for different water levels and crest widths. Based on the results of the present experimental studies, it is logical to conclude that both submerged impermeable and permeable artificial reefs contribute to a significant extent to the attenuation of the incident wave.

Pile foundations are subjected to vertical loads and significantly higher lateral loads due to wind, seismic effects, ocean waves and currents, and floating ice sheets. Applied vertical load on a pile is resisted by the skin friction and base resistance. The base resistance is provided by the soil layer and skin friction develops at the soil-pile interface. The lateral load on the pile is resisted by the soil-pile interaction effect, which is dependent on the pile and soil parameters. Published literature shows that a properly designed Pile-to-Pile Cap (PTPC) connection will offer significant lateral resistance to the applied loads. The soil-pile system behavior is highly non-linear which requires a detailed study on the soil-structure interaction considering multi-layered soil strata and their properties.
This Dissertation is divided into two parts: Evaluation of (A) the behavior and performance of PTPC connections, and (B) the load-displacement responses of a pile embedded in a multi-layered non-linear elastic soil strata subjected to static loads. A comprehensive literature review has been performed to study the factors affecting the PTPC connection performances and the load-displacement behavior of piles subjected to static lateral and axial loads considering soil-pile interactions. The objective of the study in Part A is to develop a PTPC connection design capable of producing adequate moment capacity of the pile by relying only on plain pile embedments without any special connection reinforcement details. The present study evaluates the local and global behavior of the PTPC connections with plain pile embedment through Finite Element Analyses (FEA).

This dissertation presents methodologies to develop bridge condition deterioration models which accounts for non-stationarity in the deterioration process with applications to Florida concrete and timber bridges. A critical and comprehensive review of bridge deterioration modeling approaches is presented with illustrative examples based on regression, stochastic Markov-chain, mechanistic and Artificial Neural Network (ANN) models. This study also develops a framework for relating the qualitative National Bridge Inventory (NBI) condition ratings with normalized resistance of the concrete bridge component with application to concrete bridge T-beams to reduce the subjectivity of the NBI condition rating. A systematic approach for the prioritization of bridges for inspection is developed using the multivariate regression modeling technique, and forecasting models are developed based on multiple relevant variables for both concrete bridge superstructure and substructure components.
This dissertation also develops an approach for risk and reliability assessments of concrete and timber bridges based on non-parametric deterioration modeling techniques such as average time-in condition rating (ATICR) and Kaplan-Meier (K-M) survival (reliability) models, for probabilistic prediction of bridge safety while accounting for the partial information from the incomplete bridge condition observations. This study develops relative deterioration rates based on the ATICR and illustrates the time-dependent probability of deterioration of the concrete and timber bridge components based on K-M estimates. Further, the relationship of explanatory variables to the survival time is discussed and estimates are made for the median survival years for reinforced concrete solid slab decks. This dissertation presents the code developed in R for multivariate regression analysis and data-driven reliability analysis. Future research studies in bridge deterioration modeling are also presented.

The present study reviews applications of FRP materials joined by structural adhesives in civil engineering. FE analysis with mix-mode cohesive zone material model (CZM) was used to analyze stresses induced in two structural adhesives joining dissimilar materials (concrete GFRP-CFRP) of the hybrid-composite unit. The predicted failure loads, displacements and deformation by the 3-D non-linear FE analysis in the present study are in good agreement with the experimental results of the hybrid-composite unit reported by Deskovic et al. (1995). The contact analysis revealed a complex 3-D state of stress in the bondlines of both structural adhesives. It is concluded that higher joint strength is expected when a ductile adhesive is used.

Scour is the process of sediment erosion around bridge piers and abutments due to
natural and man-made hydraulic activities. Excessive scour is a critical problem that is
typically handled by enforcing design requirements that make the submerged structures
more resilient. The purpose of this research is to demonstrate the feasibilities of the Optical-
Based Green Laser Scanner and HydroLite Sonar in a laboratory setting to capture the 3D
profile of simulated local scour holes. The Green Laser had successfully reconstructed a
3D point-cloud imaging of scour profiles under both dry and clear water conditions. The
derived scour topography after applying water refraction correction was compared with the
simulated scour hole, and was within 1% of the design dimensions. The elevations at the
top and bottom surfaces of the 6.5-inch scour hole were -46.6 and -53.11 inches from the
reference line at the origin (0,0,0) of the laser scanner. The HydroLite Sonar recorded
hydrographical survey points of the scour’s interior surface. The survey points were then
processed using MATLAB to obtain a 3D mesh triangulation.

The objective of this research is to determine if the deflection equations currently adopted in ACI
440.1r-15 and previously ACI 440.1r-06 accurately reflect the flexural behavior of an overreinforced
Basalt Fiber Reinforced Polymer (BFRP) concrete beam. This was accomplished with
experimental, analytical and numerical models. The experiment consisted of two beams doublyreinforced
with BFRP rebar. A three-point flexural test on beams with a 30 in. clear span was
performed and the deflections were recorded with a dial gauge and LVDT system. This data was
compared to the equations from ACI 440.1r-06, ACI 440.1r-15, Branson’s equation and a
numerical model created in ANSYS Mechanical APDL.
Experimental results show a stiffer beam than expected when compared to the four predictive
models for deflection. This can be due to the level of over-reinforcement and the small clear-span
to depth ratio. Further research should be conducted to determine the cause for the additional
stiffness.

Super-tall buildings located in high velocity wind regions are highly vulnerable to large lateral loads. Designing for these structures must be done with great engineering judgment by structural professionals. Present methods of evaluating these loads are typically by the use of American Society of Civil Engineers 7-10 standard, field measurements or scaled wind tunnel models. With the rise of high performance computing nodes, an emerging method based on the numerical approach of Computational Fluid Dynamics has created an additional layer of analysis and loading prediction alternative to conventional methods. The present document uses turbulence modeling and numerical algorithms by means of Reynolds-averaged Navier-Stokes and Large Eddy Simulation equations applied to a square prismatic prototype structure in which its dynamic properties have also been investigated. With proper modeling of the atmospheric boundary layer flow, these numerical techniques reveal important aerodynamic properties and enhance flow visualization to structural engineers in a virtual environment.

Carbon Fiber Reinforced Plastics has recently has been recognized as an alternative to conventional steel reinforcement in concrete due to its excellent resistance to corrosion. Four rectangular concrete beams and four concrete columns reinforced with CFRP bars were cast for the study of the long term behavior under uniform sustained loading. The beams were simply supported and subjected to uniform sustained loading. The columns were arranged in a steel reaction framework. The beams and columns were instrumented and monitored to observe the change in the behavior due to the creep and shrinkage of concrete. An analytical method is developed to predict the long term behavior of CFRP reinforced concrete members. The calculated deformations compare reasonably with the experimental values. A modified equation for the calculation of the long term deflection is proposed for CFRP reinforced concrete beams. A simplified equation for the calculation of the creep coefficient is also proposed.

Integral abutment bridges provide bridge engineers an economical design alternative to traditional bridges with expansion joints owing to the benefits, arising from elimination of expensive joints installation and reduced maintenance cost. The superstructure for integral abutment bridges is cast integrally with abutments. Time-dependent effects of creep, shrinkage of concrete, relaxation of prestressing steel, temperature gradient, restraints provided by abutment foundation and backfill and statical indeterminacy of the structure introduce time-dependent variations in the redundant forces. An analytical model and numerical procedure to predict instantaneous linear behavior and non-linear time dependent long-term behavior of continuous composite superstructure are developed in which the redundant forces in the integral abutment bridges are derived considering the time-dependent effects. The redistributions of moments due to time-dependent effects have been considered in the analysis. The analysis includes nonlinearity due to cracking of the concrete, as well as the time-dependent deformations. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) models for creep and shrinkage are considered in modeling the time dependent material behavior. The variations in the material property of the cross-section corresponding to the constituent materials are incorporated and age-adjusted effective modulus method with relaxation procedure is followed to include the creep behavior of concrete. The partial restraint provided by the abutment-pile-soil system is modeled using discrete spring stiffness as translational and rotational degrees of freedom. Numerical simulation of the behavior is carried out on continuous composite integral abutment bridges and the deformations and stresses due to time-dependent effects due to typical sustained loads are computed. The results from the analytical model are compared with the published laboratory experimental and field data. The behavior of the laterally loaded piles supporting the integral abutments is evaluated and presented in terms of the lateral deflection, bending moment, shear force and stress along the pile depth.