Structural analysis (Engineering)

Flexible thermoplastic p1pes under field and laboratory loading conditions have been
examined in the present study. The flexible pipes were tested under truck loading
application with shallow soil cover. The pipe-soil system response includes soil stresses
around and above the buried pipes, vertical pipe crown diametral strain, and
circumferential pipe wall strains. Modeling the pipe-soil system is made using plane
strain and thin ring assumptions. A thin ring model using Castigliano's theorem is
developed to analyze the behavior and response of a flexible pipe under well defined
loading conditions and simulate the behavior of the buried pipe under the live load
application. Laboratory work was carried out to study the pipe behavior and response
under two-point, three-point, and four-point loading configurations. The thin ring model
predictions show good agreement with classical solutions specially valid for two-point
and three-point loading configurations. Laboratory results were also in good agreement with the predictions. Laboratory results show that the maximum tensile strain for the
four-point loading test occurs at inner pipe crown region. Comprehensive efforts were
made to correlate the thin ring model predictions with the field test results; however, it
appears that the thin ring model cannot be used to simulate the effect of the live load
application. A major source of the differences between the predicted and measured
values is attributed to the applied load magnitude. A further investigation was carried out
to examine the applicability of the model to study the general pipe behavior. The
predicted hoop pipe wall strain profile was found to be similar to that of the reported
strain profile by Rogers under overall poor soil support condition. Comparison of soil
stress distribution shows that the 2D prediction approach provides nonconservative
results while the FE analysis agrees more favorably with the measured pressure data.
Overall, FE analysis shows that a linearly elastic isotropic model for the surrounding soil
and flexible pipes with a fully bonded pipe-soil interface provides a reasonable prediction
for soil pressures close to the buried pipes.

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.

A numerical investigation was conducted to evaluate the geotechnical safety and slope
stability of Municipal Solid Waste (MSW) landfills, considering the effects of
geosynthetic reinforcements, biodegradation of the waste, and associated changes in
material properties, and extreme wind force simulating hurricane conditions. Three
different landfill slopes, 1:1, 1:2, and 1:3 having the height of 122m and width of 2134m,
were analyzed using Limit Equilibrium Method (SLOPE/W) and Finite Element
Modeling (ANSYS). Techniques developed in this study were used to analyze a case
history involving a geogrid reinforced mixed landfill expansion located in Austria. It was
found that few years after construction of the landfill, there is a significant decrease in the
FS due to biodegradation. Extreme wind loading was also found to cause a substantial
loss in the FS. The geosynthetic reinforcement increased the slope stability and
approximately compensated for the damaging effects of biodegradation and wind
loading.

The equivalent end deflections and rotations for beams with integral, but dissimilar, elastic supports were determined. Finite element analysis was used to generate the midsurface deflection of the beam. Numerical results were then fit to the analytical solution for the deflection of a beam, yielding the equivalent end slope resulting from deformations in the support. The lateral deflection at the support was available directly from the finite element calculation. The approach used for modeling of the supports is discussed. It was found that the slope and deflection at the support increase as the relative stiffness of the support decreases, as would be expected. Results are presented for both cantilever and beams with fixed ends, are valid for slender beams with small deflection.

In thick structures, vibrational power can propagate by both in-plane and out-of-plane waves. In performing measurements of power flow or structural intensity, it would be required that the components associated with the in-plane or out-of-plane waves be identified. Using a frequency wavenumber approach, the measured structural intensity can be decomposed into its different wave components. In this thesis, simulated structural intensity measurements are presented to demonstrate the use of this frequency wavenumber technique. The results obtained show the distribution of the structural intensity into the wave components. The implementation of this technique using a laser based instrument is discussed. The required characteristics of the instrument, the number of channels, the spacing between the channels, and the phase accuracy, are described. Also, a table to perform the scanning for the frequency wavenumber analysis is presented.

The dynamic response of plate structures composed of rigidly connected thin plates subjected to point loads is studied. The finite strip method combined with a new approach for analyzing periodic structures is utilized to obtain substantial reduction in computational efforts. Each strip with various boundary conditions is treated as a waveguide capable of transmitting different wave motions. Wave scattering matrices are defined to characterize wave motions at boundaries, intersection of plates and where type of wave guides are changed. The results obtained from the application of the approach on various plate configurations are presented and discussed.

Different methods have been employed to calculate the interlaminar stresses and to study the edge effect in a laminated sandwich specimens under uniaxial tension. However, Finite Element Analysis and Force Balance Method produced stress values which disagreed in both magnitude and sign, a controversy which exists in the case of composite laminates also. Experimental methods, photoelastic coating method and strain gaging, were attempted to obtain the strain distribution on the top surface of a sandwich specimen in three point bending. However, these conventional methods failed to show the sharp strain gradient that exists near the free edge. The Force Balance Method was simplified for sandwich specimens by considering the face laminate as a homogeneous and orthotropic material with averaged properties. Simplified expressions were also obtained for calculating the boundary layer thickness. The boundary layer thickness was found to vary linearly with core thickness for the cases considered.

The objective of this thesis is to report on an experimental study on the compressive behavior of foam cored sandwich composite specimens with and without face/core debond. A test fixture was designed which enables a precisely machined sandwich specimen instrumented with back-to-back strain gages to be loaded in edgewise compression. Tests were conducted on specimens without implanted face/core interface debonds over a range of core densities and gage lengths. The experimentally determined compression strengths and failure modes were compared to closed-form predictions and finite element analysis. Specimens with an implanted through-the-width face/core debond were also tested and mechanism of failure was analyzed using finite element analysis. Good agreement between collapse loads predicted using geometrically nonlinear analysis and experimentally measured strengths was observed.

Flexible plastic and metal pipes are increasingly being used for drainage and storm sewers. When flexible pipes are buried at shallow depths, the pipe behavior will not depend on the dead load pressure above the crown, but rather on the live load pressure (vehicle load). Field tests were designed to evaluate the performance of large diameter flexible pipes of 36 in. (915 mm.) and 48 in. (1050 mm.) under shallow burial depths subjected to the actual vehicle loading. The test pipes included high-density polyethylene (HDPE) pipes, polyvinyl chloride (PVC) pipes, steel pipes and aluminum pipes. AASHTO standard pipe installation procedures were followed and pipes subjected to vehicle loads simulating the effect of HS 20-44 trucks. Measurements of interior pipe-wall strains, soil pressures at different depths and pipe deformations were taken to determine the influence of surface vehicle loads. Results of field tests are compared with those based on theoretical analyses.

Research, tests and analysis are presented on several reinforcements placed in the asphalt overlay of a roadway built over soft organic soils. Non-destructive Evaluation (NDE) methods and statistical analysis were used to characterize the pavement before and after rehabilitative construction. Before reconstruction, falling weight deflectometer, rut and ride tests were conducted to evaluate the existing pavement and determine the statistical variability of critical site characteristics. Twenty-four 500ft. test sections were constructed on the roadway including sixteen reinforced asphalt and eight control sections at two test locations that possessed significantly different subsoil characteristics. NDE tests were repeated after reconstruction to characterize the improvements of the test sections. Test results were employed to quantify the stiffness properties of the pavement based on load-deflection data to evaluate the relative performance of the reinforced sections. Statistical analysis of the data showed the stiffness of the reinforced sections was consistently higher than the control sections.