Master of Science / Department of Civil Engineering / Hayder A. Rasheed / The development of column interaction diagrams for unconfined concrete is a standard analysis procedure. However, the need to develop analysis tools for the actual ultimate capacity of columns is evident. Modern codes and standards are introducing the need to perform extreme event analysis. In previous studies, various models were implemented to assess the ultimate confined capacity of columns under concentric axial loads. On the other hand, the effect of confinement in case of the eccentric axial load and the corresponding bending moment are not investigated in such models. So it is demanded to relate the strength and ductility to the degree of confinement utilization in a new model. The more the eccentricity the less the confinement engaged till the effect of the confinement vanishes at pure bending. Accordingly, the ultimate confined strength and the maximum strain range between the fully confined values (at zero eccentricity) and the unconfined values (at infinite eccentricity) depending on the level of eccentricity. Radial loading with constant eccentricity is followed in the nonlinear moment of area concept that considers the finite layer procedure and the secant stiffness approach, to achieve equilibrium points up to failure. Three different comparisons are made to ensure the accuracy of the analysis. The first is to compare the unconfined analysis results with the well-known software (CSI-Section Builder). Secondly, the ultimate capacity of the confined section is compared with experimental data. Finally, the new eccentricity model is compared with the widely used Mander model, which is applicable to concentric columns, to examine the accuracy versus safety.

Master of Science / Department of Civil Engineering / Stefan A. Romanoschi / The primary objective of this research project was to evaluate the shear behavior of three asphalt-to-asphalt mix interfaces. To accomplish this objective, a special attachment and loading mechanism was designed and built to facilitate the measurement of the dynamic shear reaction modulus and shear strength of the asphalt-to-asphalt interfaces when shear and normal forces are acting simultaneously and they are proportional. Two tests were conducted on 4-inch diameter cylindrical samples cored from an asphalt concrete pad where three types of asphalt-to- asphalt interfaces were built. For each interface, four tack-coat quantities were sprayed. On each sample, the Dynamic Shear Reaction Modulus test was conducted first. Then the Shear Strength test was conducted until the sample failed in shear at the interface. The experiments suggest that the shear strength of the interface is affected neither by the interface type nor by the tack-coat application rate. However, the dynamic shear reaction modulus was affected by both interface type and by the tack-coat application rate. The lowest moduli were recorded for the interface between two fine graded asphalt mixes. With very few exceptions, the highest moduli were obtained for the tack-coat application rate recommended by the construction specification.

Master of Science / Department of Civil Engineering / Mustaque A. Hossain / Due to budget constraints, many highway agencies are becoming interested in pavement preservation or rehabilitation rather than reconstruction to ensure pavement is in serviceable condition. Thin whitetopping (TWT) is the process of rehabilitation of distressed asphalt concrete (AC) pavements using a concrete overlay. This study was done to develop a design catalog for existing AC pavements to be overlaid with TWT. The finite element (FE) analysis was performed with SolidWorks, a 3-D FE software program to develop this design catalog. The design considered different TWT thicknesses, existing AC layer thicknesses and modulus, bonding conditions between TWT and existing AC layer, shoulder conditions and temperature differentials. Each model was built as a three-layer pavement system—concrete (TWT), asphalt layer, and subgrade soil. The traffic load was modeled as a constant pressure with a rectangular area applied at the surface and with intensity equal to the tire inflation pressure of 100 psi. The expected lives of TWT overlays were estimated using fatigue equations developed by the Portland Cement Association (PCA). Results obtained from this study show that interface bonding condition is the most important factor affecting the behavior of TWT. With the increase of TWT thickness or existing AC thickness or AC modulus, and addition of paved shoulder, concrete tensile stress decreases. Curling stress increases with the increase of TWT thickness and is not a function of AC properties. A design catalog was developed in terms of service life of the pavement. Unlike unbonded TWT with unpaved shoulder that results in catastrophic loss of rehabilitated pavement life, bonded TWT is expected to last 10 years, assumed in design. Thus, proper bonding must be ensured in order to have extended pavement life.

Master of Science / Department of Civil Engineering / Asadollah Esmaeily / In this research, soil consolidation is explored in a comprehensive analytical and experimental study. The pore pressure development and dissipation for clay at its liquid limit under one-dimensional compression was investigated using the mid-plane pore pressure measurements. In general, the Terzaghi’s theory of consolidation predicted the pore pressure dissipation and the percent consolidation accurately as long as the sample was in a normally loaded state. For a preconsolidated state however, the results obtained by Terzaghi theory are doubtful. Coefficient of consolidation for smaller pressures varied during consolidation, and although the soil was in a fully saturated state for relatively high pressure increments, the pore pressure developed was less than the applied pressure. Then, the effect of different pressure increment ratios on one dimensional consolidation tests has been studied. The secondary compression effects have been founded to increase as the pressure increment ratio is reduced. Consolidation of a clay layer delimited between sheets with small permeability was also investigated in this study. The consolidation theory of compressible soils usually assumes drainage-free boundaries. This change in boundary conditions at the drainage surface necessitates the use of an approximate technique for solution of the governing partial differential equation. In this study, the solution was obtained by using the Galerkin Method and compared with the “free drainage” case. As expected, the consolidation in the case of restricted drainage proceeds at a much lower rate. The compression consolidation behavior of trampled clays in a semi- saturated state was also analyzed in this research program. It is generally known that the type and energy of compaction bring about deviations in the soil structure and hence, in its engineering properties. Therefore, in the experimental phase of this study, soils were prepared by different trampling efforts and also by different compaction methods. Finally, a reasonably realistic theory of soil consolidation has been proposed and the effect of variable permeability and compressibility on the consolidation behavior was investigated followed by a mathematical treatment of the behavior. Subsequently, laboratory consolidation tests with mid-plane pore pressure measurements were conducted on different kinds of clay.

Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / Glass can be beautiful and strong, so why is it not used more often as a structural material? Most often the reasoning is because people fear its perceived fragile and dangerous nature. Although this is the perception, it is far from the reality. Structurally designed glass can even withstand higher loads than steel. The following report will present several advantages of using glass as a structural material. Because understanding the history of glass can foster a greater understanding of where the future of glass is headed, it is discussed early on. After this, the focus is on how to make a mixture of molten liquid into a structural member. The manufacturing process is at the root of the strength of glass, as are the material properties. The composition and properties of glass are addressed before discussing various uses of glass as a structural material. As architects begin to ask for more structural glass in their projects, structural engineers must be prepared to design the systems or to specify performance criteria to a specialty engineer. To aid in design, published guidelines and testing must be utilized and are therefore discussed. In a glass structural system, the glass is not the only aspect that needs an engineer's attention. Connections present a special challenge when designing with structural glass, but several different forms of connections have been successfully demonstrated in construction. To tie all the previous topics together, three examples of structural glass systems are presented. Europe has been using glass as a structural material for years, but the United States has been slow to follow the trend. Glass has been proven to work as a structural material that can create impressive visual impact. With the support of the glass manufacturing industry and the courage of design engineers, the United States could easily start a movement towards building with structural glass.

Master of Science / Department of Civil Engineering / Mustaque A. Hossain / Pavement preservation by adopting low-cost maintenance techniques is increasing among transportation agencies day by day. Chip seal, also known as seal coat, is widely used as a low-cost, thin surface treatment in preventive maintenance of asphalt pavements in many states, including Kansas. Loosening of aggregate particles from chip-sealed pavement and associated windshield damage to vehicles is a common problem. Thus the Kansas Department of Transportation (KDOT) uses lightweight aggregates as cover materials for chip seals. Although this has decreased windshield damage problems extensive chip loss on seal-coated pavements in the state has been reported. In this study, lightweight aggregates along with polymer-modified asphalt emulsion were used to determine proper aggregate and emulsion application rates to minimize chip loss in chip seals. Again, lightweight aggregates were studied in the laboratory to determine the effect of moisture content and electrical charge on chip loss. Evaluation of chip seal was performed by statistical analysis based on rutting potential, chip embedment, and retention. Results show that aggregate retention and embedment depth depend on aggregate-emulsion interaction, whereas rutting depends on the type of aggregate. Proper selection of aggregate and asphalt emulsion is important to maximize aggregate retention in chip seal. Chip loss also results from a lack of compatibility between the aggregate and asphalt emulsion. Results indicate that retention of aggregate depends on the prevailing charges of aggregate and emulsion particles. Moisture condition of the aggregate does not have any effect on chip loss. A new sweep test machine has been developed to assess chip loss, and it was found to be better than the sweep test currently recommended by the American Society for Testing and Materials (ASTM).

Doctor of Philosophy / Department of Civil Engineering / Asadollah Esmaeily / Civil structures are susceptible to damages over their service lives due to aging, environmental loading, fatigue and excessive response. Such deterioration significantly affects the performance and safety of structure. Therefore, it is necessary to monitor the structural performance, detect and assess damages at the earliest possible stage in order to reduce the life-cycle cost of structure and improve its reliability. Over the last two decades, extensive research has been conducted on structural health monitoring and damage detection. In this study, a signal-based pattern-recognition method was applied to detect structural damages with a single or limited number of input/output signals. This method is based on the extraction of sensitive features of the structural response under a known excitation that present a unique pattern for any particular damage scenario. Frequency-based features and time-frequency-based features of the acceleration response were extracted from the measured vibration signals by Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) to form one-dimensional or two-dimensional patterns, respectively. Three pattern recognition algorithms were investigated when performing pattern-matching: (1) correlation, (2) least square distance, and (3) Cosh spectral distance. To demonstrate the validity and accuracy of the method, numerical and experimental studies were conducted on a simple small-scale three-story steel building. In addition, the efficiency of the features extracted by Wavelet Packet Transform (WPT) was examined in the experimental study. The results show that the features of the signal for different damage scenarios can be uniquely identified by these transformations. Suitable correlation algorithm can then be used to identify the most probable damage scenario. The proposed method is suitable for structural health monitoring, especially for the online monitoring applications. Meanwhile, the choice of wavelet function affects the resolution of the detection process and is discussed in the “experimental study part” of this report.

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / The concept of prestressed concrete appeared in 1888 when P.H. Jackson was granted the first patent in the United States for prestressed concrete design. Jackson’s idea was perfect, but the technology of high strength steel that exhibited low relaxation characteristics was not yet available. It was not until Eugene Freyssinet defined the need for these materials that prestressed concrete could be used as a structural building material. Unfortunately, although Freyssinet, a brilliant structural designer and bridge builder, lacked the teaching qualities necessary to communicate his ideas to other engineers. It would take Gustave Magnel to write the first book of design in prestressed concrete, communicating this idea to designers worldwide. Magnel designed and built the legendary Walnut Lane Bridge in Philadelphia, which revolutionized prestressed concrete in America. Simultaneously, Urlich Finsterwalder, the German bridge builder and designer, was revolutionizing the construction means and methods for prestressed concrete bridges. For example, Finsterwalder invented the free-cantilever construction method of prestressed concrete bridges, which allowed long span bridges to be constructed without stabilized shoring. He then designed stress-ribbon bridges, which would eventually allow prestressed concrete to span distances only steel suspension bridges could achieve. However, it wasn’t until Paul Abeles and his peer, H. von Emperger studied and tested prestressed concrete that the idea of “partial prestressing” emerged. Initially, Freyssinet and Magnel were adamant that prestressed concrete should not be allowed to exhibit any tensile forces at sustained loading. Later, the Roebling family developed the first stress--relieved wire followed by the first stress-- relieved strand. T.Y. Lin once again brought prestressed concrete back into the spotlight when he organized the First Prestressed Concrete World Conference in 1957. Shortly after this conference, Lin published a technical paper in the Prestressed Concrete Institute (PCI) Journal that introduced a new Load Balancing technique which allowed most structural engineers to design prestressed concrete very easily.

Master of Science / Department of Architectural Engineering and Construction Science / Sutton F. Stephens / Cold-formed steel studs, though they are a relatively new building material, have become a mainstay in modern construction. They are favored over traditional lumber studs for their high strength to weight ratio and resistance to insects and rot. Due to their relative newness as a material, new advances in their design and implementation are being developed quite rapidly. One such advancement is flange embossing, a technique used to increase the strength of the connection of screws into the studs. Currently, embossed flanges are not specifically addressed in the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI S100), thereby preventing current design equations from being used to calculate an embossed stud's member properties. An experimental investigation was undertaken to determine what effect, if any, flange embossing has on the nominal flexural strength of cold-formed steel studs as determined using the provisions of AISI S100-07. Studs with embossed flanges were tested in bending and their actual flexural strength was computed. This data was then compared with the nominal flexural strength determined using the AISI Specification, without embossing, to determine if these equations would still be appropriate for the design of embossed studs.

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / This report is designed to be a valuable tool for any engineer who has had proper instruction in load paths and knowledge of structural steel design but is not familiar with truss systems and has never designed a long-span steel truss. In other words, for someone who knows the math and concepts but not the means, methods, and practical limitations of truss design. By applying their knowledge of engineering concepts and some good judgment with the information in this report they will be able to design an efficient truss. The type of truss considered has a span of 100’ to 200’, is parallel chord, one-way, simply spanned, and constructed of steel. The trusses are evaluated for typically gravity loading and analyzed in two dimensions. Aspects from analysis, layout, fabrication, erection, and transportation are investigated to find ideal methods of design and practical limitations for this type of truss. Once this information is learned it can be to be applied to an individual truss on an individual basis. Engineers need to realize that even though a truss could be designed with the most efficient use of steel it may not be the most economic solution. One must also realize too many variables are present to form rules or equations to always yield the perfect truss. Only by coupling proper design and analysis with knowledge of fabrication and erection will one be able to design an efficient truss.