Sara Y. Kenno

Mechanical Properties of Fiber-Reinforced Concrete Made with Basalt Filament Fibers

AbstractFiber-reinforced concrete (FRC) has become a viable new material used in various constructions such as building pavements, large industrial floors, and runways. In this research, basalt chopped fibers in filament form were used to develop an FRC material called basalt fiber-reinforced concrete (BFRC) to study the possible improvement in the 28-day compressive strength and modulus of rupture, though the latter one is more important for the construction of pavements, industrial floors, and runways. The basalt fiber specimens were cast using basalt filament fibers of three different lengths and three different amounts. Clumping of fibers at high fiber amounts caused mixing and casting problems. These problems become even more severe when long fibers are used at the high fiber dosage amount. The results indicated that 36-mm-long chopped basalt filament fiber and a fiber amount of 8  kg/m3 are optimum for achieving high performance in both the compressive strength and modulus of rupture. This paper dis...

Distributions of residual stresses in stiffened plates with one and two stiffeners

This study was undertaken for a better understanding of the residual stress distributions associated with welds typically found in ship hulls. Specimens that represent small sections of an actual ship hull were built and tested using the neutron diffraction method at the Canadian Neutron Beam Centre in the Chalk River Laboratories. The specimens comprised 9.5 mm thick steel plates stiffened by L127 × 76 × 9.5 steel angles. This paper presents one- and three-dimensional distributions of all three components of residual stress created from the production of the steel plate and from the welding of one and two stiffeners onto the parent steel plate. Subsequently, the longitudinal stress in the transverse direction of the stiffened plate specimens was compared with the Faulkner model. It was found that the Faulkner model is able to predict the general distributions of this stress; however, it was unable to predict the stress values correctly.

Changes in residual stresses caused by an interruption in the weld process of ships and offshore structures

Residual stresses are present in welded stiffened steel plates that are used to construct ships and other offshore structures. These locked-in stresses can exceed the yield stress of the parent plate material. Interruptions due to stop and restart in the welding process in these structures cannot be eliminated completely. It is suspected that weld interruptions are detrimental, though the effect of an interruption on the residual stress distribution is not well understood. Hence, this study was undertaken to determine the change in the residual stresses due to various stop durations in the weld process. The stop time varied from 10 to 60 seconds and the resulting stresses were compared with those observed when the weld is not interrupted. Neutron diffraction was used to determine the residual stresses. The study revealed that, compared to the residual stresses observed for a continuous weld, immediately before the stop location there is a decrease in the resulting residual stresses which is balanced by a concomitant increase immediately following the restart of the weld. The difference between the low and the high stress points in the distribution increased as the stoppage time (duration) increased. This paper presents the specimen design, specimen preparation and construction, test method, and test data obtained for four steel plate specimens.

Residual Stresses in Welded Stiffened Steel Plates—An Experimental Comparative Study

This paper examines the residual stress distributions at selected depths in three stiffened 350WT steel plates representing typical stiffened steel plates used in modern ship construction. Residual stresses can develop from the welding process, and the magnitude of these stresses can be high enough to cause an early onset of yielding. Therefore, fatigue or other failures can also occur when welding-induced residual stresses are combined with service-load-induced stresses. In this study, the welding-induced residual stresses of these stiffened steel plate specimens were quantified at the near surface using the X-Ray diffraction method and at various depths using the neutron diffraction method. Transverse and longitudinal stress components for all three specimens were collected and analyzed. The residual stress profiles determined from both methods were found to be similar. However, some disagreement was found within the heat-affected zone of the weld bead. This paper discusses the residual stress distributions found in the three specimens and compares the two methods of measurement.

Strength of Line Pipe With Dent and Crack Defect

Pipeline industry and various research organizations have been undertaking studies to understand how the pressure strength of line pipes reduces as the defects in the line pipes grow. Defect in pipe lines can be in the form of corrosion, dent, wrinkle, gouge, crack, and combinations of these. A large number of studies have been completed in developing methods for determining the pressure strength of line pipes with dent and gouge defects and also in the form of combined dent-gouge defect. Some of these studies were undertaken with the intention of determining the pressure strength of line pipes when a combined dent and crack (dent-crack) defect has formed. However, in these studies no cracks were simulated in the test pipe specimens; instead, a gouge (machined cut or notch) was produced and considered as a crack. Therefore, it is not realistic to call this defect a dent-crack defect; rather, it should be called dent-gouge defect. Hence, the current project is being undertaken at the University of Windsor to study how the dent-crack defect influences the pressure strength of line pipes. In this study, a crack in true sense was introduced in the pipe wall. Two different techniques were used to simulate the crack in the pipe wall. This paper discusses the procedures used in this study to simulate crack and dent. In addition, the test procedure and test data obtained from denting and pressure tests are discussed.Copyright