Search

The current method for estimating parallel-to-grain dowel bearing strength of cross-laminated timber (CLT) fasteners applied perpendicular to the face in the US adjusts the length of the fastener to account for the effect of cross-layers rather than modifying the dowel bearing strength. This method is counter to more-commonly used methods in Canada and Europe which adjust the dowel bearing strength of the CLT material and using the original length of the dowel. Currently, there are no experimental data supporting the use of an adjusted fastener length. This paper presented an alternative method for CLT dowel bearing strength assessment according to the US design code. The proposed method produced similar or slightly conservative dowel bearing strength values compared with the current US design method. Experimental results of dowel bearing strength were compared against the current design code, the proposed method, and European and Canadian codes. Standard test procedures were used to evaluate, stiffness, yield strength, 5% offset yield strength and ultimate strength. Greater mechanical properties were found for CLTs containing more parallel-to-grain layers, whereas lower mechanical properties were found for CLTs containing more perpendicular-to-grain layers. The current US dowel bearing strength method, the proposed method, and the European design code produced similar results, which were slightly conservative compared with the experimental values. The proposed dowel bearing strength equation is felt to be an improvement given the ease of use and similarity in form to other design formats. [ABSTRACT FROM AUTHOR]

Joint sealants are used widely in Canada to protect pavements from infiltration of water and incompressible materials. Sealants are typically selected based on field studies, which are commonly repeated on a 10-year cycle. This paper examines a laboratory evaluation method based on two laboratory tests that are commonly used for testing asphalt binders: dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Creep stiffness, rate of change in creep stiffness, and rate of change in complex shear modulus with temperature were used to evaluate sealant performance in cold climates. A sealant ranking system was proposed based on the calculation of a sealant index, which combines the proposed evaluation criteria. This method can potentially provide a cost-effective and rapid alternative to field studies. Eight hot-pour sealants were evaluated using this method. Results were verified from an ongoing field study that started in 2004. A good correlation was found between the proposed simplified evaluation method and the existing method. [ABSTRACT FROM AUTHOR]

Low-temperature cracking is a significant distress in asphalt pavements built in the northern United States and Canada. As temperature decreases, thermal stresses develop in the restrained asphalt surface layer; and when the temperature reaches a critical temperature, cracking occurs. The current guides use thermal stress as a critical input parameter in the low-temperature performance model. In this paper, statistical and graphical analyses are performed to compare thermal stresses that develop in an idealized asphalt pavement calculated from mixture creep data obtained using indirect tensile test (IDT) and bending beam rheometer (BBR) test. In addition, the idea of obtaining thermal stresses from binder BBR creep data is further investigated. Thermal stresses calculated using IDT and BBR mixture creep data, respectively, are similar. Thermal stresses calculated from binder creep data are significantly different than thermal stresses calculated from mixture creep data. The effect of physical hardening is investigated for a limited number of materials, and the effect on thermal stresses is significant. [ABSTRACT FROM AUTHOR]

The use of fiber-reinforced composite materials for the construction and rehabilitation of civil engineering structures is relatively new. Structural members are routinely joined by bolted connections. Bolted connections are relatively easy to assemble and maintain, and are capable of transferring the high loads that typically occur in civil engineering structures. Currently there is a serious lack of knowledge on the behavior and design of bolted connections for fiber-reinforced composites. In light of this, a comprehensive experimental and analytical investigation was conducted at the University of Manitoba to study the behavior of bolted connections in composite materials appropriate for civil engineering applications. A total of 102 single-bolt connections were tested up to failure. The various parameters investigated were the width of the structural member, the edge distance, the thickness, and the direction of the fibers with respect to the applied load. The experimental program also included comprehensive material testing to determine the various in-plane material properties. This paper discusses the experimental program, test results, and various modes of failure as affected by the foregoing parameters. From the test results an analytical model and design procedure were developed as proposed in a companion paper. [ABSTRACT FROM AUTHOR]

Medium-density polyethylene (MDPE) pipes are extensively used for gas distribution systems in Canada and worldwide. MDPE pipe material possesses time-dependent mechanical properties that govern the performance of the pipes in service. In this research, an extensive laboratory investigation is carried out to investigate the time-dependent behavior of MDPE pipe material. Uniaxial tensile tests are conducted with samples (coupons) cut from the wall of a 60-mm diameter MDPE pipe. A tensile test with a sample of the full cross section of the pipe is also conducted to investigate the influence of sample type on the test results. The test program includes uniaxial testing at various strain rates ranging from 10−6/s to 10−2/s to capture the effects of loading rates, creep testing, and relaxation testing. The program revealed that the stress-strain responses of MDPE pipe material are highly nonlinear and strain rate-dependent. However, the strain rate effect is negligible below 10−6/s , which is termed herein as the "reference strain rate." A numerical technique for modeling time-dependent behavior is proposed using the features available in a commercially available finite element software, Abaqus. In this technique, strain rate-dependent stress-strain models are used to simulate loading and unloading responses, and a power-law type creep-law model is used to simulate the creep/relaxation behavior. The proposed modeling approach successfully simulated the test results. [ABSTRACT FROM AUTHOR]