Reliability-based assessment of flexural timber components with ultimate deflection performance

Assessing the deflection performance of existing flexural timber components is of paramount importance for making better, reliable, and substantiated decisions. The main purpose of this article is to propose four-level reliability index β and deflection criteria for updating existing flexural timber components (main beam, joist, purlin, and rafter) based on long-term deflection probabilistic model, limit state functions, and load combinations. The long-term deflection probabilistic model was obtained through creep deflection and short-term deflection model. Limit state functions were considered to be ultimate limit states of load-bearing capacity. In addition, four-level reliability index β were calculated by three live loads (residential live load, office live load, and snow live load) and seven load ratios ρ (0.2, 0.3, 0.5, 1.0, 2.0, 3.0, and 4.0). The results of proposed four-level criterion were illustrated with the reliable safety assessment for flexural timber components.

Determination of Support Minimum Rigid Stiffness for Piping Analysis

Pipe supports are represented as spring constants in piping analysis, and therefore a formal procedure is required to determine the spring constant values. Two current approaches are to enforce deflection criteria to ensure support rigidity or calculate the support stiffness values directly. However, the former approach results in overly conservative support designs and the latter approach becomes an iterative process of designing the supports and observing the response of the piping system. To avoid the issues presented by these methods, an alternative approach is presented which involves increasing values of support stiffness until change in natural frequency of the system diminishes. This method can help establish a lower bound (minimum rigid) stiffness above which there will be no significant change in the seismic response of the piping system. Using this approach only requires the support designs to have stiffness values at or above the minimum value without being concerned with detailed stiffness calculations or using deflection limits. This paper presents the methods and results of an expansive study to establish minimum rigid stiffness values for piping analysis.

Assessment of a smart concept for d15 shear piezoceramic direct torsion actuation

An experimentally proved smart concept for piezoceramic direct torsion actuation is here numerically assessed with regards to the bonding and segmentation influence on its behavior and performance. The TRESCA and deflection criteria analysis indicates that the actuator sandwiching with composites contributes to its integrity enhancement, but in the cost of its performance reduction. It is also found that modeling the core inter-rows and composites inter-layers bonding is more influential than that of the core rows segmentation. The conducted open-circuit modal analysis confirms that the inter-rows adhesive softens the actuator, while the inter-layers one stiffens it. Besides, the conducted adhesive parametric analysis indicates that, as expected, the most influential bonding parameters are its thickness and shear modulus.

Experimental Investigation on Effect of Carbon Nanotubes and Carbon Fibres on the Behavior of Plain Cement Mortar Composite Round Bars under Direct Tension

This paper investigates the behavior of reinforced cement mortar composite round bars with multiwalled carbon nanotubes (MWCNTs) and carbon fibers (CFs). The percentage of CFs was fixed at 2.25 wt% of cement, while the percentage of MWCNTs was fixed at 0.5, by wt% of cement. Dispersion of both MWCNTs and CFs was carried out using ultrasonic energy method. Composite round bars were tested under direct tension in order to evaluate their mechanical properties such as ultimate load, deflection criteria, and stress-strain behavior. These results were then compared with the results of plain cement control round bars. From the study, it is shown that the load carrying capacity of composite bars under direct tension is substantially higher than the plain controlled bar.