Mechanics of Microspheres Reinforced Hollow Microcells

Emerging polymeric foams exhibiting unique microstructure of microspherical shells with reinforcing dense microspheres creates a new opportunity for impact-tolerant foam paddings in sport gears applications. This paper describes the static response of reinforced microcell consisting of an outer spherical shell and uniformly distributed microspheres while quantifying the stiffening effect. The distribution of the microspheres is illustrated using the Fourier series, allowing tuning of the reinforcing strategy. Expressions of the external and internal works are derived, whereas the Ritz energy method is adopted to calculate the deformations due to a compressive load distributed over a range of areas. Emphasis is given to the effect of the geometrical attributes of the microcell and the reinforcing microspheres on the resulting deformation response and stiffening effect. The framework is used to investigate the response of several case studies to elucidate the effects of relative radii ratio, reinforcement density, microcell wall thickness, and loading configurations on the stiffness. A new normalized strain energy parameter is introduced to simplify and accelerate the analysis while providing insights on the underpinnings of the observed buckling response. The results strongly suggest the viability of the newly discovered foam microstructure in managing static loads while providing an opportunity to strategically tune the mechanical response using the analytical framework presented herein.

Stability Analysis of Tunnel Face Reinforced with Longitudinal Fiberglass Dowels Together with Steel Pipe Umbrella

When tunnels are constructed under difficult geotechnical conditions in urban areas, tunnel face stability is one of the main issues to be addressed. To ensure tunnel face stability and reduce the impact of tunneling on adjacent structures, a few alternative procedures of ground reinforcement should be adopted, which includes reinforcing the soil ahead of the face using longitudinal fiberglass dowels alone or together with a steel pipe umbrella. It is of great academic value and engineering signification to reasonably determine the limit reinforcement density of these ground reinforcements. In this paper, an analytical prediction model is proposed by using the limit analysis method to analyze the tunnel face stability, and the favorable effects of longitudinal fiberglass dowels and steel pipe umbrella on tunnel face stability are investigated quantitatively. The analytical prediction model consists of a wedge ahead of the tunnel face, distributed force acting on the wedge exerted by overlying ground, and the support forces stem from the longitudinal fiberglass dowels. Moreover, sensitivity analysis is conducted to study the effect of the depth of cover, the tunnel shape, the reinforcement installation interval and the reduction factor on the required limit reinforcement density.

Systematic Changes in Preference for Schedule-Thinning Arrangements as a Function of Relative Reinforcement Density

We treated destructive behavior maintained by both social-positive (i.e., access to tangibles) and social-negative (i.e., escape from demands) reinforcement in an individual diagnosed with autism spectrum disorder using functional communication training (FCT). We then thinned the schedule of reinforcement for the tangible function using a multiple schedule (mult FCT) and later thinned the availability of escape using a chained schedule (chain FCT). Both treatments proved effective at maintaining functional communicative responses while decreasing destructive behavior to near-zero levels. In addition, treatment effects maintained when we rapidly thinned mult FCT to the terminal schedule. Throughout chain-FCT schedule thinning, we assessed client preference for each schedule-thinning arrangement (mult FCT or chain FCT) using a concurrent-chains procedure. Client preference reliably shifted from chain FCT to mult FCT as the response requirement increased and the proportion of session spent in reinforcement began to favor mult FCT. We discuss the clinical implications of these findings.

Stiffness-Displacement Correlation from the RC Shear Wall Tests of the SAFE Program: Derivation of a Capacity Line Model

The response of 13 reinforced concrete shear walls submitted to successive seismic tests has been postprocessed to produce time histories of secant stiffness and displacement oscillation amplitude. For every wall an envelope curve of displacement amplitude versus stiffness is identified which is fairly modelled by a straight line in double logarithmic scale. This relatively simple model, when used as a capacity line in combination with the demand response spectrum, is able to predict in an approximate manner the maximum response to the applied earthquakes. Moreover, the graphic representation of the demand spectrum and a unique model capacity line for a group of equal walls with different assumed design frequencies on them gives a visual interpretation of the different safety margins observed in the experiments for the respective walls. The same method allows as well constructing vulnerability curves for any design frequency or spectrum. Finally, the comparison of the different identified line models for the different walls allows us to assess the qualitative effect on the behaviour of parameters such as the reinforcement density or the added normal load.

Selection of Construction Parameters in Heading Pre-Reinforcement Working Method for Liuyang River Tunnel on Wuhan-Guangzhou High-Speed Railway

The Liuyang River Tunnel on Wuhan-Guangzhou High-Speed Railway goes through the bottom of Liuyang River, the geological condition of which wall rock is not suitable for the construction. The paper proposes the heading pre-reinforcement method, namely pre-reinforcing core soil ahead of heading with fiberglass rockbolt in construction in order to optimize the construction methods and avoid both the deformation inside the tunnel and surface subsidence, and to ensure safety of tunnel construction. In order to determine the reasonable construction parameters, the paper obtains reinforcement density and length of fiberglass rockbolt, pre-reinforcement method on outline of heading, excavation step length and other construction parameters, by the numerical simulation, the indoor model tests and other methods, and analyzes its sensitivity. It is shown by the practices in construction that the selected parameters are reasonable and significantly effective, thus providing valuable experience for promotion and application of heading pre-reinforcement method.