Joshua D. Clapp

Computationally Efficient Finite-Element Modeling of Braided Inflatable Structural Members with Axial Reinforcing

AbstractBraided, inflatable structural members with axial reinforcing cords have the ability to accommodate loading with a low mass and small storage volume. These members are particularly attracti...

Simulation of Buried Arch Bridge Response to Backfilling and Live Loading

AbstractIn this study, soil–structure interaction in a buried arch bridge system is numerically investigated with two models. Model predictions of arch bending moments and ultimate capacities are compared with the load test performance results of two buried structures from a companion paper. A novel finite-element model was developed using an arch discretized with beam elements and soil discretized with spring elements initialized during progressive backfill simulation. Nonlinear soil-spring force is determined from vertical overburden pressure and earth pressure coefficient dependent on arch deflection. A nonlinear soil-continuum finite-element model was developed using software with Mohr-Coulomb soil plasticity. Experimental moments are compared with model results for backfilling, a series of service-level line loads, and ultimate capacity with an apex line load. The soil-spring model does reasonably well at predicting arch moments and ultimate capacity, and the incorporation of deflection-dependent ear...

Back-Calculated Pavement Layer Modulus Values of Geogrid Reinforced Test Sections

A study was conducted on full-scale pavement test sections to assess base reinforcement with geogrid in flexible pavements. Two thicknesses of asphalt and two thicknesses of base course were tested. Four test sections were reinforced with geogrid placed at the base/subgrade interface, and there were four matching control sections constructed on one subgrade. A heavy vehicle simulator loaded all the test sections. After construction, the subgrade was conditioned to a lower modulus value by adding water to the test sections, and the response was monitored using falling weight deflectometer (FWD) testing. In addition, FWD testing was also performed immediately prior to and after traffic loading in order to monitor the modulus of the subgrade and base layers. The subgrade modulus values were greatly affected by water content, but also experienced a significant decrease from immediately before to immediately after application of traffic. The modulus values then recovered over time. The base modulus values demonstrated a similar response when traffic was applied. The average modulus values for the base courses reinforced with geogrid were on average 1.34 times those for the base courses in the control sections throughout the project.

Withdrawal Capacity of Plain, Annular Shank, and Helical Shank Nail Fasteners in Spruce-Pine-Fir Lumber

Abstract This study examines the withdrawal load and energy capacity of three types of nail fasteners that are commonly used to attach sheathing to framing members: 8d common, annular ring shank, a...

Load-Deformation Response of Pressurized Tubular Fabric Arches

Pressurized fabric arches are lightweight, portable structural members fabricated from a continuously woven or braided fabric tube and an internal impermeable bladder. This study examines the load-deflection and buckling response of semi-circular, inflated fabric arches. Experiments on the load-deformation response of a woven and braided fabric arch tested over a range of inflation pressures are detailed. A quadratic Timoshenko beam finite element previously developed for the small deformation analysis of beams and beamcolumns is extended to the large-deformation in-plane analysis of arches with a co-rotational formulation. Response simulations that include fabric wrinkling, work done by pressure, and geometric nonlinearity are shown to accurately predict measured, pressure-dependent arch load-deformation response. Additional analyses indicate that inflation pressure significantly affects the buckling capacity of both deep and shallow arches. The effect of arch included angle Θ is also studied with respect to buckling. Experimental measurements of braided arch load-displacement response provide a starting point for extending the beam finite element to analyze braided arch response.