Response of tubular FRP arches for bridge construction to concretefilling loads
Publication Name: ASCE Journal of Composites for Construction
The FRP arch bridge system is composed of hollow fiber reinforced polymer (FRP) arches with a circular cross-section that are filled in place with concrete, connected with corrugated decking, and buried under soil. The objective of this study is to examine the behavior and capacity of these arches during filling with wet concrete – when they are most vulnerable. When concrete is first poured as a fluid it lacks strength and the FRP shell of the arch must hold the weight of the wet concrete, making the arch deflect globally and the cross section deform into an ellipse, known as ovalization, from bending. The elliptic cross section reduces the local buckling capacity of the arch. Typically, the arch is filled through a hole drilled at the apex; this hole further reduces the buckling capacity of an arch. Local buckling, collapse from irrecoverable cross-sectional shape change, is driven by compressive stress. Short, hollow, FRP tube specimens were tested in axial compression to assess the materially- and geometrically-dependent local buckling capacity for the arches. Constant flow water loading tests on long bending beam specimens have shown similar failure stresses in the compression face to compression testing and demonstrated less ovalization occurs than anticipated. A finite-element model created from the results of these tests and specimen material and geometric properties serves as a general-purpose tool for predicting shell buckling capacity. Additionally, finite-element models of entire arches were created to simulate the loads and shell stresses from concrete filling. Predictive results are compared to measured strains and deflections found in filling arches both in the laboratory and the field. Primary conclusions of this research are that pre-existing models poorly predict local buckling capacity of arches due to defects or holes and buckling models with concrete filling holes have improved accuracy over normal cylindrical models. Finite element shell models provide an improved solution for predicting capacity for specimens with holes. A reduced elastic modulus region around the hole has been used as a fitting parameter. Future testing of additional geometries is needed to determine the adequacy of the fitting parameter.