Thomas E. Boothby

Three-dimensional modelling and full-scale testing of stone arch bridges

Abstract Existing test results of full-scale in-service masonry arch bridges are analysed to determine appropriate material properties for the modelling of this structural type. Three-dimensional nonlinear finite element models of three masonry arch bridges are generated using a commercially available finite element package. The behaviour of the masonry is replicated by use of a solid element that can have its stiffness modified by the development of cracks and crushing. The fill is modelled as a Drucker–Prager material, and the interface between the masonry and the fill is characterised as a frictional contact surface. The bridges are modelled under service loads, and the model results are compared to the results of a program of field testing of the structures. It is found that the assumption of a reasonable set of material properties, based on visual observations of the material and construction of the structure, implemented through a program of three-dimensional nonlinear finite element analysis enable good predictions of the actual behaviour of a masonry arch bridge.

Longitudinal and transverse effects in masonry arch assessment

Abstract Recent advances in the analysis of masonry arch bridges, substantiated by extensive testing programs in the United States and Europe, provide bridge engineers and inspectors with increasing confidence that reasonable estimates can be made of the capacity of these structures. Observations of ultimate strength testing indicate that spandrel walls and fill contribute greatly to the strength and stiffness of these structures, and that loads approaching the plastic collapse load can often be obtained. Observations from service load testing indicate that the development of cracking and non-linearity under service loads can be a significant indicator of the capacity of the structure. Modeling of these structures has shown the importance of restraint of the abutment to the overall resistance of the structure, and has recently shown the importance of transverse effects in diminishing the strength of structures with high spandrel walls or thin arch rings.

Test Methods for FRP-Concrete Systems Subjected to Mechanical Loads: State of the Art Review

This report addresses the methodology for determining the long-term behavior of bridge structures reinforced with fiber reinforced plastic (FRP) rods. In particular, a review of the existing literature on what has been done and what needs to be done for the development of accelerated test methods, with emphasis on mechanical loads, is presented. The focus of the report is on new, bonded FRP reinforcement for concrete bridge structures. Companion reports address stand-alone FRP systems subjected to mechanical loads, and stand-alone FRP and FRP-concrete systems subjected to environmental loads.

Analysis of bonding mechanisms of smooth and lugged FRP rods embedded in concrete

Abstract The bond behavior of two fundamental types of FRP reinforcement for concrete—smooth rods and lugged rods—has been investigated by examining experimental data and developing detailed finite-element models of these simple rod/concrete systems. The bond controlling parameters, identified by direct pull-out tests on embedded rods, were built into the models so that analytical studies of the effect of each parameter on bond could be carried out. The viability of the finite-element models, created by the use of commercial finite-element programs, was verified by comparing the predicted and experimentally obtained load versus slip and/or load versus longitudinal strain data. The models were used to predict the behavior of environmentally degraded rods. The moire method of strain analysis was used to investigate full-field, local strain distributions in flat, lugged rods embedded on the surface of concrete.

Evaluation of bond using FRP rods with axisymmetric deformations

Abstract This paper presents experimental results obtained with the direct pull-out test using machined and wrapped glass/vinylester, carbon/vinylester, and carbon/epoxy FRP rods with axisymmetric lugs. The typical results are given as nominal shear stress vs. free- and loaded-end slip. Experimental results obtained from strain probes used during the pull-out test are presented as shear stress vs. strain. Machined glass/vinylester FRP rods with embedded lengths including five and 10 lugs, and different lug widths and heights were studied. The failure mode consisted of the shearing off of the lugs without concrete damage. Four concrete mixtures with strengths ranging from 32 to 66.1 MPa were examined. Provided that enough confinement is used, it was found that the concrete strength has no noticeable effect on the shear strength and failure mode of FRP rods. Results showed that the FRP–concrete bond is controlled by the lug dimension and shear strength of the resin. The shear strength of the wrapped lugs is less than that of machined ones due to fiber orientation and weaker interfacial bond between the wrapped strands and rod surface.

Load testing and model simulations for a stone arch bridge

Service and high level load tests on a typical single span stone arch bridge in the south of Ireland and an associated set of three-dimensional nonlinear numerical analyses are discussed in this paper. The three-dimensional finite element models, which were generated using a commercially available finite element package, include the arch fill and a frictionless contact interface between this fill and the spandrel walls modelled with a nonlinear smeared crack material model. While this modelling strategy has been previously corroborated for service load levels, the results of the numerical model (which are compared with results from the experimental tests) also demonstrate the suitability of this modelling strategy at higher load levels. Finally, the suitability of three-dimensional solid models in the context of stone arch bridge assessment is discussed.

Effect of cyclic loading on bond behavior of GFRP rods embedded in concrete beams

Three types of glass fiber-reinforced plastic (GFRP) rods with different surface configurations were embedded in concrete beams to determine their bond behavior under cyclic loading. Load amplitudes and numbers of cycles were chosen based on the GFRP rod type and its bond behavior in virgin beams loaded monotonically to failure. After completion of cyclic loading, all beams were tested quasi-statically to failure to determine the residual bond strength. Results were presented as load-slip curves, load-midspan displacement curves, and slip versus number of cycles curves. In all types of GFRP rod evaluated, cumulative slip increased as the number of cycles and/ or loading amplitude increased. The bond strength in cyclically loaded beams increased relative to the bond strength in virgin beams.

Inelastic behavior of sand-lime mortar joint masonry arches

The response of masonry arch bridges to moving wheel loads was simulated in the laboratory by hanging steel weights from the center of gravity of selected voussoirs of four arches. Elastic and plastic deformations occur in the sand-lime mortar joints, where significant plastic behavior occurs under the first few cycles of loading, then an elastic response follows when the magnitude of load and the load cycles increase. The results from the ultimate load testing show that the collapse load depends significantly on the load history of the arch and that a sliding failure can override a four-hinge mechanism. A model of the arch ring using ADINA and the Drucker-Prager material model indicates that plastic accumulations do not occur after the first load cycle; however, it is believed that sliding occurs between the voussoirs and the mortar, producing small inelastic deformations under moving loads.

Elastic plastic stability of jointed masonry arches

A masonry arch is considered as an assembly of rigid blocks with deformable joints. The joint deformations are characterized by linear hardening plasticity under axial thrust and moment. The activation of four hinges in the arch results in a mechanism. Two types of mechanisms are considered in evaluating a structure: mortar controlled and block controlled. The mortar controlled mechanism is considered by Maiers theory of piecewise linear interacting yield surfaces with linear hardening. The hardening constants and their interactions may be found experimentally. It is found that stable and unstable mechanisms exist, which are predicted by applying first- and second-order optimality conditions to energy functions on a constrained state space. Bounds on the loads activating a mechanism may be determined using bounding theorems similar to the bounding theorems of plasticity. The block controlled behaviour of the system is predicted using Heymans application of rigid plastic analysis and the bounding theorems of plasticity.

A general lower and upper bound theorem of static stability

Abstract A statically stable state of a system subjected to conservative and dissipative forces is considered as a local minimum of the sum of the potential energy and the energy dissipated from the system subject to the kinematic constraints on the system. This stability criterion is investigated by the methods of optimization under constraints. A dual mathematical program, the maximization of the complementary energy of the system subject to equilibrium contraints, is constructed. Bounds on the kinematic state space of a system and energy dissipation are introduced as inequality constraints. Lower and upper bound conditions for the loads causing instability of the system are derived. By the upper bound condition, the system is unstable if the virtual work is negative in a kinematically admissible displacement, including rigid body components. By the lower bound condition, the system is stable if the gradient vectors of the active constraints with nonzero Lagrange multipliers span the space of feasible rigid body rotations. The existence of a nonempty feasible set for the dual program is also found to ensure the stability of the system.