Jay A. Puckett

B-spline compound strip analysis of stiffened plates under transverse loading

Abstract An improved compound strip method based on the unequally spaced cubic B-spline is presented. The in-plane displacements are also incorporated in this approach to analyze the concentrically and eccentrically stiffened plates. Several of the available theoretical, experimental, and numerical results have been compared with those obtained from the proposed method. The accuracy and efficiency of this method is verified.

EFFECTS OF GEOTEXTILES ON LATERAL PRESSURE AND DEFORMATION IN HIGHWAY EMBANKMENTS

Abstract A procedure to lower the lateral loading acting on the back of a highway abutment wall utilizing geotextiles is described. A gap is formed between the wall and the geotextile reinforced backfill using either corrugated cardboard (which is wetted after construction) or removable plywood forms. This allows the backfill to deform and go into the active state. The fabric sustains the resulting tensile forces, essentially forming a free-standing fabric wall behind the abutment. Laboratory testing indicates that less than 25 mm lateral movement is required to reduce lateral loads by 90 percent. Four reinforcement schemes were compared on two Interstate bridges. The fills were instrumented with inclinometers, Sondex tubing and pressure cells. The results indicate that an initial gap reduces the lateral load to essentially zero and settlements were no greater with the voided system than that experienced by a nonvoided fill

Plate bending analysis by unequally spaced splines

Abstract A cubic B-spline finite strip method (BFSM) is developed to analyze thin plates in bending. The basic mathematical relationships are derived for a direct stiffness formulation using a series type strip displacement function. Longitudinal behavior is modeled by a spline series in which unequal spline spacing is permitted. This feature allows local refinement of the discretization near patch and concentrated loads. Accuracy and convergence vis-a-vis alternative methods are compared. These include various finite element models, the conventional finite strip method and the BFSM with equally spaced splines. Comparisons show comparable accuracy with improved convergence. Oscillatory convergence due to Gibbs phenomenon, evident in some of the models, is avoided in the BFSM.

Compound strip method for the buckling analysis of continuous plates

Abstract A special finite strip method is developed for the analysis of linear buckling of flat plate systems that are continuous over non-rigid supports. This approach incorporates the effect of support elements in a direct stiffness methodology. The stiffness contribution of the support elements adds directly to the plate strip stiffness matrices at the element level prior to assembly. This summation of plate and support stiffness contributions forms a substructure, which is termed a compound strip. The compound strip methodology may be readily employed for the enhancement of computer programs based on traditional finite strip procedures. The validity of the compound strip method for elastic buckling analysis is demonstrated in two examples. The critical loads based on compound strip methodology compare favorably with those obtained with the finite element method.

The finite layer method for groundwater flow models

The finite layer method (FLM) is an extension of the finite strip method familiar in structural engineering. The idea behind the method is to discretize two space dimensions using truncated Fourier series, approximating variations in the third via finite elements. The eigenfunctions used in the Fourier expansions are orthogonal, and, consequently, the Galerkin integrations decouple the weighted residual equations associated with different Fourier modes. The method therefore reduces three-dimensional problems to sets of independent matrix equations that one can solve either sequentially on a microcomputer or concurrently on a parallel processor. The latter capability makes the method suitable for such computationally intensive applications as optimization and inverse problems. Four groundwater flow applications are presented to demonstrate the effectiveness of FLM as a forward solver.

Application of the compound strip method for the analysis of slab-girder bridges

Abstract The compound strip method is illustrated for the analysis of slab-girder bridges modeled as a linear elastic plate continuous over deflecting supports. This approach incorporates the effects of support elements in a direct stiffness methodology by creating a substructure composed of plate. beam. and column elements which is termed a “compound strip.” The theory and application of the compound strip method is presented. The finite element and compound strip methods are compared in an illustrative analysis for a slab-girder bridge. The results of the compound strip analysis compare well with the finite element method. The methodology presented herein can be used to efficiently model any slab-girder bridge configuration. Typically, the compound strip method requires significantly less computational resources than does the finite element method and is well suited for use on todays microcomputers.

BrIM for project delivery and the life-cycle: state of the art

Bridge Information Modeling (BrIM) was introduced to bridge enterprise stakeholders in design, construction, operations, and management. These stakeholders are increasingly realizing that a well thought out leveraging of bridge data for multiple purposes through the entire bridge life cycle is important. This paper surveys the genesis and development of BrIM supported by NSBA, NCHRP, AASHTO, and FHWA. This includes aspects that distinguish it from its close cousin, Building Information Modeling (BIM). Principal questions, issues, and challenges that have been raised by various stakeholders about BrIM are summarized to help clarify the way forward to increased industry acceptance and deployment of BrIM-enabled workflow.

Framework for Simplified Live Load Distribution-Factor Computations

The live load distribution-factor (LLDF) equations in the AASHTO-LRFD specifications were developed under National Cooperative Highway Research Program (NCHRP) Project 12-26. These equations include limited ranges of applicability, and when these ranges are exceeded, a refined analysis must be used. Additionally, the multiple-presence factors, bias, and variability with respect to the rigorous estimates are obscurely embedded. Herein, a simplified LLDF framework is provided. The effects of analysis uncertainty, variability, and multiple presence are separated and distinctly defined. This separation provides specification writers with the opportunity to use different multiple-presence and variability models. LLDFs were calculated using several simplified methods and grillage analyses for over 1,500 bridges. Based on the comparison, two simplified methods were further studied: adjusted uniform distribution and adjusted lever rule methods. Calibration factors were used to their improve accuracy. Seventy-four...

Simplified Load Distribution for Vehicles with Nonstandard Axle Gauges

Several simplified methods have been developed to determine the live-load distribution factors for overweight vehicles on slab-on-girder bridges; however, these methods were developed for vehicles with standard axles. Many vehicles exist with nonstandard axle configurations, such as two-wheel axles that are wider than 6 ft (1.83 m) and four-wheel axles with wheels that are evenly or unevenly spaced. For these vehicles, a rigorous analysis is generally desired but is often deemed uneconomical. Therefore, a simplified method should be an asset to the bridge community and the trucking industry. A simplified method for determining live-load distribution factors for vehicles with nonstandard axle configurations is presented. Distribution factor formulas for moment and shear in interior and exterior girders are given. These formulas account for the transverse axle configurations that compose a vehicle. Several two- and four-wheel axle configurations are considered. The distribution factor formulas for slab-on-girder bridges presented in the AASHTO LRFD Bridge Design Specifications are incorporated into the proposed simplified method. The simplified method formulas were developed to approximate the results from a rigorous finite strip method. Comparisons are presented as verification of the accuracy of the simplified method. The simplified method results are usually conservative and correlate reasonably well with the rigorous results. In general, simplified methods worked better for interior girders than for exterior girders, and moment was better predicted than shear.

Spline compound strip analysis of folded plate structures with intermediate supports

Abstract A B-spline column element in 3D space is derived and combined with the B-spline compound strip method for the analysis of plate-type structures (e.g. folded plates, box-girders, etc.) with intermediate supports. A direct stiffness method is used. Numerical examples demonstrate the advantages of this method: accuracy, efficiency and simplicity.