Richard M. Gutkowski

COMPOSITE REPAIR OF TIMBER STRUCTURES

Abstract An approach, using pultruded composites, to rejuvenate low aspect ratio timber beams, which model railroad bridge span timbers, is described. The approach focuses on overcoming the loss of shear properties by inserting fiberglass pultruded rods from the bottom to the top of the beam, through areas of damage. The concept includes the incorporation of an adhesive during the process of insertion, which not only bonds the reinforcing rods in-place, but also, fills adjacent cracks. Scale beam testing, with a variety of reinforcement cases, has been performed and the overall results are extremely positive, with test beams showing strong recovery of flexural properties and improvement in the strain to failure.

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.

UNIVERSITY TRANSPORTATION SURVEY: TRANSPORTATION IN UNIVERSITY COMMUNITIES

Universities and transit agencies across the United States have been finding innovative ways of providing and financing mobility services on and around university campuses. Many transit agencies are providing substantially more service and moving substantially more riders than their counterparts in nonuniversity environments. Determining what types of relationships exist between transit performance and university policies or practices is the research premise. To that end, the purpose is to document the types of transportation policies, demographics, and land use characteristics that exist on university campuses, and to examine the relationship between transit performance, land use on university campuses, types of university communities, university transportation and parking policies, and student demographics. These characteristics of university transportation systems were examined through demographic data and a mailed questionnaire. The questionnaire was sent to 48 universities and transit agencies across the United States, with 23 responding with enough valid data and information to be included in the study. It has been demonstrated in a significant number of university communities across the country that transit performance is enhanced dramatically by certain fare policies. However, that enhancement differs from one community to the next. It is believed that the answer to maximizing transit performance can be found in a combination of factors and that the optimum mix can be identified empirically.

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.

Three-Dimensional Modeling of Long-Term Structural Behavior of Wood-Concrete Composite Beams

AbstractThis paper presents a three-dimensional (3D) numerical model for capturing the time-dependent behavior of layered wood-concrete composite beams with notched shear key interlayer connections, subject to long-term static load and simultaneous exposure to naturally changing ambient environmental conditions, including temperature and relative humidity. For the wood material, the research extends the formulation of a previous rheological model, originally proposed for uniaxial stress state of wood exposed to moisture variations, to 3D finite-element modeling with a multiaxial stress state. For the concrete material, a standard creep model for uniaxial stress states was approximated using a generalized Maxwell’s model and then expanded to 3D formulations. The 3D model described in this paper was implemented via external user subroutines in the commercial software ABAQUS. Finite-element models for a wood-concrete composite beam with notched shear key were developed to model the diffusion problem of moist...

Pultruded composite shear spike for repair of timber members

Use of pultruded composites to rejuvenate low aspect ratio timber beams is described. Loss of shear resistance is restored by inserting fiberglass pultruded rods from the bottom to the top of the beam, through areas of damage. An adhesive is incorporated during the process of insertion, which bonds the reinforcing rods in-place and fills adjacent cracks. Scale beam testing, with a variety of reinforcement cases, has been performed and the overall results are extremely positive, with test beams showing strong recovery of flexural properties and improvement in the strain to failure.

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.

Analysis And Testing Of Composite Wood-concrete Floor/deck Systems

Experimental and analykal studies of composite wood-concrete floorldeck systems have been ongoing at Colorado State University. A novel shear keylanchor detail of overlaying solid wood floors in office buildings with a concrete layer, thus creating a composite floor, was adapted for this study. The detail utilizes a notch to transfer bearing stress and shear stress in the joined materials for interlayer force transfer, rather than connector shear. Compared to ordinary mechanical connectors, the connection detail develops a substantially higher degree of composite action. Systems are being studied for residences, offices etc. and short span bridges. Laboratory testing included pull-out tests on the anchors, interlayer slip tests on connection details, pilot load tests of full-scale beams and one-way floors and thick decks. This paper also describes the analflcal study of the mechanics of the interlayer force transfer, surface to surface contact stresses at the notched-anchor connection and nearby continuum behavior. A finite element formulation that includes line-to-line (L-L) and node-to-node (N-N) link elements was utilized. It is applied to interlayer slip specimens and layered beam test specimens. In the latter the degree of composite action is examined by comparing experimental results with rigorous layered finite element modeling of the global systems, with connection modeling included. To date the model is successful within the early limitations enacted for initially simplifjmg the simulation. Transactions on Modelling and Simulation vol 33,

FIELD STUDIES OF STRENGTHENED TIMBER RAILROAD BRIDGE

Comprehensive field testing had been done previously on a typical three-span, open-deck timber deck railroad bridge. The test program was done in cooperation with the Transportation Technology Center, Inc., of the Association of American Railroads. The bridge was subjected to static and moving train loads as well as controlled actuator ramp loading. The bridge was later stiffened by the addition of a stringer to each chord. The bridge was retested after the stiffening using moving train loads. Results of this field study are reported, and comparisons of the response of the bridge before and after the stiffening are made. The efficiency of the stiffening was between 82 and 97 percent.