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A conceptual design approach is presented that was applied in a multi-disciplinary project to develop innovative solutions for the US Army’s Future Combat System to negotiate 4-meter gaps on the battlefield. The design approach focused on seven steps that were founded on three specific techniques. The techniques included a dual approach to developing project objectives, a two-dimensional model based on risk and return to evaluate conceptual concepts, and a controlled convergence with iterative concept generation and selection. It is proposed that this conceptual design approach may be beneficial to other projects because of the commonality with the objectives associated with conceptual design, innovative solutions, and infrastructure systems. The development of unique design methods is necessary to meet a challenging design environment that seek innovative solutions for infrastructure systems. The conceptual design approach presented and illustrated in this paper addresses this challenge.

This research investigates the production of hybrid composite tubes by combining spirally wound paperboard tubes and fiber-reinforced polymer (FRP) materials using the pultrusion process to improve selected mechanical and physical properties of the paperboard tube. Higher natural frequencies of vibration of tubes used in the converting industry is needed in the marketplace because of continued pressure for throughput productivity improvements. This study focuses on hybrid tubes with increased natural frequencies of flexural vibration. A manufacturing feasibility study is conducted which determined that the pultrusion method is the most cost-effective process for this purpose. To evaluate the proposed method, a series of production trials is conducted using 1-in. (2.54 cm) diameter paperboard tubes as the internal mandrel with a thin layer (0.050 in. (0.13 cm)-0.15 in. (0.38 cm)) of FRP material pultruded on the outer surface. Trials are conducted with different FRP layer thicknesses, fiber architectures, and volume fractions. Bonding between the interface of the paperboard and the FRP layer is examined by a microscopy study, and flexural properties of the hybrid tubes are determined using modal analysis. Overall, the research project reveals that manufacturing composite FRP/paperboard tubes is feasible and that little modification is needed to the existing production machinery. In addition, the process results in a highly cost-effective method to produce hybrid paperboard and FRP tubes with high natural frequencies of vibration.

Synopsis: The punching shear capacity of concrete slabs reinforced with threedimensional fiber-reinforced polymer (FRP) double-layer reinforcement cages composed of glass fiber-reinforced pultruded grating elements has been investigated using full-scale experimental tests and a number of different analytical models. Test specimens were full-scale prototype bridge deck slabs with varying end restraint and support conditions, differing dimensions, and two different FRP bar fiber lay-ups. The tests results were compared with the punching shear models in ACI 318, ACI 440, Eurocode 2, BS 8110, CEB-FIB MC90, JSCE, and a number of models proposed in the literature specifically for FRP reinforced slabs. Based on this investigation a new empirical model has been developed to predict the punching shear capacity of double layer grids having either restrained or simply supported edges and including an overlapping splice. The model is shown to give reasonably good predictions for both simply supported and restrained slabs.

This paper offers an overview of an extensive series of flexural tests conducted on beams retrofitted with fiber reinforced polymer (FRP) plates using the mechanical fastening technique. The tests showed that strength gains close to that expected from conventionally-bonded FRP can be obtained and the failure mode is actually much more ductile than with conventional FRP upgrades. Results of several analytical parametric studies are also given, providing insight into the effect of variations in material and geometric properties of the upgraded beams.

This paper focuses on the use of explicit finite-element (FE) analysis tools to predict the behavior of fiber-reinforced polymer (FRP) composite grid reinforced concrete beams subjected to 4-point bending. Predictions were obtained using LS-DYNA, an explicit FE program widely used for the nonlinear transient analysis of structures. The composite grid was modeled in a discrete manner using beam and shell elements, connected to a concrete solid mesh. The load-deflection characteristics obtained from the simulations show good correlation with the experimental data. A detailed FE substructure model was also developed to further analyze the stress state of the main longitudinal reinforcement at ultimate conditions. Based on this analysis, a procedure was proposed for the analysis of composite grid reinforced concrete beams that accounts for different failure modes. A comparison of the proposed approach with experimental data indicated that the procedure provides a good lower bound for conservative predictions of load-carrying capacity.

The authors attempted to (1) present a so-called unified analytical equation for estimating the compressive strength of pultruded columns; (2) investigate the accuracy of their proposed equation by comparing analytical and experimental results; and (3) conduct Monte Carlo simulations of their selected unified equation to obtain a resistance factor for use in a load and resistance design-based format. The authors’ successful attempt to curve-fit experimental data with a mathematical function found in the literature falls short of providing a well-established and practical formulation that describes the behavior of axially compressed pultruded structural members. The discusser wishes to address the first two issues by providing background information on the unreferenced work that the authors used in their paper and to point out some typical pitfalls and frequent misconceptions contained in the authors’ article. The procedure for calculating the compressive strength of pultruded columns presented by the authors originated more than five decades ago with Ylinen (1956). Ylinen investigated the buckling strength of steel columns in the inelastic range, basing his analysis on the tangent modulus concept advocated by Engesser (1889; 1895a, b), where the average buckling stress is expressed in the form

The U.S. military must often deploy to other countries where bridges may have insufficient strength for their heavy tactical vehicles. In recent years, fiber-reinforced polymeric (FRP) materials have emerged as a viable retrofit scheme for strengthening reinforced concrete bridges. However, because of stringent application requirements, long cure times, and climatic sensitivity, this technology has yet to prove feasible for military operations where time is often the most critical factor. Furthermore, Army operations are conducted under the broadest range of climatic conditions. For these reasons, the U.S. Army Engineer Research and Development Center has undertaken to develop a unique FRP application methodology utilizing powder-actuated mechanical fasteners (i.e., nails from a conventional carpenter's nail gun). This method shows great promise for military applications, since no substrate preparation or adhesive curing is required. Additionally, this method should work well in all but the most extreme environments. For this purpose, numerous laboratory tests have been conducted, and the results have been very promising. This report provides a detailed summary of the first 2 years of testing on this concept.

Thin-walled open-section beams constructed of panels of laminated composite materials and subjected to transverse loading are considered in this paper. Such beams are used as stiffeners in stiffened-panel construction for aerospace vehicles and in composite structural frames for rotorcraft vehicles. Beams constructed of panels having generally anisotropic mechanical properties are considered. Due to anisotropically induced normal-shear coupling effects these open-section beams will rotate and deflect laterally out-of-plane under the action of in-plane transverse loads in addition to their expected transverse deflection. A one-dimensional modified beam theory is used to describe the coupled deflection and rotation of these beams. The theory, which is intended for preliminary design studies, can be used to obtain inexpensive 'hand-calculation' predictions of the behavior of anisotropic thin-walled beams. .Predictions of the theory are compared with predictions of a 3-D finite element analysis in which the beams are constructed of general laminated shell elements. Good agreement between the theory and the finite element results is shown.

Existing methods of flexural strengthening of reinforced concrete beams (RCBs) with fiber-reinforced polymer (FRP) strips require time-consuming and often difficult preparation to yield adequate bond strength between the FRP strip and the concrete substrate. This research presents a feasibility study of an alternative method of attaching FRP strips to RCBs. Off-the-shelf powder actuated fasteners are used to attach pultruded FRP strips to the concrete. Small-sized RCBs strengthened with this method were tested, and the results were compared with those from beams strengthened with conventional bonding methods and to results from control beams. Small-size RCBs strengthened using powder actuated fasteners achieved 65-70% of the increase in capacity of the beams strengthened using the conventional bonding method; however, the fastening method is extremely rapid and the failure modes of the beams strengthened by the fastening method were more ductile than those using the bonded method.

Results of tests of ten concrete beams reinforced with fiber-reinforced plastic grids fabricated from small pultruded profiles are presented. The beams were designed to investigate the behavior and performance of the grids when used to reinforce beams that develop significant flexural-strength cracking (a/d = 3). Different grids were designed to study the influence of the main bars, vertical bars and transverse bars (cross-rods) of the grid on the failure loads and failure modes. From the results of the testing it was concluded that pultruded grids can provide effective shear reinforcement, however, their design must account for failure of the main bars in the shear span. Overreinforced beams failed in a somewhat more ductile manner than underreinforced beams.

A research study on the effect of material degradation of fiber reinforced plastic (FRP) reinforcing bars on their bond strength and bond stiffness properties is reported in this paper. A convenient new embedded-rod test (ERT) specimen was developed and used in the study. The ERT specimen is recommended for future environmental degradation studies of FRP bars. The ERT specimen enables microscopic and mechanical tests to be performed on portions of the same FRP bar after it has been subjected to environmental conditioning while it is embedded in concrete. Photographs and scanning electron micrographs were used to investigate the nature of the degradation in the polyester and vinylester resin matrices and the E-glass fibers of smooth and deformed FRP bars. Pullout tests were used to investigate the bond strength and bond stiffness characteristics of the FRP bars. A descriptive model of the mechanism of the deterioration of the FRP material is proposed to relate the decreases in bond strengths and stiffnesses to the degradation of the materials in the FRP bars.

An experimental and analytical study was conducted to investigate the feasibility of developing three-dimensional fiber-reinforced plastic (FRP) grating cages to reinforce concrete members. Experimental FRP cages, fabricated from off-the-shelf commercially manufactured pultruded FRP profiles, were used to reinforce three concrete beams which were tested to failure. The performance of the FRP grating cage reinforced beams was compared with that of a control beam reinforced with conventional steel rebars. The results of the testing are given and a detailed analysis of the failure modes of the FRP reinforced beams is provided. A simplified analytical model is proposed to calculate the failure load of the beams. A truss model is used to predict deflection at failure. Predictions of the proposed models agree well with the experimental data. The construction practice potential of using the FRP grating cages is discussed. The pilot study indicates that the future development of FRP grating cages for concrete reinforcement would appear to be warranted.

A novel method for the analysis of frames constructed of thin-walled members of anisotropic composite materials is presented in this paper. The method accounts for non-isotropic coupling effects that exist in composite material beams due to the anisotropy of the composite material laminates that form the thin-walled cross-section. The method also accounts for warping effects known to be significant in thin-walled members. The analysis is performed by the direct stiffness matrix method utilizing a new approach that divides each thin-walled member of the frame into one-dimensional warping-beam superelements and non-warping conventional beam elements. The element stiffness matrices for these two one-dimensional beam elements are obtained by a numerical procedure that is based on the classical force method of analysis. The stiffness matrices of both beam elements are 12 × 12 matrices corresponding to the six degrees of freedom per node required for conventional space frame analysis. The remarkable feature of this representation is that warping is accounted for without introducing additional degrees of freedom to account for the bimoment and warping twist in the members. This is accomplished by use of the warping-beam superelement that linearizes the regions of non-uniform torsion in the thin-walled beam. Examples of space frame structures constructed of thin-walled composite material I-beams are presented to demonstrate the method. Results of analyses using the proposed method are compared with those obtained from two-dimensional finite element models.

As a cosponsor of the ASCE Journal of Composites for Construction, the International Institute for FRP in Construction (IIFC) has an official agreement with the Journal to publish occasional special issues. The Journal had its first IIFC-centric special issue in April 2007, and the present issue represents the second such edition. A proposal was made to ASCE that this IIFC-sponsored issue would be in honor of Professor Urs Meier, and this proposal was received with enthusiastic endorsement. It was felt that this would be timely and would constitute a fitting recognition in view of Professor Meier’s pioneering contributions to the field of fiberreinforced polymers (FRPs) in construction. It was also suggested that it would be most appropriate if there were a strong connection between the papers of the special issue and Professor Meier, either through working relationships between the authors or because the paper topics strongly relate to his work. To say that Urs Meier has enjoyed an illustrious professional career is a definite understatement. Urs Meier has held various positions at the Swiss Federal Laboratories for Materials Testing and Research (Empa), an institute that has approximately 800 coworkers and laboratory technicians in Dubendorf-Zurich, Switzerland. In 1983, Urs Meier rose to the rank of Deputy Director General of Empa, a position that he held until his recent retirement. In addition, he has also been lecturer and professor at the Swiss Federal Institute of Technology (ETH) in Zurich. Over the years, Urs Meier’s accomplishments in the application of FRPs in civil engineering have had a tremendous impact on the field; indeed, he has received many accolades and worldwide recognition for his pioneering work. Especially noteworthy is his work on the poststrengthening of civil structures with carbon-fiber-reinforced polymer (CFRP) strips, which has been successfully implemented at a growing rate worldwide, and the application of CFRP stay-and posttensioning cables. Urs Meier has been a prolific researcher and engineer with more than 250 publications to his credit. He has received numerous international best paper and technical innovation awards for excellence for his research and development contributions. He has also developed a number of worldwide recognized patents within the field. Other tributes to Urs Meier include the establishment by the ISIS Canada Research Network (Intelligent Sensing for Innovative Structures—an organization of the Canadian government) of a specially dedicated Urs Meier Scholarship and his being acclaimed Doctor of Engineering, honoris causa, by the Royal Military College of Canada in 2005. In preparing this special issue, a number of prospective authors from the international community were initially contacted by the guest editors. Each submission was then subjected to the usual rigorous review process of the Journal; this was handled by the Journal editor in chief, Professor Charles Bakis, according to the standard procedures. Ultimately, 11 papers emanating from Canada, Greece, Japan, Poland, Switzerland, the United Kingdom, and the United States were selected. We believe that these papers reflect the various topics that relate to Urs Meier’s contributions to the use of FRPs in civil engineering applications. They are an excellent representation of the depth and breadth of Urs Meier’s interests. We are delighted to present this special issue of the Journal of Composites for Construction to honor Professor Urs Meier for his remarkable achievements and exemplary dedication to this field. His accomplishments, leadership, and impact have been outstanding. This community has been extremely fortunate to benefit from both his technical and personal contributions. On behalf of all our colleagues, we offer our thanks and extend our very best wishes to this extraordinary researcher, teacher, engineer, and individual.

The physical and mechanical properties of polymer matrix composite materials, often referred to as fiber-reinforced plastic or fiber-reinforced polymer (FRP) materials, are discussed in this chapter. These properties are discussed with an emphasis on the potential uses of composite materials as reinforcements for concrete. The term FRP reinforcements is used to describe the composite material products developed for this purpose. Properties of composite materials that are likely to be significant for FRP reinforcements are identified. The influence of the properties of the constituents, viz , the fibers, resins, fillers and additives, on the properties of FRP reinforcements is discussed. Emphasis is placed on issues of heterogeneity and anisotropy of composite materials and how they can be expected to affect the properties FRP reinforcements.

The natural frequencies and mode shapes of thin-walled beams constructed of walls, or panels, of advanced composite materials depend upon both the geometry of the cross-section and the mechanical properties of the materials used in the panels. A shear deformation beam theory having the form of a Timoshenko beam theory is used to investigate the influence of these design variables. It is found that the maximum stiffness of a particular beam configuration is obtained when the contributions from the bending and shearing modes of deformation are optimized. Results show the influence of shear deformation even in the fundamental mode of vibration. Simply-supported, cantilever and free-free beams of various cross-sectional shapes and materials are analyzed.

An experimental investigation of plastic zone geometry, plastic strain magnitudes, and fracture strength was conducted on unidirectionally reinforced boron-aluminum specimens with a center notch. The results indicate that long, discrete plastic shear zones grow from the notch tip in the fiber direction well before fracture. However, no plastic zones were detected along the fracture surface. The plastic zones blunt the notch and cause a significant stress redistribution in the notched specimens. A model is proposed for evaluation of the resulting stress fields. The companion Part II of the paper describes an analysis of the model and its use in fracture strength predictions.

The shear coefficient is obtained for multicelled thin-walled composite material beams in terms of the elastic properties of the walls, or panels, which form the beam. The method presented follows one discussed in a previous paper in which shear coefficients were found for open or single cell symmetrical cross-sections by Cowper's method. In order to apply Cowper's method to the multicelled section the shear flow around the cross-section must be modified to account for lateral distortion of the cross-section due to Poisson effects. As an example, a detailed calculation for a double-cell composite box beam is given. Additional results are given for a triple-cell box beam. The effect of varying the properties of the panels around the cross-section is investigated.

A beam theory is presented that is formulated in terms of the in-plane elastic properties of the panels of the cross-section of a thin-walled composite beam. Shear deformation is accounted for by using a suitable form of the Timoshenko beam theory together with a modified form of the shear coefficient. The theory gives both the bending deflection and the shear deflection of a beam loaded by an applied transverse load. Numerical and graphical results obtained from a computer code show the effects of using different composite material systems and lay-ups in the panels of typical beams.

Constitutive laws are presented for the inelastic analysis of laminated composite plates. The implications of using an elastoplastic theory, applied in a stress-resultant formulation, are discussed and investigated. Two different stress-resultant plasticity theories are proposed, both of which overlook the matrix and fiber inelastic behavior and describe the inelastic response of the laminate as a function of overall laminate properties. Results from numerical experiments with the proposed models are compared with results obtained using a micromechanical elastoplastic composite constitutive model.

The shear coefficient in Timoshenko beam theory is obtained for thin-walled beams constructed of laminated panels of composite material using a variation of the method due to Cowper. Formulae are presented for a class of such composite beams. Comparisons are made with Cowper's original formulae for the case of an isotropic beam. The effect of shear deformation under static loading of typical composite beams is investigated. A procedure is outlined for the distribution of plies in the laminated panels to achieve optimal response under static or dynamic loading.

The use of experimental modal analysis to obtain the dynamic mechanical properties of spirally wound paper tubes is investigated. Based on experimentally measured natural frequencies in the free-free mode of transverse vibration, tube flexural stiffness properties are predicted using three beam theories: Euler-Bernoulli beam theory, Timoshenko beam theory for isotropic materials, and Timoshenko beam theory for anisotropic materials.