Adhesively Bonded and Translucent Glass Fiber Reinforced Polymer Sandwich Girders

An experimental program has been carried out to investigate the structural behavior of adhesively bonded glass fiber reinforced polymer (GFRP) sandwich girders. The girders, conceivable for main spans up to 20 m, are composed of translucent double sandwich element webs and adhesively bonded pultruded shape flanges. The continuous adhesive connections between web and flanges are loaded in a highly favorable manner without peeling stresses. Despite the complex load-carrying and failure behavior of the girders, simple calculation models can be applied. The successful girder experiments allowed for the development of a material-adapted construction method for new GFRP bridges and buildings. The integration of architectural aspects such as transparency, translucency, lighting, and color, as well as building physical aspects for buildings such as thermal insulation, substantially increases the overall value of the proposed constructions. Together with the lower life-cycle costs, this further justifies these new materials’ higher initial costs as compared with traditional materials.     

Characterization of Material Properties of HPS-485W (70 W) TMCP for Bridge Girder Applications

There are currently two methods of production for A 709 Grade HPS-485W (70 W)—quenching and tempering (Q&T) and thermomechanical controlled processing (TMCP). The TMCP enables plates to be rolled in longer lengths than is possible with Q&T; however, because of its recent introduction and a lack of material testing, relatively little is known concerning the effect of this new production method upon the intraplate variability of both tensile strength and toughness. Data from 96 tensile tests show that yield and ultimate strengths of HPS-485W (70 W) TMCP may be dependent upon plate thickness and orientation. The average yield strength was found to be lower than the 485 MPa (70 ksi) limit, while the average ultimate strength was within acceptable limits. Seventy-five Charpy V-Notch (CVN) specimens were tested, and all met the 48 J at ?23°C (35 ft-lb at ?10°F) AASHTO Zone III requirement for minimum toughness. Overall it was seen that HPS 485W (70 W) TMCP shows promise for bridge girder applications, but thicker plates do not currently meet all the ASTM A 709 standards, and should be reevaluated before being used in bridge construction on a large scale.     

Load Distribution Factors in Simply Supported Skew Bridges

Simply supported bridges consisting of five I-section concrete girders are analyzed using the finite-element method. The main parameters of this study are: girder spacing (1.8–2.7 m), span length (25–35 m), skew angle (0–60°), and different arrangements of internal transverse diaphragms. Results of reliable analysis based on the finite-element method show that, in right bridges, American Association of State Highway and Transportation Officials distribution factors are conservative and in skew bridges, these factors are very conservative.     

Fatigue Response of New Graphite/Epoxy-Concrete Girder

A new graphite/epoxy/concrete (G/E/C) cross section was developed and tested under fatigue loading with constant amplitude for one million cycles. The cross section consisted of a G/E box element, a G/E channel element, a concrete slab, and a concrete box formed by the walls of the G/E elements. Epoxy resin and vertical steel stirrups provided shear connection between G/E elements and the concrete slab. The results showed that the epoxy interface slipped after 150,000 cycles of fatigue loading. Softening of the girder continued for another 350,000 cycles of loading, after which the stiffness and strains stabilized. The failure testing of the girder after fatigue loading showed that the load and displacement capacities were only moderately reduced by fatigue loading.     

预应力薄壁斜腹箱梁施工工艺探讨

预应力薄壁箱梁因其外形美观、力学性能较好、惯性截面积大、剪力传递良好、综合经济指标优于其它预制梁体而被许多桥梁所采用,但由于其腹板倾斜,预制施工时易出现一些与直腹梁不同的情况。以武汉市中环线南环段高架桥25m预应力箱梁施工为对象,对预应力薄壁斜腹箱梁预制施工工艺进行探讨。     

Basic parametric study on corrugated web girders with cut outs

This paper presents a basic parametric study on steel girders with trapezoidally corrugated webs having cut outs. A finite element analysis is carried out to investigate the effect of cut outs in corrugated webs. This FE-modelling is conceived in ANSYS because of the program’s significant capability to account for the web stresses and out-of-plane buckling failure modes. The Finite element model of corrugated web plates is calibrated with theoretical study and finally a parameter study with a scope of application of cut outs in girders with corrugated web plates is performed. This procedure includes the influence of web height, length of parallel part, depth of corrugation, web configuration, location of cut out and its diameter. The analytical study shows that the influence of geometry of corrugated sheets with cut outs on the load capacity and buckling behaviour of the girder can be significant. With the help of the finite element model, the eigenvalue buckling analysis is carried out for all parameter combinations. The local buckling coefficients and the accompanying failure mechanisms are determined for several heights of web and for a wide range of the horizontal eccentricity of the cut out. With the help of this numerical research, design specifications are recommended in line with Eurocode 3.     

Live Load Distributions on an Impact-Damaged Prestressed Concrete Girder Bridge Repaired Using Prestressed CFRP Sheets

This paper describes detailed flexural behavior, including live load distributions, of a four-span prestressed concrete girder bridge supported by 14?m long C-shape girders (4 @ 14.05 = 56.2?m). The bridge has been damaged by frequent impact from heavy trucks, and repaired using prestressed carbon fiber-reinforced polymer sheets. A calibrated finite element analysis is conducted to investigate the flexural behavior (i.e., stress redistribution, deflection, live load distribution, and applied load effects) of the bridge in three different phases (i.e., undamaged, damaged, and repaired states) under various loading configurations. Strain localizations are noted at the damaged and repaired locations. Assessment of existing bridge codes such as the Association of State Highway and Transportation Officials Load Resistance Factor Design and Canadian Highway Bridge Design Code is conducted. The bridge codes predict well the nominal live load effect on the exterior girder, but underestimate the effect on the interior girders. A refined analysis may be recommended for this type of bridge.     

Flexural Behavior of an Ultrahigh-Performance Concrete I-Girder

The flexural behavior of an ultrahigh-performance concrete (UHPC) was investigated through the testing and related analysis of a full-scale prestressed I-girder. A 28?ksi (193?MPa) compressive strength steel fiber reinforced concrete was used to fabricate an 80?ft (24.4?m) long AASHTO Type II girder containing 26 prestressing strands and no mild steel reinforcement. Intermediate and final behaviors, including cracking, flexural stiffness, and moment capacity, were investigated. Test results are compared to predictions based on standard analytical procedures. A relationship between tensile strain and crack spacing is developed. The uniaxial stress-strain response of UHPC when subjected to flexural stresses in an I-girder is determined and is verified to be representative of both the stress and flexural stiffness behaviors of the girder. A flexural design philosophy for this type of girder is proposed.     

Investigating a Structural Form System for Concrete Girders Using Commercially Available GFRP Sheet-Pile Sections

This paper presents a new girder consisting of a trapezoidal pultruded glass fiber-reinforced polymer (GFRP) hat-shaped section commercially available as a sheet pile, but used in this study as a structural form for concrete. It can also offer continuity in the transverse direction through a pin-and-eye connection. Five 610?mm×325?mm and 3,300-mm-long girders were tested in flexure to examine different bond systems, voided and solid concrete cores, and the performance in positive and negative bending. Bond systems were wet adhesive bond to freshly cast concrete, adhesively bonded coarse aggregates, and mechanical shear studs. No slip was observed between concrete and the GFRP section until delamination failure occurred within a thin layer of cement mortar that remained attached to GFRP. The studs failed by pull out from the concrete flange. In general, 47–75% of the full strengths of concrete and GFRP were reached at ultimate bond failure. Wet adhesive bonding was the simplest and quickest to apply, while resulting in a comparable strength to other systems. A “moment-curvature” analytical model, incorporating a robust bond failure criterion, was developed, validated, and used in a parametric study. It showed that varying the concrete compressive strength or thickness of the GFRP section has insignificant effect on the bond failure load. Also, there are critical values for shear span-to-depth ratio, shear strength of cement mortar, concrete strength, and width of the top GFRP flange, beyond which, the desired flexural failure mode would precede bond failure.     

Analytical Model for CFRP-Strengthened Prestressed Concrete Girders Subject to Cyclic Loading

An analytical model is presented to simulate the behavior of prestressed concrete girders strengthened with various carbon fiber-reinforced polymer systems and subjected to static and cyclic loading. The initial concrete strains owing to prestressing and girder self weight load at the moment of the application of the strengthening system and the concrete cyclic creep as a result of the cyclic loading are considered in the model. Experimental results are used to validate the analytical model. Additionally, deflection and concrete strain increases on account of the cyclic loading are compared to the values provided by Comité Euro-International du Béton and Fédération Internationale de la Précontrainte (CEB-FIP) and Asso?i?o Brasileira de Normas Técnicas (NBR) 6118 codes. Deflection and concrete strain obtained from the analytical model were above those observed in the tested girders, especially after 100,000?cycles, owing to the logarithmic function used to express the fatigue behavior of concrete. In general, deflection provided by CEB-FIP was above experimental and analytical deflection, but otherwise concrete strain values provided by NBR 6118 were close to experimental results.