Shear stud connection development for steel stringer highway bridges with hardwood glulam timber deck

A new connection detail which consists of Nelson shear studs, Sikadur 42 Grout Pak epoxy grout, and a stepped receiver hole in wood glulam, was developed for attaching hardwood glulam decks to steel bridge girders. Experimental and analytical investigations were conducted for the inclusion of the new connection detail in bridge design standards. The experimental investigation included: (1) determination of the initial connection strength and stiffness in shear parallel-to-grain, perpendicular-to-grain, and in direct withdrawal; (2) determination of the dowel bearing strength of red maple glulam material perpendicular-to-grain using a 2-9/16 in (65.1 mm) diameter steel dowel; (3) determination of the residual connection strength and stiffness after 3.7 million and 15 million load cycles in shear parallel-to-grain and shear perpendicular-to-grain; and (4) full scale specimen testing to determine the maximum achievable level of composite action between the glulam deck and steel girder. The analytical investigation included: (1) prediction of the connection strength in shear parallel-to-grain, perpendicular-to-grain, and in direct withdrawal; (2) determination of the LRFD connection resistance for use with the LRFD design methodology; (3) design and modeling of a matrix of 60 bridges to determine the maximum force on each connector and to determine the minimum number of connectors required; (4) prediction of the composite action level between the glulam deck and steel girder for the full scale specimen using both classical mechanics analysis and finite element model (FEM) analysis; (5) construction cost comparison for six typical bridge configurations between the new connection detail and the PennDOT approved lagged offset shoe connection to confirm the economical feasibility of the connection; and (6) development of the required connection details for use with current design and construction standards for this type of construction.; The experimental results indicated that: (1) the initial 5% offset connection strength was 21.7 kip (96.5 kN), 17.0 kip (75.6 kN), and 22.2 kip (98.7 kN) for shear parallel-to-grain, shear perpendicular-to-grain, and withdrawal, respectively, with failure occurring in the epoxy grout and steel shear stud in all cases; (2) the proportional dowel bearing stress perpendicular-to-grain was 2,970 psi (20.5 MPa) and the 5 percent offset dowel bearing stress perpendicular-to-grain was 4,500 psi (31.1 MPa); (3) after 15 million load cycles the connection retained 92.8 percent and 87.7 percent of the initial 5 percent offset strength parallel-to-grain and perpendicular-to-grain, respectively; (4) the maximum achievable level of composite action between the glulam deck and steel girder was 5 percent based on system stiffness after grouting of all inter-panel joints. The analytical portion of the study indicated that: (1) accurate prediction of the connection strength was achieved using classical methods; (2) the LRFD connection strength was 25 kip (11.2 kN), 17.5 kips (78.0 kN), and 24.7 kip (110.1 kN) in shear parallel-to-grain, perpendicular-to-grain, and in withdrawal, respectively; (3) the design fatigue shear load for the connection in bridge applications was 2 kips (8.9 kN); (4) the maximum theoretical level of composite action was 13.8 percent, contrasted with the 5 percent achieved by the experimental determination and verified by the FEM using the connection data determined in the previous phases of the study resulting in a recommendation that no reliable composite action should be considered with use of this connection in bridge applications; and (5) the constructed cost of a single connection was similar to that of a lagged offset shoe connection, but overall costs are reduced because fewer connections are needed, especially in long bridge spans. Connection installation details were created allowing inclusion of the new connection into current bridge standards such as PennDOTs' BLC-560M, Low Cost Sta...