Institutionen för Bygg - Konstruktionsteknik - Lunds Tekniska Högskola

AbstractIn this thesis a bridge with main girders of steel and a bridge deck made out of glulam isstudied. The bridge is compared with an existing composite bridge built in Kalix, Sweden.Initially both bridge solutions are presented and some detail descriptions is presented for thebridge with the glulam deck. A short description of the finite element method is giventogether with the main equations for the finite element model for plates. The basics on how tobuild up a finite element model in SAP 2000 is also presented.A main goal with this report is to study how the risk for lateral torsional buckling can bereduced by using a lighter bridge deck. This is done by first deciding what kind of loads thebridge is subjected to. Then the critical lateral torsional buckling moment is calculated fordifferent spacing between the cross girders. Hand calculations are compared to a finiteelement model in SAP 2000 and the minimum number of cross girders is calculated. Theresults are then compared with a finite element model in SAP 2000. It´s also checked how therisk for lateral torsional buckling is reduced when the bridge deck is attached. This isperformed by attaching springs between main girders and bridge deck in the model in SAP2000. The springs represent screws and different stiffness is applied to these screws. Analysisis made and the total stiffness of the bridge is examined.The bridge is also checked in the serviceability state. It is shown that the vertical deflection isbigger than accepted. A suggestion to decrease the deflection is to build the bridge with asmall vertical curvature.Results from the analysis shows that the number of cross girders can be reduced by half. It isalso shown that a distance of 160 mm is required between the screws with a diameter of 12mm to achieve sufficient total stiffness of the bridge deck. This is the screws that attach themain girders to the bridge deck.In the report an overviewing economic calculation is also done. The report shows that a bigcost in the glulam alternatives is the bridge deck. However the alternatives with the glulamdeck can be built faster since there is no time for concrete hardening. This can save a lot ofmoney in labor costs.Nyckelord: Samverkansbro, vippning, finita elementanalys, SAP 2000, brottgränstillstånd,bruksgränstillstånd, skjuvbuckling, spänningskapacitet.i