E load combination ab is when lanes a and b both

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a traffic load (i.e. load combination AB is when lanes A and B both carry traffic). The reaction numbers coencide with numbering system in Figure 4-5 where reaction 1 is at the far left bearing point on the pier, reaction 2 is at the 2 nd from the left bearing point, etc. These reactions where multiplied by A 6.43 -173.11 -82.15 14.51 -2.40 B -2.96 17.91 -131.30 -131.34 10.97 C 0.69 -4.17 16.90 -84.74 -165.40 AB 3.47 -155.20 -213.46 -116.83 8.57 AC 7.12 -177.28 -65.25 -70.23 -167.80 BC -2.27 13.74 -114.40 -216.08 -154.43 ABC 4.16 -159.37 -196.55 -201.57 -156.83 Reaction 2 (kips) Reaction 3 (kips) Reaction 4 (kips) Reaction 5 (kips) Load Combination Reaction 1 (kips)
34 AASHTO multiple presence factors and the resulting bearing rections are shown in Table 4-6. The factors of 1.20, 1.00 and 0.85 relate the probability of one, two or three lanes being loaded simultaneasly. Table 4-6 Vehicle Live Load Multiple Presence Factors x Bearing Reactions Bridge Pier Total Bearing loads Table 4-7 AASHTO Load Factors AASHTO load factors in table 4-7 were used to calculate the total factored girder reactions acting at each bearing point of the pier cap. The total factored loads are in table 4-8 and were calculated as follows: Total Load = 1.25(DC)+1.5(DW)+1.75(LL) Example: The total load at bearing point 1 for load combination A+DC+DW is the combination of Reaction 1 for live load in lane A and the DC and DW dead loads for an exterior girder. Total Load = 1.25(-253.70)+1.5(-39.20)+1.75(7.72) = -362.42 kips A 1.20 7.72 -207.73 -98.58 17.41 -2.88 B 1.20 -3.55 21.50 -157.56 -157.60 13.16 C 1.20 0.83 -5.01 20.28 -101.69 -198.48 AB 1.00 3.47 -155.20 -213.46 -116.83 8.57 AC 1.00 7.12 -177.28 -65.25 -70.23 -167.80 BC 1.00 -2.27 13.74 -114.40 -216.08 -154.43 ABC 0.85 3.54 -135.46 -167.07 -171.33 -133.31 Reaction 2 (kips) Reaction 3 (kips) Reaction 4 (kips) Reaction 5 (kips) Load Combination Multiple Presence Factor, m Reaction 1 (kips) Load Case Load Factors Superstructure DL 1.25 Wearing surface DL 1.5 Vehicle LL 1.75
35 Table 4-8 Bridge Pier Bearing Loads Figure 4-6 Bearing Load Locations The load combination producing the maximum moment at the column is used for the design of the bridge pier. Shear and moment values at these locations are shown in Table 4-9 and are calculated according to Figure 4-7 which shows the pier idealized as a frame. Combinations include the factored level live loads for each load case and the factored dead loads acting on each bearing point. The governing load combination is BC+DC+DW which refers to the lanes B and C having traffic live load, the dead weight of the superstructure (DC) and the dead weight of the wearing surface (DW). The loads used from this combination are Load 4 = -773.31kips and Load 5= -646.18kips. This produced a shear value of 1289.29 kips and a moment of 19259.70 kip-ft. To keep the design of the pier cap symettrical and due to uncertainty in the possible location of the traffic lanes, Load 1= Load 5 and Load 2 = Load 4. Load 3 is taken as the maximum reaction at bearing point 3 which is -762.72kips. The final loading at each bearing point of the pier cap is shown in Table 4-10 and the location of these loads is shown in Figure 4-6. Load 1 Load 2 Load 3 Load 4 Load 5 (kips) (kips) (kips) (kips) (kips) A + DC + DW -362.42 -758.70 -567.70 -364.71 -380.96 B + DC + DW -382.15 -357.56 -670.91 -670.98 -352.90 C + DC + DW -374.48 -403.94 -359.68 -573.13 -723.26 AB + DC + DW -369.85 -666.77 -768.72 -599.63 -360.93 AC + DC + DW -363.46 -705.42 -509.36 -518.08 -669.57 BC + DC + DW -379.90 -371.13 -595.37 -773.31 -646.18 ABC + DC + DW -369.73 -632.24 -687.55 -695.01 -609.21 Load Combination
36 Shear 1 Moment 1 Shear 2 Moment 2 (kips) (kips·ft.)

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