Lane Supports (Negative Moments at Interior Piers) 





Assign the elements constituting a multiple span being considered for moving load analysis using traffic lane loads. When a support is defined by the function, midas Civil automatically places concentrated loads of equivalent magnitudes to the uniformly distributed loads on the spans each side of the support in addition to the uniformly distributed loads. The concentrated loads are located so as to produce the maximum negative moment due to the traffic lane loads in accordance with the AASHTO Standard, AASHTO LRFD and PennDOT. AASHTO LRFD Design Load This function also automatically considers the requirement of the effect of 90% of two design trucks spaced at 50 ft and 90% of the design lane load for negative moment in accordance with AASHTO LRFD when specified. The requirement of 14 ft distance between the 32 kip axles is also maintained. PennDOT Design Load (PHL93TRK) This function considers the Pennsylvania DOT requirements. For the negative moment between points of dead load contraflexure, the effect of two design trucks spaced a minimum of 50 ft. between the lead axle of one truck and the rear axle of the other truck, combined with the effect of the design lane load; the distance between the 32 kips axles of each truck shall be taken as 14 ft.. The two design trucks are placed in adjacent spans to produce maximum force effects. (PUB 15M (512) 3.6.1.3.1.) PennDOT Tandem Load (PHL93TDM) For the negative moment between points of dead load contraflexure, the effect of two tandems with axle weights of 25 kips spaced from 26 ft. to 40 ft. apart, combined with the effect of the design lane load. The two tandems should be placed in adjacent spans to produce maximum force effects. (PUB 15M (512) 3.6.1.3.1.) AASHTO legal load (The Manual for Bridge Evaluation) This function also automatically considers the requirement of the effect of a lane load of 0.2 klf combined with two AASHTO Type33 vehicles or state legal loads multiplied by 0.75 spaced at 30 ft for negative moment in accordance with the Manual for Bridge Evaluation by AASHTO . In addition, for span lengths greater than 200ft, critical load effects shall be created by the AASHTO Type33 vehicles or state legal loads multiplied by 0.75 and combined with a lane load of 0.2klf. Each State DOT legal load This function also automatically considers the requirement of the effect of a lane load of 0.2 klf combined with two state legal loads multiplied by 0.75 spaced at 30 ft for negative moment in accordance with DOT Legal vehicles when specified using the LRFR method. In addition, for span lengths greater than 200ft, critical load effects shall be created by the state legal loads multiplied by 0.75 and combined with a lane load of 0.2klf.








From the Main Menu select Load > Moving Load > Lane Supports  Negative Moments at Interior Piers. 







