LARSA 4D Live Load Analysis

Influence surface analysis is the latest methodology for live load analysis, which extends the notion of an influence line onto a 2D surface on plate-deck models. In LARSA 4D, both influence lines and influence surfaces are available to quickly compute the worst case loading configurations on bridge decks, including bridges with curved and skewed roadways and nonparallel curb lines.

The influence surface algorithms integrated in LARSA 4D automatically determine the transverse location of the design lanes, along with live load placement in the longitudinal direction of the design lane to maximize extreme effects. Both axle-based and wheel-based vehicle definitions that model the length and width of the vehicle can be used.

Supported Codes

LARSA 4D provides tools that can be applied to any live load design code, including AASHTO LRFD, AASHTO LFD, BS5400, and Indian Roads Congress. The vehicle load patterns for these codes come preloaded in LARSA 4D, and additional as well as custom vehicle load patterns can be entered.

Unique Features

Unique to LARSA’s live load analysis, centrifugal force factors can be specified which automatically adjust wheel magnitudes. Multiple factors can be specified to apply difference factors on the different segments within a single influence surface, and surface design lanes can include UDL without vehicle loading to promote flexibility in creating load combinations.