Continuous‐Beam Analysis for Highway Bridges

Continuous‐beam bridges may be analyzed in a very concise manner for situations of constant‐flexural stiffness (EI), symmetrical structures with interior spans of equal length. When load is applied to only one span, all end moments may be directly determined from simple calculations using coefficients derived on the basis of the compatibility of joint rotations, without iteration or simultaneous equations. Results from multiple loads in several spans may then be obtained by superposition. Closed‐form expressions are presented herein for end moments in continuous beams with three or four spans followed by a presentation of the general formulation for any number of spans, which provides an efficient algorithm suitable for interactive microcomputer usage. Practical applications of the method are illustrated by providing closed‐form expressions for bending moments caused by both dead load and lane load in continuous‐beam highway bridges, and by suggesting a simple procedure for treating as a single unit the several concentrated loads from a bridge‐design vehicle. The technique can easily be customized to suit the needs of individual designers.