# COMPARATIVE INVESTIGATIONS OF DESIGN TRAFFIC LOADS FOR ROADS BRIDGES AND THE DERIVATION OF AN IMPROVED LOAD PATTERN

## VERGLEICHENDE UNTERSUCHUNGEN VON VERKEHRSREGELLASTEN FUER STRABENBRUCKEN UND ABLEITUNG EINES VERBESSERTEN LATBILDES

The aim of this work is to determine for bos-girder and T-beam cross-sections of bridge constructions the stresses due to solar radiation and varying air temperature as well as roadway heating, taking into account the residual stresses resulting from the nonlinear temperature development. These results are intended to be used for investigating in how far damage to prestressed concrete bridges can be ascribed to stress due to temperature, and whether the stresses resulting from roadway heating exceed those due to the influence of the weather. The temperature field is calculated with the Fourire differential equation for heat conduction transformed into a difference equation. The stress distribution is then determined on the assumption that the stresses due to the unsteady temperature field in the individual directions are independent of one another and that the cross-sections remain plane in the case of deformation. Temperature measurements performed on a bridge with a box-girder cross-section in cooperation with the Road and Bridge Construction Office of the City of Frankfurt serve as controls. The measurements were almost identical with the calculated figures. By means of the calculation process the temperature field and the stress distribution caused, on the one hand, by the weather conditions in summer and, on the other hand, by roadway heating in winter, were calculated for 13 existing bridges--7 with box-girder cross-section and 6 with T-beam cross-section. The results show that the stresses due to roadway heating are smaller than those due to the influence of the weather. Consequently, only the stresses due to the influence of the weather need be demonstrated. In the longitudinal direction, the timperature differences in the examples calculated are of the order of +5 deg C, the residual tensile stresses amount to about 10 kgf/sq cm, and the residual compressive stresses may reach 20-30 kgf/sq cm. In the transverse direction, in the case of box-girder cross-sections, the temperature differences determined for state I may amount to 3 deg to 14 deg C, depending on the incidence of the radiation. /Author/

• Availability:
• Corporate Authors:

Bundesminister fuer Verkehr

ABT. Strassenbau, Lennestrasse 30
D-5300 Bonn,   Germany
• Publication Date: 1977-8

## Filing Info

• Accession Number: 00168389
• Record Type: Publication
• Report/Paper Numbers: Report 212-1976
• Files: TRIS
• Created Date: Feb 16 1978 12:00AM