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This page is devoted to frequently asked questions (FAQ) related to bridge girders. |
Why
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must bearing properties be assigned to an integral bent cap?
Extended Question: The bearing assignments do not seem to be relevant for integral bents and abutment with integral girder support condition (the bearing property should be always fixed and the elevation does not seem to carry any useful information since there are no bearings at integral bents). How is the Why must I assign bearing properties to an integral bent cap? Since bearings should always be fixed, bearing assignment does not seem relevant to girder support conditions for integral bents and abutments. How is bearing assignment used for bents and abutments with integral-girder support conditionconditions?
Answer: A truly While a true integral bent would be is fully fixed, so the statement about irrelevant bearing assignments makes sense. However, we are allowing the option that the connection may not fixed be for all DOF. Really, what SAP2000 is doing for the integral bent/abutment is connecting the bearing to the girder top and bottom. So to define a fully integral bent, you should use fixed bearing. If you choose a different bearing, you will get different behavior that may apply in some special situations, such as when steel box cross girder is connected to superstructure girders by a shear-only connection and hence the longitudinal girders are allowed CSI software allows the connection to have free DOF. The software connects fixed bearings to the top and bottom of a girder to model fully integral bents and abutments.
Some special cases exist, however, where behavior is more closely simulated with bearings which are not fully fixed. An example may be a steel box girder connected to superstructure girders through shear-only connections. This allows longitudinal girders to rotate relative to the cross girder.The figure below shows the links utilized in modeling integral , necessitating free DOF assignment within the support condition. The links used to model an integral-girder support condition for a bridge with "Steel Girders" deck section and girders modeled by shell elements:
See also
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steel-girder deck section composed of shell elements are shown in Figure 1:
Figure 1 - Integral bent links
See Also
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