Distress in Prestressed Concrete Roof Girders at Cement Plant

An investigation was made into the causes of the collapse of one prestressed concrete roof girder and the cracking of many others at a cement plant. Visual inspection, measurement of cracking and deflection, assessment of in situ strength and design calculations were employed in the appraisal. Overloading of the roof with cement dust was identified as the most probable cause of the failure, although instability arising out of wind uplift may also have been a possibility. The remedial measures proposed for the remaining cracked girders included removal of cement dust and maintenance of the roof in a dust‐free condition, epoxy grouting of existing cracks, provision of externally bonded steel plates for the strengthening of specified panels against shear failure, ensuring proper connection of purlins to girders and the provision of adequate longitudinal bracing for the structure at roof level. A reflection on the causes of failure indicated that misuse during the operational phase was at fault; however, it is argued that a change in design philosophy may have prevented catastrophic collapse.