Strengthening of Hollow Core Slabs to Reduce Excessive Vibrations: A Case Study

Abstract

The LB Building 6 is the main logistic building of the Total Agility Logistic Co. Ltd located in Bang Phi district, Samut-Prakan province, Thailand. The building consists of a 2 storey steel structure having steel beams with a typical span of 6.0 m supported by reinforced columns. After a few months of service, cracking and spalls was found on the concrete overlay on the 2nd floor. Preliminary investigations were first performed by the building engineer and it was reported that deflections occurred at the 1-ton forklift moving path zone. Therefore, the capacity of structural elements in the building had to be re-assessed and field measurements of vibration levels were also taken during the peak operation period. To reduce the vibration level as well as deformation of the floor under normal operation, a structural strengthening intervention was made by adding additional steel beams under the hollow core slab as a span shortening technique. Field measurements have shown that the vibrations of the strengthened concrete slab reduced by up to 35% compared to the pre-strengthening measurements, thus confirming the effectiveness of the strengthening intervention. The work reported in this paper also sets the scene for identifying the major decisions for a design engineer starting from on-site inspection to the post-construction supervision.