Structural Engineering

Structural Engineering Case Synopsis

Case Synopsis: In 2002, an examination of a two-story mid-19th century brick building was conducted and nothing was found regarding any dynamic disturbance to the building. The front wall at that time had bulged outward and star bolting was specified. Three stars were installed at the first floor ceiling level. An engineering report noted no instances of any cracks or any bulging of the rear wall, or any damage whereby the doors did not close or any racking or cracking within the interior was found. In 2008, another engineer visited the property and provided a survey of the general structural conditions. On the right side of the party wall of the building he noted that the contractor working at the adjacent house removed the rear wall of that house and broke the bond between the rear-wall at the right side party wall. This caused the rear wall to bow outward and lean out toward the rear of the property because this was an unsupported 8-inch thick wall for two-stories.

Engineering Analysis: Upon being retained, a new visit was conducted, and it was noted that shoring had been provided to the bulged rearward leaning wall. Work that was done at the adjacent property had turned what was a structurally sound and stable structure into an unstable one. The wall had moved outward by a distance of 1½-inches to 3-inches, which would not have occurred if the property walls were bonded together. Also, the floor in the basement of this property had moved outward in an easterly direction by 1½-inches due to an improper underpinning procedure resulting in cracks. This caused settlement of the easterly wall, sloping of the joists and diagonal cracking at the second-floor rear, whose directionality is toward the front of the house.

Defendants’ engineers stated that the occupied house was originally defective and that the damage was not caused by the demolition operations. Upon examination, it was apparent that a sledge hammer was used, rather than saw cutting, to cut the rear wall of the house that was demolished and thus, by the dynamic actions, had removed any keying action of the brick and removed any tie material. Instead of installing a bolting procedure to tie the wall together, they had done nothing, and the wall had bulged outward now approaching 3-inches.

Conclusion: Engineering analysis revealed that the 8-inch thick brick was not properly restrained and free to move leading to buckling. The allowable height for an 8-inch thick masonry wall is 13-feet, which is 20-times its thickness thus, corroborating the conditions that were found. Sledgehammer blows and breaking of the bond between the party wall and the rear wall, shown in photographs, led to the conditions that have occurred. The failure of the contractor to pin the wall together led to the racking of the rear exit door and the bulging of the rear wall of the building. Additionally, the poor underpinning at the east side has caused the floors to slope within the interior of this building. All damage that was seen within this building could be traced to recent operations and the construction of the new house to the east.

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