Volume 28, Issue 6 (November 2000)
Assessment of Misalignments in Some Selected Buildings in Jordan and Their Structural Effects
A field survey was performed to assess horizontal and vertical misalignments and their structural effects in some selected buildings in Irbid City, Jordan. Fifty-two building units were selected as representative of the construction practice of residential buildings in Jordan after the Gulf War during the nineties. Buildings in the inventory were low-rise with one to four stories above ground. Story height ranged typically from 2.80 to 3.30 m. Field measurements for misalignments in the exterior elements of twentyone buildings were collected. Twelve of these buildings have concrete-backed stone masonry walls that serve as bearing walls, and nine buildings have skeletons which serve as reinforced concrete frames in-filled with hollow concrete blocks. Also, field measurements for misalignments in the interior elements of thirty-one buildings with skeletons of reinforced concrete frames filled in with hollow concrete blocks have been collected using the concept of the intersection algorithm.
Average values of measured misalignments for every type of construction are compared with the tolerances according to the Jordanian Standards, General Technical Specifications for Buildings, and ACI Standards. All measured misalignments exceed the tolerances in both standards except for the vertical alignment of the interior reinforced concrete frames filled in with hollow concrete blocks. The maximum values for the ratio between the measured misalignments and the tolerances were in the exterior concretebacked stone masonry walls, which reached 31.5 for the horizontal misalignment, and 3.4 for the vertical misalignment, according to the Jordanian Code. The reason for the different ratios between the interior and the exterior misalignments is due to more difficult environmental conditions for outside construction compared with inside construction. The value 3.4 for vertical misalignment compared with 31.5 for horizontal misalignment reflects the importance of using checking and surveying equipment (such as level and plumb) for every stone course (25 cm height), while lines and other checking equipment are used for horizontal distances which range between 12 and 15 m.
Moreover, misalignment sensitivity analysis was carried out for a typical reinforced concrete frame, which consisted of three spans continuous beam and four-story height, for the purpose of studying its effect on the static actions in the plane frame. Results indicated that horizontal misalignments have negligible effect on the static actions, however, vertical misalignment starts to have an effect at a value of 2.5% (e.g., at 3% vertical misalignment and 2.5% horizontal misalignment the required ratio of steel in the column has increased from 0.0100 to 0.0219).