Iron and steel structural components
Editor's note: This story is adapted from the U.S. Department of Housing and Urban Development's Residential Rehabilitation Inspection Guide, 2000.Click here for other stories in this series.
Parts of this story: Introduction ~~ Seismic and wind resistance ~~Cracking and deterioration of masonry, general issues ~~Masonry foundations & piers~~Above ground masonry walls ~~Chimneys ~~Wood structural components ~~ Iron and steel structural components ~~Concrete structural components
|Failure of a concrete lintel and sill due to differential settlement of the building. Permanent repairs will be quite expensive. Note the makeshift shoring of the lintel.|
Metal structural components used in small residential buildings are usually limited to beams and pipe columns in basements, angles over small masonry openings, and beams over long spans elsewhere in the structure. These components are almost always made of steel, although in buildings erected before 1890 to 1900 they may be of cast or wrought iron. While cast iron is weaker in tension than steel, when found in small buildings it is rarely of insufficient strength unless it is deteriorated or damaged.
Joist notching and drilling criteria
Problems with iron and steel structural components usually center on corrosion. Inspect them as follows:
- Lintels and other embedded metal components in exterior masonry walls can corrode and in time become severely weakened themselves. Rain and snow often contain carbonic, sulfuric, nitric, or hydrochloric acid that lowers the pH of rain water, thereby accelerating corrosion. Check all embedded iron and steel to determine its condition. Make sure lintels have adequate bearing. Corrosion can also displace surrounding masonry.
- Columns should be checked for adequate connections at their base and top, and for corrosion at their base if they rest at ground level. Eccentric (off-center) loading or noticeable tilting of columns should be remedied.
- Beams should be checked for bearing, adequate connections to the structure, and deflection. Bearing can be significantly reduced on pilasters, piers, or columns in differentially settled buildings; inspect such conditions carefully. Beams in small residential buildings rarely deflect. If deflection is found, however, the cause should be determined and supplemental supports or plates should be added to correct the problem.
- Fire damage to iron and steel structural components should be carefully inspected. Iron and steel rapidly lose their load-bearing capacity when exposed to fire and will under-go considerable expansion and distortion. In general, a structural iron or steel member that remains in place with negligible or minor distortions to its web, flanges, or end connections should be considered serviceable. Sagging or bent members, or those with a loss in bearing capacity should be replaced or reinforced with supplemental plates.
When the quality or composition of an iron or steel structural component is in doubt, a small sample of the metal (called a coupon) may be removed from a structurally unimportant location and sent to a testing laboratory for evaluation. The sample should be tested in accordance with ASTM E8, Standard Test Methods for Tension Testing of Metallic Materials, and ASTM E9, Standard Test Methods of Compression Testing of Metallic Materials at Room Temperature. Such work should be performed under the auspices of a structural engineer.
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