Ultimate capacity of steel angles subjected to eccentric compressive load

Abstract

Steel angles have a wide range of structural applications requiring a comprehensive design methodology. Steel angles, although used universally, such as in lattice microwave towers and transmission towers have not received a comparable attention for various reasons. The behavior of angles is different to some extent from that of other commonly used steel shapes because they are unsymmetric sections and are usually attached to other members by one leg only resulting the load to be applied eccentrically. Eccentrically loaded single steel angles are one of the most difficult structural members to analyze and design. They are prone to failure modes that are not usually associated with other steel shapes. The ultimate compressive load carrying capacity of single steel angles subjected to eccentrically applied axial load is investigated in this project as part of a three dimensional truss. In this thesis, a previously conducted experimental study is simulated. A finite element study was conducted to properly understand the complex load carrying behavior of single angles. Account is taken of member eccentricity, local deformation as well as material and geometric non-linearity. Results are then compared with experimental records and with those found by means of internationally adopted standard codes. It is demonstrated that the finite element model closely predicted the experimental ultimate loads and the behavior of steel angles. Hence, finite element analysis of structures composed of single angles may be an easy alternative to physical testing of these structures. From the present study it has been observed that only the ASCE Standard 10-97 predicts angle capacity to a reasonable extent when compared to both FE analyses and experimental results. Generally, AISC, BS and IS Codes underestimate the capacity while AASHTO and CRC Formulas overpredict the capacity. It is therefore recommended that in the design of three-dimensional trusses and lattice towers, the provisions of ASCE Standard 10-97 should be followed.