THE EFFECT OF TOLERANCES OF INDIVIDUAL STEEL COMPRESSIVE MEMBERS ON THE BEHAVIOUR OF STEELWORK STRUCTURE OF BUILDINGS

The Effect of Tolerances of Individual Steel Compressive Members on the behavior of Steelwork Structure of Buildings

The Effect of Tolerances of Individual Steel Compressive Members on the behavior of Steelwork Structure of Buildings

Introduction

Raising Steel Building Rigid Frames

The intermediate or interior frames nearest the bearing endwall are usually erected first. This bay usually contains the optional diagonal bracing. The proper completion and plumbing of this first bay, as will be discussed later, is extremely important to the successful completion of the Steel building. (Boyd, D. and Weaver, P. 2004, 54-78)

 

 Although several methods are used to erect general steel rigid frames, it has been found most satisfactory to erect the columns first, tie them together with the girts and tighten the anchor bolts*. On small spans and short eave heights, columns can often be set in place by hand without the use of hoisting equipment. Temporary bracing should always be installed as soon as sections are lifted in place. The anchor bolt tension may need to be adjusted to seat the rafter.

After the columns have been erected, the ground assembled rafter is hoisted into place and connected to the columns. The size of the rafter which can be safely handled depends on the equipment available and the experience of the erection foreman. Generally as many connections as possible are made on the ground.

The flange brace should be bolted to the rafter prior to raising in order to save time. The hoisting equipment should never be released from the rafter until the frame is adequately braced, so it cannot buckle or tip in the longitudinal direction of the building. Stay well in the clear of loads being moved by any type of lifting equipment. Safety first! (Boyd, D. and Weaver, P. 2004, 54-78)

A second method, when equipment is limited, (while not recommended) is illustrated below. After the column is erected, the first rafter section, with the lifting cable around the balance point, is raised into position and bolted to the column. Then, when the free end of the rafter is supported by any safe method (such as an adequate wood frame, or a metal scaffold, properly braced, and of satisfactory capacity) the lifting cable can be released. The procedure is then repeated until the entire frame is in place and bolted together at the ridge.

Still a third method for erecting general steel rigid frames with limited equipment adopts the same support procedure described previously, but differs in that the sidewall column and the first rafter section are bolted together on the ground and raised into position in one lift. The lifting cable is again attached at the balance point (about the quarter point of the rafter in this case). When the column is secured by the anchor bolts and the free end supported, the process is repeated with the frame bolted together at the ridge. Typically the erection manual you will receive is a ...