Page 322 - Advanced Design Examples of Seismic Retrofit of Structures

Example of a Steel Frame Building Retrofitted Chapter 5 311

displacements. Primary and secondary component demands shall be within the
acceptance criteria for nonlinear components at the selected structural perfor-
mance level. Modeling parameters and acceptance criteria for nonlinear
procedures—structural steel components are illustrated in Table 5.12.

Beams
Flexural actions of beams shall be considered deformation controlled. Permis-
sible plastic rotation deformation shall be as indicated in Table 5.12.

Columns
Flexural loading of columns, with axial loads at the target displacement
less than 50% of P CL shall be considered deformation controlled, and maximum
permissible plastic rotation demands on columns, in radians, shall be as indi-
cated in Table 5.12, dependent on the axial load present and the compactness
of the section. As an example, the plastic hinge characteristics of the columns
and braces of the sports building are presented in Tables 5.13 and 5.14,
respectively.

5.7.2.2 Force-Controlled Actions
Primary and secondary components shall have lower-bound strengths not less
than the maximum analysis forces. Lower-bound strengths shall be determined
considering all coexisting forces and deformations.

Columns
Axial compressive loading of columns shall be considered force controlled.
Flexural loading of columns, with axial loads at the target displacement
greater than or equal to 50% of P CL , shall be considered force controlled and
shall conform to Eq. (5.31).

5.8 RESULTS
5.8.1 Beams With Cradle-Type Connections

The results of a typical beam with cradle-type connection are shown in Fig.
5.11. Based on these results for all the beams with cradle-type connection pre-
sented in Table 5.15, the vulnerability of the beams is determined.
The loading and hand calculations of the beams in cradle-type connections is
as follows.