CE 5310 Lecture Notes - Lecture 18: Convention Center, Ductility
HOMEWORK ASSIGNMENT
CE5310 Plastic Analysis and Design of Structures Summer 2016
Homework 7 (Due Wednesday, August 10)
Use Perform-2D for this problem.
As a structural engineer, you are consulted by a client for evaluating the collapse-prevention
capacity of an old steel building, which will be remodeled into an exhibition center. The main
seismic force resisting system is a one-story, one-bay moment frame as shown in Figure 1. The
frame members are so oriented that bending occurs about their strong axis (x-axis). According to
applicable building code, the maximum considered earthquake (MCE) force is determined as 145
kips, which can be simplified as a concentrated lateral load applied at Joint B.
(a) Typical moment-rotation relation for column and beam sections is shown in Figure 2. After
checking the original design you realize that only limited ductility detailing was done on this
old frame. Based on previous experimental testing, the corresponding deformation
parameters can be estimated as: plastic rotation (DL) = 0.005 rad.; residual plastic rotation
(DR) = 0.01 rad., when the peak strength drops to 50%. The maximum plastic rotation (DX)
= 0.15 rad. Assume all sections can reach Mp even with the limited ductility detailing.
Neglect axial load effect and second-order effect (that is: P
and Peffects). Check
the collapse-prevention capacity of this frame by performing static pushover analysis up to
3% story drift ratio. Identify the sequence and locations of plastic hinges and plot the
moment-rotation response for all plastic hinges.
(b) To ensure sufficient overall ductility, you decide to upgrade the detailing (but not changing
the member sizes) according to the current seismic provisions. The corresponding
deformation parameters then become: plastic rotation (DL) = 0.03 rad.; residual plastic
rotation (DR) = 0.1 rad.; maximum plastic rotation (DX) = 0.15 rad. The other parameters are
not altered. Redo the pushover analysis to justify the modification and discuss the difference
of overall base shear vs. drift response between frames in (a) and (b). Identify the sequence
and locations of plastic hinges and plot the moment-rotation response for all plastic hinges.
(c) In order to be a local attraction, the architect proposes using a curtain wall that adopts the
most advanced, aesthetic, and expensive glazing system for this exhibition center. This
glazing system, however, is deformation-sensitive. It has been tested and suggested by the
fabricator that the damage in the glazing system due to lateral story drift cannot be repaired if
the story drift ratio is beyond 1.3%. Check if the frame in (b) needs a new glazing system
after MCE. An alternative plan to avoid total replacement of the glazing system is increasing
beam size to obtain a stiffer frame. Redesign the beam if needed, by selecting the lightest
W14 section in the AISC Manual and justify your design.
Use rigid-plastic moment hinge as discussed in the class to model the plastic hinge in all
members. E = 29,000 ksi, Fy = 50 ksi for all members.
Document Summary
As a structural engineer, you are consulted by a client for evaluating the collapse-prevention capacity of an old steel building, which will be remodeled into an exhibition center. The main seismic force resisting system is a one-story, one-bay moment frame as shown in figure 1. The frame members are so oriented that bending occurs about their strong axis (x-axis). After checking the original design you realize that only limited ductility detailing was done on this old frame. Based on previous experimental testing, the corresponding deformation parameters can be estimated as: plastic rotation (dl) = 0. 005 rad. ; residual plastic rotation (dr) = 0. 01 rad. , when the peak strength drops to 50%. Assume all sections can reach mp even with the limited ductility detailing. Neglect axial load effect and second-order effect (that is: p and p effects). Check the collapse-prevention capacity of this frame by performing static pushover analysis up to.
