The authors propose a design philosophy for steel buildings in moderate seismic regions that draws on familiar concepts of ductility and capacity design, but also integrates the concepts of reserve capacity, elastic flexibility and strength to broaden the field of design possibilities. The paper discusses structural systems representing each of these concepts: Moderate-Ductility Concentrically-...

An experimental campaign on joints of x-braced frames is presented. Tests are performed on strap-gusset joints and lower and upper corner joints. Many different phenomena and failure modes are observed in these tests. However, it is possible to see that only one failure mode can be accepted if a good seismic performance of the frame needs to be guaranteed: the net section failure of the diagona...

Residual drifts after severe earthquakes interrupt serviceability of buildings. Retrofitting of such buildings is in many cases very difficult and consumes lots of time and money. Recently, there are some attempts to develop the seismic design procedures to not only satisfy life safety criteria but also lead to more economical buildings. One of these modern methods of improving seismic performa...

Direct Displacement-Based Design (DDBD) is a performence-based seismic design method that has been proposed and well developed over the past two decades to design RC frame structures, shear walls and bridges. In this method, the behavior of a multi-degree-of-freedom (MDOF) sysytem is approximaeted by an equivalent single-degree-of-freedom (SDOF) substitute structure. Although this method has be...

The design and behavior of a ductile structural system called a knee-braced moment frame are presented in this paper. The design of this structural system is based on a capacity-design concept that results in ductile behavior. The knee part is a fuse-like component that dissipates energy by the formation of plastic flexural and/or shear hinges at its ends and mid-span, when the building is subj...

For most practical purposes, true topology optimization of a braced frame should be synchronized with its sizing. An integrated layout optimization is formulated here to simultaneously account for both member sizing and bracings’ topology in such a problem. Code-specific seismic design spectrum is applied to unify the earthquake excitation. The problem is solved for minimal structural weight un...

Abstract:   Previous research on bracing members show that the ductility of bracing members is compromised due to the buckling phenomena. Therefore, many researchers have tried to use special considerations to increase the fracture life of bracing members. Some of these recommendations such as increasing the slenderness ratio, using lower width to thickness ratio, increasing the out-of-p...

Passively damped bracing systems in steel frames, in which the conventional materials of the joint are replaced by high damping viscoelastic materials, have the potential of being effective practical means for passive vibration control of dynamically loaded civil engineering structures. However, this potential can be realized only if the associated structural penalties are reduced within accept...