Yuki TERAZAWA

Abstract This paper presents a damper design strategy for highly indeterminate 3D structures utilizing computational optimization and generalized response spectrum analysis, which is extended to incorporate non‐proportional damping. This enables a more efficient design process compared to trial‐and‐error with nonlinear response history analysis. The efficiency of the proposed design strategy is verified, analyzed and then applied to a series of illustrative examples including retrofit of an exis

The damped outrigger system is in widespread use as a damping modification system for tall buildings that provides high additional damping in addition to the bending back effect against the core. However, while the enhanced seismic performance of damped outrigger systems was confirmed in previous studies all over the world, a general-purpose optimal design method focusing on modal damping ratios has not been established yet. This paper proposes an optimal damper design kit composed of a first mo

In this study, a computational seismic design routine is proposed based on a generalized response spectrum analysis for highly indeterminate structures with energy‐dissipation members, such as viscous or elasto‐plastic dampers. Complex stiffness terms are introduced to account for displacement‐dependent damping, and a three‐dimensional (3‐D) element stiffness matrix with complex axial stiffness is proposed for elasto‐plastic dampers. A modified complete quadratic combination method previously de

Seismic isolation is widely used in seismic areas of the world for their functions of securing both of human life and the property. While simple design methods for simple structures have been proposed by many researchers, these methods are generally limited to specific seismically isolated structural systems. Particularly in Japan, the number of challenging structural systems (e.g. a base isolation with tall buildings, mid-story isolation or roof isolation systems having substructures with dampe

In steel roof gymnasiums with RC substructures, out-of-plane response of Cantilevered RC walls are predominant during seismic responses, which triggers sequential damages of structural or non-structural components. Particularly, in 2016 Kumamoto earthquake, structural damages related to space frames (i.e. member buckling, member local buckling, post-buckling ductile fracture and connection bolt fracture) were reported, which is the newly observed damage characteristic. Space frames are generally

The outrigger system incorporating dampers between the outrigger truss and perimeter column can significantly reduce dynamic response compared with the conventional one, and is becoming the most popular structural system for tall buildings in seismic regions except for Japan. While Smith and Willford who are the proposers of this damped outrigger system recommend to confirm the modal damping ratio in the design, there are few proposal of optimal design strategy based on the modal damping ratio.

Summary The damped outrigger system is known to efficiently provide additional damping in buildings with heights of over 250 m. However, particularly for supertall buildings in the center of Tokyo, Japan, the outrigger truss from the center core to the exterior columns need to span distances of more than 20 m. This increases the flexural stiffness demand on the outrigger that leads to larger truss depths making the damped outrigger system inefficient. For such tall buildings with large plans, a

The damped outrigger system is in widespread in seismic area as a damping modification system. However, the relationships between the exact damping performance and its seismic response reduction effect has not been deeply investigated yet. This paper investigated the non-linear dynamic response characteristic of single-damped outrigger systems with oil dampers or elasto-plastic dampers considering design earthquake levels. The optimal damper design equations to maximize 1st mode damping ratio we

1. Introduction Numerous structures are recently required continuous use even after large earthquakes. An efficient technique is to employ elasto-plastic dampers, such as buckling-restrained braces (BRBs), which act as fuses. Although response spectrum analysis (RSA) has a good time efficiency for damper design, relative to non-linear response history analysis (NLRHA), the conventional methods are generally limited to specific structures that are easily translated into simple models. With a suit

This paper presents design recommendations for optimal seismic response control of damped braced tube system with focus on cost performance of introducing energy-dissipation devices. According to the results, 1) braced tube structure should be designed so that coupled-shear-wall-like vibration modes are predominant to obtain highly damping ratio and better cost performance of dampers, 2) oil damper should be introduced to obtain highly damping ratio, 3) BRB has good cost performance about seismi

This paper presents a design application of the proposed generalized response spectrum analysis (GRSA)-based seismic optimization method to a large metal spatial structure (constructed in Japan) where a rigid diaphragm assumption is not available and displacement responses are disproportionally distributed in a story. It also discusses the optimal mixed placement and capacity distribution of buckling-restrained braces (BRBs) and conventional braces (CBs) to minimize both the story drift response

Structural morphogenesis is widely used as a parametric tool to find an optimal structural shape of shell structures for a prescribed objective function and a given design load. However, the current optimization methods are limited to finding a geometry under only a specific static load like the dead load or an equivalent static seismic load for predefined geometrical shapes, and so can not be applied to free-form gridshells. This poses a challenge to achieving an efficient free-form shell struc

This paper investigated the dynamic response characteristic with focus on damped slit configuration of damped braced tube systems with oil dampers. According to the results, 1) damped braced tube system has over 10% 1st to 3rd damping ratio, 2) while the displacement and acceleration responses are simultaneously reduced up to maximized 1st mode damping ratio, the acceleration reduction effect may be getting worse after the peak, 3) while uniform damper distribution contributes to better damping

A series of modal response spectrum analyses were performed on 60m to 150m spanned lattice domes with the half subtended angle ranging from 20 deg. to 30 deg. to investigate the effect of the dynamic characteristics of the substructure’s higher mode. It was found that the current equivalent static seismic loads underestimate the roof response when supported by multi-story substructure with the 1st natural period in the range of 0.5s to 1.2s. Therefore, a modified equivalent static seismic load c

It is concerned that a long-duration earthquake in the future generates fatigue fractures in the steel structural components. The authors have investigated the member fracture of axial members including cold-formed circular hollow sections. According to previous study of steel braced frames, it’s suggested that more ductile structural components should be applied to a steel structure achieving higher seismic performance. On the other hand, it is needed to develop an aseismic design method of a s