Kiyoshi Aida

Evaluation of aseismic reliability of actual boiler structures and a study on design of seismic ties based on proof tests using a large scaled shaking table

This paper deals with the evaluation of aseismic reliability of actual boiler plant structures in conjunction with seismic ties, installed between the boiler and the support structures. Proof tests were conducted with a coupled model using a large-scale shake table which verified that the ties acted as energy-absorbing devices against severe earthquakes. Since recent boiler structures are designed based on dynamic response analysis considering the boiler-structure interaction and the effect of energy dissipation of the ties, it is necessary to verify the accuracy of simulation methods. In view of this, the numerical models of the ties are discussed in post analysis. As a result of the post analysis, it is confirmed that (1) seismic ties of existing boiler plants designed by dynamic analysis provide sufficient durability, and (2) the support structures designed by conventional methods have enough aseismic reliability.

Earthquake Load Reduction Effects of Boiler Structures by High Energy Absorbing Seismic Ties

Seismic ties are steel energy absorbing devices installed between the boiler and its support structure. This paper deals with the relationship between the energy absorption of a new type of seismic tie (made of low yield strength steel and with an optimized I-sectional shape) and its reduction effect on the resultant shear force of the support structure. To quantify the relationship between the energy absorption and the reduction effect on the resultant shear force, time-history analyses using a lumped mass vibration model that simulates the boiler structure, were performed for three representative design seismic waves (The largest class (level 2) waves of Taft, El Centro and Hachinohe earthquakes). The time-history analysis results demonstrated that the energy absorption increasing rates of the new seismic ties were correlated quantitatively with the shear force reduction rates of the support structure for the three design seismic waves.Copyright

Development of High Energy Absorbing Seismic Tie With I-Sectional Shape for Thermal Power Boiler Structure

This paper deals with new types of steel seismic ties, which are energy absorbing devices installed between boiler and its support structure. To enhance the aseismic reliability of the boiler and its support structure, energy absorbing capacities of the seismic ties must be increased. To increase the capacities, sectional shapes of the seismic ties have been optimally designed. Concretely, I-section seismic ties as new types have been gained by optimizing the design parameters, material (conventional carbon steel and low yield strength steel), sectional height, web thickness, flange thickness under conditions to maximize absorbing energy and to restrict the reaction force equal to or smaller than that of round-section current seismic tie. As a result of cyclic load testing using 1/3 scale model, it was verified that energy absorption of the new types of seismic ties were 16–23 % larger than that of the current seismic tie.Copyright