We present a model to simulate the increase in sludge temperature during batch-type thermal pretreatment of sewage sludge. The semi-theoretical model is based on energy balance as a function of operating conditions, including non-ideal factors determined by fitting. The model was verified by comparison with the results of bench-scale runs. It predicted the relationship between the operating conditions and steam input with sufficient accuracy. The test plant needed more energy input than the ideal during operation owing to the influence of the heat capacity of the apparatus. To optimize the scale of the apparatus, we simulated the treatment of 10 t of sludge. The energy input was minimized with 10 runs of a 1-t apparatus if the heat capacity of the ancillary apparatus exceeds a certain threshold, and 5 runs with a 2-t apparatus if the heat capacity is below the threshold. The influence of the boiler's performance on energy input is small, but its effect on the heat-up rate of the sludge is large. A boiler with sufficient equivalent evaporation and rated pressure will shorten the operating time.

Seismic isolation can provide superior building safety and dynamic response during strong earthquakes, however, performance is only assured below the design earthquake intensity level. This paper opens with a study of observed strong, near-source ground motions and long-period earthquake waves proposed by researchers. Through the examination of a widerange of earthquake response and input energy spectra, up to a period of 100 seconds, the most suitable range of damping values and isolation periods are found. The optimal period range is further confirmed by evaluating earthquake-wave amplification features during propagation from bedrock to the ground surface. Three types of next-generation seismic isolation systems are proposed along with new parameters to evaluate the dynamic response of seismically isolated structures. By comparing the dynamic response performance of four isolation systems, including a "conventional" 4-second period system, the superior seismic performance of the three next-generation isolation systems is confirmed. The paper shows the direction for a new generation of seismically isolated structures, with periods exceeding 10 seconds, and which minimize the elastic strain energy stored in the structure. Seismically isolated structures possessing these properties will survive strong earthquake input regardless of the uncertainty inherent in earthquake ground motions.

No abstract

Since the safety of seismically-isolated buildings during earthquakes depends mainly on the largedeformation stability of the isolation devices, it is necessary to either provide large isolator deformation capacity or to reduce seismic response deformation to ensure enhanced building safety. From the viewpoint of earthquake demand, it must be recognized that, the isolator response deformation may exceed the allowable capacity when the isolation system resonates with strong, near-source earthquake ground motions. This paper first establishes the problem of the damping capacity of conventional isolation systems that a system with strong restoration spring causes large elastic strain energy to accumulate in largely deformed isolators. Then, a new hysteresis behavior is proposed to reduce the strain energy developed in isolators. Based on studies of the fundamental characteristics of the proposed hysteresis behavior, this paper proposes a new isolation system concept called “Seismic Isolation with No Strain Energy (NSE)” which does not result in resonance because it eliminates the strain energy stored in deformed isolators, even if the period of the isolation system coincides with predominant period of the input ground motions. The superior performance of NSE Seismic Isolation is confirmed by the results of dynamic response analyses for strong, near-source earthquake ground motions.

In the design and analysis of seismically-isolated structures, it is assumed that the ground is always horizontal during earthquake ground shaking. But a previous paper [3] found that ground inclination may reach to 1/1000∼1/100 (rad) during earthquake shaking, and that the horizontal displacements of isolated structuresmay be significantly affected by the static ground inclination. This paper investigates how the displacement of isolated structures may be increased by dynamic ground inclination during earthquake shaking. Since no time-histories of ground inclination exist, this paper assumes two different conditions for ground inclination motions : sine-wave motions, and displacement time-history inputs with the same phasing as vertical displacement waves. In the case of assumed sinewave motions, the increased displacement of an isolated structure due to dynamic ground inclination can be predicted by considering two factors: the basic increase displacement and the resonance amplification ratio of the isolation period to the dynamic ground inclination period. When displacement time-history waves are considered, the upper limit of displacement increase can be predicted by the isolation period and the longest period of the ground inclination motion.