Study on the Design Criteria for Prestressed Concrete Pavements

With a concrete pavement slab prestressed, its load carrying capacity can be significantly increased; thus a thinner slab may be used for the same loading. Prestressing modify the structural behavior of the pavement slab and there is a greater resistance to impact, vibration and overloading. This paper discusses the major design considerations necessary in the successful construction of prestressed concrete pavements and presents a design procedure developed to predict the compressive stress due to prestressing in the pavements at early stage, during service and after cracking. Variation in the approach for repetitive and nonrepetitive loads is clearly distinguished. Check on the recovery after cracking for overloading in prestressed pavements is also needed. Finally, a design example is illustrated the application of the approach developed.

Analytical procedure for massive water-sealing barriers used in deep excavations considering seepage effect and its application

This paper presents an analytical procedure for massive water-sealing barriers(MWSBs)that are made of partially overlapped jet-grouting columns used for deep excavations,in which two crucial factors of the permeability and strength of jet-grouted materials are considered.Subsequently,a calculation example is analyzed and discussed.Results show that“tension failure”mechanism is a major concern for the structural failure during a design of MWSBs.The maximum allowable seepage discharge is a crucial index for the design of MWSBs,which has a significant influence on determining the design parameters of MWSBs.Compared with the design procedure for MWSBs that is proposed in this paper,the design parameters of MWSBs determined by the stability equilibrium and seepage stability equilibrium approaches are conservative due to the fact that it fails to consider the permeability or strength of jet-grouted materials that makes a contribution to the structural safety.Based on the proposed design method,the ranges of both the thickness and depth of MWSBs for a case history of subway excavation in Fuzhou,China were determined.Finally,field pumping test results showed that the water-tightness performance of MWSBs performed at site was quite well.

Design of controlled elastic and inelastic structures

One of the founders of structural control theory and its application in civil engineering, Professor Emeritus Tsu T. Soong, envisioned the development of the integral design of structures protected by active control devices. Most of his disciples and colleagues continuously attempted to develop procedures to achieve such integral control. In his recent papers published jointly with some of the authors of this paper, Professor Soong developed design procedures for the entire structure using a design - redesign procedure applied to elastic systems. Such a procedure was developed as an extension of other work by his disciples. This paper summarizes some recent techniques that use traditional active control algorithms to derive the most suitable （optimal, stable） control force, which could then be implemented with a combination of active, passive and semi-active devices through a simple match or more sophisticated optimal procedures. Alternative design can address the behavior of structures using Liapunov stability criteria. This paper shows a unified procedure which can be applied to both elastic and inelastic structures. Although the implementation does not always preserve the optimal criteria, it is shown that the solutions are effective and practical for design of supplemental damping, stiffness enhancement or softening, and strengthening or weakening.

The Design for R＆D Performance Auditing System

Based on the definition of R＆D pcrformance auditing system, this paper analyzes the characteristics of the system. Then it designs the components of the R＆D performance auditing system and the procedure of its establishment.

Design and Analysis of a Novel Rotor-Segmented Axial-Field Switched Reluctance Machine

As excitation strategy is influenced by the parity of phase number,and serious end effect is caused by full pitch windings adopted by the conventional rotor-segmented switched reluctance machine(RS-SRM),a novel rotor-segmented axial-field switched reluctance machine(RS-AFSRM),which adopts concentrated windings,is proposed in this paper,whose control strategy is independent of the parity of phase number.The stator of the proposed RS-AFSRM consists of inner and outer flux-conductive ring,excitation poles,and stator yoke,while the rotor consists of fan-shape cylinder-type segments.The structure and principle of the proposed machine is introduced through the magnetic circuit model of the machine.The fringing effect on air-gap field is considered.The simplified magnetic circuit considering the fringing effect is presented and the fringing effect coefficient is introduced.The design procedure considering the fringing effect through iterative modification is presented in this paper and is validated through 3D finite-element method(3D-FEM).Results show that both magnetic field distribution and operation are reasonable and satisfy the requirements.

Design Strategy of Diagonal Compressors in Compressed Air Energy Storage System

As a kind of large-scale physical energy storage,compressed air energy storage(CAES)plays an important role in the construction of more efficient energy system based on renewable energy in the future.Compared with traditional industrial compressors,the compressor of CAES has higher off-design performance requirements.From the perspective of design,it needs to pay attention not only to the performance of the design point,but also to the performance of all the stable working range.However,from the previous literature,no diagonal compressor was used in CAES which can meet the requirements,which also reflects the design program can be further improved.Therefore,this paper studies the design strategy of high efficient diagonal compressor for large-scale CAES,and gives the complete strategy algorithms used for different program modules.The pressure ratio,isentropic efficiency and stable working range are comprehensively considered.In the design process,the criteria for the key parameters of the diagonal flow angle of the diagonal compressor are given for the first time.The results show that the isentropic efficiency at the design point is 92.7%,the total pressure ratio is1.97,and the stable working range exceeds 20%,which meets the design requirements of the compressor for CAES and exceeds the overall performance of the previous compressors in the entire working range.

Design procedure for optimizing CMOS low noise operational amplifiers

This paper presents and experimentally verifies an optimized design procedure for a CMOS low noise operational amplifier. The design procedure focuses on the noise performance, which is the key requirement for low noise operational amplifiers. Based on the noise level and other specifications such as bandwidth, signal swing, slew rate, and power consumption, the device sizes and the biasing conditions are derived. In order to verify the proposed design procedure, a three-stage operational amplifier has been designed. The device parameters obtained from the proposed design procedure closely agree with the simulated results obtained by using HSPICE.

Recent developments in seismically isolated buildings in Japan

The Building Standard Law of Japan and related Enforcement Order and Notifications have been substantially revised since the year 2000 to introduce a performance-based regulatory and deregulation system for building control systems. Up to then,time-history analyses were mandatory for isolated buildings and had to be specially approved by the Minster of the Ministry of Construction (MOC).Simplified design procedures based on the equivalent linear method for seismically isolated buildings have been issued as'Notification 2009-Structnral calculation procedure for buildings with seismic isolation'from MOC,and are now integrated into the Ministry of Land,Infrastructure,and Transportation (MLIT).Along with Notification 2009,'Notification 1446 of year 2000-Standard for specifications and test methods for seismic isolation devices'was also issued.Buildings with heights equal to or less than 60m and that are designed according to these Notifications,including base isolated buildings,only need approval from local building officials,and no longer require the special approval of the Minister of MLIT.This paper summarizes:1) some statistics related to buildings with seismic isolation completed up to the end of 2001; 2) simplified design procedures required by Notification 2009 of year 2000;and 3) performance of seismic isolation devices required by Notification 1446 of year 2000.

The Layout and Simulation of Logarithmic Spiral Double Curved Arch Dam Transverse Joints

Because of its good condition with mechanics, logarithmic spiral double curve arch bam has been widely used in the practical engineering. The introduction of a new method in how to divide transverse joint in arch dam will be given and the further research of its calculation has been done. The C＋＋ is used in electronic procedure and the 3D simulation has been finished with AutoCAD, which will provide the object model for computer simulation of the arch dam and the division of finite element mesh. Meanwhile, this method in dividing the transverse joint in arch dam also can be taken as the calculated basis for the design and calculation of arch dam, construction lofting and the calculation of the work amount.

High-efficiency prediction method for helicopter global/ground noise based on near-field acoustic holography

Noise reduction program design is an effective approach that relies on efficient noise prediction for reducing ground noise during flight.The existing noise prediction methods have the limitations of being computationally expensive or only applicable to far-fields.In this paper,a High-Efficiency Prediction Method(HEPM)for helicopter global/ground noise based on near-field acoustic holography is proposed.The HEPM can predict the global noise based on acoustic modal analysis and has the advantages of high prediction accuracy and low time cost.The process is given as follows:firstly,the rotor noise on the holographic surface in the specified flight is obtained by simulations or experiments.Secondly,the global noise model,which maps time-domain noise to acoustic modes,is established based on near-field acoustic holography and Fourier acoustic analysis methods.Finally,combined with acoustic modal amplitude,the model established enables efficiently predicting the global/ground noise in the corresponding flight state.To verify the accuracy of the prediction method,a simulation study is conducted in hovering and forward flight states using a model helicopter with a 2-meter rotor and Rotor Body Interaction(ROBIN)fuselage.The comparison of HEPM with numerical results shows that the average prediction errors of the global and ground noise are less than 0.3 dB and 0.2 dB,respectively.For a region containing 100000 observers,the computation time of the HEPM is only one-fifth of that of the acoustic hemisphere method,demonstrating the rapidity of the proposed method.