專業(yè)英語(雷擊鋼筋混凝土結(jié)構(gòu)時電磁環(huán)境的時域有限差分分析)剖析

1、Finite-Difference Time-Domain Analysis of the Electromagnetic Environment in a Reinforced Concrete Structure When Struck by Lightning 指導(dǎo)老師：XXX老師學(xué) 生：XXX 日 期：2016.06.15Vocabulary finite-difference time-domain (FDTD) reinforced concrete structure ring conductor electromagnetic radiated red,et method of

2、 moment the impulse response Vertical column klm oscillation ,slen superimpose,suprmpoz Faraday cage grounding conductor Lightning Protection Zone(LPZ) Shielding grid-like spatial empirical formulas compatibility impedance 有限差分 鋼筋混凝土結(jié)構(gòu)環(huán)導(dǎo)體電磁的輻射的矩量法脈沖響應(yīng)垂直列振蕩重疊法拉第籠接地導(dǎo)體防雷區(qū)屏蔽的柵格空間經(jīng)驗公式兼容性阻抗Vocabulary matr

3、ix potential coupled transient surge current quasi-static permittivity narrow-pulse current electrode exponential amperempe(r) spectrum spektrm filtering self-inductance mutual inductance conductivity perpendicular configuration mitigate longitudinal ,lndtudnl horizontal uneven adjacent des()nt 矩陣電勢

4、耦合的暫態(tài)的；瞬時的沖擊電流準(zhǔn)靜態(tài)的介電常數(shù)窄脈沖電流電極指數(shù)的安培頻譜濾波自感互感電導(dǎo)率垂直的配置減輕縱向的水平的不均勻的鄰近的AbstractWhen a building is directly struck by lightning, the electromagnetic environment in the structure is very severe, and the conducted and radiated electromagnetic disturbances are dangerous to the information technology equipment

5、 in the building. Furthermore, the role of a ring conductor to stabilize its interior electromagnetic field is discussed in detail.Besides a reasonable concordance between the calculation results of current distribution among the vertical columns and those of former experiments, the oscillations sup

6、erimposed on the current flowing along the reinforced bars, and the relation between the oscillation intensity and the soil conductivity are discussed.In this paper, instead of the equivalent circuit method and method of moment used by the former researchers, the finite-difference time-domain method

7、 is applied to calculate the impulse response in a reinforced steel structure struck by lightning.otlinethe equivalent circuit methodThe finite-difference time-domain(FDTD)methodthe frequency domain based on the method of moment(MoM)Calculations and experiments of the transient electromagnetic distr

8、ibution within a structure under a lightning impulse have been conducted in many papers.1.Introduction（1）To demonstrate the validity of FDTD method applied to calculate lightning electromagnetic responses in a reinforced concrete structure,the current distribution among the vertical columns is calcu

9、lated,and the calculation results are compared with the results of earlier experiments.（2）To investigate the induced oscillation in the steel structure,a relative narrow pulse current source is injected,the soil conductivity is set as three different values,and the time-domain oscillation waveform o

10、f current along steel bar is calculated and discussed.（3）To investigate the role of a conductively closed ring conductor to stabilize the interior electromagnetic field,the magnetic field in the same area when encircled and not encircled by a ring conductor is calculated and compared.These research

11、works are expected to be useful for the EMC design of a building.2.Calculation modelFig. 1 Scheme of a reinforced concrete structure struck by lightning.To simulate the lightning current source,the double-exponential pulse wave shape is usedTo investigate the high-frequency response in the building,

12、 a narrow-pulse-current waveform is chosen for the source, which is 0.13/4s, where Fig. 2. Calculation model to calculate the lightning response in the structure.)(0tteeIIAI1057201s1871911s19005100Fig. 3. Currents flowing along the four vertical columns shown in Fig. 1(a)with g = 0.05 S/m.Fig. 4. Cu

13、rrents flowing along the four vertical columns shown in Fig. 1(c)with g = 0.05 S/mthe time-domain Fig. 5. Frequency spectrum of the current along column 1 with g = 0.05 S/m.the frequency-domain Fig. 6 Currents flowing along the four vertical columns shown in Fig. 1(a)with g = 0.002 S/m.Fig. 7. Curre

14、nts flowing along the four vertical columns shown in Fig. 1(c)with g = 0.002 S/mthe time-domain Fig. 8. Frequency spectrum of the current along column 1 with g = 0.002 S/m.the frequency-domain ABBecause of the oscillations superimposed on the current waveform,it is not accurate to use the peak value

15、 of every branch current to describe the current distribution percentage among the vertical columns.After filtering the current waveform through a low-pass filter with a cut frequency of 0.9 MHz,the peak value of every branch current can be used to calculate the distribution percentage.The data pres

16、ented in Tables I and II are obtained after such filtering.Table I shows the current distribution percentage among the vertical columns corresponding to Fig.1(a)and(b).The data presented in Tables I and II are obtained after such filtering.Table II shows the current distribution percentage among the

17、 vertical columns corresponding to Fig.1(c)and(e).To investigate the effect of the ring conductor on the electromagnetic environment in the building,we evaluate the magnetic field at the four points above the level of0 or 10 m,as shown in Fig.9,which is the top view of the steel structure shown in F

18、ig.1Fig. 9. Four positions where the magnetic fields are calculated.the time-domain Fig. 10. Magnetic fields at the four points shown in Fig. 1(a) and (b).Fig. 11. Frequency spectrum of the magnetic fields at the four positions shown in Fig. 1(c) and (e).the frequency-domain Fig. 12. Frequency spect

19、rum of the magnetic fields at the four positions shown in Fig. 1(d) and (f).the frequency-domain conclusionIn this paper,the FDTD method is introduced to calculate the electromagnetic environment in a steel structure.All the complicated factors,such as the resistance of the reinforcing steel bar,the

20、 self-inductance,the mutual inductance,the capacitance of conductor,the conductivity of the soil,etc.,are considered automatically in the FDTD method.From the calculation results,we have following conclusions.1)Part of calculation results by the FDTD method yield reasonable agreement with those of e

21、xisting experiments reported in related references,so the validity of the FDTD method applied to calculating lightning electromagnetic responses in reinforced concrete structures is demonstrated.conclusion2)When lightning strikes directly on a steel structure,the waveform of the current flowing amon

22、g the steel branches is not a simple scale of lightning current waveform.There are oscillations of considerable intensity superimposed on the lightning current waveform.The frequencies and the intensity of the oscillations depend not only on the size and configuration of the steel structure,but also on the conductivity of the soil.3)In practical engineering,when the grounding system and the condition of soil cannot be changed,It is beneficial to minimize the resistance of the steel columns and ring conductors,i.e.,if all the reinforcing bars in the columns and ring beams are