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From version < 40.5 >
edited by IwonaBudny
on 2018/09/10 12:55
To version < 40.6 >
edited by IwonaBudny
on 2018/09/10 13:10
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266 266  
267 267  (% style="text-align: justify;" %)
268 268  Calculation input parameters can be set in the Calculation dialog in Analysis/ Seismic analysis in the Setup as can be seen below.
269 +
269 269  
270 270  (% style="text-align: justify;" %)
271 271  [[image:1536569776410-536.png||height="76" width="250"]]
... ... @@ -300,7 +300,7 @@
300 300  * Modal response spectrum analysis (Modal analysis).
301 301  
302 302  (% id="H1.Lateralforcemethod" %)
303 -=== 1. Lateral force method ===
304 +=== Lateral force method ===
304 304  
305 305  In some codes called equivalent static analysis.EC8 as well NS3491-12 uses this method. The user may not use this method in other codes.
306 306  
... ... @@ -336,7 +336,7 @@
336 336  
337 337  )))
338 338  
339 -==== a. Linear distribution of horizontal seismic forces (Static, linear shape) ====
340 +==== Linear distribution of horizontal seismic forces (Static, linear shape) ====
340 340  
341 341  In this method the distribution of base shear force happens according to a simplified fundamental mode shape which is approximated by horizontal displacements that increased linearly along the height (see EC8 4.3.3.2.3(3)). The seismic action effects shall be determined by applying to the x' or y' direction. The horizontal forces are:
342 342  
... ... @@ -378,13 +378,14 @@
378 378  * unusable if the horizontal foundation is elastic
379 379  )))
380 380  
381 -== [[image:1536570428267-379.png||height="205" width="330"]] ==
382 +(% class="wikigeneratedid" id="H" %)
383 +[[image:1536570428267-379.png||height="205" width="330"]]
382 382  
383 383  (% style="text-align: justify;" %)
384 384  If any of the above mentioned situations happen, the static, mode shape or modal analysis should be used.
385 385  
386 386  
387 -==== b. Distribution of seismic forces according to fundamental mode shapes (Static, mode shape) ====
389 +==== Distribution of seismic forces according to fundamental mode shapes (Static, mode shape) ====
388 388  
389 389  (% style="text-align: justify;" %)
390 390  In this method the distribution of base shear force happens according to the base vibration shape (see EC8 4.3.3.2.3(2)P). The horizontal forces acting on the place of mi are:
... ... @@ -412,15 +412,19 @@
412 412  (((
413 413  Remarks:
414 414  
415 -* The calculation of base shear force is performed according to the total mass of the structure and not the effective mass, as was introduced earlier in Lateral force method.
417 +* The calculation of base shear force is performed according to the total mass of the structure and not the effective mass, as was introduced earlier in** Lateral force method**.
416 416  )))
417 417  
418 -=== 2. Modal response spectrum analysis (modal analysis) ===
420 +===
421 +Modal response spectrum analysis (modal analysis) ===
419 419  
420 420  (% style="text-align: justify;" %)
421 -This method can be used in all national codes. The essence of the method is the calculation of the structural response for different ground motions by the sufficient summation of more vibration shapes. Method gives possibility to take into account full x, y and z direction investigation. In the table below, more vibration mode shape could be selected in x', y' and z' directions if necessary. The last row of the table shows that in a given ground motion direction how large is the sum of the considered effective masses compared to the total or reduced mass of the structure.
424 +This method can be used in all national codes.
422 422  
423 423  (% style="text-align: justify;" %)
427 +The essence of the method is the calculation of the structural response for different ground motions by the sufficient summation of more vibration shapes. Method gives possibility to take into account full x, y and z direction investigation. In the table below, more vibration mode shape could be selected in x', y' and z' directions if necessary. The last row of the table shows that in a given ground motion direction how large is the sum of the considered effective masses compared to the total or reduced mass of the structure.
428 +
429 +(% style="text-align: justify;" %)
424 424  According to EC8 4.3.3.3.1(3) and NS3491-12 sum of the effective mass of the chosen mode shapes - at least in horizontal direction - should reach 90% of total mass. Additionally every mode shape has to be taken into account which effective mass is larger than 5%.
425 425  
426 426  (% style="text-align: justify;" %)
... ... @@ -457,7 +457,6 @@
457 457  T,,j ,,/ T,,i ,,> 0,9 with T,,j ,,≤ T,,i,,
458 458  
459 459  
460 -
461 461  FEM-Design always applies the selected rule for the summation except if the **Automatic **is highlighted. If the **Automatic **is selected then the rule selection procedure is as follows:
462 462  
463 463  * (((
... ... @@ -469,7 +469,6 @@
469 469  If at least one dependent situation exists in a direction, the program automatically uses the CQC rule for all mode shapes in that direction, otherwise SRSS rule is used.
470 470  )))
471 471  
472 -----
473 473  
474 474  == Other setting possibilities ==
475 475  
... ... @@ -499,9 +499,8 @@
499 499  In FEM-Design Reduced mass means the difference between the total mass of the structure and the basement mass. The basement mass is the sum of all masses which lay on the foundation level which can be set in the Others tab of seismic load.
500 500  
501 501  It is uninteresting from the calculation point of view that effective masses are compared to the total or the reduced mass because these values are given in percentage and only gives information about which mode shape is the fundamental or which shapes are dominant in a given direction.
506 +
502 502  
503 -----
504 -
505 505  == Combination rule, rotation and second order effects ==
506 506  
507 507  (% style="text-align: justify;" %)
... ... @@ -513,7 +513,7 @@
513 513  The first rule which is called SRSS is implemented to all the other codes than EC8 and NS3491-12 and there is no possibility for rule selection.
514 514  
515 515  (% id="HTorsionaleffect" %)
516 -=== **Torsional effect** ===
519 +=== Torsional effect ===
517 517  
518 518  (% style="text-align: justify;" %)
519 519  According to EC8 4.3.2 the program gives possibility to take into account the accidental mass distribution of the structure by the calculation of the torsional effect. This means that from the horizontal seismic forces a Z directional torsional moment can be calculated according to EC8 4.3.3.3.3 (EC8 4.17 equation) as follows:
... ... @@ -552,7 +552,7 @@
552 552  It was seen that the influence of uncertainties of mass position was modeled by the rotation effect. According to our experiment using the FE method, when a plate, a wall and beams are divided into several elements the accidental torsional effect is not reasonable.
553 553  
554 554  (% id="HSecond-ordereffects28P-2206effects29" %)
555 -=== **Second-order effects (P-∆ effects)** ===
558 +=== Second-order effects (P-∆ effects) ===
556 556  
557 557  (% style="text-align: justify;" %)
558 558  Only EC8 gives a possibility to calculate the second order effect which is done according to 4.4.2.2(2). The second order effect is ignored if the following condition is fulfilled in all storeys and all horizontal directions:
... ... @@ -587,10 +587,9 @@
587 587  * To calculate thesecond order effect, storey(s) should be defined.
588 588  )))
589 589  
590 -----
593 +==
594 +Displacement calculation ==
591 591  
592 -== Displacement calculation ==
593 -
594 594  (% style="text-align: justify;" %)
595 595  The displacement calculation is made according to EC8 4.3.4 using the following formula:
596 596  
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