动态控制参数的含义DyncontrolWord下载.docx

1、 Static Load Case for Nonlinear Restraint Status动态分析是线性的分析，在开始建立分析模型之前，我们选择哪个工况作为开始。STATIC LOAD CASE FOR NONLINEAR RESTRAINT STATUS （Active for: Harmonic, Spectrum, Modal, Range, and Time History） Currently all of CAESAR IIs dynamic analyses act only on linear systems, so any non-linearities must be

2、 linearized prior to analysis. This means that one-directional restraints will not lift off and reseat, gaps will not open and close, and friction will not act as a constant effort force. Therefore, for dynamic analyses, all non-linear effects must be modeled as linear - for example, a one-direction

3、al restraint must be modeled as either seated （active） or lifted off （inactive）, and a gap must be either open （inactive） or closed （active）. This process is automated when the static load case is selected here - CAESAR II automatically activates the non- linear restraints in the system to correspon

4、d to their status in the selected load case （the user may think of this as being the loading condition - for example Operating - of the system at the time at which the dynamic load occurs）. It must be noted that this automated linearization does not always provide an appropriate dynamic model, and i

5、t may be necessary to select other static load cases or even to manually alter the restraint condition in order to simulate the correct dynamic response. A static load case must precede the dynamics job whenever: 1） There are spring hangers to be designed in the job. The static runs must be made in

6、order to determine the spring rate to be used in the dynamic model. 2） There are non-linear restraints, such as one-directional restraints, large-rotation rods, bi-linear restraints, gaps, etc. in the system. The static analysis must be made in order to determine the active status of each of the res

7、traints for linearization of the dynamic model. 3） There are frictional restraints in the job, i.e. any restraints with a nonzero （mu） value. 0.0 Stiffness Factor for Friction （0.0-Not Used）解释这个含义 STIFFNESS FACTOR FOR FRICTION （0.0-NOT USED） All of CAESAR IIs dynamic analyses are currently linear, s

8、o non-linear effects must be linearized. Modeling of friction in dynamic models presents a special case, since friction actually impacts the dynamic response in two ways - static friction （prior to breakaway） affects the stiffness of the system, by providing additional restraint, while kinetic frict

9、ion （subsequent to breakaway） actually affects the damping component of dynamic response; due to mathematical constraints, damping is ignored for all analyses except time history （for which it is only considered on a system-wide basis）. CAESAR II allows friction to be taken into account through the

10、use of this Friction Stiffness Factor. CAESAR II approximates the restraining effect of friction on the pipe by including stiffnesses transverse to the direction of the restraint at which friction was specified. The stiffness of these frictional restraints is computed as: Kfriction = （F）*（）*（Fact） W

11、here: Kfriction = stiffness of frictional restraint inserted by CAESAR II F = the force at the restraint taken from the static solution = mu, friction coefficient at restraint, as defined in the static model Fact = Friction Factor from the control spreadsheet This factor should be adjusted as necess

12、ary in order to make the dynamic model simulate the systems actual dynamic response （note that use of this factor does not correspond to any actual dynamic parameter, but is actually a tweak factor to modify system stiffness）. Entering a friction factor greater than zero causes these friction stiffn

13、esses to be inserted into the dynamics job. Increasing this factor correspondingly increases the effect of the friction. Entering a friction factor equal to zero ignores any frictional effect in the dynamics job. Max. No. of Eigenvalues Calculated （0 - Not Used） MAX. NO. OF EIGENVALUES CALCULATED （0

14、-NOT USED） （Active for: Spectrum, Modal, and Time History） The first stage of the Spectrum, Modal, and Time History analyses, is the use of the Eigensolver algorithm to extract the piping systems natural frequencies and mode shapes. For the Spectrum and Time History analyses, the response under load

15、ing is calculated for each of the modes, with the system response being the sum of the individual modal responses. Obviously, the more modes that are extracted, the more the sum of those modal responses resembles the actual system response. The problem is that this algorithm uses an iterative method for finding successive modes, so extraction of a large number of modes usually requires much more time than does a static solution of the same piping system. The object is to extract sufficient modes to get a suitable solution, without straining computational resources. CAESAR I