Dynamic Response of Structure


For long span structure subject to periodic load (like human walking load), it is necessary to estimate the human comfort.

Computer program like ETABS, SAP2000 can be adopted to estimate the slab/ beam acceleration under such load. The procedure is outlined as follow (using ETABS as an example):

(1) Obtain the function of the periodic load from relevant code, like BS5400, PRC codes, etc;
(2) Define load case for the periodic load;
(3) Define Time History Function (say Sine Function) for the periodic load. Usually the amplitude for the function is taken as 1 for easy reference;
(4) Define Time History Case Data, with scale factor same as the amplitude stipulated in relevant codes. The load case (under item 2 above) shall be selected;
(5) Add loading on the floor elements under the load case in item 2 (Usually taken as 1 for easy reference);
(6) Carry out the modal analysis (with mass defined);
(7) After analysis, click "Display" -> "Show Time History Traces";
(8) Select the following: 
     "Define Function..." -> Select the Joint concerned -> Click "Modify/Show TH Function"->Vector Type "Accel" -> Component "UZ";

The result is displayed as follow:

Dynamic Response of Structure
Fig1: Dynamic Response of Structure
The acceleration shall then check against the code requirement.