Design of Land Oil Drilling Rog

Question

Sir, 
 I am a structural designer in Oil Field equipment. I design land oil rigs. I have couple of doubts. The entire Mast section is manufactured in segments due to transport constraint and assembled at site by use of PIN joints. How do I model this junction? The entire structure is placed on the concrete foundation. How to resemble this in the model? I have attached my model and couple of photographs as to how it looks. Kindly enlighten me. I would appreciate a reply from those who are familiar with API 4F and similar structures. Thank you in advance. Mast_Vertical_AC Rigs_AISC_ASD.std gn product with API 4F standard.

Kush · Answer

Hi, 
 Here are some suggestions for your queries: 
 How do I model this junction? 
 You can use Member Release option from General > Specs > Beam. To simulate a pinned connection you may release or partially release in MY and MZ at the member ends. As these parameter are in respect to local axis of the member, MX should not be released as this would mean that it is allowed to rotate about its own axis. 
 
 How to resemble this in the model? 
 Though you are stating that the entire structure is supported by concrete foundation but in your model pinned supports are used. This depends on how you are connecting your member with concrete foundation. Some of the questions here: Base plate connection? No. of bolts? etc. On the other hand to model concrete foundation, you can use Mat Support option from General > Support > Create > Foundation but this would mean that all your members are fixedly supported with concrete foundation.

Kush · Answer

There are a couple of options: 1. Compression only spring support: First you need to define a spring using FIXED BUT support and later assign the same to COMPRESSION ONLY spring. The sample syntax is: SUPPORTS 1 2 158 TO 161 170 TO 173 250 251 256 257 262 263 342 - 343 FIXED BUT FX FZ MX MY MZ KFY SPRING COMPRESSION 1 2 158 TO 161 170 TO 173 250 251 256 257 262 263 342 343 KFY 2. Elastic Mat (Compression only in Y-direction). The sample syntax is: SUPPORTS 1 2 158 TO 161 170 TO 173 250 251 256 257 262 263 342 - 343 ELASTIC MAT DIRECT YONLY SUBGRADE PRINT COMPRESSION Please feel free to post your queries regarding API-4F specifications. Lot of experts are always available and happy to answer them.