Michi h i r o N a t o r i * I n s t i t u t e o f Space and A s t r o n a u t i cA b s t r a c t S t r u c t u r a l concept o f adaptive p l a n a r space t r u s s s t r u c t u r e s i s evaluated from t h e viewpoints o f b o t h geometrical a d a p t i v i t y and dynamic c h a r a c t e r i s t i c s . Some geometrical p r o p e r t i e s o f a f u n c t i o n model are a l s o presented t o demonstrate t h e e f f e c t i v e n e s s o f t h e concept. I n t r o d u c t i o n An adaptive s t r u c t u r e i s a new concept o f space s t r u c t u r e s which can p u r p o s e f u l l y v a r y i t s geometr i c a l c o n f i g u r a t i o n and mechanical c h a r a c t e r i s t i c s through t h e geometrical change o f component members i n order t o adapt t o t h e m i s s i o n r e q u i r ements and environmental c o n d i t i o n s . T h i s new s t r u c t u r a l concept i s seemed t o be a l s o u s e f u l as a d j u s t a b l e elements t o compensate t h e u n c e r t a i n t y i n ground t e s t i n g f o r l a r g e space s t r u c t u r e s . Adaptive t r u s s beam s t r u c t u r e s have been studi e d m a i n l y f o r t h e a p p l i c a t i o n t o space crane arms (Refs.1-5). Dorsey (Ref.1) analysed t h e v i b r a t i o n c h a r a c t e r i s t i c s o f a r e g u l a r two-dimensional c a n t i l e v e r e d t r u s s boom which c o u l d be a x i a l l y deployed o r r e t r a c t e d and undergo a v a r i e t y o f changes by t e l e s c o p i n g diagonal members i n each t r u s s bay. Miura e t a l . (Refs.2 & 3 ) presented t h e fundamental c h a r a c t e r i s t i c s o f a p o s s i b l e adaptive t r u s s beam which c o n s i s t s o f octahedral t r u s s elements, and showed i t s e f f e c t i v e n e s s through t h e o p e r a t i o n o f a f u n t i o n a l model. S i m i l a r concept has been s t u d i e d independently by Rhodes & Mikulas (Ref.4). The study o f another adaptive t r u s s beam c o n f i g u r a t i o n which c o n s i s t s o f t e t r a h e d r a l t r u s s elements has been presented i n Ref.5. Concerning t h e p l a n a r t r u s s s t r u c t u r e s , v a r i o u s conceptual s t u d i e s f o r deployable t r u s s p l a t f o r m s have been presented (Rzf. 6 -9 ) , b u t t h e a d a p t a b i l i t y o f p l a n a r t r u s s s t r u c t u r e s i s n o t discussed a c t i v e l y . This n a t u r e o f p l a n a r t r u s s s t r u c t u r e s i s d e s i r e d e s p e c i a l l y f o r shape c o n t r o l o f antenna s t r u c t u r e s . Recently, Anderson and Nimmo (Ref.10) have s t u d i e d t h e s t a t i c a l l y d e t e rminate n a t u r e o f t r u s s s t r u c t u r e s which i s one o f t h e i m p o r t a n t elements o f adaptive s t r u c t u r e s from t h e v i e w p o i n t o f dynamic c h a r a c t e r i s t i c s . It i s p o i n t e d o u t t h a t frequencies f o r t h e s t a t i c a l l y * Associate Professor, Space S t r u c t u r e s Engineering, Member AIAA determinate t r u s s p l a t f o r m decrease w i ...

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