Comparison of actual and theoretical loads due to a crane's outriggers

Abstract

Recent changes in the crane i n d u s t r y throughout the world have placed a g r e a t e r emphasis on pre-planning l i - ft crane operations. One important aspect of pre-planning a s a f e l i f t i s the assurance of an adequate supporting foundation for the crane. In order to^do t h i s , the load imposed on the foundation by the crajnes o u t r i g g e r s must be determi ned. I r v i n g Equipment^ a d i v i s i o n of J . D . I r v i n g L t d . , which i s a crane r e n t a l company h^sc^e" i n A t l a n t i c Canada, p r e s e n t ly uses a t h e o r e t i c a l method of determining the o u t r i g g e r loads of t h e i r cranes. As t h i s information i s becoming more and more important to almost every job, t h i s company f e l t that i t would be b e n e f i c i a l to compare the t h e o r e t i c a l loaub Lu an actual s i t u a t i o n to confirm the accuracy of t h i s method. The t e s t crane's outrigger loads proved to be c o n s i s t e n t l y g r e a t e r than the c a l c u l a t e d values. G r a p h i c a l ly however, both methods produced s i m i l a r trends. T h is i n d i c a t e d that even though the t h e o r e t i c a l method produced lower outrigger loads, i t may be due to the machine's component weights, which were obtained from the manufacturer, being greater than the weights used i n the c a l c u l a t i ons. Because the l o a d s t r a n s m i t t e d to t h e foundation of mobile truck c r a n e s , due to i t ' s o u t r i g g e r s , i s becoming an important f a c t o r on j o b s , i t i s recommended t h a t exact machine weights be determined and t h a t a second comparison be done. I t i s a l s o recommended t h a t on l i f t s which a re c o n s i d e r e d c r i t i c a l , that i s where t h e r e i s s i g n i f i c a n t concern with r e s p e c t to the c r a n e s supporting f o u n d a t i o n, t h a t p r e s s u r e gages be i n s t a l l e d on each o u t r i g g e r so t h at continuous monitoring can be conducted.