Following

Complex structures are highly indeterminate and therefore if one member is eliminated then also it will not have adverse effect on stability of structure. However. Some members will be over stressed and yielding of these members can take place resulting in to progressive collapse.

Need to check the design again with the set of members provided on the site. We have to be very careful as the failure of steel structures are sudden.

Manish Shah .... Totally Right... Thanks so much for your answer...

Om Prakash Chhangani ..... Absolutely... indeterminacy in some cases might provide additional safety.... that happened by re-distribution of stresses to other members... which can withstand the additional loads... either by its internal factor of safety or by going thorough the practicality reign ... so in final words... the structure heal himself ... for sure that in some special cases... not a general role..... Thanks so much Om Prakash Chhangani for your very good answer.

It is not legal to anybody (especially with no experience) to change the design out of the designer consulting agreement. The resident engineer (RE) should be responsible in ensuring that the structural design according to the original contract is always followed.

Ahmed S. H. Suwaed , ... Thanks for your answer, ... but its happened, not always, ... but its happened, ... I did check that many times in many projects

The important now, is what the safe response and how can fix that in easiest way.. and the most reliable question is related to the cost of fixing the case, ... try to reduced that cost up to its minimum value with good range of safety..

Thanks again

I think the safe respond, from structural point of view, is to analyze the modified structure and check everything! I mean every member at every condition was included in the original design. Sometimes the structure is safe against ultimate loading but still not accepted because of excessive displacement, for example, after let say 10 years!

Ahmed S. H. Suwaed .... 100% Right... again I want to consider the re-distribution of stress due to eliminating or changing some members.... sure after checking the whole structures members and their connections .... considering as you say.. the long run deformations....

Ahmed S. H. Suwaed .... Thanks again for your answer...