Engineering Cost Versus Final Results
The above described computer assisted process of more accurate engineering modeling and solutions of mill building structural design does not come without associated costs.
This process requires substantially more engineering time to be spent in comparison with the time required to solve old simple models by computer, which before the computer era had been solved manually (for example, simple beams, planar frames and code appointed crane dynamic load factors}. It also requires involvement of more qualified personnel.
In some cases, the cost of field crane load testing to support the dynamic analyses results should also be added. However, the additional cost of engineering paid by the clients (steel producing companies} for the advanced structural analyses of mill buildings, associated with upgrading the existing buildings, could be substantially offset by the reduced field modification costs received as the result of advanced analyses.
This benefit of the advanced engineering is often not clearly recognized by the clients in the early phase of a project, or the project bid phase, when several consulting firms compete to provide engineering for a particular project In most cases, the winner is the lowest bidder, the consultant who uses the obsolete simplified approach in structural modeling and loads. This approach eventually results in high construction cost and a substantial down time in the operation
His sounds like a problem. The suggested solution could be as follows:
Prior to the bidding process, the client should develop a project specification. A conceptual description of analytical methods to achieve the most cost effective design shall be required to be presented with a bid package by each bidder for the project , in addition to the standard requirements for the structural engineering part of the project.
The following is an example of the real-life project:
A major steel producer planned to upgrade its teaming aisle of BOP and two continuous casting shops to the crane lifting capacity of 400 US tons from the existing capacities of 250 and 350 US tons.
Several engineering firms were invited to bid for performance of the structural engineering study to investigate the feasibility of the proposed upgrade and determine the scope of the modification work.
The two engineering firms provided proposals to perform the above study. The first firm offered to perform the study and develop
recommendations for the cost of $25,000; the second firm offered to perform the study and develop commendations for the cost of $100,000.
The study was awarded to the first firm. In two months the conclusion of the study as follows:
The crane runways and framings of
the investigated buildings are not able to carry cranes with 400 US ton lifted load and the lifted load for cranes shall be limited to the original design capacity.
To upgrade crane runways and building framings to accommodate 400 US ton cranes, a substantial reinforcement would be required.
However, the scope of reinforcement work was not defined.
Review of the study analyses, located in the appendix to the study report, revealed a limited number of "typical frames and crane girders" analyzed for each building utilizing simplified framing modeling and crane load approaches.
The client was not satisfied with the above study results and requested the second firm, who provided an original bid for $100,000, to perform the study.
The second study included:
Crane load dynamic analyses for the existing ladle cranes upgraded to 400 US tons. These analyses permitted to substantially reduce the crane dynamic loads in comparison with the AISE Technical Report No. 13 recommendation.
Computerized crane side thrust distribution for wide variety of framing situations. Framing analyses which accounted for the space frame affect for all different framing models in the three investigated buildings.
A full crane runway system analyses, including fatigue analyses performed by utilizing the damage accumulation principle.
During the final stage of the study, additional work on crane dynamic load determination was performed. It included the field crane load test and computerized crane/building analyses using the "ADAMS' program by MDI (additional cost of $40,000}.
The analyses proved that the existing continuous casting shops and the teaming aisle crane runways and framings could carry the upgrade to 400 US ton ladle cranes without exceeding allowable design limits.
Modification works were limited to repair of minor deficiencies found during structural inspections with a total cost not exceeding $300,000.
The personal computer revolution and creation of computerized engineering programs equipped the design engineers with analytical tools to accurately analyze mill building.
As a result of that, engineers are now able to provide a cost-effective design of new mill buildings or open hidden opportunities to upgrade existing mill buildings to increased crane loads.
An advanced computerized solution of the new mill building design or upgrade projects requires additional time to produce the results in comparison with a simplified computer solution, and this means a higher engineering cost.
However, higher engineering costs will be more than offset by the effective construction cost reduction and reduced downtime received as a result of a sophisticated design procedure.