Question: What is the reason for Utzon's designs being changed in the Sydney Opera House?
About the article "Sydney Opera House", section "Significant changes to Utzon's design".

Candidate passages:
Hughes was elected as a member of the New South Wales Legislative Assembly for Armidale from 1950 to 1953 and 1956 to 1973 for the Country Party.
He was chosen to lead the party in 1958, but his term of office was brief because he was forced to resign in 1959 after it was revealed that he did not have the university degree which he claimed.
With the election of the Askin government in 1965, Hughes became Minister for Public Works, with responsibility for, among other things, the completion of the Sydney Opera House.
He eventually brought about Jørn Utzon's resignation.
Hughes refused to accept Utzon's approach to managing the Opera House project and, specifically, to give permission for the construction of plywood prototypes for its interiors.
He cut off Utzon's funding so Utzon could not even pay his own staff.
Utzon was forced to resign, and Hughes immediately accepted.
The Opera House was subsequently completed according to designs that were inconsistent with Utzon's original vision.
With his resignation from parliament in January 1973, Hughes was appointed NSW Agent-General in London.
He died at Erina, New South Wales. 
Additive Architecture is an approach used by Danish architect Jørn Utzon to describe his development of architectural projects on the basis of growth patterns in nature.
Mogens Prip-Buus, one of Utzon's closest colleagues, reports that the term was coined in 1965 in Utzon's Sydney office when, after a discussion of the social structures in Britain and Denmark, Utzon suddenly jumped up and wrote "Additive Architecture" on the wall.
He saw it as part of an additive world where both natural and cultural forms contributed to additive systems and hierarchies.
He realized that his own architecture reflected the same principle, just as the transitions in primitive societies between family, village and the surrounding world have visible links revealing differences, relations and distances.
Utzon observed the additive approach in Chinese temples whose stacked timber structures are basically identical, differing only with the size of the building.
In his "Additive Architecture" manifesto in 1970, he tells us how he saw the phenomenon reflected in a group of deer at the edge of a forest or in the pebbles on a beach, convincing him that buildings should be designed more freely rather than in identical box shapes.
Earlier, in 1948, he had expressed the same ideas in an essay titled "The Innermost Being of Architecture" stating: "Something of the naturalness found in the growth principle in nature ought to be a fundamental idea in works of architecture.
"The application of the additive approach can be seen in many of Utzon's works including the courtyard housing schemes which began with the Kingo Houses, the tiling of the Sydney Opera House and his designs for a sports complex in Jeddah.
Utzon's early competition project for a crematorium in 1945 also exemplifies his approach.
The building's free-standing walls could be extended over time, a new brick being added for each cremation.
Examples of the Additive Architecture approach in Utzon's work can also be seen in his designs for the unbuilt Silkeborg Museum, the Farum Town Centre proposal, the Herning expansion plan including a "school town" and the flexible Espansiva approach for low-cost housing which only resulted in a prototype.
Perhaps the best example of all is the proposal for a major sports centre in Jeddah, Saudi Arabia, based on the use of a limited number of repeating elements. 
Paustian House () is a large furniture showroom located on the waterfront in Copenhagen.
Completed in 1987, it is one of the most notable works in Denmark by prize-winning architect Jørn Utzon, who also designed the Sydney Opera House.
Utzon's son Kim designed two adjacent buildings which were completed in 2000. 
 The major hall, which was originally to be a multipurpose opera/concert hall, became solely a concert hall, called the Concert Hall.
The minor hall, originally for stage productions only, incorporated opera and ballet functions and was called the Opera Theatre, later renamed the Joan Sutherland Theatre.
As a result, the Joan Sutherland Theatre is inadequate to stage large-scale opera and ballet.
A theatre, a cinema and a library were also added.
These were later changed to two live drama theatres and a smaller theatre "in the round".
These now comprise the Drama Theatre, the Playhouse, and the Studio, respectively.
These changes were primarily because of inadequacies in the original competition brief, which did not make it adequately clear how the Opera House was to be used.
The layout of the interiors was changed, and the stage machinery, already designed and fitted inside the major hall, was pulled out and largely thrown away, as detailed in the 1968 BBC TV documentary "Autopsy on a Dream", which "chronicles the full spectrum of controversy surrounding the construction of the Sydney Opera House".
 Externally, the cladding to the podium and the paving (the podium was originally not to be clad down to the water, but to be left open).
 The construction of the glass walls (Utzon was planning to use a system of prefabricated plywood mullions, but a different system was designed to deal with the glass).
 Utzon's plywood corridor designs, and his acoustic and seating designs for the interior of both major halls, were scrapped completely.
His design for the Concert Hall was rejected as it only seated 2000, which was considered insufficient.
Utzon employed the acoustic consultant Lothar Cremer, and his designs for the major halls were later modelled and found to be very good.
The subsequent Todd, Hall and Littlemore versions of both major halls have some problems with acoustics, particularly for the performing musicians.
The orchestra pit in the Joan Sutherland Theatre is cramped and dangerous to musicians' hearing.
The Concert Hall has a very high roof, leading to a lack of early reflections onstage—perspex rings (the "acoustic clouds") hanging over the stage were added shortly before opening in an (unsuccessful) attempt to address this problem.
Utzon's design was widely imitated in the 1950s, first for one-family homes and later on a larger scale, when the Louisiana Museum in Humlebæk was built by Vilhelm Wohlert and Jørgen Bo in 1958.
Halidor Gunnløgsson and Erik Christian Sørensen were among those who emulated Utzon's approach, developing a new Danish trend.