Concept designs for the £193 million Library of Birmingham will be unveiled on Thursday morning.

Dutch architects Mecanoo, who were selected last August from an international shortlist of seven practices, will reveal their solution to the challenge of replacing the existing 1970s Central Library with a building fronting Centenary Square, between the Repertory Theatre and Baskerville House.

The building, which will house the lending and reference libraries together with archives on a single site, will be about 20 per cent larger than the present library.

It will be built on the existing surface car park and the site of the 1980s extension to the Rep, which will be demolished.

The library will be physically connected to the Rep, with which it will share foyer, catering and meeting spaces, as well as a new 300-seat auditorium.

Mecanoo’s creative director Francine Houben, who was a founder member of the Delft-based practice 25 years ago, has paid numerous visits to Birmingham over the last six months. Her research has included walking tours of the city with local historian Carl Chinn and a lengthy conversation with Graham Winteringham, architect of the Rep.

“What is unique about the Library of Birmingham is that firstly it will be connected to the Rep and secondly it will have the whole city archive in it,” she said. “It is really the memory of Birmingham in this building,” she said.

The city has been trying to replace its brutalist central library, designed by Birmingham architect John Madin and opened in 1974, since the turn of the century.

The Richard Rogers Partnership was originally appointed after an international competition to design a library which would have formed the centrepiece of the regeneration of Eastside. But the Rogers concept of an elliptical-shaped building overlooking a new city park was abandoned after the Conservative-Lib Dem coalition won control of the city in 2004.

After aborted proposals to house the library in Baskerville House or to split library and archive services between Centenary Square and Eastside, the proposal for a joint development with the Rep was announced in 2007.

Council leader Mike Whitby has insisted that the council will fully fund the development, which is expected to begin construction next year and open in 2013.

But the project still faces a threat from campaigners on behalf of the existing library, who believe it is a building of outstanding architectural merit which should be given the protection of listed status. will reveal the new designs at 11am on Thursday.