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Oulun yliopiston väitöskirjat

LIMIT STATE DESIGN FOR STRENGTHENING FOUNDATIONS OF HISTORIC BUILDINGS USING PRETESTED DRILLED SPIRAL PILES WITH SPECIAL REFERENCE TOST. JOHN’S CHURCH IN TARTU, ACTA UNIVERSITATIS OULUENSIS C Technica 392

ISBN-13:	978-951-42-9576-8
Kieli:	englanti
Kustantaja:	Oulun yliopisto
Oppiaine:	Tekniikka, matematiikka
Painosvuosi:	2011
Sidosasu:	pehmeäkantinen
Sijainti:	Print Tietotalo
Sivumäärä:	126
Tekijät:	AVELLAN KARI

22.00 €

This thesis discusses strengthening foundations of historic buildings by means of pretested, end-jacked, steel piles; pretested, end-jacked drilled spiral steel piles, as well as the geotechnical andstructural design of strip foundations using ultimate limit state method. Strengthening thefoundations of historic buildings is a field of engineering where every site is more or less differentfrom another. The variation of the substructure, foundation, and superstructure make every caseunique. Preserving heritage buildings by preventing structural decay requires know-how andsuitable strengthening methods. Drilled spiral piles and jacked piles were employed as strengthening methods for St. John’sChurch of Tartu, because of the sinking and uneven settlement of the building. The strengtheningwork at St. John’s Church was challenging due to the risk of collapse of this historic church.Underpinning with jacked piles is a preferred method for strengthening historic foundations andwhere drilled spiral piles were employed, the author of this thesis developed special equipment. The strengthening method employed for the tower complies with the anastylosis principle bypreserving the authenticity of the structures. Old block stones are visible upon the floating piledrafts. The empty space was left to give archaeologists and engineers a chance to study the realizedwork “in situ” in the future. The foundation of the tower was underpinned step by step with pretested jacked piles and aconcrete raft poured step by step. The weight of the tower is 5500 tons and it rests on four pillars.Every pillar rests on its own floating piled raft. This thesis proves that by means of lower and upper bound theorems a floating, piled strip-foundation can be designed geotechnically and structurally using one method based on ultimatelimit state (ULS) and serviceability limit state (SLS). The method takes the following into accountas geotechnical requirements: contact pressure, total settlement and angular distortions; and asstructural requirements; admissible plastic rotations, end moments due to displacement angle, aswell as control of cracking. The chosen piling methods were suitable for St. John’s Church, andthe installed piles work well in addition to the old foundations. The functionality of thestrengthening techniques has been verified by test piling. Furthermore, every drilled spiral pilewas preloaded twice and end-jacked for soil hardening.

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