Modular construction systems in Switzerland: structural assessment and development of retrofit measures

(original title: Systembau in der Schweiz: Tragwerksanalyse und Entwicklung von Ertüchtigungsmassnahmen)

Author: Konstantinos Theocharis
Language: German

Abstract

This Master’s thesis deals with the structural assessment and the development of retrofit measures of buildings that were erected in a modular way with prefabricated elements known as GOEHNER system. First, the vertical structure of the GOEHNER settlements, which were predominantly erected in the Zurich and Geneva area between the 60s and 80s of the last century, is briefly described. Then, the horizontal load-bearing system is analysed and the capacity of the horizontal stiffening walls against horizontal actions is determined by establishing moment - normal-force interaction diagrams. The earthquake and wind actions are calculated for two- to eleven-storey buildings and compared to the load-bearing capacities of the stiffening walls. The earthquake actions are thereby determined according to the response spectrum method according to the Swisscode.

The investigated buildings are structurally deficient, particularly for earthquake loads. Hence, the safety factor αeff is determined and retrofit measures are developed for the decisive stiffening walls for safety factors αeff ˂ αmin according to the Swisscode. The examined retrofit measures are (i) the strengthening of the available steel connections of the walls in vertical direction; (ii) an external, centric post-tensioning of the walls; (iii) and an eccentric post-tensioning with carbon-fibre-reinforced polymer lamellae glued on the walls. The effectiveness of the third measure is significantly greater than the first two due to the higher increase in the bending resistance of the walls and the compressive force acting from the outside.