Optimisation of structures to reduce costs and environmental impacts are important issues in the building sector. In order to meet these the computer program Opti_String is developed for optimising reinforced concrete walls using the stringer method based on the plasticity theory. The program is formulated by a finite element concept. The Eurocode is implemented in Opti_String to ensure practical design demands.
A lower bound method is compared with an upper bound method. The comparison shows that an exact translation for the stringer system exists.
Opti_String is capable of optimising an ar- bitrary geometry and the optimisation is based on the lower bound method. Opti_String calculates the ultimate load bearing capacity or design parameters for a given load along with the stress parameters.
By use of a complex structure the influence of practical design restrictions and several load cases are illustrated. Different weighting parame- ters are applied to force another stress distribution in order to decrease the utilisation of selected stringers.