Design verification of a force- and displacement-based designed torsionally-unbalanced wall building

Student: Sara Martini
Supervisors: Dr R. Pinho

Abstract

The Direct Displacement-Based Design (DDBD) is a procedure that has been developed over the past ten years in order to solve the problems of the current Force-Based Design (FBD), related to the use of the initial stiffness and to the assumption that a unique force-reduction factor is appropriate to a given structural type and material. This individual study has the aim of apply the FBD and DDBD approach to a torsionally eccentric structural wall building and compare the response of the two designed structures to a target profile related to a given limit state and seismic input level.

The design procedures are applied to an asymmetric structural wall building and the torsional effects due to its irregularity are considered; the wall's displacement profiles related to the given limit state and earthquake level are obtained and therefore the design shear and moment capacities of the walls are computed.

The design displacement profiles are then verified by a nonlinear dynamic time-history analysis done with the finite element program SeismoStruct. The different modelling choices (constraints, mass discretization, and hysteretic rules) are investigate in order to obtain the best representation of the real system and the use of the finite element program SAP2000 and of other types of analyses (eigenvalue and linear dynamic time-history) is considered in order to validate the final results.

The final design and analysis results have differences of about 2% for the stiff wall and 19% for the flexible one; the comparison with the Force-Based Design values (differences of about 42% and 38% respectively) shows that the Direct Displacement-Based Design leads to a better distribution of shear capacities to the walls, a better estimation of the analysis results and therefore also a lower cost of thestructural elements given that a lower reinforcement area is needed.

You may download a digital version of this MSc dissertation here.