# Parametric Analysis of the Shear Lag Effect in Tube Structural Systems of Tall Buildings
## 6 Conclusions  
The prototype structure of a 126 m high (36 storeys) tube structural system tall building was analyzed, comprising of a reinforced concrete column and beam panel members. For a varying set of parameters defining layout dimensions from 24 to 43 m, column spacing from 2 to 3 m, beam height from 0.8 to 1.2 m, and two different horizontal load profiles, following conclusions can be made regarding changes in the shear lag effect:  
1. The positive shear lag effect is characteristic for the lower storeys of the structure and as the structure rises, the positive shear lag decreases and gradually transforms into negative shear lag which then increases to the buildings top. This transformation usually happens at around 33% of the building height measured from the bottom to the top except in the case of the variation of the layout dimensions where the transformation happens at 50% of the building height. (2) The increase of column spacing, with the layout dimensions of the building staying the same, has no major impact on the positive shear lag effect that is characteristic for the lower storeys of the building. The position of the change from the positive to the negative shear lag is also not conditioned by the column spacing. In upper storeys, where negative shear lag appears, with the increase in column spacing the negative shear lag increases. (3) The increase of beam height results in the decrease of positive and negative shear lag effect. During the horizontal loading of tube structures due to the flexibility of beams in flange and web panels they bend under horizontal loads which results in unequal distribution of axial forces in columns of the panel. Therefore, if the beam is higher, the deformation under horizontal loads is smaller and thus the shear lag effect decreases. The storey where the transformation from the positive to the negative shear lag occurs is not conditioned by the beam height. (4) The increase in the building layout dimension on which the horizontal load acts (flange panel) results in the increase of positive and negative shear lag effect. As the flange panel widens, the cumulative deformations of flexible beams increase. The transformation from the positive to the negative shear lag is conditioned by the layout dimensions ratio in tall tube structural systems. As the flange panel on which the horizontal load acts widens, the transformation from the positive to the negative shear lag happens on progressively higher storeys of the structure. (5) The positive and negative shear lag effects are more significant for the continuous horizontal load profile with a constant value than for the actual variable wind load profile.  
Conceptualization, I.H. and A.V.; methodology, A.V.; software, I.H. and A.V.; validation, A.V., T.K. and T.R.; formal analysis, I.H. and A.V.; investigation, I.H.; resources, I.H., A.V. and T.K.; data curation, A.V.; writing--original draft preparation, I.H.; writing--review and editing, A.V., T.K. and T.R.; visualization, I.H.; supervision, A.V. and T.K.; project administration, I.H.  
Please turn to the CRediT taxonomy for the term explanation. Authorship must be limited to those who have contributed substantially to the work reported. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy restrictions.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.