## 1 Introduction
It is a common norm to start with simplified models in such scenarios. Also, in wind tunnel testing, it is not possible to capture all the structural behaviors, and a common approach is to use MDoF systems. An MDoF system is the best representation of a tall building and is widely used in computational studies for evaluating the wind effects on structures. A more complex and accurate structural model may be built at a later time as more information and decisions on the structural system are made in a design scenario. However, the accuracy of these simplified models has not been not well studied in the literature. Here, in this contribution, a systematic study is carried out to quantify the effects of simplified modeling in structures under transient loads with a focus on the wind. The current study aims to assess (dynamic) wind load in various scenarios (angle of attack, degree of turbulence) obtained from CFD simulations, which represent the input load case in the form of force time history on the structural model. A generic highrise structure (CAARC B--a well-established model in the wind engineering community proposed by the International Association of Wind Engineering--IAWE [10; 11]) is chosen due to the vast literature available related to the airflow around it as well as necessary information regarding the choice and set up of the structural model. Originally, the structural model is only prescribed a certain geometry (uniform rectangular along height), mass distribution (uniformly along height), eigenfrequencies of the first three modes (weak and strong bending, torsion), and type of mode shape (linear, as the initial study way intended for HFFB in experimental wind tunnels). Additional remarks on structural damping are given for the assessment of responses. This study takes these existing prescriptions and uses them as a base model: continuous and uniform mass and stiffness distribution along the height chosen so that target parameters (eigenfrequencies) are met. The study of slight variations of this model, aiming to assess other scenarios typical for the engineering practices for such constructions, such as three intervals along the height with varying mass and stiffness distribution, is included. A model of the building with a full FEM model is presented, comparing the responses with approximate MDoF systems. Wind loading is considered as a given input, with the variations described previously. Structural models and respective modifications will be analyzed as briefly outlined. The systematic parametric study is further enhanced with the investigation of the spatial resolution of the structural model itself. This last step aims to quantify the effect of structural detailing through the usage of various (decreasing) numbers of structural elements. It is aimed to highlight what minimum requirements related to proper analysis are needed, such that certain target response parameters (e.g., time and magnitude of maximum displacements and accelerations) are captured with sufficient accuracy. The insights are linked to modal analysis and a subsequent reduction of the number of modes in order to identify minimally relevant ones. The numerical toolchain that is developed and used permits a flexible and thorough parametric assessment of these aspects. The accuracy assessment of these simplified models can be useful for both simplified numerical modeling and the use of simplified models in wind tunnel tests. The rest of this paper is organized as follows: Section 2 describes the methodology used for modeling and analyzing fluids and structures. Section 3 describes the details of the numerical study and results, and discusses the obtained results. Section 4 presents the conclusions and outlooks.