**1. Introduction**

In the recent times, dynamically increase in population and limitation of land acquisition high-rise structures or multi-story building become major concern of researchers. The critical issue in high-rise buildings is selecting proper structural form to resist the lateral and flexural loads. Therefore, the static and dynamic responses of high-rise building is essential to design safe and reliable structure for engineers. These high-rise buildings may be transformed into multi-story buildings in order to make more floors space but occupy less lands space [1]. These multistory buildings are used for residential flats, offices, shopping complex, Malls, Hotels and public centers.

Lateral loads such as wind load and seismic load play predominant role in high-rise structures.

#### **1.1 Wind loading**

There are several instances where structures have failed owing to an instability that needs second-order analysis (P-Delta). One of the problems resulted from wind loading. The wind induces outward and inward as a triangular load act on the surfaces of multi-story buildings. Structural instability issues arises when structures could not bear certain loads and buckling of structures +occurs due to dead load, wind load and seismic load like earthquake [2]. Ankireddi and Yang [3] considered gradually increased load along building height (wind load) as shown in **Figure 1**. To simplify the analysis [4, 5] load is reduced by 50 percent at the center of building as consideration of BS EN 1991-1-4:2005.

The direction of wind is very important throughout the life of structure. Wen [6] found that the wind direction analysis is not conducted seriously. Analysis of wind direction becomes necessary for the case of high-rise buildings and suspension bridges. Moreover, wind speed is also plays crucial role on construction sites, structures will collapse without warning due to speed of wind. For example, building, power lines and trees are collapsed in Hurricane Frederic east of Pascagoula, Mississippi on September 12, 1979 in coastal areas. Mehta et al. [7] estimated the effect of wind speed based on an indirect approach. Authors collected comprehensive data to introduce an alternate approach and convenient equipment. It is noticed that wind speed and direction significantly contribute in deflection of multi-story structures.

#### **1.2 Urban context and sustainability**

For energy saving and sustainable development high-rise building requires sunlight access, considering optimum utilization of limited conventional resources.

**Figure 1.** *Wind loads act on the surface of the building [3, 5].*

*Perspective Chapter: Dynamic Analysis of High-Rise Buildings Using Simplified Numerical… DOI: http://dx.doi.org/10.5772/intechopen.108556*

Therefore, new multi-story buildings are optimized on its shape, height and orientation considering environmental factors such as harmony between buildings and their urban and environmental contexts.

Environment friendly structures are classified into three basic sets of strategies. First one is the minimization of operation cost and material consumption; second one minimization of energy consumption or maximum utilization of solar energy and sun light; third one is consideration of whether conditions according to different climate zones.

To design building for different climatic zones, then consider the hot seasons and the cold seasons to deal with, and you have the two mid- seasons. So, you have to design the enclosure, the skin as a responsive environmental filter for energy efficiency.

For the analysis purpose, a cantilever beam (*l* = 60 m, *b* = 12 m and *h* = 1 m) with fixed support at bottom and free at remaining all three ends is modeled as high-rise building. The analysis is performed considering the building experiencing different loading conditions viz., uniformly distributed load, uniformly varying load (wind load) with zero magnitude at bottom and the combination of the two said loads.

The static behavior of hybrid high rise buildings have been studied here considering a vertical cantilever flat panel under uniformly distributed load, wind load and combination of both. Linear bending response of vertical cantilever plates has been analyzed under triangular load. The structural analysis of tall buildings has been carried out here through commercial software ANSYS.

#### **1.3 High-rise building considered as cantilever beams**

An approximate method for the static and dynamic analysis of high-rise buildings is continuum method in which these structures are substituted by a continuum beam/ plate, adopting Euler-Bernoulli or Timoshenko beam theory/Classical or Mindlin or higher-order plate theory. The bending analysis of tall building have been performed by employing continuum-based Kwan model, here, tall buildings were considered as a cantilever beam and studied bending behavior of tall building by employing Euler-Bernoulli beam theory [8] and also compared the analytical results with numerical results obtained by ETABS software. Framed tube structures primarily act like cantilever hollow box beams. These beams could resist more moments of the lateral loads; the beam bending action of the framed tube structures were complicated due to shear lag in the web and flange panel; [9] introduced a simple hand-calculation method considering shear lag effect for approximate static analysis of framed tube structures. Alavi et al. [10, 11] proposed a simple mathematical technique to design minimum cost tall and slender structures that might be used as conceptual/early-stage design. Authors considered the tall structures as cantilever beam and studied the flexural vibration behavior [10] and peak lateral deflection response [11] of high-rise buildings. They also performed the parametric study considering 42-story and 60-story buildings.

Most of the researchers modeled the tall building as cantilever beam to study the free vibration behavior [12**–**16]. The discrepancy of empirical formulas given by various researchers for the fundamental frequency of tall buildings was examined by Dym et al. [12] and used the Euler-Bernoulli and Timoshenko beam model to estimate the natural frequencies of these structures. The natural frequency of multistory building under seismic load was determined by Kaviani et al. [14] using

Timoshenko beam theory. They assumed each lateral load carrying subcomponent (floor) of tall building is considered continuous cantilever beam with variable cross-section.

The natural frequencies of framed tube and shear walls structures have been calculated by using energy method and Hamilton's principle [17]. Authors considered the framed tube and shear walls structures as a cantilever beam based on continuum approach. They also compared the analytical results with numerical results obtained by SAP2000. Piccardo et al. [18] introduced an equivalent three-dimensional space continuous Timoshenko beam model to study the static and dynamic behavior of tower building.

Hallebrand and Jakobsson [19] investigated the high-rise building under static and dynamic loads to investigate the effect of deflections, resonance frequencies, accelerations and stability. They discussed the modeling techniques and issues to model highrise building using finite element method. Authors also compared the vertical loading (such as self-weight, imposed loads, snow loads and live loads) and horizontal loading (for example wind load or design load and unintended inclinations) considering different modeling techniques.

Miranda [20] introduced an approximate method based on an equivalent continuum beam model to determine lateral displacement and maximum inter-story drift of tall buildings under seismic load. Multistory structures were considered as an equivalent continuum model taking in account the combination of shear cantilever beam and flexural cantilever beam. Author examined the effect of lateral force along the height of tall structures, shear deformations, flexural deformations on the multistory buildings that was considered as a beam structure. An approximate method was further generalized [21] to consider the non-uniform lateral stiffness of tall structures. The non-uniform Timoshenko beam was modeled [22] to describe the spectrum analysis of it. They assessed the first four vibration modes of non-uniform Timoshenko beam model under seismic loading conditions. Attention of researchers is also focused on the eigenvalue solutions of beams (Rafezy and Howson 2008) that would be considered as a high-rise building.

Authors considered the step change of properties along the height of the structures. Recently, the nonlinear static and dynamic response of thin-wall composite structures were investigated [23**–**26] by employing finite element method with firstorder shear deformation theory. Here, author considered a high-rise building as a cantilever plat to study the static and dynamic behavior of these thin-wall structures.
