New nonlinear dynamic response model of squat/slender flanged/non‐flanged reinforced concrete walls

Nikkhoo

Hajirasouliha

2019

Bull Earthquake Eng

Insufficient information about the seismic performance of tunnel-form buildings and limited relevant design codes and standards are the main barriers towards application of these systems in seismically active areas. Vertical and horizontal irregularity of typical tunnel-form buildings is another cumbersome challenge restricting the application of these systems. To address these issues, this study aims to evaluate the seismic behaviour of tunnel-form buildings with horizontal irregularity and develop appropriate design methodologies. Based on the results of 3, 5, 7 and 10storey buildings, new response modification factors are proposed as a function of seismic demand and expected performance level. Fragility curves are also derived for various levels of intensity, and simple equations are introduced to estimate uncoupled frequency ratios. The results, in general, demonstrate the flexible torsional behaviour of irregular tunnel-form structures and their adequate seismic resistance capacity. The buildings studied herein, managed to satisfy the Immediate Occupancy (IO) performance requirements under design-basis earthquake, which implies that the plan regularity requirement for tunnel-form buildings in seismic codes may be too conservative. Moreover, it is concluded that using response modification factor equal to 5 can generally result in sufficient stability and adequate performance level under both design basis and maximum considered earthquake scenarios.

Section: Methodology O Specifications Of Numerical Modelsmentioning

confidence: 99%

Estimation of seismic response parameters and capacity of irregular tunnel-form buildings

Nikkhoo

Hajirasouliha

2019

Bull Earthquake Eng

“…Most of the walls in plan are long and attempts to satisfy the minimum requirements of BHRC Report . Since the torsion caused by the eccentricity of the mass center can also increase the shear force in the walls, all of the walls and the link beams are assumed to be only shear deformable . Therefore, for the walls (except few walls which are bending‐control) and the link beams, nonlinear shear behavior is defined by the graph shown in Figure .…”

Section: Methodsmentioning

confidence: 99%

Seismic reliability evaluation of tunnel form (box‐type) RC structures under the accidental torsion

Mortezaei

2018

Structural Concrete

In the tunnel form (box‐type) structural system, walls arrangement and mass distribution have important effect on the interactions of thinner shear walls and slab configurations. In the other words, despite the regularity of these buildings as well as symmetry in wall arrangement and mass distribution, the first mode of structural behavior in many cases is twisting. This characteristic is limited to the flexible torsional buildings, which are often sensitive to the mass eccentricity and rotational components of earthquake. According to the available guidelines for design and construction of tunnel form systems and emphasizing on regularity of these structural systems, it seems that the most probable mass irregularity of this type of structures is asymmetric distribution of live loads during service life. Therefore, in this paper, seismic behavior of box‐type (tunnel form) buildings is evaluated under the accidental torsion caused by asymmetric distribution of mass in stories. The incremental nonlinear dynamic analysis is used for this purpose. Despite the asymmetric distribution of mass in plan, the results demonstrate high capacity and appropriate seismic behavior of the tunnel form system. Therefore, an eccentricity equal to 10% of the plan dimension does not change the building performance level, which is higher than the immediate occupancy level under the design and maximum probable earthquake hazard levels.

“…Next, deep beam relations were applied to estimate the nominal shear strength of the coupling beams (ACI318, 2014). The other parameters required to define the nonlinear behavior to the software (D I , D u , D r , D x , F y, and F r in Figure 7(a)), as well as the limit states to control the acceptance criteria in the walls and coupling beams, were captured from the generalized load-displacement curve, as illustrated in Figure 7(b) and the table related to the modeling parameters and control of acceptance criteria for the shear-control concrete components (ASCE41-17, 2017; Allouzi and Alkloub, 2017).…”

Section: Modeling the Nonlinear Behavior And Determination Of The Str...mentioning

confidence: 99%

A low computational cost seismic analyses framework for 3D tunnel-form building structures

Advances in Structural Engineering

Nikkhoo

Hajirasouliha

et al. 2022

Numerical modeling of tunnel-form buildings entails the utilization of 3D finite element models consisting of large numbers of shell and fiber elements. Accordingly, the non-linear analysis of such models under seismic excitations is both time-consuming and computationally expensive, especially in the case of large scale structures. To address this challenge, this study investigates the efficiency of the Endurance Time Method (ETM) to evaluate the structural responses, location of damage initiation, and the overall performance of tunnel-form structures under the Design Basis Earthquake (DBE) hazard level. Comparison with results derived from pushover and time-history analyses indicated the acceptable accuracy of ETM with significantly less computational efforts. The computation time required for the ETM was less than 25% of pushover (until total failure of the system) and time history analyses on the five- and ten-story tunnel-form buildings. The maximum differences between the results of ETM and time history analysis used to estimate the story drifts and shear forces were 4–6% and 1–4.5%, respectively. Considering the reliability of ETM and its appropriate accuracy, this method can be considered as a suitable alternative to the conventional methods to provide a low computational cost seismic analyses framework for non-linear tunnel-form buildings and similar structural systems.