Torsional Irregularity Research Articles

Study on earthquake induced torsional irregularity and lateral displacement of RC building with shear wall

Study on earthquake induced torsional irregularity and lateral displacement of RC building with shear wall

Towards an earthquake-resistant architectural design with the image classification method

ABSTRACT Architectural design is an interdisciplinary process which involves multiple stages that are interconnected. In this process, it is common for major decisions to be changed during the final stage, the analysis of the structural system. After making substantial corrections, the architect has to revisit the early stages, the preliminary project. This back-and-forth process can result in significant losses in time and cost. The proposed Irregularity Control Assistant (IC-Assistant) aims to provide architects with feedback on the conformity of structural system decisions to the irregularities defined in the Turkish Building Earthquake Code (TBEC-2018), using image processing methods at the early stages of the design process. The IC-Assistant was preliminarily created to evaluate the torsional irregularity of plan organization using deep learning methods. In this study, the results of the IC-Assistant were verified by structural analysis with the Prota-Structure program. The novelty of this study is the use of the image-classification method in earthquake-resistant architectural design. Up to this point, the method has been mainly used in facial recognition systems. This method minimizes time, human error, and cost losses and includes awareness of load bearing and earthquake resistance as inputs in the early stages of architectural design.

Optimum Design of Tuned Mass Dampers for Structures with Torsional Irregularity via Jaya Algorithm

Optimum Design of Tuned Mass Dampers for Structures with Torsional Irregularity via Jaya Algorithm

Structural Design and Analysis of a Super-High Building in Nanjing, China

This study analyzes a high-rise building with B-level height (i.e., a total height of 146.5 m) and a shear wall structure. Since the project contains many plane irregularities (including 1a torsional irregularity, 1b eccentric arrangement, and 2a plane convex irregularity), it should be treated as a super high-rise building. This study introduces the main characteristics and overrun conditions of the project and describes the structural design of the foundation and the basement, upper structural layout, force conditions under frequent, fortified, and rare earthquake actions, and structural performance-based objectives in detail. The following measures can be adopted to address the overrun problem. First, the floor at the thin waist of the structure was thickened to 150 mm and reinforced in the bilayer and bidirectional patterns, with a reinforcement ratio of no less than 0.25%. The damage condition on the floors under a great earthquake was analyzed. The vertical components at the waist were reinforced to constrain the extension of the edge components toward the top. Second, the structure’s peripheral stiffness was strengthened to enhance the anti-torsional performance and minimize the adverse effects on torsional irregularities. Third, using two software programs, the performance-based envelope design under medium earthquake action and dynamic elastoplastic analysis under great earthquake action were analyzed to ensure structural safety. Fourth, the edge components were constrained for the shear wall columns with axial-to-compressive stress strength ratios exceeding 0.3. For the overall structure and critical parts, force conditions under frequent, fortified, and rare earthquake conditions were calculated and examined with the SATWE, MIDAS GEN, and SAUSAGE software packages. The calculation results revealed that the structure shows favorable anti-seismic performance, with an overall anti-seismic C-level and a safe and reliable structure. The structural design method introduced in this article can promote the sustainable development of structural design.

A comparative study on the response of the L-shaped base isolated multi-storey building to near and far field earthquake ground motion

This study aims to understand the behaviour of a base isolated l-shaped building under far field and near field earthquake ground motion. A ten-storey l-shaped building was considered for the study and modelled using SAP2000, which is finite-element-based software. At first, a non-isolated model was created, and the required data was generated in order to develop an isolated model. After that, a non-linear time history analysis was performed, and the results of storey displacement, torsional irregularity, and base shear have been discussed for the base isolated model and the non-isolated model. The fundamental time period of base isolated l-shaped building was found to be 2.56 s while the base model had fundamental time period of 0.88 s. It was found in this study that higher peak ground acceleration (PGA) and peak ground velocity (PGV) of the ground motion led to higher storey displacement, storey drift, and base shear but a lower torsional irregularity ratio under near field ground motion, while torsional irregularity ratio of base isolated building was found to be increased under far field ground motion.

Optimal seismic design of multiple-rocking steel concentrically-braced frames in 3D irregular buildings

This paper presents a gradient-based optimization approach for the seismic design of multiple-rocking systems in irregular buildings. The proposed design method tackles general 3D buildings with high torsional and vertical irregularities is developed. The design problem is formulated as an optimization problem that minimizes the construction cost of steel self-centering concentrically braced frames. The constraints are formulated based on current seismic design code requirements and recommendations from the literature. The structural response is computed using nonlinear time history analyses of general 3D models subjected to ensembles of ground accelerations.A dual-phase optimization approach is developed to reduce the computational effort and improve convergence In the first phase, a simplified numerical model is adopted for the analyses while the topology of the framing elements is not optimized. The second phase adopts a more detailed numerical model and starts with fixed location of the rocking sections. This enables topology optimization of the framing elements as well. The design method was implemented for the design of an 8-story building with two setbacks and high torsional irregularities subjected to an ensemble of ground accelerations, each having three components. The results show that this method provides efficient designs of these complex systems with a reasonable computational effort.

Dynamic Analysis of the High Speed Train–Track Spatial Nonlinear Coupling System Under Track Irregularity Excitation

Track irregularity is the main factor that affects the safety and comfort of high-speed railway. It is important to study the influence of the track irregularity on the safety service of high speed train–track coupling system. In this paper, a vehicle–track spatial nonlinear coupled system dynamics model is developed with FEM. The model includes vehicle subsystem and track subsystem, which are coupled by wheel–rail interface. The vehicle subsystem is a 31-DOF spatial vehicle model, and the track subsystem is a three-dimensional slab track model composed of the rail, rail pad and track slab. Considering wheel tread profile and rail head profile, the wheel–rail spatial contact geometry relationship is established, and the “Trace method” and the “Minimum distance method” are used to search for wheel–rail contact points. Considering the nonlinear contact between the wheel and the rail, a numerical approach is presented, where the “Trace method” is embedded into the algorithm for solving the vehicle–track nonlinear coupling dynamics equation by cross iteration, realizing searching the wheel–rail contact points and solving the vehicle–track nonlinear coupling equation simultaneously, which greatly improves the efficiency of numerical analysis. As application examples, the dynamic responses of a high speed train–track spatial nonlinear coupled system excited by the track V-shaped local profile irregularity and the track torsional irregularity are analyzed. The results show that the algorithm is effective in solving the vehicle–track spatial nonlinear coupled system dynamics problem, and the track irregularity has significant influence on the dynamic response of vehicle and track structure.

Non-Linear Behavior of Reinforced Concrete Frame Structure with Vertical Irregularities

Various structural factors that contribute to damage during an earthquake are vertical irregularities, irregularities in strength and stiffness, mass irregularities, torsional irregularities, and so on. Over the past decade, performance-based design (PBD) procedures have become one of the most critical areas in earthquake engineering. The pushover procedure is divided into two parts; the first is the displacement target for the erected building. The target is the estimated displacement of the top of the building when exposed to the design earthquake excitation. Then a pushover analysis is carried out on the building until the top removal is equal to the target displacement. Second is the type of controlled force in which the total amount of force acting is estimated and applied to the structure, and analysis is carried out. The various performance levels for a building are expressed in terms of the base shear carried versus the roof displacement. If all the plastic hinges formed are within the CP limit, the structure is said to be safe. On the other hand, if the plastic hinge formed exceeds the CP limit, the structure is said to have collapsed. This paper proposes a 2D reinforced concrete frame with three models with variations of vertical irregularity. This paper aims to see the nonlinear behavior of reinforced concrete frames with vertical irregularities through the pushover method using SAP2000 software. Furthermore, the analysis results show that the skeleton is susceptible to increasing vertical irregularity. As the vertical irregularity increases, the percentage of the plastic hinge crossing the boundary increases. The analysis results also show that model 2 has better behavior.

Experimental investigation of gear rattle and nonlinear dynamic interaction in a dual-clutch transmission

Dual-clutch transmissions (DCT) having high efficiency and powershift are widely used in passenger cars thanks to the dual-clutch and preselection strategies. However, the dual-clutch transmission gear rattle behaviour still needs to be fully discovered, especially the influence caused by different preselection strategies. In this regard, the gear rattle sensitivity and dynamic evolution of the geartrain in a DCT were experimentally investigated on a rattle test bench and vehicle powertrain. The rattle response and instantaneous speed of all speed gears potentially contributing to the overall rattle are measured. The measured results from the DCT were compared with a similar structure six-speed manual transmission to depict its characteristics. Moreover, a multi-degree-of-freedom nonlinear torsional model was established to gain the nonlinear dynamic response along with the rising torsional irregularities; the model considers the crucial parameters affecting rattle behaviour. Two qualitative criteria were consequently given based on the numerical results and the law of the gear motion.The experimental results on the rattle test bench show that the DCT rattle behaviour varies with different preselected gears and is quite different from the manual transmission. The rattle sensitivity curves disclose an abrupt jump-up phenomenon when the excitation level reaches a certain level. The nominal input speed, preselection gear and lay-shaft configuration considerably determine the excitation level and amplitude increase of the jump-up on the rattle response. Based on the proposed qualitative criteria, a strongly nonlinear dynamic response is observed in the loaded gear pair under preselection conditions and deteriorates the rattle noise. A considerable dynamic interaction between active and passive sub-gearboxes is found. The appearance of the harmonics of the excitation frequency on the active input shaft that generates the high impact amplitude and density contributes to the jump-up and high vibration response on the rattle sensitivity. Finally, vehicle experiments reproduce the rattle jump-up and dynamic torsional interaction in the DCT powertrain are confirmed.

Performance-Based seismic design and evaluation of out-of-code structure on Nanjing Financial City

The main scope of performance-based seismic design and evaluation study focuses more on the seismic performance of the simple structure or the regular structure, instead of out-of-code structure. The C1 tower in Nanjing Financial City is taken as an engineering case study. Many design indexes of the original design scheme of the structure exceed the requirements of the existing Chinese specifications, such as the height exceed the limits, the torsional irregularity, the partial floor slab discontinuity etc., which are summarized in detail in this paper. Then, several special structural design strategies are adopted to improve the overall seismic performance of this out-of-code structure. For example, multiple lines of seismic defences are set and the outrigger trusses are strengthened to solve the height overrun. For torsion irregularity, the influence of the bidirectional seismic torsion effect is considered in the calculation. Finally, according to the results of dynamic elastoplastic time history analysis under rare earthquakes, the seismic performances of the out-of-code structure are evaluated in detail. The analysis results show that the overall seismic performances of the structure are all within a reasonable range, and the seismic performance of the main components in the structure all meet the specification requirements.

Seismic Fragility Assessment of Irregular High Rise Buildings using Incremental Dynamic Analysis

The construction of high rise buildings is common in city areas. These buildings may be irregular because of aesthetics or other requirements. As Nepal lies in a seismically active region these irregular high rise buildings may not perform well during earthquakes. Two existing irregular high rise buildings are taken as case study buildings that had pre-existing torsion. Shear walls are added to the building at the required location to minimize torsion in the buildings. The objective of the study is to determine the performance of building with and without torsional irregularity. The seismic performance of all the buildings is carried out by taking seven pairs of ground motions using nonlinear time history analysis. These ground motions are scaled to the required intensity to develop incremental dynamic analysis (IDA) curve. These IDA curves are used to develop fragility curves to access the performance in the buildings. The result from the analysis showed that performance in one building improved by 35% and in another by 70% at the peak ground acceleration (PGA) of 0.35g.

Reliability-based layout optimization of concentrically braced in 3D steel frames

For an economical and safe design of building systems with concentrically braced frames, the layout of the braces should be done by considering all limitations. The current study proposes an approach for a reliability-based optimal design of concentric bracing layouts in 3D steel frames. The objective function was considered to be a reduction in the total weight. The layout of the braces was considered as the variable of the optimization problem. The deterministic design constraints of limitations of strength, drift and torsional irregularities were considered according to AISC 360-16 and ASCE 7-16. The distance between the center of mass and the center of rigidity was defined as the probability constraint. The probabilistic variables were the intensity of the distributed loads and the cross-sectional area of the braces and columns. The reliability index was evaluated using the Monte Carlo simulation method. The reliability-based design optimization (RBDO) problem was solved for 4-, 5- and 9-story steel space frames using the EVPS algorithm. To investigate the effect of the probabilistic constraint on the optimal design, numerical examples were solved without applying this constraint and the solutions to the RBDO and deterministic design optimization problems were compared.

Analysis of irregular multistorey buildings with and without floating columns under seismic loading

Floating column is a vertical structural member that rests on the beam. Floating column is advantageous to provide large open space in a building, but it is disadvantageous in earthquake conditions. On the other hand, by the advancements in civil engineering knowledge, architects try to adopt irregular shapes of buildings. Providing floating columns in irregular buildings is a challenging issue for civil engineers they should deal with. That’s why study of application of floating column in irregular buildings is one of the important topics in modern civil engineering. This study focuses on analysing the seismic behaviour of G + 10 irregular buildings considering floating columns and without floating columns to compare with a regular building. The building models are analysed in ETABS V19 software, then analytical findings are explained in terms of (maximum storey drift, maximum storey displacement, and torsional irregularity). From the study it is found that providing floating columns in irregular buildings increase storey drift and storey displacement significantly. Similarly, the torsion increases in buildings when the floating columns are not provided symmetrically.

DETERMINATION OF BUILDINGS WITH TORSIONAL IRREGULARITY BY ARTIFICIAL INTELLIGENCE METHODS

Reinforced Concrete (RC) frame buildings with shear wall are widely used in severe seismic zones. Shear walls are bearing system elements that provide the greatest resistance against hori-zontal force under the effect of the earthquake, limit displacements, and prevent torsions. A re-inforced concrete shear wall is one of the most critical structural members in buildings, in terms of carrying lateral loads. However, irregular layouts cause torsional irregularity in buildings. For this purpose, different shear wall frame reinforced concrete building models are designed. The model buildings have a regular formwork plan. The shear wall layout has different variations in each plan. These structure plans were mainly classified into two classes according to their tor-sional irregularities as structures with torsional irregularities and Structures with non-torsional ir-regularities. Artificial intelligence (AI) has revolutionized industries such as healthcare, agricul-ture, transportation, and education, as well as a variety of structural engineering problems. Arti-ficial intelligence is transforming decision-making easier and reshaping building design process-es to be smarter and automated. Artificial intelligence technology of learning from an existing knowledge base is used to automate various civil engineering applications such as compressive strength estimation of concrete, project pre-cost and duration, structural health monitoring, crack detection, and more. In this study, it is aimed to determine the structures with torsional irregulari-ty using artificial intelligence methods. Besides, the study is expected to introduce and demon-strate the capability of Artificial intelligence-based frameworks for future relevant studies within structural engineering applications and irregularities.

Numerical Analysis and Validation of Irregularity in Moment Frame Structure Due to Varying Location of Tuned Mass Damper

Abstract: Within the construction industry, the number of higher and lighter structures that are adaptable and have a low damping value has been steadily increasing in recent years. Those constructions will simply fail as a result of earthquake and wind-induced structural vibrations. There are a variety of approaches available today to reduce structural vibration, and one of the oldest is the use of dampers. The tuned mass damper is tuned to the structural frequency of the structure if the stiffness and damping values are kept constant. The main goal is to investigate the mass and torsional irregularity in the structure. This study is divided into two phases - first phase involves the investigation and validation of structure having tuned damper with varying location along the height of building. The second phase involves the location of tuned mass damper with the plan projection of the building. Non-Linear Time history analysis is used to identify the behavior of frame elements in the structure based on considered cases using ETABS. The parameters such as displacement was evaluated. The result shows that the dampers should be carefully placed in order to tune the frequency of the structure.

Torsional Improvements in a Multistoried Building with Plan Irregularities

Irregular buildings consist of large number of modern urban structures. Though some buildings look symmetrical in plan might have irregular distribution of mass, strength and stiffness along the plan and height of the buildings. In common sense, a building with a regular geometry is supposed to be regular building. While the building is designed to be used for different functions along the building area and along the building plan the presence of opening, staircase positioning and positioning of the shear/core wall for different purpose like lift and HVAC (Heating, Ventilation and Air Conditioning) leads to the irregularity in the plan. Ultimately, torsion irregularity occurs, which if remains not taken care properly may create substantial damage of the building structures. The purpose of this study is to determine the conditions for excessive torsional irregularity and solve them with the proper positioning of the shear wall to counter the torsional behavior of the building. A linear response analysis was conducted and the studied structures were both six- storey buildings. First building has opening left for different purpose like lift and HVAC systems. While the second building has shear wall for lift at the edge of the building. Though both buildings seem fine with their geometrical orientation after the analysis torsional irregularity was evident. The proper placement of the shear wall has been used to stiffen the building to counter for the torsional modal and make to regular in terms of the mass and stiffness distribution.

Experimental assessment of proposed seismic strengthening scheme for adobe structures

A new scheme of seismic strengthening of adobe structures has been proposed in this paper. The scheme involves horizontal and vertical bands of steel wire mesh plastered with cement-sand mortar. The effectiveness of the proposed scheme is assessed by dynamically testing a half-scale model of the adobe structure on a shaking table. The acceleration time history record of the 1995 Kobe earthquake was used to simulate the ground motion for the strengthened model which was increased sequentially in increments of 25% of peak ground acceleration (PGA). Initial (hairline) cracks were observed in the in-plane wall of the model at a PGA of 0.439 g. Although the out-of-plane walls also sustained damages, the in-plane walls were the most damaged parts of the structure. The proposed strengthening method reduced the torsional irregularity of the structure. It also increased strength, ductility and energy dissipation capacities of the walls. The data of observed structural damages and building drift were used to propose four performance levels for the strengthened adobe structures corresponding to the applied PGAs of ground motion.

IDA analysis of regular and irregular seismically isolated structures in different stories and different seismic categories

The effect of superstructure stiffness, types of plan irregularities, and kinds of seismic categories on the behavior of isolated structures by nonlinear dynamic analysis has been investigated. Incremental nonlinear time history of base isolated structures with different types of irregularities, seismic categories, and at different elevation levels with different superstructure stiffness is the main purpose of this study. In this regard, 72 structures from 8 to 32 floors with regular and irregular spindle-shaped plans were analyzed in seismic design categories C and D (According to ASCE07). The buildings had basements, and the rest were on the ground. Furthermore, in isolated structures, the stiffness of the superstructure was considered once in normal condition (that satisfied the main criteria of drift control and strength design), and once 10 times on average (to achieve higher stiffness). The incremental dynamic analysis (IDA) results showed that in all the cases, along with a noticeable reduction in acceleration and relative lateral displacement of the floors, the response modification factor of the structures was higher than what was considered in the design. In all the studied structures, the plastic joints formed within the immediate occupancy (IO) range. In 10 times stiffened structures, the roof acceleration decreased in all isolated structures. Also, in isolated structures, plan and torsional irregularities did not remain especially in 10 times stiffened isolated structures.

Parametric analysis of the whole loading process of translation-torsion coupled vibration characteristics of the multi-layer bi-directional eccentric frame structure

1. Alaa K.M., El-Kashif K.F., Salem H.M., 2022, New definition for torsional irregularity based on floor rotations of reinforced concrete buildings, Journal of Engineering and Applied Science, 69, 1, 1-35. CrossRef Google Scholar

Structural Resistance of a Reinforced Concrete Building under Earthquake and Wind Loads in Isparta and Burdur Region

It has been clearly seen from building experiences and studies that lateral load effects such as earthquake load and wind load make building irregularities more obvious. Hence, it is of great importance to evaluate the regularity of the structural systems in accordance with the conditions determined by the building regulations. In this paper, irregularity effects were investigated according to Turkish Building Earthquake Regulation (TBEC) 2018. A reference building which have vertical setback irregularity were analzed under earthquake and wind loads. Etabs software were used for structural analyses. Response spectrum method were used for the seismic analysis and TS498 for Wind load analysis. Effective relative storey drift, A1 –Torsional irregularity and B2 –Soft Storey Irregularity are comparatively investigated and Irregularity values were determined.