• Structural Monitoring and Maintenance
• /
• 제11권2호
• /
• pp.101-126
• /
• 2024

To avoid irregularities in buildings, design codes worldwide have introduced detailed guidelines for their check and rectification. However, the criteria used to define and identify each of the plan and vertical irregularities are specific and may vary between codes of different countries, thus making their implementation difficult. This short communication paper proposes a novel approach for quantifying different types of structural irregularities using a common parameter named as unified identification factor, which is exclusively defined for the columns based on their axial loads and tributary areas. The calculation of the identification factor is demonstrated through the analysis of rectangular and circular reinforced concrete models using ETABS v18.0.2, which are further modified to generate plan irregular (torsional irregularity, cut-out in floor slab and non-parallel lateral force system) and vertical irregular (mass irregularity, vertical geometric irregularity and floating columns) models. The identification factor is calculated for all the columns of a building and the range within which the value lies is identified. The results indicate that the range will be very wide for an irregular building when compared to that with a regular configuration, thus implying a strong correlation of the identification factor with the structural irregularity. Further, the identification factor is compared for different columns within a floor and between floors for each building model. The findings suggest that the value will be abnormally high or low for a column in the vicinity of an irregularity. The proposed factor could thus be used in the preliminary structural design phase, so as to eliminate the complications that might arise due to the geometry of the structure when subjected to lateral loads. The unified approach could also be incorporated in future revisions of codes, as a replacement for the numerous criteria currently used for classifying different types of irregularities.

• Structural Engineering and Mechanics
• /
• 제90권1호
• /
• pp.41-49
• /
• 2024

In recent years, China's high-speed railway (HSR) line continues to expand into seismically active regions. Analyzing the features of earthquake rail irregularity is crucial in this situation. This study first established and experimentally validated a finite element (FE) model of bridge-track. The FE model was then combined with earthquake record database to generate the earthquake rail irregularity library. The sample library was used to construct a model of desired earthquake rail irregularity based on signal processing (SFT) and hypothesis principle. Finally, the effects of random pier height and random span number on desired irregularity were analyzed. Herein, an equivalent method of calculating earthquake rail irregularities for random structures was proposed. The results of this study show that the amplitude of desired irregularity is found to increase with increasing pier height. When calculating the desired irregularity of a structure with unequal pier heights, the structure can be regarded as that with equal pier heights (taking the largest pier height). For a structure with the span number large than 9, its desired irregularity can be considered equal to that of a 9-span structure. For the structures with both random pier heights and random span number, their desired irregularities are obtained by equivalent calculations for pier height and span number, respectively.

• Advances in concrete construction
• /
• 제7권3호
• /
• pp.131-141
• /
• 2019

Irregular distribution of mass in elevation is regarded as a structural irregularity by which the modes with high energy levels are excited and in addition, it can lead the structure to withstanding concentration of nonlinear deformations and consequently, suffer from unpredictable local or global damages. Accordingly, with respect to the lack of knowledge and insight towards the performance of concrete buildings making use of tunnel-form structural system in seismic events, it is of utmost significance to assess seismic vulnerability of such structures involved in vertical mass irregularity. To resolve such a crucial drawback, this papers aims to seismically assess vulnerability of RC tunnel-form buildings considering effects of irregular mass distribution. The results indicate that modal responses are not affected by building's height and patterns of mass distribution in elevation. Moreover, there was no considerable effect observed on the performance levels under DBE and MCE hazard scenarios within different patterns of irregular mass distribution. In conclusion, it appears that necessarily of vertical regularity for tunnel-form buildings, is somehow drastic and conservative at least for the buildings and irregularity patterns studied herein.

• Computers and Concrete
• /
• 제14권4호
• /
• pp.405-417
• /
• 2014

The poor seismic performance of reinforced concrete buildings during the latest earthquakes has become a serious issue in the building industry in Turkey. This case, designing new buildings without structural irregularities against earthquake loads reveals to be quite significant. This study mainly is focused on the effects of different torsional irregularities on construction costs and earthquakes performance of reinforced concrete buildings. In that respect, structural torsional irregularities are investigated based on the Turkish Earthquake Code. The study consists of major eight main parametric models. In this models consist of totally 49 models together with the variations in the number of storey. With this purpose, the earthquake performances and construction costs (especially steel quantities) of reinforced concrete buildings which having different structural torsional irregularities were obtained with the help of Sta4-CAD program. Each model has been analyzed by both the methods of equivalent earthquake loading and dynamic analysis. The obtained results reveal that the model-1 which has lower torsional irregularity coefficient shows the best earthquake performance owing to its regular plan geometry. Also, economical comparisons on costs of the torsional irregularity are performed, and results-recommendations are given.

• Structural Engineering and Mechanics
• /
• 제74권5호
• /
• pp.699-709
• /
• 2020

Torsional irregularity is one of the most probable types of horizontal irregularity and existence of this irregularity in most of the structural loading codes is determined by calculating the ratio of the maximum to the average story drift. No specific method has been previously recommended by the codes to calculate the mentioned ratio in the response spectrum analyses. In the current investigation, nine steel building structures with different plan layouts and number of stories have been analyzed and designed in order to evaluate the efficiency of three methods for calculating the ratio of the maximum to the average story drift in the response spectrum analyses. It should be noted that one of these methods is the approach used by current version of ETABS software andother ones are proposed in this paper. The obtained results using the proposed methods are compared with the time history analysis results. The comparisons show that one of these methods underestimates the mentioned ratio in all studied models, however, the other two methods have shown similar results. It is also found that the plan layouts and irregularities can affect how these methods estimate the ratios compared to those obtained by the time history analysis. Generally, it can be concluded that all of these methods can properly predict the ratio with acceptable errors.

• Architectural research
• /
• 제24권2호
• /
• pp.53-61
• /
• 2022

Irregularities in the structure are crucial factors in screening structural vulnerability under extreme loadings. Numerical analyses were carried out considering wind and seismic loadings for four structures with discrete irregularity: continuous and discontinuous beams with varied story levels, and L-shaped irregular buildings. Structural responses such as maximum displacements, bending moments, axial forces, torsions, and story drifts are evaluated as per the criteria and limits defined by ACI 318. The outcomes indicate that the frame system with beam discontinuity on the upper half of the height exhibits the best structural performance. The results also indicate that the asymmetrical design of the L-shaped model makes it more susceptible to damage when subjected to strong lateral loading conditions.

• 대한건축학회논문집:구조계
• /
• 제35권10호
• /
• pp.191-198
• /
• 2019

In this paper the evaluation scheme for determining torsional irregularity of Hanok has been proposed. The proposed method can evaluate torsional irregularity of Hanok easily only with characteristics of Hanok shapes, arrangement of lateral load resisting frames and their lateral stiffness without time consuming and complicate 3-dimensional structural analysis. The proposed formula is expressed as allowable maximum eccentricity, and torsional irregularity is evaluated by comparing this value with actual eccentricity. The applicability of the proposed scheme was evaluated by applying it to the line shape plan Hanok with two symmetrically arranged walls and the result was expressed by formula and graph. The results showed that the allowable maximum eccentricity is 10% of plan dimension perpendicular to the seismic load when the walls are placed at the extreme end. The proposed formula was expressed as a generalized formula so it can be applied generally to the various plan shape and wall arrangement of Hanok.

• Structural Engineering and Mechanics
• /
• 제14권2호
• /
• pp.237-243
• /
• 2002

It is well known that torsionally unbalanced buildings are more vulnerable to earthquake hazards than are the regular structural systems. In this paper, a parametric investigation is presented, in order to observe the amplification in the internal forces, when increased eccentricities are used instead of the ones corresponding to the 5% accidental eccentricity. A series of five, ten-story framed and walled structures, with rather high torsional irregularity coefficients, are selected and a numerical test procedure is applied. Numerical results show that the maximum amplification in the internal forces at the most critical beams and columns at the flexible sides of the structures is about 10%. It is concluded that, more serious measures in the codes are needed in the case of this rather dangerous type of irregularity.

• 한국전산구조공학회논문집
• /
• 제25권4호
• /
• pp.331-338
• /
• 2012

현재 국내에서 EM-120에 의해 검측된 틀림 데이터는 매우 불규칙적인 형태를 나타내며 데이터 분석 시 다양한 문제점을 가지고 있다. 본 연구에서는 궤도의 효율적인 유지관리를 위해 검측된 틀림데이터의 특징과 문제점을 분석하고, 이를 보완할 수 있는 효율적인 처리 기법을 개발하였으며, 정제된 데이터의 ARIMA 분석을 통해 검측데이터와 계절 변화의 상관관계 분석을 수행하였다. 또한 회귀모형, 지수평활법, ARIMA 모형 등 다양한 예측 모델의 적용을 통해 검측 데이터의 시계열 분석을 수행하고, 궤도 틀림 데이터의 예측 모델에 적합한 최적 모델 선정과 관련한 연구를 수행하였다.

• Earthquakes and Structures
• /
• 제26권5호
• /
• pp.349-361
• /
• 2024

Excessive torsional behaviour is one of the major reasons for failure of buildings, as inferred from past earthquakes. Numerous seismic codes across the world specify a displacement-based or drift-based criterion for classifying buildings as torsionally irregular. In recent years, quite a few researchers have pointed out some of the inherent deficiencies associated with the current codal guidelines on torsional irregularity. This short communication paper aims to envisage the need for a revision of the displacement-based guidelines on torsional irregularity, and further highlight the appropriateness of a rotation-based criterion. A set of 6 reinforced concrete building models with asymmetric shear walls are analysed using ETABS v18.0.2, by varying the number of stories from 1 to 9, and the torsional irregularity coefficient of various stories is calculated using the displacement-based formula. Since rotation about the vertical axis is a direct indication of the twist experienced by a building, the calculated torsional irregularity coefficients of all stories are compared with the corresponding floor rotations. The conflicting results obtained for the torsional irregularity coefficients are projected through five categories, namely mismatch with floor rotations, inconsistency in trend, lack of clarity in incorporation of negative values, sensitivity to low values of displacement and error conceived in the mathematical formulation. The findings indicate that the irregularity coefficient does not accurately represent the torsional behaviour of buildings in a realistic sense. The Indian seismic code-based values of 1.2 and 1.4, which are used to characterize buildings as torsionally irregular are observed to be highly sensitive to the numerical values of displacements, rather than the actual degree of rotation. The study thus emphasizes the revision of current guidelines based on a more relevant rotation-based or eccentricity-based approach.