Bay Width Research Articles

Influence of Vertical Geometric Irregularities of Reinforced Concrete Buildings on the Time Period for Different Bay Widths and Building Heights

Influence of Vertical Geometric Irregularities of Reinforced Concrete Buildings on the Time Period for Different Bay Widths and Building Heights

Seismic performance assessment of concentrically braced steel frames designed to the Turkish Building Earthquake Code 2018

The Turkish Building Earthquake Code 2018 (TBEC 2018) came into force in 2019 and superseded the previous code, the Turkish Earthquake Code 2007 (TEC 2007). Compared to TEC 2007, TBEC 2018 includes new design approaches as well as significant changes in the design of steel structures which are likely to notably affect the seismic design and performance of concentrically braced frames (CBFs). This study aims to quantify the seismic performance of CBFs designed to TBEC 2018. To this end, a set of archetypes was designed, covering a wide range of building heights, bay widths, and seismic hazard levels. Nonlinear numerical models of the archetype buildings were built to perform nonlinear static and dynamic analyses. The seismic performance assessment framework outlined in FEMA P-695 was adopted. The effects of build height, bay width, and seismic hazard levels were investigated and reported. The results of the study revealed that CBFs located in moderate-seismic regions showed acceptable performance while CBFs designed to TBEC 2018 performed poorly in high-seismic regions.

Development of a loading protocol for long links in eccentrically braced frames

Loading protocols are generally used for qualification testing of structural members. In eccentrically braced frames (EBFs), the connections of short links attached to columns are evaluated based on the loading protocol given in the AISC Seismic Provisions for Structural Steel Buildings (AISC 341–16). Behavior of many short links without column attachments was also investigated by making use of this loading protocol. The AISC341 loading protocol is suitable for only short links and does not take into account the one-sided nature of link rotation angle (LRA) demands due to mean effects. Long link behavior differs from short link behavior in a sense that long links are subjected to strength and stiffness degradation due to local buckling effects. A nonsymmetrical loading protocol for long links was developed as a part of this study. Twenty-four long link EBF archetypes with variable floor plans, bay widths, number of stories and link length to bay width (e/L) ratios were designed according to the US standards. The responses of EBFs under maximum considered earthquake (MCE) and collapse level earthquake (CLE) were obtained by making use of numerical analysis employing degrading link models. The link rotation angle time histories were reduced and converted into a series of cycles and the peaks of the LRA response were identified by using the rainflow counting algorithm. The nonsymmetrical loading protocol was represented as a function of maximum rotation range, which depends on the seismic hazard and e/L ratio.

Seismic performance evaluation of eccentrically braced frames with long links using FEMA P695 methodology

Short links that primarily yield under shear are usually preferred in eccentrically braced frames (EBFs) due to their high rotation and energy dissipation capacities. Long links that yield under flexure can be used in cases where large openings are required for architectural reasons. Research conducted in the past showed that the seismic response factors recommended in ASCE7 result in designs with higher collapse probabilities than expected for EBFs with shear links. Long link behavior differs from the behavior of short links because the former is governed by flexure and subjected to significant amounts of strength and stiffness degradation. A numerical study was undertaken to evaluate the seismic response factors for EBFs with long links using FEMA P695 methodology. Twenty-four EBF archetypes were designed by considering the bay width, number of stories, the link length to bay width (e/L) ratio and column base condition as the variables. Performances of these archetypes were evaluated under maximum considered earthquake (MCE), and collapse level earthquake (CLE). The effects of degradation were studied by considering degrading and non-degrading responses separately. The results showed that strength and stiffness degradation increases the link rotation angle as much as 46 percent when compared with the non-degrading models. The recommended response factors were found to provide acceptable performance for e/L = 0.5, when 20% probability of collapse is considered under MCE level events. Remedial measures were investigated to achieve acceptable performance for collapse probability of 10% under MCE level events.

Analysis and cost comparison of framed structure using different building materials under different load combinations

In the present study, the analysis and cost comparison of framed structures using different building materials under different load combinations were carried out. G + 7 storey framed structure of 24 m high was analysed for 8 load cases and 4 different load combinations. The bay width was maintained as 4 m in both directions (16 m × 16 m) and analysis was achieved through the licensed version of STAAD.Pro CONNECT V22. The material properties assigned were concrete, steel, and steel-concrete composite. The total cost of material utilised was calculated, with reference to the unit costs mentioned in the Standard schedule of rates. The cost comparison was carried out for each type of material under different load cases and different load combinations. It was observed that under extreme load combination, the concrete frame showed the increase in cost of 77%. Whereas the corresponding increase in steel-concrete composite frame and steel frame were 62% and 50% respectively. Even though the initial cost of steel structures is high, these structures were found to be optimal with less increment in cost under extreme load combinations.

Rapid seismic damage-state assessment of steel moment frames using machine learning

The damage state assessment of buildings after an earthquake is an essential and urgent task that typically requires significant manpower and time for the resilience of a city-scale society. This study aims to develop machine learning (ML) models for the rapid seismic damage-state assessment of steel moment frames, which was never tried before to the authors’ knowledge. Eight ML models were examined for this purpose, including K-nearest neighbors, naïve Bayes, decision tree, random forest (RF), adaptive boosting (AdaBoost), extreme gradient boosting (XGBoost), light gradient boosting, and category boosting. The combination of 468 steel moment frames from the database in DesignSafe cyberinfrastructure and 240 ground motions yielded a total of 112,320 data points. The steel moment frames have a wide variety of geometric configurations (e.g., number of stories from 1 to 19, number of bays from 1 to 5, bay width from 6.1 to 12.19 m), and applied loads (i.e., three cases of dead load and two cases of live load). Nonlinear time history analyses were conducted using OpenSees to produce a comprehensive dataset for the training and testing of the ML models. A reliable procedure to define the damage states of steel moment frames was suggested based on pushover analysis. Damage states of steel moment frames were categorized following the tag definitions (i.e., green, yellow, and red) in ATC-20. Spectral accelerations at five selected periods (1, 2, 3, 4, and 5 s) for the given ground motions and at the first three natural periods of the steel frames were used as input variables for the ML models. From the results, the RF model is suggested for the prediction of the seismic damage states of steel moment frames. The RF model could accurately predict 98% of the assigned tags in the testing dataset. In contrast, the AdaBoost (88%) and naïve Bayes (90%) models displayed the lowest performance. Among the four boosting methods considered, the XGBoost model (97%) exhibited the highest performance. Furthermore, Shapley additive explanations (SHAP) method was used to inspect the importance of input variables on the prediction. It was found that the spectral accelerations at 1 and 2 s strongly influence the prediction, likely because the first natural periods of the considered steel frames fall in the range of 1–2 s. Finally, to provide convenient access to engineers, a graphical user interface based on the developed RF model was created. This study places a pioneering step for the application of machine learning to the rapid damage assessment of building structures.

Rethinking the Proportional Design Principles of Timber-Framed Buddhist Buildings in the Goryeo Era

This study examines how the wooden architecture of the Goryeo Dynasty in Korea evolved in an original way while incorporating Chinese architectural principles. For the Goryeo Era’s timber-framed buildings, eave purlin height was determined according to √2H times the eave column height (H), while the eave column height influenced the proportional location of each purlin, determined by the √2H times decrease rate in the cross-section. Thus, eave column height was proportionately connected to a geometric sequence with a common ratio of √2H. This technical approach, achieved using an L-square ruler and a drawing compass, contributed to determining eave purlin and ridge post placement, bracket system height, and outermost bay width. This study notes that the practical works were consistently preserved in East Asian Buddhist architecture, in that a universal rule of proportion was applied to buildings constructed during the Tang–Song and the Goryeo Dynasties, surmounting differences in local construction methods. These design principles were a vestige of socio-cultural exchange on the East Asian continent and a minimal step toward the establishment of structurally safe framed buildings.

Effects of cyclic strain hardening on performance of eccentrically braced frames

Performance based seismic design (PBSD) procedures have been developed in recent years. Studies conducted in the past revealed that strain hardening ratio (SHR) used in numerical modeling can be influential on the performance of steel structural systems. In this paper, the effects of SHR on the performance assessment of eccentrically braced frame (EBF) buildings were studied by using FEMA P-58 methodology. The numerical model was validated using the pseudo-dynamic test results of the DUAREM structure. Seismic performance of six archetype EBFs with different number of stories and link length to bay width (e/L) ratios were evaluated under design basis earthquake (DBE), maximum considered earthquake (MCE), and collapse level earthquake (CLE). Irreparable residual drift, repair cost and unsafe placards were calculated for SHR ranging between 0 and 0.01. The results showed that the residual interstory drift ratio is more influenced by the SHR when compared with the interstory drift ratio, link rotation angle and story acceleration. The replacement decision was found to depend on the SHR, the number of stories, the e/L ratio, and the seismic hazard. Under MCE and CLE level events, almost all of the archetypes with SHR ≤ 0.003 required replacement while replacement can be avoided for some of the archetypes with SHR > 0.003. Under DBE level events, 3-story archetypes and 6-story archetypes with SHR ≥ 0.002 did not require replacement. Nine-story archetype with e/L = 0.08 required replacement for SHR = 0 only, while archetypes with e/L = 0.12 required replacement for SHR ≤ 0.003. The study demonstrated the strong influence and sensitivity of the repair cost to the SHR.

Optimization of Diagrid Angle for High Rise Structure for Varying Bay Widths

The development of urban population, the lack of space and the high land costs has created the scope and necessity for the high-rise structures. In high rise structures, the design of lateral load resisting systems is more crucial than gravity load resisting system. There are many structural systems exists in literature to resist lateral loads. Diagrid structure is one among them which is proven to be both structurally and architecturally efficient structural system to resist lateral loads. The present study aims to investigate the best bay spacing for a particular high-rise structure and also optimizing the best diagrid angle to suit to the selected bay spacing. A numerical study is carried out with a 24 storied high-rise structure of plan area 36m x 36m considering with and without corner columns. The structure performance is checked with a bay width of 4m and with a bay width of 6m. Each structure is analyzed for four angles of inclinations of diagrid are formed by connecting 1, 2, 3, 4 stories respectively to optimize the diagrid angle. A comparative investigation is carried out for the structural responses like storey displacement, storey drift and base shear with different diagrid angles and with different bay width.

Blockage Probability Modeling of Large Wood at Reservoir Spillways With Piers

AbstractLarge wood increases the morphological and hydraulic complexity of rivers, yet it may block and modify the flood discharge capacity of hydraulic structures. To assess the related risk, blockage probability estimation for hydraulic structures such as reservoir spillways is needed. This work presents unstudied parameters for blockage of large wood with a reservoir‐type approach flow, where the inflow velocity has a negligible magnitude. Experiments were conducted in a channel with an ogee crested spillway equipped with piers, representing a commonly used hydraulic structure. Artificial stems were used to systematically evaluate the influence of stem length and stem draft on the blocking process. Different hydraulic conditions were evaluated by changing the water level in the reservoir. The head at the spillway crest with respect to stem draft was found to be a key parameter for blockage probability estimation at a spillway. Additionally, stem length was related to the bay width in the estimation of blockage. Larger heads tend to reduce the blocking probability of large wood, for a given stem draft, while increasing the relative stem length tends to increase the blocking probability. A logistic regression model is provided to estimate large wood blockage probability at ogee crested spillways with piers. Finally, recommendations for engineering practice are presented.

Modeling and analysis of a pin jointed plane frame using Biomimicked structural elements

Biomimicry can be termed as the concept that involves the imitation of models, systems and elements of the nature to solve complex human problems. When compared to the conventional techniques, it is an efficient, innovative and sustainable way and thus has scope in future. The various levels in biomimicry are utilized in the construction of the structures inspired from the nature thus paving way to innovation and sustainability. Various information can be learnt from nature when it comes to solving our challenges in a sustainable way. Nature builds to shape, because shape is cost effective and it minimizes the expenditure on materials while maximizing the effectiveness to achieve the desired functions. In this study the analysis of the conventional pin jointed plane frame is done first using STAAD. Pro to identify the compression and tension members in the frame. The various conventional frame models are modelled and analyzed. The finite element analysis is done using ANSYS 2020R2. A conventional pin jointed plane frame of height 4 m, bay width 4 m and strut length of 5.66 m were analyzed to know its member properties. A conventional pin jointed frame with horizontal springs provided at both the sides of the frame was modelled and analyzed. The optimized mimicked members are assembled to form the mimicked frame and analyzed. The various parameters such as total deformation, directional deformation, normal stress, equivalent stress, maximum principal stress and minimum principal stress were compared for the pin jointed plane frames. The present study helps in the reduction of material usage and self-weight of elements thus resulting in a sustainable and efficient structure

Effect of sequential earthquakes on evaluation of non-linear response of 3D RC MRFs

Most of the existing seismic codes for RC buildings consider only a scenario earthquake for analysis, often characterized by the response spectrum at the specified location. However, any real earthquake event often involves occurrences of multiple earthquakes within a few hours or days, possessing similar or even higher energy than the first earthquake. This critically impairs the rehabilitation measures thereby resulting in the accumulation of structural damages for subsequent earthquakes after the first earthquake. Also, the existing seismic provisions account for the non-linear response of an RC building frame implicitly by specifying a constant response modification factor (R) in a linear elastic design. However, the 'R' specified does not address the changes in structural configurations of RC moment-resisting frames (RC MRFs) viz., building height, number of bays present, bay width, irregularities arising out of mass and stiffness changes, etc. resulting in changed dynamic characteristics of the structural system. Hence, there is an imperative need to assess the seismic performance under sequential earthquake ground motions, considering the adequacy of code-specified 'R' in the representation of dynamic characteristics of RC buildings. Therefore, the present research is focused on the evaluation of the non-linear response of medium-rise 3D RC MRFs with and without vertical irregularities under bi-directional sequential earthquake ground motions using non-linear dynamic analysis. It is evident from the results that collapse probability increases, and 'R' reduces significantly for various RC MRFs subjected to sequential earthquakes, pronouncing the vulnerability and inadequacy of estimation of design base shear by code-specified 'R' under sequential earthquakes.

Pushover Response of Multi Degree of Freedom Steel Frames

Seismic codes use the behaviour factor to consider the ductility and the structure's non-linearity to improve the system's overall performance. Generally, Steel moment-resisting frames are characterized by a relatively high period showing high deformability and, foreseen that with stringent damageability criteria, the adopted behaviour factor might not optimally be utilized for achieving better performance of the frames. The design is generally governed by stiffness, leaving behind a complex structural system where the capacity design rules are disturbed and therefore necessitates to relax the drift limits for such frames. Given this and with extensive parametric analysis, the current paper aims to examine the behaviour factor of steel Moment Resisting Frames (MRFs). The parametric analysis has been conducted on rigid steel MRFs of 9, 7, and 5 storeys with bay 4 different bay widths of 9.15 m, 7.63 m, 6.54 m, and 5.08 m. Perimeter frame configuration has been designed using 4 different behaviour factors (q = 6.5, 4, 3, and 2) for a total number of 144 cases. Static nonlinear analysis has been conducted, and consequently, the behaviour factors have been examined. It has been observed that compatibility is required while choosing the drift limit for an assumed ductility class of the code. Doi: 10.28991/cej-2020-SP(EMCE)-08 Full Text: PDF

Quantification of Seismic Performance Factors for Ductile Vierendeel Steel Truss Moment Frames

ABSTRACT This study is focussed on the collapse performance assessment of steel truss moment frames (STMFs) with Vierendeel panels. The main parameters varied in this numerical study are the height of structures, bay width, aspect ratio of special segments, and number of ductile panels within the special segments. Incremental dynamic analyses are performed on twenty number of STMF archetypes having the overall height and aspect ratio of special segments exceeding the limiting values recommended in the current design codes. Based on findings of this study, seismic performance factors, namely, overstrength factor, response modification factor, and deflection amplification factor for STMFs are recommended.

Frequency-dependent amplification of the Sanriku tsunamis in Ryori Bay

In the present study, the local tsunami amplification observed in Ryori Bay, located on the Sanriku coast of Japan, was investigated using numerical simulations. Large-scale tsunami propagation simulations and tsunami inundation simulations for the bay were systematically conducted to estimate and model the 2011, 1933, and 1896 tsunamis that occurred off the Sanriku coast and which resulted in large run-ups. The simulation results, which are moderately consistent with observations, presented larger run-up heights and inundations for the 1933 and 1896 tsunamis (which followed relatively small earthquakes) compared to those of the 2011 tsunami (which followed a larger earthquake). Furthermore, the frequency analysis indicated that the former two tsunamis comprised higher predominant components. A tsunami inundation simulation using parametrized synthetic waveforms was conducted to identify the contributing factors associated with the large amplification and run-ups. The results indicated that the predominant components are significantly amplified in the bay and the initial decrease in the water surface elevation prior to the primary waves of the two tsunamis leads to an increase in their run-up heights. Furthermore, the simulated waveforms of the tsunamis revealed that the 1933 and 1896 tsunamis had their wavefronts changed into a steep wavefront, i.e., a bore-like wave, during their wave developments in the bay, attributed to shoaling, narrowing bay width, and the nonlinear effect of the wave. These results, therefore, indicate that bores which are known to generate large run-up heights were generated in the bay during the two tsunamis.

Nonsymmetrical loading protocols for shear links in eccentrically braced frames

SummaryThe AISC Seismic Provisions for Structural Steel Buildings (AISC 341‐16) provide a testing protocol for qualification of link‐to‐column connections in eccentrically braced frames (EBFs). This symmetrical testing protocol was developed by conducting nonlinear time history analysis on representative EBFs designed according to the International Building Code. Although the testing protocol is intended for qualification of link‐to‐column connections, many research programs have employed this recommended protocol for testing of shear links. Recent numerical investigations on constructed EBFs and archetype models showed that links can be subjected to one‐sided loadings with significantly higher link rotation angles than the codified limits. A numerical study has been undertaken to develop nonsymmetrical loading protocols for shear links in EBFs. Pursuant to this goal, 20 EBF archetypes were designed according to the ASCE7‐16 standard. The main parameters investigated were the link length to bay width ratio (e/L), number of stories, type of EBF, and the ground motion level. The archetypes were subjected to maximum considered earthquake and collapse level earthquake as recommended by FEMA P695. The results showed that the history of link rotation is single sided and depends strongly on e/L and the level of ground motion. Nonsymmetrical loading protocols that depend on the aforementioned variables were developed and are presented herein.

Collapse Mechanism of Strong Column Weak Beam Buildings of Varying Heights

During past earthquakes column plastic hinges are more important than beam hinges which gives rise to global structural damage and high life threatening risk. All the structural components transfers their forces through column and then column shares it with foundation to soil, so u can imagine if column fails whole structure can collapse this is strong beam weak column concept. In this paper collapse mechanism of three buildings 5, 12 and 15 storey heights are investigated for strong column weak beam concept. The structure is designed for zone 5 and medium soil. The aim of this work is to determine the static non-linear performance of three buildings of varying heights, each storey height is 3m and each bay width is 5m, the width of the building in X and Y direction is 20m. The heights of the buildings are 15m, 36m and 45m. The parameters which are obtained from the analysis are base shear, displacement and hinge formations in the structure. The base shear and displacement of the structures increases with an increase in strong column weak beam concepts. The hinge formations in the low-rise building involved beam failures where as the hinge formation in mid-rise buildings involves mixed failure pattern involving beams and columns.

Optimum Location of Soft Storey in Multi-Storeyed Building

The present study is focus on 11-storey reinforced concrete buildings to optimize the location of soft storey under seismic zone-v. The plan of building 40m x 40m is considered. In X- direction and y-direction number of bays is 8 and each bay width is 5m. To observe the non linear behaviour of multi-storeyed building will be studied for various position of soft storey by increasing the storey height. Soft storey is provided at 1st storey, 5th storey and 10th storey. In this first three models is analyzed by increasing height of storey as 4.5m and other three models is analyzed by increasing height of storey as 5.1m and remaining storey height is kept as 3m are compare with regular building by using ETABS software. Comparison is made for the storey displacement, storey stiffness, base shear and formation of hinge patterns. The result remarks the conclusion that base shear carrying capacity of the structure increases as the soft storey is placed at higher levels and is least when the soft storey is at the ground. The seismic performance of structures is very sensitive to stiffness ratio. The lower the stiffness ratio of soft storey displacement of that structure is high.

Study of the seismic performance of Centrically Fused Braced Frame (CFBF)

Abstract This paper presents an analytical study to investigate the seismic performance of Centrically Fused Braced Frame (CFBF) which was recently proposed. In CFBF systems, a very thin mid-height gusset plate with the specified details as a Structural Fuse (SF) is designed to dissipate the input energy demanded by seismic loading and tolerate large inelastic deformation while other structural element and connections including braces, beam, columns and corner gusset plates remain in elastic behavior range. This study describes summary results of four three-fourth scale experiments then a set of validated analytical Finite Element Models (FEMs) are developed based on latter experiments using displacement and damage evolution formulation to include the crack modeling explicitly. The results of this study confirms that the CBFB system is capable of concentrating the plastic strain demand at mid-height gusset as a central Structural Fuse (SF) efficiently for the studied bay width to story height ranging from 1.0 to 1.6 and specified details of mid-height gusset plate and the proposed detail for mid-height gusset plate as a Structural Fuse (SF) is able to provide the minimum requirements as desired by AISC codes for qualified Special Concentric Braced Frame (EBF). Finally, the proposed closed-form equation can predict the peak strength of proposed system having maximum error bounds less than 15%.

Reconsidering a proportional system of timber-frame structures through ancient mathematics books: a case study on the Muryangsujŏn Hall at Pusŏksa Buddhist Monastery

ABSTRACTThe mathematics references in ancient China, the Zhoubi Suanjing and the Jiuzhang Suanshu, present information on formative ideas of ancient people and their perception of objects. The introduction to the Yingzao Fashi mentions mathematical sources, including the Zhoubi Suanjing. Both of these books focus on the philosophical concept of Tianyuan difang (Heaven is round and Earth is square), as well as inscribed and circumscribed circles. The square root of 2(√2), which can be derived from this part, proves to be an essential criterion for building, seen in Korea, China, and Japan. Using the exemplary Koryŏ building, the Muryangsujŏn Hall at Pusŏksa Buddhist Monastery, this thesis shows that the standard ground plan width of the outermost bay has a √2 ratio to the central bay width. Its cross-section, likewise, proves that √2 times or twice the distance or height (relying on the height of the eave columns) are applied to the distance or height between each column and purlin in the application of arithmetic and geometric concepts. In the future, this work will be a reference for the reconstruction design of ancient buildings prior to the Koryŏ period, analogous to the Muryangsujŏn Hall.