Bracing Pattern Research Articles

Effect of solid blocking on lateral bracing requirements for cold-formed steel wall studs

The effectiveness of horizontal bracing in increasing the strength of cold-formed steel (CFS) load-bearing walls has been widely acknowledged. However, while significant research has been conducted regarding the bracing requirements for CFS bearing walls, the effect of solid blocking, which prevents columns (studs) within the wall from rotating, has not been fully explored. In this study, we propose an analytical method to quantitatively assess the effect of solid blocking on bracing requirements for CFS load-bearing walls. This method is comprehensive as it can be applied to systems with different bracing patterns, load patterns, or non-identical columns (studs), and it accounts for the columns’ initial curvature and semi-rigid end connections. It has been verified that considering the solid blocking always decrease the bracing requirements because the existence of solid blocking increases the system’s stiffness and subsequently decreases the additional displacement as well as the brace force, as expected. An example consisting of 23 CFS studs is presented to illustrate how the effect of solid blocking on bracing requirements is influenced by the location and interval of solid blocking, the stiffness of column end connections, and the characteristics of tie bracing. The results indicate that the effect of solid blocking on bracing requirements increases when the location of solid blocking is closer to the anchor and the solid blocking interval is smaller. Moreover, a modification to the equation in AISI S100 is proposed to account for the effect of solid blocking on the strength requirement of tie bracing. Overall, this research contributes to a better understanding of the role of solid blocking in CFS load-bearing walls and provides insights for optimizing bracing design in practice.

Analysis and optimization of brace system in scaffold

Scaffold consists of horizontal components, vertical components and lateral braces, while the lateral stiffness of structure is mainly provided by brace system. Brace system can be classified into three groups: concentric brace, eccentric brace and knee brace. Concentric brace enables to offer greater stiffness, for providing direct load transfer. Eccentric brace and knee brace belong to ductile system, maintaining stability by energy consumption braces. Eccentric brace dissipates energy by deforming and buckling, while knee brace disposes energy by form a plastic hinges. Concentric brace is a common way for enhancing lateral stiffness in scaffold. Current studies aimed to investigate detail parameter effects in one brace pattern, while few comparative studies were carried on multiple brace pattern. In this paper, a simplified simulation method was proposed. Throughout simulation analysis, some regulations of brace arrangement were summarized, which provides a guidance during the scaffolding design and optimization process.

Segmental instability failures in transmission line towers

This paper presents the results of the detailed studies conducted on premature failures of transmission line towers during full-scale testing. Configuration and proportioning of base width, hamper width, the height of each segment and selection of bracing patterns play a vital role in providing geometric stability to the tower. In the present study, three towers of different voltage clauses failed during testing, investigated and found that geometric instability caused the premature failure. In the case of a 500 kV tower with a rectangular configuration, the staggered bracing pattern continuously for multiple segments for about 20 m height without a diaphragm bracing in between caused geometric instability in the tower. Nonlinear FEA results of the tower modelled with diaphragm bracing showed that tower failure can be prevented by introducing diaphragm bracing at different heights. The 400 kV double circuit dead-end type tower with a 15 m height bottom segment and 161 kV suspension towers analysed based on the conventional static analysis ignoring geometric instability failed prematurely and FE analysis clearly shows the failure due to geometric instability. It is recommended to divide the single segment into two segments such that the included angle between the leg and primary bracing member can be increased, and thereby additional moments in the leg members are reduced by making the bracing member contribute to sharing the shear. The code recommended minimum included angle of 15° between the leg and primary bracing member is only a guiding parameter for the designers. Based on this study, it is recommended that the designers shall check the tower geometry for segmental / panel instability by modelling and nonlinear FE analysis of the tower with beam elements in place of conventional space truss elements.

Seismic Analysis and Design of Elevated Circular Water Tank for Variation of H/D Ratio and Bracing Patterns

Abstract: Seismic analysis and design of elevated circular water tanks play a crucial role in ensuring the structural integrity and safety of these essential infrastructure components. This study focuses on investigating the effects of varying the height-todiameter (H/D) ratio and different bracing patterns on the seismic performance of such tanks. The analysis procedure includes a comprehensive numerical investigation using finite element analysis (FEA) software. The elevated circular water tank models are subjected to various seismic loading conditions to evaluate their dynamic response. Different H/D ratios are considered to assess their influence on the tank's behavior under seismic excitation. Additionally, the study explores the impact of different bracing patterns on the tank's seismic resistance. Various bracing configurations, such as radial, circumferential, and combined patterns, are investigated to identify the most effective design approach for mitigating seismic forces.

Comparative Study of Intze Type of Water Tank for Different Bracing Pattern under Wind and Seismic Load

Abstract Overhead water tank is a water storage facility supported by a tower and constructed at an elevation to provide useful storage and pressure for a water distribution system. Safety as well as working of such structures is considered as very crucial during earthquakes, since they put up for necessities like drinking water, firefighting during fire accidents, etc. Such structures should stay in operating condition even after several earthquakes. This RC overhead water tanks involves huge water mass supported on the top of tank supporting system known as staging. This investigation is basically to discover the seismic behavior of RC overhead water tanks. In this study, a FEM based model is used for finding out the nonlinear seismic performance of RC overhead water tanks with several staging variations. The staging that is different bracing patterns considered in this study in lateral and vertical direction, which relatively increases the strength and stiffness of tank in supporting system. Staad models are prepared and analyze for different seismic zones as well as for cyclonic regions and observed the parameters such as base shear, base moment and lateral displacement. The commercial software STAAD.Pro is used for structural analysis. Since the seismic response of water tank structure depends on its dynamic properties and frequency of ground motion. This seismic analysis of overhead water tank structure cannot be carried out on the basis of maximum value of ground acceleration because of nonavailability of ground acceleration data at every location. Hence for seismic analysis of overhead water tank, earthquake response spectrum analysis is widely used. While using this method, smooth design spectra is used to determine the value of displacement and forces in members at every mode of vibration. Octagonal, Radial, Cross, Alternate tie , Diagonal and X- type bracings are used to analyze the structure under all the seismic zones viz. II, III, IV & V. Also observed the behavior of tank for cyclonic region where wind load is increased by 30%. Analysed the overhead water tanks of same capacity for different bottom dome deviation angles and concluded.

Performance of Different Bracing Patterns for Moderately Tall Steel Buildings Subjected to Lateral Load

In the present work, a model of moderately tall steel building G+20 storied, has been developed and then analysed for lateral load using design software STAAD Pro. Performance of different types of bracing systems are checked under gravity load and wind load. Various results such as bending moment, shear force, lateral deflections, storey drift, axial load on columns are extracted from this analysis and studied meticulously. In few cases of brace pattern effect of providing eccentricity are also studied to suggest optimum positioning of these bracing systems.

Experimental and numerical investigation on reserve strength of jackets with single diagonal and X brace configurations

ABSTRACT Jacket framing arrangement X, K, V and single bracing systems used in jackets influence the ultimate strength and redundancy in the system. Experimental investigation was conducted on a 2D frame (1:20) with two different bracing patterns (2D-1 and 2D-2) the results are compared with that obtained from nonlinear pushover analysis. Parametric assessment of Reserve Strength Ratio has been carried out on three bracing patterns, namely 3D-A, 3D-B and 3D-C using non-linear pushover analysis including pile-soil interaction. It is observed that RSR increases by 15% for X brace configuration (2D-2) compared to single brace configuration (2D-1). The RSR for 3D-B is found to be higher by be 35 % and 12% compared to bracing patterns 3D-A and 3D-C respectively. The brace pattern 3D-C exhibits similar strength to 3D-B, illustrating the insignificance of the brace at the top bay and this leads to reduction in wave loads on the system.

Investigation of the Occurrence of Progressive Collapse in High-Rise Steel Buildings with Different Braced Configurations

Abstract The progressive collapse phenomenon refers to a chain of damages in a structure where all or a large part of the structure is destroyed by an initial local collapse in it, which can lead to very disastrous results. Therefore, the prevention of progressive collapse has become a necessary action in the design and analysis of buildings and it is vital to investigate this topic more accurately. This study aims to present a proposed pattern in the configuration of braces at the height of a high-rise steel building for reducing the probability of progressive collapse. In this regard, the vertical displacement of 18-story structure with four scenarios of column removal and five concentric bracing patterns including V, Inverted V, X, discontinuous X-bracing at height, and a combination of Xbracing in the side spans and discontinuous X-bracing at height in the middle spans are investigated and compared. In this study, the Alternative Path Method (APM) is used based on the GSA guideline for the analysis of progressive collapse. The results of this research showed that the use of X-bracing in the side spans and discontinuous X-bracing in the middle spans in nonlinear static and dynamic analyses performed better in reducing the probability of progressive collapse than other bracing configurations. Finally, it is recommended to use discontinuous X-bracing at the height that would place the bracings in one direction and providing alternative paths for force transferring in the structure.

Model-based evidence of the dominance of the guitar brace design over material and climatic variability for dynamic behaviors

It is generally alleged that the design choices of acoustic guitar bracing patterns lead to a specific sound of the instrument. However, in the presence of strong uncertainties due to variability of material properties and climatic conditions, the robustness of the soundboard dynamics has yet to be investigated. In this study, three types of bracing patterns are studied using physics-based models and stochastic analyses are performed to account for material and climatic uncertainties. It is shown that the choice of a brace design leads, at least in the low frequency domain, to a dynamic behaviour that is not stackable with another design, even in the presence of strong aleatory uncertainties. This assessment supports the conjecture that guitar brace design choices have a greater impact than material variability where guitar soundboard dynamics are concerned. More generally, these results illustrate the usefulness of detailed physics-based models in the understanding, design and making of guitars.

Performance Evaluation of Elevated Storage Reservoir with Hybrid Staging

Elevated water tanks are essential Civil Engineering framework which are known as compulsory community services urban areas. A number of elevated water tanks suffered collapse and damage to their staging in deep earthquakes, consequently their safety performance is a crucial concern throughout effective earthquake. Because of storage of clean water, it is utilized for important needs such as drinking purpose and for other domestic purpose. Within the existing work, four support patterns viz. easy brace, cross brace, rectangular brace as well as radial brace connected with various staging heights (fifteen m, twenty m, and twenty-five m) are analysed for seismic zone II, III and IV for empty tank and loaded tank. Probably the most affordable as well as secure, Intze style tank of thousand kilolitre capacity considered. When it comes to the evaluation of Intze container, 72 designs are constructed with STAAD.ProV8i Software, by which 36 models are analysed for empty tank and additional 36 models are analysed for loaded tank. Each and every seismic zone has 12 models as well as every brace has three distinct staging rises. For the safety, stability and serviceability, different parameters are obtained for different brace pattern

Effects of Bracing System on Multistoryed Steel Building

In recent years, in regions of the highly seismic prone area, steel construction has changed from moment resistant frames to concentrically braced frames. To withstand earthquake forces, bracing part of the structural pattern by providing extra stiffness plays a crucial role in structural action. Concentric bracing in building frames is one of the most common horizontal load resistance patterns. For this reason, seven distinct models were created by changing the bracing pattern in the steel frame and analyzed for wind and seismic forces A 20-story steel frame structure is explored in this presented work. From this research, it can be inferred that the bracing factor will have a very significant impact on structural behavior under seismic loading. The most desirable bracing framework is the Backward bracing pattern. Horizontal displacement at the top floor is decreased by approximately 50 percent for Backward braced in frame structure compared to without bracing pattern.

Hybrid braced frame with buckling-restrained and strong braces to mitigate soft story

The steel concentric braced frames (CBFs) are the common structural system for buildings. Unlike high strength and stiffness, brace buckling in CBFs results in high nonlinear behavior, which causes damage concentration in one or a few stories during a severe earthquake. This paper proposes a hybrid CBF bracing system to reduce soft-story mechanisms and improve the structural behavior of the CBF system. The proposed system is composed of a buckling restrained brace (BRB) or an energy dissipation device and a strong brace (SB) in one span. The strong braces are designed to have an elastic performance during an earthquake. The direction of BRB and SB are changed, inversely, story by story in a zigzag form. This configuration leads to paradoxical results: stiffness and ductility. This improves both the soft story mechanisms and the buckling capacity of CBFs. In this study, a set of 6-story structural models with different bracing patterns including inverted-V, multi-X, zipper, hexa (hexagonal bracing configuration), and strongback braced frames were evaluated through nonlinear static (pushover) and dynamic analyses (IDA). The collapse performance of structural models was assessed by comparing the seismic behavior of conventional CBFs with similar bracing configuration based on FEMA P695 criteria. From the evaluation of collapse fragility curves, the hybrid bracing system had more safety margin against collapse during severe earthquakes than conventional CBFs.

Behavior of three-chord concrete-filled steel tube built-up columns subjected to eccentric compression

An experimental investigation of a series of three-chord concrete-filled steel tube (CFST) built-up columns was conducted under eccentric compression. The influences of slenderness ratio, eccentricity ratio, eccentricity direction, and brace pattern (battened or laced) on the load bearing process, failure modes, and ultimate load-carrying capacities of the specimens were analyzed. The test results indicate that a CFST built-up column exhibits better performance than a corresponding plain steel built-up column. The ultimate strengths and stiffnesses of the three-chord CFST built-up specimens decreased with increasing slenderness ratio or eccentricity ratio. Battened specimens exhibited lower load-carrying capacities than laced specimens, and different load-bearing capacities were obtained for specimens under different directions of compression eccentricity. Using the proposed equivalent slenderness ratio, three existing design codes were evaluated to predict the stability coefficient, and a new correlation equation considering two failure modes is suggested for calculating the ultimate strength of three-chord CFST built-up columns subject to combined compression and flexure.

Effect of Steel Bracings on RC Building by Aligning Them at Different Positions

Earthquake is an unexpected and expensive disaster for both livelihood and economy. In the modern day construction there has been a lot of importance to make the structure resistive against the laterally acting loads. Bracings are an option for lateral load resisting system in tall buildings. The concept of bracings is to add more stiffness and strength to the adequate strength of the structure. Members in a braced frame are generally made of structural steel which can work effectively both in strain and pressure. In the present work 13 story irregular building is considered with and without bracings to evaluate the optimum bracing pattern for the structure. By changing the position of the bracings alternately in both horizontal and vertical direction the analysis is carried out. These are the different models analyzed by pushover analysis (a) Building with no bracing, (b) Building with alternate vertical bracing starting from bay-1, (c) Building with alternate vertical bracing starting from bay-2, (d) Building with alternate vertical bracing starting from story-1, (e) Building with alternate vertical bracing starting from story-1. The non linear static results were compared. The various parameters like story drift, shear, time period, stiffness, moment, torsion, performance points are obtained by the analysis for all the models.

Comparative Analysis of Elevated Water Storage Structure using different Bracing Pattern in Staging

Comparative Analysis of Elevated Water Storage Structure using different Bracing Pattern in Staging

Factors contributing to the transverse shear stiffness of bolted cold-formed steel storage rack upright frames with channel bracing members

Accurately determining the transverse shear stiffness of steel storage rack upright frames is essential in calculating the elastic buckling load, performing earthquake design and serviceability checks. International racking design specifications recommend different approaches to evaluate this stiffness. The Rack Manufacturers Institute (RMI) specification conservatively uses an analytical solution based on Timoshenko and Gere's theory while the European (EN15512) and Australian (AS4084) specifications recommend experimental testing to be conducted. Previous studies have shown that Finite Element Analyses (FEA), solely using beam elements, fail to reproduce experimental test results and may overestimate the transverse shear stiffness by a factor up to 25. This discrepancy is likely attributed to the local deformations occurring at the bolted joints. In this paper, a model to capture the transverse shear stiffness of upright frames is developed using shell elements and advanced FEA. Its accuracy is verified against published experimental test results performed on three commercially used upright frame configurations with lip-to-lip bracing pattern. The model accurately reproduces the experimental stiffness, with differences ranging from 2% to 17%. Based on the FE model, the factors contributing to the transverse shear deformation of the frames are quantified and discussed for both lip-to-lip and back-to-back bracing patterns. For lip-to-lip upright frames, results show that the local deformations at the end of bracing members contributes the most to the shear deformation of the frames. For back-to-back upright frames, bolt bending and axial deformation of braces contribute the most to the shear deformation of the frames. Results from this paper would assist the racking industry in improving their products by focusing on the factors influencing the most the behaviour of the frames.

Alongwind load effects on free-standing lattice towers

Free-standing lattice towers are structures used for various purposes such as radio and television broadcasting, electric power and microwave transmission, meteorological measurements, wind energy production and so on. Due to their properties, they are mainly sensitive to wind loads. A longstanding discussion on the wind loading effects on this structural type has been carried out in the literature. This paper investigates the alongwind load effects on free-standing lattice towers by introducing specific influence functions of displacements, shear forces, bending moments and axial forces in leg elements. Such influence functions are first derived, calibrated and validated for the most typical structural types, then they are used within the framework of the gust effect factor technique. Comparative studies with reference to both the traditional use of cantilever beam approaches and finite element methods point out the role of the bracing pattern and, more precisely, of the level of the crossing of diagonals in tower panels. All the applications developed here refer to real structures with different properties. Results are interpreted and compared with those provided by previous studies on this structural type. Engineering and design issues are discussed focusing on the most critical aspects concerning dynamic wind loads.

Topology optimization of bracing systems using a truss-like material model

To minimize the compliance of frame, a method to optimize the topology of bracing system in a frame is presented. The frame is first filled uniformly with a truss-like continuum, in which there are an infinite number of members. The frame and truss-like continuum are analysed by the finite element method altogether. By optimizing the distribution of members in the truss-like continuum over the whole design domain, the optimal bracing pattern is determined. As a result, the frame\'s lateral stiffness is enforced. Structural compliance and displacement are decreased greatly with a smaller increase in material volume. Since optimal bracing systems are described by the distribution field of members, rather than by elements, fewer elements are needed to establish the detailed structure. Furthermore, no numerical instability exists. Therefore it has high calculation effectiveness.

STUDY ON EFFECT OF STOREY HEIGHT ON THE SEISMIC PERFORMANCE OF TALL BRACED BUILDINGS

Present trend of high-rise buildings in the urban scenario, there is necessity for finding effective and efficient forms of bracing systems to be used in high rise buildings to resist lateral loads.Various bracing patterns perform differently under different storey heights.The present study aims at finding the effect of storey height on the structural responses of tall braced buildings.Response spectrum analysis is performed to investigate the structural responses like lateral displacements, storey shears, storey drifts and Overturning moments.The bracing patterns studied in the present paper are diagonal, X, V and inverted V-bracings. 10-storeyed building with 3.0 m, 3.6 m and 4.2 m storeyheights is considered in zone V for the present study. In the present paper, ETABS software is used for investigating the structural responses of Tall Buildings.

Bracing Configurations Effect on BucklingRestrained Braced Frames

Buckling restrained bracing systems are effectively being used to reduce seismic response during recent years. But often configurations of these systems are ignored while evaluating their behaviour. Aim of this study is to consider the effect of different bracing configurations on the behaviour of Buckling Restrained Braced Frames(BRBFs). Five-storey three-bay braced frames with three different patterns are modelled using Finite Element Analysis software ANSYS. The main variables of this study are the bracing pattern and location of bracing. The effects of bracing configurations on seismic behaviour of buckling restrained braces are also considered. The best combinations of bracing pattern and location along with specific bay width and storey height in terms of seismic response are suggested finally.