Bracing Configurations Research Articles

Analysis and Design of Electrical Transmission Towers with Various Sections and Bracing Configurations

Abstract: This study focuses on the analysis and design of a 400kV electrical transmission tower with a height of 50 meters. The tower was modeled in STAAD.PRO using three distinct steel sections Angle, Tube, and Channel combined with various bracing configurations, including X, K, and D-bracings. The main objective of this study is to determine the most efficient and economical configuration for the design of Transmission tower. The tower is analyzed for Dead load, Live load and wind load as per the codes. The study concludes that transmission towers with angled sections and X-bracing exhibit moderate displacement, minimal reaction forces, and reduced structural weight, making them a preferred design choice. Manual calculations were performed to design the connections and footing, ensuring structural integrity. The results confirm that the tower's connection design is safe and reliable

Study on the load capacity of prefabricated buckling-restrained braces with ductile steel castings based on singular function

Prefabricated buckling-restrained braces with ductile steel castings were used in the special concentrically braced frames to enable brace yield without buckling and prevent brittle failure of brace joints. This study presents a simplified three-segment calculation model subjected to axial force, based on the failure mode of the bracing system, utilizing singular function to derive formulas for the ultimate capacity of the braces. The accuracy of the computational formula was validated through numerical simulations and experimental findings. The outcomes indicate that the core unit of the brace undergoes third-order buckling deformation under axial force. The ultimate capacity of the braces is observed to increase with the cross-sectional area of the core unit but decrease with the length of the ductile steel castings. The theoretical values of the ultimate bearing capacity of the bracing system closely align with numerical simulations and experimental results, with error margins of 2.9 % to 9.3 % and 3.2 % to 4.6 %, respectively. These findings offer a theoretical foundation for the stability assessment of such brace configurations.

Bracing systems for three-ribbed arch bridges against out-of-plane buckling

This paper is concerned with the design of bracing systems for three-ribbed parabolic arch bridges against out-of-plane buckling. Typical bracing systems for the three-ribbed arch bridges include K-bracing system and X-bracing system as well as transverse bracing system. The buckling criterion of the braced funicular three-ribbed arch bridge is derived from an exact matrix stiffness method (MSM) with a 14 × 14 s-order element stiffness matrix of three-dimensional beam-column elements that allows for torsional and warping deformations. The lateral torsional buckling load and mode are given by the lowest eigenvalue and eigenvector associated with the assembled structural stability stiffness matrix. A comparison study between different bracing system configurations suggests that the three-ribbed arches with the integral K- or X-bracing system (a K/X-bracing across the three arch ribs) have lower lateral torsional buckling loads than their arch counterparts with the independent K- or X-bracing system (the adjacent arch ribs are connected by K/X-bracing respectively), because the latter ones could provide more restraint on the middle arch rib to avoid early lateral torsional instability. Further, a bracing utilization efficiency index (defined as the normalized buckling capacity over material usage for bracing system) is proposed to quantify the effect of bracing systems in improving the lateral torsional buckling capacity of arch bridges. Highly efficient bracing systems that maximize the lateral torsional buckling load of three-ribbed arch structures with the lowest bracing material usage are then recommended.

Numerical hybrid simulation assessment of E‐BRBF and E‐FBF systems for mitigating P‐delta effects and enhancing post‐earthquake performance

AbstractThis article investigates the seismic stability of E‐BRBF and E‐FBF systems previously proposed as stability‐enhanced alternatives to conventional BRBF and FBF systems. The E‐BRBF system is a buckling restrained braced frame with an inverted‐V brace configuration in which one of the two braces is a conventional brace designed to remain elastic during a strong earthquake. When the buckling restrained brace (BRB) yields, an unbalanced vertical force develops at the brace‐to‐beam connection, which imposes flexural demand on the beam and creates a positive post‐elastic storey shear stiffness. The E‐FBF system is identical except that the buckling restrained braces are replaced by conventional bracing members constructed with an end friction connection designed and detailed to slip at a predetermined load. At every storey, the beam and the elastic braces are designed such that this post‐elastic stiffness is sufficient to cancel the negative storey shear stiffness resulting from P‐delta effects and introduce a re‐centring mechanism to achieve an enhanced performance in steel buildings subjected to interface subduction earthquakes. Using distributed plasticity numerical models, past studies demonstrated the effectiveness of E‐BRBF and E‐FBF systems in mitigating P‐delta effects, emphasizing the importance of a stable and predictable response of the beam, which is a critical element in the scheme that provides the post‐elastic stiffness of the system. This beam is subjected to axial and flexural demands and must remain near elastic to ensure the global seismic stability of the structure. The response of the beam can be affected by localized yielding and local instability effects resulting from residual stresses, stress concentration near gusset plate connections and geometric imperfections. Employing a refined nonlinear finite element model of the beam element, this article assesses the performance of 10‐storey E‐BRBF and E‐FBF systems utilizing multi‐platform numerical hybrid simulations. The evaluation involves static‐monotonic and dynamic response history analyses, incorporating seismic excitations representing Vancouver, BC's seismic hazard (Crustal, In Slab, and Subduction Interface). In the hybrid simulation model, the most critical member for the proposed system (i.e., first‐storey beam) is sub‐structured in ABAQUS using solid elements, while the remaining frames are integrated using OpenSees using fiber‐based sections. Numerical hybrid simulation dynamic nonlinear response history analyses demonstrate the adequacy of the E‐BRBF and E‐FBF systems in mitigating P‐delta effects with residual drifts within repair limits, unlike conventional systems where instability or excessive drifting occurred. Monotonic Pushover hybrid simulations reveal a more ductile beam behavior compared to standalone models, in which frame members are entirely modeled in OpenSees. The analysis also indicates a ductile plastic hinging beam failure mechanism with no instability failure modes at extreme drifts.

Seismic Performance Evaluation of Steel Braces in Enhancing the Lateral Load Resistance of RCC Flat Slab Structures

This research paper conducts a comprehensive investigation into the seismic performance of reinforced concrete flat slab structures, employing different configurations of steel bracing systems. The seismic behavior of flat slab buildings with 5, 7, and 9 stories is scrutinized through Equivalent Lateral Force (ELF) analysis and Response Spectrum Analysis (RSA). The study delves into the efficacy of various bracing configurations, encompassing X-bracing, eccentric bracing, and knee bracing, in augmenting the lateral load resistance of these structures. Additionally, the research evaluates the influence of bracing systems on crucial structural response parameters such as displacement, drift ratio, base shear, and fundamental natural period. Keywords: steel bracing, seismic performance, flat slab structures, comparative study

Seismic Resilience of Steel-Braced Frames Incorporating Steel Slit Dampers: A Review and Comparative Numerical Analysis

Steel dampers, specifically steel slit dampers (SSDs), are crucial for enhancing the seismic resilience of buildings by absorbing energy and mitigating damage. SSDs are celebrated for their ability to produce stable hysteretic behavior, owing to the inelastic deformation of their strips, alongside benefits such as lightness, ease of manufacture, and straightforward post-earthquake replacement. This research extensively examines SSD applications, design principles, and innovations in their modeling, optimization, and production processes. The literature highlights SSDs' consistent performance in resisting both compression and tension, their adaptability in strength, ductility, and energy dissipation through modifications in strip configurations and the superiority of non-prismatic and hourglass-shaped designs over traditional options. Numerical analyses have been conducted to assess the effectiveness of non-prismatic slit dampers in comparison to their prismatic counterparts within braced frames. Three distinct braced frame configurations have been analyzed: one with a diagonal brace without a damper, another featuring a uniform prismatic slit damper, and a third incorporating a non-prismatic slit damper with an hourglass shape. The analysis primarily compared these systems' hysteresis behavior, ductility, and energy dissipation capacities. Results indicate a significant enhancement in performance when utilizing non-prismatic slit dampers. Notably, these dampers exhibited a remarkable 69% increase in cumulative energy dissipation compared to prismatic ones. Furthermore, the study reveals that a steel slit damper-braced frame, when equipped with optimally designed slit geometries, can tolerate inter-story drifts in excess of 2% while simultaneously achieving a greater than 12% increase in energy dissipation efficiency. Doi: 10.28991/CEJ-2024-010-04-019 Full Text: PDF

Review of Using Shear Walls and Bracings for Seismic Strengthening of High-Rise RC Structures

This review explores the seismic resistance of high-rise buildings through the implementation of shear wall and steel bracing systems. The use of reinforced concrete (RC) buildings with shear wall systems and steel structures with concentrated steel bracing systems has become increasingly common to mitigate seismic effects. However, the response of these systems to seismic loads varies due to differences in structural design and response factor values. Additionally, the presence of asymmetrical building designs poses a potential risk during earthquakes, necessitating a thorough examination of both new and old structures. By analyzing the dynamic properties and influencing factors of irregular RCC buildings with shear walls, this research aims to assess the impact of shear walls on factors such as base shear, torsion, story displacement, and drift. Furthermore, the study investigates the effectiveness of steel bracing systems in enhancing the performance of high-rise buildings under wind and seismic loading conditions. Different bracing configurations are evaluated to determine their ability to reduce lateral displacements and improve structural strength and stiffness. The findings will provide valuable insights into optimizing the location and design of bracing systems for enhanced structural resilience against seismic and wind forces while considering both economic and effectiveness factors.

Automatic Column Grouping of 3D Steel Frames via Multi-Objective Structural Optimization

Formulations of structural optimization problems are proposed in this paper to automatically find the best grouping of columns in 3D steel buildings. In these formulations, the conflicting objective functions, minimized simultaneously, are the weight of the structure and the number of different groups of columns. In other words, the smaller the number of different groups of columns, the greater the weight of the structure, and the greater the number of groups, the smaller the structure’s weight. The design variables are the bracing system configuration, column cross-section orientation, and assigned W-shaped profile indices for columns, beams, and braces. The design constraints are the allowable displacements, strength, and geometric considerations. After solving the multi-objective optimization problem, the result is a Pareto front, presenting non-dominated solutions. Three evolutionary algorithms based on differential evolution are adopted in this paper to solve three computational experiments. Even if preliminary groupings of columns are adopted, considering architectural aspects such as the symmetry of the structure, it is possible to discover other interesting structural configurations that will be available to the decision maker, who will be able to make their choices based on the impacts on manufacturing, cutting, transporting, checking and welding.

Spectral Dynamic Analysis of Buckling Restrained Brace (BRB) Configurations in a Peruvian Irregular Building

Spectral Dynamic Analysis of Buckling Restrained Brace (BRB) Configurations in a Peruvian Irregular Building

Analysis of Seismic Performance Characteristics for School Buildings on the Bracing Configuration of Steel Frame System Reinforcement

Analysis of Seismic Performance Characteristics for School Buildings on the Bracing Configuration of Steel Frame System Reinforcement

The Performance of Concentrically Braced Frames (CBF) in Chevron V Brace and Diagonal Configuration by Considering Various Frame Heights

Concentrically Braced Frame (CBF) is a structural system with high stiffness, so it is recommended to be implemented in earthquake-hazard areas. The stiffness in CBF is contributed by its diagonal component, which is called bracing. Bracing reduces lateral deformation on the frame system because of the earthquake and prevents heavy damage or failure of the structure. So far, several studies have been conducted. However, the effect of the frame height and the bracing configuration on the CBF performance has not yet been clarified. This study analytically investigated several models of CBF in Chevron V Brace and Diagonal configurations. Those models were prepared with different frame heights. The analyses were conducted by employing the cyclic load and considering yield displacement control in each model. The observation was emphasized on the load-displacement hysteresis curve, from which the performance of each model can be revealed. Three parameters of performance are evaluated: strength, stiffness, and dissipation energy. The analysis discovered that the Diagonal CBF performed better than the Chevron V Brace CBF by presenting a larger and more stable hysteresis curve, which is addressed to better energy dissipation. It is also discovered that reducing the frame height is suggested to enhance the CBF performance due to the earthquake

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.

Analytical Study of Buckling Restrained Braced Frames in Different Seismic Zone Using ETABS

Abstract Tall buildings have unique seismic challenges, particularly the P-delta effect. This can cause an increase in loads on certain parts of the structure, leading to potential instability or collapse. The solution is to use buckling restrained bracing (BRB) systems, which improve the lateral strength of the structure and control the P-delta effect. The present study aimed to determine the effectiveness of various brace configurations in reducing the seismic response of a 50-story reinforced concrete structure, with a focus on P-delta effects. To achieve this, linear dynamic analysis (response spectrum analysis) was conducted using E-TAB software. The selection of bracing configuration, however, depends upon the seismic zone. For this reason, five distinct configurations (X-pattern, inverted V, forward inclined, zig-zag, and bare frame) are considered for the analysis of buildings in different seismic zones. A building model was employed to study the behaviour of a structure with and without BRB to compare the parameters of storey drift, story displacement, diaphragm drift, story shear, story stiffness, and story acceleration using E-TAB software. Results showed that both Type-4 and Type-2 braces perform similarly in several aspects in seismic zones III and V. However, Type-2 braces perform slightly better in terms of storey stiffness-Y, with a lower difference of 39-40 % compared to Type-4 braces with a difference of 49 %.

A comparison of utilization design ratios of self-centering shape memory alloy with different brace configurations

Concentrically braced frames are common and effective systems for resisting earthquake forces in low and high-rise buildings. While various brace configurations can improve seismic performance, steel yielding causes residual drifts, which complicate or render the repair of damaged buildings irreparable. Minimizing seismic residual drifts is, therefore, imperative. The Superelastic Shape Memory Alloys (SE-SMAs) are superelastic materials capable of experiencing large plastic deformations and regaining their original shape upon unloading. Their use in steel structures reduces residual deformations associated with seismic events and will facilitate post-seismic retrofitting.The impacts of the utilization design ratio (UDR) on the seismic response of different brace configurations are investigated using two utilization design ratios (UDR1 and UDR2). The results show that using the UDR2 reduces the used SE-SMA material while maintaining the unique characteristics of SE-SMA material. Further, the FEMA P-58 equation accurately predicts residual displacements for I-VBF and M−XBF when braces are designed using UDR2 but overestimates residual displacements for VBF and XBF when the same UDR2 is used.

Experimental investigation on lateral behavior of novel hybrid cold-formed steel walls with composite sheathing

This paper proposes a new hybrid cold-formed steel (CFS) wall system with thick corner columns to improve the lateral performance of CFS structures. 16 CFS walls with various composite sheathing, diagonal bracing, and corner configurations, including ten hybrid and six conventional walls, are experimentally tested to investigate their lateral behavior and performance under monotonic and reversed-cyclic lateral loading. The experimental results demonstrate that the effect of the diagonal bracing varies depending on the presence of sheathing and the type of CFS wall. The shear capacity of both types of CFS walls without sheathing is highly improved by diagonal bracing. On the other hand, the diagonal bracing effect on the double-sided sheathed conventional wall is negligible. The brace-to-track connection causes diagonal bracing to exhibit different capacities and behavior under compression and tension. It should also be noted that the effect of loading mode on lateral performance varies depending on the configuration of the hybrid walls. The loading mode effect on the shear capacity of hybrid walls with sheathing is negligible, whereas its impact on the shear capacity of hybrid walls without sheathing is observed to be up to 14%. The wood-fiber cement board as sheathing material increases the shear capacity and stiffness of CFS walls while decreasing their ductility. Overall, compared with the conventional walls, proposed hybrid walls with a certain level of ductility demonstrate higher shear capacity and stiffness and comparatively less energy absorption capacity.

Application of Sustainable Concrete in the Seismic Evaluation of an Innovative Type of Buckling Restrained Brace

The Buckling Restrained Braced Frame (BRBF), consisting of a ductile steel core in concrete or a steel tube encased in concrete, is constructed to avoid brittle failure modes. The application of ductile materials with improved damping properties, such as tire-derived lightweight aggregate concrete, has not been investigated in BRBF systems, but it enhances the overall performance of the system and contributes to sustainability. Hence, this study aims to investigate the influence of such an application on the response modification, overstrength, and ductility factors, as well as the general earthquake performance, of 4-, 8-, and 14-story special reinforced concrete moment resisting frames equipped with BRBF. The current study compares 48 different BRBF models with TDA infill and conventional concrete infill by considering various bracing configurations, such as Chevron (Inverted V and V), Split X, and Single-Leg BRBF, and different span lengths of 6 m and 8 m. The evaluations include nonlinear response history analyses intended to provide insights into the performance of BRBF when exploiting the available experimental stress–strain characteristics of tire-derived lightweight aggregate concrete as an alternative material. Furthermore, the effectiveness of using tire-derived lightweight aggregate concrete as an alternative damping material in BRBF is examined by comparing BRBF with the new damping properties of concrete. Buildings equipped with BRB encased in TDA showed reduced base shear demand (by an average of 7%) when compared to concrete infill, and the prescribed value for the response modification factor for buildings of 50 m or less provides an acceptable estimation of the lower bond factors in approximately 95% of the cases. Furthermore, when a system requires more damping, the application of BRB encased in TDA is recommended.

Assessing seismic response equivalency for fixed pile-founded offshore platforms utilizing PSDA and IDA

Detrimental seismic effects on offshore platforms safety and serviceability highlight the necessity of these infrastructures fundamental seismic investigations that contribute to the design and maintenance of reliable structures. To this end, probabilistic seismic response evaluation of fixed pile-founded offshore platforms utilizing probabilistic seismic demand analysis (PSDA) has been employed. Housner Intensity-Drift Ratio as the derived optimal pair -in which engineering demand parameters (EDPs) are calculated, given the ground motion intensity measures (IMs)- is chosen. A selection of optimal IM–EDP pairs is made based on the criteria of practicality, effectiveness, efficiency and sufficiency. In this study, equivalency of the results is evaluated comparing the same IM-EDP pairs against the method of incremental dynamic analysis (IDA). Furthermore, another objective of this assessment is to investigate the appropriate number of required ground motion records according to which structural seismic responses are not over/underestimated. The uncertainties associated with fixed pile-founded offshore platform brace configurations, besides the effect of soil-pile-structure interaction (SPSI) are thoroughly considered, generating more accurate and vigorous results. The findings of this study demonstrate that seismic responses resulted from IDA approach utilizing 12 ground motion records scaled 7 times matches well with those derived from PSDA.

Dynamic Response of Concentrically Braced Steel Frames to Pulse Period in Near-Fault Ground Motions

Steel braced frame systems (SBFs) having high stiffness and high strength are commonly utilized due to their resistance to lateral seismic forces in regions with high seismicity. In this study, concentrically braced frames (CBFs) having different bracing configurations are used to obtain the significance of the pulse period associated with near-fault (NF) ground motion by time-history dynamic analysis. Besides, far-fault (FF) ground motions are also used to compare with NF ground motion results according to chancing bracing configurations. To achieve dynamic responses of steel frames with different concentric bracings under NF ground motions, which especially have small, medium, and long pulse periods, 3-story and 4-span CBFs having different bracing configurations were selected as an example. 4 FF and 12 NF ground motions having different pulse durations were chosen to evaluate the dynamic response of concentrically braced frames. The results showed that peak ground acceleration (PGA) could be identified as a key parameter that controls the response of braced frames under FF ground motions. In addition, the ratio of the pulse duration to the first mode period is the dominant parameter when this ratio is only greater than 1.0 under the NF ground motions.

Sizing Optimization Using Genetic Algorithm to Achieve Minimal Offshore Structure

Accelerating marginal field development must consider the economic factor. While the structural strength must remain capable and robust when subjected to environmental loads. To meet the desired objective in design phase, optimization is used. With the rapid growth of computing technology, the optimization method is developed as more advanced and reduced iteration time. However, the structural evaluation of jacket structure is a complex problem. The usual process of structure evaluation is through finite element analysis, and it is still time-consuming. Thus, surrogate models can evaluate the structure, lowering computational time. This study optimizes the jacket structure to get an affordable and robust minimal jacket structure. Sizing optimization will be performed on the jacket's leg and bracing thickness. For single-objective optimization, weight structure is considered the objective function, and multi-objective optimization adds production cost as the second objective function. The surrogate model uses the radial basis function to predict the relation between design variables and ultimate limit strength. The functions generated from the surrogate model will act as behaviour constraints in the optimization process. For consideration, X-type and V-type bracing configurations are compared. Different results were obtained from the single objective and multi-objective optimization process.

Seismic Analysis of Steel Building with Bracing

Abstract: As we know that construction of steel buildings is popular nowadays. To protect buildings from earthquake by providing bracings are very common. Bracing help to resist the lateral load during earthquake. Bracings are providing in structure at various configuration. This paper illustrates the effect of new bracing configuration with existing x bracing configuration. The seismic analysis of the structure has been carried out using ETABS Software.