Bracing System Research Articles

Experimental Investigation of Seismic Vulnerability of Braces under Hazard Consistent loading sequences

AbstractIn the last ten years, Chile and Japan have experienced several subduction earthquakes that lasted for extended periods of time. These occurrences have emphasized the need for a thorough examination of how the duration of ground motion impacts the performance of the components of the lateral load resisting system. In the present study, three large‐scale experiments were conducted on the wide‐flange brace member to evaluate the seismic vulnerability of the braces under the hazard consistent loading protocol. The loading sequences consider in the study are standard symmetric cyclic loading sequences, collapse‐consistent loading sequences representing subduction zone tension dominated and collapse‐consistent loading sequences representing subduction zone compression dominated. The subassemblage test‐set‐up was taken in the study to consider the effect of the end‐protect zone on the seismic assessments of the brace members. The evolution of strain at the mid‐section of the brace member is observed to be higher in case of the standard loading sequences as compared to the subduction zone loading sequences. The post yielding stiffness and the collapse resistance of the brace member under the subduction zone earthquake are present. The damage state of the open section brace member and evolution of the local bucking at the mid of the brace member were discussed. It is observed that open section delays the accumulation of strain at brace member and delay the fracture initiation. The ductility of the different brace members is compared to highlight the influence of the cross‐section properties of the brace on the ductility of the braced system.

Reliability of steel structures with Chevron bracing systems considering the performance-based seismic design philosophy

In this paper, the seismic performance and reliability of steel buildings with Chevron-Braced frames are studied integrating a novel probabilistic approach and the performance-based seismic design concept. The seismic response of models is extracted using response history analyses with the help the commercial software SAP2000. In this sense, three variables associated with the seismic response of the structure are studied: overall lateral displacement, rotation of connections, and inter-story drift. Those responses are evaluated by exciting the structure with eleven characteristic ground motions of the zone with respect to three performance levels: immediate occupancy, life safety, and collapse prevention. Once the seismic response is extracted for every performance level, the reliability of the models is calculated with respect to inter-story drift as described next. First, considering the seismic response in terms of inter-story drift for every ground motion, the associated histogram is constructed. Then, using 13 Probability Density Functions (PDFs), a Chi-square test is performed to identify the best-fitted PDF associated to the histogram of inter-story drift. Afterwards, with the best-fitted PDF of inter-story drift, the probability of failure and reliability index are extracted considering serviceability limits for every performance level. This represents a unique approach to extract the risk of structures subjected to ground motions associated to different performance levels. In addition to the structural reliability, a study about the cost of the structures with and without Chevron braces is developed, and then, it is documented the best option. Finally, based on the results reported in this paper, it is demonstrated that steel buildings with Chevron-braced frames present a better seismic performance than steel moment resisting frames without any bracing system. In summary, overall lateral drifts are reduced between 40 and 60% when Chevron braces are implemented in comparison to steel moment resisting frames without braces. On the other hand, if Chevron bracing systems are not used, i.e., in steel moment resisting frames, the inter-story drifts are about 300% higher than those of steel structures with Chevron braces. Hence, structural damages can be considerably reduced if Chevron-braced frames are implemented in steel structures that may be excited by characteristic ground motions of the zone where they are located.

Analysis and design of a vertical sectored tank

AbstractThis article describes the conceptual design and the structural analysis of a vertical cylindrical partitioned tank for an international chemical company. Vertical cylindrical tanks are commonly used in the chemical industry worldwide as vessels to contain liquids. Most of these plants have reduced area for the installation of the container tanks. Many of them need to renew their manufacturing process according to the new technologies and requirements. In addition, in some cases, the preparation of mixtures is carried out on small surfaces. All this factors led to the idea of designing a vertical sectorised tank, considering that alternative hydrostatic pressure cases can lead to eccentric loads on the upper surfaces. Therefore, bending stresses and compression and tension stresses will occur. A Finite Element Method calculation was performed to determine the wall thickness fulfilling the structural requirements for two distinguishing design alternatives. This article describes the particular models designed and the detailed FEM simulation and mechanical calculation carried out to determine the optimized solution of partitioned tanks with a diamond‐shaped inner bracing system that manages to meet all the structural, manufacturing, constructive and environmental needs with a target thickness of 12 mm.

Seismic Performance of Reinforced Concrete Buildings with Different Lateral Load

Shear wall, steel bracing and combined system are the most commonly used lateral-load resisting technique for high-rise buildings. Shear walls have very high in-plane strength and stiffness, which can be used simultaneously for resisting large horizontal and gravity loads. The aim of this study is to examine how well reinforced concrete buildings withstand seismic activity using various systems for resisting lateral loads. In this study, a reinforced concrete building with 12 floors (G+12) and 5 X 5 bays is selected, and various lateral load resisting frame systems are applied in different positions. These are shear wall, bracings, shear wall-bracings combinations (Combined) at five different locations/patterns i.e., at outer corners (Type- I), center of outer sides (Type- II), middle corners (Type- III), center of middle sides (Type- IV), and inner core and middle sides (Type- V) respectively. A total of sixteen models are created for this study, with one being a bare frame and the other fifteen consisting of three types of lateral load resisting systems arranged in five different configurations each. With the assistance of ETABS all models are analyzed by Equivalent Static Analysis and Response Spectrum Analysis. The performance of building is evaluated on the basis of following parameters- maximum storey displacement, maximum storey drift and storey shear. At last the results are compared for different models. Among the three systems, the shear wall system exhibits the least displacement and the highest stiffness. Response of combined system is better than that of bracing system. Overall, the Type II shear wall model is more earthquake-resistant and structurally efficient than the other fifteen models. Key Words: Equivalent Static Analysis, Response Spectrum Analysis, Maximum storey displacement, Maximum storey drift, Storey shear

Perbandingan Nilai Simpangan Horizontal yang Menggunakan Bresing Tipe Diagonal dengan Inverted V dalam Menahan Gaya Lateral pada Studi Kasus Hotel Loji Kridanggo Boyolali

Application of a bracing skeletal system is an additional steel structure that can strengthen a column by transferring weights and force to the received column. The broad use of flensa steel bracing type v diagonally and inverted gradually on each floor. It is possible to determine the junction of the junction if the building is brewed and not braced. The junction to cross section of the building does not use bracing, which USES bracing type v diagonal and inverted is 0.385:0.321:0.294. Bracing inverted type v is more rigid and sturdy than bracing diagonal types shown by the deviation of horizontal bracing the inverted type v smallest and volume 12.5 percent greater than bracing the type diagonal.

Experimental collapse investigation and nonlinear modeling of a single-span stone masonry arch bridge

Determining appropriate intervention methods for rehabilitation and restoration of historic masonry bridges requires understanding the true behavior of the structural system. The presented study addresses this need by focusing on nonlinear structural behavior of stone masonry arch bridges and investigates the effect of different constitutive material laws, modeling approaches, and multiple spans on simulating the true behavior of the structural system. An extensive experimental program was conducted on a ¼-scaled model of a selected span of the multi-span arch bridge consisting of the arch ring, spandrel walls, and the fill. The model was tested with and without the presence of an in-plane steel bracing system supporting the spandrel walls to study the effect of adjacent spans on the selected span. Line loading applied at the quarter-span was increased with constant increments until. Destructive experimental investigation was followed by numerical studies of the tested specimen by means of both macro and simplified micro modeling approaches with DIANA FEA software utilizing different constitutive material models including Multi-Directional Fixed Crack Model with/without Drucker-Prager plasticity material law and Total Strain Based Fixed Crack Model. Comparison of the experimentally measured values with those of the numerical model validates that both modeling approaches can accurately predict the collapse load and collapse mechanism. Although simplified micro model offers advantages such as capturing the observed local damage states and cracking at masonry joints between the units; the added requirements of time, computational effort, and detailed material knowledge to model such structures accurately, makes macro modeling technique more preferable for masonry bridges having a complex geometry.

Comparative Analysis of Steel Structure with Rigid and Semi Rigid Joint using Analysis Tool ETABS

Generally, in steel structure the connection between beam and column are designed as moment connection and pinned connection, but in actual condition the structure behaves between these two conditions, resulted into semi-rigid condition which is intermediate stage between rigid and pinned joints. Effect of semi-rigid connection on multi-story multi-bay frame is accomplished in this Study. The present study introduces the effect of static and dynamic loading on high rise steel structure of G+12 story with 4m, 6m and 8m three bay span length. Structure is analyzed under two different condition of partial release of semi-rigid connections which is derived by fixity factor of values 0.5 and 0.75 in this study. The analysis is done commercially available software ETABS. From the non-linear analysis, the story displacement and story drift are obtained. The overall performance of the structure from the analysis, semirigid joints display more story displacement and story drift compared to rigid joints. To overcome the results, bracing system is introduced at different location of periphery of structure. These brace frame structure consist of X- bracing and diagonal bracing. Again, comparative analysis is to be performed in ETABS on these three-bay span lengths. It is found that braced semi-rigid frame structure perform quite well as compared to unbraced frame structure.

Analysis of the Feasibility of a Diagrid Bracing System in Tall Buildings

Abstract: The primary goal of this study is to provide a superior lateral load-resisting system. In this study, the diagrid structural system is considered, with the shear wall core present at the center part of the building and the diagrid bracings provided at the outer periphery of the structure, which is formed of steel material. The diagrid, which is made up of inclined diagonal steel sections, allows the diagonal member to function axially to resist lateral loads. Due to its structural effectiveness and versatility in architectural planning, the diagrid structural system has recently been used in tall buildings. A 14-story Diagrid composite building is selected, and its analysis and design results are presented. The Diagrid bracing system is connected to the end bays, the diagrid bracing system is connected to the mid-end bays, and the diagrid bracing system is connected to the end bays these are the three different types of models that have been studied. The diagrid bracing system has been modeled by using structural steel material, and the remaining structure has been modeled by using concrete material. A standard 60 m x 60 m floor plan has been considered. FEM-based software called ETABS has been used to model and analyze structures. A PT slab and a PT band beam have been used in the model frame for the span of 10 m. By considering all possible load combinations, all structural members made of steel and concrete are analyzed by IS: 800:2007 and IS: 456:2000, respectively

Seismic performance and damage evolution of RC frames retrofitted by the novel GESB system: A numerical study

A novel gapped eccentric steel brace (GESB) system was developed to enhance the seismic performance of existing reinforced concrete (RC) frame structures. To thoroughly investigate the mechanism and damage mode of the novel retrofitting system, numerical analysis was conducted on retrofitted frames with various brace eccentricity configurations, using a comprehensive multi-scale finite element model. Six suitable damage indices were defined to carry out the structural damage evolution study during the whole loading process. On this basis, a simplified damage model was developed. The results demonstrated that GESB effectively modified the mechanical mechanism and failure modes of the frames. The brace eccentricity configuration exerted a significant influence on the structural strength, stiffness, and ductility. With regards to both of strength and ductility requirements, an eccentricity range of 0.3 to 0.4 was recommended. The proposed simplified damage model was used to indicate the allowable drift ratios associated to performance levels, which were found to be very variable with various eccentricity configurations. The outcomes are essential and timely for design decision of RC frames retrofitted by GESB.

Analysis of the behavior of reinforced concrete buildings with and without non-buckling braces under the effect of earthquake loads

The moment frame is one of the most widely used seismic resistant systems in the world, due to its high formability and flexibility, this system causes a lot of displacement in the structure and force exceeding the capacity of the structural components. The bracing system is a suitable method to control the lateral displacement of the structure and the seismic improvement of the bending frame. The new type of bracing system that is used in the design of new systems and the improvement of old structures is non-buckling bracing, and in this research, their effect on the performance of 4, 7, and 10-story concrete moment frames under the Northridge, San Salvador, and Tabas earthquake has been investigated. The research method in this research is analytical-applied, which the results of this study showed; In the 4-story structure, the amount of wasted energy under the 3 considered earthquakes is equal to 0%, 0%, and 1% without buckling braces and 39%, 48% and 50% in the case with non-buckling braces and in the 7- story structure, the amount of energy consumed under the mentioned 3 earthquakes is equal to 0%, 0% and 0% without buckling braces and 40%, 45% and 51% in the case with non-buckling braces and also in the 10- story structure, the amount of energy consumed under the above 3 earthquakes is equal to 1%, 0% and 11% without buckling braces and 35%, 42% and 45% in the case with non-buckling braces. So, it was concluded that the performance of the structure in the case with non-buckling braces is better than in the case without non-buckling braces.

A novel generalized sandwich-type replacement beam for static analysis of tall buildings: Inclusion of local shear deformation of walls

As the length of the shear walls increases, local shear deformation leads to increased error when using classical continuum models for static structural analysis of tall buildings. In this paper, a novel continuous beam of the generalized sandwich type is proposed for the structural analysis of tall buildings that have shear walls of significant length as lateral bracing systems. The proposed continuous beam includes in its formulation an additional kinematic field of rotation due to the local shear deformation of the walls and results from the series coupling of a classic sandwich beam and a shear beam. The equilibrium equations, the constitutive laws, and the boundary conditions of the continuous model are obtained with a variational approach using the Hamilton principle on the relevant Lagrange function. A system of three coupled differential equations leading to sixth-order differential equation and six boundary conditions are obtained. Two closed-form analytical methods are proposed for uniform-height tall buildings. For the case of buildings with variable properties along their height, a numerical method of the modified transfer matrix type is proposed, which is directly derived from the analytical method and avoids the need to calculate the inverse of the classical zero transfer matrix method. The numerical results show the validation of the continuous model and the proposed solution methods. In addition, a parametric analysis of 352 buildings was performed to demonstrate the superiority of the continuous model and the proposed solution methods.

Buckling-Restrained Bracing System with Ultra-High-Performance Fiber Concrete

Recently, buckling-restrained braces (BRBs) have been widely implemented as seismic load resistance systems in buildings to enhance their response against dynamic vibration. However, during catastrophic earthquakes, the steel core in BRB devices fully yields, which causes the BRB to lose its functionality. While the incorporation of various filler materials, such as new high-performance concretes, has the potential to enhance the performance of buckling-restrained braces (BRBs), there remains a notable gap regarding comprehensive research investigating this aspect. Therefore, this study assessed the effect of implementing ultra-high-performance concrete (UHPFRC) as filler material on BRB behavior. For this purpose, the finite element model for the proposed BRB was developed and hysteresis analysis results under incremental cyclic loads were investigated. Then, the prototype of a BRB with UHPFRC concrete was cast and experimentally tested under cyclic loads by using a dynamic actuator. Based on the testing results, a new design for a BRB device named as rubber buckling-restrained brace (RBRB) was developed, implementing hyperelastic rubber components between the steel core and UHPFRC as an additional load-bearing mechanism to enhance the device vibration dissipation capacity. Subsequently, a finite element model of the newly proposed rubber buckling-restrained brace (RBRB) was developed to assess the device’s performance. The analysis results demonstrate a notable enhancement in load capacity and energy dissipation for the RBRB device compared to conventional BRBs.

Monotonic and cyclic sway behaviour of 2-dimensional frames made of pultruded GFRP I-section profiles

This paper presents an experimental study on the structural response of 2-dimensional full-scale frames comprising pultruded GFRP I-section profiles under lateral quasi-static monotonic and cyclic loading, including four different frame configurations, to assess (i) the influence of using different beam-to-column connection systems (one series included cleats and other included cuff parts); (ii) the benefits of using bracings (one series included a cable bracing system); and (iii) the impact of using infill walls (one series included plasterboard panels). The beam-to-column connections and the bracing system were materialized exclusively with stainless steel parts. The results of the monotonic tests showed that the type of beam-to-column connection has considerable influence on the frames’ response, namely on their lateral stiffness; additionally, the frame with bracings and the frame with infill walls exhibited the highest strength and stiffness, respectively, among all series. In the cyclic tests, all frames presented considerable pinching, limiting the energy dissipation; the results showed that the benefits of the infill walls should not be accounted for in design and that the bracing system used is not adequate for seismic areas, as both the plasterboards and the cable bracing system presented non-recoverable deformations/damage that limited their structural contribution from that point forward. The best performing frame series without bracings or walls was simulated using a simple finite element (FE) model. The profiles were modelled using frame elements and the beam-to-column connections were simulated using link elements with the Pivot hysteresis model, calibrated from previous experiments on the beam-to-column connection system. The FE model was able to predict the lateral response with reasonable accuracy, validating this numerical procedure. Then, the FE models were used to evaluate the effects, on the cyclic performance, of including GFRP bracings and a steel plate damper, leading to an improved hysteric response, especially in what concerns the energy dissipation capacity. Overall, the results show that (i) even with ductile connections, the energy dissipation capacity of simple pultruded frames is limited, (ii) although they present high drift capacity; (iii) simple models can be used for design purposes and (iv) they show that the introduction of material-adapted dissipation systems can improve the seismic performance of pultruded frame structures.

Mechanics of superelastic tensegrity braces for timber frames equipped with buckling-restrained devices

This work studies tensegrity bracing systems to be used as energy dissipation devices in next generation, earthquake-proof timber buildings. The examined lightweight and high-strength structures with re-centering capabilities are formed by timber members and pretensioned elements with a superelastic response, which may consist of shape memory alloy wires, cables or bars with energy dissipation capacity. In the case of bars, we assume that such members can be protected against buckling through their encasement in buckling-restrained devices, so as to respond both in tension and in compression. The work on the analyzed bracing systems presents novel results on this type of bi-directional response and the effects derived from the pretension of the superelastic elements, within an analytic formulation of the mechanical response of the structure. It includes an example dealing with a full-scale glued laminated timber frame, which compares the responses of different bracing systems in terms of the lateral force vs. drift ratio curve and ductility factor. The beneficial effects deriving from the use of buckling-restrained devices in an inverted V-braced timber frame are discussed. The presented results highlight the high potential of superelastic braces with tensegrity architecture for the design of timber frames exhibiting markedly high ductility ratios, which considerably surpass those of full-timber or timber-steel systems.

Modelling of Bracing Systems for Seismic Behaviour of High Rise Steel Building

Modelling of Bracing Systems for Seismic Behaviour of High Rise Steel Building

Experimental and numerical investigations on an assembled self-centering buckling-restrained brace with high post-yield stiffness

In order to facilitate the replacement of damaged components and prevent the weak-story mechanism of frame structure after strong earthquakes, a novel assembled self-centering buckling-restrained brace (ASC-BRB) is proposed in this paper. The proposed bracing system is comprised of the buckling-restrained brace (BRB) system and the self-centering (SC) system. The SC system consists of two sets of steel strands and one group of disc springs stacked in series to achieve the goal of large deformability and post-hardening behavior. The detailed configuration, fundamental working mechanism, and restoring force model of the ASC-BRB are first presented. Different from SC systems with bilinear elastic behavior of existing SC-BRBs, the SC system of ASC-BRB exhibits trilinear elastic behavior due to its special configuration. Then, quasi-static tests are conducted to validate the effectiveness of the proposed ASC-BRB. The experimental results indicate that the ASC-BRB has a flag-shaped hysteretic response with excellent self-centering capability, stable energy dissipation capability, and appreciable deformation capacity with a maximum ductility coefficient of 25.58. More importantly, the specimen can exhibit the anticipated post-hardening behavior. The refined numerical model of ASC-BRB is established and verified by the experimental results, which can effectively analyze the mechanical behavior of the main components of ASC-BRB, making up for the deficiency of the tests. According to the problems discovered in the tests and numerical analyses, an improved configuration of the ASC-BRB is proposed and validated by the numerical simulation of the BRB system before and after improvement. The numerical results indicate that the improved BRB system exhibits more stable hysteretic behavior, and the stress levels of the inner and outer tubes become much lower after replacing 1-shaped cores with steel angle cores.

Development of hybrid rubber damper-restrainer (HRDR) system for structures under sever dynamic excitation

Nowadays, high damping rubber materials are extensively implementing in various types of structure to mitigate harmful effect of imposed vibration and dynamic force to the structure. Although, the rubbers exhibit noticeable damping in the shear action, however, de-bounding, shear rupture and delamination of rubber layers under cyclic loads, undermine the load-bearing capacity of the rubber dampers and increase their maintenance costs. Hence, the action of the rubbers is considerably high under applied compression to generate resistant force to restrain the deformation.For this reason, in this research, a new hybrid rubber damper-restrainer (HRDR) system is proposed. The system comprises a high-damping rubber component designed to dissipate applied vibrations, along with a pair of hyper-elastic rubbers intended to restrain displacement. Therefore, the developed HRDR device is capable of dissipating vibrations while restraining large movements to prevent any damage and debounding of the rubber layers and also, protect the structure from excessive displacements.To examine the performance of the proposed device, the numerical model of a HRDR was developed using the finite element simulation and subsequently, nonlinear dynamic analyses were conducted for the 6 storey prototype steel structure furnished with HRDR device. The findings revealed that the structure equipped with the HRDR device exhibited outstanding response against applied earthquake excitation which is proving high efficiency of HRDR device to diminish vibration effect on structure and prevent any excessive deformations. The HRDR device is applicable to any types of framed structures through installing via chevron brace system in steel structures or short wall in reinforced concrete structures. Furthermore, the developed HRDR device can be implemented in bridge structures, between the deck and pier of bridge to effectively dissipate vibrations and restrain the movement of the bridge span under traffic loads.

Rotational behavior of bolted post-to-beam glulam connections with friction damped knee brace

Alternative bracing systems have been widely applied in heavy timber structures due to its contribution to lateral stiffness and strength, while the improvement in the ductility and energy dissipation capability is limited. Friction damped knee brace is applied in this paper to reinforce rotational behavior of the bolted post-to-beam glulam connections. Monotonic and cyclic loading experiments were conducted on fifteen full-scale specimens. The failure modes, elastic stiffness, moment capacity, hysteresis response and energy dissipation were evaluated and analyzed. The experimental results indicated that with the installation of friction damped knee brace, extremely large initial stiffness was achieved and the moment capacity and accumulated energy dissipation of the post-to-beam connections were increased by 207% and 950%, respectively. Moreover, a multi-segment theoretical model was proposed to predict the rotational behavior of the reinforced bolted glulam connections. The theoretically predicted moment-rotation curves showed good agreement with the experimental results.

Nonlinear Dynamic Assessment of a Steel Frame Structure Subjected to Truck Collision

The progressive collapse of structures subjected to a truck collision with ground floor columns is numerically investigated in this paper. For this purpose, a four-story steel building with a dual system (including an intermediate steel moment frame, with a special concentric steel bracing system in the longitudinal (x) direction, and an intermediate steel moment frame in the transversal (y) direction) is considered. The structure, which was designed according to AISC, ASCE7 and 2800 Iranian seismic standard guidelines, is located in seismic-prone area and subjected to eight different truck collision scenarios. The nonlinear dynamic analyses carried out in ABAQUS on a three-dimensional finite element (FE) numerical model include variations in collision features (i.e., mass and speed of the truck, the height of collision point), and are used to support the analysis of expected damage. The presented results confirm that increasing the truck mass and speed increases damage entity for the column and structure. Several influencing parameters are involved in damage location and progressive evolution. The height of the collision point from the ground also significantly affects the magnitude of structural damage, especially in terms of stress peaks in the panel zones for the target column. Finally, the perimeter columns are more vulnerable to impact than corner columns, in structures with dual system as with the examined four-story building. The presence of a bracing system parallel to the impacting vehicle can in fact reduce the deformation—and thus the expected damage—of the adjacent target column. Most importantly, it is shown that the numerically reproduced collision scenarios (and the associated damage configurations) based on truck impact are significantly more severe than those artificially created based on the conventional column removal method (i.e., alternate path (AP) analysis approach), which confirms the importance of more sophisticated numerical calculation procedures to investigate and assess the progressive collapse of structures.

Experimental Study on the Seismic Performance of Seismic Bracing in Important Buildings

Important buildings, such as hospitals and nuclear power facilities, must have basically intact pipe systems to function effectively after an earthquake. To study the seismic fragility and failure mechanisms of different typical seismic bracing system types, this paper conducts a comprehensive series of 34 monotonic and cyclic loading tests on four distinct configurations of seismic bracing. The bearing capacity performance and ductility of the components are evaluated thoroughly by using the area (energy) corresponding to the yield displacement, peak force corresponding displacement, and ultimate displacement of the force–displacement curve in the cyclic loading test. Ultimately, the results comprehensively assess the performance of various test specimens, offering suggestions to address the identified issues.