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1
Hemmati, Ali y Ali Kheyroddin. "BEHAVIOR OF LARGE-SCALE BRACING SYSTEM IN TALL BUILDINGS SUBJECTED TO EARTHQUAKE LOADS". Journal of Civil Engineering and Management 19, n.º 2 (18 de abril de 2013): 206–16. http://dx.doi.org/10.3846/13923730.2012.741613.
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Bracing is a highly efficient and economical method of resisting of lateral forces in a steel structure. The most common types of bracing are those that form a fully triangulated vertical truss. These include the concentric and eccentric braced types. In high-rise buildings, the location and number of bracings is an important limitation to the architectural plan. A similar scheme has been used in larger scale spanning multiple stories and bays in tall buildings which is called large-scale bracing system. Large-scale bracing (LSB) is a particular form of a space truss. It consists of multiple diagonal elements that form a diagonal grid on the face of the structure. In this paper, a 20 story steel frame with different arrangement of bracing systems is analyzed. Linear and static nonlinear (push-over) analyses are carried out and the results presented here. Analytical results show that, the large-scale bracing is more adequate system under the lateral loads. Using LSB in tall buildings, decreases the lateral displacement, drift ratio, uplift forces in foundation and increases the ductility and shear absorption percent of the bracing system. Moreover, the stress ratios in the structural members of LSB system are less than the relevant values in other bracing systems.
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Shamivand, Abbas y Jalal Akbari. "Ring-Shaped Lateral Bracing System for Steel Structures". International Journal of Steel Structures 20, n.º 2 (16 de diciembre de 2019): 493–503. http://dx.doi.org/10.1007/s13296-019-00299-z.
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Lee, Kang Seok. "An Experimental Study on Hybrid Noncompression CF Bracing and GF Sheet Wrapping Reinforcement Method to Restore Damaged RC Structures". Shock and Vibration 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/202751.
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We describe a novel technique for restoration of reinforced concrete (RC) structures that have sustained damage during an earthquake. The reinforcement scheme described here is a hybrid seismic retrofitting technique that combines noncompression X-bracing using CF with externally bonded GF sheets to strengthen RC structures that have sustained damage following an earthquake. The GF sheet is used to improve the ductility of columns, and the noncompression CF X-bracing system, which consists of CF bracing and anchors to replace the conventional steel bracing and bolt connections, is used to increase the lateral strength of the framing system. We report seismic restoration capacity, which enables reuse of the damaged RC frames via the hybrid CF X-bracing and GF sheet wrapping system. Cyclic loading tests were carried out to investigate hysteresis of the lateral load-drift relations, as well as the ductility. The GF sheet significantly improved the ductility of columns, resulting in a change in failure mode. The strengthening effect of conventional CF sheets used in columns is not sufficient with respect to lateral strength and stiffness. However, this study results in a significant increase in the strength of the structure due to the use of CF X-bracing and inhibited buckling failure of the bracing. This result can be exploited to develop guidelines for the application of the reinforcement system to restore damaged RC structures.
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Hadad, Hadad S., Ibrahim M. Metwally y Sameh El-Betar. "Cyclic Behavior of Braced Concrete Frames: Experimental Investigation and Numerical Simulation". Building Research Journal 61, n.º 2 (1 de marzo de 2015): 101–14. http://dx.doi.org/10.2478/brj-2014-0008.
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Abstract RC shear walls have been widely used as the main lateral-load resisting system in medium and high-rise buildings because of their inherent large lateral stiffness and load resistance. But, in general, the energy dissipating capacity of RC shear walls is not very good and it has been found that using the bracing system gives good results. The main purpose of this paper is to study the effect of different types of bracing on the lateral load capacity of the frame. Also, the research contains a comparison between the braced and infilled frames to decide on the best system. The research scheme consists of four frames; the bare frame, two frames the first of which was braced with concrete, the second was braced with steel bracing and the fourth frame was infilled with solid cement bricks. All the specimens were tested under cyclic loading. The results gave some important conclusions; braced and infilled bare frames increased the lateral strength of the bare frame depending on the type of bracing and infill. Also, the different types of bracing and the infill increased the initial stiffness of the bare frame by a reasonable value. The energy dissipation for the braced and infilled frames is always higher than that for the bare frame up to failure. Also, numerical modeling was carried out with the nonlinear software platform (IDARC). The numerical results obtained with the calibrated nonlinear model are presented and compared with the experimental results. Good agreement was achieved between the numerical simulation and the test results.
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Sarhan, Osamah y Mahdy Raslan. "Study of the elastic stiffness factor of steel structures with different lateral load resisting systems". International Journal of Advanced Engineering, Sciences and Applications 1, n.º 2 (30 de abril de 2020): 6–11. http://dx.doi.org/10.47346/ijaesa.v1i2.26.
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Steel structures, like other types of structures, are exposed to different types of loads, including lateral loads such as earthquake and wind. To resist such loading, lateral stiffness has a significant role. In this paper, the elastic stiffness factor (K) for different models of steel structure with various bracing systems and different parameters are compared. The comparison has been performed by analysing and studying the formation of plastic hinges applying the pushover analysis. The results illustrate that the increase in the number of stories reduces the K value, while the increase of span length increases it. Besides, the usage of the bracing system significantly increases the K value.
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Meynerd Rafael, Jusuf Wilson y Alva Yuventus Lukas. "COMPARISON STUDY OF BRACING CONFIGURATION WITH SHEAR LINK IN ECCENTRICALLY BRACED FRAME STEEL STRUCTURE". Journal Innovation of Civil Engineering (JICE) 1, n.º 1 (2 de noviembre de 2020): 7. http://dx.doi.org/10.33474/jice.v1i1.9058.
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The EBF structural system is identified by the use of bracing and link beams as components that work to receive lateral seismic loads. The position of the link beam makes the EBF system have several choices of bracing configuration; D-Braces, Split K-Braces, V-Braces, Split K & Inverted Split K-Braces, Inverted Y-Braces. Structural analysis was carried out on a 10-story building model for the EBF system with different type of bracing configurations using the ETABS software. All models analyzed according to Indonesian Code (SNI 1729:2015 and SNI 1726:2019) to obtain the structural element. Seismic analysis uses the response spectrum analysis method to obtain the structural response parameters in the EBF system. Result of the analysis for all of bracing configuration are shown that Split K-Braces model has the best response parameters when compared to the MRF system. The lowest value for the parameter is owned by Inverted Y-Braces, although overall it is still larger than the MRF system. The bracing configuration greatly affects the response of EBF system due to the behavior that occurs in the link beam, therefore the selection for type of bracing configuration is also important in the EBF system structure design.
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Baijian, Tang, Shao Jianhua, Pei Xingzhu y Gu Sheng. "Mechanical Performance of Mega Steel Frame-Prestressed Composite Bracing Structure". Open Civil Engineering Journal 8, n.º 1 (7 de marzo de 2014): 23–41. http://dx.doi.org/10.2174/1874149501408010023.
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The mega structure has been widely studied and applied due to the clear force transferring way, good structural integrity and flexible layout of diverse building functions. Based on the structure of mega truss or mega frame, the research and application of the mega structure with many kinds of bracing structures become a hot topic in recent years. Mega steel frame-prestressed composite bracing structure with a rigid-flexible composite bracing system composed of rigid Λ-shape steel brace and inverted Λ-shape flexible cable is a new kind of mega structure and this composite bracing system is set up in the mega steel frame. By establishing the three-dimensional finite element model and considering the material and geometric nonlinearity, the structural performance under static load in whole process was analyzed and the energy dissipation as well as failure mode under earthquake is also investigated for this new system in this paper. The results indicate that the lateral deformation is mainly decided by horizontal load and the corresponding curve of lateral displacement has the characteristic of flexure mode as a whole, whereas the deflection of mega beam is mainly governed by vertical load and pretension of cables. The internal force equilibrium of composite brace is decided by vertical load and the degree of force unbalance is about 15% when the fluctuation of vertical load is 20%, but the change of anti-symmetric horizontal load has no effect on the internal force equilibrium. The composite braces not only help the mega beam to bear the vertical load but also greatly enhance the lateral stiffness of main structure and so the lateral stiffness of whole system is relatively uniform. Due to the TMD effects of substructure and additional dampers, the seismic energy is mainly dissipated by dampers and substructure and then the main structure is able to maintain elastic. The desired failure mode of MFPCBS under lateral loads is as follows: the web members of mega beam appear to yield at first, and then the braces between mega column limbs, Λ-shape rigid bracing truss, floor beams between mega column limbs and mega column limbs in order.
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Bagheri, Saman, Siamak S. Shishvan, Majid Barghian y Behzad Baniahmad. "A new energy dissipative cable bracing system". Advances in Structural Engineering 22, n.º 14 (27 de junio de 2019): 3134–46. http://dx.doi.org/10.1177/1369433219858726.
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A special type of cable bracing system comprising a pre-stressed cable and a drum interacting via frictional contact is proposed for lateral resistance of structures, and an analytical solution for the response of this system is developed. The response of the system is highly non-linear due to the existence of frictional contact as well as geometrical effects and it consists of two phases: a linear phase before gross slipping with a relatively high stiffness followed by a non-linear phase with gradually increasing stiffness (i.e. hardening). However, the analytical solution is capable of capturing the whole response with a remarkable accuracy when compared to the finite element model of the system constructed for cross-validation. This analytical solution facilitates studying the effects of various parameters on the behaviour of the system, namely, the coefficient of friction, pre-strain and geometrical aspect ratio. These parameters can be arbitrarily set to achieve a desirable behaviour of the system. The proposed system is capable of undergoing large deformations with symmetrical and stable hysteretic behaviour. The effectiveness of the proposed device in reducing the seismic responses of a building frame is examined using a simplified numerical model.
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Klasson, Anders, Roberto Crocetti, Ivar Björnsson y Eva Frühwald Hansson. "Design for lateral stability of slender timber beams considering slip in the lateral bracing system". Structures 16 (noviembre de 2018): 157–63. http://dx.doi.org/10.1016/j.istruc.2018.09.007.
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Shen, Chao Ming y Jun Yuan Guo. "Static Mechanical Performance of Mega Steel Frame-Prestressed Composite Bracing Structure". Advanced Materials Research 838-841 (noviembre de 2013): 477–82. http://dx.doi.org/10.4028/www.scientific.net/amr.838-841.477.
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Mega steel frame-prestressed composite bracing structure is a new kind of mega structure with a rigid-flexible composite bracing system composed of rigid Λ-shape steel brace and inverted Λ-shape flexible cable set up in the mega steel frame. By establishing the three-dimensional finite element model and considering the material and geometric nonlinearity, this paper analyzed the structural performance under whole process of static loading. The results indicate that the lateral deformation is mainly determined by horizontal load and the corresponding lateral deformation curve is bending type on the whole, whereas the deflection of mega beam is mainly governed by vertical load and pretension of cables.
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Tremblay, Robert y Siegfried F. Stiemer. "Seismic behavior of single-storey steel structures with a flexible roof diaphragm". Canadian Journal of Civil Engineering 23, n.º 1 (1 de febrero de 1996): 49–62. http://dx.doi.org/10.1139/l96-006.
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The nonlinear response of 36 rectangular single-storey steel buildings subjected to historical earthquake accelerograms is examined. The buildings were designed according to current Canadian practice. The lateral load resisting system of the buildings includes a flexible metal roof deck diaphragm and vertical bracing located along the exterior walls. The results indicate that the fundamental period of the structures, the maximum drift, the forces and deformations in the roof diaphragm, and the ductility demand on the vertical bracings cannot be adequately predicted with existent design provisions. Tentative design guidelines are proposed on the basis of the results obtained in the study. Key words: analysis, design, seismic, dynamic, structures, steel, roof diaphragm.
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Liu, Li, Bo Wang, Ya Nan Liu y Ju Chao Wang. "Analysis on Lateral Deformation of High-Formwork in Different Column’s Spacing of Bridging". Applied Mechanics and Materials 580-583 (julio de 2014): 2228–31. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.2228.
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Setting bracing is conducive to stabilize formwork support in high-formwork system. ABAQUS was used to build the calculating model of high-formwork system to simulate and analyse lateral deformation of high-formwork in different column’s spacing of bridging. The results show, increasing column’s spacing of bridging can add the whole lateral displacement of high-formwork, but, it is not obvious. Increasing appropriately column’s spacing can save material during construction.
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Linde, Lukas D., Jessica Archibald, Eve C. Lampert y John Z. Srbely. "The Effect of Abdominal Muscle Activation Techniques on Trunk and Lower Limb Mechanics During the Single-Leg Squat Task in Females". Journal of Sport Rehabilitation 27, n.º 5 (1 de septiembre de 2018): 438–44. http://dx.doi.org/10.1123/jsr.2016-0038.
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Context: Females suffer 4 to 6 times more noncontact anterior cruciate ligament (ACL) injuries than males due to neuromuscular control deficits of the hip musculature leading to increases in hip adduction angle, knee abduction angle, and knee abduction moment during dynamic tasks such as single-leg squats. Lateral trunk displacement has been further related to ACL injury risk in females, leading to the incorporation of core strength/stability exercises in ACL preventative training programs. However, the direct mechanism relating lateral trunk displacement and lower limb ACL risk factors is not well established. Objective: To assess the relationship between lateral trunk displacement and lower limb measures of ACL injury risk by altering trunk control through abdominal activation techniques during single-leg squats in healthy females. Design: Interventional study setting: movement and posture laboratory. Participants: A total of 13 healthy females (21.3 [0.88] y, 1.68 [0.07] m, and 58.27 [5.46] kg). Intervention: Trunk position and lower limb kinematics were recorded using an optoelectric motion capture system during single-leg squats under differing conditions of abdominal muscle activation (abdominal hollowing, abdominal bracing, and control), confirmed using surface electromyography. Main Outcome Measures: Lateral trunk displacement, peak hip adduction angle, peak knee abduction angle/moment, and average muscle activity from bilateral internal oblique, external oblique, and erector spinae muscles. Results: No differences were observed for peak lateral trunk displacement, peak hip adduction angle, or peak knee abduction angle/moment. Abdominal hollowing and bracing elicited greater muscle activation than the control condition, and bracing was greater than hollowing in 4 of 6 muscles recorded. Conclusion: The lack of reduction in trunk, hip, and knee measures of ACL injury risk during abdominal hollowing and bracing suggests that these techniques alone may provide minimal benefit in ACL injury prevention training.
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KIM, C. W., M. KAWATANI, T. KANBARA y N. NISHIMURA. "SEISMIC BEHAVIOR OF STEEL MONORAIL BRIDGES UNDER TRAIN LOAD DURING STRONG EARTHQUAKES". Journal of Earthquake and Tsunami 07, n.º 02 (junio de 2013): 1350006. http://dx.doi.org/10.1142/s1793431113500061.
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This paper investigated dynamic responses of steel monorail bridges incorporating train-bridge interaction under strong earthquakes. Two types of steel monorail bridges were considered in the study: a conventional type with steel track-girder; an advanced type with composite track-girder and simplified lateral bracing system. During strong earthquakes, monorail train was assumed standing on the track-girder of monorail bridges. Observations through the analytical study showed that considering the monorail train as additional mass rather than a dynamic system in numerical modeling overestimated effect of the train load on seismic performance of monorail bridges. Earlier plastic deformations at the end bracing of the girder system absorbed seismic energy and reduced the stress at the pier base.
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Michel, Kenan, Wolfram Jäger y Frank Steinigen. "Redistribution of internal forces in the lateral bracing system / Schnittgrößenumlagerungen bei der Gebäudeaussteifung". Mauerwerk 19, n.º 6 (diciembre de 2015): 441–52. http://dx.doi.org/10.1002/dama.201500679.
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Abd Samat, Roslida, Muhammad Fikri Khairudin, Muhammad Haziq Din, Gamil Gamal Ali, Abu Bakar Fadzil y Suhaimi Abu Bakar. "Comparative Structural Performance Of Diagrid and Bracing System in Mitigation of Lateral Displacement". IOP Conference Series: Earth and Environmental Science 220 (21 de febrero de 2019): 012025. http://dx.doi.org/10.1088/1755-1315/220/1/012025.
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Boostani, Maryam, Omid Rezaifar y Majid Gholhaki. "Introduction and seismic performance investigation of the proposed lateral bracing system called “OGrid”". Archives of Civil and Mechanical Engineering 18, n.º 4 (septiembre de 2018): 1024–41. http://dx.doi.org/10.1016/j.acme.2018.02.003.
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Răcănel, Ionuţ Radu, Vlad Daniel Urdăreanu y Andrei Radu. "“Bowstring” Arches in Langer System Without Wind Bracing". Romanian Journal of Transport Infrastructure 4, n.º 1 (1 de julio de 2015): 67–77. http://dx.doi.org/10.1515/rjti-2015-0032.
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Abstract Arch bridges are slender structures and can be efficiently used in the range of medium to large spans. These structures have an improved aesthetic aspect and in the same time a low construction height, with obvious advantages regarding reduced costs in the infrastructuers and their foundations. For this type of structures usually composite or orthotropic decks are used. Lately, innovative solutions have been used in designing arch bridges, especially discarding the top wind bracing system. The level of axial forces and bending moments in the arches and tie imply the design of sections with sufficient stiffness and strength in both directions in order to ensure the general stability of the arches, without the need for top wind bracing. Moreover, the cross section of the arches is not constant, but shifts in accordance with the variation of the bending moments, in order to ensure their lateral stability. This paper studies a road bridge with parallel Bowstring arches, with a span of 108m and a carriageway 7.00m wide, sustained by a deck made up of crossbeams 2m apart and a concrete slab. The main beams are held by ties arranged in the Langer system, 10 to 14m apart from each other. The sag of the arches is 18m high. The analyzed structure was proposed for construction in the city of Oradea and is used for crossing the “Crişul Repede” river, between Oneştilor street on the left bank and the Sovata, Fagului and Carpaţi streets on the right bank. The performed analyses have the following two main objectives: to establish the critical load for which the failure of the arches occurs by instability and to underline the influence of different wind bracing systems on the bridge’s collapse loads respectively.
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Bush, Thomas D., Loring A. Wyllie y James O. Jirsa. "Observations on Two Seismic Strengthening Schemes for Concrete Frames". Earthquake Spectra 7, n.º 4 (noviembre de 1991): 511–27. http://dx.doi.org/10.1193/1.1585640.
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A large-scale model of a nonductile concrete frame with columns susceptible to shear failure was retrofitted with two strengthening schemes. In the first scheme, full-height concrete piers were added to the original columns. Tests showed that the strengthened column section behaved monolithically and the failure mode was shifted to hinging of the spandrel beams. Large increases in frame strength and stiffness were also realized. In the second scheme, a steel X-bracing system was attached to the frame's exterior face. Lateral capacity was governed by yielding and buckling of the braces. The system exhibited substantially increased frame stiffness and strength. Both systems were quite constructable and relied extensively on epoxy-grouted dowels. The pier system required a lower level of construction skill but was somewhat more labor intensive. The bracing system required a higher level of construction skill due to local variations in fit-up requirements and the need for field welding.
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Li, Guo Chang, Fei Tian, Zhi Jian Yang y Guo Zhong Zhang. "Finite Element Analysis on K-Type External Braced Steel Frame System". Key Engineering Materials 763 (febrero de 2018): 495–501. http://dx.doi.org/10.4028/www.scientific.net/kem.763.495.
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The concept of moment resisting frames with K-type external braces is proposed to increase the lateral stiffness, which has short external span and large lateral stiffness. In order to investigate the lateral stiffness, overstrength coefficient and the reduction factor of K-type external brace under horizontal load, ABAQUS was applied to study the different slenderness ratios (from50 to 150) of K-type external steel braced frames. The results showed that the lateral load and displacement curve can be divided into elastic stage, the buckling of the compressive brace-yield of the tensile brace stage and plastic stage. The overstrength of K-bracing is related to the potential bearing capacity of the frame when the compressive brace buckled, and the potential growth of the tensile brace. The overstrength coefficient increases with increasing of the brace slenderness ratio. The range of recommended values of slenderness ratios of K-type external steel braces and design values of unbalanced force of column sections are proposed.
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Yang, Wei Guo y Xing Po Li. "Effects of Different Structural Systems on Lateral Rigidity of Steel Structural Frames". Advanced Materials Research 287-290 (julio de 2011): 1877–81. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.1877.
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To understand the effect of filler walls on lateral rigidity of steel frame, Some methods such as theoretical analysis, finite elements calculation and experiment study were carried out to do research on the resistant-lateral effectiveness and the steel consumption of the three different structural systems, namely steel frame, frame-bracing and frame-board. The results show that the frame-board system can improve the structural lateral rigidity effectively, and will enhance the structural fundamental natural frequency sharply as well as reducing the structural steel consumption. It is an effective method for improving structural lateral rigidity to utilize the frame filled with wall panel. Making fully use of lateral rigidity of the wall panel can reduce the size of beam and column cross-section, material consumption and project cost.
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Fu, Yaomin y Sheldon Cherry. "Simplified seismic code design procedure for friction-damped steel frames". Canadian Journal of Civil Engineering 26, n.º 1 (1 de febrero de 1999): 55–71. http://dx.doi.org/10.1139/l98-043.
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This paper describes the development of a proposed seismic design procedure for friction-damped steel structures, which employs the lateral force provisions used in many modern building codes. Closed-form expressions are first derived that relate the normalized response of a single degree of freedom friction-damped system with the system parameters, such as bracing stiffness ratio, damper slip ratio, and frame member ductility. A parametric analysis is then used to reveal that the seismic displacement of a friction-damped frame can be controlled by combining the frame stiffness with the bracing stiffness of the friction damper component, while the seismic force can be controlled by the damper slip force. A force modification factor (equivalent to the code R-factor) and displacement estimate for a friction-damped system are next determined. The single degree of freedom results are subsequently used to develop expressions for dealing with the multi degree of freedom situation, which permits the seismic lateral force design procedure adopted by many current building codes to be applied to friction-damped systems. The proposed procedure allows the frame response to be controlled so that the displacement can be limited to small magnitudes and the overall structural shape to an essentially straight-line deformation. Design examples illustrate that friction-damped frame systems are economical and offer a better overall response performance than that provided by conventional systems under the design earthquake.Key words: passive energy dissipation system, friction damper, steel frame, design procedure, static analysis.
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Rocha, Arthur L., Marcelo de A. Ferreira, Wilian dos S. Morais y Bruna Catoia. "The Use of Moment-Resisting Frames and Braced Frames for Lateral Stability of Multy-Storey Precast Concrete Structures". Solid State Phenomena 259 (mayo de 2017): 173–77. http://dx.doi.org/10.4028/www.scientific.net/ssp.259.173.
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Precast structures for multi-storey buildings can be designed with economy, safety and high performance. However, depending on the height of the building and the intensity of the lateral loads, the lateral stability system must be carefully chosen in order to maximize the global structural performance. In Brazil, the most common method for lateral stability is achieved by moment resisting precast-frames, wherein the moment-rotation response of the beam-column connections are responsible to provide the frame action, which will govern the distribution of internal forces and the sway distribution along the building height. On the other hand, in Europe, bracing systems comprised by shear walls or infill walls are mostly used, wherein beam-column connections are designed as hinged. The aim of this paper is to present a comparison between these methods for lateral stability, applying nine structural simulations with moment resisting precast-frames, shear walls and infill walls solutions, divided in three groups - 3 building with 5 storeys (21 meters high), 3 buildings with 10 storeys (41 meters high) and 3 building with 20 storeys (81 meters high). All first storeys are 5 meters high, while all the others are 4 meters high. The results from all structural analyses are compared. As conclusion, while moment-resisting beam-column connections are more feasible for applying in low-rise precast buildings, the use of shear walls and infill walls are more efficient for tall buildings due to decrease of lateral displacements, having a reduction of second order effects but also increasing the reactions at the foundations of bracing elements.
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Veladi, H. y H. Najafi. "Effect of Standard No. 2800 Rules for Moment Resisting Frames on the Elastic and Inelastic Behavior of Dual Steel Systems". Engineering, Technology & Applied Science Research 7, n.º 6 (18 de diciembre de 2017): 2139–46. http://dx.doi.org/10.48084/etasr.1040.
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According to most valid Design Codes including the Iranian Seismic Design Code (Standard No. 2800), moment resisting frames in dual systems must have the ability of resisting the 25% of the total lateral load of the dual system independently. This study is conducted to investigate the implementation of this rule for dual steel structures with two types of steel braced frame. Also, its effect on the strength of the structure and the distribution of lateral load between the frames and the bracing system is evaluated. In order to investigate the effect of that rule, structural models with 5, 10 and 15 floors are modeled. Nonlinear static analysis is employed and results are discussed. Following the Standard No. 2008 seems to increase the structure’s lateral resistance and decrease the number of elements entered into the inelastic behavior stage. In general, the structure has a more desirable inelastic behavior.
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Masri, Adnan C. y Subhash C. Goel. "Seismic Design and Testing of an RC Slab-Column Frame Strengthened by Steel Bracing". Earthquake Spectra 12, n.º 4 (noviembre de 1996): 645–66. http://dx.doi.org/10.1193/1.1585904.
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This study is concerned with developing a rational design procedure for use of ductile steel bracing for strengthening existing seismically “weak” RC slab-column building structures. A one-third scale, two-bay, two-story RC slab-column frame model was selected to represent existing seismically inadequate structures of its type. The design procedure, construction and test results of the steel bracing system for strengthening the RC frame are presented in this paper. The strengthened frame was subjected to a combination of gravity and cyclic lateral loads up to 2% overall frame drifts. The behavior of the strengthened frame improved dramatically over that of the bare RC frame. A maximum 2.75% drift in the first story was reached which is highly probable during severe earthquake motions.
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Nims, Douglas K., Phillip J. Richter y Robert E. Bachman. "The Use of the Energy Dissipating Restraint for Seismic Hazard Mitigation". Earthquake Spectra 9, n.º 3 (agosto de 1993): 467–89. http://dx.doi.org/10.1193/1.1585725.
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This paper describes the mechanical operation and presents parametric studies for the Energy Dissipating Restraint (EDR). The EDR is a strongly self-centering passive friction-based seismic energy dissipator with a wide range of hysteretic behaviors. In the behaviors of most interest in seismic design, the slip load is proportional to displacement. Typically the EDR would be installed in a building as part of the bracing system which resists seismically induced lateral forces.
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Yang, Shi Ruo y Dan Qing Chen. "Railway Steel Truss Coefficient of Lateral Force Distribution". Advanced Materials Research 304 (julio de 2011): 359–65. http://dx.doi.org/10.4028/www.scientific.net/amr.304.359.
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This paper illustrates the internal force calculation of the railway steel truss girder under the action of lateral load q by using the finite element method for truss segment. Load q is distributed with partition coefficients a1, a2 respectively on the top and bottom longitudinal bracing in conventional way and calculated as planar articulate. When two forces calculated respectively by using the spatial analysis and planar structure method are equal, lateral force distribution coefficient a1, a2 can be obtained. In the end of this paper we take examples of simple through beam of 48m, 64m, 80m, 144m, 192m, continuous through beam of 2×64m,3×64m, dual continuous deck beam of 2×64m and dual simple through beam of 64m and get the partition coefficient of the floor system plane, 0.77, and the other plane is 0.39.
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Yin, Ling Feng, Long Tan, Gan Tang, Min Zhang y Zhao Xin Zheng. "Structure Composition and Mechanical Principle of Assembled Self-Supported Warehouse". Advanced Materials Research 838-841 (noviembre de 2013): 574–78. http://dx.doi.org/10.4028/www.scientific.net/amr.838-841.574.
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This paper describes the structure composition and characteristic of assembled self-supported warehouse. And its mechanical principle is introduced and compared with both the assembled pallet rack and the building structure. The assembled self-supported warehouse combines the two structure systems effect. The longitudinal horizontal load is transferred to foundation by means of roof truss and multi-pan portal rigid frame and the lateral horizontal load is transferred by means of spine bracing system and semi-rigid frame. Load on roof and goods load are transferred separately from roof truss and beams to columns, then these loads are transferred to foundation.
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Shahmohammadi, Amir, James B. P. Lim y George Charles Clifton. "Portal Frames with a Novel Cold-Formed Tapered Box-Section". Key Engineering Materials 763 (febrero de 2018): 301–9. http://dx.doi.org/10.4028/www.scientific.net/kem.763.301.
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This paper introduces a novel steel portal frame system, in which cold-formed nested tapered box members are used in the design. The bird and dust proofing features of the system make it useful for applications where clean work areas are required, such as food, storage, and manufacturing industries. The new section used in the portal frames comprises two cold-formed channels welded to each other, forming a box-shaped steel member, either tapered or prismatic along its length. Such sections possess high torsional stiffness compared with the conventional I-sections; therefore, lateral bracing employed for the flexural-torsional buckling suppression of I section portal frames is mostly unnecessary. A comparative study, taking into account the cost of steel, painting, bird proofing and lateral bracing, is conducted between a number of portal frames with the proposed box-sections and the conventional I-sections. An analysis and design code, incorporating the Genetic Algorithm (GA), is developed to optimise the weight of the designed frames. The results indicate that the novel portal frame system is economically viable with additional benefits of bird and dust proofing. To investigate the failure modes and verify design procedure of the new portal frame, an experimental testing program is undertaken in University of Auckland. The test results show excellent behaviour and good agreement with the numerical models but have been completed too recently to be included in this paper.
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Nurchasanah, Yenny, Muhammad Ujianto y Abdul Rochman. "Diagonal reinforcement as strengthening to increase the stiffness and strength of concrete frame". MATEC Web of Conferences 195 (2018): 02033. http://dx.doi.org/10.1051/matecconf/201819502033.
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Two test objects of concrete frame behavior against lateral loading were performed by applying structural analysis with the wall as diagonal reinforcement in modeling. The results of the structural analysis indicated that concrete frames with walls have better performance than concrete frames without walls. Twelve objects consisting of the frame without the wall, frame with the wall, and frames with a group of steel and bamboo as diagonal reinforcement at brick walls and concrete panel walls were tested at the laboratory with monotonic lateral forces that work parallel to the wall as the illustration of earthquake loads. The diagonal reinforcement elements can spread the force received by the wall and increase the strength of the wall as well as enhance the stiffness of the structural system at once. Bracing contributes to increasing the strength, especially in resisting the compressive forces due to the earthquake loads. Deformation occurs in the opposite direction between compression path and tension path at the diagonal area. The failure in the concrete frame can be caused by the in-plane force parallel to the wall. Bamboo is quite effective to be used as a substitute for steel reinforcement as bracing material despite its shortage of steel quality.
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Akbari, Azin, Erfan Ordookhani y Mohammad Reza Pasaeian. "The Consideration of Response Modification Factor of L-Shaped Structures by Using Adaptive Pushover Analysis Method and Comparison with Traditional Pushover Method". Civil Engineering Journal 4, n.º 8 (31 de agosto de 2018): 1955. http://dx.doi.org/10.28991/cej-03091130.
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In the most of regulations, reduction factor of seismic force depends only on the kind of lateral loading system, but research has shown that this factor is a function of many factors such as period and modal characteristics of the structure, the height and especially form of plan in the building. Due to the complexity of nonlinear dynamic analysis method, today, nonlinear static analysis method called pushover, as a practical appropriate tool has developed in field of earthquake engineering based on function frequently. But traditional pushover analysis method have defects that can be noted Including the stability of lateral load pattern form, did not consider the impact of higher modes or impact of more efficient modes and lack of consideration of the stiffness matrix of member or the entire of structure changes in step of analysis. In recent years a number of researchers have proposed using adaptive load pattern, in this methods, lateral load pattern have changed and adapting in during analysis based on momentary stiffness matrix of structures. In this paper we investigate the response modification factor in L-shaped geometric asymmetry by using SAP software, Pushover analysis used in this study is divided into two categories pushover with constant load pattern (traditional method) and pushover with the adaptive load pattern (adaptive). So, it is studied building with L-shaped asymmetrical plan, with moment frame double structural system - bracing and number of floors 5, 10, 15 and 20, with four different bracing plan types at considering frames, and the end were compared obtained response modification factor from the two methods for these buildings.
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Puértolas-Pascual, E. y O. Mateus. "A three-dimensional skeleton of Goniopholididae from the Late Jurassic of Portugal: implications for the Crocodylomorpha bracing system". Zoological Journal of the Linnean Society 189, n.º 2 (31 de octubre de 2019): 521–48. http://dx.doi.org/10.1093/zoolinnean/zlz102.
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Abstract We here describe an articulated partial skeleton of a small neosuchian crocodylomorph from the Lourinhã Formation (Late Jurassic, Portugal). The skeleton corresponds to the posterior region of the trunk and consists of dorsal, ventral and limb osteoderms, dorsal vertebrae, thoracic ribs and part of the left hindlimb. The paravertebral armour is composed of two rows of paired osteoderms with the lateral margins ventrally deflected and an anterior process for a ‘peg and groove’ articulation. We also compare its dermal armour with that of several Jurassic and Cretaceous neosuchian crocodylomorphs, establishing a detailed description of this type of osteoderms. These features are present in crocodylomorphs with a closed paravertebral armour bracing system. The exceptional 3D conservation of the specimen, and the performance of a micro-CT scan, allowed us to interpret the bracing system of this organism to assess if previous models were accurate. The characters observed in this specimen are congruent with Goniopholididae, a clade of large neosuchians abundant in most semi-aquatic ecosystems from the Jurassic and Early Cretaceous of Laurasia. However, its small size, contrasted with the sizes observed in goniopholidids, left indeterminate whether it could have been a dwarf or juvenile individual. Future histological analyses could shed light on this.
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Chi, Pei, Jun Dong, Wenlong Tian y Dafu Cao. "Nonlinear Seismic Response of Multistory Steel Frames with Self-Centering Tension-Only Braces". Applied Sciences 10, n.º 5 (6 de marzo de 2020): 1819. http://dx.doi.org/10.3390/app10051819.
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The self-centering tension-only brace (SC-TOB) is a new and innovative bracing system that provides both a flag-shaped recentering hysteresis and load mitigation to structures. This paper presents an extensive investigation of the nonlinear seismic response of multistory steel frames built with SC-TOBs to internal force, drift, and energy dissipation. Pushover analysis subjected to two lateral load distributions and nonlinear dynamic analysis under ground motion ensembles corresponding to four hazard levels were conducted. The SC-TOBs can be designed to serve as conventional tension-only braces (TOBs) only providing lateral stiffness during minor earthquakes, to function with energy dissipation as intensity increases, and to fully recenter a structure even after severe earthquakes. The findings show that with an increase in the earthquake intensity, both the force response and drift response of the SC-TOB frames (SC-TOBFs) increased; however, the force distribution and drift distribution shapes of the SC-TOBFs remained almost constant. The SC-TOBFs generally experienced more energy dissipation in the lower parts of the building, while the upper stories dissipated almost no energy under certain load conditions, suggesting that the bracings on those stories could be replaced by conventional TOBs for economy. It is demonstrated that the SC-TOBs have immense potential to effectively improve seismic resilience to structures such that rehabilitation costs and operational disruptions after earthquakes are minimized.
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FitzGerald, T. F., Thalia Anagnos, Mary Goodson y Theodore Zsutty. "Slotted Bolted Connections in Aseismic Design for Concentrically Braced Connections". Earthquake Spectra 5, n.º 2 (mayo de 1989): 383–91. http://dx.doi.org/10.1193/1.1585528.
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The use of concentrically braced steel frames to satisfy lateral force requirements is a common design practice in regions of strong seismicity. They provide a very efficient means of fulfilling the dual objectives of earthquake resistant design, that is, damage control and collapse prevention. While tensile yielding and inelastic buckling of bracing elements provide the basic energy absorbing mechanism, there are inherent problems with member behavior under multiple cycles of inelastic deformations. Inelastic energy dissapation, however, may also be provided by friction resistance in slotted bolted connections, thus eliminating the need for inelastic member buckling. Limited laboratory tests indicate that this concept may be a viable alternative for use as a lateral force resisting system for both new construction and the seismic upgrading of existing structures.
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Naderi, Arash y Mohammad Reza Sohrabi. "Analyzing Effective Length Factor of OBS Members". Advanced Materials Research 255-260 (mayo de 2011): 40–44. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.40.
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Using OBS (Off-center Bracing System) is one of the methods to make buildings resistant to the lateral Loads. This kind of brace has a great tendency to out of plane buckling. So, due to the lack of formal regulations, analyzing out of plane effective length of its members is important. In this paper, buckling load of 15 one-story frames is obtained and then out of plane effective length factor of the longer member is calculated. Finally, as buckling of one of the members causes the system to lose its stability, the mentioned effective length factor is introduced as out of plane effective length factor for all OBS members.
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Pourali, Atefeh, Rajesh P. Dhakal, Gregory MacRae y Ali Sahin Tasligedik. "Fully Floating Suspended Ceiling System: Experimental Evaluation of Structural Feasibility and Challenges". Earthquake Spectra 33, n.º 4 (noviembre de 2017): 1627–54. http://dx.doi.org/10.1193/092916eqs163m.
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Full scale shake table testing is conducted on a novel type of suspended ceiling called fully floating ceiling system, which is freely hung from the floor above lacking any lateral bracing and connections with the perimeters. A gap is provided on all sides of the ceiling. Throughout different tests, a satisfactory agreement between the fully floating ceiling response and simple pendulum theory was demonstrated. When subjected to input motions with significant energy in the floating ceiling's resonant frequency, the horizontal displacement of the ceiling exceeded the gap width resulting in pounding induced large acceleration pulses. To mitigate such effects, the perimeter gap fillers of a compressible material are proposed. The addition of perimeter isolation was found effective in inducing extra damping and protecting the ceiling from pounding impact; resulting in much reduced ceiling displacements and accelerations. Throughout the tests a single panel dislodgement was observed as the only instance of damage.
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Mazzolani, Federico M., Gaetano Della Corte y Mario D’Aniello. "EXPERIMENTAL ANALYSIS OF STEEL DISSIPATIVE BRACING SYSTEMS FOR SEISMIC UPGRADING". JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 15, n.º 1 (31 de marzo de 2009): 7–19. http://dx.doi.org/10.3846/1392-3730.2009.15.7-19.
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Energy dissipating devices, such as metallic ductile dampers, could represent one reliable system for seismic performance upgrading of reinforced concrete (RC) structures. This paper illustrates the significant improvement to the seismic response of RC structures equipped with dissipative bracing systems, such as eccentric braces (EBs) and buckling restrained braces (BRBs). In fact, the results of experimental tests carried out on two similar two‐storey one‐bay RC structures, respectively equipped with EBs and BRBs, are described. Referring to EBs, 3 lateral loading tests have been performed. Each test is characterized by shear links with bolted end‐plate connections. Different design criteria have been applied in the design of the connections. In the first test, capacity design criteria have not been considered. In the second test, a capacity design criterion has been applied, with a link shear over‐strength factor equal to 1.5. In the third test, a design criterion similar to the one adopted for the second test has been implemented, but with a larger over‐strength factor. In case of BRBs, two types of ‘only‐steel’ braces have been tested: one type was made using two buckling‐restraining rectangular tubes that are fully welded together with steel plates; the other type is detachable, being made again with two buckling‐restraining rectangular tubes but joined together by means of bolted steel connections. In both cases, the internal yielding core was a rectangular steel plate. The experimental results of both bracing systems are encouraging about the possibility to use these devices for improving the seismic resistance of existing RC structures. Santrauka Didinant gelžbetoninių pastatų atsparumą seisminiams poveikiams, gali būti naudojami energiją sugeriantys metaliniai slopintuvai. Straipsnyje parodoma, kaip tokios slopinančios sistemos, kaip necentriniai ryšiai ir klupimą suvaržantys ryšiai, gali iš esmės gerinti pastato seisminę elgseną. Pateikiami dviejų panašių vienos angos gelžbetoninių pastatų su minėtaisiais ryšiais eksperimentiniai tyrimų rezultatai. Tyrimai parodė, kad abi suvaržymo sistemos gerina eksploatuojamų gelžbetoninių pastatų atsparumą seisminiams poveikiams.
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Malik, Hawraa Sami y David A. M. Jawad. "Brace Forces in Horizontally Curved Steel Box Girder with Two Types of Lateral Bracing System by Using ANSYS Program". IOP Conference Series: Materials Science and Engineering 1090, n.º 1 (1 de marzo de 2021): 012098. http://dx.doi.org/10.1088/1757-899x/1090/1/012098.
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Daley, B. J., J. L. Ralston, T. D. Brown y R. A. Brand. "A Parametric Design Evaluation of Lateral Prophylactic Knee Braces". Journal of Biomechanical Engineering 115, n.º 2 (1 de mayo de 1993): 131–36. http://dx.doi.org/10.1115/1.2894112.
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Six major mechanical design variables characterizing single-upright lateral prophylactic knee braces were studied experimentally, using a generic modular brace (GMB). Impulsive valgus loading tests were conducted with the GMB applied to a surrogate leg model. The surrogate involved anatomically realistic aluminum-reinforced acrylic components to model bone, and expendable polymeric blanks to mimic the major knee ligaments. Behavior of the surrogate system reasonably reproduced that of human cadaveric knees under similar loading conditions. Load at failure of the medial collateral ligament (MCL) analog, gross knee stiffness, and MCL relative strain relief were measured for each of twelve parametric brace design permutations. Compared to the unbraced condition, bracing provided statistically significant increases in valgus load uptake at failure and in MCL strain relief. Increasing the dimensions of individual brace components (hinge length and offset; upright length, breadth, and thickness; cuff area), relative to those of a GMB baseline configuration deemed representative of current commerical products, failed to achieve statistically significant improvements in brace performance. However, most below-baseline dimensioning of individual components did significantly compromise GMB performance. These surrogate test data indicate that geometric modifications of current single-upright lateral brace designs are unlikely to substantially improve upon the fairly modest valgus load protection afforded by this class of devices.
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Alborzi, M., H. Tahghighi y A. Azarbakht. "Numerical comparison on the efficiency of conventional and hybrid buckling-restrained braces for seismic protection of short-to-mid-rise steel buildings". International Journal of Advanced Structural Engineering 11, n.º 4 (11 de octubre de 2019): 439–54. http://dx.doi.org/10.1007/s40091-019-00244-8.
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Abstract Buckling-restrained brace (BRB) is a specific kind of bracing system which has an acceptable energy dissipation behavior in a way that would not be buckled in compression forces. However, considerable residual deformations are noticed in strong ground motions as a result of the low post-yield stiffness of the BRBs. The seismic performance of a modern lateral load resisting system, which is called the hybrid BRB, and its conventional counterpart are assessed and compared in this paper. Multiple plates with different stress–strain behavior are used in the core of this new innovative system, and this is its difference with the existent BRBs. Nonlinear static and incremental dynamic analyses are carried out for three building frames with different structural heights, which use conventional and hybrid BRB systems. To carry out response history analyses, the FEMA P695 far-field earthquake record set was adopted in different hazard levels. The hybrid BRBs are shown to have superior seismic performance in comparison with the conventional systems based on the response modification factor and the damage measures including residual displacements and inter-story drift ratios.
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Markham, Charles H. "Vestibular Control of Muscular Tone and Posture". Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 14, S3 (agosto de 1987): 493–96. http://dx.doi.org/10.1017/s0317167100037975.
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ABSTRACT:The vestibulospinal system helps to maintain upright posture and head stability. The semicircular canals and their short latency connections to the neck motoneurons, largely via the medial vestibulospinal tract, respond to angular accelerations so as to stabilize the head in space. The paired otolith organs, the utricles placed approximately horizontally, and the saccules vertically, respond to linear acceleration including gravity. Their influence leads, via the lateral vestibulospinal tract, to excitation of ipsilateral extensor motoneurons of the limbs and trunk, and to inhibition of reciprocal flexor motoneurons. Linear displacement of the otoliths leads to bracing of the limbs and body so as to maintain upright posture, and to extend the limbs so as to help in landing after sudden falls.
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Sadeghpour, Mahmoud. "Technical-Economical Comparison Between Vertical Link Beam and Knee Brace Systems in Mid-Rise Steel Buildings". Journal of Applied Engineering Sciences 9, n.º 1 (1 de mayo de 2019): 115–20. http://dx.doi.org/10.2478/jaes-2019-0015.
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Abstract In knee brace and shear panel systems, unlike eccentric braced frames, energy absorption is achieved through plastic deformation when sub-members yield by shear forces or bending moments caused by bracing members during severe earthquakes. Several studies have been conducted on the behavior of these two systems which resulted in design methods to obtain the best structural performance. The present study attempted to design frames using these methods, and then to compare them in terms of technical and economic factors. In this regard, to obtain a pattern of the frames behavior, a 3-span 5-storey frame was modeled for three different types of brace system (coaxial, knee and shear panel) using ANSYS software. After performing pushover nonlinear static analysis, behavior coefficients were determined and the force-lateral displacement curves of the systems were compared. In the next step, 3-span 5- 8- and 12-storey frames were analyzed and designed using ETABS software and were compared in terms of the parameters such as relative lateral displacement, normal period of system, structural weight, and shear force into foundation. The results indicate that using the above-mentioned systems, structure will exhibit more ductility which leads to reduced design base shear. The forces applied to main structural members (beams, columns, and braces) are reduced by the use of knee brace and shear panel systems. This will affect the design and sometimes increases or decreases weight of these members.
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Campiche, Alessia. "Innovative UHS Steel Material for Tension-Only Braced CFS Walls". Key Engineering Materials 873 (enero de 2021): 25–31. http://dx.doi.org/10.4028/www.scientific.net/kem.873.25.
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Lightweight Steel (LWS) systems, made of Cold Formed Steel (CFS) profiles, are widespread in seismic areas and often preferred to traditional systems. Improving structural performances in order to have higher building is now the goal, which could be achieved thanks to the use of steel innovative material. In particular, to increase the seismic performances of CFS buildings, the University of Naples “Federico II”, in cooperation with the Italian company Lamieredil S.p.A., has developed an innovative Lateral Force Resisting System (LFRS). The LFRS mainly consists of CFS frame (studs and tracks) braced by “V” shaped pre-tensioned Ultra High Strength (UHS) steel bars. The bracing was designed to be able to limit global displacement of structure, working as elastic spring, and to dissipate seismic energy by yielding. In order to prove the effectiveness of the new system, an extensive experimental campaign has been conducted. This paper focuses on material and component tests, describing tension tests on traditional materials and UHS steel, creep tests on UHS steel and nut-bar assembly tests.
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Saatcioglu, Murat. "SEISMIC RETROFIT OF NONDUCTILE REINFORCED CONCRETE FRAME AND MASONRY BUILDINGS". NED University Journal of Research 2, Special Issue on First SACEE'19 (15 de junio de 2019): 143–64. http://dx.doi.org/10.35453/nedjr-stmech-2019-0009.
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A large proportion of existing building and bridge infrastructure across the world consists of seismically deficient non-ductile structural systems. Performance of structures during recent earthquakes have demonstrated seismic vulnerability of these systems, the majority of which were designed prior to the enactment of modern seismic codes, though some were designed more recently in areas where code enforcement provides challenges. These structures constitute considerable seismic risk, especially in large metropolitan centres. Because it is economically not feasible to replace a large segment of seismically deficient infrastructure with new and improved systems, retrofitting existing structures remains to be a viable seismic risk mitigation strategy. The objective of this paper is to highlight seismic retrofit strategies for deficient building and bridge infrastructures, with emphasis on experimental and analytical research conducted at the University of Ottawa. The retrofit strategies consist of structural upgrades at the system level, as well as at the element level. Non-ductile reinforced concrete frame retrofits, in the form of lateral bracing techniques, and concrete column and masonry wall retrofit methodologies are discussed. The use of innovative materials and techniques are presented.
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Roncari, Andrea, Filippo Gobbi y Cristiano Loss. "Nonlinear Static Seismic Response of a Building Equipped with Hybrid Cross-Laminated Timber Floor Diaphragms and Concentric X-Braced Steel Frames". Buildings 11, n.º 1 (24 de diciembre de 2020): 9. http://dx.doi.org/10.3390/buildings11010009.
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Simplified seismic design procedures mostly recommend the adoption of rigid floor diaphragms when forming a building’s lateral force-resisting structural system. While rigid behavior is compatible with many reinforced concrete or composite steel-concrete floor systems, the intrinsic stiffness properties of wood and ductile timber connections of timber floor slabs typically make reaching a such comparable in-plane response difficult. Codes or standards in North America widely cover wood-frame construction, with provisions given for both rigid and flexible floor diaphragms designs. Instead, research is ongoing for emerging cross-laminated-timber (CLT) and hybrid CLT-based technologies, with seismic design codification still currently limited. This paper deals with a steel-CLT-based hybrid structure built by assembling braced steel frames with CLT-steel composite floors. Preliminary investigation on the performance of a 3-story building under seismic loads is presented, with particular attention to the influence of in-plane timber diaphragms flexibility on the force distribution and lateral deformation at each story. The building complies with the Italian Building Code damage limit state and ultimate limit state design requirements by considering a moderate seismic hazard scenario. Nonlinear static analyses are performed adopting a finite-element model calibrated based on experimental data. The CLT-steel composite floor in-plane deformability shows mitigated effects on the load distribution into the bracing systems compared to the ideal rigid behavior. On the other hand, the lateral deformation always rises at least 17% and 21% on average, independently of the story and load distribution along the building’s height.
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Hyland, Clark W. K. y Sugeng Wijanto. "Lessons for steel structures from the 2009 earthquake damage in Padang". Bulletin of the New Zealand Society for Earthquake Engineering 43, n.º 2 (30 de junio de 2010): 134–39. http://dx.doi.org/10.5459/bnzsee.43.2.134-139.
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The Padang earthquake is a timely reminder to New Zealand structural engineers of a number of things with respect to seismic design and construction practice of steel structures. These include: The importance of implementing the latest seismic loadings and design technology into new and existing structures without undue delay; The need to maintain an effective Building Code enforcement and audit process, including the keeping of publicly transparent compliance records; The important role of the design engineer in observing and auditing the interpretation and implementation of the design is essential, to prevent improper substitution of materials and ill-considered design changes; The need for ongoing continuing professional development and education for design, construction and building code enforcement officials to develop and maintain technical competency; The separation of non-structural elements from interfering with the primary seismic resisting system needs to be carried through diligently from design and into construction. Where structural separation is not achieved then design models for integrating unreinforced brickwork panels within moment resisting frames need to be developed, particularly for retrofit situations; The design for weak-axis bending of two way moment resisting steel frames requires careful attention to secondary effects, and should be avoided where possible; Non-self centring structural elements need to be identified at design stage and designed to minimise inelastic behaviour during ultimate limit state earthquakes; Diagonal bracing rods should be designed to avoid failure within couplings. Consideration should also be given to the dynamic response of the roof level bracing system to heavy wall induced lateral loads; Connections at the interface of steel work with concrete and masonry sub-trades need to be carefully monitored to ensure intended design performance is achieved; Unreinforced masonry without lateral tiebacks should be avoided on lintels over egress-ways; A guide of typical structural repair methods would also be a useful tool for post-earthquake use, to quickly identify appropriate repair strategies and allow repair estimates to be developed. At a philosophical level, should a post-earthquake repair be required to simply allow a resumption of functionality? Alternatively should the repair be required to reinstate the structural performance to its pre-earthquake strength? Or should the repair improve the seismic resisting performance of the structure in line with current earthquake engineering knowledge?
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Bohara, Birendra Kumar, Kafeel Hussain Ganaie y Prasenjit Saha. "Seismic Analysis of Retrofitting of RC Regular Frame with V-Braced Frame". Journal of Engineering Technology and Planning 2, n.º 1 (19 de agosto de 2021): 55–63. http://dx.doi.org/10.3126/joetp.v2i1.39229.
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Retrofitting of the existing buildings helps to reduce the serious damages under the strong ground motions. In retrofitting techniques, steel bracings are used to resist the lateral load effectively. In this study, the author aimed to investigate the four-story RC frames without and with steel bracings to understand the seismic performances of the buildings. The authors select the V bracings having 7 different thickness of steel bracings ( t= 2.5, 4, 6, 8, 10, 14 and 20mm) and observed the effect in seismic behaviors of the structures in terms of maximum story displacements, inter-story drift (ISD), base shear, fundamental time period (FTP) and capacity curves. In addition, it observed the failure behaviors of the structures. To study the seismic behaviors, the response spectrum analysis and nonlinear static analysis are performed in ETABs software. The result indicates that V bracing improves the seismic performances of the RC frames as well as improves the strength capacity and stiffness of the buildings. Adding bracing in RC frames decreases the top story displacements and inter story drift of the buildings. To get the expected failure mechanism in the braced frames and suitable uniform energy dissipation behaviors, the bracings are designed in such a way that the RC columns should be the main line of defense in the dual systems. Expected failure mechanism is obtained when stronger column, weak beam and weaker bracings design philosophy is used and it is only possible when the columns are designed to resist at least 50% lateral base shear in dual systems. A suitable thickness of bracings which is economical and structurally good should be selected.
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Dominick, O. S. y J. W. Truman. "The physiology of wandering behaviour in Manduca sexta. III. Organization of wandering behaviour in the larval nervous system". Journal of Experimental Biology 121, n.º 1 (1 de marzo de 1986): 115–32. http://dx.doi.org/10.1242/jeb.121.1.115.
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The locomotor patterns typical of wandering behaviour were studied electromyographically in abdominal segments of freely moving larvae of Manduca sexta. Crawling locomotion consisted of stereotyped, anteriorly-directed, peristaltic waves of intersegmental muscle contraction. During burrowing the intersegmental muscles of all abdominal segments contracted simultaneously for several consecutive cycles and then performed a single bout of the crawling pattern. Sensory inputs determined which motor patterns were used and how they were modified. Local sensory inputs could modify patterns in the specific segments affected. The neural circuitry that was required to generate the peristaltic and bracing patterns was repeated among the thoracic and abdominal ganglia, and normally wa activated by the suboesophageal ganglion (SEG) and brain. In the absence of connections with the SEG and brain the segmental motor pattern generators could be activated by strong sensory stimuli. When the thoracic and abdominal segments lacked connections with the SEG, spontaneous movements were infrequent prior to wandering, but increased markedly at wandering or following 20-hydroxyecdysone (20-HE) infusion. Prior to wandering the SEG drives spontaneous locomotion in debrained larvae, but this function disappears in wandering larvae, or following 20-HE infusion. Prior to wandering the brain exerted a net inhibitory influence on locomotion. Removal of the medial region of the brain abolished this inhibition, resulting in strong, continuous locomotion which was driven by the lateral region of the brain. This lateral excitatory function of the brain was not altered by 20-HE infusion prior to wandering, nor did it change with the appearance of wandering behaviour. We conclude that the locomotor patterns used during wandering are produced by pattern generators in the segmental ganglia and are modified by sensory information. The circuitry responsible for activating these motor pattern generators is associated with the SEG, and is under the control of the brain. The brain exerts a net inhibitory influence prior to wandering, which becomes excitatory during wandering. Ecdysteroids appear to alter locomotor function by acting at various levels including the segmental ganglia, the SEG and the brain. A model is advanced describing this effect.
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Kam, Weng Yuen, Richard Built, Brandt Saxey y Jerod Johnson. "Buckling-Restrained Braces (BRB) Seismic Design - A Consulting Engineer’s Consideration". Key Engineering Materials 763 (febrero de 2018): 932–40. http://dx.doi.org/10.4028/www.scientific.net/kem.763.932.
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There is no standard for the design of Buckling-Restrained Braces (BRBs) frames in New Zealand. Consequently, a consulting engineer would need to consider a range of overseas design standards and latest research findings and incorporate into a New Zealand code-compliance framework. This “Alternative Solution” pathway to satisfy the New Zealand Building Code means peer review and agreement with peer review is required. This paper describes the design journey and technical challenges the authors had in the seismic design of the BRB for the New Zealand International Convention Centre (NZICC). BRB frames are used as the primary ductile lateral load bracing system, acting in parallel with the moment-resisting frames formed by the primary cruciform columns and storey-deep trusses. Due to the vertical irregularity and a dual-system structure, a direct displacement-based design (DDBD) approach was used in parallel with a more convention code-compliant force-based design, to derive the BRB design actions. The design of the BRB connections, in particular the gusset design is particularly challenging due to the diverging views and numerous methodologies available. We have considered several analytical methods for the BRB connection design and commissioned two full-scale testing of the critical BRB and the gusset connection. Lessons learnt
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SCHWARZ-WINGS, DANIELA. "The feeding apparatus of dyrosaurids (Crocodyliformes)". Geological Magazine 151, n.º 1 (19 de agosto de 2013): 144–66. http://dx.doi.org/10.1017/s0016756813000460.
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AbstractReconstructed soft-tissues of the craniocervical region of dyrosaurids are analysed under functional aspects to determine their prey-catching capabilities. Jaw adductors and jaw abductors are enlarged and possess longer muscle fibres that are increased by a long retroarticular process. This muscle enlargement resulted in a more forceful and quicker contraction, effective for movement of the long rostrum. The occipital joint and the cervical ribs, the long retroarticular process and the high cervical neural spines of dyrosaurids suggest a higher dorsoventral flexibility of the craniocervical region, whereas lateromedial flexibility was reduced. The epaxial muscles of the neck and scapular muscles were enlarged, and the supraspinal ligament most likely fanned out into a nuchal ligament. Suspension of the neck and skull of dyrosaurids was achieved by the scapular muscles, dorsal neck ligaments and epaxial muscles, whereas ventral bracing was reduced. From the reconstructed specializations of the feeding apparatus, an enhanced capability for movements in the vertical plane is postulated for dyrosaurids, together with reduced lateral movements of the craniocervical region. Besides laterally directed strokes for fish-catching, behaviours such as poking in the substrate, bottom feeding, multidirectional prey-catching strokes and improvement of diving skills were options for dyrosaurids and suggest a possible expansion of their diet. The longirostrine skull limited prey size, but the dentition allowed shelly prey items. The specialization of the food-capturing system in dyrosaurids and the resulting expansion of their food spectrum is one possible explanation for their evolutionary success, including their undisturbed transition of the Cretaceous–Palaeogene boundary.