scholarly journals Comparative Evaluation of Concentric Bracing Systems for Lateral Loads on Medium Rise Steel Building Structures

2020 ◽  
pp. 124-130
Author(s):  
Sisaynew Tesfaw Admassu
Keyword(s):  
Lateral Displacement ◽  
Level Structure ◽  
Lateral Load ◽  
Frame Structure ◽  
Lateral Stiffness ◽  
Building Structures ◽  
Steel Buildings ◽  
Lateral Strength ◽  
Strength And Stiffness ◽  
Bracing System

To resistance, the lateral load from wind or an earthquake is that the reason for the evolution of varied structural systems. Because, when a medium or any multi-level structure is exposed to horizontal or torsional deflections under the action of seismic burdens. Lateral stiffness is a major consideration in the design of the buildings. In addition to this, many existing steel buildings and reinforced concrete buildings for which the weak lateral stiffness is the main problem; should be retrofitted to conquer the insufficiencies to resist the lateral loading. Lateral load resisting systems are structural elements providing basic lateral strength and stiffness, without which the structure would be laterally unstable. The unstable nature of the structure is solved by the fitting arrangement of bracings systems. A bracing system is that forms an integral part of the frame. Thus, such a structure has to be analyzed before arriving at the best type or effective arrangement of bracing. Bracing is a highly effective strategy of resisting lateral forces in a frame structure. In this document, a ten-story building with incorporated bracing systems is analysed using ETABS 2016 analysis software as per Eurocode and Ethiopian Building Code Standards (EBCS). Then, the lateral displacement is evaluated under each of the bracing types.

scholarly journals Seismic Performance of Bracing, Diagrid and Outrigger System

2020 ◽  
Vol 9 (7) ◽  
pp. 32-36
Keyword(s):  
Seismic Performance ◽  
Tall Buildings ◽  
Lateral Load ◽  
Lateral Loads ◽  
Steel Buildings ◽  
Efficient System ◽  
Effective System ◽  
Tension And Compression ◽  
Lateral Bracing ◽  
Bracing System

In this paper bracing, diagrid and outrigger system have been analyzed for comparing the seismic performance of multistorey buildings. Bracing system is a very efficient system which can be used as a lateral load resisting system in concrete and steel buildings, in this system lateral loads are transferred through lateral bracing by undergoing in tension and compression .diagrid is another effective and efficient system that can be used as lateral load resisting system in steel and concrete tall buildings, in this system lateral loads are transferred by inclined members of the building. Another very effective system which commonly used for resisting lateral loads in concrete and steel high rise building is outrigger system, in this system lateral loads will be resisted by outrigger belt truss and core shear wall. Location and number of outrigger and type of bracing is very important which needs to be optimized in this system. In this paper comparison of bracing, diagrid and outrigger system have been studied on a 24 storey by using a standard package of ETABS 2017.

scholarly journals An Experimental Study on Hybrid Noncompression CF Bracing and GF Sheet Wrapping Reinforcement Method to Restore Damaged RC Structures

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Kang Seok Lee
Keyword(s):  
Seismic Retrofitting ◽  
Strengthening Effect ◽  
Reinforcement Scheme ◽  
Rc Structures ◽  
Rc Frames ◽  
Study Results ◽  
Lateral Strength ◽  
Strength And Stiffness ◽  
Cyclic Loading Tests ◽  
Bracing System

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.

Contribution of Beam-Column Connections with Bolted Angles in the Reserve Capacity and Full-Scale Cyclic Testing

2018 ◽  
Vol 763 ◽  
pp. 475-484 ◽  
Author(s):  
Thierry Béland ◽  
Robert Tremblay ◽  
Joshua Sizemore ◽  
Larry A. Fahnestock ◽  
Cameron Bradley ◽  
...  
Keyword(s):  
Failure Modes ◽  
Full Scale ◽  
Building Structures ◽  
Test Program ◽  
Moment Frame ◽  
Gravity Load ◽  
Seismic Force ◽  
Lateral Strength ◽  
Strength And Stiffness ◽  
Partially Restrained

Partially restrained beam-column connections can be used in the gravity load system of building structures to develop moment frame action to enhance collapse prevention for low-ductility steel lateral systems. The benefit from such reserve lateral strength and stiffness is illustrated for a low-rise building with steel braced frames designed in accordance with Canadian provisions for seismic force resisting systems of the Conventional Construction category. Preliminary results from a comprehensive cyclic test program recently completed on beam-to-column joints with bolted double web angle acting with top and seat angles are presented. The test program included 23 full-scale beam-to-column sub-assemblages subjected to combined gravity shear forces and cyclic rotational demands. Experimental observations on the deformation patterns and failure modes are presented together with representative hysteretic moment-rotation responses of bolted double web angles without and with top and seat angles.

scholarly journals Mechanical Performance of Mega Steel Frame-Prestressed Composite Bracing Structure

2014 ◽  
Vol 8 (1) ◽  
pp. 23-41 ◽  
Author(s):  
Tang Baijian ◽  
Shao Jianhua ◽  
Pei Xingzhu ◽  
Gu Sheng
Keyword(s):  
Failure Mode ◽  
Lateral Displacement ◽  
Internal Force ◽  
Steel Frame ◽  
Lateral Stiffness ◽  
Horizontal Load ◽  
Vertical Load ◽  
Main Structure ◽  
Bracing System ◽  
Force Equilibrium

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.

scholarly journals A Study on the Effectiveness of Bracing Systems in Soft Storey Steel Buildings

1970 ◽  
Vol 4 (2) ◽  
pp. 97-108
Author(s):  
Shalaka Dhokane ◽  
K. K. Pathak
Keyword(s):  
Seismic Design ◽  
Bending Moment ◽  
Lateral Stiffness ◽  
Steel Buildings ◽  
Soft Storey ◽  
Soft Story ◽  
High Rise ◽  
Maximum Shear Force ◽  
Steel Building ◽  
Bracing System

A soft storey or a weak storey is one in which the lateral stiffness is less than 70 percent of that in the storey above or it can be less than 80 percent of the average lateral stiffness of the three stories above. For the reduction of lateral deflection of a structure, a bracing system is provided. In seismic design of structure and in high rise structure, the provision of bracing system has become more effective. So this paper aims to find out the effect of bracing on soft storey of steel building. In this paper, G+9 steel frames are modeled with different type of bracing pattern and different combination of soft story using software STAAD Pro. Effect of these different bracings on soft storey is studied for different parameter like column displacement, maximum deflection, storey drift, maximum bending moment, maximum axial force and maximum shear force. From the observed result best type of bracing will be selected.

A Novel Technique of Seismic Strengthening of Nonductile RC Frame using Steel Caging and Aluminum Shear Yielding Damper

2009 ◽  
Vol 25 (2) ◽  
pp. 415-437 ◽  
Author(s):  
Dipti R. Sahoo ◽  
Durgesh C. Rai
Keyword(s):  
Energy Dissipation ◽  
Lateral Load ◽  
Rc Frame ◽  
Test Protocol ◽  
Shear Yielding ◽  
Reduction In Force ◽  
Rc Frames ◽  
Lateral Strength ◽  
Lateral Displacements ◽  
Strength And Stiffness

A novel strengthening scheme for seismically-weak RC frames is proposed which utilizes external steel caging to improve flexural/shear strength of columns and aluminum shear-yielding damper ( Al-SYD) to further enhance lateral strength, stiffness and overall energy dissipation capacity of the frame. This paper describes the effectiveness of this scheme as evidenced in an experimental study on a reduced scale (1:2.5) single-story, single-bay, gravity-only designed reinforced concrete (RC) frame. The strengthened frame was simultaneously subjected to gravity loads and reversed cyclic lateral displacements as per ACI-374 loading protocol. An innovative connection scheme was designed to transfer a portion of frame lateral load to the energy dissipation device ( Al-SYD). Besides the significant increase in lateral strength and stiffness of the strengthened frame, RC frame members did not suffer any major damage during the entire test protocol. This indicates significant reduction in force demand on existing RC members because of enhanced energy dissipation through hysteretic shear yielding of aluminum panels. Moreover, the simple connection scheme proposed in this study proved very efficient in transferring the frame lateral load to strengthening elements.

Study on Rational Ratios of Lateral Stiffness for Masonry Building with Frame Structure at First Two Stories

2012 ◽  
Vol 174-177 ◽  
pp. 2012-2015
Author(s):  
Xiao Long Zhou ◽  
Ying Min Li ◽  
Lin Bo Song ◽  
Qian Tan
Keyword(s):  
Seismic Performance ◽  
Time History ◽  
Shear Wall ◽  
Calculation Model ◽  
Frame Structure ◽  
Wall Structure ◽  
Masonry Building ◽  
Lateral Stiffness ◽  
Stiffness Ratio ◽  
Lateral Stiffness Ratio

There are two typical seismic damage characteristics to the masonry building with frame shear wall structure at first two stories, and the lateral stiffness ratio of the third storey to the second storey is one of the key factors mostly affecting the seismic performance of this kind of building. However, some factors are not considered sufficiently in current Chinese seismic codes. According to the theory of performance-based seismic design, the seismic performance of this kind of structure is analyzed in this paper by taking time-history analysis on models which with different storey stiffness ratios. The results show that when the lateral stiffness ratio controlled in a reasonable range, the upper masonry deformation can be ensured in a range of elastic roughly, and the bottom frame can be guaranteed to have sufficient deformation and energy dissipation capacity. Finally, according to the seismic performance characteristics of masonry building with frame shear wall structure at first two stories, especially the characteristics under strong earthquakes, a method of simplified calculation model for the upper masonry is discussed in this paper.

Column Moment Demands from Orthogonal Beam Twisting

2018 ◽  
Vol 763 ◽  
pp. 259-269
Author(s):  
George Webb ◽  
Kanyakon Kosinanonth ◽  
Tushar Chaudhari ◽  
Saeid Alizadeh ◽  
Gregory A. MacRae
Keyword(s):  
Lateral Displacement ◽  
Frame Structure ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Element Analysis ◽  
Soft Storey ◽  
Simply Supported ◽  
Composite Frame ◽  
Explicit Consideration ◽  
Column Joint

Beam column joint subassemblies in steel moment frames often have simply-supported gravity beams framing into the joint in the perpendicular direction. When these subassemblies undergo lateral displacement, moments enter the column from the beams. Some of these moments are directly applied from the in-plane beam and slab stresses as they contact the column, and additional moments occur as the slab causes the perpendicular simply supported beams to twist. In most design codes around the world, no explicit consideration of these moments is performed even though they may increase the likelihood of column yielding and a soft-storey mechanism. This paper quantifies the magnitude of these perpendicular beam twisting moments in typical subassemblies using inelastic finite element analysis. It is shown that for beam-column-joint-slab subassemblies where the primary and secondary beams are fully welded to the column, the addition of slab effects significantly increases the total stiffness and strength of the composite frame structure. In addition to this, it is also shown the twisting moment demand of the secondary beams increased the frames strength by approximately 2% for an imposed drift of 5% for the subassembly investigated when no gap was provided between slab and the column. It was also shown the twisting moment demand of the secondary beams increased the frames strength by approximately 10% for a maximum imposed drift of 5% for the subassembly investigated when a gap was provided between the slab and the column.

Seismic Performance Assessment of Existing Steel Buildings: A Case Study

2018 ◽  
Vol 763 ◽  
pp. 1067-1076 ◽  
Author(s):  
Luigi di Sarno ◽  
Fabrizio Paolacci ◽  
Anastasios G. Sextos
Keyword(s):  
Numerical Study ◽  
Central Italy ◽  
Steel Structures ◽  
Eurocode 8 ◽  
Building Structures ◽  
Steel Buildings ◽  
Seismic Performance Assessment ◽  
Masonry Infills ◽  
Main Shocks

Numerous existing steel framed buildings located in earthquake prone regions world-wide were designed without seismic provisions. Slender beam-columns, as well as non-ductile beam-to-column connections have been employed for multi-storey moment-resisting frames (MRFs) built before the 80’s. Thus, widespread damage due to brittle failure has been commonly observed in the past earthquakes for steel MRFs. A recent post-earthquake survey carried out in the aftermath of the 2016-2017 Central Italy seismic swarm has pointed out that steel structures may survive the shaking caused by several main-shocks and strong aftershocks without collapsing. Inevitably, significant lateral deformations are experienced, and, in turn, non-structural components are severely damaged thus inhibiting the use of the steel building structures. The present papers illustrates the outcomes of a recent preliminary numerical study carried out for the case of a steel MRF building located in Amatrice, Central Italy, which experienced a series of ground motion excitations suffering significant damage to the masonry infills without collapsing. A refined numerical model of the sample structure has been developed on the basis of the data collected on site. Given the lack of design drawings, the structure has been re-designed in compliance with the Italian regulations imposed at the time of construction employing the allowable stress method. The earthquake performance of the case study MRF has been then investigated through advanced nonlinear dynamic analyses and its structural performance has been evaluated according to Eurocode 8-Part 3 for existing buildings. The reliability of the codified approaches has been evaluated and possible improvements emphasized.

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