Seismic performance of low- and medium-rise chevron braced steel frames

2001 ◽  
Vol 28 (4) ◽  
pp. 699-714 ◽  
Author(s):  
Robert Tremblay ◽  
Nathalie Robert
Keyword(s):  
Dynamic Instability ◽  
Steel Structures ◽  
Seismic Loads ◽  
Building Structures ◽  
Braced Frames ◽  
Capacity Design ◽  
Seismic Behaviour ◽  
R Factor ◽  
Tension Capacity ◽  
Strong Ground

This paper describes the seismic behaviour of chevron steel braced frames for 2-, 4-, 8-, and 12-storey steel building structures. Two different design approaches were considered: one that corresponds to current CSA-S16.1 seismic provisions for braced frames with nominal ductility with an R factor of 2.0, and one in which the beams are sized to develop a fraction of the yield tension capacity of the bracing members. In this second approach, an R factor of 3.0 was used for determining the seismic loads and chevron bracing with stronger beams capable of developing 100%, 80%, and 60% of the brace yield load were examined. The results show that current S16.1 provisions for chevron braced frames may lead to systems that are prone to dynamic instability for 4-storey and taller structures. Chevron bracing with stronger beams exhibits a more stable inelastic response and can be used for structures up to 8 storeys in height. For 2- and 4-storey buildings, chevron braced frames with beams designed to develop only 60% of the brace yield resistance can be used. The analyses also show that the force demand in brace connections, beams, and columns as determined from capacity design provisions agree well with that anticipated under strong ground motions.Key words: earthquakes, seismic design, steel, structures, braced frames, bracing members, beams, columns, connections.

Seismic design of low- and medium-rise chevron braced steel frames

2000 ◽  
Vol 27 (6) ◽  
pp. 1192-1206 ◽  
Author(s):  
Robert Tremblay ◽  
Nathalie Robert
Keyword(s):  
Seismic Design ◽  
Design Method ◽  
Ground Motions ◽  
Steel Structures ◽  
Shear Resistance ◽  
Seismic Loads ◽  
Braced Frames ◽  
Design Procedures ◽  
Reinforced Beams ◽  
Strong Ground

This paper presents two different seismic design approaches for multistorey chevron (inverted V) steel braced frames. The first method complies with current Canadian code provisions in which the beams in the bracing bents must be designed to sustain the forces expected to develop up to buckling of the bracing members. In the second approach, the beams must also resist the gravity loads together with a fraction of the brace loads that are induced after buckling of the braces. This second approach aims at minimizing the degradation in storey shear resistance typically exhibited by chevron bracing subjected to strong ground motions, and it is proposed that such braced frames with reinforced beams be designed for reduced seismic loads. Both design procedures are applied to typical multistorey braced frames to examine their economical impacts. Three different beam strength levels were considered for the second design method. The results show that the saving expected from reducing the seismic loads in the second design approach is generally offset by the increase in beam sizes required by this method. However, the braced frames with stronger beams exhibit a much higher storey shear resistance after buckling of the bracing members has occurred.Key words: earthquakes, seismic, design, steel, structures, braced frames, bracing members, beams, columns, connections.

scholarly journals A Capacity Design Procedure for Columns of Steel Structures with Diagonals Braces

2014 ◽  
Vol 8 (1) ◽  
pp. 196-207 ◽  
Author(s):  
M. Bosco ◽  
A. Ghersi ◽  
E.M. Marino ◽  
P.P. Rossi
Keyword(s):  
Design Procedure ◽  
Steel Structures ◽  
Building Structures ◽  
Axial Deformation ◽  
Braced Frames ◽  
Capacity Design ◽  
Concentrically Braced Frames ◽  
Design Spectrum ◽  
Internal Forces ◽  
Seismic Forces

According to modern seismic codes, in concentrically braced frames the seismic input energy should be dissipated by means of the hysteretic behaviour of braces while all the other members (i.e. beams and columns) have to remain elastic. Accordingly, the design internal forces of braces are determined in these codes by elastic analysis of the structure subjected to seismic forces obtained by the design spectrum. The internal forces of the non-dissipative members, instead, are calculated by means of specified rules for the application of capacity design principles. According to some recent numerical analyses, the yielding or buckling of columns may take place before braces achieve their axial deformation capacity. This paper investigates the reasons of this unsatisfactory behaviour and proposes technological suggestions and a design procedure to improve the seismic performance of columns of building structures with diagonal braces.

Accounting for overstrength in seismic design of steel structures

1998 ◽  
Vol 25 (1) ◽  
pp. 1-15 ◽  
Author(s):  
M A Rahgozar ◽  
J L Humar
Keyword(s):  
Seismic Design ◽  
Slenderness Ratio ◽  
Steel Structures ◽  
Building Structures ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Design Loads ◽  
Reserve Strength

Observations during many earthquakes have shown that building structures are able to sustain without damage earthquake forces considerably larger than those they were designed for. This is explained by the presence in such structures of significant reserve strength not accounted for in design. Relying on such overstrength, many seismic codes permit a reduction in design loads. The possible sources of reserve strength are outlined in this paper, and it is reasoned that a more rational basis for design would be to account for such sources in assessing the capacity rather than in reducing the design loads. As an exception, one possible source of reserve strength, the redistribution of internal forces, may be used in scaling down the design forces. This is because such scaling allows the determination of design forces through an elastic analysis rather than through a limit analysis. To assess the extent of reserve strength attributable to redistribution, steel building structures having moment-resisting frames or concentrically braced frames and from 2 to 30 storeys in height are analyzed for their response to lateral loading. A static nonlinear push-over analysis is used in which the gravity loads are held constant while the earthquake forces are gradually increased until a mechanism forms or the specified limit on interstorey drift is exceeded. It is noted that in moment-resisting frames the reserve strength reduces with an increase in the number of storeys as well as in the level of design earthquake forces. The P→Δ effect causes a further reduction. In structures having braced frames the main parameter controlling the reserve strength is the slenderness ratio of the bracing members. In these structures, reserve strength is almost independent of both the height of the structure and the effect of building sway. Key words: seismic design, overstrength factor, reserve strength owing to redistribution, steel moment-resisting frames, steel-braced frames, push-over analysis.

scholarly journals Modal properties and seismic behaviour of buildings equipped with external dissipative pinned rocking braced frames

2018 ◽  
Vol 172 ◽  
pp. 807-819 ◽  
Author(s):  
L. Gioiella ◽  
E. Tubaldi ◽  
F. Gara ◽  
L. Dezi ◽  
A. Dall'Asta
Keyword(s):  
Braced Frames ◽  
Seismic Behaviour ◽  
Modal Properties

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.

Assessing the Pilot Implementation of Flipped Classroom Methodology in the Concrete and Steel Structures Subject of Architecture Undergraduate Studies

2019 ◽  
pp. 55-76 ◽  
Author(s):  
Carles Campanyà ◽  
David Fonseca ◽  
Nuria Martí ◽  
Daniel Amo ◽  
David Simón
Keyword(s):  
Flipped Classroom ◽  
Steel Structures ◽  
Logical Reasoning ◽  
Building Structures ◽  
Deep Knowledge ◽  
Undergraduate Studies ◽  
Core Subject ◽  
The Subject ◽  
Pilot Implementation

This work is focused in implementing and assessing a flipped classroom model in the concrete and steel structures subject, a core subject within architecture undergraduate studies. Even though current legislation in Spain settle architects as the last responsible of building structures, most architects delegate these processes in professional studios specialized in structures. Being the most common way of proceeding in architectural studios, it is not uncommon among architects to think that a deep knowledge in structures is not necessary, especially regarding calculations development. In this framework, concrete and steel structures is a subject with high logical reasoning component using mathematics, and this knowledge is considered by most of the students as difficult to acquire. With the aim of increasing students' motivation in the subject contents and improving students' acquisition of competences a new teaching proposal using flipped classroom method has been designed, implemented, and analyzed.

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