Cyclic Load Behavior of Angle X‐Bracing

2009

Bull Earthquake Eng

113

This paper assesses the fundamental approaches and main procedures adopted in the seismic design of steel frames, with emphasis on the provisions of Eurocode 8. The study covers moment-resisting as well as concentrically-braced frame configurations. Code requirements in terms of design concepts, behaviour factors, ductility considerations and capacity design verifications, are examined. The rationality and clarity of the design principles employed in Eurocode 8, especially those related to the explicit definitions of dissipative and non dissipative zones and associated capacity design criteria, are highlighted. Various requirements that differ notably from the provisions of other seismic codes are also pointed out. More importantly, several issues that can lead to unintentional departure from performance objectives or to impractical solutions, as a consequence of inherent assumptions or possible misinterpretations, are identified and a number of clarifications and modifications suggested. In particular, it is shown that the implications of stability and drift requirements as well as some capacity design checks in moment frames, together with the treatment of post-buckling response and the distribution of inelastic demand in braced frames, are areas that merit careful consideration within the design process.

Section: Member Responsementioning

confidence: 81%

Assessment of European seismic design procedures for steel framed structures

2009

Bull Earthquake Eng

113

“…When combined with the measured material strength, this leads to the normalised slenderness ratio shown in Table 1. The normalised slenderness is defined by Eurocode 3 [14] as λ = N pl /N cr (1) in which N pl and N cr are the plastic section capacity and the elastic (Euler) buckling load, respectively. The transverse beams supported three longitudinal beams (B1-B3 in Fig.…”

Section: Experimental Model and Test Set-upmentioning

confidence: 99%

“…The complex asymmetric response displayed under these conditions has prompted several investigations of the cyclic behaviour of bracing members (e.g. [1][2][3][4][5][6][7][8][9]). Most of these have been based on quasi-static cyclic tests conducted under predefined displacement histories for specific ranges of member slenderness, with comparatively fewer studies performed under realistic dynamic loading conditions.…”

Section: Introductionmentioning

confidence: 99%

Earthquake testing and response analysis of concentrically-braced sub-frames

Broderick

Journal of Constructional Steel Research

Goggins

2008

The results of shake table tests on three concentrically-braced sub-frames are compared with a series of correlative inelastic analyses. Both transient time-history and nonlinear static (pushover) analyses are considered. The lateral resistance of the test frames is provided by a pair of coldformed tubular steel members. The brace cross-section is varied between tests to investigate the influence of brace slenderness on the stiffness, resistance and ductility displayed by the frame under strong earthquake loading. Response simulations using a two-dimensional analytical model of the test frame are compared with the experimental results. Brace strengths and elastic test frame properties established in complementary static tensile tests and low-level shake table tests, respectively, are used to determine model input data. The transient acceleration and displacement response of the frames calculated in nonlinear time-history analyses are compared with corresponding experimental measurements. The base shear-frame drift relationship is calculated using pushover analyses that consider either the resistance of both frame braces or the tension brace alone. These are compared with the experimental hysteretic response of the test frame. On the whole, the analytical results are observed to agree well with the experimental results, especially with respect to brace tension forces and frame base shear. Cases where the experimental and analytical responses deviate are identified and the implications for earthquake response assessment and design are discussed.

“…This behaviour has been investigated experimentally and analytically by a number of researchers. [6][7][8][9][10] The hysteretic axial load (N) response of a bracing member against axial deformation (ä) is schematically shown in Fig. 2.…”

Section: Cyclic Responsementioning

confidence: 99%

Seismic design procedures for concentrically braced frames

Proceedings of the Institution of Civil Engineers - Structures

2003

This paper deals with the main behavioural issues involved in the seismic design of typical forms of concentrically braced frames. The response of bracing members under monotonic and cyclic axial loading is first considered, and the key parameters affecting the performance are highlighted. This is followed by an assessment of the different design approaches employed for the treatment of brace buckling, and the influence of the underlying assumptions on various aspects of frame response. The provisions of international codes of practice are examined within the discussions, with emphasis on the recommendations of Eurocode 8. Selected results from static and dynamic non-linear analysis on idealised frame configurations are presented in order to illustrate salient response criteria, particularly those related to ductility demand and inelastic distribution. The primary sources of inconsistency existing in code provisions are demonstrated, and their implications on the seismic performance of concentrically braced frames are addressed. It is shown that several code modifications are required in order to alleviate causes of undesirable performance and to facilitate a rational implementation of capacity design concepts.