Jeffrey A. Packer

Fatigue design procedure for welded hollow section joints

Part 1 Recommendations: Scope and general Fatigue design procedures Fatigue strength SCF Calculations for CHS Joints SCF Calculations for RHS Joints.

Criteria for the fatigue assessment of hollow structural section connections

Abstract A discussion of fatigue design criteria is presented for connections between hollow structural sections, based on knowledge gained from an extensive study on the fatigue behaviour of 90° T- and X-connections made of square hollow sections. After a general discussion of the various fatigue assessment methods available, the paper focuses on considerations behind the definition of the hot spot stress. On this basis, the current fatigue design guidelines are discussed. Based on knowledge gained from experiments and having identified the important fatigue design criteria, a hot spot definition is established, together with the outline of a proposal for future fatigue design guidelines of hollow section connections.

Simplified SCF formulae and graphs for CHS and RHS K- and KK-connections

Abstract In this paper, a set of simplified design formulae and graphs are presented to facilitate the determination of Stress Concentration Factors (SCFs), and hence the fatigue behaviour, of welded Circular Hollow Section (CHS) and Rectangular Hollow Section (RHS) uniplanar and multiplanar K-connections. This set of design formulae and graphs is based on a rational hot spot stress approach for hollow section connections, presented earlier in this journal [J. Construct. Steel. Res. 35 (1995) 71], and a very complex and comprehensive set of SCF formulae, also previously published in this journal [J. Construct. Steel. Res. 43 (1997) 87]. These formulae had been based on extensive Finite Element analyses and verified against independent test results. In addition to the design graphs, another new aspect of this paper is that — unlike earlier publications — a unified approach in terms of the Srh.s.−Nf line and thickness correction has been derived, for both RHS and CHS connections. The design graphs and Srh.s.−Nf line contained in this paper are destined to be an important component of the upcoming CIDECT Fatigue Design Guide and International Institute of Welding (IIW) Fatigue Design Recommendation for welded hollow section connections.

Yield line analysis of RHS connections with axial loads

The yield line method of analysis has been used successfully for estimating the strength of different Rectangular Hollow Section (RHS) connections due to yielding of the connecting face of the main member (through member such as chord or column). The influence of axial load in the main member is usually considered by a reduction factor. Two yield line models used for RHS connections and the methods previously used for the calculation of yield moment along an inclined yield line have been investigated. A new yield line model, which takes axial load in the main member into account, is developed to calculate the strength of RHS connections. Good agreement has been found between predictions from the formula developed from the new model and the results from both laboratory tests and Finite Element (FE) analyses, for plate-to-RHS connections.

Crack modeling in FE analysis of circular tubular joints

Abstract By mapping circles in two-dimensional planes to three-dimensional intersection curves between tubular members, a complicated three-dimensional mesh generating procedure for tubular joints is changed to a procedure similar to a two-dimensional case. More detailed modeling of welds and cracks can be included to analyze the fracture behavior of cracked tubular joints. Different types of crack tip models are discussed and a four-tip crack model is introduced to model crack propagation. These crack models can be applied to both through-thickness cracks and surface cracks. A procedure for transforming crack elements around a plane curve into crack elements for a doubly curved semi-elliptical surface crack around an intersection is also introduced. High-quality meshes can be obtained.

A finite element method based yield load determination procedure for hollow structural section connections

Abstract Analytical formulae based on yield line theory need to be validated by a rational determination of the yield load from experimental results. Such a comparison is then complicated by the inability to conclusively determine the yield load from load-deformation curves. Existing methods for determining the yield load from load-deformation curves are discretionary in nature. A FEM-based rigid, perfectly-plastic, yield load determination, as presented in this paper, represents a rational yield or ultimate limit state load for connections that do not otherwise exhibit a clearly defined yield or peak load. The efficacy of this newly postulated rigid, perfectly-plastic yield load determination is demonstrated by a comprehensive parametric FEM numerical study on stiffened branch plate-to-rectangular Hollow Structural Section (HSS) connections.

Cast Steel Yielding Brace System for Concentrically Braced Frames: Concept Development and Experimental Validations

AbstractThe Yielding Brace System is a highly ductile bracing system in which seismic energy is dissipated by the yielding fingers of a specially engineered cast steel connector. When the brace is severely loaded in tension and compression, the fingers yield in flexure, thus providing a full, symmetric hysteresis. Second-order geometric effects result in an increase in postyield stiffness at large displacements. The mechanics of the system are first presented, including several first principle equations used to predict a connector’s response. These equations are then used to design a prototype connector. The geometry of this prototype is evaluated using nonlinear finite element analysis. Following this analysis, the results of full-scale axial component testing of the prototype are discussed. These results include tensile coupon tests from material taken directly from unyielded portions of the test specimens. The prototype design and testing program presented demonstrate that the Yielding Brace System is ...

Analysis of Dynamic Response of Architectural Glazing Subject to Blast Loading

The effect of blast loading on civilian structures has received much attention over the past several years. The behavior of architectural glazing is of particular interest owing to the disproportionate amount of damage often associated with the failure of this component in a blast situation. This paper presents the development of a simple yet accurate finite element-based tool for the analysis of architectural glazing subjected to blast loading. This has been achieved through the creation of a user-friendly computer program employing the explicit finite-element method to solve for the displacements and stresses in a pane of glass. Both monolithic and laminated panes have been considered, in single and insulated unit configurations, and employing several types of glass. In all cases, the pane of glass has been modeled as a plate supported by an array of boundary conditions that include spring supports, and two failure criteria are employed. Furthermore, the program is designed to predict the hazard level, ...

Branch Plate-to-Circular Hollow Structural Section Connections. I: Experimental Investigation and Finite-Element Modeling

Abstract Although branch plate-to-circular hollow section (CHS) connections under branch axial load are simple to fabricate and cost-effective, they generally experience significant deformation at relatively low loads resulting in an imposed deformation limit. To increase the connection capacity, various stiffening methods such as use of ring stiffeners, grout filling, and “through plate” connections have been proposed. To determine the effectiveness of previously unstudied plate-to-CHS through plate connections, an experimental investigation consisting of 12 connections was undertaken. Additionally, the behavior of nonorthogonal or skewed connections and the effect of load sense were examined. The experimental study determined that through plate-to-CHS connection behavior can be obtained by algebraically combining the behavior of a T -type branch plate-to-CHS connection in tension with another in compression. Moreover, the through plate connection increased the capacity by more than three times that of a...

Moment connections between rectangular hollow sections

Abstract Research and development activity on manufactured tubes or ‘Hollow Structural Sections’ (HSS), has been remarkably well co-ordinated during the period from 1970 to 1992, but emphasis has been on axially loaded connections. Most of this research has been directed at connections under predominantly static loading but lately there has been increased attention given to fatigue loading. This co-ordination has been achieved principally by an international organization of HSS producers called CIDECT (International Committee for the Development and Study of Tubular Construction). This has resulted in a very favourable share of the structural steel market for this product. CIDECT and the International Institute of Welding (IIW) have collaborated closely over the last decade to produce several sets of HSS connection design recommendations, which have now achieved wide acceptance (for example, IIW Fatigue Design Recommendations (1985) and IIW Static Design Recommendations (1981, 1989)). The static design recommendations covered axially-loaded K, N, T, Y and X connections, and were based on a large number of laboratory tests and observed failure modes. Although work has evolved on moment-loaded connections it has not, until very recently, been summarized in a rational manner like axially-loaded HSS connections. This paper therefore aims to synthesize the design procedures for Rectangular Hollow Section (RHS) connections under moment loading, using for the design basis a set of failure modes which are consistent with those identified for axially-loaded connections. By proceeding in this manner, a unified design approach will be achieved for all RHS connections under ‘predominantly static loading’.