Yanglin Gong

OPTIMAL PERFORMANCE-BASED SEISMIC DESIGN USING MODAL PUSHOVER ANALYSIS

The paper presents a computer-automated performance-based design procedure for optimally proportioning a steel building framework to resist earthquakes. Modal pushover analysis is employed to evaluate structural demands imposed by design earthquakes representing a range of hazard levels (e.g. immediate-occupancy, life-safety and collapse-prevention). First-order Taylor series and sensitivity analysis are employed to formulate corresponding performance constraints explicitly in terms of member sizing variables and target lateral displacements. A generalised optimality criteria algorithm is employed to find the least-weight structure that experiences minimal damage (as characterised by ductility demand) while simultaneously satisfying all performance constraints at all hazard levels. The design methodology is illustrated for a nine-storey planar steel building framework.

Compressive tests of cold-formed steel curved panels

Abstract This paper discusses the compressive tests of cold-formed corrugated steel curved panels. In the absence of either a standard test protocol or a reported test on compressive tests of curved panels, this paper presents two types of compressive tests; namely, the corner and flange-section test, and full-section test, for curved specimens with primary focus on the experimental set-ups and test procedures. A total of 198 compressive tests, which consist of 114 corner and flange-section tests and 84 full-section tests, were conducted to investigate the influences of panel curvatures and transverse corrugations on buckling behaviour of cold-formed corrugated steel curved panels. The proposed test approaches yield consistent results; therefore, they could be considered reliable for compressive tests of curved specimens.

Plastic Behavior of Shear Tabs Welded to Flexible Wall Support

This paper presents an experimental study of six steel shear tab connections to hollow structural section columns. This study focuses on the plastic behavior of shear tabs and their supporting column walls. The column walls had width-to-thickness ratios ranging from 21 to 34. Large bending deformations were observed on both the column walls and the shear tabs. All six specimens failed owing to an excessive vertical deflection followed by a punching fracture of the tube wall around the perimeter of weld at the top of tab. The test results were found to agree well with two plastic mechanisms proposed for analysis. This study demonstrates that the shear strength of the tabs welded to a flexible wall support should be reduced when compared with that of the tabs welded to a rigid support. This paper also finds that the width-to-thickness ratio criterion for a rigid wall support is a function of the ratio of the length of tab to the width of the supporting wall and the relative bending strength between the tab ...

Optimal Stiffness Distribution of Steel Moment Frames under Extreme Earthquake Loading

The paper presents a design optimization method for steel moment frames under extreme earthquake loading. Seismic demands of the structures are evaluated using a nonlinear pushover analysis procedure. Least structural weight is taken explicitly as one design objective. The other objective, pursuing uniform ductility demands in all stories, is realized indirectly by imposing an equal limit to the plastic interstory drift ratio of each story. Explicit forms of the objective function and constraints in terms of member sizing variables are formulated to enable computer solution for the optimization model. The proposed design formulation seeks a least-weight design with an optimal lateral stiffness distribution for steel moment frames. The concepts are illustrated for a three-story moment frame example.

Inelastic Analysis Based Optimal Seismic Structural Design

This paper described an optimal inelastic-analysis-based seismic design methodology for steel building frameworks under earthquake ground motions. A nonlinear time history analysis procedure is adopted as the evolution tool for seismic demands. The analysis is categorized as an advanced analysis such that explicit member strength checking is not required in the design formulation. The design objectives are to minimize weight, earthquake input energy and to maximize hysteretic energy of fuse members. The design constraints include plastic rotation limit on frame members and inter-story drift limit on each story. A numerical example of moment-resisting frame is used to illustrate the methodology.

Design Optimization of Long-Span King-Post Trusses

With a unique arch and tie feature, king-post trusses can be built economically and efficiently and quickly for long-span roof structures. It has gained much popularity since its advent in early 1990s. The optimal design of the king-post truss system involves not only weight of the material but also factors such as fabrication, transportation and erection. This paper presents a design optimization method for long-span king-post roof truss systems. Through two example trusses built in North America, the main parameters affecting the cost of the truss system are studied thoroughly. Design guidelines, which aim to obtain a cost-effective design, are given for the determination of the depths of the overall truss and arched top truss. The result of the study is of great assistance to practicing engineers.

Optimal Design of Special Steel Moment Frames under Extreme Seismic Loading

Publisher Summary The chapter proposes a design methodology to achieve a uniform heightwise ductility demand for special steel moment frames under extreme earthquake hazards. A nonlinear pushover analysis is employed to evaluate seismic demands. A design example of a three-story rigid frame illustrates the concept of the methodology. The moment frames with a near uniform interstory drift distribution somewhat have a uniform plastification over the structural height. Specifically, the advantage of special moment frames is that columns can be designed strong enough such that the flexural yielding of beams will dominate at multiple levels of the frame, thereby achieving a higher capacity of energy dissipation. The design formulation searches for an optimal solution having a minimum structural weight with a uniform ductility demand while, at the same time, meeting displacement, strength, and strong-column weak-beam constraints.