SEISMIC COLUMN SPLICE DEMANDS IN BRACED FRAMES WITH BUCKLING CONTROLLED BRACES

Numerous experimental tests showed that ductile square hollow structural sections (HSS) are susceptible to premature fracture under design-level earthquake ground motions. In addition, recent research has highlighted the vulnerability of column splices to reach their full strength once ductile square HSS braces experience a fracture in braced frames. In this study, the performance of column splices in 5-and 13-story special concentrically braced frames (SCBFs), with X-bracing configuration, located at a distance permitted by the seismic design provisions (i.e., four feet over the concrete floor level), is evaluated under a large number of ground motion excitations. The performance of identical SCBFs with conventional HSS braces and innovative buckling controlled HSS braces is compared. Overall, results from this research indicate that the prevention of brace buckling in SCBFs yields a substantial reduction in the seismically induced bending demands on the column splices, leading to a large margin of safety to remain elastic.

Concrete-Filled Hollow Structural Sections. II: Flexural Members, Beam-Columns, Tension, and Shear

This article reviews contemporary North American and international approaches to the design of concrete-filled hollow structural section (HSS) members for flexure, axial compression plus uniaxial bending, tension, and shear. Results from tests on concrete-filled HSS members under flexure and combined loading are compared to predicted strengths using current (CSA S16:19 and AISC 360-16) and recommended CSA S16 design equations (with limits of validity). A first-order reliability analysis of design provisions for flexure is performed in accordance with CSA S408-11, and recommendations are made for potential revision of CSA S16. Design examples are provided, and results are compared to the counterpart American code (AISC 360-16). This paper is Part II of a two-part series. Part I covers materials, cross-section classification, and concentrically loaded columns.

Concrete-Filled Hollow Structural Sections. I: Materials, Cross-Section Classification, and Concentrically Loaded Columns

This paper reviews contemporary rules in CSA S16:19, AISC 360-16 and EN 1994-1-1 for concrete-filled hollow structural sections (HSS), covering materials, cross-section classification, and concentrically loaded columns. Results from 453 tests on axially compressed concrete-filled HSS members are compared to predicted strengths using current (CSA S16:19, AISC 360-16 and EN 1994-1-1) and recommended CSA S16 design equations (with limits of validity), and a first-order reliability analysis is performed in accordance with CSA S408-11. The recommendations herein are shown to maintain the current CSA S16:19 Clause 18.2 level of reliability for concrete-filled HSS compression members. Design examples are provided, and results are compared to the counterpart American code (AISC 360-16). This paper is Part I of a two-part series. Part II covers flexural members, beam-columns, tension and shear.

The Effect of Weld Length on the Tension Capacity of Hollow Structural Section (HSS)

The non-uniform stress distribution occurs in a tension member adjacent to a connection, in which all elements of the cross-section are not directly connected. This effect reduces the member’s design strength because the entire cross-section is not fully effective in the critical section’s location. That's why an experimental study has been done to investigate the effect of the weld length on the tension capacity, two specimens (hollow structural sections) have been tested by using Instron 8800 machine with two weld lengths, 46 mm and 56 mm. The 46 mm size is the minimum requirement of the sufficient size of the tension connection depending on United States Steel Standard. The Result proved that there has been too much effect on the connection carrying tension capacity. The result of the 46 mm weld length is about 155 KN and about 180 KN for the 56 mm weld length. While the ABAQUS simulation results were about 168 KN for the 46 mm weld length and about 172 KN for the 56 mm weld length.

SEISMIC EVALUATION OF SQUARE HSS BRACES IN SCBF USING REGRESSION ANALYSIS

Since the 1990s, structural engineering practice geared toward the use of hollow structural sections (HSS), notably square HSS, for their economy, and ease of design and construction. According to the AISC Seismic Provisions, during a severe earthquake, these braces could undergo post-buckling axial deformations 10 to 20 times their yielding deformation. However, recent experimental studies indicate that braces made of square HSS, depending on their size, width-to-thickness, and slenderness ratio, are vulnerable to fracture even prior to 10. Therefore, relying on past experimental studies comprised of a few square HSS specimens to develop seismic requirements for SCBF with square HSS could lead to underestimation of the seismic risk. This paper aims to evaluate the fracture risk of braces in existing SCBFs designed in accordance with AISC 341-05 and AISC 341-16 through incremental dynamic analyses (IDA) along with experimentally developed regression model that estimates fracture.

The Resistance of Welded Joints of Galvanized RHS Trusses with Different Vent Hole Geometries

A worldwide-accepted technique to protect steel lattice girders with welded hollow sections against corrosion is the hot-dip galvanizing process. In this process, vent holes are required in braces to fill the inner part protecting them from corrosion, to allow the immersion of the structure in the zinc bath and to recover the excess fluid after the bath. The cross-section reduction due to the vent hole could lead to a decrease in the effective brace resistance; this is not easily quantified, because there are neither prescriptions nor recommendations in the design codes to assess this effect. Therefore, the hollow structural sections could be underutilized due to doubts regarding the safety of this type of joint. This research was conducted in order to categorize different geometries and positions of vent holes in order to determine the best in terms of joint efficiency. A validated finite element model considering welds on lattice girders joints was extended to take into account different vent hole shapes. This research concludes that the presence of ventilation holes such as the ones considered in this study does not significantly affect the joint resistance, and that all the analyzed hole shapes could be proposed as a valid solution for machining vent holes. The conclusions drawn up from this work could be useful for structural steel designers, providing them with valuable design recommendations.

Study of cold formed steel beam column joint to resist lateral load

Cold Formed Steel (CFS) is one of the materials that recently used in building structures. There are many advantages of CFS compared with other materials, such as lightweight, high tensile strength, and fast construction. Hollow Structural Sections (HSS) is the most commonly used as beam and column CFS sections. The purposes of this study are determining the behavior and capacity of CFS beam column joint under lateral load with manual calculation, numerical analysis and experimental. The test specimens used 1 mm thick, 4x4cm HSS for column and 2x4cm HSS for beam. Beam and column connected by two single angle plates placed above and below the beam sides. Both parallel and staggered fastener configurations used in this experiment. Four 4 mm diameter bolts used in this connection. Monotonic static loading applied on beam for modelling the lateral load. The experimental results show the behavior and the capacity of the beam column joint with parallel fastener configurations. The numerical results show that the staggered fastener configuration has better performance compared with the parallel fastener configuration. The CFS beam column joint are adequate to resist the lateral load and feasible to be apply as structural components in building structures.