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Ball S.C.,John A. Martin and Associates Inc.
Structural Design of Tall and Special Buildings | Year: 2011

The architectural expressions for many modern buildings require creative and unconventional structural solutions. Columns must be taller, beams must span further, the structure must be more slender, elements must be curved, structural framing must be sloped and connections must deviate from conventional orthogonal fit-up. Although the technology exists to analyze and design responsive structural systems, prescriptive code requirements oftentimes hinder the implementation of those technologies. Although not a 'tall building' by traditional definition, the Tom Bradley International Terminal (TBIT) Modernization Program at Los Angeles International Airport (LAX) provides an appropriate case study in the implementation of unconventional structural geometry subject to code requirements that prescribe contrasting conventional geometry, which is a familiar challenge for many tall buildings. The architectural expression for the LAX TBIT Modernization Program required the use of long-span steel Special Moment Frames with non-orthogonal moment connections between the beams and columns. The beams were sloped, some were sloped and curved and some of the columns were sloped. The reduced beam section (RBS) moment connection was selected for the project. ANSI/AISC 358, Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications, provides prequalification limits for using an RBS connection. Those limits do not address non-orthogonal moment connections. ANSI/AISC 358 implicitly limits connections to orthogonal geometry; hence, non-orthogonal moment connections are not prequalified for use in seismic applications. This paper describes the structure and the cyclic testing program that was implemented to qualify the proposed non-orthogonal RBS connections in accordance with ANSI/AISC 341, Seismic Provisions for Structural Steel Buildings, Appendix S for use on the LAX TBIT Modernization Project. © 2011 John Wiley & Sons, Ltd. Source


Kim D.-W.,University of California at San Diego | Ball S.C.,John A. Martin and Associates Inc. | Sim H.-B.,Incheon National University | Uang C.-M.,University of California at San Diego
Journal of Structural Engineering (United States) | Year: 2016

AISC 358 provides steel connections that are prequalified for use in special and intermediate moment frames (SMF and IMF). Implicit in this standard is that the beam and column are orthogonal to each other in the elevation of the frame. To evaluate the effects of a sloped connection considering an angle of deviation from orthogonal of 28°, two reduced beam section (RBS) moment connections with W36 x 231 beam and W36 x 302 column were cyclically tested. Although both specimens met the acceptance criteria of AISC 341, brittle fracture of top flange weld soon followed, a failure mode not typical of an RBS connection. Finite-element analysis demonstrated that the strain demand was not symmetric between two flanges. The strain demand at the heel location was higher than that at the opposite flange and increased with the angle of the slope. The AISC 341 welding requirement for steel backing removal, back-gouging, and fillet reinforcing should be linked to the heel and toe locations, not the top and bottom flanges, for a sloped connection. A preferred RBS configuration where the center of the RBS is perpendicular to the longitudinal axis of the beam, not parallel to the column as was used in the test specimens, was proposed. © 2016 American Society of Civil Engineers. Source


Nawari N.O.,University of Florida | Sgambelluri M.,John A. Martin and Associates Inc.
Structures Congress 2010 | Year: 2010

All the different entities utilizing BIM technology in the construction and building industry including architects, engineers, contractors, and software developers, have diverse nomenclatures, diverse vocabularies, geometries, computing paradigms, data formats, data schemas, scales and fundamental world-views. They also have different requirements for accuracy, verisimilitude, and rendering performance. These various organizations have different standards and business processes for which they have developed their own paper and digital delivery procedures. To solve these problems, The National BIM standard (NBIMS) establishes standard definitions for building information exchanges to support critical business contexts using standard semantics and ontologies. This Standard forms the foundation for accurate and efficient communication and commerce that are needed by the construction industry. This paper investigates the general objectives of this standard, its relationship to structural engineering practice and focuses on the importance of involvement and contribution of structural engineering community to this standard. The standard is still in its infancy and the evolution and maturity of NBIMS will help to establish advanced design, communication and simulation tools that give the structural engineering community an opportunity to change the way it works in the industry, including open collaboration between stakeholders, design for optimum structure, increased energy efficiency, flexibility, constructability, comfort, and sustainability. It is important to note that agencies in the government and private sectors are currently adopting and enforcing the NBIM standard and it is becoming critical that the structural engineering community understands and delivers projects consistent with these NBIMS standards. © 2010 American Society of Civil Engineers. Source


Rojas F.,University of Southern California | Rojas F.,University of Chile | Naeim F.,John A. Martin and Associates Inc. | Lew M.,Amec Foster Wheeler | And 4 more authors.
Structural Design of Tall and Special Buildings | Year: 2011

Concepción, near the southern end of the fault rupture zone of the offshore Maule, Chile earthquake, suffered significant damage to all types of structures. Tall reinforced concrete buildings in the region were also affected, some severely. Spectacular collapse and partial collapse were experienced in two buildings, and many buildings had failure of thin shear walls that lacked sufficient boundary element confinement. Concrete spalling and crushing occurred and reinforcing steel buckled and were sometimes fractured. © 2010 John Wiley & Sons, Ltd. Source


Carpenter L.D.,WHL International Inc | Naeim F.,John A. Martin and Associates Inc. | Lew M.,Amec Foster Wheeler | Youssef N.F.,Nabih Youssef and Associates | And 3 more authors.
Structural Design of Tall and Special Buildings | Year: 2011

After the devastating offshore Maule, Chile earthquake of moment magnitude 8.8 on 27 February 2010, the Los Angeles Tall Buildings Structural Design Council (LATBSDC) organized a reconnaissance team to visit the Santiago, Concepción and Viña del Mar areas. This report summarizes the highlights of the damage observed in the Viña del Mar area on the coast 120 km west-north-west of Santiago and much closer to the subduction rupture zone than Santiago. A significant portion of Viña del Mar is uniquely situated on variable ground conditions, particularly in the area with most of the damaged buildings. The Viña del Mar area also included tall buildings constructed before and damaged by the large 3 March 1985 magnitude 7.8 Offshore Valparaiso earthquake, which were damaged again in the 2010 earthquake. The predominant observation in these buildings was the lack of confinement and ductile detailing of shear walls. The second observation was the high demand in the localized Viña del Mar area. The apparently high demand on buildings clustered in the Viña del Mar area may be an observation based on the damage since most of the taller structures in the area are somewhat clustered in Viña. But significant damage was not reported in Valparasio, which is largely, situated on higher ground which steps downward to a narrow flat area along the ocean. Similarly, significant damage was not reported in new buildings along the coast just North of Viña del Mar. The authors' conclusion based on these observations is that the ground conditions in Viña del Mar relate to the level of demand and the level of demand is higher. Demand is variable geoseismically but with the local history of many earthquakes from the same source zone, the characterization should be regularized. However, structural response is much better defined at least for confined elements with tested and predictable analytical characterization. Regardless, the detailing of reinforcing in reinforced concrete must relate to the expected demand and duration. In addition, the structural system and elements need to be designed and detailed to prepare a building to survive a higher unanticipated demand without collapse. However, despite the apparently large demands due to the large magnitude earthquake with strong aftershocks and the long duration of seismic motions, building collapses did not occur even with limited capability due to non-ductile and non-confined detailing. © 2010 John Wiley & Sons, Ltd. Source

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