Impact of Bi-directional Loading on the Seismic Performance of C-shaped Piers of Core Walls

Reinforced concrete structural walls are commonly used as the primary lateral load resisting system in modern buildings constructed in high seismic regions. Most walls in high-rise buildings are C-shaped to accommodate elevators or other architectural features. C-shaped walls have complex loading and response including: (1) symmetric response in the direction of the web, (2) asymmetric response in the direction of the flange and (3) high compression and shear demands when used as a pier in a coupled-wall configuration. A research study was conducted on C-shaped walls tested under (1) uni-directional and (2) bi-directional loading of an isolated walls and (3) bi-directional loading of a c-shaped pier in a coupled wall system. Each of the walls failed in flexure with strength loss resulting from low-cycle fatigue of the boundary element longitudinal reinforcement with buckling followed by fracture. The damage progression was as follows: (1) cracking at the wall-foundation interface, (2) concrete spalling in the web, (3) buckling and fracture of web reinforcement, (4) spalling in the flanges, (5) buckling and fracture of the bars in the boundary elements. Concrete spalling and steel bar damage occurred at lower strong-axis drift levels for the bi-directionally loaded, resulting in lower drift capacities for these loading protocols. However, for the strong-axis direction, bi-directional loading does not reduce flexural or shear effective stiffness values suggesting that current values are appropriate for design and evaluation of buildings with c-shaped walls

Analytical Evaluation of Reinforced Concrete Pier and Cast-in-Steel-Shell Pile Connection Behavior considering Steel-Concrete Interface

The seismic design of bridges may require a large-diameter deep pile foundation such as a cast-in-steel-shell (CISS) pile where a reinforced concrete (RC) member is cast in a steel casing. In practice, the steel casing is not considered in the structural design and the pile is assumed to be an RC member. It is partially attributed to the difficulties in evaluation of composite action of a CISS pile. However, by considering benefits provided by composite action of the infilled concrete and the steel casing, both the cost and size of CISS pile can be reduced. In this study, the structural behavior of the RC pier and the CISS pile connection is simulated by using an advanced 3D finite element (FE) method, where the interface between the steel and concrete is also modeled. Firstly, the FE model is verified. Then, the parametric study is conducted. The analysis results suggest that the embedment length and the friction coefficient between the steel casing and the infilled concrete affect the structural behavior of the RC pier. Finally, the minimum embedment length with reference to the AASHTO design guideline is suggested considering the composite action of the CISS pile

Phenotypic spectrum and transcriptomic profile associated with germline variants in TRAF7

PURPOSE: Somatic variants in tumor necrosis factor receptor-associated factor 7 (TRAF7) cause meningioma, while germline variants have recently been identified in seven patients with developmental delay and cardiac, facial, and digital anomalies. We aimed to define the clinical and mutational spectrum associated with TRAF7 germline variants in a large series of patients, and to determine the molecular effects of the variants through transcriptomic analysis of patient fibroblasts. METHODS: We performed exome, targeted capture, and Sanger sequencing of patients with undiagnosed developmental disorders, in multiple independent diagnostic or research centers. Phenotypic and mutational comparisons were facilitated through data exchange platforms. Whole-transcriptome sequencing was performed on RNA from patient- and control-derived fibroblasts. RESULTS: We identified heterozygous missense variants in TRAF7 as the cause of a developmental delay-malformation syndrome in 45 patients. Major features include a recognizable facial gestalt (characterized in particular by blepharophimosis), short neck, pectus carinatum, digital deviations, and patent ductus arteriosus. Almost all variants occur in the WD40 repeats and most are recurrent. Several differentially expressed genes were identified in patient fibroblasts. CONCLUSION: We provide the first large-scale analysis of the clinical and mutational spectrum associated with the TRAF7 developmental syndrome, and we shed light on its molecular etiology through transcriptome studies

Investigation of the behavior of slender reinforced concrete walls with complex configurations using nonlinear finite element analysis

Slender RC walls are used commonly in mid- and high-rise buildings to resist lateral loads arising from earthquakes and wind forces. To accommodate architectural constraints, facilitate construction, and maximize structural efficiency, the majority of these walls have complex configurations, comprising planar and non-planar wall elements that often include regular or irregular patterns of openings. To date most laboratory testing of slender RC walls has employed wall specimens with relatively simple configurations and without openings and coupling action which provides only limited understanding of the impact on performance of the variations in configuration and reinforcement detailing observed in real-world construction.This study presents a 3D continuum modeling approach to improve understanding of the behavior of walls with complex configurations and support recommendations for design of these systems. Planar wall data were used to calibrate the continuum-type modeling approach; experimental data characterizing the response of non-planar walls and walls with openings are used to validate the model

Seismic Performance of Chevron-Configured Special Concentrically Braced Frames with Yielding Beams

Current seismic design requirements for special concentrically braced frames (SCBFs) in chevron configurations require that the beams supporting the braces be designed to resist the demands resulting from the simultaneous yielding of the tension brace and degraded, post-buckling strength of the compression brace. Recent research, including large-scale experiments and detailed finite-element analyses, has demonstrated that limited beam yielding is not detrimental to chevron braced frame behavior and actually increases the story drift at which the braces fracture. These findings have resulted in new expressions for computing beam demands in chevron SCBFs that reduce the demand in the tension brace to be equal to the expected compressive capacity at buckling of the compression brace. In turn, the resultant force on the beam is reduced as is the required size of the beam. Further study was undertaken to investigate the seismic performance of buildings with SCBFs, including chevron SCBFs with and without yielding beams and X-braced frames. Prototype three- and nine-story braced frames were designed using all three framing systems, that is, chevron, chevron with yielding beams, and X SCBFs, resulting in six building frames. The nonlinear dynamic response was studied for ground motions simulating two different seismic hazard levels. The results were used to characterize the seismic performance in terms of the probability of salient damage states including brace fracture, beam vertical deformation, and collapse. The results demonstrate that the seismic performance of chevron SCBFs with limited beam yielding performs as well as or better than the conventionally designed chevron and X SCBFs

New Strategies for Maintaining Post-Seismic Operations of Lifeline Corridors

This project furthered the development of three strategies that could positively impact maintaining post-seismic operations of lifeline corridors. In Year 1, most of the focus was on the development of the three individual strategies. In Year 2, a follow-up project will include more formal assessments of the situation in which each strategy might be preferred. The first part of the investigation, performed at Oregon State University, assessed the use of high strength reinforcement (HSS) for use in reinforced concrete (RC) columns. HSS is not currently allowed in RC due to lack of information on the material characteristics and lack of performance information when used in columns. But potential benefits in construction, performance, and economics justify the need for research, especially for critical corridors. Results indicate that a column constructed with Grade 80 HSS reinforcement performs similar to column constructed with conventional Grade 60 reinforcement. The second part of the investigation, performed at the University of Washington, focused on a new type of connection between a precast concrete column and a cast-in-place drilled shaft. The column is precast with a roughened outer surface at the bottom of the column which will be embedded in the cast-in-place shaft. The connection can be built rapidly and allows generous construction tolerances. Building on two previous tests, a third quasi-static scaled connection test between a precast bridge column and a drilled shaft was performed to investigate the seismic performance of the new connection. The geometry of the test specimen was based on the minimum practical difference between the diameters of the shaft and the column, and so represented the most critical cases. The performance of the system was investigated up to a drift ratio of 10%. The experimental results showed that, if adequate confining steel is included in the splice zone, the plastic hinging mechanism forms in the column, without incurring damage in the splice zone or shaft. If the confinement is insufficient, the strength of the splice zone deteriorates rapidly with cyclic loading. Recommendations for transverse reinforcement in the transition area are provided to ensure desirable performance. The third part of the investigation, also performed at the University of Washington, focused on the performance of concrete filled steel tubes (CFST), with specific focus on connections to precast concrete piers and piles caps. CFSTs have the potential to improve performance in seismic events and decrease overall costs. CFSTs may be used for bridge piers, shafts, caissons, and columns, but their use is limited because AASHTO design specifications for CFSTs are dated and few validated, constructible connections exist. Part 3 of this report (Part 3) compares current CFST design provisions to experimental results, noting limitations and deficiencies. Improved provisions proposed for the AASHTO specifications and partly based on the AISC provisions are summarized. CFST connections are also addressed. A foundation connection capable of developing the full composite capacity of a CFST was evaluated experimentally and initial study of CFST column-to-cap beam connections was conducted using numerical simulation. Both are effective in developing and transferring the full capacity of the CFST and are summarized.Pacific Northwest Transportation Consortiu

Confinement behavior of rectangular reinforced concrete prisms simulating wall boundary elements

Observations following recent earthquakes, and from structural testing, indicate numerous brittle compression failures in rein-forced concrete seismic-resisting walls. This is unexpected, as most seismic-resisting walls are designed to be tension-controlled. The prob-lematic compressive response led to two independent studies, each individually aimed at identifying design and loading parameters that affectthe seismic deformability of the compression regions (or boundary elements) of seismic-resisting walls. These experimental studies arecombined here for a more complete understanding. Both studies used axially loaded, rectangular reinforced concrete specimens that simulateseismic-resisting wall boundary elements. The rectangular prisms were tested under cyclic axial loading or monotonic compression, with afocus on the following parameters: boundary element detailing classification, detailing of transverse reinforcement, maximum tensile strainpreceding compressive demand, and cross-sectional aspect ratio. Test results indicate that expected strength and deformation capacity can beoverestimated unless a rectangular hoop restrains every longitudinal reinforcing bar; use of crossties does not guarantee stability of thelongitudinal reinforcement. Tensile strains of 2 and 5%, imposed prior to reaching the compressive capacity, resulted in compression strengthreductions of 20 and 50%, respectively, indicating that load-history can also be important