Background
Alopecia areata (AA) is an organ‐specific autoimmune disease with T‐cell‐mediated attack of hair follicle autoantigens. As T helper 17 (Th17) cells and T regulatory (Treg) cells are ...crucially involved in the pathogenesis, the role of Th17 and Treg cytokines has not been studied yet.
Objective
To determine whether AA is associated with alterations in lesional and serum Th17 and Treg cytokines and studied whether they were associated with clinical type.
Methods
Scalp skin samples from 45 patients and eight normal controls were obtained for PCR specific for IFN‐γ, TNF‐α, TGF‐β, IL‐1, IL‐2, IL‐4, IL‐10, IL‐12A, IL‐13, IL‐17, IL‐22 and IL‐23. Serum cytokines were measured from 55 patients and 15 normal controls using ELISA.
Results
Lesional IL‐17 and IL‐22 were significantly increased in patient group. Moreover, positive correlations were shown between lesional IL‐17, IL‐22 and disease severity. Serum IL‐1, IL‐17, TNF‐α and TGF‐β were significantly increased, and positive correlation was shown between serum IL‐17 and disease severity.
Conclusion
These results showed significantly high Th17 cytokines in both lesion and serum in AA patients, which may highlight a functional role of these cytokines in the pathogenesis of AA.
AbstractThis paper presents a computational investigation of two reinforced concrete beam-column assemblies, each comprising three columns and two beams, subjected to monotonically increasing ...vertical displacement of the unsupported center column simulating a column removal scenario. One assembly was part of an intermediate moment frame and the other was part of a special moment frame. Two types of models were developed: (1) detailed models with highly refined solid and beam elements to represent the nonlinear material behavior of concrete and reinforcement, and (2) reduced-order models with significantly fewer beam and spring elements to represent the nonlinear behavior of structural components. Reduced models are desirable for analysis of complete three-dimensional (3D) structural systems. Modeling approaches for the detailed and reduced models are described, and the computational results are compared with experimental data from full-scale tests. Good agreement is observed, which demonstrates the capability of the detailed and reduced models to capture the primary response characteristics and failure modes, including the successive development of compressive arching action and catenary action in the beams and the fracture of reinforcing bars at the beam-column interface.
AbstractSince the events of September 11, 2001, the engineering community has devoted increased attention to evaluating the vulnerability of multistory buildings to disproportionate collapse, ...including substantial research and standards development. This paper reviews recent research conducted by the NIST on the robustness of RC buildings, including experimental validation of both high-fidelity and reduced-order modeling approaches using measurements from subsystems and an entire building tested under column removal scenarios. A robustness index was developed using pushdown analysis of a structure with initial damage to allow an evaluation and comparison of the disproportionate collapse potential of various structural systems using the validated modeling approaches. It is shown that the robustness index is sensitive to differences in the strength and detailing of the structural system, providing higher values for buildings with more stringent design requirements. Further, the paper presents a novel approach for enhancing the robustness of RC beams through local debonding of tensile reinforcing bars at the joints, where significant cracking occurs after a column loss. Experimental and computational studies were conducted to demonstrate the efficacy of this approach. It is shown that debonding of the bottom bars for a length of two beam depths on each side of a central column results in an improvement of more than 30% in the peak vertical load-carrying capacity under a column removal scenario.
The results of recent research on the dynamic response, failure mechanism, and changes in the load-transfer paths of a half-scale three-story, three-bay, and three-span reinforced concrete frame ...subjected to a series of sudden column removals are presented. Three phases of testing were carried out, including the removal of a corner column and a column adjacent to the corner column along the short span direction, two middle exterior columns along the long span direction, and one interior column. The column removal was enabled by using a gas cannon. The dynamic response at critical locations after the imposed failure of the respective columns was observed. The removal of the corner column followed by the adjacent column resulted in only an essentially elastic response of the structure. The removal of an interior column resulted in only small deflections. The removal of the two first-story exterior columns resulted in significant vertical deflections of the middle exterior columns and significant yielding at adjacent beams that framed into the two middle exterior columns.
This paper presents an experimental and computational assessment of the performance of steel and reinforced concrete beam-column assemblies under monotonic vertical displacement of a center column, ...simulating a column removal scenario. The assemblies represent portions of structural framing systems designed as intermediate moment frames (IMFs) and special moment frames (SMFs) for Seismic Design Categories C and D, respectively. The steel IMF and SMF assemblies were designed in accordance with ANSI/AISC 341-02 by using prequalified moment connections specified in FEMA 350. The concrete IMF and SMF assemblies were designed and detailed in accordance with ACI 318-02 requirements. Each full-scale assembly comprises two beam spans and three columns, and downward displacements of the center column are imposed until failure. The study provides insight into the behavior and failure modes of the assemblies, including the development of catenary action. Both detailed and reduced finite-element models are developed, which capture the primary response characteristics and failure modes. Analyses with the reduced models can be executed rapidly without loss of accuracy, facilitating implementation in models of entire structural systems.
This paper presents a computational investigation of the robustness of a typical concrete deck–steel beam composite floor system with simple shear connections in the event that a center column has ...been removed. The study provides insight into the behavior and failure modes of simple shear connections and composite floor systems comprised of such connections. Analyses of a connection subassemblage indicate that loads are primarily resisted by cable action of the beams after column loss resulting in increasing tensile forces in the beams and connections that could eventually precipitate failure. Simulation results show that the floor deck contributes significantly to the floor system response through: diaphragm action to prevent the exterior columns from being pulled inward and membrane action primarily through the reinforcement mesh and metal deck. The analyses indicate that the capacity of the analyzed floor system under the column removal scenario is significantly less than the load specified by the General Services Administration’s current progressive collapse guidelines. This suggests that applying these guidelines, the composite floor system studied would be vulnerable to collapse if a center column is lost.
The potential for progressive collapse of a typical reinforced concrete (RC) moment frame structure initiated through the loss of one or more first-story columns is numerically simulated using a ...macromodel-based approach. The development of the simulation model is guided by the realization that the characterization of nonlinear behavior associated with the transfer of forces through the joint is critical to predict the large deformation response associated with progressive collapse. A simplified simulation model of a beam-column joint is used to represent essential and critical actions in the floor beams and the transfer of these forces through the joint region to the vertical elements. The validity of the macromodel developed is evaluated through comparison of both overall response and element actions with those obtained from high-fidelity finite-element analyses. Two prototype buildings designed for lateral load requirements in a nonseismic and seismic region are considered in progressive collapse studies. Two-dimensional models of the frames are subjected to gravity loads and then one or more first-story columns are removed, and the resulting large displacement inelastic dynamic response of each frame is investigated. It is demonstrated that the proposed approach using a validated macromodel is a viable methodology for progressive collapse analysis. The study also finds that special RC moment frames detailed and designed in zones of high seismicity perform better and are less vulnerable to progressive collapse than RC frame structures designed for low to moderate seismic risk.
AbstractThis paper presents an experimental study of two full-scale steel beam-column assemblies, each comprising three columns and two beams, to (1) define their response characteristics under a ...column-removal scenario, including the capacity of the beams and their connections to carry loads through catenary action, and (2) provide experimental data for validation of beam-to-column connection models for assessing the robustness of structural systems. The assemblies represent portions of the exterior moment-resisting frames of two 10-story steel-frame buildings. One test specimen had welded unreinforced flange, bolted web connections, and the other had reduced beam–section connections. When subjected to monotonically increasing vertical displacement of the unsupported center column, both specimens exhibited an initial elastic response dominated by flexure. With increased vertical displacement, the connections yielded, and axial tension developed in the beams. The axial tension in the beams increased until the connections failed under combined bending and axial stresses. The test results show that the rotational capacities of both connections under monotonic column displacement are about twice as large as those based on seismic-test data.
This article presents an experimental study of two full-scale reinforced concrete (RC) beam-column assemblies under a column removal scenario. The assemblies represent part of the exterior ...moment-resisting frames of two 10-story RC frame buildings: one designed for Seismic Design Category C (SDC C), and the other for SDC D. Intermediate moment frames and special moment frames are integrated in the SDC C and SDC D designs, respectively. The assemblies were subjected to monotonically increasing vertical displacement of the center column. With increased vertical displacement, three stages of load-carrying mechanism are clearly seen. The test results show that, the ultimate loads under the column removal scenario are primarily resisted through the development of catenary action. The tensile force increase is limited by the fracture strength of the tensile reinforcement of the beams. The beam-end rotational capacities under monotonic column displacement are seven to eight times as large as the acceptance criterion in ASCE/SEI 41-06, which are based on seismic test data.
AbstractThis paper presents a computational investigation of the response of steel beam-column assemblies with moment connections under monotonic loading conditions simulating a column removal ...scenario. Two beam-column assemblies are analyzed, which incorporate (1) welded unreinforced flange bolted web connections, and (2) reduced beam section connections. Detailed models of the assemblies are developed, which use highly refined solid and shell elements to represent nonlinear material behavior and fracture. Reduced models are also developed, which use a much smaller number of beam and spring elements and are intended for use in future studies to assess the vulnerability of complete structural systems to disproportionate collapse. The two modeling approaches are described, and computational results are compared with the results of the full-scale tests described in the companion paper. Good agreement is observed, demonstrating that both the detailed and reduced models are capable of capturing the predominant response characteristics and failure modes of the assemblies, including the development of tensile forces associated with catenary action and the ultimate failure of the moment connections under combined bending and axial stresses.
