AbstractAISC 360-16 (the current AISC Specification) does not endorse the use of high-strength materials (Fy≥525 MPa and fc′≥70 MPa) for concrete-filled steel tube (CFT) columns because of a lack ...of adequate research and comprehensive design equations. This paper makes a contribution toward addressing this gap and proposes effective stress-strain relationships and design equations for high-strength rectangular CFT members using a three-step method. The first step consists of compiling the experimental database of high-strength rectangular CFT column tests in the literature and evaluating the possibility of extending the current AISC 360-16 design equations to high-strength rectangular CFT short columns. The second step consists of developing and benchmarking detailed three-dimensional (3D) nonlinear finite-element models for predicting the behavior of high-strength CFT columns from the database. The benchmarked models are then used to perform comprehensive parametric studies to (1) address gaps in the database and (2) develop effective stress-strain relationships for modeling the steel tube and concrete infill of high-strength rectangular CFT members, while indirectly accounting for the effects of confinement, yielding, and local buckling. The third step consists of using these effective stress-strain relationships and the enhanced database to propose a new design approach (including equations) for high-strength rectangular CFT short columns. Finally, a reliability analysis is performed to establish a resistance (strength reduction) factor (ϕ) to be used with the proposed design equations.
•Fire effects on the stability behavior of steel buildings were simulated.•Components were modeled to incorporate temperature dependent nonlinear behavior.•Gravity columns were the most critical ...components for fire safety of the structure.•If a gravity column fails, steel reinforcement in slab helps redistribute the load.
This paper presents a qualitative assessment of the importance of gravity columns on the stability behavior of a typical mid-rise (10 story) steel building subjected tocornercompartment fires. Two ten-story steel buildings with composite floor systems were designed following the design practices in the US. One of thesebuildings had perimetermomentresistingframes (MRFs) to resist lateral loads while the other buildinghadan interior core of RC shear walls. Effects of gravity loads and fire conditions were simulatedusing the finite element method and numerical analysis techniques.
The results from the numerical investigations indicated that gravity columnsgovernthe overall stability of building structures under fire conditions.Gravity columns have the highest utilization ratio, and they are most likelyto reach their critical temperatures first. If gravity column failure occurs, the loadshed or droppedby the failed columnhas to be redistributedto the neighboring columnsto maintain overall structural stability. This axial load redistribution canoccur through the development of alternate load pathsincludingcatenary action. Simulation results indicate that the presence of steel reinforcementin the concrete slabs (inadditionto the minimum shrinkage reinforcement)facilitates uniform redistribution of the axial load dropped by the failed gravity column to the neighboring columns. The additional steel reinforcement improves the flexural and tensile strengths of the composite floor system,which enhances its ability to develop alternate load paths including catenary action in the slab, and thus maintain structural stability after gravity column failure.
AbstractThis paper focuses on local buckling and axial compressive behavior of steel-plate composite (SC) walls. SC walls are comprised of a concrete wall sandwiched between two steel faceplates on ...the surfaces. The steel faceplates are anchored to the concrete core using stud anchors and (or) ties and connected to each other using ties. When subjected to axial compression, the steel faceplates can undergo local buckling between the anchor points. The local buckling and axial compressive behavior of SC walls depend on the faceplate slenderness ratio, reinforcement ratio, and strength of steel and concrete materials. A database of axial compressive tests conducted around the world is compiled and analyzed to evaluate the influence of various parameters on the local buckling and axial compressive behavior of SC walls. Experimental investigations are conducted on nine SC wall specimens with a wide range of faceplate slenderness parameters to further evaluate the local buckling and axial compressive behavior of SC walls. The test results are discussed in detail and added to the existing database. Using the enhanced database, a design equation is proposed to calculate the axial compressive strength of SC walls. A standard reliability analysis is performed to calculate an appropriate strength reduction factor (ϕ) for the proposed equation.
AbstractThis paper investigates the behavior of high-strength circular concrete-filled steel tube (CFST) short columns. An experimental database consisting of 87 tests conducted on high-strength ...circular CFST short columns was compiled, and gaps in the existing research were identified. A total of 20 tests were then conducted to address the gaps in the database. The test parameters were the diameter-to-thickness ratio of the steel tubes D/t , the yield stress of steel Fy, and the compressive strength of concrete fc′. The tests indicated that the strength of high-strength circular CFST short columns increases with increasing Fy and fc′, but decreases with increasing D/t. All tested high-strength circular CFST short columns had acceptable ductility. Four of the specimens did not have any strength degradation, while the other 16 specimens retained at least 70% of their strength at strains of 5%. Results from the tests conducted in this research were combined with those from the compiled database; the combined results were used to evaluate the applicability of current design equations for estimating the cross-sectional strength of high-strength circular CFST columns. The evaluations indicated that the Japanese code provides the most accurate estimation.
AbstractDouble-skin composite (DSC) walls consist of a thick concrete infill sandwiched in between two steel faceplates on the exterior surfaces. DSC walls used in high-rise buildings have higher ...reinforcement ratios and are subjected to larger axial-force ratios as compared to DSC walls used in safety-related nuclear facilities. This paper presents the results of experimental and numerical investigations conducted to evaluate the cyclic in-plane shear behavior of DSC walls for high-rise buildings, and the influence of higher reinforcement ratios and axial-force ratios. The DSC wall specimens were designed with a reinforcement ratio of 6.4%, and with flange walls designed as boundary elements to ensure that the walls would be shear critical. The wall specimens failed by cyclic yielding and local buckling of the steel faceplates in the web walls, and eventual crushing of the concrete infill. The steel faceplates prevented spalling of the crushed concrete and as a result, the wall specimens had stable hysteretic loops and large shear-deformation capacity. Using vertical stiffeners and tie battens as connectors further increased the shear-deformation capacity of the wall specimens, with the ultimate shear strain reaching 3%. A mechanics-based model (MBM) was used to analyze the in-plane shear response of the wall specimens. The experimental and analytical investigations indicate that axial compression has limited influence on the shear strength, but decreases the shear-deformation capacity of the DSC walls. Analytical parametric studies indicate that for DSC walls made using normal-strength concrete and steel, high reinforcement ratios (of over 7.5%) and high axial-force ratios (exceeding 0.40) can potentially lead to crushing of the concrete infill prior to yielding of steel faceplates, and thus nonductile failure modes. Finally, the design equations specified in various codes are verified using experimental results of 42 specimens from past tests and from this experimental program. Those code equations provide reasonable and conservative estimations of the shear strength of DSC walls, with the ratio of experimental-to-calculated values equal to approximately 1.30 on average.
Neural Projection Mapping Using Reflectance Fields Erel, Yotam; Iwai, Daisuke; Bermano, Amit H.
IEEE transactions on visualization and computer graphics,
2023-Nov., 2023-11-00, 20231101, Letnik:
29, Številka:
11
Journal Article
Recenzirano
We introduce a high resolution spatially adaptive light source, or a projector, into a neural reflectance field that allows to both calibrate the projector and photo realistic light editing. The ...projected texture is fully differentiable with respect to all scene parameters, and can be optimized to yield a desired appearance suitable for applications in augmented reality and projection mapping. Our neural field consists of three neural networks, estimating geometry, material, and transmittance. Using an analytical BRDF model and carefully selected projection patterns, our acquisition process is simple and intuitive, featuring a fixed uncalibrated projected and a handheld camera with a co-located light source. As we demonstrate, the virtual projector incorporated into the pipeline improves scene understanding and enables various projection mapping applications, alleviating the need for time consuming calibration steps performed in a traditional setting per view or projector location. In addition to enabling novel viewpoint synthesis, we demonstrate state-of-the-art performance projector compensation for novel viewpoints, improvement over the baselines in material and scene reconstruction, and three simply implemented scenarios where projection image optimization is performed, including the use of a 2D generative model to consistently dictate scene appearance from multiple viewpoints. We believe that neural projection mapping opens up the door to novel and exciting downstream tasks, through the joint optimization of the scene and projection images.
Rectangular concrete-filled steel tube (CFT) members are categorized as compact, noncompact or slender depending on the slenderness ratio (width-to-thickness b/t ratio) of the steel tube walls. ...International design codes typically focus on the design of compact CFT members with relatively small slenderness (b/t) ratios. The behavior and design of noncompact or slender CFT members is not addressed directly. This paper presents the basis of the current AISC Specification (AISC 360-10) for the design of noncompact or slender rectangular CFT members under axial compression, flexure, and combined axial and flexural loading. The experimental database of tests conducted on noncompact and slender CFT members is reviewed. Design equations are developed based on the experimental results and observations. Detailed 3D finite element method (FEM) models are developed for noncompact and slender CFT members, and benchmarked using experimental results. The benchmarked models are used to address gaps in the experimental database, and further verify the conservatism of the design equations.
•Presents the basis of the AISC 360-10 design provisions for rectangular CFTs•Establishes the conservatism of the design provisions using experimental database•Develops and benchmarks 3D finite element models for rectangular CFTs•Further verifies conservatism of design provisions using benchmarked models•3D finite element models predict behavior of noncompact and slender CFTs.
AbstractPlanar composite plate shear walls/concrete filled (C-PSW/CF) consist of two steel web plates and two flange (or closure) plates making up a long hollow box section that is filled with ...concrete. The web plates are connected to each other using regularly spaced steel tie bars. Steel headed stud anchors (shear studs) may be added to reduce the steel plate slenderness for local buckling considerations in the composite phase. This paper presents the results of experimental investigations conducted to evaluate the behavior of five planar C-PSW/CF specimens subjected to constant axial compression and cyclic lateral loading. Parameters included are the axial load level, steel plate slenderness ratio, and tie reinforcement ratio. The cyclic lateral load-deflection responses of the composite wall specimens are discussed along with their lateral stiffness, strength, and deformation capacity. Experimental results indicate that the lateral load capacity of composite walls is governed by flexural yielding of the steel plates followed by plate inelastic local buckling and concrete crushing. All the wall specimens developed and exceeded the flexural capacity calculated using the plastic stress distribution method (while including the effects of axial compression). The post-peak strength degradation of wall specimens is governed by the initiation and propagation of fracture through the steel flange plates and web plates. A fiber-based model was developed and used to calculate the section moment-curvature response of the specimens. Comparing the experimental and numerical moment-curvature responses indicates that the section flexural stiffness and flexural capacity can be estimated using the fiber-based analysis method.
Steel concrete composite (SC) walls are being used for the third generation nuclear power plants, and also being considered for small modular reactors. SC walls consist of thick concrete walls with ...exterior steel faceplates serving as reinforcement. These steel faceplates are anchored to the concrete infill using shear connectors, for example, headed steel studs. The steel faceplate thickness (tp) and yield stress (Fy), and the shear connector spacing (s), stiffness (ks), and strength (Qn) determine: (a) the level of composite action between the steel plates and the concrete infill, (b) the development length of steel faceplates, and (c) the local buckling of the steel faceplates. Thus, the shear connectors have a significant influence on the behavior of composite SC walls, and should be designed accordingly. This paper presents the effects of shear connector design on the level of composite action and development length of steel faceplates in SC walls. The maximum steel plate slenderness, i.e., ratio of shear connector spacing-to-plate thickness (s/tp) ratio to prevent local buckling before yielding is also developed based on the existing experimental database and additional numerical analysis.
•Non-contact lap splice for connecting steel-plate composite (SC) walls and reinforced concrete (RC) structures.•Experimental investigations evaluating the influence of design parameters on ...performance of connections.•Design recommendations for the non-contact lap splice connections.
Non-contact lap splices may be considered for connecting steel-plate composite (SC) walls to conventional reinforced concrete (RC) structures. This connection type is preferred over mechanical splice connections because of perceived construction efficiency. The primary components of the non-contact lap splice connection are the steel rebars, which are fully developed in the RC structure and extended and embedded in SC walls to transfer tensile stresses to the steel faceplates. The structural performance of a non-contact lap splice connection depends on the detailing of rebars (embedment length and location relative of stud anchors) embedded in SC walls, and the design of stud anchors (spacing and size) along the rebar length. This paper presents the results of experimental investigations conducted on SC-to-RC non-contact lap splice connections to evaluate the influence of various design and detailing parameters on structural performance, failure modes, and the ability to develop full-strength connection design. Design recommendations developed previously for SC-to-RC non-contact lap splice connections were reviewed and modified based on the results of experimental investigations.
