Large-Scale Cyclic Testing of Steel-Plate Shear Walls with Coupling

[国外交通期刊数据库] 作者:Daniel J. Borello

摘要:The steel-plate shear wall with coupling (SPSW-WC) system is a natural extension of the conventional steel-plate shear wall (SPSW) seismic force-resisting system. The SPSW-WC configuration is created by linking a pair of SPSW piers together with coupling beams at the floor levels. Two half-scale, three-story specimens were tested using hybrid controls to simulate the bottom three stories of six-story prototype structures. The experimental SPSW-WC specimens demonstrated robust cyclic performance. Both specimens reached 4％ lateral drift, the maximum displacement that could be imposed by the facility, with minimal strength degradation. Additionally, a large amount of energy was dissipated during each test, with over 20％ equivalent viscous damping observed in the 4％ drift cycles. The web plates, horizontal boundary elements, and coupling beams all exhibited ductile response through large inelastic deformations. The SPSW-WC configuration was shown to be a viable seismic lateral force resisting system for use in high seismic regions.

Circular Concrete-Filled Steel Tubes Subjected to Coupled Tension and Chloride Corrosion

[国外交通期刊数据库] 作者:Lin-Hai Han

摘要:This paper investigates the time-dependent behavior of concrete-filled steel tubular (CFST) tensile members subjected to coupled long-term loading and chloride corrosion. A series of experiments for CFST members under both 120-day sustained tensile load and electrically accelerated corrosion in chloride solution are conducted, with loading ratio and corrosion rate as the main parameters. A finite-element analysis (FEA) model is established and validated by the test data for the full-range analysis of CFST tensile members considering the longterm behavior of the core concrete as well as the corrosion of the outer steel tube. The FEA model then is used for further analysis on CFST tensile members, including the interface performance, interaction between the steel tube and the core concrete, load distribution mechanism through the cross section, and ultimate strength. Parametric studies also are conducted, based on which a simplified method is suggested for calculating the tensile strength of CFST members under coupled long-term loading and chloride corrosion.

Reliability of Tower and Tower-Line Systems under Spatiotemporally Varying Wind or Earthquake Loads

[国外交通期刊数据库] 作者:S. C. Yang

摘要:Towers or tower-line systems within a power network can experience damages under rare earthquakes or strong winds. The estimation of the failure probability of a tower-line system is rarely addressed for scenario wind or earthquake events. One of the difficulties to evaluate the reliability of a tower or tower-line system is associated with the computationally demanding task of assessing the nonlinear inelastic dynamic responses or capacity curves of the towers under spatiotemporally varying wind or earthquake loads. An assessment of the capacity curve of a tower within the tower-line system (i.e., considering tower-wire interaction) under the spatiotemporally varying wind or earthquake loads is presented based on the incremental dynamic analysis. The estimated capacity curves are compared with those obtained using the nonlinear static pushover analysis for a single tower. The comparison indicates that the use of the nonlinear static pushover analysis could lead to useful results, although in such a case the uncertainty in the capacity curve caused by the record-to-record variability of the spatiotemporally varying loads cannot be captured. Moreover, a simple procedure to evaluate the reliability of a tower-line system for scenario wind or earthquake events is proposed by considering the spatial correlation of winds or ground motion measures. The results emphasize that the consideration of the spatial correlation of natural hazards could be important to estimate the failure probability of a tower-line system.

Prediction of the Lateral Load-Displacement Curves for Reinforced Concrete Squat Walls Failing in Shear

[国外交通期刊数据库] 作者:Yi-An Li

摘要:The reinforced concrete squat wall, which demonstrates high stiffness and load capacity, is one of the most effective earthquakeresisting members. It has been widely used in seismic design and retrofitting and thus is crucial to an understanding of the lateral loaddisplacement behavior within. Based on the strut-and-tie concept, a trilinear model is proposed to predict the lateral load-displacement curves for reinforced concrete squat walls failing in shear. This paper proposes a curve with three turning points: the cracking point associated with the apparent decrease in stiffness as the crack occurs; the strength point as the squat wall fails in shear; and the collapse point as the squat wall finally loses its axial load-carrying capacity. With a simplified calculation process, the proposed model is proven suitable for application in engineering practice and achieves successful predictions of lateral load-displacement curves for squat walls. A further comparison between the proposed model and other available models is carried out so as to further explain the differences among those models and describe their physical configurations.

Surface and Subsurface Remote Sensing of Concrete Structures Using Synthetic Aperture Radar Imaging

[国外交通期刊数据库] 作者:Tzuyang Yu

摘要:Surface and subsurface inspection of concrete structures provides useful information for the maintenance of these structures. Remote sensing techniques such as radar and microwave sensors enable engineers to assess structural condition with ease and efficiency. This paper reports the performance of a 10.5 GHz portable imaging radar system for the quantitative, surface, and subsurface sensing of concrete structures in field configuration. Ranging, size determination, crack imaging, and subsurface interface determination are conducted using stripmap synthetic aperture radar (SAR) images. Three concrete structures are selected for field measurements. Ranging accuracy, size determination procedure, and effect of background noise are studied. Issues with background subtraction are discussed. Image-based, quantitative condition assessment criteria for ranging and size determination are proposed.

Enriched Force-Based Frame Element with Evolutionary Plastic Hinge

[国外交通期刊数据库] 作者:De-Cheng Feng

摘要:This paper presents a novel enriched force-based formulation for beam-column elements. The enrichment was developed on the basis of the concept of evolutionary plastic hinges and incorporated with conventional force-based element formulation. The evolutionary plastic hinge was activated on the basis of the crushing of concrete and/or yielding of reinforcement, whereas its length was calculated adaptively according to real-time sectional forces. Several representative numerical examples are demonstrated, verifying that the proposed model can achieve accurate and objective responses regardless of the number of integration points. The spreading of plasticity in strain-hardening problems and the localization of deformation in strain-softening problems can be captured well by the proposed element.

Stability of Steel Columns Subjected to Earthquake and Fire Loads

[国外交通期刊数据库] 作者:Mehrdad Memari

摘要:Assessing the stability of steel building frames exposed to fire conditions is challenging because of the need to consider the elevated temperature properties of steel, nonuniform heating of structural members, and large deformational demands on the frames. This challenge is further intensified if the stability of the frame is also influenced by the lateral forces of an earthquake that preceded the fire. Although there has been significant progress recently in simulating the response of frames using finite-element methods, there is a need for computationally efficient tools that would minimize the modeling effort and allow for accurate and rapid assessment so that a large number of simulations can be conducted. To this end, the present study aims to develop a framework for conducting a stability analysis of steel columns subjected to demands imposed by lateral loading followed by fire. A nonlinear formulation is proposed to assess the stability of W-shaped steel columns under multihazard loading scenarios. Results from the proposed formulation show good agreement with available strength design equations of steel columns at ambient and elevated temperatures. This computationally efficient tool can be used to investigate the effects of a wide variety of variables on the stability of steel columns subjected to fire and fire following earthquakes.

Withdrawal Strength of Pneumatically Driven Steel Pin Connections in Cold-Formed Steel Light-Frame Construction

[国外交通期刊数据库] 作者:R. Serrette

摘要:Pneumatically driven steel pins have been successfully used for attaching structural sheathing to cold-formed steel framing in both load-bearing and nonload-bearing applications. The design of these types of connections is exclusively based on published manufacturer data. Attempts to analytically quantify/estimate the shear and withdrawal (tensile) strength of pin connections is nearly nonexistent. This paper proposes a mechanics-based equilibrium model for withdrawal strength and presents test data for wood structural panels connected to coldformed steel with pneumatically driven steel pins. The tests include a range of wood panel and cold-formed steel thicknesses commonly found in light-frame construction. Using the proposed model, empirically modified to reflect observed behavior, equations are presented to estimate the withdrawal strength of connections made with helically knurled pins. The proposed equations are shown to provide reasonably good estimates of strength with a reliability consistent with that of the more commonly used screw fastener.

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Behavior of Hollow-Core FRP-Concrete-Steel Columns under Static Cyclic Flexural Loading

[国外交通期刊数据库] 作者:Omar I. Abdelkarim

摘要:This paper presents the seismic behavior of hollow-core fiber-reinforced polymer (FRP)-concrete-steel (HC-FCS) columns comparable with the conventional RC column. The typical HC-FCS column consists of a concrete shell sandwiched between an outer FRP tube and an inner steel tube. The HC-FCS column represents a compact engineering system; the steel and FRP tubes act together as stay-in-place formworks. The steel tube acts as a flexural and shear reinforcement. This paper studies three large-scale columns—one RC column having a solid cross section and two HC-FCS columns. Each column has an outer diameter of 610 mm (24 in.) and a shear span-to-diameter ratio of 4.0. The steel tube is embedded into the reinforced concrete footing with an embedded length of 1.6 times the steel tube diameter, whereas the FRP tube only confines the concrete shell and truncates at the top of the footing. The HC-FCS columns exhibits high lateral drift reaching 15.2％ and fail gradually due to concrete crushing and local steel tube buckling, followed by FRP rupture. The reference RC column fails at a drift of 10.9％ due to rebar fracture. Simple beam theory overpredicts the flexural strength of the columns by an average of 9％.