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Composite plate shear walls/concrete-filled (C-PSW/CFs), also known as SpeedCore systems, are a relatively new structural member in American codes and standards. Prior research has focused primarily on C-PSW/CF walls with either flange/closure plates or filled composite members as boundary elements. Walls without boundary elements have also been studied, but they are no longer permitted by the American Institute of Steel Construction (AISC 341-22). The reason is that composite walls without boundary elements do not provide adequate ductility for seismic design. This paper presents the results of experimental and numerical studies conducted to evaluate the cyclic lateral load behavior of C-PSW/CFs using hot-rolled structural steel members as boundary elements. The steel web plates of the C-PSW/CF specimens were connected to each other using threaded tie bars with double nut connections. Composite interaction between the steel and concrete infill was achieved using the tie bars and additional shear studs welded to the boundary elements. The composite walls were embedded and anchored to reinforced concrete foundation blocks using welded deformed bar anchors. The experimental investigations focused on the cyclic lateral load-drift responses including test observations and limit states, moment-rotation response of the plastic hinge and the section moment-curvature relationship, overall lateral stiffness, strength, and displacement ductility. The experimental results show that the specimens exceeded their nominal flexural capacities calculated using the plastic stress distribution method or fiber-based section modeling using measured material properties. The specimens had plastic hinge rotation capacity greater than 0.028 rad. and displacement ductility ratio greater than 5.2. Detailed 3D nonlinear inelastic finite element models and simpler fiber-based macro models of the tested specimens were developed and benchmarked using experimental results. The detailed 3D finite element models can reasonably simulate the global and local behavior of the specimens, and are recommended for conducting further parametric studies of composite wall design details. Simpler fiber-based macro models can efficiently simulate the cyclic lateral load behavior of the specimens, and are recommended for modeling C-PSW/CFs while simulating the behavior of multi-story building structures. [ABSTRACT FROM AUTHOR]

Existing projects indicate that a large number of pile boreholes formed via cement fly ash gravel (CFG) pile construction in soft soil could produce a borehole group effect in the absence of timely backfilling. The borehole group effect could cause ground settlement and threaten the safety of adjacent buildings, tunnels, and pipelines. However, the mechanism of the borehole group effect, causing serious deformation in surrounding soil, has seldom been studied, and there exists no simple simulation method to predict the borehole group effect. In this study, a case involving CFG pile boreholes in a soft soil area causing a significant settlement of surrounding buildings was introduced. Based on this case, a centrifuge test was designed to simulate the influence of a single borehole and multiple boreholes on the surrounding soft soil. The mechanism of the borehole group effect was investigated via centrifuge tests and the finite-element method. In the case of a single borehole, a horizontal circumferential stress arch and vertical stress transfer arch were formed in the soil, which effectively limited the shrinking deformation of the borehole wall. In the case of a large number of boreholes with a small spacing, the horizontal and vertical stress arches around the boreholes affected and weakened each other. As a result, the shrinking deformation of the borehole group was greater than that of the single borehole. In other words, the borehole group effect was found to cause serious deformation in the surrounding soil. To overcome the difficulty in the simulation of a large number of pile boreholes in engineering, the borehole-type conversion and multihole merging method was proposed. The simulation results indicated that the simplified method was reasonable. [ABSTRACT FROM AUTHOR]

This paper presents a new method for the nonlinear analysis of rafts resting on multilayered heterogeneous soils using the Vlasov model. The finite-element and the finite-difference methods are employed to solve the governing differential equations for the flexure of the raft and the displacement within the supporting soil mass, respectively. The soil heterogeneity in the vertical direction or in the horizontal directions within each soil layer is considered, and the soil nonlinearity is taken into account through the reduction of the soil shear modulus as a function of strains within the supporting soil mass. Through a comprehensive comparative study, it is found that the present method is validated as reasonable by field measurements and is in good agreement with nonlinear three-dimensional finite-element analysis and other existing analysis methods. A study is carried out to investigate the effect of soil layering, soil nonlinearity, and soil heterogeneity in the vertical direction and in horizontal directions on the raft behavior. It is concluded that neglecting the real conditions of the supporting soils (e.g., soil layering, soil nonlinearity, and soil heterogeneities in the vertical or in horizontal directions) in the analysis of the soil–raft interaction leads to an unrealistic prediction of the raft behavior. [ABSTRACT FROM AUTHOR]

Combined piled raft foundation (CPRF) is an effective solution for supporting high-rise constructions. The traditional design philosophy of CPRF does not consider the capacity of foundation based on combined vertical (V), horizontal (H), and moment (M) load. However, V-M-H load acts on the CPRF system concurrently due to the action of wind, wave, earth pressure, and earthquake loading in addition to gravity loading. In this context, the present investigation deals with the effect of combined V-M-H load interaction on the behavior of CPRF in sand and clay, respectively. The response of CPRF under combined loading is obtained using a 3D finite element analysis. First, validation of the numerical model is performed considering the model test results conducted in Agartala sand and another based on the available field test result of Messeturm Tower in Frankfurt clay obtained from the literature. Further, failure and design envelopes for the validated CPRF system are developed considering V-M-H load in both sand and clay deposits attributing a variety of influential system parameters. Simplified expressions for design lateral and moment capacities are proposed based on multiple linear regression analysis. Finally, the implication in design based on the findings of the present study is illustrated using a prototype case study structure. [ABSTRACT FROM AUTHOR]

This study investigates the influence of soil–structure interaction (SSI) on period and damping of steel moment-resisting frame buildings supported by shallow footings on dry sand deposits. A series of impact hammer tests were conducted on a 3-story and a 6-story model steel frame for this purpose. Different base conditions (e.g., loose and dense sand beds, surface and embedded footings, heavily loaded and lightly loaded footings) were considered to gain a complete understanding of inertial SSI effects. Experimental results were compared with FEMA provisions as well as with analytical results obtained from a finite-element model. The period and damping amplifications are more prominent in the case of the 3-story building than in that of the 6-story building, indicating more sensitivity of short and stiff buildings to SSI over the taller ones. For a heavily loaded 3-story building on loose sand, the period and damping amplifications are 21 and 330%, respectively. Although the analytical results match well with those of the experiment, FEMA provisions tend to overestimate the responses, especially for the 6-story building. [ABSTRACT FROM AUTHOR]

Piles have been used to transfer superstructure (bridges, buildings, etc.) loads to deeper competent bearing strata to minimize settlements. Accurate predictions of design settlements of vertically loaded piles under working load are a critical issue in the design of pile foundations. Numerous comprehensive trials, built on a regression-based predictive formula that produces the axial settlement using elastic shortening as the input variable, were performed in this study, and a simple relationship was established between the elastic shortening of piles and the measured design settlements of 93 full-scale pile load tests installed in variable bearing materials. The calculated axial settlements of piles from the proposed method in this study were compared to the measured axial settlements of the piles. Accuracy and validity of the proposed method were verified through conventional statistical analysis in terms of mean of bias (λm) and coefficient of variation (μ). The proposed method yielded values of λm =1.06 and μ =0.15. [ABSTRACT FROM AUTHOR]

Evaluation of the uplift capacity of plate anchors in saturated clay is an important aspect in the design of offshore foundation systems of various structures. In most of the literature reviewed, simple constitutive models such as Tresca or Mohr-Coulomb (MC) have been used in evaluating the plates' pullout capacity. There exists a need to study the pullout capacity of anchors using other advanced soil models and explore differences in computed behavior. In addition to the MC model, two other constitutive models are used herein to represent the soil behavior. These are Modified Cam-Clay and Soft Soil models. A series of finite-element analyses are performed using the three constitutive models. Undrained effective stress analyses are conducted to study the response of both strip and circular plate anchors in saturated soils. The capacities of plate anchors are assessed through the application of the displacement control approach. The effective stress parameters are correlated with the undrained shear strength, and Nc (dimensionless breakout factor) values from the three constitutive models are presented and compared with the lower bound solution, as well as with the data obtained from similar studies and experimental data available in the literature. Differences resulting from the characteristics of the three constitutive models are examined and discussed. [ABSTRACT FROM AUTHOR]

Scouring is a significant problem on river bank and coastal protection systems. Severe scouring can cause damaging consequences to geotextile tube embankment structures. In this study, five case scenarios of an embankment system supported by stacked geotextile tubes were analyzed using a commercially available finite-element analysis software. These case scenarios include (1) conventional geotextile tube stacking on ground base foundation; (2) geotextile tube stacking on gravel bedding foundation; (3) geotextile tube stacking on excavated foundation; (4) geotextile tube stacking on excavated foundation with gravel bedding; and (5) fortification of stacked geotextile tubes by riprap protection. Each case scenario is simulated under normal loading and critical loading conditions with and without scouring at the base toe of the embankment system. Results suggest that the potential problems that occur during scouring and critical states of the embankment system instigate failures that could destabilize the geotextile tube retaining structure. Among all the case scenarios considered, additional fortification by riprap increases the performance and global stability of the geotextile tube embankment system. [ABSTRACT FROM AUTHOR]

With the existence of aging highway bridges within the U.S. transportation network, federal and local agencies typically encounter a wide assortment of maintenance issues ranging from cracking, spalls, delaminations, and corrosion to high load hits and fire damage. This paper presents an approach for capturing the full system-based behavior and stages of failure in the composite bridge superstructures as they approach ultimate capacity. This step is instrumental to understanding how redundant bridges behave in the presence of coupled and uncoupled damage and deteriorations. The investigation included a comprehensive nonlinear finite-element analysis of two representative intact composite steel girder bridges that were tested to failure and provided sufficient details for model validation. Results demonstrate the high degree of additional reserve capacity, inherent to redundant superstructures, over the theoretical nominal design capacity. A rational approach was established to describe the actual system-based ultimate capacity, which was not explicitly considered in the current design methodology. In addition, a limited sensitivity study was performed on one of the selected representative bridges to investigate the sensitivity of the characterized failure stages to variations in the geometrical parameters and material properties of the bridge system. [ABSTRACT FROM AUTHOR]

This article presents the findings of an investigation that used finite-element analysis to determine the influence of a concrete footing's dimensions on its temperature development and cracking at early age. A three-dimensional finite-element model was used to predict temperatures in the footing and to assess cracking potential of the concrete. A parametric study consisting of 63 finite-element analyses was conducted on three different footing shapes: (1) a cubic shape, (2) a length:width:depth ratio of 4:4:1, and (3) a length:width:depth ratio of 4:2:1. Volume-to-surface area ratios () ranged from 0.33 to 4.0 m. The results showed that cracking potential does not depend on a footing's dimensions when its is 1.3 m or greater. Rectangular footings that have the same but different shapes (dimensional proportions) developed a similar maximum temperature, a similar maximum temperature differential, and a similar minimum crack index under the same insulation condition. Smaller footings allowed slightly higher maximum temperature differential before thermal cracking occurred. [ABSTRACT FROM AUTHOR]