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Hurricane and tsunami events can generate extreme water flows in nearshore regions of the United States with catastrophic consequences to coastal structures. Field records have shown that light-frame wood structures exhibit high vulnerability to wave-induced forces due to their light construction characteristics, which feature flexible connections and slender pile foundation systems. Previous research has studied the behavior of these structures under wave action, but most studies used rigid body modeling, which is shown in this study to be insufficient for capturing the force demand on these structures. Using a fluid-structure interaction (FSI) framework, this research investigated the structural and soil flexibility effects in the interaction between elevated light-frame wood structures and water flows. Study variables included the flexibility of timber-to-timber connections, soil type, pile embedment, wavelength, and wave amplitude. The study concluded that structural and soil responses to water flows can introduce strong coupled motions. Neglecting this coupling effect may underestimate the force demand on the light-frame wood structures by more than 40%. Accounting for both structural and soil flexibilities is necessary to accurately quantify the wave force demand of these structures. [ABSTRACT FROM AUTHOR]

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]

This study examines the behavior of high-mast lighting pole (HMLP) foundations through the use of nonlinear finite-element modeling. HMLPs utilize nuts and threaded rods to clamp the light pole structure's base plate to the foundation. Inspections by the Alaska Department of Transportation and Public Facilities (AKDOT&PF) have revealed widespread loosening of the nuts used on HMLPs over time. The threaded rods used are F1554 Grade 55, which are heat treated from mild steel rods, Fy = 248 MPa (36 ksi) to gain additional yield strength. This study briefly highlights the difference in postyield behavior in mild steel and high-strength steel, and proposes a probable mechanism behind the clamp-load loss experienced by Alaska's HMLPs. Because the HMLPs are much taller than traditional lighting poles, they experience larger external wind loading. This wind load is potentially stressing threaded rods into the postyield range. A previous study shows that the current tightening procedure is likely not undertightening nuts, which could be a major culprit behind loosening. As a result of this and previous research, it is believed that the nuts aren't loosening in the traditional sense--losing clamp load by rotating on the threads. Instead, the threaded rods undergo significant postyield strain during external loading. This plastic deformation is large enough in magnitude to cause the bolted joint interface to lose clamp load when the external force is removed. One factor that exacerbates this effect in some pole configurations is prying action, which is not accounted for in the design. The clamp loss mechanism is examined by applying wind loads to three pretensioned HMLP configurations using finite-element analysis software (ABAQUS). The analysis uses 3-D solid elements, contact surfaces that allow for separation, bonding surfaces where contact surfaces are not required, boundary conditions that approximate reality, displacement controlled pretension, and external wind loading represented by coupled moments. [ABSTRACT FROM AUTHOR]

This paper presents the earthquake response of three low-rise frame-wall-foundation centrifuge building models, including a structural hinging-dominated, foundation rocking-dominated, and balanced design model. The models were designed such that the capacities of the dominant inelastic elements varied; however, each was subjected to a similar sequence of earthquake shaking in a 30-g centrifuge environment to facilitate comparison. Experimental results reveal that the traditional frame-wall building with a strong foundation (i.e., a hinging-dominated system) has the least potential to recover from displacements induced during earthquake shaking. As a result, this system suffered the most significant residual deformation. In contrast, systems with rocking foundations sustained a smaller peak roof acceleration, residual drift, and peak base shear despite the relatively larger peak transient drift demand. Consistent with slow cyclic test results, dissipated hysteretic energy was reasonably distributed amongst superstructure and substructure inelastic components in the balanced model during moderate and high intensity shaking. [ABSTRACT FROM AUTHOR]

The mechanism of foundation rocking has received much attention recently due to its appealing seismic resistant features, namely, self-centering tendency and energy dissipation capability. It is well recognized, however, that other inelastic mechanisms will contribute to a system's seismic resistance. Considering the strength difference between a rocking footing and a shear wall structural fuse, and the system symmetry, six different two-story-two-bay frame-wall-foundation building models were constructed and tested in a geotechnical centrifuge. In this paper, the test program and experimental results when the models were subjected to slow cyclic loading are presented. A companion paper presents results from the dynamic phase of testing. Results indicate that, with the aid of foundation rocking, the system behaves in a ductile and stable manner with no strength degradation, even when the model is pushed to a drift of more than 2.5%. Importantly, when structural and foundation component strengths are approximately equal, the hysteretic energy is reasonably distributed among the superstructure inelastic components and the rocking foundations. Finally, numerical analyses predictions demonstrate comparable local and global response to measurements obtained during the experiments. [ABSTRACT FROM AUTHOR]

Two geotechnical centrifuge tests were designed to elicit the influence of soil-foundation-structure interaction (SFSI) and structure-soil-structure interaction (SSSI) effects on the seismic demands of an inelastic frame structure founded on individual spread footings. Four experimental cases were considered: (1) SFSI of an individual inelastic frame structure (baseline case); (2) in-plane SSSI between the frame structure and a large elastic wall structure designed to respond predominately in a rocking mode; (3) anti-plane SSSI between the frame and wall structures; and (4) combined in-plane and anti-plane SSSI between the frame structure and two wall structures. Results from Cases 1, 2, and 4 are analyzed considering 13 demand parameters. The peak seismic demands from the baseline case are compared to the peak demands from the SSSI cases to elicit the impacts of building adjacency. The number of earthquake motions that resulted in increases or decreases in the seismic demands in the frame structure are tracked for the SSSI cases. For these tests, SSSI consistently results in increased peak foundation moment and foundation base shear demands, regardless of the geometric layout of the structures. These increases propagate throughout the superstructure, resulting in increases in moment, shear and curvature ductility demands in the structural components. SSSI effects are observed to be most significant for low-to-moderate intensity earthquake motions, suggesting that particular consideration should be given to the likelihood of SSSI for highly probable earthquakes. [ABSTRACT FROM AUTHOR]

Although the nonlinear behavior of rocking shallow foundations has been experimentally and numerically demonstrated as an effective tool to dissipate vibrational energy during seismic loading, the engineering community has yet to uniformly accept it as a targeted design mechanism for diffusing seismic energy in a structure. This paper presents results of a centrifuge test program that incorporated inelastic behavior into model building systems via yielding of both structural and foundation components. Three 2-story-1-bay building models were designed with similar layouts but different combinations of foundation and structural component yield strengths and were shaken with a similar suite of earthquake motions. Measurements of behavior of each of the model buildings are presented and cross-compared in terms of time history responses, hysteretic responses of the structural and foundation fuses, and maximum response parameters. A balanced design configuration, wherein the rocking foundation and structural fuse are intended to yield at approximately the same load, is demonstrated to be a well-controlled seismic-resisting system, with greatly reduced seismic ductility demand on the structural components. Moreover, seismic energy is well distributed among the targeted yielding components. In contrast, if the footing is restrained from rocking, the structural component ductility demand is significantly greater than that compared to its demand when the foundation is allowed to rock. In essence, the foundation rocking dominated model demonstrates its ability to protect the superstructure from seismic demands. In contrast, when the rocking foundation capacity is more than twice that of the structural fuse, rotations at the foundations are reduced significantly, at the price of much larger demands to the superstructure. [ABSTRACT FROM AUTHOR]

The paper deals with the punching shear behavior and the capacity of interior steel fiber-reinforced concrete (SFRC) slab-column connections. In the experimental study, the effect of the amount of fibers on the punching shear resistance and cracking behavior of slabs was investigated on a total of 12 small-scale flat slabs of varying dimensions. The results show a significant increase in the punching shear capacity, reduction of the average crack widths, and improved integrity of the SFRC slab-column connections in the postcracking stage in comparison with conventional reinforced concrete slabs. A new semiempirical, fracture-mechanics-based formula for estimation of the punching shear resistance of the interior SFRC slab-column connections is also presented in the paper. Its accuracy was verified through the comparison of the test results provided by the authors with those of other researchers, as well as with some already published formulas. The obtained results show that the proposed formula provides a higher prediction accuracy of the punching shear capacity of the SFRC slab-column connections in comparison with the existing prediction formulas. [ABSTRACT FROM AUTHOR]

This paper presents a sensitivity-based damage identification of a three-dimensional truss tower tested in the laboratory. A finite-element model is updated by modal parameters obtained from ambient vibration measurements. The paper focuses on details of modeling and model updating. To get a realistic model, it was necessary to include eccentric connections, bending stiffness in truss members, and foundation flexibility. For model updating, a number of mathematical techniques are combined in a consistent way, including regularization of the nonlinear updating problem and its linearization. Considering all these details correctly, damage in the truss has been successfully identified. However, it is also demonstrated how neglecting some of these algorithmic details can lead to incorrect results. It is also shown how static condensation can lead to a model that is valid for the undamaged case but cannot adequately represent the damaged case. [ABSTRACT FROM AUTHOR]

Most of the existing mechanical models for shear strength and strain calculation of beam–column joints do not explicitly account for bond conditions of the longitudinal reinforcement of the connected members that are anchored inside the joint region. When considered, bond is accounted for through empirical parameters. In this paper, an analytical method for the definition of the strain distribution along the anchorage of the column longitudinal reinforcement inside a bridge monolithic connection is proposed. The anchorage capacity of the main column reinforcement is considered to be affected by two independent mechanisms. The capacity of the first mechanism depends on the average bond stress along the elastic part of the anchorage that is calculated by a mathematical solution without taking into account the beneficial effect of the transverse reinforcement. The capacity of the second mechanism depends on the coefficient of friction arising between main column bars and transverse reinforcement that encloses and restrains the anchorage. The coefficient of friction is empirically set in relation to the position of the transverse bar; either along the elastic part of the anchorage or in the part where yielding penetrates inside the joint. A parametric evaluation of the main design parameters affecting the anchorage capacity is conducted next. The proposed model is finally used in calculating the joint shear response of selected bridge connection specimens for which reported data of strain distribution along anchorages exist. The calculated values correlate successfully with the associated experimental data. [ABSTRACT FROM AUTHOR]

Depending on the relevant material properties, failure of grouted anchor anchorage to concrete can result from pullout of concrete cones, debonding at either anchor-grout or grout-concrete interface, fracture of anchor, and combination of some of these failure modes. The intention of the present study is to present an analytical method for analyzing the concrete cone failure during the process of interfacial debonding by using deformation compatibility conditions at the anchor-grout and grout-concrete interfaces. The tensile stress in the anchor and interfacial stresses at the two interfaces are formulated at different loading stages. It is assumed that interfacial debonding modeled as an interfacial shear crack only appears at the anchor-grout interface and is initiated from the loaded end. The concrete cone and interfacial debonding failures are analyzed according to the sizes and material properties of the anchorage. Three different failure modes are considered, including concrete cone failure at the unloaded end without interfacial debonding, interfacial debonding plus concrete cone failure at the same height as the interfacial shear crack tip, and interfacial debonding plus concrete cone failure at the unloaded end. In each case, the load for the initiation of the concrete cone failure, and the cone angle are determined analytically. Subsequently, material and structural parameters are adopted to study their influences on the failure modes and calculated results. It is found that if the embedment length is relatively long, the concrete cone failure occurs within a local scope. If the concrete diameter is large enough, the failure mode is the interfacial debonding without concrete cone failure. The conclusions provide useful references for engineering practice such as designing grouted anchor anchorage to concrete in light of different needs and failure modes. [ABSTRACT FROM AUTHOR]

In ductile braced frames, column seismic demands depend on the strength of ductile elements and yielding patterns that occur during earthquake loading. Column demands were investigated in buckling restrained braced frames (BRBFs), special concentrically braced frames (SCBFs), and eccentrically braced frames (EBFs) with different heights (3, 9, and 18 story) and strength levels using nonlinear time history analysis. For columns at the base of 9- and 18-story BRBFs and EBFs, axial demands observed from the analyses were 55–70% of demands commonly used in design, indicating potential cost savings on columns, anchor rods, base plates, and foundations in tall buildings; however, in low-rise SCBFs with braces in the 2-story X-configuration, column axial demands were up to 100% greater than those commonly used in design because of force redistribution that occurs after brace buckling. Column rotations in all frames were less than 0.03 rad. These rotation demands are lower than rotation capacities that have been demonstrated in other work. [ABSTRACT FROM AUTHOR]

Soil-structure interaction may play a major role in the seismic response of a bridge structure. Specifically, soil layers of low stiffness and strength may result in permanent displacement of the abutments and foundations, thus imposing important kinematic conditions to the bridge structure. A study to illustrate such phenomena is undertaken based on three-dimensional nonlinear dynamic finite-element (FE) modeling and analysis (for a specific bridge configuration under a given seismic excitation). A bridge-foundation-ground model is developed based on the structural configuration and local soil conditions of the Humboldt Bay Middle Channel Bridge. The FE model and nonlinear solution strategy are built in the open-source software platform OpenSees of the Pacific Earthquake Engineering Research Center. Based on the simulation results, the overall system seismic response behavior is examined, as well as local deformations/stresses at selected critical locations. It is shown that permanent ground deformation may induce settlement and longitudinal/transversal displacements of the abutments and deep foundations. The relatively massive approach ramps may also contribute to this simulated damage condition, which imposes large stresses on the bridge foundations, supporting piers, and superstructure. [ABSTRACT FROM AUTHOR]

A performance-based design methodology is aimed at controlling the structural damage based on precise estimations of the seismic response of the whole building–foundation system. This work presents a simplified procedure for practical damage analysis of structures considering the soil–structure interaction effects, with potential application to performance-based design of new buildings as well as to performance-based evaluation of existing buildings. A damage model based on maximum displacement and dissipated energy under monotonic loading is proposed, with the effects of cyclic load reversals being estimated by using a modified Park–Ang index. To simplify the consideration of the soil–structure interaction effects, an equivalent fixed-base oscillator with the same yield strength and energy dissipation capacity as the actual flexible-base structure is applied. Selected numerical results are presented in terms of dimensionless parameters for their general application, using a set of appropriate earthquake motions for ensuring generality of conclusions. The significance of soil–structure interaction in the structural performance is elucidated and the adequacy of the approach proposed is examined. [ABSTRACT FROM AUTHOR]

The present paper addresses a foundation problem in seismic resistant buildings braced by structural walls. In particular, the box-type foundation for an internal shear wall is investigated. This kind of foundation can be an alternative solution for direct foundations. It solves the problem where oversized ordinary raft foundations are needed. In fact, the box foundation gathers the gravity loads resting on the peripheral walls, so that the global soil reaction reduces its eccentricity. In most cases the elements constituting the box structure, such as peripheral walls, raft, and ground floors, are already part of any actual building; they only need a proper seismic design, which is herein proposed. A simplified theoretical approach is presented to allow a correct proportioning and design of each structural element, such as reinforcing ribs and panels constituting the box. Moreover, the solution given by this analytical procedure can be useful to check the reliability of any numerical analysis. Since the analytical approach is based on equilibrium conditions, it can be easily extended to the ultimate loading state. A practical application is finally presented for a seven floor building where both the shear walls and the box foundation are subjected to a severe seismic action. [ABSTRACT FROM AUTHOR]

Concrete anchoring systems are commonly used in blast resistant wall systems. These anchoring systems are often subjected to large tensile forces in a short time during an external blast event. Previous research has been conducted on anchoring systems to evaluate their response to cyclic and “shock” loads; however, the ultimate capacities of these systems were not determined, and tests were conducted at relatively slow loading rates. In this paper, testing has been performed to determine the ultimate capacity of various expansion anchors at high loading rates, which is characteristic of most blast events. Ultimately, concrete expansion anchors perform differently at high loading rates and some show improved ultimate performance. This paper will present the experimental findings and provide recommendations for anchor design under blast loads. [ABSTRACT FROM AUTHOR]

A methodology is developed in this paper to evaluate the first transition foundation stiffness for columns subjected to end concentrated loads, on a Winkler foundation, where the buckling mode shape changes. The method is based on earlier work of Naidu and Rao to predict the fundamental frequency of beam columns, wherein it was assumed that the mode shapes of vibration, initially loaded vibration, and buckling are the same. Very good predictions for the fundamental frequency of beam columns were obtained when the assumption of the same mode shapes is satisfied. In the case of the buckling of columns on Winkler foundations, at a certain value of the foundation stiffness the buckling mode shape totally changes while the mode shapes of vibration and initially loaded vibration remain the same. This led to a very large error in the predicted fundamental frequency parameter of the beam columns. This aspect is used in the present paper to evaluate the first transition foundation modulus of columns of Winkler foundations. The first transition foundation stiffness for simply supported columns on Winkler foundations, for which an exact solution is available, is obtained through the proposed methodology, and is found to be very accurate when compared to the literature values. The methodology is further used to find the first transition foundation modulus of clamped columns for which no solution is readily available. Very interesting and unexpected results were obtained for the transition stiffness and the corresponding mode shapes at transition for clamped columns of Winkler foundations. [ABSTRACT FROM AUTHOR]

Presents an investigation of the performance of 2X dimension lumber sill plate connections and suggests possible strategies for their improved seismic performance. Splitting of wood frame construction; City of Los Angeles' restriction of 2X dimension lumber in sill plates; Use of metal reinforcing straps to increase deformation capability.

Twenty-seven wall-splice specimens reinforced with number (No.) 15 (0.6 in.) deformed bars were tested to evaluate the effect of transverse bar spacing on the tensile resistance of the lap-spliced reinforcement. All specimens were blocks wide and 13 courses tall and were constructed in running bond with all cells fully grouted. In all cases, the lapped bars were located within a single block cell and were either spaced 0, 25, or 50 mm (0, 1, or 2 in.) apart. It was determined that the calculated tensile resistance of the reinforcement was greater for bars that were in contact and furthermore, is insensitive to the magnitude of the transverse spacing provided in the case of noncontact lap splices. It would appear that both the American and Canadian provisions are appropriate for both contact and noncontact lapped bars given the resulting levels of conservatism. [ABSTRACT FROM AUTHOR]

The authors discuss research on the cyclic response of reinforced concrete walls with different anchorage details. They reference the study "Cyclic Response of Reinforced Concrete Walls With Different Anchorage Details: Experimental Investigation" by Sriram Aaleti and colleagues published in the journal in 2014. Topics discussed include the loading history for applying lateral load to wall specimen of a test, horizontal sliding shear cracks and the mechanism of instability of wall specimens.

The article discusses the research on a nonconstrained flagpole design. The engineer's method is compared to a similar method of structural engineering. Topics examined include three-dimensional effects, design methods, and computer programs. The engineer offers a conclusion to the research and comments on the Outdoor Advertising Association of America, lateral bearing capacity, and designing by codes.