Lateral Load Response Research Articles

Experimental and numerical study on the static lateral performance of monopile and hybrid pile foundation

Considering the limitations of conventional monopiles in supporting the new generation of offshore wind turbines (OWTs), the idea of hybrid pile foundation has been proposed and studied in recent years. In this paper, static lateral load tests are conducted on model piles and hybrid pile foundations in saturated sand. The influence of pile stiffness and hybrid foundation type on the lateral response is analyzed. Three-dimensional (3D) coupled discrete continuum modelling is further performed to reveal the interaction mechanism between different pile foundations and the surrounding soil. Experimental results indicate that the lateral capacity of the hybrid pile foundation can be notably improved compared with that of the monopile foundation, especially at small pile displacement. And the lateral load response of the hybrid pile foundation is comparable to that of the monopile at the ultimate limit state. From a numerical perspective, the load transfer mechanism of different pile foundations is studied by analyzing the displacement pattern of pile and soil foundation and the distribution trend of horizontal soil stress. It reveals that the existence of footing and bucket foundation could improve the efficiency of soil resistance mobilization at shallow depth. The experimental and numerical study is expected to provide some new perspectives on the understanding of the lateral bearing characteristics of hybrid pile foundations.

Field test research and design of a new heliostat support structure in coarse gravel

A solar power tower plant includes a solar tower and tens of thousands of heliostats, with the latter accounting for 40–50% of the total cost. To reduce heliostat costs, a new type of heliostat support structure (HSS) is proposed, consisting of a prestressed high-strength concrete pipe pile and cast-in-place concrete. With the performance and applicability of this structure unknown, full-scale field load testing of the proposed HSS on coarse gravel, subjected to lateral loads or torsion–lateral combined loads, was conducted. The results indicated that lateral load amplifies the rotation under torque and the proposed HSS for mirror arrays can provide sufficient rigidity to limit structural deformations within tolerable values under severe wind loading. Together with three-dimensional modelling, the performance of the proposed HSS was thoroughly investigated to facilitate the development of modified prediction methods for its lateral and torsional load responses. A detailed design procedure is proposed for the new structure, considering foundation deformations, bearing capacity and survival requirements. This study proved that the proposed HSS can improve the economic performance of solar power tower plants.

Finite-Element Analysis of the Lateral Load Response of Monopiles in Layered Sand

Most of the existing design methods for laterally loaded monopiles were developed for uniform soil profiles. The application of such design methods in cases involving layered sand profiles can lead to incorrect capacity estimations. In order to investigate the impact of the soil layering on the response of monopiles to lateral loads and to develop a design method that is applicable to layered soil profiles, a series of three-dimensional (3D) finite-element (FE) analyses were performed on laterally loaded monopiles embedded in layered sand profiles using an advanced two-surface-plasticity constitutive model. The analyses take into consideration a wide range of pile geometries (pile diameter, slenderness ratio, and wall thickness), load eccentricities, sand types and relative densities, and layered soil profiles. The study examines the change of the lateral capacity of a monopile in a two-layer sand profile as the top layer thickness varies, as well as the impact of the presence of a thin loose-sand layer in a dense-sand profile on the pile lateral capacity. Based on the results of these analyses, a set of design equations is proposed to estimate the lateral capacity and load-rotation response of monopiles in layered sand profiles. The proposed method accounts for the 3D pile–soil interaction and provides estimates of the lateral capacity that are in close agreement with those obtained from the 3D FE analyses.

Madras Terrace Construction: Seismic Upgrade of a Historic Composite Floor Slab System

ABSTRACT Traditional construction techniques get replaced with newer systems over a period of time owing to multiple factors including limitations associated with the system in terms of lateral strength and stiffness. However, those construction techniques, which are sustainable and energy efficient can be revived using modern technologies with minimalist interventions. In this regard, the characterization of the lateral load response of a century-old traditional timber-supported composite brick-floor system in southern India called Madras Terrace floor is carried out. A full-scale experimental model is built and the specimen is upgraded using post-installed anchors to ensure integral action between different components without any changes to materials in the as-built configuration. Experimental characterization using monotonic tests is carried out in the as-built and upgraded configurations and the results are validated using numerical analyses. Results demonstrate a significant increase in strength capacity and a ductile post-peak behaviour for the diaphragm in the upgraded configuration. An analytical model, which closely predicts the system response in the upgraded configuration is formulated and a demonstrative case study for the component level seismic assessment of a typical Madras Terrace floor slab as a sub-system of an existing unreinforced masonry building is carried out.

Lateral load behavior of RC buildings exposed to fire: case study

ABSTRACT Fire damaged reinforced concrete buildings are often made usable by performing non-structural and cosmetic repairs. These types of repairs do not guarantee the safety of such buildings under the effect of future lateral loads, such as earthquakes. In this paper, an evaluation of the lateral load response of an RC fire damaged – building in Libya is presented. The building was used as a courtyard for the public and the fire visibly damaged some of its columns and beams. Material tests were conducted in situ and in the laboratory to evaluate the material strength of the building after the fire. Then, lateral load carrying capacity of the building before and after the fire was evaluated. Analysis results show that up to one-hour fire duration the building does not lose a considerable amount of its lateral strength; however, at about two and half hours fire duration, it lost about 30 percent of its lateral load carrying capacity. Lastly, analytically predicted residual strength material properties are in good agreement with material test results.

Lateral load-deformation models for seismic analysis and performance-based design of confined masonry walls

Confined Masonry (CM) has been implemented as an affordable building type in many earthquake-prone regions and continuously gaining popularity all over the world. This is primarily because of the better performance exhibited by these buildings during past earthquakes, even though their design and construction methodology is much simpler, compared to other common housing typologies, like unreinforced masonry buildings and infilled reinforced concrete frame buildings. Though several experimental studies have been carried out on CM walls across the world, the variation associated with material properties, detailing of tie-elements, construction practices, etc., are huge. This makes the formulation of generalized analytical backbone models for CM walls a difficult task for an approximate prediction of their lateral load response. Existing empirical models for the prediction of lateral stiffness, strength, and deformability at different performance levels of CM walls are utilized in the present study to estimate these parameters for seventy-eight CM specimens tested in past studies. Analytical backbone profiles for CM walls are developed using these parameters. The experimentally obtained backbone parameters are compared with those estimated analytically from different empirical models to evaluate their effectiveness. Based on these observations, proposals are made for a generalized analytical backbone model of CM walls that may be used for performance-based seismic analysis and design.

Lateral load response of large-diameter monopiles in sand

Due to the increasing demand for renewable clean energy, there has been rapid growth in the development of offshore wind energy resources in recent years. The majority of offshore wind turbines are founded on single, large-diameter, open-ended pipe piles known as monopiles. The design of these piles is often done using the p–y method, which models the soil simply as non-linear springs placed along the pile length and assumes the pile to behave as a one-dimensional beam. To develop a design method that accounts for three-dimensional pile–soil interaction and that is applicable to general conditions, a series of finite-element (FE) analyses covering a wide range of pile dimensions, wall thicknesses, slenderness ratios, load eccentricities, sand types and sand relative densities were performed using an advanced sand constitutive model. In this paper, a set of equations is proposed that can be used to estimate the critical pile length, Lcrit (the pile length beyond which the pile lateral capacity no longer increases), the lateral capacity, H, and the lateral load–rotation curve for monopiles. The proposed method produces estimates of the lateral capacity of monopiles that are in very close agreement with those from the FE analyses.

Analysis solution of the lateral load response of offshore monopile foundations under asymmetric scour

Because of the directivity of the waves and flow, the scour hole presents an irregular shape, and the scour hole dimensions are different around the pile. In this paper, an asymmetric scour is defined in the calculation of the laterally loaded offshore monopile foundations considering scour. Then, the effective overburden stress and the effective strength of the remaining soil after scour are determined based on the solution of Boussinesq's point load due to the unloading of the scour. An analysis p-y method is developed under the condition of the asymmetric scour based on the p-y curve proposed by Matlock for soft clay and the p-y curve proposed by Reese for sand, respectively. The effect of the scour depth, scour width and scour slope angle on both sides of the piles on the lateral loaded piles are determined in both soft clay and sand. Finally, according to the results of the parameter studies, a simplified method applicable to small-diameter flexible piles is developed based on the pile head deflection before scour, scour depth, loading height and pile diameter to predict the lateral loaded pile head deflection after scour in soft clay and sand, respectively.

Inelastic Responses and Finite Element Predictions of Fiber Cementitious Composite and Concrete Columns.

In this research, reinforced concrete (RC) and strain-hardening cementitious composite (SHCC) columns subjected to lateral loads combined with a constant load were investigated, both by experiments and predictions, with two distributed inelastic finite element models established by the stiffness and flexibility formulations. SHCC applied in the column plastic hinge region could not only enhance the lateral load and displacement capacities of columns but also offer effective advantages in the control of bending and shear cracks induced by multiple microcracks, the prevention of the spalling of cover concrete, and the resistance to buckling of steel bars. With the layered cross-sectional approach using constitutive laws of SHCC considering a proposed model of the post-cracked high-ductile tensile characteristics, as well as concrete and reinforcing steel bars, an inelastic beam-column finite element model was presented with a distributed flexibility formulation. In comparison with experiments concerning the RC and reinforced strain-hardening cementitious composite (R-SHCC) columns, the current flexibility method showed relatively accurate estimations in the lateral load and displacement responses of column systems as well as in localized nonlinear responses of cross-section as estimated in axial strains of longitudinal reinforcing steel bars. In comparison with the stiffness method, the current flexibility method gave more accurate solutions at both element and structural levels, as manifested in the experiments and analysis solutions.

Development of a Novel V-D Strut Model for Seismic Analysis of Confined Masonry Buildings

Confined masonry (CM) offers an affordable and seismically safe building typology, which is already a widespread construction technique in several seismically-prone countries, and is currently evolving as a popular construction technique in many other countries. This building system has shown phenomenal performance in the past seismic events; however, its engineering behavior has not been established sufficiently due to significant variation in materials used and lack of research in understanding the complex composite behavior under different loading conditions. Significant gaps exist in research, especially in reliable methods of seismic analysis and design; consequently, modeling a CM building still fails to be a persuasive choice. The primary objective of this study is to develop a simple generalized numerical model that can reliably predict the nonlinear behavior of CM walls under seismic loads. A comparative numerical study was first carried out to assess a suitable model for CM walls based on the realistic simulation of axial forces in tie-columns and tie-beam deflection under the action of gravity loads. A new macro-model “V-D strut model” was finally developed for the analysis of CM walls under the action of both gravity and seismic loads. Due care was taken to simulate not only the initial stiffness and strength of CM walls but also to characterize their failure modes in a simplified way using an effective shear strength of masonry estimated by carrying out a parametric finite element study. The effectiveness of the V-D strut model was validated by an accurate prediction of the lateral load response of several CM walls tested previously.

Experimental Investigation of Base Conditions Affecting Seismic Performance of Mass Plywood Panel Shear Walls

AbstractMass plywood panels (MPP) are a new engineered wood material produced by Freres Lumber Company, Inc. in Lyons, Oregon. This paper presents a study of the lateral-load response of MPP walls ...

Experimental behaviour of prefabricated pile-cap foundation under seismic loading

Precast building has attracted more and more interest of both researchers and engineers due to fast constructional speed and lower labour cost. In the past, the precast structure was generally used in the superstructure, such as load bearing frame, however, it is seldom applied in the substructure such as foundation. The paper thus proposed a type of pile-cap connection to fabricate the foundation of a substation. A series of tests on the prefabricated pile-cap connection using these connections were carried out under seismic loading. The failure mode and lateral load versus lateral displacement response of the tested specimens were experimentally investigated. The seismic behaviour of the precast foundation was compared with the behaviour of the corresponding cast-in-place foundation.

Generalized dynamic analysis of structural single rocking walls (SRWs)

SummaryThe investigation of structural single rocking walls (SRWs) continues to gain interest as they produce self‐centering lateral load responses with reduced structural damage. The simple rocking model with modifications has been shown to capture these responses accurately if the SRW and its underlying base are infinitely rigid. This paper advances previous rocking models by accounting for (1) the inelastic actions at or near the base of the SRW and (2) the flexural responses within the wall. Included in the proposed advancements are hysteretic and inherent viscous damping associated with these two deformation components so that the total dynamic responses of SRWs can be captured with good accuracy. A system of nonlinear equations of motion is developed, in which the rocking base is discretized into fibers using a zero‐length element to locate the associated compressive deformations and damage. The flexural deformations of the rocking body are captured using an elastic term, while the impact events are modeled using impulse‐momentum equations. Comparisons with experiments of structural precast concrete and masonry SRWs show that the proposed approach accurately estimates the dynamic responses of different SRWs with and without unbonded posttensioning, for various dynamic excitations and degrees of hysteretic action. Using the proposed approach, a numerical investigation employs different configurations of structural SRWs to quantify the various sources of energy loss, including hysteretic action and impact damping, during various horizontal ground motions.

Axial and lateral resistance coupling in the analysis of large-diameter drilled shafts

Pier foundations subjected to lateral loads are commonly designed using beam on nonlinear Winkler foundation (BNWF) models. This form of soil-structure interaction (SSI) modeling typically involves load transfer between structural members (e.g., drilled shafts) and surrounding soil via nonlinear soil resistance springs, which are distributed along the centerline of beam-column elements. Physically, soil resistance develops at the shaft-soil interface, and special considerations may be warranted regarding coupling between axial and lateral resistance when modeling large-diameter drilled shafts. Presented in this paper are side (t-z) and lateral (p-y) soil-resistance relationships for Florida limestone, obtained from centrifuge tests, and moment-rotation springs associated with coupling of axial and lateral resistances of laterally loaded drilled shafts. Using the coupled approach, BNWF models are developed that: 1) Capture physically measured lateral load responses of shafts founded in a range of soil/rock types; and, 2) Are suitable for large-diameter shafts at variable embedment lengths. This study highlights the need for such analyses in cases when relatively stiff soil/rock materials exist at shallow depths and/or when shafts undergo significant rotations. Use of coupled analysis is found to reduce computed maximum values of shaft bending moment and deflection up to 12% and 19%, respectively, compared to uncoupled analysis.

Cyclic Lateral Load Response of Full-Scale Flexure-Dominated Shear Wall

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Confined and unreinforced masonry structures in seismic areas: Validation of macro models and cost analysis

Modern structural design requires consideration of sustainability parts from a life cycle perception, but also the initial design phase in which seismic actions have a substantial influence on the design of the structure. In recent times, the seismic assessment of masonry buildings by means of macro-element modeling methodologies has become popular, by application of performance-based evaluation techniques using nonlinear lateral load procedures (Pushover). This study addresses the endorsement of these methodologies by referring to two full-scale brick masonry structures subjected to a lateral loading conditions. The lateral load response of tested unreinforced masonry (URM) and confined masonry (CM) structures is compared with the response of the numerical models. The considered numerical models have good agreement for satisfactorily predicting the response of the experimental test and hence are capable of being used in a performance-based evaluation. Then, pointing to the characteristic housing of northern Pakistan and its typical design with a reinforced concrete (RC) building, the validated numerical models are used to estimate the hazard-resistant potentials of the URM and CM options for one, two and three story options, particularly in relation with maximum lateral load capacity. The load deformation response of both the typologies was also compared for the mentioned three story levels. It was observed that by confining the masonry its ductility capacity increases considerably, hence making it more suitable to be used in earthquake prone regions. Masonry structures are also compared regarding the construction costs compared to the RC typology. With regard to the dwellings studied, the projected lateral load behavior for masonry structures indicate the ability to withstand lateral loads adequately. These structures also allow a significant reduction in costs (up to 28%) compared to RC, hence appearing as challenging alternatives.

Seismic performance of an idealized steel-plate composite (SC) modular structure subjected to accident thermal loading

This paper presents a numerical study to estimate the lateral load performance of an idealized steel-plate composite (SC) modular structure subjected to accident thermal loading. Finite element analysis (FEA) method was employed to perform the structural pushover analysis of the idealized SC modular structure that resembled a generic containment internal structure including the steam generator, pressurizer compartments, and reactor cavity walls. The paper will elaborate on the findings from the study including the nonlinear behavior of the SC modular structures subjected to seismic and accident thermal loading, while incorporating four different modeling techniques (including three nonlinear and one linear models) with different complexity levels. Nonlinear analysis techniques employed in the study provided similar responses for the lateral load response and behavior of the idealized SC modular structure. Nonlinear analysis results indicated that the temperature gradient due to heating caused thermal cracking in the concrete infill and reduced the lateral stiffness of the structure. The severity of the lateral stiffness reduction depended on the applied surface temperature amplitude. A marginal reduction (about 10%) in the lateral strength of the structure was observed for the elevated temperature cases. The peak structure strength for the accident thermal cases were reached at larger drift ratios in comparison to the ambient case. The results from the nonlinear analysis have been used to verify a linear elastic analysis (LEFE) approach to accurately establish the lateral stiffness of the SC structures subjected to seismic and thermal (operating or accident thermal) conditions. The LEFE approach was implemented as a tool for practicing engineers in industry to obtain accurate design demands. The study also investigated the influence of stress and deformations in the steel faceplates and tie bars induced by concrete casting pressures on the lateral performance of the SC modular structure.

Nonlinear Finite Element Modeling of Reinforced Concrete Walls with Varying Aspect Ratios

ABSTRACT A relatively simple finite element modeling approach – named the Fixed-Strut-Angle Finite Element (FSAFE) Model – is presented in this paper for simulating the hysteretic lateral load behavior of reinforced concrete structural walls with varying levels of flexural and shear deformation contributions on wall response. The behavioral characteristics of the constitutive panel elements incorporated in the model formulation are based on a fixed-crack-angle modeling methodology that also incorporates simple behavioral models for shear–aggregate interlock in concrete and dowel action on reinforcing bars, constituting the shear stress transfer mechanisms across the cracks. Model response predictions are compared with experimentally measured responses of selected wall specimens with varying geometry and reinforcement characteristics; including relatively slender (aspect ratio of 3.0) flexure-controlled walls with rectangular and T-shaped cross-sections, medium-rise walls (aspect ratios of 1.5 and 2.0) with coupled shear-flexural responses, and squat walls (shear span-to-depth ratios of 0.44 and 1.0) with shear-dominant responses. The FSAFE model demonstrates a reasonable level of accuracy in predicting the nonlinear hysteretic response of the wall specimens investigated. Accurate predictions are obtained for the experimentally measured lateral load vs. displacement response characteristics of the walls, including their lateral load capacity, sftiffness, and ductility, as well as their hysteretic response attributes. The model also provides reasonably accurate estimates of the relative contributions of nonlinear flexural and shear deformations to wall lateral displacements, as well as local deformation characteristics including the spreading of nonlinear flexural and shear deformations along wall height, the distribution of transverse normal strains along wall height, and the longitudinal strain profiles across the wall cross-section. It is identified that consideration of instability related wall failures, including buckling of reinforcement and out-of-plane instability of the wall boundary region, is necessary for further improvement of model accuracy.

Field and numerical analysis on effect of axial load on the lateral response of a pile

Purpose Piles often carry combination of axial and lateral. Currently, piles are designed separately for axial and lateral load. In the literature, few information is available on the influence of axial load on lateral behaviour of the pile. This paper aims to present the results of load deformation of a pile under pure lateral load and combined axial and lateral load. Design/methodology/approach The field load tests were carried out on four different pile diameters at two different bridge sites. Moreover, the paper addresses the numerical simulation of filed load test carried out on the pile under the combination of axial and horizontal load. Findings After field load tests and numerical simulation, it was found that the vertical load had a remarkable effect on the lateral load response of a pile. The lateral deflection of the pile was decreased about 25% under the effect of vertical load. In addition to this, the results from field and numerical simulation are quite comparable. Originality/value Typical field load tests were simulated numerically. This research adds a value in the areas of pile foundation subjected to vertical and lateral load particularly for structure such as transmission line tower and jetty.

Enhancing Lateral Load Performance of Traditional Timber Wall (Dhajji-Dewari) by Strengthening of joints

Traditional timber structures, known as Dhajji Dewari, are mostly found in the Northern areas of Pakistan and Kashmir. Very limited research is available to validate the seismic performance of Dhajji Dewari construction. It has experimentally been proved that Dhajji construction is suitable for earthquake resistance and the prominent features include its affordability, superficial ability to tolerate earthquakes and the fact that it is within the technical means of local, less skilled personnel for house building. This paper presents experimental work conducted on typical Dhajji Dewari wall found in northern areas of Pakistan and Kashmir, to evaluate the in-plane lateral load response by strengthening of critical joints. The experimental work includes in-plane monotonic testing on four reduced scale walls, one wall was used without any strengthening (Conventional wall) other walls were strengthened by different strengthening techniques (bamboos, metal strips, and metal gusset plates). Test results show that the connection functionality, particularly at the joint of vertical posts and bottom plates, controls the overall performance of the wall. Strengthening of these joints not only enhances the lateral load carrying capacity of the wall, but also significantly augment the energy dissipation capacity of the system. Further, based on cost benefit analysis it is concluded that wall strengthened with metal strips give the best reinforcement of Dhajji walls keeping in view the additional cost of strengthening and load deformation behavior of wall.