Static Horizontal Loads Research Articles

Research horizontally loaded pyramidal piles with compacted bottom and their calculation

The results of experimental and theoretical research in work features of a rammed pyramidal pile with compacted bottom for horizontal load in clayey soils are presented. The experimental cast-in situ pyramidal piles with compacted bottom were made at 2 experimental sites, composed of clayey soils. Static horizontal load tests were carried out. At each stage of loading, horizontal displacements were measured at the load application level and at a height of one meter from the top edge of the pile. The “horizontal load - pile head displacement” dependencies were obtained. It was found that the rotation of the pile in the soil occurs without bending, i.e. according to a rigid scheme, and also that compacted bottom prevents horizontal displacement of the pile bottom. Based on the analysis of the results of static tests of piles, a design scheme has been created, in which the pile is considered as a rigid rod buried in a multilayer linearly deformable base with a point of zero displacements at the lower end of the pile. In accordance with the design scheme, an analytical method for calculating a pyramidal pile with compacted bottom for horizontal load and bending moment has been developed. The calculation method allows to determine the horizontal displacement of the pile head in any section along the depth, the angle of rotation of the pile, bending moment and shear force along the length of the pile.

Mr Impact Dipping Pyramidal-Prismatic Piles and their Resistance to Pressure and Horizontal Load

The results of experiments carried out in the field with the use of large-scale models of reinforced concrete driven pyramidal - prismatic piles with different lengths of the pyramidal part are presented. The impact capacity of piles were evaluated of their bearing capacity to the action of indentation and horizontal static loads. It has been established that the driving of pyramidal-prismatic piles is accompanied by both large (by 1.10–1.60 times) and lower (by 8.0–37.0 %) energy consumption for their driving in comparison with conventional pris-matic and pyramidal piles. It was also revealed that under the action of a vertical indentation load, the bearing capacity of the pyramidal-prismatic piles is 1.09–1.48 times, and under the action of a horizontal static load, it is 1.17–1.80 times higher than that of a prismatic pile. It has been established that with an increase in the length of the pyramidal part of the test piles, there is an increase in their bearing capacity by 1.12–1.34 times. Formulas are proposed for determining the bearing capacity of pyramidal-prismatic piles. The research results serve as the basis for the development of recommendations for the calculation and design of pyramidal-prismatic piles.

Tilting plane tests for the ultimate shear capacity evaluation of perforated dry joint masonry panels. Part I: Experimental tests

The aim of this work is to present a simple and practical experimental technique for the estimation of the ultimate shear capacity of perforated in-plane loaded dry joint masonry panels. The test is carried out by using a tilting table; in-scale models of several different perforated walls are assembled and positioned on the tilting table. The table is progressively tilted in quasi-static conditions, in order to reproduce the action of a static horizontal load proportional to masses. As a result, the model collapses for a given tilting angle, which represents the ultimate destabilizing horizontal action. The experimental setup was applied to a series of seven different masonry panels, conceived by different University teams from different countries in the context of a student competition proposed in the occasion of the 10th international Masonry Conference (10th IMC), held at the Technical University of Milan from 9th to 11th July 2018. The aim was to design a running bond shear panel with established height over length ratio, a minimum perforation ratio equal to 30% of the area and clay bricks with given dimensions disposed in either stack or running bond. The winning team was that obtaining the largest inclination angle of the tilting plane activating the collapse of the structure. Three replicates of the same experimental test were repeated in the lab of the Technical University of Milan to reduce experimental scatter of the results. In this paper we present and discuss the outcome of the experimentations carried out, in view of analyzing such results with sophisticated limit analysis approaches in the second part of the paper. The test requires simple and inexpensive instrumentation and can be adopted for a reliable prediction of the behavior of perforated shear walls in-plane loaded, assembled with dry joint bricks and horizontally loaded.

Experimental investigation of inclined RC pile groups under horizontal static and impact loads

In engineering practice, inclined pile groups have been widely used for resisting lateral loads owing to their great lateral stiffness. This paper investigates the structural performance of inclined reinforced concrete (RC) pile groups subjected to horizontal static and impact loads through experimental studies. Using the horizontal impact facilities, a total of twelve 2 × 1 inclined RC pile groups were tested under horizontal static or low-velocity impact loads. The twelve test specimens include three types of pile groups including two types of inclined pile group with inclination angle of 9° and 18° and one type of double vertical pile group with inclination angle of 0°. For each type of pile group, four specimens with identical geometric dimension are prepared and tested under horizontal static load and three different level of horizontal impact loads initiated from different impact velocities, respectively. It can be found that, the variation of inclination angle significantly affects the static and dynamic behaviour of pile groups. Two, three and four plastic hinges are developed at the static or impact loading for the RC pile groups with inclination of 18°, 9° and 0°, respectively. With the increase of inclination angle from 0° to18°, the failure modes of the RC pile groups under impact transits from ductile to brittle type.

Static and dynamic size optimization of nonlinear continuous structure based on fully stressed design

In order to realize the fully stressed criterion, that is, the stress of the nonlinear engineering structure is uniform along the height direction under the action of wind load or ground motion, the section size of the continuous structure is optimized based on mechanical analysis. The engineering structure is simplified as a continuous cantilever with variable cross-section, and its material constitution is nonlinear. The wind load and ground motion are represented by three kinds of horizontal static loads: uniform load, inverted triangle load, and inertia force related load. In order to meet the needs of different projects, hollow circular section and box section are designed, respectively. By establishing different expressions of section moment, the optimal section size distribution is solved. Then the optimal stiffness distribution of nonlinear structure is proposed. The correctness of the theory is verified by the finite element method. The results are suitable for the elastic and elastic-plastic stages of the structure, and are effective for both static loads and dynamic actions. The optimal section size distribution and structural shape are different under different loads. Finally, a practical design example is shown.

A numerical analysis on the effect of pile head connections on piled raft foundation subjected to vertical and static horizontal load

A numerical analysis has been performed on the piled raft subjected to uniform vertical load and static horizontal load on piled raft foundation. The applied horizontal load was about 6%, 8%, 9% and 12% of vertical applied load. A constant spacing and uniform length to diameter ratio of 3x3 pile group of piled raft models have been adopted in the present study. These models were validated first and then analysis of adopted finite element models resting on cohesion less soil has been carried out. The rigid and hinged pile head connectivity with raft has been considered. The effect of raft-soil stiffness has been adopted in the study. Normalized axial forces, normalized bending moment and normalized lateral displacement of piles throughout its length have been studied. In the case of rigidly connected piles of piled raft, the maximum positive moment of the piles was reached near the top and the maximum negative moment was found at the middle one-third section of the pile depth. The bending moment at the top was zero in case of hinged connected piles of piled raft and the highest positive moment was reached at one-third portion of pile depth from the top. Furthermore, at the bottom end of the pile it decreased to about zero. The influence of increment of horizontal load on vertically loaded piled raft has been examined too. With an increase in horizontal load from 6% to 12% of applied vertical load, the piled raft with rigid connected piles displaced 8 percent −20 percent lower than the piled raft with hinged connected piles at a constant value of relative raft rigidity.

Distributed monitoring of deformation of PCC pile under horizontal load using OFDR technology

To study the horizontal bearing behavior of cast-in-place concrete (PCC) pipes, a horizontal static load model test is conducted based on the optical frequency domain reflectometry (OFDR) technology. The deformation distribution in the pile is studied. Results show that the pile moment increases with the horizontal load, whereas the position of the maximum point of moment is roughly unchanged. Moreover, the calculated and measured values of horizontal displacement at the pile top are compared; results show that the values are in agreement, which demonstrates that the deformation of a PCC pile can be successfully measured using the OFDR technology.

Experimental investigation of slender RC columns under horizontal static and impact loads

This paper reports an experimental investigation on the behaviour of slender reinforced concrete (RC) columns under horizontal static or impact loading. Fourteen square RC columns were tested under horizontal impact loading by using a modern horizontal impact facility. These specimens were subjected to the same design impact velocity of 0.8 m/s. The effects of three main parameters, namely the specimen slenderness ratio, the longitudinal reinforcement ratio, and the axial compression ratio, were considered. Based on the impact test results, the descriptions of failure mode, crack pattern, time histories of impact force, deflection, and strain are illustrated. On the other hand, tests on three additional RC columns with different cross-section dimensions subjected to horizontal static loading were undertaken for comparison purpose. In the comparisons of the load–displacement relationships for static and impact load cases, the significant divergence can be observed owing to the existence of the inertial force initiated in the dynamic responses. After the completion of the impact test, six impact-damaged specimens were tested under static loading to evaluate their residual resistance and the corresponding behaviour. It is found that the ultimate capacities of damaged specimens could reduce by 7%–14% compared with those of undamaged ones.

Multi-Beams modelling for high-rise buildings subjectedto static horizontal loads

In general, the study of a high-rise building's behaviour when subjected to a horizontal load (wind or earthquake) is carried out through numerical modelling with finite elements method. This paper proposes a new, original approach based on the use of a multi-beams model. By redistributing bending and axial stiffness of horizontal elements (beams and slabs) along vertical elements, it becomes possible to produce a system of differential equations able to represent the structural behaviour of the whole building. In this paper this approach is applied to the study of bending behaviour in a 37-storey building (Torre Pontina, Latina, Italy) with a regular reinforced concrete structure. The load considered is the wind, estimated in accordance with Italian national technical rules and regulations. To simplify the explanation of the approach, the wind load was considered uniform on the height of building with a value equal to the average value of the wind load distribution. The system of differential equations' is assessed numerically, using Matlab, and compared with the obtainable solution from a finite elements model along with the obtainable solutions via classical Euler-Bernoulli beam theory. The comparison carried out demonstrates, in the case study examined, an excellent approximation of structural behaviour.

Experimental observation on laterally loaded pile in unsaturated silty soil

An experimental study was carried out to investigate the effects of soil partial saturation on the behaviour of laterally loaded piles. The proposed study was conducted by means of centrifuge tests at 100g, where a single vertical pile was subjected to a combination of static horizontal load and bending moment. The study was conducted on a silty soil characterized with laboratory testing under saturated and unsaturated conditions. During flight, two different positions of water table were explored. The influence of density was investigated by compacting the sample with two different void ratios. Finally, the effects of a variation of saturation degree on the pile response under loading were studied by raising the water table to the ground surface. Data interpretation allows drawing different considerations on the effects of partial saturation on the behaviour of laterally loaded piles. As expected, compared to saturated soils, partial saturation always leads to a stiffer and resistant response of the system. However, the depth of the maximum bending moment is related to the position of the water table and the bounding effects induced by partial saturation appear to be more important for loose soils.

Structural models for analysis of reinforced concrete frame buildings with masonry infills

Abstract The behavior of single-storey, single-bay reinforced concrete infilled frame with masonry panel subjected to static horizontal load was studied using two structural models: i) equivalent strut model (ESM) and ii) model with two-dimensional finite elements for state stress plane (MEF). In the first model, an equivalent diagonal strut replaces masonry. The axial stiffness of this element is defined by evaluation of the equivalent diagonal width. In the second model, the infilled frame is modeling by two-dimensional finite elements, requiring the simulation of the sliding and separation between the wall surfaces and the reinforced concrete frame. Although equivalent strut models are more attractive for design, the formulas found in the literature to determine equivalent strut width provide very different values. In addition, most of these formulas ignore some parameters that may be important, such as beam flexural stiffness. For this reason, several numerical analysis were be carried out. The models simulated usual geometric and mechanical characteristics observed in reinforced concrete buildings. The results of the two-dimensional finite element modeling (by software ANSYS) were used as reference for the evaluation of the results provided by the equivalent strut model. The comparison of results allowed the assessment of the analytical expressions for evaluation of the equivalent diagonal width. Based on this assessment, a new expression is proposed for buildings with similar characteristics as analyzed in this paper. The results of numerical simulations with MEF models also allowed for an evaluation of stresses and the probable cracking pattern in infill walls.

Collapse behavior of masonry domes under seismic loads: An adaptive NURBS kinematic limit analysis approach

The ultimate limit state behavior of masonry domes under axisymmetric gravity loads is nowadays well known and it has been proved how a generalization of the thrush line method used successfully for arches is quite effective also in this case. However, the behavior of a dome under horizontal loads, which is important in case of seismic action, becomes incredibly hard to tackle and still remains an open issue.The present paper aims at presenting a fast and reliable automatized kinematic limit analysis approach able to accurately predict the actual behavior of masonry domes subjected to horizontal static loads. The model uses a rough discretization of the dome obtained by means of few rigid-infinitely resistant NURBS generated elements, adapting step by step the initial mesh in order to progressively overlap the element edges (where all dissipation is lumped) with the hinges forming the failure mechanism. The adoption of a rough mesh makes the code extremely fast, much more competitive than a standard FE model, allowing at the same time to approximate the actual geometry and load distributions in an extremely accurate way. The utilization of geometries obtained with laser scanner acquisitions is straightforward and the presence of pre-existing cracks can be accounted for as well. Three complex case studies are analyzed in detail to benchmark the approach proposed, relying into existing domes belonging to the Italian cultural heritage. The first example has the geometrical parameters of a typical late Renaissance dome, the Cathedral of Montepulciano, the second is the dome of Anime Sante church (collapsed during the L’Aquila 2009 earthquake with a paradigmatic failure mechanism) and the last is the dome of Caracalla baths, whose causes of collapse remain still unknown. In all cases inspected, the approach proposed quickly provides collapse accelerations and active failure mechanisms at a fraction of the time needed by non-linear FE analyses, providing interesting hints into the actual behavior of such kind of structures under horizontal loads.

Evaluation of virtual fixed points in the response spectrum analysis of a pile-supported wharf

Response spectrum analysis is widely employed in the seismic design of pile-supported wharves, as it can easily determine the maximum response of a structure. The analysis typically uses virtual fixed points to model the structure, without modelling the ground, as the structure is assumed to be a frame. Virtual fixed points can adequately simulate pile responses under horizontal static loads; however, pile responses under seismic loads have not been well studied. Therefore, the dynamic centrifuge tests evaluate the applicability of response spectrum analysis, using virtual fixed points, to the seismic design of a pile-supported wharf. Comparison of results from scale models (3 × 3 groups of piles from sections of Pohang New Port, Korea) with those from the analysis showed that the response spectrum analysis using virtual fixed points does not adequately simulate the natural period or pile bending moment of a pile-supported wharf system.

Model Test Study on Horizontal Static Loading of Suction Bucket Foundation under Different Scour Conditions

Abstract Under a scouring action, scouring holes occur around a suction bucket foundation and have different depths and widths. The loss of soil in scouring holes causes changes in the stress history of the remaining soil. In this study, considering the stress history, scouring depth, scouring width, and length-diameter ratio, we conducted a horizontal static loading model test of a suction bucket foundation in sand. We obtained a variation law for the ultimate bearing capacity of the foundation considering three aspects: displacement change, soil pressure distribution, and turning point position. In addition, we summarized the relationship between horizontal loads and displacements at different aspect ratios. We also demonstrated the influence of scouring factors on the distribution of soil pressure and the rotation point and revealed the mechanism influencing the scouring depth, scouring width, and history of stress on the horizontal bearing capacity of a suction bucket foundation.

On the estimation of foundation damping of mono pile-supported offshore wind turbines

This paper investigates the estimation of foundation damping in a monopile supported offshore wind turbine. The soil-structure interaction is modelled using the commercial geotechnical Finite Element (FE) software, Plaxis 3D. This allows for a more rigorous consideration of the soil response and its effect on the overall dynamic behaviour of the system. A free vibration test is simulated by applying and removing a constant horizontal static load at the top of the tower. The structure starts free vibration when the load is removed. The free decay displacement response is measured at the point of loading. The well-known logarithmic decrement method is used for the estimation of overall damping from the free decay response. The damping is estimated at different time steps along the signal to provide an instantaneous damping. It is shown that the damping varies with the amplitude of the decaying displacement response.

Horizontal Loading Tests on Disconnected Piled Rafts and a Simplified Method to Evaluate the Horizontal Bearing Capacity

Disconnected piled raft (DPR) foundations have been widely adopted as an effective foundation system where the piles are separated from the raft by a granular layer, which can limit the shear forces and moments transmitted between the raft and the piles. Thus, DPR foundations may avoid the problem of horizontal forces, such as those from an earthquake or dynamic loads, which damage the structural connection between the pile head and raft. A series of static horizontal loading tests were carried out on three types of foundation models, i.e., piled raft, disconnected piled raft, and raft alone models, on fine sand using a geotechnical model in a 1 g field. In this paper, the influences of vertical loading and interposed layer thickness were presented and discussed. The results showed that most of the horizontal force was carried by raft/interposed layer friction in the DPR foundation type, and the shear force and moment of the piles were greatly reduced due to the gap between the raft and the heads of the piles. The tested foundations were simulated using a simplified method with theoretical equations derived by making several approximations and assumptions. The simulated results agreed well with the test results.

Machine learning for combinatorial optimization of brace placement of steel frames

AbstractA method is presented for optimal placement of braces of plane frames using machine learning. The frame is subjected to static horizontal loads representing seismic loads. We consider the process of seismic retrofit by attaching braces. Therefore, the maximum value of additional stresses in the existing beams and columns and the maximum interstory drift angle are incorporated in the optimization problem. Characteristics of approximate optimal solutions and nonoptimal solutions are extracted using machine learning based on support vector machine and binary decision tree. Convolution and pooling are used for defining the features characterizing the solutions while reducing the number of variables. Optimization is carried out using a heuristic algorithm called simulated annealing based on local search. It is shown in the numerical examples that the computational cost is successfully reduced by avoiding costly structural analysis for a solution judged by machine learning as nonoptimal, and the important features in approximate optimal and nonoptimal solutions are identified.

Bearing capacity of offshore umbrella suction anchor foundation in silty soil under varying loading modes

ABSTRACTConsidering the current disadvantages of present offshore wind turbine foundations, a novel anchor foundation with skirt and branches is proposed, called offshore umbrella suction anchor foundation (USAF). A series of experiments and numerical simulations were performed to explore the bearing capacity of the USAF under various kinds of loading modes. The bearing characteristics and the anchor–soil interactions are described in detail for horizontal static loading, horizontal cyclic loading, and an antidrawing (pullout) test in silty soil. In the static loading test, the load–deflection of the anchor under step loading was analyzed and the normalized curve of the load–deflection was obtained to determine the ultimate horizontal bearing capacity of the anchor under normal working conditions. Under horizontal cyclic loading, the relationship between the plastic cumulative deformation and cyclic number was determined. In addition, the responses of USAF were investigated for a low wave frequency and storm surges. In the drawing test, it was found that a “segmentation phenomenon” occurred during the test. Moreover, a method to identify the maximum antidrawing load of USAF was provided based on dynamic mechanics. The numerical results show that the use of anchor branches and skirt can enhance the bearing performance of USAF to a certain degree. However, the anchor branch has a slight positive influence on the bearing performance improvement. The USAF is not only similar to a stiff short pile, but a rotation occurs. The failure envelope under composite loading (V-M) was obtained and the changes associated with changes in the aspect ratio of the internal compartment were clarified.

The Influence of Bonding between Layers on Pavement Performance, a Case Study of Malaysian Road

This paper summarizes a theoretical study undertaken to provide a better understanding of the consequences of poor bond on flexible pavement performance. The main objective of this paper is to investigate the influence of bond on the performance of Malaysian road. The pavement structure of Malaysian road was analyzed using a layered linear elastic program, BISAR 3.0 taking into account different state of the bond at the interfaces of the pavement layers and a static horizontal load in addition to the standard vertical dual load. The results indicate that the condition of the bond between the wearing and binder course can reduce the life of the pavement by up to 64%. On the other hand, the results also indicate that the condition of the bond between the binder and road base course, which was made up from asphaltic materials can reduce the life of the pavement by up to 68%.

Investigation of the load-bearing capacity of suction caissons used for offshore wind turbines

This paper presents the results of three-dimensional finite element analyses of the suction bucket foundation used for offshore wind turbines. The behavior of the bucket and the response of soil supporting the bucket in dense and medium dense sandy soils subjected to static horizontal load are investigated. Field tests results and a centrifuge model test are used to validate the numerical model. Dimensionless horizontal load-displacement and overturning moment-rotation relationships are derived utilizing the Power law and Buckingham’s theorem. The results show good agreement between the numerical analysis results and the straight lines obtained from the Power law until a specific value of horizontal load and overturning moment. Regarding stress behavior of soil supporting the bucket, due to soil densification and bucket movement, maximum stresses are seen near the bucket tip at the right inside of the bucket. The major part of the applied load is transferred by the bucket skirt. Numerical analysis modeling results show that the bucket rotation and displacement are highly dependent on the bucket geometry and soil properties in addition to loading conditions. Normalized equations and figures for the ultimate horizontal load and overturning-moment capacities are presented and can be used for the preliminary design of the bucket foundations in sandy soils.