Vertical Load Level Research Articles

Effect of vertical load on the lateral response of offshore piles considering scour-hole geometry and stress history in marine clay

Scour induces the loss of soil support around the pile foundations for the offshore and coastal structures, and thus increases their bending moments and lateral deflections, which may change the vertical loads effect on the lateral response of piles applied in such cases. In this paper, the stress changes of the remaining soils at the corresponding pile location due to the three-dimensional scour-hole formation are first determined based on the Mindlin's elastic solutions. Then, the calculated new soil stresses are adopted to re-examine the Young's modulus of the remaining soils undergoing a stress history due to scour. With this key soil parameter that have been modified appropriately to reasonably reflect the effects of three-dimensional scour-hole geometry and the stress history of the soils simultaneously, an analytical model based on the principle of minimum potential energy is further developed to investigate the influence of vertical loads on the lateral responses of offshore piles in marine clay under scour conditions. The influence of related parameters including the lateral displacement level and the vertical load level with different scour-hole dimensions (i.e., scour depth, scour width and scour-hole slope angle), considering or ignoring stress history effect, have also been analyzed based on a case study. The results show that scour depth plays the most important role among the various scour-hole dimensions in influencing the responses of scoured piles under combined vertical and lateral loading. Although still possessing some limitations (e.g., the simplistic assumption of linear-elastic behavior for the soil and the approximate allowance made to account for the gapping effect), the simplicity and relative ease of utilization offered by this proposed analytical model make it a good alternative approach for estimating the deflection and moment responses of the scoured pile foundations subjected to combined lateral and vertical loading.

Degradation laws of hysteretic behaviour for historical timber buildings based on pseudo-static tests

This paper reports on the pseudo-static tests (PSTs) with a single storey full-scale timber building with architectural details that are prevailing in the Song dynasty, China (A.D. 960–1279). The PSTs were conducted under three levels of vertical load. The force and displacement relationship at selected points in the backbone curves were analysed for the structural stiffness and the accumulated energy dissipation with varying ductility coefficient. The degradation ratios of the bearing capacity, lateral stiffness, and the accumulated energy dissipation of the structure under different vertical loads were obtained. The trilinear backbone curve in PST1 is different from the bilinear relationship in PST2. The stiffness degradation can be modelled with a power function while it is accompanied with a reduced maximum accumulated energy dissipation.

Quality indicators after discharge from the intensive care unit in 3 public hospitals

Although there are many researches on infilled steel frames with welded beam-to-column connections, however, few studies were undertaken to investigate the behaviour of these infilled structures but with other common connection types (extended endplate, flush endplate and header plate connections), particularly under combined vertical and horizontal loading. In this paper, firstly, a simplified numerical model of infilled steel frames under cyclic loading, considering the interactions between frames, infills and beam-to-column connections' components, was constructed. The model results were compared with experimental data for cyclically-loaded infilled frames, showing good agreement. Using the verified model, a parametric study on infilled steel frames with five different beam-to-column connection types, under vertical and cyclic horizontal loads, was performed. Several parameters, including vertical load level, infill thickness and vertical load application method, were investigated. The results showed that increasing the level of vertical load (uniformly distributed on the beam) minimised the difference in performance between the frames with welded connections and those with bolted connections. Under vertical loads of 0, 16% and 24% of the columns' axial capacity, the horizontal ultimate load of frames with header plate connections, was, respectively, 73%, 86% and 91% of that of frames with welded connections. Hence, when the infilled frames are subjected to relatively high levels of vertical load, utilising header plate connections may be a viable alternative to using welded connections. Furthermore, a simple analytical method for predicting the stiffness and load-carrying capacity of masonry-infilled steel frames (with different connection types) under vertical and horizontal loads, was proposed.

Steel bridge in interaction with modern slab track fastening systems under various vertical load levels

In modern slab tracks the continuously welded rail (CWR) is coupled through the fastening system with the substructure. The resulting restriction of expansion movement causes significant rail stress increments, which in the case of extreme loading may cause rail failures. These interaction phenomenon effects are naturally higher on a bridge due to different deformation capabilities of the bridge and the CWR. The presented contribution aims at investigating the state of the art European direct fastening system that is suitable for application on steel bridges. Analysis involves experimental determination of its nonlinear longitudinal interaction parameters under various vertical loads and numerical validation. During experimental procedures a two and a half meter long laboratory sample equipped with four nodes of the Vossloh DFF 300 was tested. There have been checked both DFF 300 modifications using the skl 15 tension clamps and the low resistance skl B15 tension clamps. The effects of clamping force lowering on the interaction parameters have also been investigated. Results are discussed in the paper.

3D numerical analysis of piled raft foundation in stone column improved soft soil

The concept of composite piled raft foundation incorporates piles of different lengths and stiffness, where short columns of flexible materials improve the shallow soft soil and longer columns of relatively rigid material support loads and reduce settlement. Present study utilised this concept by employing stone columns beneath the piled raft foundation and investigated its response through three-dimensional finite element analyses. Effects of area replacement ratio, slenderness ratio and material properties of stone column, slenderness ratio of pile and thickness of raft have been examined on the proportion of load shared by piles and stone columns and settlement response of piled raft under different levels of vertical load. Results showed that strengthening the shallow soft soil with stone columns was effective in improving the bearing interaction of raft, i.e. increasing the proportion of load shared by stone columns, and reducing the total settlement of the piled raft. Percentage load shared by piles was significantly influenced by the slenderness ratio of piles and level of vertical load on raft, but was almost independent of properties of stone columns and thickness of raft. Increment in diameter of stone columns (area replacement ratio) significantly improved the bearing interaction of raft, and increment in their lengths (slenderness ratio of stone columns) reduced the settlements of the foundation system. Increase in angle of friction of constituent stone column material improved both the bearing interaction of raft and settlement performance of the foundation system. Increment in raft thickness not only enhanced the proportion of load shared by stone columns, but also drastically reduced the total and differential settlements of the foundation.

Numerical study on masonry-infilled steel frames under vertical and cyclic horizontal loads

Although there are many researches on infilled steel frames with welded beam-to-column connections, however, few studies were undertaken to investigate the behaviour of these infilled structures but with other common connection types (extended endplate, flush endplate and header plate connections), particularly under combined vertical and horizontal loading. In this paper, firstly, a simplified numerical model of infilled steel frames under cyclic loading, considering the interactions between frames, infills and beam-to-column connections' components, was constructed. The model results were compared with experimental data for cyclically-loaded infilled frames, showing good agreement. Using the verified model, a parametric study on infilled steel frames with five different beam-to-column connection types, under vertical and cyclic horizontal loads, was performed. Several parameters, including vertical load level, infill thickness and vertical load application method, were investigated. The results showed that increasing the level of vertical load (uniformly distributed on the beam) minimised the difference in performance between the frames with welded connections and those with bolted connections. Under vertical loads of 0, 16% and 24% of the columns' axial capacity, the horizontal ultimate load of frames with header plate connections, was, respectively, 73%, 86% and 91% of that of frames with welded connections. Hence, when the infilled frames are subjected to relatively high levels of vertical load, utilising header plate connections may be a viable alternative to using welded connections. Furthermore, a simple analytical method for predicting the stiffness and load-carrying capacity of masonry-infilled steel frames (with different connection types) under vertical and horizontal loads, was proposed.

Hysteresis behavior of traditional timber structures by full-scale tests

To study the seismic response of a traditional timber structure in China, a full-scale model capturing the main characteristics of a representative ancient Chinese wooden structure in Song Dynasty (960–1279 AD) was established and tested considering three different levels of vertical loads, which is one-story sophisticated timber structure consisting of four columns and Dou- gong sets. A swing column was used to apply the synchronous horizontal force. Tests under the low-cyclic loading were performed considering three levels of vertical load to reveal the hysteretic behavior of the historic buildings. Based on the observed characteristics from restoring forces, the ancient wooden structure appears to have a good ductility despite of its low inherent energy dissipation capability. Based on the test results, the following relationships are established: loads versus displacements with key turning points, the loads at the key points versus the roof weights, the displacements at the key points with the column diameter, and structural stiffness versus ductility. Finally, a limiting value of drift angle for structural design and the equivalent viscous damping and ductility factor for dynamical response analysis are proposed.

Nonlinear Characteristics of the Pile Soil System under Vertical Vibration

In this paper, the inverse problem of the nonlinear vibration of pile foundations has been studied. The methodology proposed by Novak is used to identify the parameters of the soil-pile system from the measured response displaying nonlinear features. A comprehensive study involving both vertical dynamic testing of piles and theoretical analysis is described. The dynamic tests are carried out on single and 2 × 2 group piles in the field under varying levels of vertical harmonic load. From the measured nonlinear response curves, the effective pile-soil system mass, stiffness and damping are determined using the methodology of Novak assuming nonlinear restoring force and linear damping force. It is found that the stiffness of pile-soil system markedly decrease with increasing exciting intensity but the damping increase with exciting moments. Finally the dynamic responses of piles are back-calculated using the estimated nonlinear parameters. It is found that theoretical nonlinear response curves agree well with that obtained from vertical vibration tests.

Evaluation of Changes in Soil Compaction Due to the Passage of Combine Harvester

This paper concerns the results of changes in soil compaction after the passages of combine harvester. The research was done on the maize-stubble; the soil was the mold formed in the sand. The measured parameter was a penetration of resistance in range of depth 0–60 cm. The measurements were done in the ruts after the passages the front and rear wheel of combine harvester. During the experiment two levels of vertical load of wheels were applied – these levels were dependent on filling of grain tank of harvester. Moreover, the influence of the lateral tilt of harvester on the soil compaction was analyzed (the harvester was equipped with the leveling system which allowed to obtain the tilt). The obtained results shows that the increase in vertical load caused greater compaction in ruts. Furthermore, it was found that the passage of tilted harvester caused lower compaction than the harvester without tilt.

A numerical and experimental study of hollow steel pile in layered soil subjected to vertical dynamic loading

This paper presents an investigation of the nonlinear behaviour of single piles subjected to varying levels of vertical dynamic load. A good number of tests are performed for the understanding of the dynamic behaviour of single hollow steel piles embedded in layered soil. Experimental results are validated with results obtained from a nonlinear numerical analysis using commercially available Finite Element Method (FEM) based software. The results of numerical analysis and experimental investigations showed that the length of pile has significant influence on resonant frequency and amplitude of the pile foundation. It has also been found that the slippage of pile from the surrounding soil considerably affects the resonance frequency and amplitude of the soil–pile foundation system.

A finite element study of the effect of vertical loading on the in-plane behavior of concrete masonry infills bounded by steel frames

A finite element study was performed to investigate the effect of vertical loading on the in-plane lateral behavior and strength of concrete masonry infills bounded by steel frames. An experimental program was also conducted and results were used to verify the finite element model. Parameters considered in the finite element study included the vertical load level and application method, infill aspect ratio, infill compressive strength, and bounding frame stiffness. Results showed that when applied as a uniformly distributed load on the frame beam, an optimal load level was identified and the vertical load, when applied within this load level, was found to be beneficial to the lateral stiffness and strength of the infilled frame. When applied as point loads on columns, the vertical load was shown to reduce the lateral strength of the infilled frame. Based on the regression analysis on finite element results, a simplified analytical model was proposed to account for the effect of vertical loading through the use of a modification factor on the lateral stiffness and strength of infilled steel frames. The proposed model was shown to provide results in good agreement with finite element values over a wide range of load levels, infill material strengths, and frame stiffnesses.

Vertical Facing Panel-Joint Gap Analysis for Steel-Reinforced Soil Walls

AbstractThis paper reports the results of a numerical parametric study focused on the prediction of vertical load distribution and vertical gap compression between precast concrete facing panel units in steel-reinforced soil walls ranging in height from 6 to 24 m. The vertical compression was accommodated by polymeric bearing pads placed at the horizontal joints between panels during construction. This paper demonstrates how gap compression and magnitude of vertical load transmitted between horizontal joints are influenced by joint location along the height of the wall, joint compressibility, and backfill and foundation soil stiffness. The summary plots in this study can be used to estimate the number and type (stiffness) of the bearing pads to ensure a target minimum gap thickness at the end of construction, to demonstrate the relative influence of wall height and different material component properties on vertical load levels and gap compression, or as a benchmark to test numerical models used for proje...

Seismic Analysis of Cross-Laminated Multistory Timber Buildings Using Code-Prescribed Methods: Influence of Panel Size, Connection Ductility, and Schematization

AbstractThis paper investigates the seismic analysis of multistory cross-laminated timber (XLAM) buildings. The influence of different parameters such as wall geometry, vertical load level, friction, and, most importantly, connection stiffness, strength, and ductility is assessed. Linear and nonlinear finite-element (FE) analyses are carried out on a hypothetical 4-story case study building. The actual load-carrying capacity of the case study building is calculated with the nonlinear static pushover method and assessed using displacement-based design. The XLAM building behavior factors are then derived for different cases using a simplified method. Values in the range 2–3 have been obtained depending on whether monolithic or segmental walls (namely made of approximately 2-m-wide panels screwed to the adjacent ones) are used. Further nonlinear dynamic analyses carried out on a part of the case study building show that friction may have a beneficial effect on the seismic resistance of XLAM buildings. Howeve...

Experimental in-plane behavior and retrofitting method of mud-brick walls

Despite the rapid growth of engineering science especially in the modern structural engineering and application of new materials in civil engineering, a significant percentage of world population in different countries are living in adobe buildings made from mud-bricks. In this paper, by performing experimental study on scaled mud-brick walls under monotonic load, inplane behavior of the walls have been investigated for different levels of vertical load. After recognizing damage mechanisms from experiment, a simple retrofitting method has been presented to upgrade wall performance. Experimental behavior of retrofitted walls was also studied. The proposed retrofitting method consists of using polypropylene lace and tarpaulin belts. As a result, a better performance of the walls in terms of shear capacity, ductility and energy absorption are observed by using proposed retrofitting method. Meanwhile, Proposed retrofitting method has significant effect in rocking mechanism delay and prevention of wall sudden collapse.

The Application of Hydraulic Method to Geotechnical Compression Test

The geotechnical consolidation test is used to detect the soil deformation under all levels of vertical load. Consolidation parameters play a vital role in the basal design of the buildings. But the lever consolidometer covers too large area, and needs high labor intensity. The pressure consolidometer is not convenient to find leak, noisy, and is affected by the power supply. We developed the hydraulic consolidation system, which is aid to make consolidation tests of the soil samples. The hydraulic consolidation system is composed of the hydraulic pump used as a pressure source, the hydraulic piston cylinder used as the load transfer device, intelligent instrument and solenoid valve. Through the comparison of the test by three methods, it proved that the test results are identical. The coefficient of variation of the parameters is less than 0.1, while its efficiency is 31.33 times higher than the lever test, 6.86 times higher than the pressure method.

In-plane shear behaviour of unreinforced and jacketed brick masonry walls

This paper deals with the results of cyclic load tests on masonry walls performed for the purpose of evaluation of in-plane shear behaviour and identification of shear strength, stiffness and energy dissipation. Eight walls in two series were assembled in laboratory conditions. The first series consisted of four unreinforced masonry walls constructed from solid clay bricks and lime mortar. The walls from the second series were strengthened by application of RC jackets on both sides. These were constructed of the same material and were characterized by the same geometry properties and vertical load levels as those of the walls from the first series. The main goal of the tests was to compare the behaviour of the unreinforced and strengthened walls under cyclic horizontal load. The results from the tests showed that the application of the strengthening method contributed to a significant improvement of the shear resistance of the jacketed walls. Analytical models were used to predict the shear resistance of the walls. Good agreement with the experimental results was obtained with a model based on tensile strength of masonry.

Investigating the effect of velocity, inflation pressure, and vertical load on rolling resistance of a radial ply tire

A single-wheel tester facility at Department of Agricultural Machinery of Urmia University was utilized to investigate the effect of velocity, tire inflation pressure, and vertical load on rolling resistance of wheel. A Good year 9.5L-14, 6 radial ply tire was used as the tester wheel on clay-loam soil and was installed on a carriage traversing the length of soil bin. Three inflation pressures of 100, 200, and 300kPa as well as three levels of velocity (i.e. 0.7, 1.4, and 2m/s) and five levels of vertical load applied on wheel (i.e. 1, 2, 3, 4, and 5kN) were examined. Covariance analysis (ANCOVA) of resulted data revealed that rolling resistance is less effected by applicable velocities of tractors in farmlands but is much influenced by inflation pressure and vertical load. An approximate constant relationship existed between velocity and rolling resistance indicating that rolling resistance is not a function of velocity particularly in lower ones. Moreover, it was observed that increase of inflation pressure results in decrease of rolling resistance. Additionally, increase of vertical load brings about increase of rolling resistance which was estimated to have polynomial relation with order of two. A model comprising tested variables was developed with relative high accuracy.

Development of a new rubber seismic isolator: ‘Ball Rubber Bearing (BRB)’

AbstractThis paper presents an experimental research aimed at developing a new rubber‐based seismic isolator called ‘Ball Rubber Bearing (BRB)’. The BRB is composed of a conventional steel‐reinforced multi‐layered rubber bearing with its central hole filled with small diameter steel balls that are used to provide energy dissipation capacity through friction. A large set of BRBs with different geometrical and material properties are manufactured and tested under reversed cyclic horizontal loading at different vertical compressive load levels. Extensive test results indicate that steel balls do not only increase the energy dissipation capacity of the elastomeric bearing (EB), but also increase its horizontal and vertical stiffness. It is also observed that the energy dissipation capacity of a BRB does not degrade as the number of loading cycles increases. Copyright © 2011 John Wiley & Sons, Ltd.

Research on the Factors Affect the Settlement of Soft Pile in Double-Layered Foundation

The pile work on the complex properties of three-dimensional finite element analysis has been made by building-up one 4x4 soft pole. Having studied on the factors which affect the flexibility pole compound foundation settlement factor in foundation, include the level of vertical load, elastic modulus of the pile, cushion thickness and elastic modulus. The results show that: the impact of soft pile settlement of the factors, the level of vertical load and pile elastic modulus greater impact cushion modulus of elasticity and thickness of the less affected. As for the pole body elasticity modulus and the bed course elasticity modulus, the compound foundation existence is controlled give value preferential treatment most subsides, the bed courses among them almost can be ignored since effect is less.

비닐하우스 아치구조의 모달실험

To determine the static buckling loads and evaluate the structural performance of slender steel pipe-arches such as for greenhouse structures, a series of modal tests using a fixed hammer and roving sensors was carried out, by providing no load, then a range of vertical loads, on an arch rib in several steps. More attention was given to an internal arch where vertical and horizontal auxiliary members are not placed, unlike an end arch. Modal parameters such as natural frequencies, mode shapes and damping ratios were extracted using more advanced system identification methods such as PolyMAX (Polyreference Least-Squares Complex Frequency Domain), and compared with those predicted by commercial FEA (Finite Element Analysis) software ANSYS for various conditions. A good correlation between them was achieved in an overall sense, however the reduction of natural frequencies due to the existence of preaxial loads was not apparent when the vertical load level was about up to 38% of its resistance. Some difficulties related to the field testing and parameter extraction for a very slender arch, as might arise from the influences of neighboring members, are carefully discussed.