Lateral Load Bearing Research Articles

Research on Lateral Load Bearing Characteristics of Deepwater Drilling Conductor Suction Pile

The vast reserves of natural gas hydrates in offshore areas present significant challenges to development. Surface well construction technology is crucial for the extraction of deepwater natural gas hydrates. To ensure the safety of the subsea wellhead during the drilling process for deepwater natural gas hydrates, a novel conductor suction pile device has been designed, comprising a combination of suction piles and surface conductors. And research has been conducted to investigate the lateral stability characteristics of the conductor suction pile. Drawing upon the pile foundation load-bearing theory and the equilibrium of the differential element, a theoretical analysis model and corresponding governing equations of the conductor suction pile system are established. A solution for a multi-point boundary value problem by simplifying the conductor suction pile system into a two-end free beam is proposed. The governing equations are then converted into a first-order differential equation system, and the four-stage Lobatto IIIa collocation method program for the multi-point boundary value problem is developed and resolved using MATLAB 2023a. Furthermore, a case study of a well in the South China Sea elucidates the effects of wellhead load and seabed soil properties on the lateral load-bearing capacity of the conductor suction pile system, verifying the collocation method’s validity against the results from the finite difference method. After conducting a comparative analysis of the lateral load-bearing performance between conductor suction piles and traditional surface conductors, it is observed that conductor suction piles exhibit lower horizontal displacement and bending moments compared to surface conductors. Therefore, conductor suction piles demonstrate a substantial safety margin. The research findings provide a theoretical basis for the lateral stability of conductor suction piles during deepwater natural gas hydrate drilling. This offers a safe and efficient method for surface well construction in the extraction of natural gas hydrates.

A new energy-dissipating RBS connection with double-nut-bolts: Seismic performance assessment and design methodology

This article investigates analytically the seismic performance of a new RBS beam-column connection system with Double Nut Bolts (RBS-DNB) and double shear tabs. The bolts in the proposed RBS-DNB connection are used to: i) increase the strength of the beam’s reduced section, ii) increase the energy dissipating capacity of the connection, and iii) delay damage of the beam in the plastic hinge zone. A reference RBS connection from the literature is first modeled and calibrated in Abaqus® software. A set of RBS-DNB connections are then designed (according to a new proposed method) and subsequently modeled in Abaqus®. The analytical results from the reference RBS connection and RBS-DNB connections are then compared in terms of cyclic response, beam strength, dissipated energy, beam hinge deformation and damage. The results show that, compared to the reference RBS connection, the proposed RBS-DNB connection system can increase the strength of the beam’s reduced section and dissipate more energy by up to 16 % and 12 %, respectively. Moreover, a damage assessment shows that RBS-DNB connections can efficiently delay the initiation of beam hinging, and reduce buckling deformation and damage to the beam hinge compared to the reference RBS connection. The new proposed design method ensured the safe load-carrying mechanism of RBS-DNB connections, and it also predicted well the potential damage at the components of the RBS-DNB connections. Finally, the results of pushover analyses on typical 4-storey buildings with RBS-DNB connections demonstrated their higher lateral load bearing capacity compared to those with conventional RBS connections. This study contributes towards developing more robust energy-dissipating connections for steel buildings located in seismic areas.

Quantitative evaluation of the tibiofemoral joint cartilage by T2 mapping in patients with acute anterior cruciate ligament injury vs contralateral knees: results from the subacute phase using data from the NACOX study cohort

Immediate cartilage structural alterations in the acute phase after an anterior cruciate ligament (ACL) rupture may be a precursor to posttraumatic osteoarthritis (PTOA) development. Our aim was to describe changes in cartilage matrix in the subacute phase of the acutely ACL-injured knee compared to the contralateral uninjured knee. Participants (n=118) aged 15-40 years with an acute ACL injury were consecutively included in subacute phase after acute ACL-injury and underwent MRI (mean 29 days post trauma) of both knees. Mean T2 relaxation times, T2 spatial coefficient of variation and cartilage thickness were determined for different regions of the tibiofemoral cartilage. Differences between the acutely ACL-injured and uninjured knee were evaluated using Wilcoxon signed-rank test. T2 relaxation time in injured knees was increased in multiple cartilage regions from both medial and lateral compartment compared to contralateral knees, mostly in medial trochlea and posterior tibia (P-value<0.001). In the same sites of injured knees, we observed significantly thinner cartilage. Moreover, injured knees presented shorter T2 relaxation time in superficial cartilage on lateral central femur and trochlea (P-value<0.001), and decreased T2 spatial coefficient of variation in lateral trochlea and load bearing regions of medial-central femoral condyle and central tibia in both compartments. Small but statistically significant differences were observed in the subacute phase between ACL-injured and uninjured knee in cartilage T2 relaxation time and cartilage thickness. Future longitudinal observations of the same cohort will allow for better understanding of early development of PTOA. NCT02931084.

Lateral load bearing characteristics of light gauge steel and lightweight concrete shear walls

In China, there is a new structural system named light gauge steel and lightweight concrete (LSLC) structure, which used lightweight concrete as structural material in composite way with cold-formed steel. Here, the shear walls are the main structural members for the LSLC structure, which are assembled with the light gauge steel lattice columns and horizontal braces, and filled with lightweight concrete. In this study, the LSLC shear walls are experimentally investigated to evaluate their failure mechanism and lateral load bearing capacity. For this purpose, several specimens with different shear span ratio are designed and tested under static cyclic loading. This paper presents the damage state and hysteresis loops of the specimens detailly. Then, the lateral load bearing characteristics of the LSLC shear walls are discussed according to the failure mechanism, such as shear and flexural failure. Finally, the calculation methods of lateral strength for the LSLC shear walls are proposed based on the diagonal strut mechanism and sectional force equilibrium.

Seismic performance evaluation and experimental validation of steel-fiber-reinforced high-strength-concrete composite shear walls

The seismic performance evaluation method for the Steel-fiber-reinforced High-strength-concrete (SFRHSC) composite shear walls are studied in this paper. Currently, seismic design codes do not include such high-performance elements, due to the lack of reliable predictive equations for the lateral load bearing capacity and the deformation capacity, which are essential quantities in design. In this study, the capacity predictive equations for the wall element are proposed, corresponding to four different performance levels with “flexure-dominated failure” mode. Cross-sectional analysis on stress and strain with a series of parameters determined according to experimental results is used to attain the predictive equations. The constitutive models for unconfined and confined SFRHSC considering fiber-bridging action are developed and discussed. Additionally, the flexural and shear displacements are quantified separately to allow the estimation of the total deformation. The accuracy of such equations is validated against experimental results, from which it is ascertained that the proposed models are able to accurately predict both the material and the element behavior. The results of this study are relevant for the development of the next generation of seismic design codes.

Effect of opening layout and sheathing on lateral load bearing capacity in wooden shear walls

Effect of opening layout and sheathing on lateral load bearing capacity in wooden shear walls

Experimental investigation of using mechanical splices on the cyclic performance of RC columns

In this study, the influence of using mechanical splices on the cyclic performance of RC columns under axial and cyclic loads was investigated experimentally. Totally six specimens were fabricated and examined; the first one was fabricated by non-spliced reinforcement bars which was considered as reference specimen. Overlap splice in the middle of the column was used in the second specimen. Threaded mechanical splices were used for the all of the longitudinal bars at 50 mm above the column-foundation interface in the third column. The fourth column was fabricated the same as the third one but half of the couplers were staggered at 600 mm above the bottom couplers. The fifth and sixth specimens were fabricated similar to the third and fourth column but shear screw-threaded couplers were incorporated instead of threaded couplers. Force-displacement hysteresis loops were presented as the output and parameters including lateral load bearing capacity, ductility, absorbed energy and stiffness are considered and discussed. Based on the obtained results, it was concluded that mechanical splices can considerably affect cyclic behavior of RC columns.

Influence of the rope effect on the slip curve of laterally loaded, nailed and screwed timber-to-timber connections

Timber-to-timber connections with different types of screws and nails were experimentally investigated with the aim to quantify the contribution of their axial resistance to their slip and their lateral load bearing capacity, which is the so-called rope effect in dowel-type timber connections. Five different types of screws, including partly threaded and double-threaded screws, as well as three types of nails, including smooth round nails, twisted square-sectioned and grooved nails, were used in the experimental investigations in order to cover a broad range of axial resistance of fasteners. Their behavior was tested in single shear and double shear timber-to-timber connections. In addition to connection testing, system and material properties were experimentally determined. This gave input to design equations and allowed for a comparison of the mechanical model in the European design standard for timber structures, Eurocode 5, with experiments. Experiments indicate that the initial slip modulus in the quasi-elastic domain is not influenced by withdrawal capacity of the fastener, while it shows pronounced influence on load-carrying capacity and the nonlinear shape of the slip curve of the connection at larger deformations. Rope effect strongly depends on fastener properties. High axial resistance of fasteners leads to highly non-linear slip curves and design equations tended to underestimate strength including the rope effect up to a displacement limit of 15 mm. Experimentally observed failure modes were well in line with the theoretical failure modes predicted by the design model. The provided experimental results are motivation for improvement of design models and development of analytical and numerical models that account for nonlinear effects in the complex load transfer mechanism.

FACTORS AFFECTING SEISMIC BEHAVIOUR OF REINFORCED CONCRETE STRUCTURES AFTER FIRE EXPOSURE

In the areas under high earthquake risk, the impact of fire damage on the seismic performance of the reinforced concrete (RC) structures ought to be realistically taken into account while assessing the fire damage to develop reuse/repair/replace strategies through the remaining service life. In the scope of this study, a literature review is conducted on the changes of mechanical characteristics of concrete and reinforcement caused by a fire with a particular emphasis on the post-cooling stage. Post-cooling behaviour of RC members is different than the behaviour under elevated temperatures and hence it is of vital importance on structural seismic performance assessment after a fire. Apart from material-wise assessment methodologies, post-fire seismic performance of RC structural members is also discussed through post-fire simulated seismic loading tests conducted on full-scale cast-in-place and precast columns. The test results pointed out to a reduction in lateral load bearing capacity of the cast-in-place columns subjected to fire whereas fire-exposed precast columns demonstrated better performance in terms of residual lateral load capacity due to the lower axial load and larger heights. All columns exhibited satisfactory performance in terms of ductility.

Lateral load behaviour of a rectangular precast shear wall involving vertical bolted connections

This article is concerned about precast reinforced concrete shear walls and the methods of assembling shear wall panels to form a reliable load transfer system. An assembling method is proposed using dry connection through an H-shaped steel connector (H-connector) and high-strength bolts. A preliminary design, including the H-connector design and bolt design, has been carried out based on the force analysis on the vertical connection in the wall assembly. On the basis of the finite element analysis verified by an experimental study, the preliminary design has been confirmed and a monolithic coefficient ( ζ) has been used to evaluate the cooperative working performance of the two parallel shear walls. Then this article continues to carry out a finite element parametric study on the mechanical behaviour of the precast reinforced concrete shear walls with varying parameters, which includes the bolt specification, the frictional coefficient on the contact surface within the bolted connection and the thickness of the H-connector flange. The lateral load bearing capacity, lateral stiffness and cooperative working performance of the wall assemblies involving these varying parameters have been broadly analysed.

Damage during the 6–24 February 2017 Ayvacık (Çanakkale) earthquake swarm

Abstract. On 6 February 2017 an earthquake swarm began at the western end of Turkey. This was the first recorded swarm in the Çanakkale region since continuous seismic monitoring began in 1970. The number of earthquakes located increased during the following 10 days. This paper describes the output of a survey carried out in the earthquake-prone towns in the area of Ayvacık, Çanakkale, Turkey, in February 2017 after the earthquakes. Observations of traditional buildings were made on site at the rural area of Ayvacık. A description of the main structural features and their effects on the most frequently viewed damage modes were made according to in-plane, out-of-plane behavior of the wall regarding construction practice, connection type, etc. It was found that there were no convenient connections like cavity ties or sufficient mortar strength resulting in decreased and/or lack of lateral load bearing capacity of the wall. Furthermore, distribution maps of damaged/undamaged buildings according to villages, damage ratios, structures and damage levels are generated. Distribution maps showed that damage ratio of structures is higher in villages close to epicenter and decrease away from epicenter except Gülpınar, where past experiences and development level affect the construction quality.

Lateral load bearing capacity of offshore high-piled wharf with batter piles

Understanding the lateral load behavior of high-piled wharf is of practical value to structural design, and the horizontal load bearing capacity of the bent is essential to analyzing the behavior of the high-piled wharf. In this paper, finite element models of high-piled wharf are built in a general finite element software–ANSYS to investigate the lateral loading behavior. Parametric analyses have been performed on the working behavior of single pile with varying slopes and section sizes under different load levels. The behavior of bent with batter piles under different lateral loads is discussed. The formulas of lateral load vs. horizontal displacement for single pile and high-piled wharf are formulated and presented in this paper. The numerical simulation results of pile top displacement are found to be in good agreement with those predicted using the theoretical formula presented in this paper. These formulas, which describe the relationship between top displacement and stiffness, inclination and loads, can be useful to determine the horizontal load bearing capacity of the high-piled wharf with batter piles and can realize the real-time safety monitoring of the high-piled wharf for practical application.

Lateral load bearing capacity modelling of piles in cohesive soils in undrained conditions: An intelligent evolutionary approach

The complex behaviour of fine-grained materials in relation with structural elements has received noticeable attention from geotechnical engineers and designers in recent decades. In this research work an evolutionary approach is presented to create a structured polynomial model for predicting the undrained lateral load bearing capacity of piles. The proposed evolutionary polynomial regression (EPR) technique is an evolutionary data mining methodology that generates a transparent and structured representation of the behaviour of a system directly from raw data. It can operate on large quantities of data in order to capture nonlinear and complex relationships between contributing variables. The developed model allows the user to gain a clear insight into the behaviour of the system. Field measurement data from literature was used to develop the proposed EPR model. Comparison of the proposed model predictions with the results from two empirical models currently being implemented in design works, a neural network-based model from literature and also the field data shows that the EPR model is capable of capturing, predicting and generalizing predictions to unseen data cases, for lateral load bearing capacity of piles with very high accuracy. A sensitivity analysis was conducted to evaluate the effect of individual contributing parameters and their contribution to the predictions made by the proposed model. The merits and advantages of the proposed methodology are also discussed.

Experimental Investigation of Flax FRP Tube Confined Coconut Fibre Reinforced Concrete

The compressive and flexural performance of flax fibre reinforced polymer (FFRP) confined coconut fibre reinforced concrete (CFRC) structures were investigated. The mass content of coconut fibre considered was 1% of cement. Eighteen cylinders were tested under uniaxial compression and 12 beams were tested under four-point bending. Test results show that in compression, both FFRP tube and FFRP wrapping confinements enhance the axial compressive strength and ultimate strain of concrete significantly, e.g. the ultimate strength of 4-layer FFRP tube confined CFRC is 94% larger than that of the unconfined CFRC. In flexure, the FFRP tube increases the lateral load bearing capacity and the deflection several times larger than the unconfined concrete columns, e.g. the ultimate lateral load of 4-layer FFRP confined PC and CFRC are 1066% and 946% larger than the corresponding unconfined PC and CFRC specimens. In flexure, coir inclusion can affect the failure mode of the FFRP-CFRC composite structure significantly.

Reliability Index Calculation of Lateral Load Bearing Single-Piles Based on ANSYS

At present, it is scarcely possible to represent results in deterministic calculation in the definite finite element analysis. Stochastic finite element method is on the basis of the combination of mathematical statistics and the finite element method. Then we can use mathematical statistics to analyze the randomness of the parameters, get the data of dependent displacement and stress, and finally calculate all kinds of features. In this paper, modeling and calculation function and unique PDS module offered by ANSYS are applied to analyze the reliability of lateral load bearing single-piles.

Application of Different Rehabilitation and Strengthening Methods for Insufficient RC Beam-Column Joints

Earthquake is one of the most destructive natural disasters that cause loss of life and property in the earthquake prone regions. Unsuitable soil conditions, inadequate material properties and deficiencies in the structural system can lead to costly seismic damages to structures. In this study, damages caused by the earthquake were examined for reinforced concrete beam-column joints. The most common damage type observed in earthquakes is the beam-column joint damage that decreases the lateral load bearing capacity and might be the reason for total collapse of structures. Weak bonding between concrete and reinforcing bars, absence of transverse reinforcement and incapable shear strength of RC beam-column joint are the most common causes for RC beam-column joint damage. After numerous experimental works, different strengthening methods were developed in literature. This paper discusses various strengthening methods including conventional and new techniques as well as their technological application details and the issues arise in practice

The Gusset Plate Effect in Steel Plate Shear Wall Systems

A steel plate shear wall dual system consists of a moment resisting frame plus thin infill shear panels. In the literature, it is stated that the ultimate lateral load bearing capacity of such a dual system can be evaluated by a simple addition of the discrete frame, brought about by the formation of plastic hinges and that of detached infill panel evaluated when yield patterns form along their diagonal tension folds. However, more recent studies show that there is an interaction effect between the wall and the frame and that the combined system can resist additional loads. In other words, the principle of superposition does not apply to this dual lateral load resisting system. This super added value may arise from two factors: (a) the influence of beam and column rigidities on the buckling and ultimate load bearing capacity of panel, and (b) the influence of the panel on the frame. This article studies the latter effect, otherwise known as the gusset plate effect in shear-walled frames.

Load Bearing Capacity Analysis of Squeezed Branch and Plate Pile under Vertical and Lateral Loads

Considering the initial stress field and concrete damage, no-linearity caused by crack of concrete, non-linear of reinforcement, elastic-plastic of soil around pile, couple interaction between concrete and steel, non-linearity contact of interface between pile and soil, the lateral load bearing capacity of squeezed branch and plate pile under vertical and lateral load is studied with infinite element and finite element couple method. The results indicate that the vertical load decreases the lateral displacement of pile top and increase the pile lateral load bearing capacity at the same time.

Experimental Investigation on the Effect of Reinforcement Ratio to Capacity of RC Column to Resist Lateral Impact Loading

The influence of lateral impact loading rate, longitudinal reinforcement ratio and stirrup ratio on the failure mode, lateral load bearing capacity etc. was investigated. It was carried out with experimental research on the dynamic response of RC columns under lateral impact loading. Results show that increasing in longitudinal reinforcement ratio can enhance ultimate load bearing capacity of columns. The greater the loading rate, the greater the increased amplitude. It is also demonstrated that he main influence factor on the failure mode of RC columns is stirrup spacing. The column is prone to shear failure when the stirrup spacing is large otherwise to flexural failure.

Spinal stability is improved by inducing a lumbar lordosis in boys with Duchenne Muscular Dystrophy: A pilot study

The development of scoliosis in boys with Duchenne Muscular Dystrophy (DMD) is a significant, morbid event in the progression of the disease caused by progressive spinal musclulature weakness. As an alternative to muscle activity, the spine can also be stabilised by locking the articular facet joints, which is achieved when the body is supported on a seat tilted anteriorly using a ‘wedge’, of the kind commonly recommended for low back pain. We tested spinal stability when using a seat tilted 15° anteriorly in eight boys with DMD, without significant scoliosis, by measuring the ability to support a lateral load applied to the thorax through a sling and hawser. All eight boys tolerated lateral loading better with wedged seating and were able to support an average additional load of 95 g per kilogram of body weight compared to normal seating. Lateral load bearing was improved in 10 normal control boys by an average of 40 g per kilogram of body weight. These encouraging pilot findings indicate that there is a need for further studies on the effectiveness of passive mechanical factors in spinal stabilisation to delay the development of scoliosis in boys with DMD.