Compressive Load Capacity Research Articles

Study on compressive strength characteristics of selective inhibition sintered UHMWPE specimens based on ANN and RSM approach

Selective inhibition sintering (SIS) is an evolving additive manufacturing (AM) technology that enables to build functional parts from various polymers, metals and ceramics materials in reasonable cost and time. SIS parts are significantly influenced through their process parameters. Further, due to the brittleness and anisotropic characteristics of functional parts, optimization of SIS process variables is necessary to improve the compressive loading capacity. In this study, the effect of five main SIS process parameters such as infrared (IR) heater power, bed temperature, IR heater feedrate, layer thickness and IR heater scanning distance on the compressive strength (CS) of selective inhibition sintered ultra-high molecular weight poly ethylene (UHMWPE) test specimens was examined. Firstly, experimentations were conducted based on Box–Behnken design (BBD) scheme by considering three levels for each process parameters. Subsequently, the CS of SIS test specimens were predicted using response surface methodology (RSM) based on developed quadratic regression model. Finally, the predicted CS using RSM model were compared with that of artificial neural network (ANN) model. Further, the influence of SIS parameters on CS was studied through performing analysis of variance (ANOVA) and sensitivity analysis. The results show that the power and feed rate of the infrared heater have a significant influence on CS. Furthermore, an optimization was performed using the desirability approach to identify the optimal levels of the SIS process parameters and was validated through experimental result.

Compressive Load-Carrying Behavior of Inclined Micropiles Installed in Soil and Rock Layers

Abstract Micropiles are an effective option to enhance the load-carrying performance of buildings and infrastructure. In this study, the compressive load capacity and load-carrying mechanism of inc...

Effect of MS Rings’ Confinement on Lateral Deformations of M 25 Grade Circular RCC Columns under Axial Compression Loads

Confinement has been always a key concern area for researchers in present and in past also. The metal confinement of RCC columns has been extensively used from long time like concrete-filled steel tube (CFST) columns etc. In the present work mild steel rings have been used as confining material. In this paper based on experimental work, it is aimed to improve the axial compression strength and lateral deformation characteristics of circular RCC columns confined by mild steel (MS) rings. Total 45 nos. of specimen of size 150 mm dia. and 300 mm height were prepared during the experimental work. These specimen were tested and results were analyzed.These MS rings confined circular RCC columns of M 25 grade concrete were experimentally studied for different variables like (i) % of column main vertical steel bars (ii) thickness of MS rings (iii) spacing of MS rings. It was found that the MS ring confinement effectively helped in reducing lateral deformation of circular RCC column specimen resulting in improved axial compressive load capacity of circular RCC columns also. As MS rings are made up of conventional material i.e. mild steel pipes, the technique has a vast application area. In rural part of India this technique can be conviniently used for the efficient confinement of RCC columns.

Axial Compression Testing of Bamboo-Laminated Encased Steel Tube Composite Columns

To resolve the problem of premature glue failure in square, thin-walled steel tube/bamboo-laminated composite hollow columns (SBCCs) under compression, a new type of SBCC with transverse binding bars (SBCCB) is proposed. An axial compression test was performed on nine SBCCBs to observe the compressive failure mode and analyse the influence of the net cross-sectional dimension, slenderness ratio and cross-sectional composition on the glue failure and the ultimate bearing load; the results were compared with the known limit stress of SBCCs without transverse binding bars. The experimental results indicate that the compressive damage to SBCCBs is primarily the breaking of the bamboo plywood material and glue failure between the matrix interfaces at the end and middle of the column between the binding bars. The ultimate bearing load is not only related to the dimensions of the cross section and the slenderness ratio but also impacted by the cross-sectional composition. Installing transverse binding bars can effectively reduce glue failure in the test specimens, alter the limit failure mode and significantly increase the ultimate bearing load. Compared to the limiting compressive stress on an SBCC, the limiting compressive stress on an SBCCB is 26% higher on average. A formula for calculating the axial compressive load capacity of an SBCCB was established using nonlinear regression analysis.

Experimental and numerical studies of laminated plates with delamination subjected to compressive loads

Abstract In this research, the multilayered composite plates made of glass/epoxy material were experimentally and numerically investigated under compressive loading conditions. The intact and defected structures were analyzed with the use of finite element method. The influence of the thickness and geometrical imperfection level were carried out in the linear buckling analysis. The nonlinear analysis was performed to determine the influence of the delamination length on the buckling behavior of the plate. The numerical results were validated by experiments. Experimental tests were performed for structures having artificial delamination between laminate layers. The buckling behavior was monitored using the nondestructive and noncontact structural vision-based health monitoring system (the digital image correlation (DIC)). The influence of the different delamination behavior during the tests on the compressive load capacity was determined by a detailed analysis of DIC measurements. The 20% reduction of the compressive load was noticed in the cases with local buckling of delamination.

Numerical Study on Uniaxial Compression Behavior of Geobags

Geobags have been used as coastal erosion control and flood preventing measures during the last decades. More recently engineers have used geobags to improve the bearing capacity of soft soils. In this paper, a study was performed to investigate the behavior of geobags under compression loadings utilizing a finite element computer software. The numerical modeling was verified by simulating reported laboratory compression test results. The effects of various parameters such as geobag's dimensions, mechanical characteristics of filling soil and bag material properties on the ultimate bearing capacity of geobags were investigated. It was shown that increasing the friction angle of filling soil and the tensile strength of textile lead to an increase in the geobag ultimate compressive load capacity. On the other hand, an increase in dilation angle of filling soil, Poisson's ratio and the height of geobag lead to a decrease in the ultimate compressive load capacity of geobags.

Performance Assessment of Screw Piles Embedded in Soft Clay

Screw piles are widely used in a variety engineering applications supplying stability against compression, overturning moment, uplift tension, and horizontal loads. Screw pile is a famous solution for support light structures, roads and rail signs which have relatively low-capacity foundation. In this study, the behavior of circular (10) mm solid screw pile models embedded in a bed of soft clay soil covering a layer of sandy soil has been studied. The 200 mm thick sand layer was compacted in a steel container with a diameter of 300 mm into four sublayers. The sandy soil layer was compacted at a relative density of 70%. The 300 mm thick soft clay soil bed with Cu (30) kPa was compacted in six sub-layers on the sandy bottom layer. Model tests are carried out with screw piles with a length of 300 mm, 350 mm and 400 mm and a helix diameter of 30 mm. Also, single and double helix and different S/Dh ratio were used for these piles and a comparative study between screw piles and ordinary piles (without helices) is accomplished. This study revealed that introducing screw pile of double helix increases its bearing capacity in soft clay soil by up to a (4-8) % as compared to a single helix screw pile. The results showed that the behavior of screw pile essentially depends on the geometric properties of the pile. According to the achievements, compressive load capacity of screw piles depends on embedded length, spacing ratio (S/Dh) and number of helical plates.

Macroporous scaffolds of cross-linked Poly(ɛ-caprolactone) via high internal phase emulsion templating

A high internal phase emulsion based ring-opening polymerization (HIPE-ROP) of ɛ-caprolactone (CL) was conducted to fabricate macroporous scaffold in a single-step. An oil-in-oil HIPE of CL was formed using high molecular weight olefin (C10-C16) dispersed in continuous medium comprised of CL, a bifunctional cross-linking monomer bis-ɛ-caprolactone-4-yl (BCY) and catalyst stannous octoate (Sn(Oct)2). The emulsion was stabilized using nonionic surfactant, pluronic F127 and polymerization was conducted at 120 °C without any inert atmosphere for a period of 8 h. Complete monomer conversion and cross-linking was achieved and am acroporous scaffold of desired shape was obtained, having in-situ generated porosity and interconnected pores. All chemicals were purposely used without any purification and the high temperature process prevented deactivation of catalyst. The HIPE-ROP developed in this way was found to be highly feasible for conducting otherwise moisture sensitive organo-metallic catalyst based ROP. The morphology of HIPE was directly transferred to macroporous structure of the scaffold in this process where pore size was reproducibly controlled by variation in volume fraction of dispersed phase and cross-link density. The resultant macroporous scaffold showed superior compressive loading and swelling capacity. The porous scaffolds also exhibited excellent osteoblast (MG63) attachment and proliferation. HIPE-ROP based macroporous scaffold of cross-linked PCL thus developed paved a new route to create porous scaffolds of aliphatic polyesters in a single step. The method also reflected high commercial viability by potential conversion into a continuous process.

Low-velocity impact responses and CAI properties of synthetic foam sandwiches

This paper presents experimental and analytical studies on impact and compression after impact (CAI) responses of sandwiches with glass fiber reinforced polymer (GFRP) skins and synthetic foam cores under low-velocity impacting. The impact test results showed that the penetration depth of GFRP panels with synthetic foam is much smaller than that of bare synthetic foam panels. The edgewise compression test results indicated the facesheet debonding dominates the failure mode of the sandwich panels without lattice webs, while the failure mode of the sandwich panels with lattice webs is predominated by the wrinkling and delamination of the facesheets and the crushing of foam core. The influences of applied impact energy, GFRP lay-up, synthetic foam density and the existence of webs on the impact and post impact behavior of sandwich panels are discussed herein. Analytical models are proposed to predict the residual ultimate edgewise compressive load capacity of sandwich panels with lattice webs after impacts, using energy principles and variational methods in applied mechanics. The influences from impact damage, the local buckling of the facesheets and the confined strength of the foam core are measured and compared well with proposed analytical models.

Compression behaviour of clay bricks prisms, wallets and walls - Coating influence

This work describes an experimental study carried out on running bond 195 red clay prisms, of two and three ceramic blocks, with and without cement mortar coating and some samples reinforced with mesh, subjected to axial compression in order to enhance the capacity of masonry. The prisms were subjected to compressive loading and all of them had deformation control on each face with a deflectometer, to obtain information about the structural behaviour of the prisms. The experimental results indicate an increase both in the compressive load capacity of the coated prisms and in those that use coatings based on reinforced mortar, not complying with the specifications of conventional structural mortar. The load ratios of prism/wallettes and prisms with two blocks/prisms with three blocks were satisfactory.

Behaviour of concrete-filled corrugated steel tubes under axial compression

Concrete-filled tubular (CFT) structures are exposed to increasingly complex environments with ever-broadening applications. Anticorrosion maintenance is generally difficult and expensive for established structures exposed to the air. Due to the superior corrosion resistance and the high lateral stiffness of the corrugated steel pipe (CSP), concrete-filled corrugated steel tube (CFCST) is proposed which has the similar working mechanism with the tube confined concrete columns. Such innovative composite member has advantages such as free of maintenance, ease of construction, high load-bearing capacity, good ductility and strong interlocking effect between CSP and concrete. In order to verify the load bearing reliability of concrete-filled corrugated steel tube (CFCST), twenty-one short columns including twelve CFCSTs were tested under axial compression. It was found that the CFCST is a tube confined concrete member and behaves slightly better than tubed-concrete columns. The strain and stress of CSP are discussed in detail to clarify the confinement effect. As well, solid nonlinear finite element models (FEM) were established to investigate the influence of key factors including geometries of CSP and strength of materials, which were summarized in the confinement index. Based on early studies on steel tube confined concrete and the parameter analysis in this paper, a suitable design method to predict the ultimate axial compressive load capacity for CFCST columns is proposed in this paper.

A Detailed Experimental Study on The Flexural Behaviour of Concrete Filled Steel Tube Beams

Concrete filled steel tubes (CFST) member have many advantages compared with the ordinary structural member made of steel or reinforced concrete. One of the main advantages is the interaction between the steel tube and concrete. Concrete delays the steel tube’s local buckling, whereas the steel tube confines the concrete and thereby increases the concrete’s strength. CFSTs are economical and permit rapid construction because the steel tube serves as formwork and reinforcement to the concrete fill, negating the need for either. The deformation capacity of the system is increased by the combined action of the concrete fill with the thin, ductile steel tube. The concrete fill significantly increases inelastic deformation capacity and the compressive stiffness and load capacity of the CFST member. In building construction concrete filled steel tubes are very widely used for columns in combination with steel or reinforced concrete beam. In this work totally 9 specimens were tested out of which 3 specimens were empty steel tubes and remaining 6 specimens were concrete filled with different bonding techniques. As it is prefabricated time consumption will be less in construction practice and due to confinement more ductility is expected which is very useful in earthquake resistant structures. Load carrying capacity of CFST almost doubled in comparison with empty steel tubes. Ultimate load carrying capacity of concrete filled steel tube beams almost doubled compared to empty steel tubes. Compared to empty steel tubes, strength increase of 67.19%, 97.48% and 114.84% was observed in normal CFST, CFST with sand blasting and CFST with diagonal shear connector beams respectively. Average ultimate load of EST was 105.66kN whereas average load of CFSTB, CFSTBWSB and CFSTBWDSC was 176.66, 208.66 and 227kN respectively. The maximum load was taken by the specimen CFSTBWDSC – 03 which was 231kN, it may be because of presence of diagonal shear connector inside the tube.

Design and Manufacturing Loading Rig Machine for Testing Screw Pile Models

The main objective of this paper is to design, manufacturing and testing of new loading rig machine to install and testing (i.e. compression and tension load capacity) of screw pile models in both cohesive and cohesionless soil layers. The mainframe was fabricated from thick steel sections, 8mm steel plates that welded together to construct a heavy and strong frame, that able to resist the expected loads during installation (linear and rotational movement at the same time) and testing of the screw pile models (model of loading test). Two independent gearbox motors (actuators) are used to supply the rotational and vertical movement. To provide precise control of velocity, the master gearbox motor, that can convert the rotary motion to a linear motion for vertical displacement along two screw bars via two ball screw systems, and four stainless guided rods to prevent rotation or inclination the bearing plate (rig) which manufactured from high stiffness stainless-steel was used. The second gearbox motor (‘slave’) mounted on the bottom loading plate that rotates the multi-plate screw pile. It was observed that the measured compression and tension load capacity of screw pile models illustrated the actual behavior of such kind of piles and this machine can be used in both conventional piles (i.e. pipe piles) and screw pile model.

Preliminary Analysis of the Influence of Reinforced Mortar Coating on the Compressive Strength of Clay Bricks

Introduction: This paper presents an extensive characterisation of materials and components used in non-structural masonry constructions in the region of Pernambuco, Brazil. Methods: An experimental study was carried out on a running bond of red clay prisms, of two and three ceramic blocks, with and without cement mortar coating, subjected to axial compression in order to enhance the capacity of masonry. Results and Conclusion: The experimental preliminary results indicate an increase both in the compressive load capacity of the coated prisms and in those that use coatings based on reinforced mortar, not complying with the specifications of conventional structural mortar.

The Effect of Local Fuse on Behavior of Concentrically Braced Frame by a Numerical Study

The concentrically braced frames (CBFs) are one of the most widely used lateral load-resisting systems. Seismic performance of these structures has a weakness that is due to the brace buckling at a lower loading than the ultimate compressive loading capacity. In this paper, attempt is made to enhance the seismic response of CBFs through utilizing a local fuse. For this purpose, first the formulation of fuse area and length are presented. Then based on this formulation, several numerical models have been built and analyzed to examine the effect of implementing this fuse on seismic response of CBFs. From the analyses results, it is found that if the reduced cross-section fuse (RCF) is properly designed and also the end of brace is fixed, the CBFs with equal energy dissipation capacity, that are equipped with this fuse exhibit a better ductility than the customary CBFs.

A critical assessment of the compressive behavior of reinforced recycled aggregate concrete columns

This paper presents a critical assessment of the compressive behavior of reinforced recycled aggregate concrete (RRAC) columns. Previous research has demonstrated that recycled aggregate concrete (RAC), manufactured using crushed concrete aggregates obtained from construction and demolition waste, can be a feasible and environmentally friendly alternative to conventional concrete for the use in structural applications. Currently, very limited information is available in the literature about the methods to be used for designing RC elements manufactured with recycled concrete aggregates. With the aim of extending the available experimental data, a fiber section based nonlinear finite element (FE) model was developed so as to provide in-depth insights into the compressive behavior of RRAC columns. First, a comparison between simulation results of the compressive behavior of RRAC columns and available experimental results were made to validate the FE model. Then, using the validated FE model, a parametric study was performed to investigate the effects of different recycled concrete aggregate (RCA) contents, volumetric ratio and yield strength of longitudinal steel reinforcement, and spacing and yield strength of transverse steel reinforcement on the compressive behavior and load capacity of RRAC columns. Finally, based on the limited available experimental database, a grey correlation analysis was used to evaluate the parametric sensitivity of the compressive behavior of RRAC columns. The experimental and numerical investigations demonstrate that the method used for considering the additional water absorption of RCAs in manufacturing RAC has a significant influence on the compressive load capacity of RRAC columns and that the influence of the RCA content on the compressive load capacity of RRAC columns is lower when compared with other important parameters but this effect should not be ignored in modeling the behavior of RRAC columns.

Effect of PWHT with Sheet-Type Ceramic Heater on Compressive Behaviors of Non-Stiffened Welded Steel Box Columns

A series of fundamental experimental investigation was conducted in order to examine the effect of PWHT by sheet-type ceramic heater on the residual stress, deformation and compressive behavior of non-stiffened welded box columns. The sheet-type ceramic heater was able to control the required temperature history for PWHT with high accuracy. The welding-induced tensile and compressive residual stresses of the specimens were reduced by 90% and 76% respectively with PWHT. Besides, PWHT could reduce the welding-induced out-of-plane deformation by 22%. It was revealed that the PWHT specimens had a slight higher stiffness than the As-welded specimens when applying monotonic static compressive load on both As-welded and PWHT specimens. They could also enhance the ultimate compressive load capacity about 32% of that of the As-welded specimens. The effectiveness of PWHT with the sheet-type ceramic heater could be confirmed.

Capacity of steel CHS X-joints strengthened with external stiffening rings in compression

This paper studies steel circular hollow section (CHS) X-joints by conducting experiments on the axial compressive strength of unreinforced and reinforced X-joints with external stiffening rings. Three pairs of unreinforced and reinforced X-joints were tested to compare their compressive load capacity. The diameter ratios (β) between the brace and the chord β were 0.25, 0.51 and 0.73 respectively. The experimental setup, parameters and results are presented. The failure modes and load-displacement curves of the unreinforced and reinforced X-joints were compared. It was shown that external stiffening rings greatly increased the axial compressive load capacity of the X-joints, by 86%, 75%, and 58% respectively. Finite element modelling accurately predicted the structural responses of the X-joints with and without external stiffening rings.

Stress-transfer in concrete encased and filled tube square columns employed in top-down construction

Top-down construction is a construction technique in which pit excavation and structure construction are conducted simultaneously. Reducing construction time and minimizing noise and vibration which affect neighboring structures, the technique is widely employed in constructing downtown structures. While H-steel columns have been commonly used as core columns, concrete filled steel tube (CFT) columns are at the center of attention because the latter have less axial directionality and greater cross-sectional efficiency than the former. When compared with circular CFT columns, square CFT columns are more easily connected to the floor structure and the area of percussion rotary drilling (PRD) is smaller. For this reason, square CFT columns are used as core columns of concrete encased and filled square (CET) columns in underground floors. However, studies on the structural behavior and concrete stress transfer of CET columns have not been conducted. Since concrete is cast according to construction sequence, checking the stress of concrete inside the core columns and the stress of covering concrete is essential. This paper presents the results of structural tests and analyses conducted to evaluate the usability and safety of CET columns in top-down construction where CFT columns are used as core columns. Parameters in the tests are loading condition, concrete strength and covering depth. The compressive load capacity and failure behavior of specimens are evaluated. In addition, 2 cases of field application of CET columns in underground floors are analyzed.

The importance of loading the periphery of the vertebral endplate.

Commercial fusion cages typically provide support in the central region of the endplate, failing to utilize the increased compressive strength around the periphery. This study demonstrates the increase in compressive strength that can be achieved if the bony periphery of the endplate is loaded. Sixteen cadaveric lumbar vertebrae (L1-L5) were randomly divided into two even groups. A different commercial mass produced implant (MPI) was allocated to each group: (I) a Polyether-ether-ketone (PEEK) anterior lumber inter-body fusion (ALIF) MPI; and (II) a titanium ALIF MPI. Uniaxial compression at a displacement rate of 0.5 mm/sec was applied to all vertebrae during two phases: (I) with the allocated MPI situated in the central region of the endplate; (II) with an aluminum plate, designed to load the bony periphery of the endplate. The failure load and mode of failure was recorded. From phase 1 to phase 2, the failure load increased from 1.1±0.4 to 2.9±1.4 kN for group 1; and from 1.3±1.0 to 3.0±1.9 kN for group 2. The increase in strength from phase 1 to phase 2 was statistically significant for each group (group 1: P<0.01, group 2: P<0.05, paired t-test). There was no significant difference between the groups in either phase (P>0.05, t-test). The mode of failure in phase 1 was the implant being forced through the endplate for both groups. In phase 2, the mode of failure was either a fracture of the epiphyseal rim or buckling of the side wall of the vertebral body. Loading the periphery of the vertebral endplate achieved significant increase in compressive load capacity compared to loading the central region of the endplate. Clinically, this implies that patient-specific implants which load the periphery of the vertebral endplate could decrease the incidence of subsidence and improve surgical outcomes.