Load-bearing Tests Research Articles

Design and performance of 3D-Printed ABS@rGO/CF/CeO2 composites for microwave absorption and mechanical strength

Traditional microwave absorbing materials struggle to balance wideband absorption with mechanical properties, particularly in multifunctional applications. This study explores the effects of short carbon fibers (CF), cerium dioxide (CeO2), and reduced graphene oxide (rGO) on the electromagnetic and mechanical properties of 3D-printed composites. The ABS@CF/CeO2/rGO composite with a thickness of 2.2 mm exhibited exceptional microwave absorption, achieving an effective absorption bandwidth (EAB) of 6.6 GHz and a minimum reflection loss (RLmin) of −40.9 dB. The Whale Optimization Algorithm (WOA) was employed to design a load-bearing, microwave-absorbing superstructure, which significantly improved wideband absorption. Experimental results confirmed the superstructure’s isotropy and wide-angle absorption capabilities. The calculated electromagnetic parameters were applied to evaluate the radar cross-section (RCS) of large targets, demonstrating enhanced stealth performance for unmanned aerial vehicles (UAVs). Mechanical tests revealed that rGO improved interlayer bonding strength, while CF negatively impacted bending performance. The superstructure also showed excellent mechanical stability in load-bearing tests, underscoring its potential for practical engineering applications. This study offers insights into designing advanced composite materials with balanced electromagnetic and mechanical properties, guiding future multifunctional material development.

Development of transparent soil grouting test system and its application in grouted gravel pile

To visualize the grouting process of grouted gravel piles, a transparent soil model test system was developed. This system allows for the study of soil movement around the piles during grouting reinforcement and enables load-bearing capacity testing after grout solidification into piles. The experimental system comprises a grouting system, a vertical load-bearing capacity testing system, a continuous physical field measurement system, and a model box. The grouting system facilitates sequential processes: pre-consolidation, constant-pressure grouting, and vertical loading. In transparent clay with a pre-consolidation pressure of 60 kPa, constant-pressure grouting and vertical load-bearing tests for grouted gravel piles were conducted. The results captured the disturbance deformation of the soil around the pile during both grouting and vertical loading. The study indicates that disturbance deformation of the soil surrounding the pile increases with prolonged grouting time. Soil beneath the pile end predominantly undergoes vertical compression, while soil at the pile sides experiences horizontal compression. The mid-section of the soil adjacent to the pile displays oblique upward bulging and vertical deformation. Under constant-pressure grouting, the filling rate of gravel voids in the pile hole by epoxy resin chemical grout with strong time-dependent viscosity shows a decreasing trend. During vertical loading, the displacement of the soil around the pile is significantly greater than that at the pile end. Consequently, this test system facilitates the visualization and simulation of grouting and vertical load-bearing tests for grouted gravel piles.

Load-bearing tests and simulation analysis of compacted loose snow

To explore the load-bearing capacity of compacted loose snow, a loading experimental equipment was developed. Load-bearing tests and finite element simulation research on compacted loose snow were conducted. The research shows that the compacted loose snow undergoes punching shear damage under vertically uniform loads. The P-s curve demonstrates three phases, corresponding to slow development, rapid development, and failure stages respectively. Based on this, a relationship between the critical edge load Pcr and ultimate load Pu of the compacted snow and the unconfined compressive strength fu were proposed. Under vertically uniform loads, the snow's deformation depth increases with the density, and the bearing plate's width has a minimal effect on deformation depth. The comparison between the simulation and theoretical conclusion reveals that Boussinesq's stress solution is applicable for analyzing the additional stress in low-density snow. The results are helpful for the scientific understanding of the load-bearing capabilities of compacted snow and snow engineering.

Experimental study on Q355 steel T-stubs connected through high-strength ring groove rivets

High-strength ring groove rivet connections have several advantages over bolt connections, including anti-loosening performance and high fatigue resistance. This research aims to investigate the mechanical properties of high-strength ring groove rivet assemblies and load resistances of riveted T-stubs. Experimental tests on high-strength ring groove rivet assemblies were firstly carried out, including coupon tests, preload measurements, and load-bearing tests. Q355 steel T-stubs connected through ring groove rivets were subsequently tested. The effects of certain geometrical parameters and material grades of the rivets on the performance of the T-stubs were analyzed. The applicability of the Eurocode 3 and Demonceau methods to the T-stubs was discussed. The results show that the Grade 10.9 rivet possesses higher yield strength and strain, and lower ultimate strain, in comparison to the Grade 8.8 rivet. Increasing the diameter of the rivet is beneficial for the T-stubs, whereas increasing the flange thickness is not always advantageous. The Eurocode 3 method is unsuitable for the T-stubs connected through ring groove rivets, whereas the Demonceau method is conservative. The findings of this research provide guidance for engineering designs of high-strength ring groove rivet assemblies and steel T-stubs connected through ring groove rivets.

An experimental study on parabolic trough solar cookers with materials collector of chrome stickers and glass mirrors

Cooking, a fundamental human necessity, frequently relies on environmentally harmful energy sources. Concentrated solar power offers a promising solution through solar cookers to address this issue. This study assesses a Parabolic Trough Collector (PTC) solar cooker's performance with two reflector materials: chrome stickers and glass mirrors. The PTC-type solar cooker comprises essential components, including an absorber tube, a flexible conduit, and a spiral-shaped cooking container holder that accommodates a diverse range of cooking vessels. In the configuration of the PTC collector, reflectors fabricated from chrome stickers and glass mirrors are strategically employed to harness and concentrate solar radiation effectively. The absorber tube, crafted from copper, is filled with a heat-transfer fluid consisting of soya oil. Experimental investigations were conducted in a two-stage process, encompassing trials without any applied load and subsequently with varying loads. In the no-load experiments, alterations were made to the PTC collector's inclination angle, spanning the ranges of 15º, 20º, 25º, and 30º. In contrast, the load-bearing tests encompassed the assessment of the PTC solar cooker's performance under a diverse array of cooking scenarios, including boiling water, heating oil, frying eggs, and crisping crackers. The evaluated parameters encompassed key metrics such as incident solar radiation (Ir), ambient temperature (Ta), receiver temperature (Tr), fluid temperature (Tf), spiral furnace temperature (Tsf), and load temperature (To). Subsequently, the outcomes of the experiments were employed to determine the efficiency of the solar cooker. Analysis of the no-load test results indicates that the most favorable performance, as observed in the parameters Tr, Tf, and Tsf, is achieved at a collector inclination angle of 15º for both chrome sticker and glass mirror reflector materials. The solar cooker demonstrated commendable proficiency in boiling water, heating oil, frying eggs, and crisping crackers, accomplishing these tasks within a time frame ranging from 5 to 20 minutes. Notably, the solar cooker featuring the glass mirror reflector exhibited a superior thermal efficiency of 33.7%, surpassing the efficiency of the counterpart with the chrome sticker reflector, which registered an efficiency of 30.9%. These findings underscore the efficacy of the glass mirror reflector in harnessing solar energy for enhanced cooking performance within this solar cooker configuration.

Deck Slab Elements for the Accelerated Construction of Steel–Concrete Composite Bridges

Various methods have been developed to produce deck slabs for steel–concrete composite bridges. Usually, the deck slabs are cast with in situ concrete using a formwork carriage, resulting in construction progress of 15 to 25 m of deck slab per week. A new construction method was developed at the Institute of Structural Engineering (TU Wien), which enables the swift erection of the concrete deck slab. This method employs precast deck slab elements with reinforced concrete cross-beams which span in the transverse direction. With this new construction method, producing up to two deck slab sections of 15–25 m per day becomes possible. Further, the performance of novel reinforcement detailing required for the precast deck slab elements is investigated by structural testing. The experiments consist of eight load-bearing tests on four specimens which represent sections of the element during casting and after completion. The investigated parameters in series 1 are the length and spacing of loops, used for protruding longitudinal bars enclosure. In series 2, the enclosure of the shear reinforcement and the height of the cross beams are varied. The results show that the targeted bending capacity could be reached in all tests with no signs of premature failure due to detailing reasons. Based on the experimental results, the feasibility of the new approach is shown and recommendations for detailing are given.

Travelling through the Natural Hierarchies of Type I Collagen with X-rays: From Tendons of Cattle, Horses, Sheep and Pigs.

Type I collagen physiological scaffold for tissue regeneration is considered one of the widely used biomaterials for tissue engineering and medical applications. It is hierarchically organized: five laterally staggered molecules are packed within fibrils, arranged into fascicles and bundles. The structural organization is correlated to the direction and intensity of the forces which can be loaded onto the tissue. For a tissue-specific regeneration, the required macro- and microstructure of a suitable biomaterial has been largely investigated. Conversely, the function of multiscale structural integrity has been much less explored but is crucial for scaffold design and application. In this work, collagen was extracted from different animal sources with protocols that alter its structure. Collagen of tendon shreds excised from cattle, horse, sheep and pig was structurally investigated by wide- and small-angle X-ray scattering techniques, at both molecular and supramolecular scales, and thermo-mechanically with thermal and load-bearing tests. Tendons were selected because of their resistance to chemical degradation and mechanical stresses. The multiscale structural integrity of tendons' collagen was studied in relation to the animal source, anatomic location and source for collagen extraction.

Experimental Study on Prestressed CFRP-reinforced Aluminum Alloy Bridge Panel Based on Shape Memory Alloys

In order to strengthen aluminum alloy bridge panels, a CFRP (Carbon Fibre Reinforced Plastics) plate is tensioned under the bottom plate to exert prestress. Installing the tensioning device under narrow bottom plates of bridge panels via traditional prestressing method is difficult; therefore, a new prestress tensioning technology based on Shape Memory Alloy (SMA) is employed to efficiently apply the prestress. The tensioning and anchorage device used in prestressing technology has been designed and manufactured. A tensile stress of 360Mpa was applied to the CFRP plate with the tensioning and anchorage device and then, load-bearing tests were performed on prestressed reinforced aluminum alloy and unreinforced bridge panels, respectively. Experimental results showed that the proposed CFRP prestressing technology was feasible and verified the application possibility of SMA as a prestress device in practical engineering. The new technology ensured that the desired prestress value was applied to aluminum alloy bridge panel and the strength and stiffness of aluminum alloy bridge panels reinforced with the proposed technology were significantly improved.

Process-induced damage and its effect on strength of composite - aluminum alloy joint by FDS technique

Flow drilling screw (FDS) is a novel joining technique that enables high-speed joining of dissimilar metals with one-shot process of hole machining, female thread forming and fastening from one side. The damage after FDS process and its effect on joint strength and fracture behaviour near the screw by load-bearing tests for FDS joints between aluminum alloy and carbon fibre reinforced thermoplastics (CFRTP) are evaluated. Cross-sectional observation after joining process reveals that delamination in CFRTP is clearly suppressed and matrix resin is filled in the screw thread compared to the case with CFRP using thermosetting resin. In the joint strength test with shear loading and the cross-shaped tensile tests where the screw is pulled out in its axial direction, only the fibre micro-buckling is observed until fracture. These experimental results recommend that CFRTP laminates should be applied as composite side since this technique utilizes frictional heat by the screw that can contribute to plastic flow or deformation of the thermoplastic resin with high fracture toughness. It is also clarified that damage growth is further suppressed by using CFRTP/Al hybrid laminates where aluminum alloy sheets are inserted between CFRTP plies, which leads to improve the joint strength.

3D printed lightweight metastructure with microwave absorption and mechanical resistance

Recently, lightweight multifunctional metastructures have attracted significant attention owing to its advantage of integrating microwave absorption and mechanical resistance. However, these features are typically entangled, and a feasible strategy for independently manipulating the microwave absorption and mechanical resistance is still lacking. Herein, a double high-impedance surface-loaded honeycomb (DHHC) is proposed, based on a theoretical analysis, and fabricated using a 3D printing technique. The impedance and surface current distribution of the DHHC were analyzed and investigated to achieve broadband microwave absorption characteristics. The structural parameters and resistances of the high-impedance surface were investigated and optimized to regulate the absorbing bandwidth and reflectivity intensity. Our experimental results indicated that a 4.25 mm thick DHHC metastructure can achieve a –10 dB absorbing bandwidth at a frequency range of 6.73–18 GHz, as well as a –15 dB absorbing band at 8.42–14.75 GHz. Moreover, the structural parameters of the honeycombs were investigated for the adjustment of stress distributions during the compression and flexural processes. Load-bearing tests indicated that the DHHC possessed a mechanical resistance with an equivalent areal density of 2.32 kg/m2. This study provides a promising route for achieving independently manipulated compatibility between microwave absorption and mechanical resistance for practical applications.

Exploratory Study on the Load-Bearing Behaviour of Laminated Glass Beams Exposed to Fire

All-glass structures have become increasingly popular with architects and builders in recent years. Glass surfaces are becoming larger and more impressive, while connections are being decreased to obtain maximum transparency. The supporting structure of glass facades, glass roofs or walk-on glazing is mostly made of metal. One of the reasons for this are the fire protection requirements. To increase the overall transparency load-bearing glass structures have recently been given more attention. However, their use is currently still limited due to the concerns about glass performance in case of fire. Within a research study at TU Dresden load-bearing tests in a furnace were carried out to examine the load-bearing behaviour of glass beams exposed to fire. Different glass types and interlayer materials were tested with varying loads. This study provides a closer look at fire performance of glass beams and proposes further examinations to increase the load-bearing capacity in case of fire.

U-Type Honeycomb Based on Super-Elastic Shape-Memory Alloy for One-Dimensional Large Wing Morphing

Flexible skin is an important part of morphing wings, which must comply with the altered geometry during wing morphing. Especially for some applications of one-dimensional large morphing wing such as chord-change, flexible skin is demanded to be capable of large deformation. In this paper, we present a U-type honeycomb structure of shape-memory alloy (SMA) for flexible skin that can undergo large deformation owing to the super-elastic Nickel Titanium (NiTi)-SMA, and the mechanical properties are studied by numerical and experimental methods. In the stage of linear elasticity, U-type honeycomb structure is analyzed theoretically based on the virtual work principle, and its mechanical behavior in the stage of large deformation is studied by finite element method with considering geometric and material nonlinearity. In-plane tensile tests and out-of-plane load-bearing tests are performed, and the experimental results agree well with the numerical results. The experimental results have proved that the U-type honeycomb structure based on NiTi-SMA has large deformation capability, of which the recoverable global strain can reach at least 60%, and has great potential in the application of morphing wings.

Projection Image Interpolation for 4DCT Data using Optical Flow

Recent progress in additive manufacturing (AM) technology has made it possible to form objects with fine and complex internal structures. X-ray computed tomography (CT) is widely used for inspecting AM objects because it can scan objects’ internal structures nondestructively. Although conventional X-ray CT scanning scans static objects to obtain their three-dimensional geometry, recently, attention has been paid to scanning deforming objects in real time and obtaining time-varying fourdimensional (4D) data. This technology, called 4-dimensional computed tomography, is also used to conduct load-bearing tests of AM products and observation of the deformation of the internal structure of objects. However, dynamic deformation of an object to be scanned while rotating 360° yields a series (one frame) of projection images necessary to reconstruct a CT volume, causing blurs in the reconstructed data. Therefore, we propose an algorithm to generate a frame of projection images of an arbitrary time point by interpolating the projection images from the previous and next frames of continuous scanning. Specifically, we generate the projection images from given frames using optical flow, which adopts the vector field of the gradient of projection values. This algorithm was applied to dynamically changing projection images to experimentally show its robustness against dynamical changes.

Influence of heat treatment on the suitability for clinching of the aluminium casting alloy AlSi9

In many manufacturing areas, multi-material designs are implemented in which individual components are joined together to form complex structures with numerous joints. For example, in the automotive sector, cast components are used at the junctions of the body and joined with different types of sheet metal and extruded profiles. To be able to join structures consisting of different materials, alternative joining technologies have emerged in recent years. This includes clinching, which allows assembling of two or more thin sheet metal and casting parts by solely cold forming the material. Clinching the brittle and usually less ductile cast aluminium alloys remains a challenge because the brittle character of the cast aluminium alloys can cause cracks during the forming of the clinched joint. In this study, the influence of the heat treatment time of an aluminium casting alloy AlSi9 on the joinability in the clinching process is investigated. Specific heat treatment of the naturally hard AlSi9 leads to a modification of the eutectic microstructure, which can increase ductility. Based on this, it will be examined if specific clinching die geometries can be used, which achieve an optimized geometrical formation of the clinched joint. The load-bearing capacities of the clinched joints are determined and compared by shear tensile and head tensile tests. Furthermore, the joints are examined microscopically to investigate the influence of the heat treatment on the failure behaviour during the load-bearing tests as well as crack initiation within the joining process.

Stochastic approach for the material properties of reinforcing textiles for the design of concrete members

Textile-reinforced concrete has emerged in recent years as a new and valuable construction material. The design of textile-reinforced concrete requires knowledge on the mechanical properties of different textile types as well as their reinforcing behaviour under different loading conditions. Conventional load-bearing tests tend to be complex, time-consuming, costly and can even lack consistent specifications. To mitigate such drawbacks, a standardised tensile test for fibre strands was used to characterise the material properties needed for the design of a textile-reinforced concrete member. The standardised tensile test uses a fibre strand with 160 mm length, which is cut out of a textile grid. For the sake of this study, an epoxy resin-soaked AR-glass reinforcement was considered. The results show that the textile reinforcement has a linear-elastic behaviour, and the ultimate tensile strength can be statistically modelled by a Gumbel distribution. Furthermore, the results indicate that the modulus of elasticity is not influenced by the length or the number of fibre strands. Therefore, the mean value attained from the standardised test can be used for design purposes. These findings are essential to derive an appropriate partial safety factor for the calculation of the design values of the tensile strength and can be used to determine the failure probability of textile-reinforced concrete members.

Bearing Capacity of Jute Geotextile-Reinforced Sand Bed

This paper evaluates the optimum geometrical parameters of jute geotextile reinforcement for the load-bearing capacity based on the laboratory model tests carried out on 50, 100 and 150 mm diameter (D) circular footings resting on sand bed. These footing sizes were obtained using a scaling down factor of 4 for the prototype foundations so as to obtain the behavior of an actual prototype structure. Geotextile reinforcement was also scaled down using appropriate scaling factors. The natural jute geotextile reinforcement layers were placed as planar sheets and the optimum reinforcement geometrical parameters were evaluated using 150 mm diameter circular footing for the load-bearing capacity of sand. Further, the effect of the footing size on improvement of load-bearing capacity of both unreinforced and reinforced sand beds was brought out using circular footings of 50, 100 and 150 mm diameter. The experimental results showed that the optimum depth and vertical spacing of jute geotextile reinforcement layer(s) for the load-bearing capacity were found to be 0.31–0.32D and 0.28–0.3D, respectively, depending on the settlement criteria. The optimum width of reinforcement layer was found to be 3.5D, while the optimum number of reinforcement layers was found to be 4. The surface deformations are also in conformity with the optimum geometrical parameters obtained from the load-bearing tests. Further, the load-bearing capacity of unreinforced and reinforced sand beds increased with the increase in footing size. However, the bearing capacity ratio decreased with the increase in size of footing.

02.01: Development of a new design approach for weldings

ABSTRACTThe application of high strength steels provides economic and ecological advantages in many types of constructions, due to the resource‐conserving material use. However, for welded constructions, some of these advantages are partially offset by conservative design rules and more complicated execution regulations. The objective of the ongoing AiF‐FOSTA research project P1020 is the development of principles, which lead to significant improvements of design and execution rules for welded connections of high strength steel structures. The development of design rules aims at a simpler and economically more efficient execution. This paper gives an overview of the research project P1020, including the design model, the assessment of the welding processes and the parametric studies, consisting of load bearing tests and numerical simulations. It describes the development of the flat tensile test method for the assessment of the welding behaviour and the structural analysis of welded joints for parametric studies.

Failure mode dependent load bearing characteristics of mechanical clinching under mixed mode loading condition

Abstract The purpose of this study is to investigate the failure mode dependent the load bearing characteristics of the mechanical clinching under the mixed mode loading condition. The joint strength of the mechanical clinched joint was determined by the geometrical interlocking shape parameters, such as the neck thickness and undercut. The load bearing tests under the pure normal and shear mode loading condition were carried out to investigate the influence of the geometrical interlocking shape parameters on the failure mode of the mechanical clinching and its joint strength by analytical approach. The Arcan test apparatus was modified to realize the mixed mode loading condition on the cross-tension specimen. For each angular positions(α=0,15,30,45,60,75,90° ), the failure mode and strength of the mechanical clinched joint was evaluated by the cross tension specimen with the modified Arcan test apparatus. Based on the experimental result, an analytical expression was derived to describe the joint failure criterion under the mixed mode loading condition.

Fire Resistance of Timber Panel Structures Under Standard Fire Exposure

Timber panel construction using Cross-Laminated Timber (CLT) or Laminated Veneer Lumber (LVL) panels have been developed for cost and construction efficiencies in the building industry. The increased use of timber as a sustainable construction material in buildings is expected to expand the forest industry and increase carbon stock. Heavy timber structural elements with sufficient load bearing capacity could be used in tall buildings. However, sufficient data are not yet available to understand the structural and thermal behaviors of domestic timber panel elements with cross laminations/layers when they are exposed to fire. In this study, fire testing data for timber panels are obtained and the charring characteristics and failure modes of structural elements under standard fire exposure are investigated to develop a simple method for estimating the fire resistance of timber panels. Toward this end, a series of experiments consisting of heating tests and load bearing tests for walls in furnaces with various experimental parameters was conducted. The experimental parameters considered include the adhesive type, thicknesses of laminations and panels, wood species, fire protection, and applied loads of the panels. Experiments without loading showed that CLT and LVL panels and joints of panels with 135 mm thickness showed sufficient thermal insulation and integrity over 90 min in standard fire tests. Smoke leakage from the joints of the timber panels was observed in the early stage of the fire tests because of a lack of air-tightness. Delamination of almost all charred layers glued with an API adhesive was observed in fire tests of CLT panels; however, delamination of LVL and CLT panels with a RPF adhesive was limited. The estimated charring rates of a Japanese cedar CLT panel with API and RPF adhesives were 0.78 mm/min and 0.66 mm/min at 260°C, respectively. The charring rate of LVL panels was ∼0.6 mm/min at 260°C, less than that of CLT panels. The load bearing capacity of timber walls subjected to one-sided fire exposure depended on the buckling strength under the eccentric load caused by asymmetric charring. A prediction method based on the Secant formula was presented to estimate the buckling strength in fire tests. An equation that considered the effect of the degradation of elasticity at high temperatures and eccentricity of loading provided the approximate buckling strength of the timber panel specimens in the fire tests.

Dynamic telescopic craniotomy: a cadaveric study of a novel device and technique.

OBJECT The authors assessed the feasibility of the dynamic decompressive craniotomy technique using a novel cranial fixation plate with a telescopic component. Following a craniotomy in human cadaver skulls, the telescopic plates were placed to cover the bur holes. The plates allow constrained outward movement of the bone flap upon an increase in intracranial pressure (ICP) and also prevent the bone flap from sinking once the ICP normalizes. The authors compared the extent of postcraniotomy ICP control after an abrupt increase in intracranial volume using the dynamic craniotomy technique versus the standard craniotomy or hinge craniotomy techniques. METHODS Fixation of the bone flap after craniotomy was performed in 5 cadaver skulls using 3 techniques: 1) dynamic telescopic craniotomy, 2) hinge craniotomy, and 3) standard craniotomy with fixed plates. The ability of each technique to allow for expansion during intracranial hypertension was evaluated by progressively increasing intracranial volume. Biomechanical evaluation of the telescopic plates with load-bearing tests was also undertaken. RESULTS Both the dynamic craniotomy and the hinge craniotomy techniques provided significant control of ICP during increases in intracranial volume as compared with the standard craniotomy technique. With the standard craniotomy, ICP increased from a mean of 11.4 to 100.1 mm Hg with the addition of 120 ml of intracranial volume. However, with the dynamic craniotomy, the addition of 120 ml of intracranial volume increased the ICP from a mean of 2.8 to 13.4 mm Hg, maintaining ICP within the normal range as compared with the standard craniotomy (p = 0.04). The dynamic craniotomy was also superior in controlling ICP as compared with the hinge craniotomy, providing expansion for an additional 40 ml of intracranial volume while maintaining ICP within a normal range (p = 0.008). Biomechanical load-bearing tests for the dynamic telescopic plates revealed rigid restriction of bone-flap sinking as compared with standard fixation plates and clamps. CONCLUSIONS The dynamic telescopic craniotomy technique with the novel cranial fixation plate provides superior control of ICP after an abrupt increase in intracranial volume as compared with the standard craniotomy and hinge craniotomy techniques.