Ultimate Shear Research Articles

Multimode coupled failure assessment of an LNGC cargo containment system considering flexible boundary condition

In recent years, there has been a demand for the large-scale membrane type LNGC due to the energy crisis. The cargo containment system (CCS) attached to the LNGC cargo tank is directly exposed to the sloshing load. Different pressure distribution forms may cause different failure modes of insulation box. The separate analysis of a single component or a single failure form cannot fully reflect the strength of CCS. Besides, the traditional numerical model with single insulation box and simply supported condition may overestimate the strength. In this study, a refined CCS numerical model attached to the inner hull structure is proposed. The deformed hull structure under sloshing impact is taken as the flexible boundary condition of CCS. The ultimate shear, bending, crushing and buckling strengths of NO96 CCS are assessed under various structures and boundary conditions. Finally, the multimode coupled analysis is conducted to fully assess the failure of CCS. The results show that the increase of structural stiffnesses can directly improve the ultimate strength. The weak structural and supporting stiffnesses make the buckling failure of insulation box become the most dangerous failure mode. The support from the strong hull structure leads to the shear failure of primary bottom plate. In the rest of loading conditions, the bending failure of primary horizontal plates need to be focused.

Sustainable construction material: Ultra-high performance fibre reinforced concrete (UHPFRC) for railway bridges in Malaysia

UHPFRC is a new concrete technology being used in many countries including Malaysia. UHPFRC favourable material properties open up new potential for precast options in bridge construction and have been widely used as beams for highway bridges in Malaysia. Nevertheless, PRC beams were preferred despite heavy in weight and large sections although these properties affect the design of the bridge substructure as well the cost of construction. This research is to review the applicability of Grade 140/155 UHPFRC beam for railway bridges in Malaysia. Laboratory tests for mechanical properties of UHPFRC were conducted and results were verified and complied with the French Standard, NF P18-470: 2016. The characteristic cylinder and cube compressive strengths were 151 and 155 MPa while the tensile limit of elasticity, post-cracking tensile strengths and modulus of rupture were 7.8, 8.4 and 24.3 MPa respectively. Structural analysis and design as per NF P18-710: 2016 requirement was then performed for a 15 meter UHPFRC IB650 beam to justify its applicability against a Grade 40/50 PRC U-beam of an existing railway bridge in which the ultimate shear and moment capacities of both beams were compared. The ultimate shear and moment capacities of the 4 numbers of U-beams/deck were 4,092 kN and 13,324 kNm respectively and when compared to UHPFRC IB650 beam, six numbers/deck were required with ultimate shear and moment capacities of 4,836 kN and 14,574 kNm respectively. For durability, the modulus of elasticity and depth of water penetration for UHPFRC were 50.8 GPa and 2mm respectively compared to 34 GPa and 11mm for Grade 40/50 concrete.

Study of Applicability of Triangular Impulse Response Function for Ultimate Strength of LNG Cargo Containment Systems under Sloshing Impact Loads

The LNG cargo containment system used in membrane-type LNG cargo tanks must have sufficient dynamic strength to withstand the impact of sloshing loads. However, performing direct dynamic nonlinear transient finite element assessments against design sloshing impact loads with different design specifications can be complicated and time-consuming. To address this, it is effective to use linear superposition methods, such as the triangular impulse response function (TIRF) method, to conduct dynamic transient FE assessments of LNG cargo containment systems. However, as LNG cargo containment systems have a high level of nonlinearities in terms of geometry, material, and boundary effects, it is necessary to evaluate the applicability of the TIRF method in advance. This study investigates the dynamic responses of an LNG cargo containment system using the TIRF method and compares the ultimate value of the structural responses and impulses with that obtained using direct dynamic nonlinear transient assessments. Based on a comparison of a series of FE analyses, the study proposes a design for the partial safety factors for calculating the ultimate bending and shear capacities of an LNG cargo containment system, taking into consideration the dynamic impact of sloshing loads using the TIRF method. Finally, the ultimate shear and bending capacities are calculated using the proposed method and compared with those obtained through direct dynamic nonlinear transient assessments. The results show that the proposed method provides conservative estimates against direct nonlinear finite element simulations, with a difference of around 10% for the mean minus two standard deviations. This approach can be practically applied for early basic design purposes in the shipbuilding industry.

Geotechnical properties and microanalyses of marble dust-bentonite as an alternative geomaterial of sand-bentonite mixes

ABSTRACT The present works have been aimed to investigate the potential of marble dust (i.e. a waste material obtained as a by-product from the marble industry) as a replacement of sand to achieve the desired geotechnical properties for its possible use as a geomaterial. Hence, marble dust (MD) is amended with a wide range of Bentonite (B) content (up to 95%) to examine the geotechnical properties [i.e. Atterberg’s limits, free swell indexes, compaction characteristics, California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS), and shear strength]. The efficacy and potential of MD-B mixes are confirmed by validating the geotechnical properties of sand (S)-bentonite (B) mixes. Results revealed that the geotechnical properties of MD-B mixes are observed to be comparable with S-B mixes. However, the amendment of MD and S with 60% B has been observed to be most beneficial in terms of achieving the ultimate CBR, UCS, and shear strength values. Thus, it is concluded that MD can be used as an alternative geomaterial to the sand with bentonite. Further, microanalyses [X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDAX), Fourier Transform Infrared Spectroscopy (FTIR) and Thermal Analysis (TA)] and physicochemical are performed to elucidate the results.

Comparison of the design of composite prestressed concrete hollow-core floor units between Eurocode 2 and ACI 318

A typical 1200 mm (48 in.) wide × 200 mm (8 in.) deep prestressed concrete hollow-core floor unit is analyzed and designed as a composite slab with a 75 mm (3 in.) deep structural topping to make a comparison between Eurocode 2: Design of Concrete Structures (EC2-1-1) and the American Concrete Institute’s Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary (ACI 318R- 08). This is the second of two papers. The first was published in PCI Journal in the March–April 2021 issue and designed a noncomposite hollow-core unit. The present comparison includes two-stage composite service and ultimate moments of resistance, ultimate composite shear capacities, camber and deflections, and interface shear between the hollow-core unit and cast-in-place concrete topping. Precast concrete cylin­der strength was 40 N/mm2 (5800 psi) and the cast-in-place concrete topping was 25 N/mm2 (3625 psi). The hollow-core unit was pretensioned using 10 number seven-wire helical strands. Worked examples are pre­sented in parallel formation for EC2 and ACI 318.

Transient response analysis of sandwich composite panel

In order to introduce a novel way relied on enhancing structural design as well as utilizing advanced material for protecting nonmetallic structures from detrimental impacts of transient thermal shock, this research analyzes the transient coupled thermo-elasticity response of the sandwich cylindrical panel with nanocomposite face-sheets strengthened with the functionally graded distributions of graphene-platelets affected by thermal shock loading. To determine the performance of the simply-supported system in the content of the time-altering stresses and deflections, the analytical solving approach, according to the broadly-known Navier technique, is applied to the governing equations developed on the bases of the exact theory of elasticity. It is considered that the internal surface of the panel is thermally isolated, while the outer surface is affected by thermal shock. The energy balance relation specified for this thermal boundary condition is solved to acquire the temperature gradient. Inverting the Laplace transform would be done with the aid of Dubner and Abates’ technique to designate time-history of displacements, shear stresses, and temperature distribution. The Halpin-Tsai micromechanics adjusted for nanocomposites is utilized to calculate thermoelastic properties of the nanocomposite face-sheets. The obtained numerical outcomes revealed the growth of the geometrical factor called mid-radius to thickness ratio leads to higher ultimate temperature and lower transverse shear stress.

Post-buckling shear resistance of slender girder webs: Stiffener participation and flange contributions

A series of validated finite element models are used to parametrically evaluate the participation of flanges and transverse stiffeners in the post-buckling web shear mechanics of welded I-shaped steel plate girders. The models are validated against the results of six large-scale web shear-buckling tests from the existing literature on highly slender plate girders (with web slenderness ratios of 250–267) and varying transverse stiffener spacing (with web panel aspect ratios from 1 to 4). All girders exhibited a 3-stage web shear-buckling response: 1) an initial linear elastic stage, 2) a post-buckling stage I during which shear stiffness begins to progressively decrease, and 3) a post-buckling stage II with either significantly reduced or negative stiffness after the buckled web panel has formed a yield mechanism. Increasing the flange thickness in a given girder configuration can change the mode of the post-buckling stage II response from gradual unloading (with ultimate shear reached at the end of post-buckling stage I) to positive hardening (with ultimate shear instead reached during post-buckling stage II at much larger displacement and with a 5–15% increase in shear resistance from the end of post-buckling stage I). At ultimate shear, the transverse stiffeners develop axial forces that equal only 10–30% of the applied shear load depending on their sizing, the panel aspect ratio, and the web plate thickness. The stiffeners are primarily engaged in the web's out-of-plane direction to impose panelization and less as an axial strut for the post-buckling load path.

A Comprehensive Flexural Analysis for Sustainable Concrete Structure Reinforced by Embedded Parts

In this research, the plate embedded parts and grooved embedded parts reinforced concrete structures were investigated. Two types of plate embedded parts and three types of grooved embedded parts experienced coating treatment to enable sustainable function. Later, the ultimate failure capacity by bending experiments was conducted and compared with the theoretically calculated results. Moreover, three grooved embedded parts were simulated by ABAQUS to compare the results with the experimental exploration results, which was in close agreement with the theoretically calculated results and finite element analysis results. The result indicated that the failure modes of the embedded specimens under the five working conditions are all concrete vertebral failure. The plate-type embedded components were proved to exhibit higher ultimate bearing capacity than the grooved embedded parts. Moreover, the flexural and shear capacity of these five types of embedded parts has not been fully developed. The ultimate flexural and shear capacity of these five types of embedded parts could be further explored by adjusting the higher concrete grade.

Tension-compression asymmetry and shear strength of titanium alloys

The relation between the tension-compression asymmetry (TCA) and shear strength in a wide variety of Ti alloys was examined. For this purpose, uniaxial tensile and compression, and double shear strength tests were performed on 13 Ti alloys, which have different microstructural phases (α, α+β, and β) and underwent different thermo-mechanical histories. Results show that the tensile-to-compressive yield strength and shear-to-tensile strength ratios of the alloys vary widely (between 0.79 to 1.24 and 0.52 to 0.86, respectively). A linear dependence between shear yield strength and tensile or compressive yield strength (whichever is lower) of all the alloys is found. While the ultimate shear and tensile strengths also show a linear dependence, data obtained on the fully β alloys are distinct. Finite element analyses employing the Drucker-Prager (DP) yield condition (to account for pressure-dependence on yield), Ludwick's strain hardening model, and Rice-Tracey failure criterion were performed to gain insights into the experimental trends. Results show that TCA decreases the shear yield stress while the shear strength is sensitive to the rate of hardening. A good correlation between the experimental and simulated shear-to-tensile yield strength ratios was observed. Based on a large, simulated dataset (generated using different combinations of material parameters), an empirical relation between shear strength, TCA, and tensile strengths was identified.

Engineering large, anatomically shaped osteochondral constructs with robust interfacial shear properties

Despite the prevalence of large (>5 cm2) articular cartilage defects involving underlying bone, current tissue-engineered therapies only address small defects. Tissue-engineered, anatomically shaped, native-like implants may address the need for off-the-shelf, tissue-repairing therapies for large cartilage lesions. This study fabricated an osteochondral construct of translationally relevant geometry with robust functional properties. Scaffold-free, self-assembled neocartilage served as the chondral phase, and porous hydroxyapatite served as the osseous phase of the osteochondral constructs. Constructs in the shape and size of an ovine femoral condyle (31 × 14 mm) were assembled at day 4 (early) or day 10 (late) of neocartilage maturation. Early osteochondral assembly increased the interfacial interdigitation depth by 244%, interdigitation frequency by 438%, interfacial shear modulus by 243-fold, and ultimate interfacial shear strength by 4.9-fold, compared to late assembly. Toward the development of a bioprosthesis for the repair of cartilage lesions encompassing up to an entire condylar surface, this study generated a large, anatomically shaped osteochondral construct with robust interfacial mechanical properties and native-like neocartilage interdigitation.

Experimental Study of Adobe Masonry and its Adherence with Reinforced Concrete Confinement Elements

The constructions with adobe masonry confined with concrete elements, experience a separation between them, mainly due to the inherent physical and chemical characteristics of both materials that are not very compatible with each other; adobe, a raw masonry with a high clay content, undergoes changes in its shape in the presence of humidity and temperature variation, which affects its adherence to concrete elements, compromising the confinement, function and stability of the walls. The different coefficients of expansion and contraction between concrete and adobe, added to their physical properties, make it difficult to achieve adequate adherence between these two materials. In the present study, 6 mixtures of earth (adobe) were designed, with different granulometry proportions to measure the adherence between adobe and concrete, identifying the most suitable one with the purpose of using it as a bonding material in walls for houses, from this study, with the best response being the sample MA-3. The test methodology was based on standards applicable to concrete and annealed brick masonry, as there is no available one for this material. Thirty-six adobe specimens adhered to concrete were tested, to which a normal load was gradually applied to their cross section, to a piece of adobe between two pieces of concrete, recording the ultimate horizontal shear stress between both materials. The scope is considered the result of the test of adobe pieces adhered to concrete subjected to horizontal shear force, considering different granulometry in the composition of the adobe mixture. This work provides a starting point for the standardization of the test and the justification of the need for an additional element that contributes to the confinement.

Mechanical response of a metastable austenitic stainless steel under different deformation modes

The deformation behaviour of AISI 304L stainless steel was examined under uniaxial tension and shear deformation modes in the temperature range of 0–500°C. A linear relationship between the tensile and shear yield stresses was observed over the whole temperature range, which was in a good agreement with the predictions of the von-Mises criterion. The relationship between the ultimate shear and tensile strength values, however, showed three distinct temperature-dependent regimes. In the temperature ranges corresponding to the transformation-induced plasticity effect and the dynamic strain aging phenomenon, a deviation from the expected behaviour was observed, which was related to the dependency of these phenomena on the loading mode.

Experimental study on the influences of different surface treatment processes and adhesive type on the aluminum adhesive-bonded joint strength

Surface roughness obtained from different preparation processes such as sanding, shot blasting, and sand blasting were considered in this study. The effects of surface roughness on shear strength of single-lap adhesive joint were examined. 2024-T3 aluminum sheets were cut into standard pieces and then sanded with seven sandpapers with different mesh, shot blasted for four different duration times and sandblasted under four different pressures. Pairs of prepared surfaces were attached using Araldite 2015 adhesive with high viscosity and HPL1012/HPH112 epoxy adhesive with low viscosity. Results show that the ultimate lap shear strength of the sanded samples initially increase and then decrease as surface roughness is increased. The lap joint strength continuously increases as the surface roughness of shot blasted and sand blasted samples are increased. In sanding, the optimum surface roughness is different for both high and low viscosity adhesives. However, for shot blasting and sand blasting, the optimum surface roughness is the same for both adhesive types. The maximum ultimate lap shear strength of joints for both types of adhesives obtained for sand blasting under 0.6 MPa pressure with 0.6 μm surface roughness.

Collapse of a high-rise building with pretensioned high-strength concrete piles

On 27 June 2009, a 13-storey building founded on pretensioned spun high-strength concrete piles suddenly collapsed in Shanghai, China. Prior to the collapse, an underground garage was excavated to the south of the building while excavated soil was dumped to its north side and formed a 10 m high fill slope. A comprehensive field investigation was carried out to collect physical evidence relating to the sudden collapse, particularly damage to building piles. The ultimate bending moment and shear capacities of this type of pile were determined through a series of full-scale tests to assist in evaluating failure patterns. Likely factors that could have influenced the collapse – namely, geotechnical pile failure, adjacent excavation and excessive surcharge – were tested by carrying out calculations, three-dimensional centrifuge tests and finite-element analysis. This paper reports on the forensic investigation process, the findings of the investigation and the most likely collapse mechanism. Lessons learned from the accident and recommendations to avoid a similar collapse in the future are also presented.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ПРЕДВАРИТЕЛЬНО НАПРЯЖЕННЫХ БЕЗ СЦЕПЛЕНИЯ ЖЕЛЕЗОБЕТОННЫХ ПЛИТ ПРИ ПРОДАВЛИВАНИИ

In this paper there are results of a punching shear test of slab samples, which were modeling post-tensioned reinforced concrete floor slabs when they are punched by columns. Geometrical dimensions of slab samples and properties of used materials are listed as well. There were 4 series of samples which differed to each other by level of prestress. Load have been applied through stamps of several types, which have allowed to research different positions of tensioned reinforcement relatively to the punching pyramid. Obtained results are discussed. Recommendations, which compliance may allow to obtain positive effect in ultimate punching shear loads for unbonded post-tensioned slabs are given.

RCC Highrised Residential Buildings its Influence on Earthquake Loads

The present decade, high rise multi-storey buildings are subjected to many external effects such as earthquake, wind loads, tidal loads, etc., in most cases high rise buildings have more vulnerable to earthquake and wind loads. Most of the reinforced concrete multi-storeyed frame buildings were heavily damaged and many of them completely collapsed during due earthquakes. RC frame buildings were severely damaged due to various deficiencies when proper codal provisions are not designed. A study is need to study the behaviour of the RC framed structure under earthquake load to reduce the damage caused by earthquake forces In this investigation a RC framed building of G+20 storeyed is considered in several seismic zones under different soils as per Indian Standard code IS 1893(part1):2016, using STAAD. Pro V8i as software tool. Finally evaluate the ultimate Base shear using Equivalent static method and Response spectrum method addressing under design forces.

Effect of aspect ratio of footings on settlement response of geosynthetic-reinforced granular fill-soft soil system

In this paper, a simple mathematical model is used to study the effect of aspect ratio of footings on settlement response of unreinforced or geosynthetic-reinforced granular fill-soft soil system. The length-to-width ratio (aspect ratio) of footings is varied from 1.0 (square) to 3.0 (rectangular). The foundation model is formulated for single layer of reinforcement. Parametric studies are carried out for a range of shear modulus values of granular fill and ultimate bearing capacity values of soft soil. It is observed that the aspect ratio has significant effect on settlement response and mobilised tension in geosynthetic layer. Both settlement and mobilised tension below the loaded area increase with an increase in the aspect ratio of footing for a particular loading intensity with constant width of the footing and constant soil parameters. The effectiveness of the reinforcement in terms of settlement reduction decreases due to increase of aspect ratio. The settlement decreases with an increase in ultimate bearing capacity of soft soil or shear modulus of granular fill. However, the rate of reduction of settlement with an increase in ultimate bearing capacity or shear modulus decreases as the aspect ratio increases.

Punching Shear Strength Characteristics of Flat Plate Panels Reinforced with Shearhead Collars: Experimental Investigation

This paper presents an experimental investigation on the punching shear strength of reinforced concrete flat plate slabs with shearhead collars. Eight reinforced concrete slab specimens were casted and tested under static load test, the load was applied at the center of slab by 100x100 mm steel column. The effect of the shapes, diameter and number of stiffeners has been discovered for shearheads through studying its effect on the load-deflection behavior, ultimate capacity, cracking load, failure mode, stiffness, ductility and energy absorption of tested specimens. The experimental results indicates that using square shearhead had achieved a slight increase in punching shear strength about 3% over that circular shearhead using the same surface area. Also, utilize 550 mm shearhead diameter will contribute to increase the punching shear strength about 14.5%. The increase in the number of stiffeners in specimen (CS4) had reduced the ultimate punching shear capacity by 20.3% over reference specimen. The first crack was decreased from 12.5kN to 7.5kN, when increases the number of stiffeners from one to two. The cracking load was increased with the increase of the diameter of circular shearhead from 10kN to 15Kn in specimens of 336mm and 550mm respectively. The specimen with 336mm diameter and 30mm height circular shearhead achieved 427 kN.m energy absorption, it is higher than the energy absorption of reference specimen by 2.6%. Also, using two stiffeners improved the energy absorption by 110.2% higher than the specimen with one stiffener.

The Influence of Clamping Pressure on Joint Formation and Mechanical Performance of Ti6Al4V/CF-PEEK Friction-Riveted Joints.

This work aims at investigating the influence of pre-set clamping pressure on the joint formation and mechanical strength of overlapping direct-friction-riveted joints. A pneumatic fixture device was developed for this work, with clamping pressure varying from 0.2 MPa to 0.6 MPa. A case study on overlapping joints using Ti6Al4V rivets and woven carbon fiber-reinforced polyether-ether-ketone (CF-PEEK) parts were produced. Digital image correlation and microscopy revealed the expected compressive behavior of the clamping system and the continuous pressure release upon the joining process owing to the rivet plastic deformation and the polymer squeezing flow. Two preferential paths of material flow were identified through the alternate replacement of the upper and lower composite parts by a poly-methyl-methacrylate (PMMA) plate—the composite upward and squeezing flow between the parts which induced their separation. The ultimate lap shear forces up to 6580 ± 383 N were achieved for the direct-friction-riveted CF-PEEK overlap joints. The formation of a gap to accommodate squeezed polymer between the composite parts during the process had no influence on the joint mechanical performance. The increase in the clamping pressure for joints produced with a low friction force did not affect the joint-anchoring efficiency and consequently the joint strength. On the other hand, the combined effect of a high-friction force and clamping pressure induced the inverted bell shape of the plastically deformed rivet tip, a lower anchoring efficiency, and the delamination of the composite, all of which decrease the mechanical strength by 31%. Therefore, the higher the friction force and clamping pressure, the more defects would be generated in the composite parts and the more changes in the shape of the plastically deformed rivet tip, leading to a lower level of quasi-static mechanical performance. All the joints failed by initial bearing of the composite and final rivet pull-out. The findings of this work can contribute to further improvement of the clamping design for industrial application.

Flexural Behavior of Sandwich Structure with AA 8011 Honeycomb Core and Al 1100 Face Skins

This paper details the fabrication and flexural testing of sandwich structure with Aluminium honeycomb core with Aluminium face skins. The material for the face skin is aluminium 1100 and for the core is Aluminium AA8011. The cell size obtained by fabrication is 7mm. The specimen is prepared and tested as per the ASTM standard C393/C393M-11 on a three-point bending test to obtain the ultimate core shear strength and the face skin strength. Finite element analysis is also carried out to validate the experimental test.