Non-load Bearing Research Articles

The innovative application of a novel bone adhesive for facial fracture osteosynthesis—in vitro and in vivo results

This study evaluates a novel adhesive fixation technique to affix cortical bone fragments to osteosynthesis plates using common PMMA cement. This technique utilizes a new amphiphilic bone bonding agent adhering with both hydrophilic bone and hydrophobic PMMA cement. After in vitro biomechanical testing of the bonding strength with explanted bovine and rabbit calvarian bone samples, osteosynthesis plates with screw holes of 1.3 and 1.5 mm were placed on the cranial bone of New Zealand white rabbits and the bond strength of these plates was determined through tension tests. In vitro bond strengths of 19.8-26.5 MPa were obtained. Control samples, prepared without a bone bonding agent, exhibited bone bonding strengths <0.2 MPa. In vivo respective bond strengths at the cranium of the white rabbits were 2.5-4.1 MPa 2 weeks post surgery and 1.9-2.5 MPa 12 weeks after implantation. This new innovative fixation method can be envisioned for cases in which conventional fixation techniques of screws and plates are insufficient or not possible due to the bone or trauma conditions. The observed bonding strengths support implementing this technique in nonload bearing regions, such as the central midface or frontal sinus, facilitating immobilization until bone reunion is complete.

Experimental studies of non-load bearing steel wall systems under fire conditions

Fire safety of buildings has been recognised as very important by the building industry and the community at large. Traditionally, increased fire rating is provided by simply adding more plasterboards to light gauge steel frame (LSF) walls, which is inefficient. Many research studies have been undertaken to investigate the thermal behaviour of traditional LSF stud wall systems under standard fire conditions. However, no research has been undertaken on the thermal behaviour of LSF stud walls using the recently proposed composite panel. Extensive fire testing of both non-load bearing and load bearing wall panels was conducted in this research based on the standard time-temperature curve in AS1530.4. Three groups of LSF wall specimens were tested with no insulation, cavity insulation and the new composite panel based on an external insulation layer between plasterboards. This paper presents the details of this experimental study into the thermal performance of non-load bearing walls lined with various configurations of plasterboard and insulation. Extensive descriptive and numerical results of the tested non-load bearing wall panels given in this paper provide a thorough understanding of their thermal behaviour, and valuable time-temperature data that can be used to validate numerical models. Test results showed that the innovative composite stud wall systems outperformed the traditional stud wall systems in terms of their thermal performance, giving a much higher fire rating.

The Evolving Dynamic Response of a Four Storey Reinforced Concrete Structure during Construction

Structures include elements designated as load bearing and non-load bearing. While non-load bearing elements, such as facades and internal partitions, are acknowledged to add mass to the system, the structural stiffness and strength is generally attributed to load bearing elements only. This paper investigates the contribution of non-load bearing elements to the dynamic response of a new structure, the Charles Institute, in the grounds of University College Dublin (UCD) Ireland. The vertical vibration response of the first floor and the lateral response at each floor level were recorded at different construction stages. The evolution of the structural response as well as the generation of a finite element (FE) model is discussed. It was found that the addition of the non-load bearing facades increased the first floor natural frequency from 10.7 Hz to 11.4 Hz, a change of ap- proximately +6.5%. Similarly these external facades resulted in the first sway mode having its frequency increased by 6%. The subsequent addition of internal partitions, mechanical services and furnishings resulted in the floor natural frequency reducing to 9.2 Hz. It is concluded that external facades have the net effect of adding stiffness and the effect of internal partitions and fur- nishings is to add mass. In the context of finite element modelling of structures there is a significant challenge to represent these non-structural elements correctly so as to enable the generation of truly predictive FE models.

The Evolving Dynamic Response of a Four Storey Reinforced Concrete Structure during Construction

Structures include elements designated as load bearing and non-load bearing. While non-load bearing elements, such as facades and internal partitions, are acknowledged to add mass to the system, the structural stiffness and strength is generally attributed to load bearing elements only. This paper investigates the contribution of non-load bearing elements to the dynamic response of a new structure, the Charles Institute, in the grounds of University College Dublin (UCD) Ireland. The vertical vibration response of the first floor and the lateral response at each floor level were recorded at different construction stages. The evolution of the structural response as well as the generation of a finite element (FE) model is discussed. It was found that the addition of the non-load bearing facades increased the first floor natural frequency from 10.7 Hz to 11.4?Hz, a change of approximately +6.5%. Similarly these external facades resulted in the first sway mode having its frequency increased by 6%. The subsequent addition of internal partitions, mechanical services and furnishings resulted in the floor natural frequency reducing to 9.2 Hz. It is concluded that external facades have the net effect of adding stiffness and the effect of internal partitions and furnishings is to add mass. In the context of finite element modelling of structures there is a significant challenge to represent these non-structural elements correctly so as to enable the generation of truly predictive FE models.

Manufacturing of High Toughness Hydroxyapatite Produced by Wet Chemical Method

Hydroxyapatite (HA) is among the leading ceramic materials for hard tissue replacement implants. Despite the excellent bioactivity of HA, low toughness has limited the application of these materials to non-load bearing areas. The sinterability of nanocrystalline hydroxyapatite (HA) powder via new heating profile for conventional pressureless sintering was studied. The starting nanocrystalline HA powder was synthesized by wet chemical precipitation method. After uniaxial pressing followed by isostatic pressing, HA powder compacts are sintered over the temperature range of 1000°C to 1300°C. Different holding time of 1 minute and 120 minutes was applied as a heating profile of HA samples. The results revealed that new heating profile was effective in producing a HA body with high density of 98% when sintered at 1200°C. Subsequently, mechanical properties such as fracture toughness and hardness, of HA compacts increased with decrease in grain size. HA showed the highest hardness of 9.51 GPa and fracture toughness of 1.41 MPa.m1/2 when sintered at 1100 °C. XRD analysis indicated that decomposition of HA phase during sintering at high temperatures do not occur. Short holding time leads to finer microstructure of HA and subsequently better mechanical properties.

Acute energy cost of multi-modal activity-based therapy in persons with spinal cord injury

ObjectiveTo examine acute energy costs of multi-modal activity-based therapy (ABT) in men and women with spinal cord injury (SCI).Study designDescriptive case series.SettingAn outpatient center in California.ParticipantsSeven men and women (age = 28.3 ± 11.6 years; duration of injury = 4.3 ± 2.5 years) with injury levels ranging from C5 to T8.InterventionActivity-based therapy.Outcome measuresOxygen uptake (VO2), energy expenditure (kcal/minute), SCI Metabolic Equivalent of Task (MET) (1 MET = 2.7 ml/kg/minute).ResultsOxygen uptake (VO2) during ABT ranged from 5.10 to 8.62 ml/kg/minute, with VO2 consistently higher during modalities involving load bearing versus non-load bearing (P = 0.08). SCI MET values ranged from 1.89 to 3.24 and were significantly higher in subjects with mid-thoracic injury versus low-cervical injury (P = 0.01).ConclusionData reveal that multi-modal ABT increases VO2 in persons with SCI, but energy expenditure is relatively low. Strategies must be identified to optimize energy expenditure in the SCI to reduce health risks. Modalities involving load bearing seem to be superior to non-load-bearing activities. VO2 was greater in response to load-bearing modalities than non-load-bearing modalities. It remains to be determined whether chronic ABT enhances cardiovascular fitness and reduces disease risks in this population.

Realize the Non-Load Bearing Walls Material Products Development of Building Envelope of Energy Conservation and Durable Fire Integration and Realize the Complete Sets of Technology Researching

Introduce the realizing the non-load bearing walls material products of building energy conservation and durable fire integration, which is also called the heat-cutting off energy-saving composite block. Introducing it’s constitute, structural features, mix design, productive technology, properties of products, main technological, economic indicators and energy saving and emission reduction effect. It is also introducing a technology thinking of new wall materials development.

Retrofit strategies to protect structures from blast loadingThis article is one of a selection of papers published in the Special Issue on Blast Engineering.

Structural retrofits to buildings can be implemented to increase the protection level to occupants from potential terrorist bombing attacks. Retrofit strategies discussed in this paper can be categorized into three groups: (i) strengthening concepts, (ii) shielding concepts, and (iii) concepts to control hazardous debris. Strengthening concepts such as span reduction and increasing member sections are considered in this paper for three common construction systems including steel, concrete, and masonry. Shielding concepts are intended to prevent structural members from being fully loaded by blast forces and range from local area applications to entire building coverage. Examples of shielding concepts include a new section of wall that shields a vulnerable portion of the building or a new structure built over an entire building. Examples of concepts to control hazardous debris include arresting or deflecting failed cladding away from critical areas with “catch systems” or internal shield systems. This paper is intended to discuss typical building retrofit strategies for primary structural members (load bearing) and secondary structural members (nonload bearing) through strengthening, shielding, or controlling hazardous debris.

Furnace Testing of Full-Scale Gypsum Steel Stud Non-Load Bearing Wall Assemblies: Results of Multi-Laboratory Testing in Canada, Japan, and USA

The present paper discusses the results of a multiple laboratory test program aimed at determining the consistency of large scale furnace testing. The North American Fire Testing Laboratories (NAFTL) consortium organized a multiple laboratory test program for ASTM E119-00 using a common structural element: a 1-h rated gypsum/steel-stud non-load bearing wall assembly. Walls were tested by six different organizations employing 10 different furnace facilities following the guidance provided in ASTM E119-00. In addition to NAFTL members conducting the tests, the program was expanded to include four testing laboratories in Japan; the Center for Better Living served as the organizer for the Japanese testing. Results obtained from these experiments are discussed.

Assessing the Bearing Capacity of Cast Laterite in Compression and Flexure

This article examines the usability of the mixture of laterite and calcined (heated) gypsum or cast laterite as a residential building masonry material. The objectives involved preliminary tests to determine the gradation of the laterite, mix ratio of the constituent materials with adequate proportion of heated gypsum. Compressive and flexural tests were carried out on the samples to determine the suitability of the material for walling. The results obtained from this work show that calcined gypsum is suitable for a non-load bearing (infill) masonry material. The comparison of the tests results indicates that cast laterite of 15% gypsum additive is adequate and higher in compression and flexure than the conventional sandcrete blocks.

Analysis of non-load bearing, 2 component epoxy-adhesive to the hemming process variations; Thermo-Gravimetric, Differential Scanning Calorimetry, and Fourier Transform Infrared Spectroscopy FT-IR analyses

This manuscript investigates the impact of automotive hemming-process variations on a 2K (2 component) non-load bearing adhesive. The investigated variations include the resin and the hardener mixing quality and ratio, the storage conditions prior to final curing, and the curing profile for Electro-Coat ovens. A Thermo-Gravimetric Analysis (TGA) provides information about the volatile evaporation percentiles in the final curing chamber, while a Fourier Transform Infrared Spectroscopy (FT-IR) is used to analyze the adhesive chemical groups mainly the hydroxyl and the epoxy groups. Additionally, this work validates the use of a Differential Scanning Calorimetry (DSC) procedure to determine such variations’ impact on the glass transition T g temperature, also on the thermo-set cure rate for different holding times. Results show that the 2K adhesive volatile content is sensitive to the curing profile (ramp-up rates) and to the holding-time variations; however the adhesive composition is insensitive to the holding-conditions, mainly the relative humidity.

Delayed Ettringite Formation (DEF) Within Pre-Cast Concrete Cladding Panels on a Mid-Rise Commercial Office Building: A Case Study

Abstract This paper will present the findings of multiple forensic investigations on a fourteen-story office building located in Houston, Texas. During our initial survey, widespread cracking was observed within the concrete cladding panels that warranted a more extensive investigation. Construction of the building was completed in 1985; 17 years prior to our initial investigation. Exterior cladding components are comprised of pre-cast concrete panels over each of the floor lines, with a continuous, structurally glazed, horizontal window system at each floor level. The cladding panels are nonload bearing, pre-cast concrete panels, installed at the time of the building’s construction. The concrete panels are attached to the structure via steel plates that are welded and bolted to the building’s frame. It is intended that this paper will present the results of observations made at the site over a period of several years, as well as the results of testing conducted to assist in the evaluation. A system was developed to locate and catalog the visible anomalies on the panels; including cracks, exposed steel, spalls, pop-outs, and efflorescence on the panels. Full-depth cores were removed from select panels to perform a petrographic analysis and scanning electron microscopy/energy dispersive x-ray microanalysis (SEM/EDXA). The results revealed the presence of delayed ettringite formation (DEF) and alkali-silica reactivity (ASR), with varying degrees of severity. Specific conclusions will be derived related to the conditions at this project and how these anomalies have affected the cladding system performance. Current repair and maintenance provisions will be discussed, in addition to the necessary recladding that will be required in the future. Recommendations will be developed regarding construction practices so that the cladding panel failure observed may be avoided in the future.

Thermal and physical characterisation of apatite/wollastonite bioactive glass–ceramics

Glass–ceramics, containing apatite and wollastonite (A/W) crystals in the MgO–CaO–SiO 2–P 2O 5 glassy matrix, show the ability to form tight chemical bonds with living tissues when implanted in the body, as demonstrated by Kokubo and co-workers. However, the medical applications are mainly limited to non-load bearing conditions because of their poor mechanical properties. To overcome this drawback, a coating of the A/W glass–ceramic could be deposited onto a titanium substrate, in order to combine the good bioactivity of the bioceramic and the good mechanical strength of the titanium alloy base material. In this study, A/W powders obtained from commercial raw materials were thermally sprayed by APS (atmospheric plasma spraying) on Ti–6Al–4V substrates. Since in the as-sprayed conditions the coating microstructure was defective because of pores and cracks, thermal treatments on A/W plasma-sprayed coatings were conducted to enhance the coating microstructure. In order to gain a deeper insight, A/W bulk and sintered samples of the same composition were prepared and subjected to the same thermal treatments. In addition, the crystallisation behaviour of A/W bioactive glass–ceramic was investigated. The frits thermal behaviour was characterised by means of hot stage measurements and DTA analysis. DTA analysis on the A/W base glass, revealed two crystallisation peaks at about 1150 and 1193 K, corresponding to the crystallisation of oxyapatite and β-wollastonite phases, respectively. The two corresponding activation energies, calculated with the Kissinger equation, were also reported. The microstructure and the crystallinity of the A/W glass–ceramics were evaluated depending on the thermal treatment. The morphology and the microstructure were observed by SEM and the crystalline phases were detected by X-ray diffraction. Finally the porosity was determined via image analysis.

Regional load bearing of the canine acetabulum

Objective To determine the load bearing areas of the canine acetabulum. Materials and methods A kinematic study of four healthy dogs was used to determine the orientation of the femur to the pelvis at mid-stance. Femora and pelves from 10 canine cadavers were loaded with the physiological canine hip reaction force and angle being replicated. Impression material placed within the acetabulum was extruded from areas of load bearing. Digital images before and after loading were used to assess if six different regions of the acetabulum were fully, partially or non-load bearing. Results All areas of the acetabulum were partially or fully load bearing. The cranial and caudal thirds of the acetabulum were 7.9 and 13.1 times more likely to be fully load bearing than the central third, respectively. There was a significant difference in load bearing between the axial, middle and abaxial thirds of the acetabulum in all tests, with the middle and abaxial thirds 72.4 and 351 times more likely to be fully load bearing than the axial third, respectively. Conclusion The cranial and caudal thirds and the middle and abaxial thirds of the canine acetabulum are fully load bearing. Clinical relevance The caudal third of the canine acetabulum is loaded and therefore recommendations that fractures in this area be managed conservatively need to be reconsidered.

Regional load bearing of the feline acetabulum

Objective: To test if the caudal acetabulum of the cat is unloaded at mid-stance as has been asserted. Materials and methods: A kinematic study of five healthy cats was performed to ascertain the mid-stance angle of the hip joint, and the orientation of the pelvis and femur. Femora and pelves from 10 feline cadavers were loaded at physiological load at the mid-stance angle. Impression material placed within the acetabulum was extruded from areas of load bearing. Digital images before and after loading were used to assess whether three areas of the acetabulum, cranial, central and caudal, were fully, partially or non-load bearing. Results: There was a significant difference in load bearing in the three regions ( p<0.001, Kruskal-Wallis test), with a significant difference in load bearing between the cranial and central thirds ( p<0.001) and the cranial and caudal thirds ( p<0.001) but no difference between the central and caudal thirds of the acetabulum (Mann-Whitney-U test). Conclusions: The load bearing areas of the feline acetabula are the caudal and central thirds. Clinical relevance: The caudal acetabulum of the cat is loaded, therefore the recommendations for simple fractures being treated conservatively needs to be reconsidered.

Testing of cold-formed steel wall stud panels

This study purposed to develop experiment-based limiting heights for interior, non-load bearing, cold-formed steel wall panels subjected to uniformly distributed lateral loadings. The composite panel of this study consists of three C-section steel wall studs with gypsum wallboard attached to each flanges of the stud with screws at regular intervals. The limiting heights were evaluated by their deflection and strength (for flexure, shear, and web crippling). Limiting heights for deflection limits ofL/360,L/240, andL/120 (whereL is the height of the wall) were developed over the range of typical design pressures. The experimental results for nominal 0.02in thickness and 12in stud spacings showed limiting heights increases from 6% to 18% compared to the current SSMA tables. Therefore, the procedure used by the SSMA for 12in spacing is conservative in this range.

Increased presence of cells with multiple elongated processes in osteoarthritic femoral head cartilage

Objective: This study examined the morphology of chondrocytes in articular cartilage from osteoarthritic (OA) and non-OA human femoral heads and in particular the appearance of a sub-population of cells with multiple elongated processes radiating up to 30 μm into the extracellular matrix. Methods: Cartilage explants were removed from 8 anatomical sites over the surface of OA ( n=6) and non-OA ( n=5) femoral heads. Cells were labeled for vimentin intermediate filaments and visualized using epi-fluorescence and confocal microscopy. The percentage of cells with elongated processes was correlated with macroscopic and histological indicators of osteoarthritis. Results: Cells with processes accounted for less than 10% of the total cell population in non-OA cartilage. By contrast, in the peripheral regions of the OA femoral head these cells accounted for 20–45% of the total cell population, the differences being statistically significant. These peripheral areas are habitually non-load bearing and were also the most likely to show gross fibrillation and pannus formation. A statistically significant correlation was demonstrated between the percentage of cells with processes and the histological extent of the OA degradation, quantified in terms of the Mankin score. Conclusions: The extension of cell processes, which may be associated with localized breakdown of the pericellular matrix, will undoubtedly alter numerous aspects of cell function including phenotypic expression and mechanotransduction. Hence these significant changes in chondrocyte morphology are likely to have important implications for the aetiology of osteoarthritis and the development of potential treatment strategies.

Topographic and zonal distribution of tenascin in human articular cartilage from femoral heads: normal versus mild and severe osteoarthritis

Objective: The extracellular matrix glycoprotein tenascin (TN) is upregulated in articular cartilage with severe osteoarthritis (OA). This study gives a detailed description of TN expression in areas of articular cartilage from femoral heads with mild OA showing structural lesions and in structurally normal areas of the same femoral heads compared with normal cartilage and cartilage with severe OA. Methods: Immunohistochemical evaluation was performed on cryosections stained with antibodies against TN. Sections were selected as follows: from each macroscopically normal femoral head ( n=6) a normal central and peripheral biopsy; from each femoral head with macroscopically mild OA ( n=8) a central biopsy that showed structural lesions and a peripheral normal biopsy; from each femoral head with severe OA ( n=9) a central and a peripheral biopsy with structural lesions. Central biopsies represent load bearing areas, whereas peripheral biopsies are non-load bearing. Results: Central cartilage with mild OA contains significantly higher levels of TN in the superficial zone than structurally normal, peripheral cartilage from the same femoral heads. Normal cartilage and cartilage with severe OA do not display this topographic variation. Central cartilage with mild OA shows significantly higher levels of TN than normal, central cartilage. Peripheral, normal cartilage with mild OA shows significantly less TN than peripheral cartilage with severe OA. Conclusions: In femoral heads with mild OA, TN is accumulated in areas displaying structural damage. This proposes mild OA to be a localized disorder. Extreme caution is necessary for sampling of articular cartilage, especially from joints with mild OA.

Structural and Economic Comparisons Between the Conventional and Stacking Method of Laying Locally Manufactured Non-Load Bearing Concrete Hollow Blocks (CHBs)

One structural element in constructing a building which requires lengthy execution is the construction of peripheral walls and partitions. If the duration of this activity is lessened, the total construction time will surely be shortened, and somehow, a cut in the construction expense due to the subsequently saved time shall also be realized. This study presents an analysis of the effects of deviating from the conventional way of laying concrete hollow blocks with the proposed stacking method using locally manufactured concrete hollow blocks. The general trend ofthe study suggests that the proposed stacking method oflaying locally manufactured concrete hollow blocks could savean average of 39 seconds per square meter, and considerably more as the wall progresses in height. Using this statistics, a medium rise building with 1,500 sq.m. of wall area could save two man-days with the method. The test results show that the samples laid using the stacking method are generally stronger than the samples done with the staggered method in terms of the recorded higher compressive stresses by direct comparison. Then compared vis-a-vis the age, the staggered method was observed to have resisted slightly more (but insignificant) compressivestresses than the samples in stacking method.

Preformas para compósitos estruturais

Os compósitos estruturais com reforço uni ou bi-direcional, ao contrário dos materiais homogêneos e isotrópicos, apresentam tanto baixa resistência ao cisalhamento interlaminar (&lt; 60 MPa) quanto baixa tenacidade à fratura interlaminar. Como decorrência disso estes compósitos são susceptíveis de falha sob baixo carregamento mecânico, e por esse motivo a utilização destes materiais está confinada a componentes estruturais de responsabilidade secundária. A utilização de matrizes com maior tenacidade à fratura em compósitos produz resultados insatisfatórios para aplicações estruturais, pois o ganho na resistência à fratura interlaminar é insuficiente. A utilização de reforços multi-direcionais (preformas) têm gerado resultados significativos nesse particular fazendo com que as pesquisas sejam direcionadas para essa tecnologia. O presente trabalho descreve os métodos que estão sendo utilizados para obtenção de preformas multi-direcionais, tanto para aplicação em compósitos poliméricos quanto para compósitos termo-estruturais. A adição de uma fração volumétrica de fibras equivalente a ~1 - 2% na direção normal ao plano do compósito é suficiente para conferir tanto resistência ao cisalhamento quanto tenacidade à fratura interlaminar, sem prejudicar as propriedades originais em outras direções. A utilização de preformas multi-direcionais permite também maior isotropia de propriedades, maior tenacidade à fratura e resistência às tensões térmicas durante o processamento e em serviço.