Abstract. Collapse of timber constructions can appear under the effect of load that exceeds the resistance of a carrying element or under the effect of a geometrical instability like buckling. In addition, loading can be constant or varying for example loads due to wind or earthquakes. The aim of this paper is to study the behaviour and the lifetime of columns in wood or based-wood material such as glulam (GL) or laminated veneer lumber (LVL) under repeated loading leading to buckling.
Because of repeated loading, thickness of base course becomes higher than only subjected by static loading. Soil reinforcement using geosynthetic material (geotextile and/or geogrid) accommodated in some methods as Giroud-Han, USA Corps of Engineers and DuPont Typar method respectively, but they give divergence results. For instance USA Corps of Engineers is applied for low traffic originally in the forest region particularly in USA and did not accommodate the repeated loading and DuPont Typar method only focuses on reinforcement using geotextile. Otherwise Giroud-Han method offers for design of soil reinforcement using both geotextile and geogrid and also accommodate the repeated loading of vehicles. The last
In the present study, only the mean whole free AT transverse strain was assessed because of the large variation in tendon injury location along the length of the free AT in participants with MAT. Studies in the field of tendon mechanobiology suggest that there is an optimal strain environment for positive tendon adaptation (Wang, 2006), with either higher or lower than optimal strains resulting in a catabolic effect. It therefore follows that targeted rehabilitation strategies, perhaps combining biological and exercise-based therapies, could be developed in the future to create an optimal mechanical environment for tendon regeneration. In future studies, it will be important to better characterize the local strains in the region of the tendinopathic lesion. Additionally, we were not able to visualize the whole tendon CSA along the proximal AT during a single transverse ultrasound sweep in the present study. Such information could be obtained in future using other imaging approaches such as MRI (Iwanuma et al., 2011; Reeves and Cooper, 2017). Furthermore, 3D US is limited by its inability to detect the thickness of the tendon paratenon, epitenon and peri-tendinous space, and thus the tendon CSA measurement in the present study was confined to the tendon core. Additional studies are required to determine these tendon parameters at rest and during repeated loading using imaging techniques such as MRI that have greater resolution than ultrasound in order to identify the fluid exudation mechanism from the tendon core into the peri-tendinous space as well as the time course of recovery of tendinopathic tendon volume following a standardized AT repeated loading protocol. Also, although all measurements were made at the same relative ankle joint plantarflexion torque (50% MVIC), we cannot be certain that the force applied to the free tendon and proximal AT was equal or whether longitudinal and/or transverse force distribution changed as a function of contraction number. It is, however, important to note that the activation level of TA muscle during repeated isometric plantarflexion contractions was small ( ∼ 5%) and no changes in EMG activity of the TS and TA muscles and the co-activation index were detected between contractions. Finally, the present study was conducted using a specific repeated loading protocol (25 s at 50% MVIC per contraction) (Nuri et al., 2016) in male adults with
In each set six specimens were cast, out of which three specimens were tested under monotonic loading and other three under repeated loading. A reaction frame was fabricated for testing specimens under monotonic and repeated load as shown in figure 3.The specimen was seated in between two supports spaced 600mm apart canter to canter in reaction frame. Loading was applied from top upwards such that the tension face of specimen is on bottom as shown in fig 3. This was done to facilitate marking of cracks in the flexure zone. Rubber padding was used both that supports and at load points, to ensure that the load was applied uniformly across width of the specimen. Loads were applied at one fourth span points, ie at 150mm from supports using a mechanical screw jack of 250kN capacity through a distribution steel high beam shown fig 3.Applied load was measured using a proving ring of 50KN capacity.
In the present paper, a new probabilistic model of fatigue failure of structures made of brittle materials undergoing cyclic loading in the range of elastic strains is addressed. In accordance with the model, the beginning of macrofailure is related to the critical value of microcrack concentration and is defined by the statistical strength criterion whose nature is attributed to the probabilistic character of the microfailure process. It is assumed that the macrofailure occurs by forming macrocracks due to accumulation of microdefects in the form of flat microcracks randomly dispersed over a volume ().
The Wheel Tracking Test apparatus (WTT) are used for this investigation with varying contact pressure of moving load to simulate the filed condition. It was developed by British National Rail Road Research Institute (generally used for measuring the plastic deformation of bituminous asphalt concrete). The WTT apparatus height of the loading
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Deflections and strains on mortar surfaces at various levels across the depth of the specimens in pure flexure zone were recorded during testing of ferrocement elements under monotonic and repeated flexural loading. Deflections were measured at mid points and locations of these points are shown in figure 4.2. For measuring deflections at these points, dial gauges of 25mm range with least count of 0.01mm were used. During testing, these dial gauges were reset when the deflection exceeded the range of gauges.Strains on mortar surface of specimens were measured by demec (de mountable mechanical) gauge over demec points fixed to the mortar surface with an adhesive. Surface strains were measured on top and bottom edges of the specimens and at other levels of specimen across the depth. strains were measured on both the faces of specimen over gauge length of 200mm and least count of demec gauge was 0.79*10^-5.
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mechanical behavior due to heterogeneous characteristics of concrete influence behavior after a peak load , Table-8 show the result of repeated load test and figures from (2) to (5) show the behavior of slabs under repeated load for G1(normal concrete) and G2 (silica fume concrete) respectively, the result for all slabs with bacterial addition showed Improved in performance in varying degrees reached (4.85%) for first cracking load and (4.89%) for load of the eight cycle ,that’s return to bacterial activity while mixing the concrete it grows and spread it produce the strongest glue inside the concrete (for direct addition) which work in improve the concrete micro stricture[16 ] It was also observed that pores in concrete are partially full of by the material growth with the addition of bacteria. Reduction in pores will obviously increase the density of the material and strength. As the pores in concrete are filled by bacteria, a chance of development of cracks reduces considerably . Plate-4 show the experimental test.
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Due to controversial results of several random- ized trials, Aradi et al. conducted a meta-analysis on the efficiency and safety of intensified antiplate- let therapy (repeated loading or elevated mainte- nance doses of clopidogrel, prasugrel or glyco- protein IIb/IIIa inhibitor) on the basis of platelet reactivity testing versus standard clopidogrel dos- ing in PCI-treated patients with HTPR. The results of 10 clinical trials revealed that intensified treat- ment considerably reduced cardiovascular mortal- ity, stent thrombosis and myocardial infarction. However, no difference was apparent in terms of major bleeding events. Overall, the benefit of the intensified treatment was meaningful for patients at high risk of ST, while disappeared in low-risk in- dividuals. The authors of the article also stated that the aggregometry approach is also more economi- cal due to the high costs of administering new-gen- eration ADP receptor antagonists .
comparison. These samples were not straight and had curva- tures in original state. After the tensile test, the samples were straight forwarded along the tensile direction. Figure 9(a) shows the load-strain curves with repeated loading- unloading-reloading treatment for the samples (a) and (b). As the conﬁguration and cross-sectional area varied with the sample length, the deﬁnite cross-sectional area could not be deﬁned, due to which just the load was used instead of stress. As the non-contact extensometer could not be used for the test of micro-samples, the displacement of the cross-head was used for strain estimation. Accordingly, the estimated strain was apparent (noted as e app in Fig. 9(a)), containing the strain
A total number of eighteen T- beams (out of which six beams are reinforced with conventional steel reinforcements and six beams were reinforced with Grooved Glass Fibre Reinforced Polymer (GFRP) reinforcements and Six beams were reinforced with Sand coated GFRP reinforcements) are studied. A rigorous experimental studies on the behaviour of conventional and GFRP reinforced concrete T- beams under static and repeated loading are investigated by considering reinforcement ratios, grade of concrete, thickness of slabs and type of GFRP reinforcements. GFRP T-beams are investigated for repeated loading (with constant and variable amplitude loading). At ultimate load, GFRP reinforced T- beams experience concrete crushing followed by rupture of GFRP reinforcements. As the ultimate load carrying capacity of GFRP reinforced T- beams is increased, the corresponding deflections, strains and crack width are reduced by increasing the thickness, grade of concrete, reinforcement ratio of the beams. GFRP reinforced concrete beams experiences better performance under repeated loading than those beams reinforced with conventional steel. It is due to the fact that the onset of permanent deformations is delayed due to the higher strains in the GFRP specimens than the conventionally reinforced beams. This is mainly attributed due to the equal values of the modulus of elasticity for GFRP reinforcements and concrete in addition to the linear - elastic behaviour of GFRP reinforcements.
On rocky shores, wave-swept macroalgae experience dramatic and repeated wave-induced hydrodynamic forces. However, previous studies of macroalgal mechanics have shown that individual waves are not forceful enough to account for observed rates of breakage. Instead, fatigue may contribute to algal breakage, with damage accumulating over time in conditions of repeated loading. Here I examine the entire process of fatigue, from crack initiation to eventual specimen fracture, in the common red alga Mazzaella . Propensity for fatigue failure in laboratory tests varied with life history phase and species: at a given repeated loading stress, male gametophytes endured more loading cycles before breakage than tetrasporophytes, which in turn lasted longer than female gametophytes; likewise, M. splendens withstood more loading cycles at a given repeated loading stress than M. flaccida . Fatigue failure begins with formation of cracks, the timing and location of which were assessed. Cracks formed, on average, after approximately 80–90% of cycles required for failure had passed, although crack timing varied with life history phase. Also, crack formation frequently occurred in association with endophytes and female gametophyte reproductive structures, suggesting a cost of endophyte infection and a tradeoff between reproduction and mechanical survival. Comparison between laboratory and field loading conditions provides robust confirmation that fatigue breaks fronds in natural M. flaccida populations. Large, female gametophyte fronds are predicted to be most susceptible to fatigue failure in the field, whereas small, male gametophyte fronds are least likely to break.
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We return now, and for the remainder of the introduction, to our basic example with 2 nodes and only 1 link. Consider the repeated commuting game for this example. That is, the dynamic commuting game that we have speci ﬁ ed is played daily. What payoﬀs are attainable? We shall apply a folk theorem below, so the set of payoﬀs attainable as Nash equilibria in the repeated game is related to the payoﬀs attainable in the one shot game. Speci ﬁ cally, for large enough discount factors in the repeated game, all feasible payoﬀs at least as high as the maximin payoﬀ for the one shot game (that are not necessarily Nash equilibria of the one shot game) are attainable as Nash equilibria of the repeated game. In fact, we can show that any payoﬀ that is feasible in the one shot game can be attained as a Nash equilibrium of the repeated game. This result is achieved by simply computing the maximin payoﬀ of the one shot game. It will be −∞ . Why? Consider one individual in our simple example. The worst case scenario for that individual in the one shot commuting game is that everyone else who lives at the same node “blockades” them at time zero. That is, the strategy used by everyone else is to depart at time 0. Then local congestion is in ﬁ nite, so nobody ever reaches the destination or even moves at all, independent of what the commuter in question does (namely, what departure time strategy they follow). 3
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Recently, various researchers show their interest in improvising properties HPC against impact loads with addition of different fibres. Earlier research shows that addition of fibres acts as crack arrester and also increases the energy absorption capacity of structural members (Sabale Vishal Dhondiram. B. B. Patil, 2012). Strength and Durability Properties of High Performance Concrete incorporating High Reactivity Metakaolin (HRM), with various percentage of HRM and replacement of cement by silica fume, GGBS and Fly Ash to 10% causes a significant increase in the mechanical properties of the HPC. (Prashant Muley, 2015; Kinayekar 2014) The Compressive Strength, flexural strength increases significantly for 1 % carbon fibre content. (Rajagopalan et al., 1995) investigated experimentally under repeated low energy impact loading on concrete beam 100x200x2300mm, M40. Impact head is instrumented with load cell, Accelerometer and LVDT are used to measure the dynamic response of the beam. The beam peak force reduces with increased number of impact blows for a giver energy of impact loading. (Anbuvelan, Yeol Yoo and Trevor D. Hrynyk 2012) the resistance of concrete slabs under impact loading by strengthening by Fiber Reinforced Polymer Sheets, steel fibre, Polypropylene fibre under impact loading shows a significant increase in the impact characteristic with respect to number of blows for first crack and also the ultimate load carrying capacity of the concrete member. The load carrying capacity of the specimen containing only steel fibre was increased by 19 % whereas the capacity increased by 30% in case of specimen containing steel fibre and fiber reinforced plastics. (Xue-Chao Zhu et al., 1996) Drop-Weight Impact Test on U-Shape concrete specimens from a drop height of 400 mm with four different masses
Figure 10 compares the time-dependent mid-span deflection of the debonded beams under sustained and repeated load types. It can be seen that the deflection of both beams was similar during the first 20 days, however, at the end of the test, the beam subjected to the repeated load exhibited more deflection (+7%) than the beam subjected to the sustained load. The 7% extra deflection after 90 days seen in this investigation (note that this may be considered close to the setup accuracy) theoretically may be due to 1) the effect of cyclic creep, since the cyclic creep enhances static creep  or 2) the fact that the artificial debonding method had not worked in its entirety. Also relate to the fact that any residual bond may have been removed during the loading stage.
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Sugun and Rao  conducted repeated drop tests over a range of incident energies on glass, carbon and kevlar composites and reported a numerical relationship between the impact energy and the number of drops to failure (perforation). As the incident energy was varied in an arithmetic progression, the number of drops to failure took a harmonic sequence. They also noted that peak load decreases, while total energy increases until failure. The impact penetration process can be divided into three stages: an initial slope, the fracture zone and the friction stage. The force – time histories contain characteristic features distinguished by the impactor shape used to impact the specimen. Experiments using a round tip, low cone and tall cone impactors were conducted by Kepler  who reported that the stiffness of the panels decrease with the pointness of the impactor. A blunt impactor pushes the material inwards and a sharp one pushes the material sideways. In a similar study Kim and Goo  showed that as the spherical radius of the impactor increases the maximum contact force becomes higher and impact duration shorter.
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The temporal evolution of the thin film under the effect of shear T and surface tension γ loading is shown in figure 12. Under this combination of load- ings, two distinct symmetrically placed rivulets form, one each on the upper and lower surfaces. Figure 12 shows the evolution at early times of these rivulets, whose location is just windward of the clockwise and anti-clockwise separation points for a dry cylinder at the same Re, which is consistent with the previous experimental analysis of Bosdogianni and Olivari  and the numerical results of Lemaitre et al. . Closer examination of the temporal evolution of the rivulets in figure 12 reveals that they are of approximately equal height, profile and growth rate; the minor discrepancies between the two can be attributed to a small asymmetry in the applied shear loading distribution which results from the faithful approximation of the aerodynamic coefficients determined ex- perimentally by Achenbach , since with a perfectly symmetric distribution of aerodynamic coefficients the two rivulets are indeed identical and symmetric about the incident wind.
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resulted into undesirable load shedding 10years ago. As a result of this, another substation was commissioned about 7years ago. Presently, the area is experiencing same problem of load shedding. The occupants of this substation are high caliber people which include a vice chancellor of a private university in Nigeria, a retired pharmacist of Federal University Teaching Hospital in Nigeria, a Managing Director and medical practitioner in Lagos State, a practicing consulting engineer and lecturer in a Nigeria Federal University, directors in the Lagos States coupled with the high concentration of the people where street lights are highly needed to reduce mischievous characters in the night. Loading of transformer at 60% to cater for future expansion is a necessity. Code recommends 25% future expansion of the load. It therefore means that 25% of the 60% loading yields 75% previous loading. This will allows moderate overloading at 75% previous loading. The design in work is based on this philosophy. This will facilitates long life of the transformers or otherwise the substation. Apart from load shielding that motivated this work which was mentioned earlier, another motivation is inability of the author to design a 33/0.415 kV substation after 2years of obtaining his Master Degree when working with an international consulting firm. This bottleneck should be overcome with our first and second degree holders, thus the high motivation of this research.
Kumar et al. (2006) comment that in order to provide valuable learning lessons, it is important to highlight and discuss the difficulties encountered when conducting improvement projects. Kumar et al. (2006) suggest that this will contribute in facilitating their deployment in the future. In the case of the implementation of the proposed LSS framework, convincing top management of taking a broader view of the loading operation by also considering the berthing process and role of other business units rather than simply focusing on the loading process itself was an arduous task. This may be considered a natural phenomenon as previously indicated, the application of Lean and/or Six Sigma principles and tools by iron ore producers is limited (Indrawati and Ridwansyah, 2015; Hokoma et al., 2010; Shinka Management, 2012; Chinbat and Takakuwa, 2008). Additionally, the limited use of Lean and/or Six Sigma in the iron ore industry may also suggest that there is no clear understanding on how the benefits of the combination of these approaches, in the form of LSS, can support the improvement of operations in this sector. To overcome these challenges, management teams were convinced by citing examples of some successful organisations, in other industries, that had improved the efficiency of their processes and enhanced their bottom-line results using the application of LSS.
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Many economic and social interactions are repeated: the same buyers and sellers of- ten trade with one another multiple times, teams of contractors regularly work for the same procurement agencies, and voters repeatedly elect representatives, to name just a few. The central theme of this paper is the design of institutions, or contractual arrange- ments, that generate “socially desirable” outcomes in settings where agents repeatedly interact and preferences change over time.
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