Full-size Specimens Research Articles

Connections between Simply Supported Concrete Beams Made Continuous

Precast bridge girders can be made continuous for live loads with the provision of a moment connection over the supports. NCHRP Project 12–53 examined methods for making this type of moment connection. This is usually done by placing negative moment reinforcement in a cast-in-place deck over the support and by placing a diaphragm between the girder ends. To counteract positive moments caused by creep and shrinkage, positive moment connections are often provided at the girder ends. An experimental study of the strength of six different positive moment details, involving either extended strand or extended bar, was conducted. The results showed that all details had sufficient strength. Details using additional stirrups in the diaphragm were found to have increased ductility, and the use of horizontal web bars increased capacity. Two full-size specimens were tested to determine the level of continuity after cracking occurs at the joints. One of these specimens was also monitored for several months to determine the effects of creep, shrinkage, and temperature on the connections. It was found that expansion and contraction of the deck caused by heat of hydration and changes in ambient temperature greatly affected the system. However, an anticipated formation of negative moment caused by differential shrinkage did not occur. Even when the positive moment connection was near failure, the system maintained 70% continuity even when cracked. The system was also found to have adequate negative moment capacity.

強風下における機械的固定工法による防水層の挙動の風洞実験による観察

A waterproofing membrane is partially fixed to a substrate by fasteners in mechanically anchored systems. For designing a safer anchored waterproofing system against typhoons, it is needed to make clear the behavior of it under strong wind. Two kinds of full size specimens with a parapet and without one were exposed to high wind speed of a wind tunnel. The behavior of the system was investigated from the three aspects such as wind forces to a membrane, deformation of a membrane and tensile forces of fasteners induced by high wind. Strong wind force was observed in the area close to the windward edge for the roof without a parapet and about 1m on the leeward from a parapet for the roof with a parapet. The membrane was lifted up by wind to about 60mm in maximum height and was extended to about 0.6% in maximum elongation and it oscillated about 5-20Hz in periodic time. The tensile force of more than 160N was observed in some fasteners, depending on the location in the roof.

A trilinear stress-strain model for confined concrete

For reaching large inelastic deformations without a substantial loss in strength, the potential plastic hinge regions of the reinforced concrete structural members should be confined by adequate transverse reinforcement. Therefore, simple and realistic representation of confined concrete behaviour is needed for inelastic analysis of reinforced concrete structures. In this study, a trilinear stress-strain model is proposed for the axial behaviour of confined concrete. The model is based on experimental work that was carried out on nearly full size specimens. During the interpretation of experimental data, the buckling and strain hardening of the longitudinal reinforcement are also taken into account. The proposed model is used for predicting the stress-strain relationships of confined concrete specimens tested by other researchers. Although the proposed model is simpler than most of the available models, the comparisons between the predicted results and experimental data indicate that it can represent the stress-strain relationship of confined concrete quite realistically.

Empirical Correlation of Specimen Size Effects in Charpy Impact Properties of 11Cr-0.5Mo-2W, V, Nb Ferritic-Martensitic Stainless Steel

An effect of specimen size on the Charpy impact property was evaluated in the ferritic-martensitic 11Cr-0.5Mo-2W, Nb, V stainless steel (PNC-FMS). The upper shelf energy (USE) is expressed by the power law equation as USE[J]=m(Bb) n where m is the material constant (m=0.277 in PNC-FMS), B[mm] is the specimen thickness and b[mm] is the ligament size. The normalizing exponent n was empirically derived using the USE of the full size specimen as n=1.38×10–3USEfull+1.20. The n value varies in the range of 1.2 to 1.7, which is affected by the fracture volume below the notch. The PNC-FMS wrapper takes n=1.42. The ductile-to-brittle transition temperature (DBTT) of PNC-FMS is correlated as DBTT=115(log10 BKt)—158 using an elastic stress concentration factor Kt that represents the effects of notch size, e.g. notch depth, notch root radius and notch angle.

On the Possibility of Avoiding the Use of a Clip Gage When Testing Precracked Charpy-V Specimens in the Ductile-to-Brittle Transition Region

Abstract Fracture toughness testing using bend-type samples, such as precracked Charpy specimens, requires using a clip gage for measuring crack mouth opening displacement (CMOD). This paper demonstrates that it is possible to avoid using a clip gage and use instead machine crosshead displacement (MCD) as an approximation of load-line displacement; this simplifies considerably the test procedure, both in terms of mechanical operations and specimen instrumentation. This is particularly desirable for irradiated materials and when testing subsize specimens. Results obtained in the ductile-to-brittle transition regime from the analysis of 151 toughness tests show that reference temperatures calculated using the Master Curve methodology with CMOD and MCD are fully equivalent within a few degrees. The investigation has been conducted on different materials, test machines, full-size, and subsize specimens.

Effect of Aggregate Type on Mechanical Behavior of Dam Concrete

Due to the practical difficulties in performing a full size specimen test, dam concrete is usually sieved to remove the aggregate larger than 40 mm (1.6 in) when tested, which is called sieved concrete. This paper reports on a study that examined the influence of surface roughness of aggregate via two types of aggregates on the mechanical and fracture properties for dam and sieved concretes. The authors used two types of aggregates by full size specimens of 450 x 450 x 900 mm (18 x 18 x 35 in.) for tension and 450 x 450 x 450 mm (18 x 18 x 18 in.) for compression and by standard size specimens 150 x 150 x 550 mm (6 x 6 x 22 in.) for tension and 150 x 150 x 150 mm (6 x 6 x 6 in.) for compression, respectively. The complete stress-strain responses both in tension and compression were acquired through a systematic experimental program. The authors propose models to estimate the basic mechanical properties and the fracture parameters of the concretes with specimen ages; they propose theoretical models for normalized axial stress-strain curve in compression and for normalized axial stress versus normalized maximum crack width curve in uniaxial tension. Results include: the strengths, modulus of elasticity, and fracture energy increase with specimen age; the specimen size and maximum aggregate diameter significantly affect the fracture energy, peak strain, and crack width of concretes in uniaxial tension; and the performance of concrete with crushed coarse aggregate is higher than that of concrete with natural coarse aggregate.

Full-scale testing of corrugated fibreboard shelter subjected to static-equivalent wind loads

DuraKit Shelters Inc. has developed a modular house for emergency, temporary or semi-permanent occupation that uses corrugated fibreboard as the main structural material. The houses are marketed internationally and so must resist tropical cyclone wind loadings. Two full-scale shelters, measuring 4.9 m×6.1 m in plan, were subjected to static forces equivalent to loads caused by wind acting normal to the ridge of the roof. Five areas of each full-size specimen were independently loaded using a large test facility built in 5 days on a rural outdoor site for a cost of approximately Cdn$8000. The testing illustrated strengths and weaknesses in the design and construction of both the shelter and the testing apparatus. The shelter generally performed well, but was susceptible to premature local failures in regions where tension was applied through the thickness of corrugated fibreboard panels or where the quality of construction was imperfect. The testing apparatus also generally performed well, once its connections to the specimen were modified to eliminate localized areas of high stress and the relatively large deformation of the specimen were accommodated. Failure of the second specimen initiated at the roof-to-wall connection of the windward wall when the applied load reached 73% of the pressures caused by tropical cyclone winds. Roof deflections observed on the full-scale shelter agree reasonably with those predicted using finite element analysis. The observed deflections were greater than the predicted values, and the discrepancy can be attributed to creep and other effects not considered in the finite element analysis. This suggests that finite element modeling is an appropriate tool for investigating the behaviour of corrugated fibreboard structures.

구속효과를 고려한 모르타르 충전식 철근이음의 부착강도

The purpose of this study is to propose the more reasonable equation of bond strength of grout-filled splice sleeve. To accomplish this objective, total 60 full-sized specimens were tested under monotonic loading. The experimental variables are compressive strength of mortar, embedment length and size of reinforcing bars. Following conclusions are obtained; 1) If the adequacy of existing equations which estimate the bond strength of grout-filled splice sleeve are investigated, they underestimate the bond strength of grout-filled splice sleeve by 8-18%. Also the existing equations have a tendency to underestimate with decrease in the embedment length of reinforcing bars. 2) From the test result of bond failure, the equation which estimates the confining pressure of grout-filled splice sleeve was proposed by making multiple regression analyses of which independent variables are embedment length of reinforcing bars and compressive strength of mortar. This equation predicted the measured bond capacity of this test more accurately than existing equations and eliminated the deviation according to the embedment length of reinforcing bars.

Evaluation on Fatigue Crack Propagation of Reduced Activation Ferritic Steel (JLF-1) at High Temperature

Recently, reduced activation ferritic/martensitic steel, vanadium alloy and SiC/SiC composite are embossed for nuclear fusion reactor in accordance with the coolant. Especially, reduced activation ferritic/martensitic steel is very suitable material for nuclear fusion reactor, because it has low coefficient of thermal expansion and excellent heat conductivity. The objective of this study is to investigate fatigue crack propagation behavior in the Reduced Activation Ferritic Steel (JLF-1). The fatigue crack propagation behavior of the JLF-1 steel was investigated by the constant-amplitude loading test for the stress ratios R = 0.1, 0.3 and 0.5 respectively. The fatigue crack growth tests carried out at room temperature and [Formula: see text] for base metal and weld metal. The effects of stress ratio, test temperature, specimen size and TIG welding on the fatigue crack propagation behaviors for JLF-1 steel were discussed within the Paris law. Particularly, the fatigue crack propagation rate of a weld metal was similar to that of base metal at the stress ratio of 0.3. Also, the fatigue crack propagation rate of a half size specimen was similar to that of a full size specimen at the stress ratios of 0.1, 0.3 and 0.5 respectively. From this result, we can recognize that the fatigue crack propagation behavior of this material can be evaluated by using the half size specimens.

Fatigue life and fatigue crack propagation behavior of JLF-1 steel

The objective of this study is to investigate fatigue life and fatigue crack propagation behavior in the reduced activation ferritic steel JLF-1. The experiment of fatigue life for JLF-1 steel have been carried out for the stress ratio R=0 at room temperature and 400 °C. The fatigue crack propagation behavior of the JLF-1 steel was investigated by the constant amplitude loading test for the stress ratios R=0.1, 0.3 and 0.5, respectively. The effects of stress ratios and specimen size on the fatigue crack growth behaviors for JLF-1 steel were discussed within the Paris law. The fatigue life test performed under the room temperature and 400 °C. At room temperature, the fatigue limits of longitudinal and transverse direction to the rolling direction were 480 and 490 MPa at 1×10 7 cycles, respectively. Also, at 400 °C, the fatigue limits of longitudinal and transverse direction to the rolling direction were 400, 416 MPa at 1×10 7 cycles, respectively. The base material of JLF-1 steel showed the isotropic behavior in fatigue properties of the rolling direction and the test temperature. The fatigue crack propagation rate of a half size specimen was similar to that of a full size specimen at the stress ratios of 0.1, 0.3 and 0.5, respectively. The fatigue crack propagation behavior of this material can be evaluated by using half size specimens.

Measuring Air Leakage Characteristics with Flexible Double Air Chambers

The fan pressurization method for measuring air leakage through the building envelope relies on the assumption that the extraneous air leakage (EAL) through paths other than those through the specimen being tested is negligible. When EAL does exist, the calibration procedure by ASTM Standard E-283 is used to measure EAL values by covering the specimen or guarded chambers are used to equalize the pressure differences across these unintended paths. A new testing method, the flexible double-chamber method, is presented in this paper for large specimens where the above two approaches are difficult to implement and where flexible chambers are more easily applied. The experimental procedure and data processing routine are presented for the case of a full-size metal curtain wall specimen. The EAL is estimated by regression analysis in data processing. Inference analysis, multivariate error analysis, and the Monte Carlo simulation technique are also presented to examine the estimation errors.

Fiber micro-buckling of continuous glass-fiber reinforced hollow-cored recycled plastic extrusions under long-term flexural loads

Experimental results on fiber micro-buckling of continuous glass-fiber reinforced hollow-cored recycled plastic extrusions under creep tests are introduced in the paper. The full size specimens with dimensions in 2.5×3.5×42 in. 3 were submerged in warm water at a temperature of 125 °F when they were under a four-point bending creep test. The results show that the micro-buckling of the embedded glass-fiber roving occurs along 90% the length of the specimen on the upper inner surface (compressive side) and mainly during the time between 5 and 100 h from the initial loading moment. The micro-buckling causes the steady-state apparent flexural modulus of the composite drop faster, and it also causes the plastic matrix local crackling which subsequently leads to the structural failure of the composite. The stress level has little effect on the steady-state creep rate. The results also show some evidence that the plastic matrix becomes more brittle when it is submerged in warm water for certain long time. From the results, it is indicated that the pattern or distribution of the micro-buckling is significantly different from that of short-term four-point bending test for the same composite materials, for which the fiber micro-buckling occurs locally only on the middle section of the specimen.

Charpy-V Subsize Specimens

Subsize specimens in Charpy impact tests has are a valuable substitute to predict the ductile-to-brittle transition temperature (DBTT) and the upper shelf energy (USE) anticipated for full size specimens where volume limitations exist. The subsize specimens have been applied to testing of several steels and the data has been compared to those of standard full size specimens. The common normalization on the basis of fracture area does not produce any correspondence between the two different sized specimens therby showing an apparent decrease in both USE and DBTT by using subsize specimens.

水衝撃連続チッピングの掘削体積比エネルギー

Specific energy of the chipping upon water jet drilling is discussed from a latticed multi-point drilling experiment, to make clear the utility of chipping as an excavation measure in hard rock. The experiment is conducted using the full-size specimen of Amakusa sandstone of the uniaxial compressive strength: SC = 84 MPa, and Granite of SC = 190 MPa. The optimum drilling interval is evaluated as well as the specific energy Es, after consideration to the relation between the crater depth: h and the excavation volume: V. It is clarified that the dimension ratio of m = SC / Es is in a range of from 0.40 to 0.55 in the case of the driving pressure: pI = 90 MPa. A model named the repetition model is proposed, to forecast the specific energy of the continuous chipping by the Third Power Method, and its validity is successfully verified by comparing the computation to the experimental results. Subsequently, it is discussed that the continuous chipping results in an excavation of higher efficiency than both of the pure water jet cutting and the abrasive water jet cutting.

Dynamic Racking Performance of an Earthquake-Isolated Curtain Wall System

Dynamic racking tests, coupled with air leakage tests, were performed on fullsize specimens of a new, Earthquake-Isolated Curtain Wall System and a widely used, conventional curtain wall system (used as an experimental control). Dynamic racking tests simulated seismic movements that could be imposed upon a curtain wall system as a result of interstory drifts. Air leakage tests were performed as an indicator of serviceability performance of both curtain wall systems during the dynamic racking tests. The Earthquake-Isolated Curtain Wall System demonstrated strongly superior performance in terms of both serviceability (glass cracking and air leakage) and life safety (glass fallout). The conventional system exhibited vulnerability to annealed monolithic glass cracking and glass fallout at dynamic racking drift indices of 1.9% and 3.1%, respectively. No glass damage was observed in the earthquake-isolated system up to the dynamic racking displacement limit of the test facility, which corresponded to a drift index of 4.9%. Air leakage rates through vision panels in the conventional system remained constant up to a drift index of 1.9%, after which the air leakage rates increased rapidly. In contrast, air leakage rates through vision panels in the earthquake-isolated system remained unchanged up to the 4.9% drift index capacity of the test facility.

Tensile testing of microsamples

Structural analysis has advanced rapidly to the point where lack of knowledge about the local inhomogeneity and anisotropic nature of the materials prevents the accurate prediction of the behavior; models can incorporate local material properties provided they can be experimentally determined. Conventional tensile techniques are unable to test speciments from submillimeter-sized regions, and micro-hardness measurements do not reveal directional variations. A system has been developed to perform tensile tests on microsamples that are 3.1 mm long with a gage cross section that is 0.2 mm square. The volume of the test region is roughly 500,000 times smaller than a standard half-inch diameter specimen. Tensile stress-strain curves are measured, and the yield strength, ultimate strength, modulus and elongation are calculated for each sample. Samples cut from the weld metal of undermatched welds in HY-100 plate showed a large variation in properties from the center of the weld to the outer edge, as well as anisotropy at some locations. The average mechanical properties of a group of microsamples cut from the outer region of the weldment compared favorably with measurements made using full-sized specimens; the variation in the microsample measurements reflect local variations in the material that are not measured with full-sized specimens.

Seasonal and spatial changes in blowfly production from small and large carcasses at Durham in lowland northeast England.

Colonization by blowflies (Diptera: Calliphoridae) of mouse carcasses exposed in open agricultural land near Durham (54 45'N) changed from early spring monopolization by Calliphora vicina R.-D. to a summer pattern of multiple species exploitation by this species together with Lucilia caesar L., L. illustris Mg., L. silvarum Mg., L. sericata Mg. and L. richardsi Collin. In a garden at the edge of Durham, mouse carcasses were dominated by C. vicina from spring to autumn. Difference in mouse colonization between the agricultural and garden sites seemed to reflect differences in the blowfly species present, as measured by baited trap catches at the sites. In sets of C. vicina reared from mice under conditions of competition for larval food, it was found that resulting females were significantly larger than males, size being measured as mean wing length. Blowfly production from three sheep carcasses exposed successively at the agricultural site was dominated by C. vomitoria L. and L. caesar, but also produced other Lucilia species in small numbers, including L. sericata. These L. sericata females from sheep that had died from causes other than myiasis included full-sized specimens, in contrast to those produced from mouse carcasses that were all undersized individuals. As L. sericata females trapped on sheep pastures are predominantly full-sized, this suggests that large carcasses may, in part, be a source of the L. sericata population that attacks sheep as a myiasis agent. The nature of large carcasses as possible sources of L. sericata in lowland Britain is discussed.

Stirrup distribution across the beam width in tension lap splices

The influence of the distribution of transverse confining steel on the strength of tension lap splices was investigated experimentally in this study. Beam specimens contained three lap-spliced No. 35 bars placed in one layer. Either two or three stirrup legs were placed across the beam width to provide splitting confinement. Both configurations were designed to provide similar stirrup resistances for intercepting horizontal bond splitting. The effectiveness of the different stirrup configurations was compared by investigating the performance of beams subjected to static, fatigue, and fully reversed inelastic loading. Twenty-three full-size beam specimens were tested with the lap splice placed symmetrically within a maximum moment, zero-shear region. Specimens were constructed and tested in six different series (concrete batches). Within each series, the total bond resistance, as evaluated on the basis of CSA A23.3-94, was similar even though the lateral distribution of transverse steel was varied. Nine specimens were tested under monotonically increasing (static) loading to failure, six specimens were subjected to fatigue load cycling between 25% and 75% of their ultimate static strength, and eight specimens were subjected to fully reversed inelastic load cycling. Test results for six similar specimens from a previous study were also included in the current investigation analysis. Test results indicated that using three vertical stirrup legs across the beam width to provide a more uniform distribution of stirrup confinement significantly enhances post yield ductility under fully reversed inelastic load cycling. Meanwhile, specimens tested under static loading showed that CSA A23.3-94 provisions provide a consistent and conservative prediction of lap-splice strength for the specimen configurations investigated, regardless of the distribution of stirrup confinement across the beam width. Finally, the performance of fatigue specimens indicated a slight improvement with the use of the three-leg stirrup configuration. However, this result does not agree with previous observations made at the same institution where it was suggested that stirrup confinement intercepting vertical splitting plays a more significant role in defining fatigue resistance.Key words: reinforced concrete, bond, confinement, lap splices, stirrups, static loading, fatigue load cycling, inelastic load reversal.

Strength and behaviour of steel fibre reinforced concrete corners under opening bending moment

The effect of adding steel fibre to reinforced concrete corner joints under opening bending moment was investigated by tests on 23 specimens containing various amounts of fibres up to 2% (by volume). Two reinforcement details, with and without inclined bars, were used in the full-sized specimens, which were tested to failure. The corner angle was varied from 60° to 180°. The results obtained indicate a considerable improvement in the flexural efficiency and ultimate moment-carrying capacity of the joints with the inclusion of moderate amounts of fibres. By adding 1–2% fibres the risk of diagonal tension failure is considerably reduced, and full flexural capacity is achieved in the weakest corners (corner angles of 75–150°). From the analysis of the results, a simplified empirical relationship was derived for the prediction of the ultimate moment-carrying capacity of joints.

Effect of specimen type and size on fracture resistance curve determination for CuCrZr alloy

The precipitation hardened copper alloy CuCrZr is one of the candidate materials for the first wall and divertor components of ITER. In order to validate the applicability of copper alloys in the structural components of ITER, the effect of neutron irradiation on the fracture toughness behaviour has to be studied. Fracture toughness testing of irradiated materials requires the use of miniaturised specimens and the verification of specimen size effects on fracture toughness test results. In the present study the effects of specimen type, size as well as temperature on the ductile tearing fracture resistance behaviour of CuCrZr alloy will be shown. The applicability of miniaturised specimens for fracture resistance curve determination is considered by studying the allowable crack extension with which the miniaturised specimens still have similar fracture resistance curves as full-size specimens. The crack length and J-integral values will be compared to ASTM standard requirements for the maximum allowable crack extension and J-integral values in the fracture resistance test.