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Purpose To present the visual and safety outcomes of surgery for primary idiopathic macular holes including predictors of visual acuity and the impact of combined phacovitrectomy surgery. Design Registry-style, prospective, nonrandomized, observational cohort study. Participants Patients with idiopathic macular holes undergoing primary surgery. Methods Surgeons were invited to submit clinical details of all macular hole cases receiving surgery. Baseline demographic and clinical information, and details of surgical intervention were collected. Primary follow-up data were collected at 3 months postoperatively or before revision surgery, and surgeons were also asked to submit data at 12 and 24 months postoperatively. Main Outcome Measures Visual acuity improvement ≥15 letters and ≥0 letters, change in mean visual acuity, visual acuity ≥70 letters (20/40), retinal detachment, and endophthalmitis. Results A total of 2455 eyes of 2366 patients were included in the study, and hole closure was achieved in 95.6% of eyes with a single procedure. Mean baseline vision was 48.3 letters. The proportion of successful eyes improving ≥15 letters at 3, 12, and 24 months was 59.1%, 69.4%, and 68.2%, respectively. The mean improvement in acuity at 3, 12, and 24 months was 16.0, 19.2, and 23.6 letters, and 92.4%, 93.4%, and 95.8% improved ≥0 letters at 3, 12, and 24 months, respectively. Eyes receiving SF6 gas had better visual acuities at all time points postoperatively (adjusted effect 3.4, 3.1, and 4.6 letters better at 3, 12, and 24 months vs. longer-acting gas, respectively). Combined phacovitrectomy in phakic eyes was associated with better corrected visual acuity postoperatively (vs. vitrectomy surgery alone), a difference that vanished when eyes went on to have subsequent cataract surgery. The rate of retinal detachment postoperatively was 1.3%, and the odds of detachment were greater in eyes receiving longer-acting gases versus SF6 gas (adjusted odds ratio, 2.2; 95% confidence interval, 1.04–4.77; P = 0.039). There were no reported cases of endophthalmitis. Conclusions Macular hole surgery substantially improved acuity in approximately two thirds of patients and was seldom associated with loss of vision. SF6 gas was associated with better visual outcomes, an effect that warrants further study.

Nuclear concrete structures must be designed against a large spectrum of severe accidents. The primary purpose of this study is to simulate and evaluate the blade fragment impact on an auxi...

As a structural and constructional element, a thin-walled U-shaped precast permanent form consisting of High-Performance Fiber-Reinforced Cementitious Composites (HPFRCC) and steel wire mesh is considered. Prior to casting, transverse steel threaded bars are installed, as well as longitudinal reinforcing bars, connecting two sides of the U-shaped form for shear transfer between the precast and in-filled concrete sections and for fresh concrete pressure resistance. The present study investigated the effect of precast U-shaped HPFRCC section on the shear strength of the composite beams. As parameters for full-scale three-point bending tests, the type or materials of precast section, spacing of shear reinforcement, and shear span-to-depth ratio were considered. The test results showed that the precast U-shaped HPFRCC permanent form increased the shear contributions of in-filled concrete and shear reinforcement in the composite beam substantially. From the experimental and analytical assessment, the coefficients related to the composite action between precast HPFRCC and in-filled concrete sections, shear reinforcement along diagonal cracks, and shear span-to-depth ratio were proposed, which were applied to a previous shear strength model for the simplified shear design of proposed precast U-shaped HPFRCC-in filled concrete composite beams.

High density 1Gb embedded STT-MRAM in 28nm FDSOI technology was successfully demonstrated. Based on the highly reliable and manufacturable eMRAM technology, high yield over 90% was achieved at the operating temperature from −40°c to 105°c with satisfying read, write function and 10 years retention at 105°c. These results are mainly attributed to the advanced process for better control of MTJ CD, highly manufacturable process window and robust circuit design for high density chip. MTJ properties can be systematically adjusted by tailoring the MTJ stack and MTJ module process. Improved endurance up to 1E10 cycles was achieved to broaden eMRAM applications to eDRAM replacement.

We demonstrate a novel way of integrating STT-MRAM for on-chip hybrid memory which exhibits either features of high-retention or high-speed implemented in separate zones in a single chip. For satisfying high-temperature retention requirement, tailored MTJs are shown to support > 10 year retention at 220°C. For high-speed operation, critical improvements have been made in terms of TMR, short fail probability, overdrive and write error rate. The new integration provides a manufacturable way of combining diverse memory components by modulating non-volatility of STT-MRAM without affecting within-chip distributions of critical properties.

The Mireuksaji stone pagoda (the only remaining building in Mireuksaji temple) has existed for 1400 years. More than half of the Mireuksaji stone pagoda has collapsed. Due to the historical...

Separate processes underlying forward (e.g., crescent MOON) and backward (e.g., office POST) priming have previously been inferred from button-press lexical decision response times, with an automatic prospective mechanism and a strategic retrospective mechanism presumed responsible for forward and backward priming, respectively. We tracked hand/mouse kinematics during lexical decision, and found that forward, backward, and symmetrical (e.g., cat DOG) priming exhibited different movement trajectories, with the effect of forward priming emerging earlier than that of backward priming and with symmetrical priming taking the lead around the time when the backward priming effect came online. The findings provide strong converging evidence for different mechanisms driving forward and backward priming, and demonstrate that continuous kinematic measures can shed light on cognitive processes as they unfold in real time.

ACI 318-14 and 423.7-14 require the use of encapsulation system for an unbonded single-strand tendon for the purpose of corrosion protection and enhanced durability. In this study, load-carrying performance and hydrostatic tests were conducted for a newly developed, unbonded post-tensioning (PT) anchor with encapsulation, following the guidelines put forth in KCI-PS101 and ACI 423.7-14. The static load and fatigue tests as part of this study were used to evaluate the anchorage system behavior under static and cyclic loads, respectively. The hydrostatic test was used to demonstrate that the encapsulation system withstood at least 9.3 kPa of water pressure in a 24 h period according to ACI 423.7-14, and thus has been proven to promote the durability of unbonded PT single-strand tendons. Additionally, the push-in and jacking tests were used to assess the compressive and tensile strengths of the anchor as used in the field. Although these tests were not performed to failure for safety reasons, the anchor endured at least 1.18 and 1.02 times the nominal ultimate strength of a strand in each test, respectively. The authors’ previous load transfer tests were also reported in this paper, showing that test specimens with only two horizontal backup bars were capable of resisting at least 1.7 times the nominal ultimate strength of a strand. Based on the favorable results from the load-carrying performance and hydrostatic tests, the developed encapsulated anchor systems are being applied in actual practice as an economically feasible option in Korean PT industry and are expected to improve the corrosion resistance and durability of post-tensioned structures.

Investigating pore structure of calcium sulfoaluminate cement paste is significantly important to understand the hydration process of cement, to develop the models that describe the cement paste mi...

The present study investigated whether the sequencing of exemplars affects learning of rule-based science categories. We taught undergraduate students chemical categories by showing them diagrams of organic chemical compounds accompanied by their category label in either an interleaved or blocked fashion. On a categorization test of novel exemplars administered 2 days later, interleaved presentation produced superior performance than blocked presentation for categories that were visually simple (Experiment 1) and relatively more complex (Experiment 2). The advantage of interleaved presentation was still observed when the diagnostic features of each category were highlighted during study (Experiments 3 and 4), suggesting that the benefit of interleaving may not be due solely to increasing the salience of contrastive features that differentiate the categories. These findings demonstrate that interleaved presentation can improve learning of educationally relevant categories, even when coupled with pedagogical techniques that emphasize the diagnostic features of each category.

Mercury intrusion and nitrogen sorption porosimetry were employed to investigate the pore structure of calcium sulfoaluminate ( $$ C\overline{S} A $$ ) and portland cement pastes with cement-to-water ratio (w/c) of 0.40, 0.50, and 0.60. A unimodal distribution of pore size was drawn for $$ C\overline{S} A $$ cement pastes, whereas a bimodal distribution was established for the portland cement pastes through analysis of mercury intrusion porosimetry. For the experimental results generated by nitrogen sorption porosimetry, the $$ C\overline{S} A $$ cement pastes have a smaller and coarser pore volume than cement paste samples under the same w/c condition. The relative dynamic modulus and percentage weight loss were used for investigation of the concrete durability in freeze–thaw condition. When coarse aggregate with good freeze–thaw durability was mixed, air entrained portland cement concrete has the same durability in terms of relative dynamic modulus as $$ C\overline{S} A $$ cement concrete in a freeze–thaw environment. The $$ C\overline{S} A $$ cement concrete with poor performance of durability in a freeze–thaw environment demonstrates the improved durability by 300 % over portland cement concrete. The $$ C\overline{S} A $$ concrete with good performance aggregate also exhibits less surface scaling in a freeze–thaw environment, losing 11 % less mass after 297 cycles.

The Kuiper Belt is a distant region of the Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a Cold Classical Kuiper Belt Object, a class of objects that have never been heated by the Sun and are therefore well preserved since their formation. Here we describe initial results from these encounter observations. MU69 is a bi-lobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color and compositional heterogeneity. No evidence for satellites, ring or dust structures, gas coma, or solar wind interactions was detected. By origin MU69 appears consistent with pebble cloud collapse followed by a low velocity merger of its two lobes., 43 pages, 8 figure

In this paper, we reviewed the existing literature on the fabrication of nanocomposites based on cellulose and cellulose nanocrystals (CNCs), and analyzed their dispersion mechanism with respect to their use in the field of construction. First, the existing literature on CNC-based nanocomposites that exhibit the physical and chemical properties of nanocellulose and CNCs was reviewed. Next, keeping the use of these nanocomposites in the field of construction in mind, we determined the optimal mechanical method for their dispersion as an alternative to the currently used harmful chemical techniques. To this end, we evaluated the dispersibility of colloidal CNCs using two dispersion methods: magnetic stirring (for stirring times of 60 min, 120 min, and 180 min) and high-pressure dispersion (at pressures of 345 &times, 105 Pa, 1035 &times, 105 Pa, and 1587 &times, 105 Pa, and one to three dispersion passes). The optimal dispersion conditions were determined by analyzing the size and zeta potential of the CNC particles. It was found that the difference in the average diameter was reduced by approximately 76% at 1587 &times, 105 Pa during high-pressure dispersion.

We successfully demonstrated the manufacturability of 8Mb STT-MRAM embedded in 28nm FDSOI logic platform by achieving stable functionality and robust package level reliability. Read margin were greatly improved by increasing TMR value and also reducing distribution of cell resistance using advanced MTJ stack and patterning technology. Write margin was also increased by improving the efficiency using novel integration process. Its product reliability was confirmed in package level with passing HTOL 1000 hours tests, 106 endurance test, and retention test. For a wider application, we also demonstrated the feasibility of high density 128Mb STT-MRAM. Based on these results, we clearly verified the product manufacturability of embedded STT-MRAM.

This paper describes a deformation-based strut-and-tie model for the flexural members at post-yield state. Boundary deformation conditions by flexural post-yield response are chosen in terms of the flexural bar strains as the main factor influenced on the shear strength. The main purpose of the proposed model is to predict the shear capacities of the flexural members associated with the given flexural deformation conditions. To verify the proposed strut-and-tie model, the estimated shear strengths depending on the flexural deformation are compared with the experimental results. The experimental data are in good agreement with the values obtained by the proposed model.

The flexural strength of circular concrete-filled tubes (CCFT) can be estimated by several codes such as ACI, AISC, and Eurocode 4. In AISC and Eurocode, two methods are recommended, which are the strain compatibility method (SCM) and the plastic stress distribution method (PSDM). The SCM of AISC is almost the same as the SCM of the ACI method, while the SCM of Eurocode is similar to the ACI method. Only the assumption of the compressive stress of concrete is different. The PSDM of Eurocode approach is also similar to the PSDM of AISC, but they have different definitions of material strength. The PSDM of AISC is relatively easier to use, because AISC provides closed-form equations for calculating the flexural strength. However, due to the complexity of calculation of circular shapes, it is quite difficult to determine the flexural strength of CCFT following other methods. Furthermore, all these methods give different estimations. In this study, an effort is made to review and compare the codes to identify their differences. The study also develops a computing program for the flexural strength of circular concrete filled tubes under pure bending that is in accordance with the codes. Finally, the developed computing algorithm, which is programmed in MATLAB, is used to generate design aid graphs for various steel grades and a variety of strengths of steel and concrete. These design aid graphs for CCFT beams can be used as a preliminary design tool.

Retrieval practice has been shown to benefit learning. However, the benefit has sometimes been attenuated with more complex materials that require integrating multiple units of information. Critically, Tran et al. Psychonomic Bulletin & Review, 22, 135–140 (2015) found that retrieval practice improves sentence memory but not the drawing of inferences from the same sentences. In three experiments, we investigated whether this lack of benefit of retrieval practice for inferential ability was due to the presentation format of the material. Participants studied four sets of seven to nine related sentences by practicing retrieval for two sets and rereading the other two sets. A final test was given 2 days later. When sentences were presented one at a time during study/practice as in Tran et al., we found no effect of retrieval practice on a test requiring inferential reasoning. When sentences in a set were presented simultaneously during study/practice, retrieval practice in the form of fill-in-the-blank testing (experiments 1 and 2) and free recall (experiment 3) aided later deductive inference more than rereading. Our findings suggest that retrieval practice can improve deductive inference, but in order to optimize its utility, the format in which the material is presented during practice must not hinder relational processing of the individual sentences.

Given that there are few concrete stress-strain models available for rectangular CFT sections with high-strength materials, this study attempts to develop an empirical and practical stress-strain model that can be used in conjunction with the strain compatibility method of the American Concrete Institute Code (ACI 318-14), American Institute of Steel Construction Specification (AISC 360-10), and Eurocode 4. For a better understanding, the structural provisions of rectangular CFT columns in ACI 318-14, AISC 360-10 and Eurocode 4 are comparatively reviewed. Then, an updated database is assembled from previous and recent test results of rectangular CFT columns subjected to eccentric axial loads to evaluate whether the existing provisions and/or stress-strain models for concrete can be used. Finally, a new concrete stress-strain model is proposed that leads to more accurate and more consistent prediction of the P-M interaction strength of rectangular CFT columns under general design conditions.

Steel fiber-reinforced prestressed concrete (SFRPSC) members typically have high shear strength and deformation capability, compared to conventional prestressed concrete (PSC) members, due to the resistance provided by steel fibers at the crack surface after the onset of diagonal cracking. In this study, shear tests were conducted on the SFRPSC members with the test variables of concrete compressive strength, fiber volume fraction, and prestressing force level. Their localized behavior around the critical shear cracks was measured by a non-contact image-based displacement measurement system, and thus their shear deformation was thoroughly investigated. The tested SFRPSC members showed higher shear strengths as the concrete compressive strength or the level of prestress increased, and their stiffnesses did not change significantly, even after diagonal cracking due to the resistance of steel fibers. As the level of prestress increased, the shear deformation was contributed by the crack opening displacement more than the slip displacement. In addition, the local displacements around the shear crack progressed toward directions that differ from those expected by the principal strain angles that can be typically obtained from the average strains of the concrete element. Thus, this localized deformation characteristics around the shear cracks should be considered when measuring the local deformation of concrete elements near discrete cracks or when calculating the local stresses.

A laboratory test was performed to predict the lateral earth pressure on the pipe buried in soft ground subject to lateral movement. The boundary of the punching shear was drawn from the observed c...

This study was conducted to verify seismic performance of special moment frame's joints at roof-level with high-strength concrete and SD600 bars. K-RC-H was designed according to the seismic code and K-HPFRC-H had 150% of the original hoop spacing and 1.0% steel fiber volume fraction compared with K-RC-H. Both specimens had remarkable seismic performance without noticeable decrease in moment, but with very good energy dissipation before rebar failure. The U-bars in the joint sufficiently constrained rebar`s action that pushed the cover upward. SD600 bars with 1.25 had minimum slip in the joint. It was considered that the steel fiber contributed to improvement of the bending moment and joint shear distortion, and the result showed that it would be possible to increase the hoop spacing to 150% of the regular spacing.

This paper presents a Strut-and-Tie Model for reinforced concrete (RC) columns subject to lateral loading. The proposed model is based on the loading path for the post-yield state, and the geometries of struts and tie are determined by the stress field of post-yield state. The analysis procedure of the Strut-and-Tie Model is that 1) the shear force and displacement at the initial yield state are calculated and 2) the relationship between the additional shear force and the deformation is determined by modifying the geometry of the longitudinal strut until the ultimate limit state. To validate the developed model, the ultimate strength and associated deformation obtained by experimental results are compared with the values predicted by the model. Good agreements between the proposed model and the experimental data are observed.

Concern that students in the United States are less proficient in mathematics, science, and reading than their peers in other countries has led some to question whether American students spend enough time in school. Instead of debating the amount of time that should be spent in school (and on schoolwork), this article addresses how the available instructional time might be optimally utilized via the scheduling of review or practice. Hundreds of studies in cognitive and educational psychology have demonstrated that spacing out repeated encounters with the material over time produces superior long-term learning, compared with repetitions that are massed together. Also, incorporating tests into spaced practice amplifies the benefits. Spaced review or practice enhances diverse forms of learning, including memory, problem solving, and generalization to new situations. Spaced practice is a feasible and cost-effective way to improve the effectiveness and efficiency of learning, and has tremendous potential to improve educational outcomes. The article also discusses barriers to adopting spaced practice, recent developments, and their possible implications.

It is known that the prestressed half PC (precast) slab system has many advantages such as a reduced construction period and use of long-span one-way slab systems over reinforced concrete and half PC slab systems without prestressing. For this reason, prestressed half slabs are commonly used for both residential and basement parking structures in Korea and other countries. The prestressed half PC slab systems currently being used only have the pre-tensioning system only for PC slabs. To ensure better performance of the half PC slab system with larger span-to-depth ratio, a new system using both pre-tensioning and post-tensioning methods is suggested for basement parking structures in this paper. The main purpose of this paper was to analyse the suggested model and verify its safety and serviceability for a given span and a given load. The second purpose is to suggest a preliminary calculation process for the suggested system that satisfies the ACI 318 requirements. A parametric study is conducted ...

The seismic performance evaluation of a 49-story residential building under construction in Seoul, Korea is the subject of this paper. The building for this case study has an irregular plan and a deep basement shared with adjacent buildings. A series of nonlinear time history analyses were carried out for the Maximum Considered Earthquake (MCE) and Rare Earthquake (RE). Effects of modeling methods of the basement were studied. Modeling of the surrounding underground structure included transfer of torsional modes, which can easily be amplified by high frequency components of ground motions and result in localized damage at the upper part of building. Based on the analysis presented, the basement model with surrounding underground structures and non soil-structure interaction is recommended for a conservative design.

The design of a post-tensioned transfer plate is typically controlled by shear force&mdash, in particular, punching shear at the slab-column connection. To verify the accuracy of the separated model only for one floor currently used in the design of a post-tensioned transfer plate, results were compared to a complete model with multi-story building system for which two representative residential building plans were used to emulate physical structural systems. Punching shear stress for the separated model was calculated using the eccentric shear stress model presented in ACI 318. Punching shear stress was found to be overestimated in the separated model, given that interaction between transfer plates and upper shear walls cannot be reflected therein. Differences at column locations were also noted as the number of stories below the transfer floor increased. Consequently, the separated model is not recommended for design of post-tensioned transfer plates. A complete model is more suitable for more realistic and potential cost-effective design, through the inclusion of the interaction between transfer plates and upper shear walls.

Motivation is fundamental to human agency and volitional behavior, and several influential theories have been proposed to explain why individuals choose or persist in a course of action (over others). New terms and concepts have proliferated as the theoretical models aim to be comprehensive, at the expense of parsimony. The theoretical models covered in this special issue each have their unique aspects and contributions, but four major dimensions cut across them: person factors comprising self (expectations, self-efficacy), social (modeling, comparisons), and cognitive aspects (self-regulation); task values; goals; and perceived costs and benefits. Motivation is determined by a complex interplay of internal and external factors, and we suggest that a greater focus on individuals’ motivation profiles, construal of situations, and metacognitive monitoring and control of goal pursuit might shed more light on the moment-by-moment decisions people make in daily life. Future research could be targeted at evaluating competing models (or perhaps more parsimonious ones) and enhancing interventions to address students who are unmotivated to excel in school.

In previous studies, it was demonstrated that the geometry of regular anticlastic membrane structures attached to edge beams on all four sides of the membrane is one of the most influential...

This study assessed the structural performance of reinforced concrete (RC) arch bridges under strong ground motion. A detailed three-dimensional finite element model of a 400 m RC arch bridge with composite superstructure and double RC piers was developed and its behavior when subjected to strong earthquakes examined. Two sets of ground motion records were applied to simulate pulse-type near- and far-field motions. The inelastic behavior of the concrete elements was then evaluated via a seismic time history analysis. The concept of Demand to Capacity Ratios (DCR) was utilized to produce an initial estimate of the dynamic performance of the structure, emphasizing the importance of capacity distribution of force and bending moment within the RC arch and the springings and piers of the bridge. The results showed that the earthquake loads, broadly categorized as near- and far-field earthquake loads, changed a number of the bridge&rsquo, s characteristics and hence its structural performance.

To investigate the axial load behavior of hybrid concrete columns consisting of an ultra-high performance fiber-reinforced concrete tube (20 mm thick, 92.6 MPa or 143.3 MPa) and normal-strength concrete core (28.2 MPa), concentric axial load tests were performed for five column specimens. The UHPFRC tube can function as a form during core-filling and as a cover having high performance at service and ultimate load conditions. Axial loading was applied to the core only, and the tube was indirectly loaded by bearing of transverse threaded bars. Test parameters included the volume fraction of steel fibers, volumetric ratio of transverse bars, and usage of wire-mesh in the tube. Test results showed that structural performance such as initial stiffness, peak load, displacement ductility, and energy absorption capacity varied greatly according to each test parameter. During the course of axial loading applied on the core only, the axial load behavior of the hybrid concrete columns generally corresponded to the full composite action at the initial loading stage and then changed to that of non-composite action (core only) after the failure of the threaded bars.

In the moment frame subjected to earthquake loads, beam-column joint is structurally important for ductile behavior of a system. ACI Committee 352 proposed guidelines for designing beam-column joint details. The guidelines, however, need to be updated because of the lack of data regarding several factors that may improve the performance of joints. The purpose of this study is to investigate the seismic performance of reinforced concrete exterior joints with high-strength materials and unbonded tendons. Three specimens with different joint shear demand-to-strength ratios were constructed and tested, where headed bars were used to anchor the beam bars into the joint. All specimens showed satisfactory seismic behavior including moment strength of 1.3 times the nominal moment, ductile performance (ductility factor = at least 2.4), and sufficiently large dissipated energy.

This paper summarizes the results from an experimental study on the behavior of concrete slabs-on-ground in a controlled environment. The test program characterizes the dimensional properties of selected concrete materials, evaluating their performance as real slabs-on-ground in that they are exposed to the controlled environment on the top surface and to the ground moisture on the bottom surface. The concrete mix designs examined included normal-strength portland cement concrete ( PCC ), high-strength concrete ( HSC ), concrete using shrinkage reducing admixtures ( SRA ), and concrete using calcium sulfoaluminate cement ( CSA ). The data include standard concrete material characterization test results, joint movements, internal relative humidity and temperature over the slab depth. It was found that the concrete using CSA was very stable with no long term shrinkage, cracking or warping, while typical PCC and HSC continued to show crack growth at over 600 days of age. The concrete using SRA had a minor impact at early age and limited impact on long term sectional stability.

In this study, twenty four steel-fiber reinforced concrete (SFRC) beams using recycled coarse aggregates (RCA) were manufactured to examine the shear behavior of SFRC and to determine the beams' ultimate shear strengths. The RCA replacement ratio was fixed at 30%. The variables studied in this investigation are: (1) shear span-to-depth ratios (a/d) of 2, 3 and 4; (2) longitudinal reinforcement ratio () of 0.008 and 0.0127; and (3) steel fiber volume fractions (Vf) of 0, 0.5, 0.75 and 1%. Test results were analyzed and then compared with the findings and proposals of various other researchers. Based on the test results, the more steel fiber volume fraction is increased, the large crack resistance and shear strength are exhibited. Most of the experimental data is higher than the theoretical value. Therefore, steel-fiber reinforced concrete beams using recycled coarse aggregates are suggested to be applied for building structures.

Cold-formed built-up members are compression members that are common in multiple areas of steel construction, which include cold-formed steel joints and stud walls. These members are vulnerable to unique buckling behaviors; however, limited experimental research has been done in this area. Give this gap, experimental testing of 71 built-up members was conducted in this study. The variations of the test specimens include multiple lengths, intermediate welds, orientations, and thicknesses. The experimental testing was devised to observe the different buckling modes of the built-up C-channels and the effects of the geometrical properties; to check for applicability of multiple intermediate welding patterns; and to evaluate both the 2001 and 2007 editions of the American Iron and Steel Institute (AISI) Specification for built-up members in pure compression. The AISI-2001 and AISI-2007 were found to give inconsistent results that at times were un-conservative or overly conservative in terms of axial strength. It was also found that orientation of the member has an important impact on the maximum failure load on the member.