196,012 research outputs found
Timber Frame Moment Joints with Glued-In Steel Rods. II: Experimental Investigation of Long-Term Performance
No full textThe pull-out performance of steel rods glued into timber is well-documented, and short-term tests by many researchers have demonstrated reliable strength. The behavior of glued-in steel rods in moment-resisting beam-column joints is much more complex because of anisotropy of wood in the connection region, discontinuity of material at the interface, and the possible effects of creep of timber and stress
concentrations on the joint performance. This paper describes the results of a series of long-term load tests on moment-resisting joints between glulam members and separate load tests on the various joint components, including the epoxy itself and the timber stressed
perpendicular to the grain. Different types of knee joints, with rods fully epoxied along their length or epoxied only in one member
and tensioned in the other, and with different geometries (with the beam extended over the column or with the column extended past the beam) were tested. Measurements were recorded to identify time-dependent stress redistribution within the test joints, creep of the joint as a whole, and possible crushing of the timber-to-timber bearing surfaces. Local deformation of timber loaded in compression perpendicular
to the grain was found to contribute to excessive joint deformations in tests in which the steel rods were not glued over their full length. The test results confirm the possibility to use the transformed section method in design as presented in the first companion paper, and address a number of issues pointed out in the same paper
Timber Frame Moment Joints with Glued-In Steel Rods. I: Design
No full textSignificant evidence based on experimental research exists to give designers confidence in the use of theoretical equations to evaluate the pullout strength of threaded steel rods glued into timber. However, the mechanism of load transfer through a timber frame moment joint utilizing glued-in steel rods requires more than simply understanding the tension performance of a glued-in rod. A method of evaluating joint strength for moment and axial forces based on traditional mechanics theory adapted for use with timber is presented. Formulas were derived from first principles for joint configurations, with extended columns or with extended beams and with various types of construction (i.e., with rods fully glued along their entire length or only glued in one of the two members connected and then tensioned). The design method also considers the effects of time-dependent deformation in timber at bearing interfaces and the effects of stress concentrations imposed by the steel rods on the timber. Some open questions that deserve further investigations are highlighted, as well as some possible details to optimize joint performance while retaining ease of assembly. The approach provides a methodology for joint design that has been successfully used in many projects
"Long term deformation of epoxy glued glulam portal frame knee joints" May 2009.
No full textThis project was initiated to resolve uncertainty regarding the long-term performance of epoxied rod connections in glue laminated timber (glulam), specifically the long term-deformations associated with beam-column moment joints. The excellent short-term performance of this type of connection is well known. However there is some scepticism in industry over the long-term performance. The behaviour of this connection when subjected to long term loading is thought to be primarily affected by creep in the timber and heterogeneity of the cross section. It has been hypothesised that the stress distribution at the beam-column interface may change over time leading to a localisation of stresses, rotations within the joint and ultimately, excessive deflections of the frame at serviceability limit states. Furthermore, crushing of the timber perpendicular to the grain may occur in the long-term as a result of the stress redistribution over time which could cause failure at ultimate limit state. In order to investigate the long term performance, two types of experimental testing were carried out in this project: (i) long term testing of several frames and lever specimens; and (ii) short term testing of several smaller glulam specimens.
Four frames with a “C” shaped layout (i.e. one column and two beams) were tested. Two of these frames used the “fully-epoxied” connection, where the steel rods were epoxied along the full length, whilst the other two frames used the “tensioned half epoxied” connection, where the steel rods were epoxied into one member and tensioned to the other. Two different geometries were tested (the column running past the end of the beam and the beam extending over the top of the column).
The lever specimens were designed to individually measure the different components of creep. These measured the creep of the timber itself (both parallel and perpendicular to the grain), the creep of a timber specimen with epoxied rods at both ends, and the creep of the glue alone.
Short-term bending, compression and pullout tests were carried out on glulam according to ISO recommendations to characterise the timber used in this project. The results of the compressive strength tests perpendicular to the grain gave compressive stresses that were approximately 50% of that specified in the New Zealand Timber Standard. This is of concern and needs attention given the importance of this property when designing any joints where structural performance depends on bearing perpendicular to grain.
Some important conclusions have been reached. The results from the Glulam Lever Specimens showed that creep perpendicular to the grain may be up to 8 times greater than that parallel to the grain. The remaining lever specimens showed that long term pullout deformations are likely to be negligible in dry conditions. The “fully epoxied” connection performed significantly better than the “tensioned half epoxied” connection. This is due to better transfer of forces in the “fully epoxied” connection and hence very little reliance on the compressive strength of timber perpendicular to the grain. Creep of timber was found to mainly affect the deflection of the frame specimens, as no significant stress redistribution was noticed in the long-term between timber and rods. It was also pointed out that a significant contribution to the total deflection is given by the flexibility semi-rigidity of the connection itself, which is usually designed as a rigid joint but should more realistically be considered as a semi-rigid connection. Design equations have been proposed and are shown to correlate well with the results obtained. Lastly, a method has been described to estimate the long-term stresses in the glulam and steel elements
"Moment joints in timber frames using glued-in steel rods: experimental investigation of long-term performance"
No full text"Long term deformation of epoxy glued glulam portal frame knee joints" May 2009.
No full textThis project was initiated to resolve uncertainty regarding the long-term performance of epoxied rod connections in glue laminated timber (glulam), specifically the long term-deformations associated with beam-column moment joints. The excellent short-term performance of this type of connection is well known. However there is some scepticism in industry over the long-term performance. The behaviour of this connection when subjected to long term loading is thought to be primarily affected by creep in the timber and heterogeneity of the cross section. It has been hypothesised that the stress distribution at the beam-column interface may change over time leading to a localisation of stresses, rotations within the joint and ultimately, excessive deflections of the frame at serviceability limit states. Furthermore, crushing of the timber perpendicular to the grain may occur in the long-term as a result of the stress redistribution over time which could cause failure at ultimate limit state. In order to investigate the long term performance, two types of experimental testing were carried out in this project: (i) long term testing of several frames and lever specimens; and (ii) short term testing of several smaller glulam specimens.
Four frames with a “C” shaped layout (i.e. one column and two beams) were tested. Two of these frames used the “fully-epoxied” connection, where the steel rods were epoxied along the full length, whilst the other two frames used the “tensioned half epoxied” connection, where the steel rods were epoxied into one member and tensioned to the other. Two different geometries were tested (the column running past the end of the beam and the beam extending over the top of the column).
The lever specimens were designed to individually measure the different components of creep. These measured the creep of the timber itself (both parallel and perpendicular to the grain), the creep of a timber specimen with epoxied rods at both ends, and the creep of the glue alone.
Short-term bending, compression and pullout tests were carried out on glulam according to ISO recommendations to characterise the timber used in this project. The results of the compressive strength tests perpendicular to the grain gave compressive stresses that were approximately 50% of that specified in the New Zealand Timber Standard. This is of concern and needs attention given the importance of this property when designing any joints where structural performance depends on bearing perpendicular to grain.
Some important conclusions have been reached. The results from the Glulam Lever Specimens showed that creep perpendicular to the grain may be up to 8 times greater than that parallel to the grain. The remaining lever specimens showed that long term pullout deformations are likely to be negligible in dry conditions. The “fully epoxied” connection performed significantly better than the “tensioned half epoxied” connection. This is due to better transfer of forces in the “fully epoxied” connection and hence very little reliance on the compressive strength of timber perpendicular to the grain. Creep of timber was found to mainly affect the deflection of the frame specimens, as no significant stress redistribution was noticed in the long-term between timber and rods. It was also pointed out that a significant contribution to the total deflection is given by the flexibility semi-rigidity of the connection itself, which is usually designed as a rigid joint but should more realistically be considered as a semi-rigid connection. Design equations have been proposed and are shown to correlate well with the results obtained. Lastly, a method has been described to estimate the long-term stresses in the glulam and steel elements
"Moment joints in timber frames using glued-in steel rods: experimental investigation of long-term performance"
No full textDr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
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