LEED-NC version 2.2 rating system applications of common structural materials

Maher, J.E., Kramer, K.W.. LEED-NC version 2.2 rating system applications of common structural materials. 2007. Sustainable Construction Materials and Technologies, Taylor and Francis Group.Comprehensive understanding of building materials has been the basis of structural engineering. The rising environmental concern is making sustainability a crucial issue in our society. In creating a sustainable built environment, the architect usually takes the lead role with the mechanical engineer having the key responsibility for energy and water savings. Only recently have structural engineers and civil engineers begun to see the real potential of their contributions. This paper contains information pertaining to the four most common structural materials: reinforced concrete, reinforced masonry, steel, and timber. For each material, the sustainability of the material as defined by the LEED-NC Version 2.2 rating system is discussed. Information is provided on how to attain LEED points for a specific material. Whether the LEED-NC Version 2.2 rating system accurately portrays sustainability of common structural materials or needs further development is discussed in the conclusion. A comparison is provided of the four common structural materials in relation to the rating system

Slip modulus of cold-formed steel members sheathed with wood structural panels

Maher, J. E., & Kramer, K. W. (2007). LEED-NC version 2.2 rating system applications of common structural materials. Paper presented at the Sustainable Construction Materials and Technologies - International Conference on Sustainable Construction Materials and Technologies, 549-562.Cold-formed steel framing sheathed with wood structural panels is a common method of construction for wall, roof and floor systems in cold-formed steel structures. Since wood structural panels are attached with screws at relatively close spacing, a certain amount of composite behavior will be present. The benefit of composite behavior is not currently being taken advantage of in the design of these structural systems. While composite effects are present, they are not yet being accounted for in design due to a lack of statistical data. To determine the amount of composite action taking place in these systems, the slip modulus between steel and wood is required. The slip modulus reflects the amount of shear force able to be transferred through the screw connection, to either member of the composite system. This paper presents the results of a study conducted to determine values of the slip modulus for varying thicknesses of cold-formed steel and plywood sheathing. Shear tests were conducted and the slip moduli were determined based on ISO 6891 and ASTM D1761. Compared with data from a previous preliminary study performed by others, the slip modulus values determined from these tests were deemed reasonable. The determination of the slip modulus will lead to the ability to calculate a composite factor. Determination of a composite factor will allow cold-formed steel wood structural panel construction to become more economical due to the available increase in bending strength

Load-deflection response of prestressed concrete beams strengthened with FRP: a comprehensive perspective

Doctor of PhilosophyDepartment of Civil EngineeringHayder A. RasheedCurrently, degradation of pretensioned prestressed reinforced concrete (PRC) bridge structures is a serious problem in the United States of America. Since 2000, the use of fiber-reinforced polymer (FRP) is well studied and has become an accepted method to rehabilitate concrete bridges. Design engineers use the ACI 440.2R-17 to determine strength requirements. Additionally, evaluating the deflection of strengthened PRC members is required during the restoration/strengthening design. ACI 440.2R-17 relies on ACI 318-19 for deflection calculations and limits prestressing from yielding under service load levels. This dissertation examines the application of the effective moment of inertia equation given in ACI 318-19 for the determination of deflection after cracking of PRC beams externally strengthened with carbon fiber reinforced polymers (CFRP). The results reported in this dissertation deal with the behavior of partially prestressed concrete beams strengthened with high strength composites. The three major parts discussed are experimental work, analytical investigations, and a parametric study. Experimental results obtained by other researchers were used to verify the results of the analytical procedures developed. The parametric study provides information on the moment-curvature and load-deflection behavior of strengthened pretensioned prestressed concrete flexural members externally strengthened with fiber-reinforced polymers that can be obtained for various concrete strengths, reinforcement ratios, and varying cross-sections. An analytical model was developed to predict the flexural rigidity of pretensioned, partially prestressed concrete beams that are externally strengthened with high strength composites. CFRP sheets were used for the derivation of equations. The proposed model is based on principles of mechanics and the sectional equations available for the analysis of partially prestressed beams. The model is applicable to the full range of prestressed concrete members covering partially and fully prestressed concrete, straight or harped strands, with or without supplemental mild-reinforcing steel, and varying loading conditions. The procedure can be used to generate the entire load-deflection response and through performing the moment-curvature analysis and estimation of stresses and strains in addition to computing the effective flexural stiffness of the strengthened prestressed member. Comparisons of experimental and analytical results show that deflection can be predicted with good accuracy using the developed modified effective moment of inertia equation. The parametric investigation was conducted on the effect of the basic variables namely, cross-section, concrete compressive strength, prestressing steel ratio, amount of carbon fibers, modulus of elasticity of prestressing steel-to-modulus of elasticity of CFRP ratio, modulus of elasticity of carbon fiber composite, spans, and shear span-to-span ratios. The goal of this investigation was conducted to understand the effect of CFRP strengthening to the flexural stiffness. Rectangular cross-sections with straight bonded prestressing tendons strengthened with 1 to 5 layers of unidirectional carbon sheets were analyzed in the parametric study. Lastly, the application of the proposed effective moment of inertia equation to bonded, pretensioned prestressed members, with harped strands depressed at midspan, externally strengthened with CFRP is examined in comparison with the experimental and analytical response curves