The Illinois Institute of Technology Research Institute (IITRI) composite compression test method is probably the most widely accepted as producing accurate results. Difficulties associated with the application of this method, however, have fueled continued research into alternate methods. In this study, the Wyoming End-Loaded Side-Supported (ELSS) test scheme was investigated in a combined shear/end loaded mode. This system was examined experimentally and analytically to establish the method as a reasonable alternative to IITRI testing. Combined shear/end loading was accomplished by applying a controlled amount of clamping force to the stabilizing blocks, allowing them to transmit shear force to the coupon faces through friction. The fabrication of test specimens from a BASF graphite IBMI material system is described in detail, including the application of a novel "press-clave" processing system developed at Virginia Tech. This system allows for cost-effective manufacture of flat panels under conditions similar to autoclave processing. For the material system employed in this study, this process proved superior to conventional hot press processing. Experimental results include strengths and failure modes for both tabbed and untabbed coupons tested by the combined loading ELSS method, and these data are compared to the results by the IITRI method. Strength was found to increase with increasing clamping, but reached a maximum with both untabbed and tabbed specimens. The maximum strength achieved with untabbed specimens was still significantly below the IITRI value, but the tabbed specimens reached strengths comparable to the IITRI data. The failure mode also changed with increased clamping, from end crushing to brooming with untabbed specimens, and from end crushing to shear failure with tabbed specimens. As the strength and failure mode achieved with the combined loading ELSS method using tabbed specimens are both similar to those seen in the IITRI tests, this modified technique can be considered equivalent to the IITRI method. Preliminary data from tests using novel nonbonded tabs were also similar to those given by the IITRI method. The finite element method was used to analyze the effect of increasing the clamping force. Competing effects of locally complex and severe stresses at the coupon end and a stress concentration which develops at the end of the gage section were shown to limit the maximum strength. Tabs appear to reduce the stress concentration while further decreasing the stresses at the end, allowing results comparable to those given by the IITRI method to be achieved. / Master of Science

There are two basic methods used to analyze and design reinforced concrete members for shear, the American Concrete Institute Code method (used in the United States) and the truss model method (used in different European Codes and in the Canadian Codes). The ACI Code method is a semi-empirical solution since it builds on fitting actual test results to the analytical mechanism method. Although it will lead to safe results, the ACI method lacks a physical model to represent the actual forces in the beam. For this reason, attention is increasingly being given to develop a mechanical-mathematical model to show the actual behavior of the beam failing in shear. The truss model theory provides a more promising way to treat shear since it can model the structural action in the beam. It was first proposed by Ritter and Marsh at the turn of the twentieth century. The concept has been extended by recent work of Lampert and Thürlimann (1971), Collins and Mitchell (1980), MacGregor (1988), and others. The purpose of this study is to compare the ACI method and the truss model method for the design of reinforced concrete slender and deep beams. The results of this study suggest that the truss model is better suited for the design of deep reinforced concrete beams because it models the dominant mechanism that happens in the beam which is the force transfer from load to reaction by the direct compression struts. For slender reinforced concrete beams, either method is suitable for design. / Master of Science

The feasibility study of subscale notched specimens to determine the shear response of composites is presented. The investigation consists of finite element analyses, conventional strain-gaged testing, and photomechanics experiments. Several notch geometries of the subscale specimens are studied, the standard 900 V -notch, U-notch, and circular notch. The investigation is performed on two different material systems, a standard high performance graphite/epoxy (AS4/3501-6) material and an SMC R-28 material reinforced with 28% volume fraction strand glass fiber. The moduli obtained from the subscale specimens are compared with those obtained from the standard specimens. Different degrees of twisting observed in testing the sub scale specimens are discussed. Numerical and experimental results of the SMC R-28 materials are presented. The dependence of the measured shear modulus on the relative orientation of the specimen in the panel is identified. The application of the subscale, circular notched specimens to obtain the shear modulus of the SMC material is discussed. / Master of Science

The program described in this paper is capable of determining horizontal and vertical shear resultants at any point within a one, two, or three plate system where plates are joined at ninety degree angles. Program options allow for tapered walls and combinations of both uniform and triangular loads for each type plate problem. The three plate solution process automatically imposes boundary conditions conducive to one quarter of a monolithically constructed rectangular tank system due to tank symmetry. The plate dead weight effects and their associated shear force upon the floor plate are also accounted for when analyzing the three plate problem. Difficulties are encountered in the refinement of plate finite element meshes due to program computer storage requirements. The result is that derived resultant values do correlate with published solutions for one or two plate problems. Three plate problems require at least an 8x8 plate mesh, 8.7 megabits computer storage, to provide acceptable resultant accuracy. / Master of Science

Shear lag is a non-uniform distribution of stress resulting when all cross sectional elements are not directly connected. This phenomenon renders the cross section only partially effective in resisting tensile loads. In this investigation, both experimental and analytical studies were conducted to ascertain the shear lag coefficients to be used in design of welded tension members by the AISC Specifications [1989]. Four types of specimens (angles, plates, channels, and tees), were tested, each with three weld configurations (longitudinal welds only, transverse welds only, and a combination of both transverse and longitudinal welds). The specimens were statically loaded in tension to failure. Experimental shear lag coefficients are presented and compared to theoretical values. / Master of Science

This thesis is concerned with the buckling problem of a cantilever thin plate with its tree end subjected to uniform shear. The same problem waa originally solved by Prandtl in 1899, based on the equilibrium condition of a deep beam. The author baa used the energy method based on the thin plate theory to attack the problem. After the displacement is assumed, the potential energy can be formulated. From the condition that the potential energy assume a minimum value in an equilibrium configuration, results a system of n linear homogeneous algebraic equations ot n parameters which are introduced in the assumed displacement. For a non-trivial solution, the determinant of the coefficients must vanish. This gives a characteristic equation from which the buckling load is determined. The author has obtained a curve for maximum stress at buckling state, which shows that the result 1a better than that obtained by Prandtl in certain cases. The energy method has been generalized to a three dimensional problem to consider the displacement in all directions. / Master of Science

A series of resonant column and torsional shear (RCTS) and large scale resonant column (LSRC) tests were performed to investigate the dynamic properties (shear modulus and material damping ratio) of municipal solid waste (MSW). the MSW materials were recovered from the Tri-Cities landfill adjacent to the San Francisco Bay in California. A total of 30 specimens 2.8-in. (71.1-mm) and 6.0-in. (152.4-mm) of old, fresh, and mixed MSW were reconstituted in accordance with established sample preparation procedures. Ten of specimens were small-diameter (2.8-in. (71.1-mm)) RCTS specimen and 20 specimens were larger (6.0-in. (152.4-mm)) LSRC specimens. Dynamic laboratory measurements were performed in the linear and nonlinear strain ranges. Test parameters affecting the dynamic properties in the linear range included: (1) duration of confinement, (2) isotropic total confining pressure, [sigma]o, (3) excitation frequency, f, and (4) specimen size. Other test parameters affecting dynamic properties in the nonlinear strain range were: (1) shearing strain amplitude, [gamma], (2) isotropic total confining pressure, (3) overconsolidation ratio, (4) number of loading cycles, and (5) excitation frequency. In addition, the effects on dynamic properties of MSW specimens of material parameters such as (1) waste composition, (2) water content, (3) unit weight of waste, and (4) particle size were evaluated. The total unit weights of old, fresh, and mixed MSW specimens were estimated during testing in the RCTS and LSRC devices. These estimated total unit weights in the laboratory were compared with those measured at other MSW landfills and were found to generally be less than the field measurements. At a given [sigma]o, Gmax decreases with decreasing weight percentage of soil-size (passing the 3/4-in. (19.1-mm) sieve) material. However, Dmin increases slightly with decreasing weight percentage of soil-size material. Another relationship was developed between estimated total unit weight, [gamma]t, and confining pressure, including weigh percentage of soil-size material. The Vs profiles of old, fresh, and mixed MSW specimens obtained in the laboratory tests were compared with those measured at other MSW landfills in situ. The 62 to 76% soil-size material groups are in good agreement with in-situ Vs profiles. The variation in normalized shear modulus and material damping ratio curves were patterned after the Darendeli model (2001) for different weight percentages of soilsize material. An empirical relationship between normalized shear modulus (G/Gmax) and modified material damping ratio (D-Dmin) was developed in the nonlinear strain range. As part of collaborative research project, nonlinear shear modulus reduction and material damping curves generated by The University of Texas at Austin (UT) and The University of California at Berkeley (UCB) were compared according to different weight percentages of soil-size material. Furthermore, nonlinear shear modulus reduction and material damping ratio curves generated by UT were also compared with ones previously proposed by other researchers.

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Lomolding is a new process similar to injection moulding. In this thesis a numerical model of the polymer flow into the cavity is presented. The model is used to compare the two processes with each other. Lomolding and injection moulding were modelled numerically with the finite element method. The model was an axisymmetric model and takes phenomena such as generalised Newtonian flow, free surfaces, moving boundaries and solidification into account. The processes’ characteristics that were compared are the cavity pressure, shear rate and shear stress. Improvements in these characteristics will result in lomolding having smaller machines, less fibre breakage and a better potential for in-mould-decoration. The thesis shows that lomolding has substantially lower shear rates and shear stresses than injection moulding. The model was also used to investigate certain machine design aspects, and to gain a better understanding of the polymer flow in lomolding. / AFRIKAANSE OPSOMMING: Lomoldering is ’n nuwe proses soortgelyk aan inspuitgiet. Hierdie tesis beskou ’n numeriese model van die polimeervloei soos dit in die gietholte invloei. Die model word gebruik om die twee prosesse met mekaar te vergelyk. Lomoldering en inspuitgiet is numeries gemodeleer met die eindige-elementmetode. Die model is aksiaal-simmetries en neem verskynsels soos Newtoniese vloei, vrye oppervlakke, bewegende grense en stolling in ag. Die proses-karakteristieke wat vergelyk is, sluit die gietholtedruk, vervormingstempo en skuifspanning in. Verbeterings in hierdie karakteristieke sal meebring dat lomoldering kleiner masjiene nodig sal hê, minder veselskade sal veroorsaak en meer versoenbaar met in-gietholte-versierings sal wees, vergeleke met inspuitgiet. Die tesis toon dat lomoldering laer vervormingstempo’s en skuifspanning het, in vergelyking met inspuitgiet. Die model is ook gebruik om sekere masjienontwerpaspekte te ondersoek, en om die polimeervloei in lomoldering beter te verstaan.

Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2006. / Some experiments utilizing the shear capacity of Engineered Cement-based Composites (ECC) have suggested that elimination of shear reinforcement is feasible when the concrete matrix is replaced by ECC. However, actual application and more rigorous cost analysis are prevented by the fact that the shear stress and strain properties of ECC have not yet been characterized as accurately as the tensile properties. This study focuses on the investigation of the shear property of ECC. The study starts with a survey and comparison of existing shear tests for composite materials. The Iosipescu shear test concept is chosen as the most objective method for ECC, and subsequently, modified for specific application on ECC by simple analytical design and finite element refinement. The modified Iosipescu shear test method is applied on, four types of ECC specimens with different fibre content (0%, 1%, 2%, 2.5% by volume), which have been cast in specially designed moulds and cured in laboratory conditions. Three phases of shear measurements are used to check the shear test appropriateness and study the shear mechanical properties of ECC. The failure mode is verified in the first phase, detailed measurement of the shear strain and shear stress is performed and recorded in the second phase, and in the third phase more information about the ductility of diagonal cracking is obtained by measurement of the tensile principal deformation. By also conducting direct tensile tests on specimens of the exact same mix, information of both uniaxial tension and shear behaviour is available, from which elastic and shear moduli, as well as Poisson’s ratio of ECC are computed. A first step toward application of this knowledge of the shear behaviour of ECC is taken by studying the response of shear-dominated beams and beam-columns of reinforced concrete and reinforced concrete combined with ECC as the outer crusts. These beams were prepared and tested by other members of the research group of the Division for Structural Engineering of the University of Stellenbosch. It is shown that ECC can indeed successfully replace shear reinforcing steel, due to its shear capacity.

published_or_final_version / Civil Engineering / Master / Master of Philosophy