Typescript (photocopy).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 61-70). Also available via the Internet.

Thesis--Otaniemi. / Thesis statement for v. C. Vol. A has summary in English. Includes bibliographical references.

Four rectangular, isotropically reinforced concrete slabs were constructed and loaded until collapse. All slabs were fixed on three edges with the fourth edge free. Three slabs contained openings at various locations while the fourth remained solid. The magnitudes of deflections were measured during loading and the final yield pattern and ultimate load were compared to those predicted by simple and advanced yield-line theory. An analytical computer program was developed and is presented for quick evaluation of the ultimate load and collapse mode of many types of uniformly loaded slabs by simple yield-line theory. Short specialized programs were also formulated to analyze the experimental slabs, considering the presence of simple corner levers and edge loads around the openings. This resulted in more accurate theoretical predictions and produced estimates of the percent difference between simple and advanced theory predictions. Analysis of the results showed excellent agreement between the advanced theory predictions and the experimental results. / M.S.

Concrete bridge rails are rated according to three performance levels. For classification at a given performance level, the rail must meet specific strength and geometric requirements. To meet the strength requirement, the rail must be able to satisfactorily withstand a transverse concentrated load applied at the top of the rail. This load is called F_t (kips) and is listed for each performance level in the Draft NCHRP Project 12-33 document entitled Development of a Comprehensive Bridge Specification and Commentary. Researchers at the Texas Transportation Institute have developed equations to determine R_w (kips), the total transverse resistance of a rail (which must be greater than or equal to F_t), and L_c (ft), the critical length of wall failure (Hirsch 1978). These equations (referred to as Hirsch equations is this study) were developed by yield line analysis for a constant thickness concrete parapet wall. The purpose of this study is to develop similar equations for R_w and L_c based on yield line analysis of a variable thickness New Jersey concrete parapet wall instead of a constant thickness wall. The results from this study indicate that the Hirsch equations significantly over estimate R_w for variable thickness concrete walls where M_c, the flexural resistance of the wall about the horizontal axis, varies substantially over the height of the wall. This study recommends that an average value for M_c, taken over the height of the wall, be used in the Hirsch equations when this situation arises. / Master of Science

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: Concrete is used in most of the modern day infrastructure. It is a building material for which there exist various design codes and guidelines for its use and construction. It is strong in compression, but lacks tensile strength in its fresh and hardened states and, when unreinforced, fails in a brittle manner. The structural use of synthetic fibres in concrete is investigated in this study to determine its effect on enhancing the mechanical properties of concrete. Slabs on grade are used as the application for which the concrete is tested. The material behaviour is investigated in parallel with two floor design theories. These are the Westegaard theory and the Yield-Line theory. The Westegaard theory uses elastic theory to calculate floor thicknesses while the Yield-Line theory includes plastic behaviour. Conceptual designs are performed with the two theories and material parameters are determined from flexural tests conducted on synthetic fibre reinforced concrete (SynFRC) specimens. Large scale slab tests are performed to verify design values from the two theories. Higher loads till first-crack were measured during tests with concrete slabs reinforced with polypropylene fibres than for unreinforced concrete. It is found that the use of synthetic fibres in concrete increases the post-crack ductility of the material. The Westegaard theory is conservative in its design approach by over-estimating design thicknesses. This was concluded as unreinforced slabs reached higher failure loads than predicted by this theory. The Yield-Line theory predicts design thicknesses more accurately while still accounting for the requirements set by the ultimate- and serviceability limit states. By using SynFRC in combination with the Yield-Line theory as design method, thinner floor slabs can be obtained than with the Westegaard theory. / AFRIKAANSE OPSOMMING: Beton word gebruik as boumateriaal in meeste hedendaagse infrastruktuur. Daar bestaan verskeie ontwerp kodes en riglyne vir die gebruik en oprig van beton strukture. Alhoewel beton sterk in kompressie is, het beton ‘n swak treksterkte in beide die vars- en harde fases en faal dit in ‘n bros manier indien onbewapen. Die gebruik van sintetiese vesels in beton word in hierdie projek ondersoek om die invloed daarvan op die eienskappe van die meganiesegedrag van beton te bepaal. Grond geondersteunde vloere word as toepassing gebruik. Parallel met die materiaalgedrag wat ondersoek word, word twee ontwerpsteorieë ook ondersoek. Dit is die teorie van Westegaard en die Swig-Lyn teorie. Die teorie van Westegaard gebruik elastiese teorie in ontwerpsberekeninge terwyl die Swig-Lyn teorie ‘n plastiese analise gebruik. ‘n Konseptuele vloerontwerp is gedoen deur beide die ontwerpsmetodes te gebruik. Materiaalparameters is bepaal deur buig-toetse uit te voer op sintetiesevesel-bewapende beton. Grootskaalse betonblaaie is gegiet en getoets om die akkuraatheid van die twee metodes te verifieer. Die betonblaaie wat bewapen was met polipropileen vesels het groter laste gedra tot by faling as die blaaie wat nie bewapen was nie. Die vesels verbeter die gedrag van beton in die plastiese gebied van materiaalgedrag deurdat laste ondersteun word nadat die beton alreeds gekraak het. Die Westegaard teorie kan as konserwatief beskou word deurdat dit vloerdiktes oorskat. Hierdie stelling is gegrond op eksperimentele data wat bewys dat onbewapende betonblaaie groter laste kan dra as wat voorspel word deur die Westegaard teorie. Die Swig-Lyn teorie voorspel ontwerpsdiktes meer akkuraat terwyl daar steeds aan die vereistes van swigting en diensbaarheid voldoen word. Deur gebruik te maak van sintetiese vesels en die Swig-Lyn teorie kan dunner betonblaaie ontwerp word as met die Westegaard teorie.