The application of steel joists to floor construction can be traced back more than 100 years to the use of a sheet steel joist in the State of New York Bank Building in 1855. Since that time various forms of joists have been developed and exploited. As a result, two general types of joists are now on the market: a) Solid web joists; b) Open web, or truss type, steel joists. In order to determine the strength, stiffness, and behavior of these structural sections under load, representative open web steel joists have been tested at the University of Miami, School of Nursing Building (building about to be demolished). Using two hydraulic jacks to apply the load at eight different locations along the strip, the assessment of the ultimate structural performance of the floor system to positive moments in correspondence of selected strips was possible. After analyzing the data collected from the sensors through the data acquisition system, it was concluded that the results obtained from the Finite Element model were consistent compared to the results obtained from the experimental approach, helping to understand better the behavior of this structural system. A recommendation for further study is enclosed.

A parametric study was performed to determine the effect of flexible foundations on the response of timber shear walls. Timber shear walls, which typically consist of structural-use panels, such as plywood or oriented strand board (OSB), attached to a frame made from dimension lumber with dowel-type fasteners such as nails, provide resistance to lateral loading for many low-rise structures in North America. Research performed on shear walls has assumed that a wall is supported by a relatively stiff foundation, such as a concrete block wall, along the entire length of the wall. However, walls are sometimes supported by a relatively flexible foundation, such as a floor joist, which would alter the stiffness, and therefore the response of the wall. Research on flexible foundations is limited at best, and there is a string need to examine the behavior of shear walls on flexible foundations. The study consisted of creating a shear wall numerical model, varying the conditions at the foundation of the model, and analyzing the model when subjected to both monotonic and dynamic loading for each foundation. The system modeled corresponded to a 2.4 m (8 ft) high by 3.7 m (12 ft) long shear wall supported by and parallel to a 7.3 m (24 ft) long joist with hold-downs at each chord of the wall. The joist was supported at each end, with one chord of the wall at an end of the joist and the other chord located at the center of the joist. Eleven joist cross-sections, with sizes determined based on deflection criteria ranging from L/180 to L/720, and a rigid base were included in the study, along with three different hold-down bolt sizes, for a total of thirty-six different foundations. The wall model was analyzed using WALSEIZ1, which is a modified version of the finite element program WALSEIZ (White and Dolan, 1995). Maximum displacements, internal forces, and maximum load were recorded when the model was subjected to monotonic loading, while the maximum displacements and base shear were recorded when the model was subjected to dynamic loading. Results from the study were examined to determine if modifications to the current design practices should be considered. / Master of Science

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The behavior of composite steel joists with various degrees of shear connection is investigated. The results of eight full-size composite joist tests, conducted as a portion of the study, are presented. Joist spans range from 24 ft. to 30 ft. and depths from 8 in. to 18 in. Six types of mechanical connectors provide horizontal shear transfer capacity. Steel deck supported slabs, from 3 in. to 4 in. thick, are used for all tests. The results of the experiments are used to evaluate the flexural strength and associated failure modes of partially composite and fully composite joists. The results of each test are compared to theoretical calculations based on an ultimate strength flexural model. The joists are classified by how the provided amount of shear connection compares to the bottom chord yield force and by how the provided amount of shear connection in conjunction with the top chord capacity compares to the bottom chord yield force. Behavior typical of each classification is discussed. Correlation with previously conducted composite joist tests of similar configuration is also discussed. / Master of Science

The goal of this research was to study several methods of generating composite action using open-web joist-girders, designed and manufactured by Nucor Corporation. In addition to comparing the relative performance of these systems, it was intended to determine whether the current accepted design procedure for composite joists could be extended to joist-girders. / Master of Science

With the development of lightweight steel beam and steel joist-concrete slab floor systems, floor vibration problems are becoming more and more prevalent. This paper presents the experimental and analytical study of the vibration characteristics of steel joist and joist-girder members. Three aspects were studied to prevent and correct vibration problems. Long span-joists and joists-girders, with a span greater than forty feet, have not been considered for Murray's criterion and the Modified Reiher-Meister scale. This study shows that these two methods can be used to predict the acceptability of a long span floor system to the occupants. Modifying existing floors so that they will be considered acceptable to the occupants is a concern for existing vibrations problems. This study has shown that by adding additional steel to the bottom chord of the joists and/or joist-girders the floor system frequency can be modified so that the floor will be considered acceptable to the occupants. Predicting the effective moment of inertia of joists and joist-girders is essential to accurately predict the frequency and displacement of a floor system due to human occupancy. This paper presents two new equations that can be use to predict the effective moment of inertia of round web joist and angle web joist and joist-girders based on their span-to depth ratio. / Master of Science

One of the major challenges of engineering is finding the proper balance between economical and safe. Currently engineers at Nucor Corporation have ignored the additional lateral bracing provided by standing seam roofing systems to joists because of the lack of methods available to quantify the amount of bracing provided. Based on the results of testing performed herein, this bracing is significant, potentially resulting in excessively conservative designs and unnecessary costs. This project performed 26 tests with Vulcraft joists in a pressure box to investigate the effects of how many variables influence the lateral bracing provided to joists from standing seam roofing systems, including the variables joist length, panel gauge, clip height, thermal block presence, insulation thickness, and top chord size. Two methods were developed to account for this additional bracing: finite element computer modeling and an application of the Rayleigh-Ritz method called the Column-on-Elastic-Foundation Method. Variables influencing the pressure at failure, namely chord size and deck gauge, were those with the greatest effect on additional lateral bracing provided from standing seam roof systems. It was determined that higher roof stiffness values and higher failure pressures yield shorter effective lengths.

This work deals with the bearing capacity of wood based I-joists Finite element models were analyzed to determine the bearing capacity of I-joists, using the finite element software Abaqus CAE. The purpose of this study is to compare the results from the developed FE-models with experimental results, and with a previously proposed design formula. To perform the analyses finite element models were created. The model consists of three parts:, the web (made of shell element), the flanges and steel plates used at the supports and loading points (made of solid elements) To determine the bearing capacity of the I-joist two types of analyses were performed, a linear buckling analysis to check the risk of web buckling and a static (stress) analysis to check the risk of splitting of the flanges. This study shows that the steel plate length, in some cases, has little or no impact on primarily the splitting load. Furthermore, the buckling load decreases as the depth of the beam increases, the influence of the depth being proportional to 1/h2. The depth of the beam has no impact on the risk of splitting of the flange.

Engineered wood I-joists have grown in popularity as flooring and roofing structural systems in the past 30 years, replacing solid sawn lumber joists. Typical wood I-joists are manufactured with a very slender section, which is desirable to achieve higher flexural capacities and longer spans; however, this makes them susceptible to lateral torsional buckling failure. Continuous beam spans and uplift forces on roof uplift are potential scenarios where lateral instability can occur and reflects the need to investigate the lateral torsional buckling behavior of wood I-joists. Within this context, the present study conducts an experimental investigation on the material properties and the critical buckling load of 42 wood I-joist specimens. A 3D finite element model is built using the experimentally determined material parameters to effectively predict the observed buckling behavior of the specimens while also accounting for initial imperfections in the joists. The adequacy of other analytical models to predict the critical buckling load of wood I-joists are also investigated. It is demonstrated that the American design standard underestimates the critical buckling load of wood I-joists while the classical theory provides an adequate estimate of the buckling capacity. Furthermore, the effects of initial imperfections on the lateral torsional buckling behavior are discussed. The developed and verified FE model is used to reproduce the nonlinear buckling behavior of the wood I-joist and also to provide an accurate estimate of the lateral torsional buckling capacity using the linear buckling analysis.

The aim of this thesis is design and assessment of the steel structure of the multi-storey administration center in Martin. Floor plan dimensions are in the shape of a square 40 x 40 m. Column spacing is 8mx8x. Building has 6 floors and total height is 22,2m. Floor and roof structure is made of steel-concrete composite slab . Part of the work is analyze two different versions. Version A has longitudinal rigidity due to truss bracing. Rigidity of Version B has is ensured by frame conections between beams and columns.Version A was selected as better solution. All parts, except truss braicing is made of rolled beams. The whole structure is made of steel S355.