Browsing by Subject "Reinforced concrete construction--Testing"

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Diagnostic testing for improved load rating of reinforced concrete slab bridges
(1997) Bussell, Loyl Clyde, 1965-; Wood, Sharon L.
There are a large number of reinforced concrete slab bridges in Texas that were constructed in the 1950s and 1960s. Although most of these bridges were designed for less than the current legal load, they are still in service and performing adequately. Currently the bridges in Texas are load rated based on a procedure similar to the original design procedure. These procedures are very conservative and result in low load ratings for slab bridges. In order to take advantage of this inherent conservatism, a method of determining a better estimate of the capacity of these bridges is needed. This study addresses the possibility of load testing reinforced concrete slab bridges in order to verify that there is adequate capacity to increase the allowable loads. A typical slab bridge was field tested. The test procedures are discussed, and the measured results are presented and evaluated
Non-destructive evaluation of gravity load carrying capacity and lateral load damage of reinforced concrete slab-column connections
(2006) Argudo, Jaime Fernando; Jirsa, James O.
The objective of this study was to develop a procedure to quantify the load carrying capacity of a slab-column connection as a function of the structural damage. To fulfill this objective, guidelines for damage assessment of reinforced concrete flat-plate buildings were developed. The intent of the guidelines was to assist engineers assess lateral load damage in the field and estimate the gravity load carrying capacity of the slab-column connection after an earthquake. The relationship between gravity load carrying capacity and degree of lateral load damage was studied in laboratory. Gravity load tests were conducted on four slab-column connections and lateral load tests on five slab-column connections. It was found that when the degree of damage was slight to moderate, there was no reduction in the gravity-load-carrying-capacity of the connection. However, when the degree of damage was severe, a reduction in the gravity load carrying capacity should be expected. The degree of lateral load damage was defined into four categories (slight, low, moderate and severe) and was characterized by the extent of cracking, stiffness degradation and yielding of the reinforcement in the slab-column connection. The degree of lateral load damage was also a function of the lateral drift level experienced by the structure. Four assessment techniques were utilized to infer the lateral drift level. The techniques were based on results from visual observations and nondestructive testing conducted on four slab-column connections. Slab vertical deflection, crack density, crack depth, extent of areas of concrete delamination, and Seismic Wave Attenuation (SWA) measurements provided useful information for estimating the amount of damage due to cycles of lateral drift. The SWA method is a non-destructive method that has not been used previously for assessing damage in slab structures. The guidelines provide an empirical approach for estimating the gravity load carrying capacity of a slab-column connection based on three steps: (1) assessment techniques for inferring the drift level experienced by the structure, (2) correlation of the inferred drift level with the degree of lateral load damage, and (3) estimation of the gravity load carrying capacity of the connection based on the degree of lateral load damage.
Progressive collapse behavior of reinforced concrete structures with deficient details
(2006-08) Kim, Hyunjin, 1974 Jan. 21-; Jirsa, J. O. (James Otis)
Damage from abnormal loading such as explosion, bombing, and sudden external impacts on elements of a structure can range from a loss of individual elements to total collapse. Progressive collapse has been a concern for many years, but recent acts of terrorism including the destruction of the World Trade Center and major damage to the Pentagon have renewed demand for methods to improve behavior of structures under these abnormal events. Progressive collapse can be defined as damage disproportional to the triggering mechanism. Design of structures against progressive collapse has not been an integral part of structural design. However, some codes such the GSA and UFC guideline have detailing requirements to reduce the likelihood of progressive collapse. It is difficult to predict the manner in which progressive collapse will propagate because the nature of loadings or triggering events are not well defined, and behavior of structural elements during a progressive collapse is not understood. In this study, three-dimensional nonlinear static and dynamic analyses of structures prone to progressive collapse are vii conducted using commercially available programs. The analysis is assumed to be independent of the cause of damage. The initial objective is to simulate structural behavior when load-carrying members are removed under the effects of abnormal loadings. After the critical member is removed, redistribution of the forces to other elements is investigated. In addition, the capability of resisting redistributed loads is examined to determine if adjacent elements participate in producing a progressive collapse. Dynamic effects due to removal of a critical column suggested by the GSA and UFC guidelines are compared with analytical results. The response of a robust structure is compared with the response of a structure with deficient details. When a critical column is removed, structural details related to connections, insufficient transverse reinforcement for shear in beams, and lap splices in columns are studied to demonstrate how components may be affected by removal of critical elements.
Seismic performance of full-scale reinforced concrete columns
(2005) Bae, Sungjin; Bayrak, Oguzhan
The deformation capacity of a concrete column can be expressed by using different ductility parameters such as curvature ductility, displacement ductility or drift capacity. However, little research has been conducted into the relationship among different ductility parameters. The objectives of this research are (1) to investigate the relationship among various ductility parameters by considering the effects of shear spanto-depth ratio and axial load level and (2) to develop methods and procedures that can be used to estimate the deformation capacity of reinforced concrete columns. Five full-scale reinforced concrete columns were tested at The University of Texas at Austin. Test results indicated that the shear span-to-depth ratio and axial load level were important parameters influencing the relationship among various ductility parameters. Measured plastic hinge lengths of column specimens were also affected by the shear span-to-depth ratio and axial load. The plastic hinge length of concrete columns was investigated by studying the compressive strain profile of the core concrete. An analytical procedure was used to study the effect of various parameters on plastic hinge length. Based on the results of the experiments and a parametric study, a new expression that can be used to estimate plastic hinge lengths was proposed. Two methods that can be used to predict the deformation capacity of reinforced concrete columns were developed. One of these methods can be considered as a state-ofthe-art analytical method, which employs various phenomenological models for confinement of concrete, reinforcing bar buckling, reinforcing bar slip and shear deformations. The other method consists of simple expressions derived by studying the lateral load response of columns as influenced by the P-Δ effect. The use of the rigorous analytical method provided reasonably accurate estimates for the deformation capacity of over one hundred columns tested by various researchers. The use of simple expressions, on the other hand, traced the lower-bound of the measured drift capacities of these columns. The simple expression is recommended for use in performance-based design of reinforced concrete columns.