Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
1,402
result(s) for
"Columns Design and construction."
Sort by:
Eccentric Behavior of Full-Scale Reinforced Concrete Columns with Glass Fiber-Reinforced Polymer Bars and Ties
Recent years have witnessed noticeable advances in evaluating the behavior and contribution of fiber-reinforced polymer (FRP) bars in concrete columns under concentric loading. In contrast, there is a scarcity of investigation available in the literature on full-scale concrete columns reinforced with FRP bars and ties under combined axial and flexural loads. This paper reports experimental data on the behavior of square concrete columns reinforced with deformed and/or sand-coated glass FRP (GFRP) bars and ties. A total of 12 full-scale concrete columns 16 x 16 in. (405 x 405 mm) in cross section and 80 in. (2000 mm) in height were constructed and tested up to failure. The columns were loaded under four different levels of eccentricities to develop axial load-moment (P-M) interaction diagrams. The influence of different GFRP bars of comparable quality on the performance of the columns and their P-M interaction diagrams were assessed. In addition, columns reinforced with conventional steel bars and ties were introduced into the test matrix as references. The load-strain behavior for the concrete, bars, and ties; load-deformation curves (axial and lateral); and experimental P-M interaction diagrams are presented herein. The impact of the compressive behavior of longitudinal GFRP bars versus steel bars was assessed. The test results indicate that the specimens reinforced with two comparable types of GFRP bars (deformed and/or sand-coated) under different levels of eccentricity behaved similarly to their steel reinforced concrete counterparts. Design strain limits were proposed to define the failure-mode mechanisms of the GFRP specimens on the P-M interaction diagram. Keywords: column; compression; eccentric; failure mode; glass fiber-reinforced polymer reinforcement; P-M interaction diagram.
Journal Article
Experimental Behavior of Glass Fiber-Reinforced Polymer-Reinforced Concrete Columns under Lateral Cyclic Load
The present study addresses the feasibility of reinforced concrete columns totally reinforced with glass fiber-reinforced polymer (GFRP) bars achieving the drift requirements specified in various codes. Eleven full-scale concrete columns--two reinforced with steel bars (as reference specimen) and nine totally reinforced with GFRP bars--were constructed and tested to failure under quasi-static reversed cyclic lateral loading and simultaneously subjected to constant compression axial load. The reported test results clearly show that properly designed and detailed GFRP-reinforced concrete columns could reach high deformation levels with no strength degradation. The results also show that the achieved drift satisfies the limitation in most building codes. Acceptable levels of energy dissipation and ductility parameters, compared to the steel-reinforced columns, were observed. The promising results can provide impetus for constructing concrete columns reinforced with GFRP and constitute a step toward using GFRP reinforcement in lateral-resisting systems such as reinforced concrete frames. Keywords: concrete columns; ductility parameters; energy dissipation; glass fiber-reinforced polymer (GFRP) bars; hysteretic response.
Journal Article
Behavior and Design of Slender Rectangular Concrete Columns Longitudinally Reinforced with Fiber-Reinforced Polymer Bars
Fifteen slender rectangular reinforced concrete (RC) columns with longitudinal glass fiber-reinforced polymer (FRP) bars were tested under compression in this paper. Results showed that all columns with varying length-to-depth ratios and eccentricity ratios failed by concrete crushing, and no rupture of FRP bars was experienced. Moreover, validated nonlinear finite element model was used to perform a detailed parametric study of 27,000 FRP-RC columns using Opensees. Based on parametric analysis results in conjunction with the moment magnifier method, a refined design equation of the effective flexural stiffness EI was then statistically derived to determine the second-order bending moments. On this basis, a design approach was proposed for slender FRP-RC rectangular columns, in which the contribution of FRP bars in compression to the strength of sections was taken into account. The proposed approach is more consistent and accurate than existing design methods by comparing their predictions with available experimental results of 46 columns. Keyword: design approach; effective flexural stiffness; fiber-reinforced polymer (FRP) bars; finite element (FE) analysis; rectangular column; reinforced concrete.
Journal Article
Seismic Performance of Precast Columns with Mechanically Spliced Column-Footing Connections
This paper presents the results from a large-scale experimental study that was conducted at the University of Nevada, Reno, NV. Five half-scale bridge column models were constructed and tested under reversed slow cyclic loading. The study focused on developing four new moment connections at column-footing joints for accelerated bridge construction in regions of high seismicity. The new connections were employed in precast columns, each using mechanical splices to create connectivity with reinforcing bars in a cast-in-place footing. Two different mechanical splices were studied: an upset headed coupler and a grout-filled sleeve coupler. Along with the splice type, the location of couplers within the plastic hinge zone was also a test variable. All precast models were designed with the intent to emulate conventional cast-in-place construction and, thus, were compared with a conventional cast-in-place test model. Results indicate the behavior of these new connections was similar to that of conventional cast-in-place construction with respect to key response parameters, although the plastic hinge mechanism could be significantly affected by the couplers. [PUBLICATION ABSTRACT]
Journal Article
Update to Shear Strength Provisions for Concrete Columns in ACI CODE-369.1-22
This paper presents important revisions to the shear strength provisions for seismic assessment of reinforced concrete columns in ACI CODE-369.1-22. A new formulation based on a strut-and-tie model is introduced to expand the range of application of existing provisions to include columns with shear span-depth ratios lower than 2. Revisions are proposed to the slender column provisions to improve their precision, reduce estimate bias, and eliminate instances where they produce unconservative estimates of shear strength. The proposed relations were calibrated using shear strength data from 94 shear-critical rectangular columns subjected to load reversals from a database developed at The University of Texas at San Antonio. Keywords: cyclic loadings; diagonal tension; rectangular concrete columns; shear strength; short columns; slender columns; strut-and-tie; truss model.
Journal Article
Constructability-based multi-objective optimization with machine learning-enhanced meta-heuristics for reinforcing bar design in rectangular concrete columns
Optimization of reinforcing bar (rebar) design represents a preponderant factor in reducing material usage and wastes for reinforced concrete (RC) structures. The assessment of constructability of such rebar designs is crucial to improve their practicality and reduce construction costs, which makes the problem multi-objective (MO). However, when applying optimization methods for the design of rebar in RC structures, little attention has been paid on columns, in comparison to beams and slabs. Meta-heuristic algorithms (MA) have been the ones mostly deployed for these types of elements, which have proven to be of high computational cost. Additionally, an existing gap in the literature as to how to relate the design and construction stage of rebar in RC structures through constructability analysis is evident. In this regard, research has been focused mainly at the building level but not at the element level. This works presents a novel algorithmic framework using Machine Learning (ML)-enhanced meta-heuristics for the optimal design of rebar on rectangular RC columns. To assess the constructability of the resulting rebar layouts a Buildability Score (BS) model at the element level is proposed. The complexity analysis of rebar design under the constructability restrictions, through combinatorial optimization (CO), is used to assess the global time efficiency of the framework. The Non-Sorting Genetic Algorithm II (NSGA-II) was deployed for showcase and five different ML algorithms were used to enhance it, namely the k -NN classifier, SVM regression, ANN, Gauss Process (GP) regression, and Tree Ensembles (TE), where the latter three showed the best performance.
Journal Article
Ultra-High-Toughness Concrete Retrofitted Boundary Column Shear Walls: Tests and Capacity Prediction
The rapid growth of the construction industry in Asia and the consequent updating of design specifications put forward higher performance requirements for structural components, which results in a large number of existing shear walls that are not compliant with the current seismic standards. A prospective retrofitting method, which is based on replacing the existing boundary concrete or attaching external boundary columns to nonconforming shear walls, is experimentally studied. Four shear-wall specimens were designed according to the current Chinese design code: one using plain concrete boundary columns and three using ultra-high-toughness boundary columns (UHTBCs), adopting three different strengthening strategies relevant to the boundary size and the connection form. Cyclic performance, damage patterns due to UHTBCs, and connection form are discussed based on the experimental results, from which it was ascertained that shear walls with UHTBCs show improved seismic performance, compatible with the requirements of the current seismic design code, even for the reduced-boundary UHTBCs and non-connection specimens. The predictive equation for the sectional moment capacity of shear walls with UHTBCs was discussed as a practical tool for retrofitting applications. This study highlights the most important features of a rapid retrofitting measure to improve the resilience of existing nonconforming shearwall structures, while also proving to be an effective measure for newly constructed structures. Keywords: boundary columns; cyclic loading test; retrofitting; seismic performance; shear wall; ultra-high-toughness.
Journal Article
Seismic Performance of Corroded Precast Reinforced Concrete Columns with Intentional Debonding
Accelerated bridge construction (ABC) has emerged as a faster method of bridge construction. Reinforced concrete (RC) columns in bridges constructed using ABC methods remain vulnerable to corrosion, which impacts their performance during large earthquakes. Three specimens were constructed using ABC methods to investigate the effects of corrosion; two of these specimens were subjected to accelerated corrosion procedures to simulate moderate and severe corrosion levels. The longitudinal steel bars experienced 11% and 24% mass loss, while the steel spirals experienced 18% and 40% mass loss for moderately and severely corroded specimens, respectively. The severely corroded specimen experienced buckling of longitudinal bars at 5.0% drift ratio. Corrosion severity impacted column displacement capacity; the first reinforcing bar fractured at lower drift ratios in the corroded specimens, both of which experienced reduced displacement ductility and hysteretic energy dissipation. The importance of considering corrosion in evaluating seismic performance of RC bridges constructed using ABC methods is demonstrated. Keywords: accelerated construction; corrosion; debonding; ductility; mass loss; precast; reinforced concrete (RC); seismic.
Journal Article
Cyclic Behavior of Columns with Proposed Arrangement of Longitudinal Reinforcement
This research proposes a standardized arrangement of longitudinal reinforcement using Grade 690 MPa (100 ksi) high-strength steel and D32 (No. 10) or D36 (No. 11) large-diameter threaded bars to alleviate reinforcement congestion and construction difficulties. Four full-scale column specimens with the proposed standardized arrangement were tested using double-curvature lateral cyclic loading to examine their seismic performance. Test results showed that all the columns exhibited a combined axial and flexural failure mode, with ultimate drift ratios ranging from 4.07 to 5.98%, ratios of measured to nominal moment strength based on actual material strengths ranging from 1.18 to 1.51, and relative energy dissipation ratios satisfying the requirement of ACI 374.1-05. No shear or bond-splitting failures were observed. Based on the test data from this research and the literature, two modifications were proposed in the calculation of [??] to relax the requirement of 1.25[Please download the PDF to view the mathematical expression] as required by ACI 318-19. Keywords: bond splitting; columns; high-strength reinforcement; large bar; longitudinal reinforcement; seismic.
Journal Article