Transverse Ties Research Articles

Short and Long RC Columns with Internal WWM Reinforcement under Concentric and Eccentric Compression

Recently, various types of steel meshes were used as additional internal reinforcement for improving the confinement, ductility, and strength of the reinforced concrete (RC) columns. In this experimental study, a welded wire mesh (WWM) layer was used as an internal reinforcement in addition to the traditional steel reinforcement (longitudinal bars and transverse ties) for short and long RC columns under concentric and eccentric compression. Thirty-six square RC columns with two slenderness ratios λ (height to width ratio) of 9 and 18 were tested under compression with eccentricity ratios e/t (eccentricity to section thickness ratio) of 0, 0.13, and 0.26. The reference columns were traditionally reinforced with longitudinal steel bars and transverse ties with a reference volumetric ratio ρr of 0.44%. The other columns comprised a WWM layer wrapped outside the ties whose volumetric ratio ranged from 0.22% to 0.44%. The results demonstrated that the columns reinforced with a WWM layer in addition to traditional reinforcement showed an improvement in ductility and strength compared to those reinforced with longitudinal bars and transverse ties only. A WWM layer increased the ultimate load of the columns comprising ρr ties by approximately 16% and 9% for short and long columns, respectively. These improvements were proportional to the ties volumetric ratio.

Improving bond performance of ribbed steel bars embedded in recycled aggregate concrete using steel mesh fabric confinement

To investigate the bond behaviour of passively confined-recycled aggregate concrete (RAC), centre pull out tests were carried out on deformed steel bar with a diameter (Ø) of 12 mm. The recycled concrete aggregate (RCA) replacement ratios are 0, 30, 50, and 100 %. To investigate local bond strength, a short anchorage bonded length (La) of 10 was chosen. Steel mesh fabric (SMF) cylinders were used to confine the RAC around the bonded length of the bar. SMFs have diameters of 4Ø and 6Ø. SMF cylinder reinforcement ratios were estimated to be 0, 2.33, 3.04, 3.5, and 4.56 %. To accurately estimate maximal rising ratios in bond strength response owing to RAC confinement using SMFs, all specimens are intended to fail in the pull out mode (rather than the splitting mode). Unconfined and confined pull out specimens were tested for failure mechanism, ultimate local bond strength, bond stress-slip response, and ductility. When compared to similar unconfined specimens, confinement utilising SMFs dramatically improved bond stress-slip behaviour for all specimens including RCA. Ultimate bond strengths of RAC-unconfined specimens were 3.7–24.5 % lower than those of NAC-unconfined specimens, whereas ultimate slips of RAC-unconfined specimens were 25–140 % higher than those of NAC-unconfined specimens. Due to the usage of SMF cylinders at various levels of RCA, the ultimate bond strength of all confined specimens was dramatically increased when compared to unconfined specimens. When compared to a control unconfined NAC-specimen, the ductility of unconfined specimens containing 30 %, 50 %, and 100 % RCA decreased by 5.7, 18.6, and 39.6 %, respectively. In comparison, when compared to similar unconfined specimens, the maximum rising ratios in the ductility of confined specimens containing 0 % RCA, 30 % RCA, 50 % RCA, and 100 % RCA are 44.2 %, 77.9 %, 52.4, and 117.7 %, respectively. A novel proposed formula is developed to compute the ultimate bond strength of RAC while taking into account the influence of concrete grade, RCA content, concrete confinement via SMF, and transverse ties, and its results agree with the experimental results.

Biomechanical State of the Operated Thoracolumbar Junction in Lateroflexion

Summary. The zone of the thoracolumbar junction is the most susceptible to traumatic injuries due to anatomical and physiological features. Accordingly, the stabilization of this section of the spine requires high reliability.
 Objective: to study the stress-strain state of the model of the thoracolumbar spine after resection of Th12-L1 vertebrae with different types of transpedicular fixation under lateroflexion.
 Materials and Methods. Mathematical finite element model of a fragment of the human thoracolumbar spine (Тh9-L5) was developed. We modeled the result of decompressive-stabilizing surgery with total removal of Th12-L1 vertebrae including installation of vertebral body replacing implant and fixation with a transpedicular system using 4 pairs of screws. Lateroflexion was modeled by applying a load of 350 N.
 Results. When evaluating the model without crosslinks and using monocortical pedicle screws, it was found that the maximum loading values in Th10, Th11, L2, and L3 vertebral bodies were 3.4, 2.0, 3.5, and 8.6 MPa, respectively; loading on pedicle screws installed in the indicated vertebrae was 48.4, 48.3, 23.3 and 43.5 MPa. When using bicortical screws without crosslinks in the vertebral bodies, the values were 3.1, 2.5, 3.8, 9.6 MPa and 49.9, 51.9, 25.8, 44.8 MPa, respectively; when using a combination of short screws and crosslinks in the vertebral bodies, the values were 3.2, 2.0, 2.6, 7.5 MPa and 47.6, 47.5, 22.6, 41.2 MPa, respectively; when using crosslinks and bicortical screws, the values were 3.0, 2.2, 2.7, 8.8 MPa and 48.3, 49.6, 24.3, 42.5 MPa, respectively.
 Conclusions. In lateroflexion, monocortical pedicle screws cause lower critical loading rates compared to long screws at all control points of the model. Crosslinks help to reduce stress levels. The use of monocortical pedicle screws in combination with transverse ties seems to be the most biomechanically effective in lateroflexion.

Evaluation of Mechanical Characteristics of High-Strength Reinforced Concrete Columns with Hexagonal Chicken Wire Mesh Under Cyclic Loading

Recently, new materials and methods have been implemented to improve the performance of reinforced concrete columns. This paper studies experimentally the behavior of reinforced high-strength columns, with additional internal confinement using hexagonal chicken wire mesh (HCWM) to enhance ductility, energy absorption, and ultimate strength and reduce the brittleness of traditional columns. Eight double-ended one-third-scale columns with different volumetric ratios of transverse rebar have been constructed and loaded under the uniform axial compression and lateral cyclic loads. Different volumetric ratios of transverse rebar were provided based on special, intermediate, and ordinary moment frames specifications of ACI 318–14 (named SD, ID, and OD, respectively). The specimens were confined by transverse rebars and HCWM and the results were compared with reference specimens with traditional transverse ties. Experimental findings demonstrated that HCWM specimens exhibited better performance compared to their control specimens concerning crack control efficiency, load capacity, ductility, energy dissipation, and failure modes. Implementation of HCWM increased the ultimate deformation, ductility, and energy absorption of OD specimens up to 21%, 50%, and 175%, respectively, compared to their control specimen. Confinement of the concrete columns by HCWM increased the ultimate strength of OD and ID specimens up to 15% and 22% under the cyclic load, but has a negligible effect on SD columns due to enough ratio of transverse and longitudinal rebars in SD specimens. As a result, confinement of specimens by HCWM could be regarded as a simple and effective method to improve the seismic characteristics of RC columns, particularly those members constructed with a minimal number of transverse rebars.

Compressive strength of high strength concrete-encased composite columns with noncompact and slender steel angles

Concrete-encased steel angle (CEA) column is an encased composite column where structural angles are used for longitudinal and transverse reinforcements. In this study, the compressive behavior of CEA columns was investigated, focusing on the use of high-strength concrete and noncompact and slender steel angles. Ten CEA column specimens (concrete strength fc' = 33 and 66 MPa and steel yield strength Fy = 454–552 MPa) were tested under compressive loading. The section classification of steel angles and the spacing of transverse ties were considered as test variables. The tests showed that the cover concrete spalled off at peak loads and local buckling occurred in steel angles. Due to the use of high-strength concrete, the compressive strength (i.e., peak loads) was increased but the post-peak degradation behavior became steeper. The peak and residual strengths of CEA columns were examined focusing on the effects of cover failure, confinement by transverse ties, and local buckling of steel angles. Based on the results, empirical equations to estimate the peak and residual strengths were proposed and the validity was assessed by comparisons with the test results.

Prediction of axial compression behavior of rectangular RCFST columns with confining ties

A numerical investigation has been conducted to predict the peak axial strength, post-peak behavior and confined stress-strain characteristics of reinforced concrete-filled steel tubular (RCFST) columns of rectangular cross-sections under axial compression loading. Finite element analyses are carried out using a computer software ABAQUS to evaluate the axial behavior of RCFST columns. A parametric study has been conducted on rectangular RCFST columns for width-to-depth (aspect) ratios varying between 1 and 2, tube slenderness ratio ranging between 10 and 266), percentage of longitudinal reinforcement varying between 0.87 and 6.21%, five different arrangements of internal ties and volumetric ratios of ties ranging from 0.13 to 3.19%. It is observed that the RCFST columns, even with a slender tube section, showed a significant increase in strength and ductility when effectively confined with internal transverse ties. The results obtained from the numerical study are compared with the analytical confinement models and the design equations of building codes. Based on this study, suitable modifications are proposed for existing design equations to consider the effect of confining reinforcements.

Flexural tests of concrete-encased composite girders with high-strength steel angle

This study investigated the flexural behavior of concrete-encased steel angle girders (PSRC girders). Inside the concrete section, high-strength steel angles (Fy = 605 MPa) with unequal legs were used as longitudinal reinforcement, and diagonal and vertical members were bolt-connected to the longitudinal angles as transverse ties. Flexural tests were performed for three PSRC girder specimens with different reinforcement details. The tests showed that the PSRC girders all developed the peak loads exceeding the nominal strengths; however, the ductility was limited as rupture occurred near bolt holes in the longitudinal angles. Overall, the concrete damage and cracking of the PSRC girders were comparable to those in conventional reinforced concrete beams, and cover spalling and bond deterioration along the longitudinal angles were not severe. The strength, stiffness, and ductility estimated in accordance with current design codes were compared with the test results. Given the investigation results, the application and design considerations of PSRC girders were discussed.

Experimental study on local bond failure of tension reinforcing bars embedded in concrete

AbstractIn this study, to evaluate the strength on the local bond failure, pull‐out tests of deformed bars straightly embedded in concrete were conducted. As a result, the test results were classified into entire bond failure and local bond failure. The effects of the beam width and inner transverse ties on the entire bond failure were evaluated by the previous bond capacity formula. In this study, split modes in which more than one bar split the concrete for the upper or lateral side were assumed, and a method to evaluate the strengths on the local bond failure and a way to expect the split mode was proposed.

Ensuring the reliability of the results of computer modeling of the behavior of bridge structures

It is noted that structural mechanics is developing in the direction of improving design schemes, allowing more correctly assess the stress-strain state of structures. One of the topical areas of improvement is the consideration of nonlinear behavior and spatial work of structures. Constructive and genetic nonlinearities are added to the geometric and physical. Attention is drawn to the problem of checking the correctness of design decisions, which are not always based on existing standards, but are justified by calculations of more correct, but also more complex calculation schemes, performed using powerful software systems. To solve this problem, the Glavgosexpertiza recommended making calculations for at least two certified, independently developed and tested in practice software systems, and conducting a comparative analysis of the results. The question that arose about which software systems to use, it is proposed to solve with the help of MIDAS/CIVIL (South Korea) and SOFISTIK (Germany) complexes that have proven themselves quite well in bridge organizations. The article provides a comparative analysis of the MIDAS/CIVIL and SOFISTIK software packages using the spatial calculation of a bridge structure as an example, and the results are also compared with the calculation using the standard methodology. For analysis, the span structure of the railway bridge was adopted, consisting of two main split trusses with a bottom ride, reinforced with longitudinal and transverse beams in the level of movement of the railway load, longitudinal and transverse ties combining the upper and lower truss belts. The main trusses of the diagonal system are reinforced with vertical struts and suspensions. In general, analysis of the calculation results shows that both software systems give fairly close values of the calculated values of forces and stresses, and the differences for individual elements do not exceed 13.90 %. The normative calculation method provides mainly overestimated in comparison with SOFISTIK PC results, and the excess can reach 53.73 % for longitudinal forces and 49.71 % for normal stresses. This difference is a consequence of the use of a flat design scheme in the regulatory methodology, which leads to an increase in the level of the acting longitudinal forces, transverse forces and bending moments. That is, the normative calculation for a number of elements of a bridge structure is, as it were, a margin of safety. In conclusion, the requirements are formulated for specialists involved in the calculation analysis and examination of project documentation.

Testing of a Full-Scale Composite Floor Plate

Abstract A full-scale composite floor plate was tested to investigate the flexural behavior and in-plane effects of the floor slab in a grillage of composite beams that reduces the tendency for longitudinal splitting of the concrete slab along the line of the primary beams. This is important in cases where the steel decking is discontinuous when it is orientated parallel to the beams. In this case, it is important to demonstrate that the amount of transverse reinforcement required to transfer local forces from the shear connectors can be reduced relative to the requirements of Eurocode 4. The mechanism under study involved in-plane compression forces being developed in the slab due to the restraining action of the floor plate, which was held in position by the peripheral composite beams; while the secondary beams acted as transverse ties to resist the forces in the floor plate that would otherwise lead to splitting of the slab along the line of the primary beams. The tendency for cracking along the center line of the primary beam and at the peripheral beams was closely monitored. This is the first large floor plate test that has been carried out under laboratory conditions since the Cardington tests in the early 1990s, although those tests were not carried out to failure. This floor plate test was designed so that the longitudinal force transferred by the primary beams was relatively high (i.e., it was designed for full shear connection), but the transverse reinforcement was taken as the minimum of 0.2% of the concrete area. The test confirmed that the primary beams reached their plastic bending resistance despite the discontinuous decking and transverse reinforcement at the minimum percentage given in Eurocode 4. Based on this test, a reduction factor due to shear connectors at edge beams without U-bars is proposed.

Concrete Cover Influence on Inelastic Buckling of Longitudinal Reinforcing Bars

The paper presents the results of numerical analyses of post yielding behaviour of compressed reinforcing bars, taking into account the impact of concrete cover on static equilibrium path. Concrete cover was modelled as a transverse ties with characteristics like for the tensioned concrete. The calculations were performed for various parameters of concrete cover and bar slenderness, with the use commercial system Abaqus/CAE. The results of analysis showed that the concrete cover has a significant impact on inelastic buckling of reinforcing bars.

Cyclic stress-strain model incorporating buckling effect for steel reinforcing bars embedded in FRP-confined concrete

Buckling of steel reinforcement usually causes a sudden loss of the load-carrying capacity and the ultimate state of conventional reinforced concrete (RC) cylinders. However, reinforcing bars behave differently in fiber-reinforced polymer (FRP)-confined RC cylinders due to the lateral confinement effect of FRP. This paper presents a theoretical study into the buckling behavior of longitudinal steel reinforcing bars embedded in FRP-confined concrete subjected to cyclic axial compression. An empirical monotonic compressive stress-strain model considering the buckling effects proposed previously for laterally supported reinforcing bars is extended to a cyclic model by combining the monotonic envelope and the Menegotto-Pinto model accounting for the cyclic loops. The cyclic stress-strain models for both laterally supported reinforcing bars and FRP-confined plain concrete are then implemented into the OpenSees software platform and validated through comparisons with compressive test results on cyclically loaded FRP-confined plain and RC cylinders. The proposed cyclic stress-strain model for laterally supported reinforcing bars is expected to serve as a fundamental model for predicting the seismic behavior of FRP-strengthened RC cylinders with widely-spaced transverse ties under cyclic axial compression, in which case the local buckling of reinforcing bars usually occurs between two adjacent transverse ties.

Experimental and analytical performance evaluation of steel beam to concrete-encased composite column with unsymmetrical steel section joints

The seismic performance of steel beam to concrete-encased composite column with unsymmetrical steel section joints is investigated and reported within this paper. Experimental and analytical evaluation were conducted on a total of 8 specimens with T-shaped and L-shaped steel section under lateral cyclic loading and axial compression. The test parameters included concrete strength, stirrup ratio and axial compression ratio. The response of the specimens was presented in terms of their hysterisis loop behavior, stress distribution, joint shear strength, and performance degradation. The experiment indicated good structural behavior and good seismic performance. In addition, a three-dimensional nonlinear finite-element analysis simulating was conducted to simulate their seismic behaviors. The finite-element analysis incorporated both bond-slip relationship and crack interface interaction between steel and concrete. The results were also compared with the test data, and the analytical prediction of joint shear strength was satisfactory for both joints with T-shaped and L-shaped steel section columns. The steel beam to concrete-encased composite column with unsymmetrical steel section joints can develop stable hysteretic response and large energy absorption capacity by providing enough stirrups and decreased spacing of transverse ties in column.

Analytical study of in-plane buckling of longitudinal bars in reinforced concrete columns under extreme earthquake loading

Seven full-scale reinforced concrete (RC) columns were tested at the Multi-Axial Subassemblage Testing (MAST) Laboratory of the University of Minnesota to investigate their performance under extreme seismic events. The specimens were designed according to seismic provisions of ACI 318-11 (ACI Committee 318, 2011) and incorporated closely-spaced transverse hoops at their base. However, at large drift ratios during these tests, longitudinal bars were observed to buckle parallel to the face of the columns with transverse ties having little effect. This previously unobserved bar buckling phenomenon is investigated numerically to gain a better understanding of the column characteristics that affect it. First, a bar-spring mechanical model is used to understand the conditions needed to prevent buckling of longitudinal bars by means of restraints with finite stiffness. Second, a three-dimensional (3D) nonlinear finite element analysis of the lower portion of the specimen subjected to monotonic loading was formulated in ABAQUS and validated with test data. The analysis reveals that columns with larger cross-sectional dimensions that incorporate larger longitudinal bar sizes (No. 8 and above) and lower strength concrete are more prone to in-plane bar buckling.

Evaluation of Transverse Tie Rods in a 50-Year-Old Adjacent Prestressed Concrete Box Beam Bridge

AbstractAdjacent prestressed concrete box beam bridges are one of the most popular bridges in the United States for short to medium spans. Recently, there has been concern about the structural capacity of these bridges as they age and show signs of deterioration. Unfortunately, limited research has been performed on the transverse ties because they are typically used for pulling the adjacent beam together during construction. Therefore, they are typically neglected in the overall performance of the bridge. Little, if any, information is known of the behavior and contribution of the transverse ties to load transfer and the ultimate capacity after failure of the longitudinal shear key joints. Instrumenting installed transverse tie rods has not been done in the past due to difficultly in accessing the rods, and no technique has been established to perform the installation of a sensor in the tie rods. In addition, instrumenting a tie rod that has already been installed from the fascia beam would only allow th...

The Strain Change Rules of Full-Scale High Strength Concrete Frame Columns with High Axial Compression Rations

Based on experimental study of 9 full-scale high-strength concrete(HSC) rectangular frame columns with high axial compression ratios, high-strength longitudinal reinforcements and transverse reinforcements and rectangular interlocking ties, their strain change rules of longitudinal reinforcement, stirrups and concrete were discussed and analyzed. The main results indicate as follows. The maximum tensile strain of longitudinal reinforcement decrease and the tensile strain of concrete increase quickly as the axial compression ratios and the strength grades of concrete are higher; the strains of outer stirrups are all the time greater than those of inner stirrups; the single brace stirrups have the same action with the closed stirrups.

Review of Transverse Reinforcement Requirements for Precast Load-Bearing Wall Panels with Large Openings under Compression

AbstractPrecast concrete load-bearing wall panels have been used for decades with unparalleled success due to their architectural versatility, thermal insulation, ease of production and erection, and structural performance. According to the current building code, structural walls do not need transverse ties if the vertical reinforcement ratio is less than 1% or when vertical reinforcement is not required as compression reinforcement. Also, minimum reinforcement requirements do not apply to structural walls with an average effective prestress of 1,551 kPa (225 psi) or greater. Elimination of transverse ties in structural precast walls simplifies the production of the panels. The presence of large openings in precast walls is very common in the design of modern buildings. This results in a significant reduction of the panel cross section. Most designers tend to design the remaining portion of the panel cross section as a column and not a wall, which requires minimum transverse ties according to the current ...

Adjacent precast concrete box-beam bridges: State of the practice

This paper provides information about the current practice for the design, construction, maintenance, repair, and inspection of adjacent precast concrete box-beam bridges. These bridges provide a popular and economical solution in many states because they can be constructed rapidly and deck forming is eliminated. The bridges may be single or multiple spans. The box beams are generally connected by grout placed in a keyway between each unit and usually with transverse ties. Partial- or full-depth keyways are typically used, incorporating grouts using various mixture proportions. Transverse ties, grouted or ungrouted, vary from a limited number of nontensioned threaded rods to several high-strength tendons, posttensioned in multiple stages. In some cases, no topping is applied to the structure, while a noncomposite topping or a composite structural slab is added in other cases. Most shear-key details currently used are regional standard details of uncertain origin. This information was gathered from a survey of state highway agencies through the AASHTO Highway Subcommittee on Bridges and Structures and a review of the AASHTO LRFD Bridge Design Specifications.

Modeling of Direct Load Transmission in Lightweight-Concrete-Core Sandwich Beams

The direct load transmission behavior of hybrid sandwich beams consisting of a bottom fiber-reinforced polymer skin and a top concrete skin was investigated experimentally. The sandwich core consisted of lightweight concretes of different brittleness (sand lightweight aggregate concrete [SLWAC] and all lightweight aggregate concrete [ALWAC] mixtures). Cracking and ultimate load prediction using classical strut-and-tie models was inaccurate because these models do not take differences in material brittleness into account. A continuous direct load transmission model is proposed that consists of a diagonal bottle-shaped strut with an infinite number of transverse ties. The statically indeterminate system allows stress redistribution resulting from post-peak material softening after concrete cracking to be taken into account. This led to accurate modeling of the varying experimental responses due to different material brittleness. The arch rise of the bowed compression strut decreased after cracking due to the available width of the diagonal strut being reduced to the distance between initiating and propagating cracks parallel to the strut. The arch rise, furthermore, decreased with increasing material brittleness. © 2009, American Concrete Institute. All rights reserved.

Bearing Strength of Hybrid Coupled Shear Wall Connections

Due to lack of information, current design methods to calculate bearing strength of connections are tacit about cases in which hybrid coupled walls have connection details of stud bolts and horizontal ties. In this study, analytical study was carried out to develop model for calculating the connections strength of embedded steel section. The bearing stress at failure in the concrete below the embedded steel coupling beam section is related to the concrete compressive strength and the ratio of the width of the embedded steel coupling beam section to the thickness of the shear walls. Experiments were carried out to determine the factors influencing the bearing strength of the connection between steel coupling beam and reinforced concrete shear wall. The test variables included the reinforcement details that confer a ductile behavior in connection between steel coupling beam and shear wall, i. e., the auxiliary stud bolts attached to the steel beam flanges and the transverse ties at the top and the bottom steel beam flanges. In addition, additional test were conducted to verify the strength equations of the connection between steel coupling beam and reinforced concrete shear wall. The results of the proposed equations in this study are in good agreement with both our test results and other test data from the literature.