Splice Length Research Articles

Design conditions in the middle range for implementation of integrated ring resonators in LiNbO 3 by direct laser writing

The aim of this work is to design an integrated optical ring resonator to be implemented in LiNbO3 with a 2.5 mm radius and an operating wavelength of 1550 nm. Considering these ring parameters, a free spectral range of 71.54 pm and a quality factor of ∼ 5 × 10 5 were calculated. The authors apply results to improve the implementation of femtosecond laser writing in lithium niobate crystals. As it is well-known finite difference time domain method requires large memory and time for processing circuits with large footprint (few square mm), in contrast, the beam propagation method allows to simulate large bends in a simple way. RSoft suite design tools commonly represent circles by closed polygons whose geometrical parameters are not optimised to obtain bending losses as least as possible, as suggested by coherent coupling theory. In this sense, the suitable determination of a splice angle (in this case 1.44 ° ), shape and length for segments are key parameters in the ring design. For this purpose, an ad hoc software was implemented to overcome this drawback. In summary, a 250 sided polygon side showed a suitable coupling performance and established a new layout approach for middle range rings.

On lap splice length of lap-spliced crossties for reinforced concrete columns under cyclic loading

A lap-spliced crosstie comprises two J-shaped rebars, each with a 180° hook at one end and straight at the other end. Six large reinforced concrete columns subjected to lateral cyclic loading were tested. The results indicated the following: (1) the confining effect of horizontally lap-spliced crossties is similar to that of vertically lap-spliced crossties. (2) Splice length of the lap-spliced crossties that is smaller than the code requirement can also provide sufficient concrete confinement. (3) A method for determining required lap splice length for lap-spliced crossties is proposed. (4) The lap-spliced crosstie can considerably improve the constructability of the crossties. Furthermore, the construction quality of reinforced concrete column reinforcement and the seismic resistance capability of reinforced concrete structures can be significantly upgraded.

Performance of Tension Lap Splice in Lightweight Concrete

The use of Light-Weight Concrete (LWC) in modern construction has resulted in efficient designs and considerable cost savings by reducing structural own weight and supporting footings sections. The purpose of this paper is to investigate the Lap-Splice behavior between LWC and steel reinforcement (RFT). The tested specimens were divided into four groups to study the effect of main variables: steel reinforcement bar size, internal confinement (stirrups), splice length and concrete cover thickness. Four-point bending tests were carried out on test specimens to evaluate the performance of lap splices under pure bending. Bond behavior and failure modes were noted to be similar in the normal concrete and in the LWC. In tested beams, it was observed that the bar size has a significant influence on the mean bond stress in the splice. Improving radial tensile strength by using increasing stirrups number improves the bond behavior. The splice length up to 35 times bar diameter decreased the moment capacity of beam. The splice length of 55 times bar diameter results in the same capacity of the beam without any splice.

Lap splices in steel fiber-reinforced reactive powder concrete beams under dynamic loading

Reactive powder concrete is a new cement-based composite with ultra-high strength and performance that has been recently used in many structural elements. This study is focused on studying the effect of lap splices in reinforcing bars on the behavior, strength and deflection of steel fiber-reinforced reactive powder concrete beams under dynamic-harmonic loading. The models were simulated using finite elements approach by ANSYS software with different parameters such as compressive strength of concrete, lap splices length of reinforcing bars, steel fiber percentage and the presence of stirrups in the lap splices zone. Data from experimental test by others were adopted as input data such as loading and mechanical properties of concrete and reinforcements. Total eight beam models were analyzed and two of them were compared with the experimental tests. The analysis results indicate that the criteria based on the ACI code for lap splices is enough in the case of splices in reinforced concrete beam under the effects of harmonic loadings under low and medium frequency ranges, and showed that the increase in lap splice length under the effect of harmonic loading resulted in a decrease in the deflection of beams, especially in case of medium frequency.

Extended Tension Chord Model for Boundary Elements of RC Walls Accounting for Anchorage Slip and Lap Splices Presence

This paper presents a mechanical model for the simulation of reinforced concrete (RC) wall boundary elements with lap splices, which builds on the tension chord model. The model is composed of an assembly of components, each one accounting for a different source of deformation. Namely: (i) an anchorage-slip element accounting for the strain penetration of the longitudinal reinforcement into the foundation; (ii) a basic tension chord element evaluating the response outside the lap splice zone; and (iii) a lap splice element describing the behaviour within the lap splice region. For an imposed global displacement, the model provides the steel and concrete stress and strain distributions, the crack distribution and opening, as well as the global resisting axial force. For spliced members, the ultimate displacement is computed through a semi-empirical relationship providing the average lap splice strain at failure. Validation is carried out against a series of uniaxial cyclic tests on RC wall boundary elements featuring both continuous and spliced reinforcement; different lap splice lengths and confining reinforcement are considered. Overall, a good match is obtained between numerical and experimental results in terms of crack width, rebar strain distribution along the splices and ultimate displacement.

Analytical investigation in bond of deformed steel bars in recycled aggregate concrete

Theoretical analysis of bond in RAC has been carried out using the thick-cylinder analogy and the calculated results are compared with the experimental results from the unconfined 132 splice beam specimens tested under four-point bending. The parameters for this investigation were: grades of concrete (normal-, medium- and high-strength), recycled concrete aggregate (RCA) replacement levels (0%, 50% and 100%), rebar diameter (12 mm and 20 mm), splice lengths, ratio of concrete cover to rebar diameter and surface rib characteristics. Similar behavior in bond has been observed in the concrete made with natural aggregates and the concrete obtained by selected levels of RCA replacements which means that the same mechanism was at play in both the types of concrete. A comparison of the obtained experimental results has been carried out by the theoretical models.

An Evaluation of Lap Splice Length of Epoxy Coated Reinforcements Using Beam-End Test

An Evaluation of Lap Splice Length of Epoxy Coated Reinforcements Using Beam-End Test

Performance of non-contact lap splices in geometrically dissimilar bridge column to drilled shaft connections

It is often required to provide a reinforcing steel splicing arrangement with non-contact lap splices due to the limitation of internal space or geometric irregularity for the connection of non-circular bridge columns interfacing directly with circular drilled shafts. But there are concerns regarding the safety and cost-effectiveness of such non-contact lap splices at bridge column to drilled shaft connections because the guidelines in AASHTO LRFD Bridge Design Specifications (2017) and studies on this type of connection are limited. This paper presents an experimental investigation of non-contact lap splices in non-circular bridge column to circular drilled shaft connections. A total of seven large-scale column-drilled shaft specimens were tested to investigate the effects of the critical parameters affecting the performance of such non-contact lap splices. The investigated parameters were the non-contact splice distance between the spliced bars, the lap splice length and the amount of transverse reinforcement in the non-contact lap splice zone. The specimens were subjected to flexure action with both monotonic and cyclic loading. The results of this study provide a basic understanding of the behavior of non-contact lap splices in non-circular columns to circular drilled shaft connections. Based on the findings from the experimental investigation, a set of design recommendations is provided for the design of non-contact lap splices in geometrically dissimilar bridge column to drilled shaft connections. All in all, with the consideration of the current AASHTO LRFD code and the design recommendations from this study, a safe non-circular column to circular drilled shaft connection can be constructed.

Cyclic test on a precast reinforced concrete column-to-foundation grouted duct connection

A full-scale specimen of a column-to-foundation grouted duct connection suited for buildings and industrial structures is tested in cyclic bending combined with axial compression. The positioning of the steel ducts along the sides of the column cross-section allows for using traditional reinforcement cages for the column, with longitudinal bars at both mid-side and corners of the cross-section. Splice length and amount of transverse reinforcement along the splice are defined based on Eurocode 2 provisions for laps of reinforcing bars. A total of 19 loading cycles are carried out, achieving a drift of 5.3% in correspondence of a degradation of 15% of the peak resistance. The shear slip measured at the column-foundation interface results to be smaller than 5% of the deflection. Conversely, to predict accurately the test results, the slip of the projecting bars within their ducts cannot be neglected. It is proposed to take account of this slip by introducing an apparent strain. For the tested specimen, the apparent strain turns out to be equal to the yield strain of the reinforcement. A comparison with a monotonic bending test, previously conducted on the same connection, shows a strongly smaller deformability when the loading protocol is cyclic. Hysteretic energy and drift ductility for the proposed connection are close to those concerning a cast-in-place specimen of comparable capacity, which was described in a recent paper. The test results show an over-strength of 1.4 and a gain in ductility of 1.8 compared with the design values of bending resistance and curvature ductility computed for the cross-section at the column-foundation interface.

Behavior and Splice Length of Deformed Bars Lapping in Spirally Confined Grout-Filled Corrugated Duct

This paper discusses the behavior of grouted noncontact lap splices under monotonic tension load. Deformed bars lapped through a grout-filled corrugated duct, and a spiral reinforcement was preembedded in the connection to improve tensile strength of the splice. The experimental results show that bond failure splices are always failed by the pullout of the preembedded bar other than the grouted bar. As the spiral pitch distance is not greater than 75 mm, the tensile strength generally improves with the increment of volumetric spiral reinforcement ratio due to the higher confinement provided by the spiral bar. Compared with the spiral bar diameter, the spiral pitch distance provides more dominant effect on the tensile strength of the connection. Based on the experimental results and the development length specified in ACI 318-14, a revised equation with a reduction factor of 0.76 was proposed to predict the required minimum lap length of spirally confined lap splice.

Output error of converse piezoelectric fiber voltage sensor caused by optical fiber factors

In fiber voltage sensor, imperfect fiber splicing angle and length difference between the sensing fiber and the compensating fiber usually influence the system output performance. This article established the mathematical model of the system output error using the Jones matrix and analyzed the relationship between the system output error and the above two error factors, respectively. The results show that the angle error of 90° splice has a significant influence on the system output, and the tolerance of angle error varies with different test voltages. When the test voltage is higher than 6 kV, if the expected system error is less than 0.02%, the splicing angle error should be less than 0.15°. Additionally, the length difference also has a significant influence on the system output accuracy. The length difference between sensing fiber and compensating fiber should be less than 1 µm when the test voltage is 110 kV so that the system can meet the accuracy requirements of IEC 0.2s. This research provides a reference for the development of fiber voltage sensor based on the converse piezoelectric effect and also provides a basis for the design of intelligent power detection robot system.

Compression Splices of Reinforcing Bars in Reactive Powder Concrete

Compression splices are widely used in compression members such as columns in multi- story buildings. There are efficient design equations for compression splice of reinforcement embedded in conventional concrete proposed by design codes of practice. However, there is no design equation for compression splice in compression members made of reactive powder concrete (RPC). So, it is required to introduce a design equation to calculate the steel bars lap splice length of RPC compression members. In this study, an experimental work was conducted to investigate the effect of different variables on compression splices strength. These variables were compressive strength of concrete, transverse reinforcement amount, splice length, yield stress of reinforcement and spliced rebar diameter. The experimental results showed that; Increase in the yield stress of reinforcing bars, length of spliced bars and compressive strength of concrete result in increasing in splice strength. Meanwhile, increase in diameter of reinforcing bars result in decreasing in compression splice strength. The increase in the amount of transverse reinforcement has insignificant effect on compression spliced strength of rebar. Finite element analysis was used to analyze the tested specimens and compared between numerical and experimental result was carried out. The numerical and experimental ultimate load and load-deflection behavior is very close to each other. Finite element method was used to investigate a wide range of experimental variables values through a parametric analysis. A new proposing equation for compression splicing of rebar in RPC column is presented in this research.

Seismic behaviour of RC columns with welded rebars or mechanical splices of reinforcement

The extension of existing RC buildings is a challenging process, which requires efficient connection between existing and new materials to guarantee load transferring between the lap-spliced longitudinal columns\' reinforcement. Therefore, the length of the columns\' starter bars is a crucial factor, which decisively affects the seismic response of the new columns. In particular, when the length of the starter bars is short, then the length of the lap splices of reinforcement is inadequate to ensure load transfer between steel bars and concrete, with an indisputable detrimental impact on the seismic behaviour of the columns. Moreover, in most of the existing RC buildings the column starter bars are of particularly short length, while they have probably been bent, cut or corroded. In the present study, the effectiveness of both welded rebar and mechanical splices of reinforcement in ensuring load transferring between the starter bars and the longitudinal reinforcement of the new column was experimentally evaluated. Four cantilever column subassemblages were constructed and subjected to earthquaketype loading. Three of the specimens were used to examine different types of shielded metal arc welding (SMAW), while in the fourth subassemblage mechanical splices were tested. The hysteretic response of the columns was evaluated and compared to the behaviour of a fifth specimen with continuous reinforcement, tested by Kalogeropoulos and Tsonos (2019). Test results clearly demonstrated that the examined types of SMAW were equally satisfactory in ensuring the ductile seismic performance of the columns, while the mechanical splices found to be more susceptible to exhibit slipping of the bars.

Prediction of bond performance of tension lap splices using artificial neural networks

Recently, machine learning has been widely used in civil engineering, because better design can be achieved using the advanced computer intelligence and test results. In the present study, to improve design reliability and to extend design application range for the development and lap splice lengths, an artificial neural network model (ANN) was presented using 1008 existing experimental studies for splice tests. Although some of the test parameters are out of the limitations of design codes, all test results were used for the ANN to extend design application range considering present-day construction materials and practices. From a parametric study with the ANN, the effect of design variables was investigated, and predictions by the ANN were compared with existing design equations. Finally, based on the parametric study result, modifications were proposed for existing design equations to consider the effect of non-uniform bond stress distribution and the effect of cover concrete and transverse bars, as well as to extend design application range. Comparisons showed that the modifications improved the accuracy of the design methods. The high accuracy to the large number of existing test results confirms that the modifications based on the ANN can improve design reliability and also can extend design application range for the development and lap splice lengths.

Variation of Splice Length with Bending Behavior of Reinforced Concrete Beams

The splice length of the distribution depends on the concrete stress with reinforcement, generally the bond stress is tested by pull out testing where pull out testing can provide a good comparison between the efficiency of the attachment of various types of reinforcement surfaces. However, the bending behavior of the beam is very different from the pure tensile pull out test. This study presents the effects of variations of lap splice (30db, and 40db) in the area of beam pull. The first test object was a beam BN - 0 (non splice length) which was a normal beam. The second test object was a beam BN - 30db with the splices length(ld) of 480 mm and the third test object was a 40db beam with the splice length (ld) of 640 mm. The test used a pure bending test method with loading of Two Point Loads on a simple support beam. The results gained from this study obtained flexural capacity in BN-0 (non lap splices) of 115.15 kN, flexural capacity of BN - 30db of 90.484 kN, and beam flexural capacity of BN-40db of 124.848 kN. The displacement ductility at BN-30db decreased 35% to BN-0 and displacement ductility at BN-40db increased 48% to BN-0, the bond strength attached to BN-40db increased 2.92% to BN-30db. The splice length (ld) 40db was able to develop the ability to achieve yield stress loads and the spread of crack concentration around the joints.

Experimental investigation on the deformation capacity of lap splices under cyclic loading

Correct detailing and positioning of lap splices is essential in order to prevent premature failure of reinforced concrete structural members. Especially before the introduction of capacity design guidelines, lap splices were often placed in member regions that undergo inelastic deformations under earthquake loading. When assessing the seismic performance of such members, not only the lap splice strength, which was assessed in previous studies, but also information on the deformation capacity of lap splices is required. This paper analyses the results of a recently concluded experimental programme on spliced RC wall boundary elements tested under uniaxial tension–compression cyclic loading. The study aimed at investigating the influence of lap splice length, confining reinforcement and loading history on the deformation capacity of lap splices. The latter is defined as the average strain, at the onset of splice failure, ascribed to deformations originating from the lap splice zone. Analysis of the test results showed that the deformation capacity of lap splices: (1) increases with lap splice length; (2) increases with confining reinforcement but the effectiveness of the confining reinforcement is dependent on the lap splice length; (3) decreases with larger imposed compression levels; (4) is larger for bottom-casted with respect to top-casted lap splices. Finally, an empirical model is proposed to estimate the strain capacity of lap splices, which provides a good fit with the experimental results.

Effectiveness of Various Techniques Using FRP for the Strengthening of R. C. Beams with Tension Lap Splices

This paper presents an experimental program conducted to investigate the flexural performance of RC beams with tension reinforcement lap splice strengthened using externally bonded FRP different techniques in splice region. The specimens were reinforced on the tension side with four deformed bars spliced at mid span. The tested beams are of 3200 mm total length and 250*120 mm cross section, tested in positive bending. The considered parameters were splice length, type of FRP (glass or carbon), strengthening techniques in splice region (externally confine strips around cross section, Near Surface Mounted technique "NSM" stirrups, externally bonded sheets or bars on the tension face, number of GFRP strips layers (one layer, two layers, and three layers), and shape of NSM stirrups (Box or U shape). No additional anchorage mechanism or bonding methodology was applied for the FRP strips on the concrete except the epoxy adhesive. The effect of these factors on the failure of modes, the ultimate load, the bond strength and that the ductility were investigated. The results indicated that all applied strengthening techniques were efficient in improving the bond strength of the lap splices, the ductility, and the load-deflection behavior of the tested beams, especially when strips were installed over the splice region. This study approved that NSM technique gave more prominent simplicity of employ.

Polymer Concrete for Bridge Deck Closure Joints in Accelerated Bridge Construction

Prefabricated concrete bridge deck panels are utilized in Accelerated Bridge Construction (ABC) to simplify bridge deck construction. Concrete with good bond and shear strength as well as excellent flowability is required to fill bridge deck closure joints. This paper discusses the use of polymer concrete (PC) for bridge deck closure joints in ABC. PC produced using poly methyl methacrylate and standard aggregate was tested. Test results of PC are compared to Ultra-High Performance Concrete (UHPC). Development length, lap splice length and shear strength of unreinforced PC were tested. It is shown that PC has a development length of 3.6 to 4.1 times the reinforcing bar diameter that is close to one-half the development length of 6 to 8 times the bar diameter required with UHPC. PC also showed a shorter splice length compared with that reported for UHPC. Finally, unreinforced PC showed shear strength that is twice that of UHPC. It is evident that using PC in bridge deck closure joints in ABC can improve constructability and provide cost-savings and eliminate reinforcing bar congestion.

Tensile Behaviors of Lap-Spliced Carbon Fiber-Textile Reinforced Mortar Composites Exposed to High Temperature

The tensile behaviors of textile-reinforced mortar (TRM) composites made with carbon fiber textile and alumina cement-based mortar were investigated through direct tensile tests. Three different surface treatment details in the lap splice area were used to improve the tensile behaviors of the TRM composites: carbon fiber textile impregnated by epoxy, carbon fiber textile coated with aluminum oxide powder following epoxy impregnation, and carbon fiber textile coated with aluminum oxide powder following both carbon fiber fabric attachment and epoxy impregnation. Three different lap splice lengths were used 180, 200, and 220 mm. In addition, the tensile properties of TRM composites following exposure to high temperature were investigated as well. In this test, TRM test specimens were exposed to two different temperature histories with maximum values of 250 and 350 °C. The results of the test specimens according to the test parameters were analyzed in terms of initial stiffness, cracking strength, corresponding strain at cracking, modulus of elasticity in the cracked stage, peak strength, and ultimate strain. The influence of lap splice length on the tensile behaviors of the TRM composites was analyzed and discussed. The surface treatment in the overlapping region showed ductile behavior and resulted in a significant improvement of the peak strength and ultimate strain over the untreated lap splice textile. Following exposure to high temperature, the TRM composites showed a reduction of tensile responses compared to those cured at room temperature. In addition, a prediction model developed in the previous study was used to predict the tensile behaviors of the lap-spliced carbon fiber-textile reinforced mortar composites exposed to high temperature, and the prediction by the model showed a good agreement with the experimental results.

Uniaxial Cyclic Tests on Reinforced Concrete Members with Lap Splices

This data paper presents the quasi-static uniaxial cyclic tests of 24 reinforced concrete members, of which 22 feature lap splices and 2 are reference units with continuous reinforcement. The objective of the experimental program is to investigate the influence of lap splice length ( ls), confining reinforcement, and loading history on the behavior of lap splices. Particular attention is placed on the measurement of local deformation quantities, such as lap splice strains and rebar-concrete slip. Details of the geometry and reinforcement layout of the specimens as well as the employed test setup, instrumentation, and loading protocols are provided. The global behavior of the test units, including the observed crack pattern and failure modes, are discussed. The organization of the experimental data, which are made available for public use under DOI: 10.5281/zenodo.1205887, is outlined in detail.