Ultimate Tensile Capacity Research Articles

Cyclic loading behaviors of novel RC beams with kinked rebar configuration

Lateral collapses due to earthquakes and progressive collapses due to the sudden destruction of columns are two of the most commonly encountered failure mechanisms for buildings. In a previous study, a novel kinked rebar (KB) configuration was proposed by the authors to simultaneously improve the seismic performance and the progressive collapse resistance of reinforced concrete (RC) frame structures. This configuration works because KB has a weaker initial yielding capacity and larger tensile deformability, and almost the same ultimate tensile capacity compared to ordinary steel rebar. This paper aims to provide further experimental validation and enhance the understanding of the seismic performance of RC beams with KB configurations. First, to overcome the disadvantages of the application of KB found in a previous study, the middle longitudinal bars in an RC beam were proposed to further improve the KB configuration. Second, cyclic loading tests of bare KB specimens were conducted to investigate the hysteresis equivalent stress-equivalent strain curves and failure modes of KB. Third, a cyclic loading test of RC beams with KB was performed. The test results showed that the application of KB could help relocate the plastic hinges to protect the RC column and joint, weaken the yielding loading capacity of the beams to increase the strong column-weak beam (SCWB) ratio, and increase the loading capacity of the beam again at large rotations to maintain a certain lateral load resistance at large deformation of the frame structure. An interesting “two-hinge” behavior was also found in the tests for RC beams with the KB configuration.

Experimental and analytical studies of base pipe pin connections under direct tension

Base pipe pin connections were developed to simulate a hinge behavior at the base of cast-in-place or precast bridge columns. Base pipe pins are composed of two steel pipes: one pipe is embedded in the column and the other in the adjoining member. Shear force is transferred through contact of the pipes and friction. The uplift force is resisted by a tension member and welded studs on the surface of the column pipe. To investigate the behavior and failure mode of base pipe pins under direct tension and to determine the ultimate tensile capacity of the pins, two scaled pipe pin connections were tested under direct tension. Elaborate nonlinear finite element (FE) studies of the pipe pins were also conducted to explore the effects of different parameters on the response of the pins. There are many possible failure modes that could occur under tension. Test results depicted that rupture of the pin tension member with no damage to the connection was the dominant failure mode in pure tension. The FE models accurately estimated the response of the test models and the observed failure mode. The analytical results showed that decreasing the pipe height alters the failure mode but does not affect the ultimate capacity of the connection significantly. Furthermore, reducing the pipe height or increasing the number of stud layers has a small effect on the ultimate capacity and stiffness of the connections.

Study on Tensile Properties of Composite Structure Shear Connector

In this paper, the ABAQUS dynamic display analysis method is used to realize the quasi-static analysis of the welding nail. The correctness of the finite element model is verified by comparing with the existing experiments. The finite element simulation calculated four different nail lengths hs, and the calculated simulation values were in good agreement with the experimental values. In the case of the failure mode, when the welding nail is too short and the length-to-diameter ratio of the welding nail is less than 5.92, the whole of the welding nail together with the broken concrete in the surrounding area is pulled out, and when the aspect ratio satisfies certain requirements, the welding nail is generated. Necking, the concrete slab is not broken, and the ultimate tensile bearing capacity is relatively close.

Numerical Study on Ultimate Deformation and Resistance Capacity of Bolted T-Stub Connection

Disproportionate or progressive collapse is a phenomenon in which entire structure or large part of it collapses because of the local failure of a structure. Resistance to such progressive collapse depends on continuity between elements and ductility of the connections. The ductility of commonly used bolted end plate connections may depend on the T-stub component of the connection. The aim of this paper is to study the behaviour of T-stub components of beam to column end plate bolted connections under large deformation demands associated with column loss scenario. For this purpose, a parametric study is carried out to evaluate the ultimate strength and deformation capacity considering two parameters i.e. distance between the bolts and endplate thickness. Based on the experimental data, numerical model has been validated and employed in a parametric numerical study aimed at improving the response under large deformation demands. The study indicate significant role of bolts in development of catenary forces since the ultimate tensile capacity of T-stub after undergoing large deformation in a ductile failure mode was controlled by the failure of the bolts. Parametric study reveals much higher bolt force in comparison with displacement controlled induced axial force in the T-stub indicating failure of the bolts at much lower applied axial force.

Experimental study on fatigue performance of adhesively bonded anchorage system for CFRP tendons

Abstract This study is concerned with the fatigue performance of adhesively bonded anchorage for carbon fiber reinforced polymer (CFRP) tendons subjected to cyclic loading. Series of monotonous and cyclic experiments under different stress amplitudes and loading frequencies were carried out in order to investigate the mechanical performance of bonded anchorage systems for CFRP tendons and to study the influence of cyclic loading on the anchoring performance. The fatigue damage and the relationships between damage, loading frequency and interfacial temperature rise of anchorage systems were analyzed. The results show that cyclic tension-tension loading is instrumental in enhancing the synergistic interaction between the anchorage components and it also stabilizes the entire anchorage system performance provided that the stress amplitude is kept lower than 10% of the ultimate tensile capacity of the anchorage systems and the maximum stress is less than 50% of the ultimate capacity of the anchorage system. The loading frequency influences significantly the temperature variation in the anchorage system. A high loading frequency may result in a sharp temperature rise at the early-stage and mid-stage of cyclic tension-tension loading, followed by a rather stable late stage. This phenomenon of temperature rise during fatigue tests may indicate the extent of fatigue damage in the anchorage system.

Shear lag effect on ultimate tensile capacity of high strength steel angles

This research investigates the shear lag effect on the behaviour and ultimate tensile capacity of high strength steel (HSS) tension angles with bolted and welded connections. Eighteen full-scale tests were conducted, including fourteen specimens with HSS tension angles and four specimens with normal steel (NS) tension angles. For these specimens, single tension angles were connected to the gusset plates either by bolted or welded connections. The main test parameters included steel grade, connection length and out-of-plane eccentricity. In general, the test observations showed that the shear lag effect was significant for the bolted HSS angle specimens connected by the short leg. The effectiveness of the design equation in the current design specifications for quantifying the shear lag (1−x¯/L rule, where x¯=out‐of‐plane eccentricity and L = connection length) was evaluated using the test results. The comparison of the test results and the predictions by the design equations showed that the latter gave un-conservative estimates of the ultimate tensile capacity of the specimens with bolted HSS angles connected by the short leg. Based on the finite element models validated by the test results, a parametric study was carried out, and the results also indicated that the current design equation would lead to unsafe estimates of the ultimate tensile capacities of bolted HSS angles connected by the short leg. Finally, a modified design guideline was proposed based on the results of the numerical study.

Tensile behaviour of anchored blind bolts in concrete filled square hollow sections

In this paper, the tensile behaviour of a new type of blind bolt, the anchored blind bolt, has been studied. This type of bolt consists of a conventional blind bolt with a headed stud extension that anchors it into the infill concrete. It has been developed for use in moment-resisting connections between I-beams and concrete-filled hollow section columns. The behaviour of these connections is highly dependent on the tensile behaviour of the anchored blind bolts. Hence, the fundamental mechanics of this behaviour has been studied here, both experimentally and in simulations using FE models. The complex interactions between the headed stud anchorage, the concrete infill, and the steel tube have been examined in detail. The experimental and numerical findings were used to understand the influence of important parameters in the tensile behaviour of the anchored blind bolts. It was found that the location of the bolt with respect to the side walls of the tube had a substantial influence on the behaviour of the anchored blind bolts. All the bolts located close to the side walls of the square hollow sections reached the ultimate tensile capacity of the equivalent structural bolts. This was due to the development of a concrete strut which transferred the load to the corner of the steel section. The bolt diameter also had a significant influence on the stiffness and strength of the anchored blind bolts.

Underwater Friction Stud Welding Optimal Parameter Estimation: Engineering Robust Design Based Approach

Underwater friction stud welding (FRSW) without a shroud around the stud requires controlling welding parameters to achieve optimal joint strength. A hydraulic FRSW unit has been designed and fabricated to perform FRSW without a shroud via a remotely operated underwater vehicle (ROV). An experimental study has been initiated to investigate the optimal FRSW parameter combinations and corresponding values leading to optimal ultimate tensile load capacity (UTLC) values in the welded joint. The engineering robust design (ERD) approach has been deployed to run the experiment. Each weld has been made with a S355 M12 stud on S355 structural steel plate. This paper discusses the experimental approach, results and conclusions reached in the parameter evaluation, estimation, and experimentation.

Ultimate Shear Resistance of Perfobond Rib Shear Connectors Based on a Modified Push-Out Test

This paper evaluates the ultimate shear resistance(USR) of the perfobond rib shear connector(PRSC) based on a modified push-out test and establishes a new equation for the USR. 33 modified push-out specimens were constructed and tested. The specimens had different perfobond bar diameters, perfobond rib hole diameters, concrete strengthes and transversal rebar quantities. From the test results, influencing factors of the USR such as the ultimate tensile capacity of perfobond bars, the shear stiffness of concrete dowels and the number of transversal rebar were evaluated experimentally. An new equation was developed based on regression analysis for the USR. This equation predicts the USR to within 14% of the experimental results in this test and the push-out tests for PRSC in pylon joint segments.

Influence of shear lag on ultimate tensile capacity of angles and tees

This paper presents an experimental investigation about the shear lag effects of tension steel members with welded connections. In total twenty tests were conducted, including twelve on single angles and eight on single tees. Various weld arrangements were considered as test parameters for the angle specimens which were connected by their short legs. For the tees, the influences of weld length and flange-to-web width ratio were studied. The test results showed that, the test efficiency, which is defined as the ratio of the ultimate capacity to the calculated tensile capacity of the gross section, can be increased when a balanced weld arrangement instead of an unbalanced one was employed for the angle specimens. For the tee specimens, the test efficiency was not sensitive to the weld length. In addition, increasing the flange-to-web width ratio could increase the test efficiency of the tees, although the improvement was not significant. Subsequently, design specifications for shear lag were examined, and the test-to-predicted ratios were presented. For more extensive comparisons, the ratios from an earlier investigation undertaken by the authors and co-workers and those from other researchers were also included for discussion. Finally, with the available database, reliability studies were undertaken to examine the resistance factors used in the current codes for predicting the ultimate tensile capacity of single angles and tee sections, and accordingly, new design recommendations are proposed.

Structural Performance of Grouted Sleeve Connectors with and without Transverse Reinforcement for Precast Concrete Structure

This paper presents the performance of the proposed grouted sleeve connector with and without steel spiral as transverse reinforcement under incremental tensile load until failure. The connector utilized mild steel pipe as sleeve where the sleeve consists of external and internal sleeve with the diameter of the external sleeve is larger than internal sleeve. The mild steel pipe and the steel spiral are used to confine and reinforce the grout and the two discontinued bars spliced end-to-end configuration in the sleeve. The test shows that, there are two modes of failure which were bar slipped and bar fractured outside the sleeve. Eleven specimens out of fourteen shows satisfactory results as it failed due to bar fractured outside the sleeve and achieve satisfactory ultimate tensile capacity. The stiffness and the ductility of the connectors also satisfy. Grouted sleeve connectors with steel spiral perform better compared to connectors without a steel spiral. The test shows that the performance of the grouted sleeve connector with or without steel spiral was governed by grout-bar bond, anchorage length and confinement action provided by the sleeve and the steel spiral. The connectors have a potential to be used in connecting precast concrete structure.

Mechanical Properties Test Research on Mass Concrete Mixed with Different Fly Ash Bulk Volume

The concrete would crack when the temperature stress caused by hardening concrete hydration heat and shrinkage action were over the concrete’ tensile strength. The concrete were added with different amount of fly ash in order to increase concrete’ tensile strength and ultimate tensile strain capacity or consider economic perspective. The mechanics performance tests were carried on mass concrete with different fly ash bulk volume. The test results showed that the fresh fly ash concrete’ workability, hydration heat, compressive strength and durability were obvious superior compared with ordinary concrete.

Study on Influence of Composite Ultra-Fine Fly Ash on Crack Resistance of Pavement Concrete

The crack resistance evaluation indexes of concrete were chosen, which were used to study the influence of ultra-fine fly ash on the crack resistance of pavement concrete. The concrete flat test was made to testify the concluded law. The test results show that composite ultra-fine fly ash improves the crack resistance of pavement concrete. The main reason is that it reduces the elastic modulus and drying shrinkage of concrete and improves the ultimate tensile deformation capacity.

Analysis on Metal Plate Connection Property of Larch Dimension Lumber

In this study, Larix gemilinii and metal plate were selected as the main materials. According to GB5005-2003, the connection properties of tension-splice joint and larch wood were investigated. The results showed that the elastic modulus of Larix gemilinii was not affected by the performance parameters of tension-splice joint greatly and three kinds of failure modes were introduced. Besides the design value for the ultimate bearing capacity of Larix gemilinii and the design value for the ultimate tensile bearing capacity of the metal plates were determined. A conservative calculation method for ductility ratio of metal plates was proposed. The ductility ratio of the metal plate connected joint changed with the construction modes, and the ductility ratio for metal plate parallel to the grain (more than 2.4) was obviously bigger than that of perpendicular to the grain, which complies with the requirements for ductility ratio in anti-seismic structure.

High speed tensile behavior of sisal fiber cement composites

The experimental behavior of sisal fiber reinforced cement composites subjected to high speed tension load was studied. High strain rates were achieved by using a high rate servo-hydraulic testing machine. A state-of-the-art high speed Phantom camera was also used to take images from the specimen during the test. The images were used in a digital image correlation model to determine the displacement fields and to calculate crack spacing. The effect of strain rate was investigated by comparing static and dynamic tensile tests which were performed at strain rates ranging from 5.5 × 10 −6 to 24.6 s −1, respectively. A numerical tension stiffening model based on nonlinear finite difference method was used to simulate tensile cracking behavior of sisal fiber cementitious composites. The composite presented strain rate sensitivity for ultimate tensile strength and strain capacity with a dynamic amplification factor of 1.26.

A Study on Flexural Performance of RC Beam Strengthened with UHTCC for Improved Durability

Ultra-high toughness cementitious composite (UHTCC) exhibits the pseudo-hardening feature when subjected to tensile load and has high tensile strain capacity of normally up to 3%. Also, UHTCC has a unique cracking behavior. From cracking up to ultimate tensile strain capacity, the crack width in UHTCC could be still kept below 100m. This paper presents the utilization of UHTCC to replace a layer of concrete surrounding the main flexural reinforcement in ordinary RC beam to improve flexural performance especially beam durability as UHTCC displays high toughness and shows multiple fine cracks. Analytical closed-form formulae for flexural capacity, curvature and deformation of UHTCC/RC composite beam derived based on the elastic beam theory is presented first. Subsequently, experimental results of two groups of different reinforcement ratios of UHTCC/RC beams and control RC beams tested under flexural loading to verify the feasibility of analytical formulae as well as to examine the performance improvement of UHTCC/RC composite beam over the control beam is presented. Moment-curvature curves and load-mid span displacement curves for the tested beams are compared with the theoretical analysis. A good agreement between experimental and analytical results is found. The experimental results show that the use of a layer of UHTCC in RC beams can enhance both flexural capacity and ductility. The improvement is not significant with the increase in reinforcement ratio; however, the maximum crack width under service load even in the case of lightly reinforced beams can be limited within 0.1mm.

Investigation of the strengthening effect of DFRCC applied to plain concrete beams

One of the most important characteristics of Ductile Fiber Reinforced Cementitious Composite (DFRCC) is its strain hardening behavior up to 5–6% strain under tensile loading. In this study, the strengthening effect of DFRCC, applied to the tension region of plain concrete beams, is both numerically and experimentally examined. More specifically, 10%, 20%, and 30% of the beam height are replaced with DFRCC to measure the strengthening effect of the composite beam. From four-point bending tests and numerical simulations, the load–deflection behaviors are investigated and compared. To assess the effect of ultimate tensile strength, strain capacity and strain hardening slope of DFRCC, numerical simulations are carried out with DFRCC strain capacities ranging from 1% to 5%. From these studies, it is shown that DFRCC significantly contributes to the deflection capacity, load carrying capacity and failure modes of concrete beams.

Transient vertical loading of model suction caissons in a pressure chamber

Vertical monotonic and cyclic loading tests on model suction caissons have been carried out to explore conditions relevant to the design of multiple-footing foundations for offshore wind turbines. The tests were conducted in a pressurised chamber, which simulates up to 20 m of water depth, to investigate the effect of cavitation on the ultimate tensile response of the caisson. Cyclic loading tests were also conducted at elevated pressures. Data from cyclic tests are presented to compare the response of caissons subjected to varying ambient pressures and rates of loading. The ambient pressure had little effect on the cyclic response. Faster rates of loading generated larger pressures beneath the lid of the caisson and increased the load−displacement stiffness. The ultimate tensile capacity was significantly affected by the ambient pressure and rate of loading. Implications for the design of offshore caisson foundations are discussed.

Effect of fiber reinforcement on the response of structural members

This paper describes a series of investigations on the effect of fiber reinforcement on the response of structural members in direct tension and flexure under reversed cyclic loading conditions. The design approach of the fiber reinforced cementitious composite is based on fracture mechanics principles, which will be described in the first part of the paper along with an introduction of the relevant material properties of the resulting engineered cementitious composite (ECC). This class of composites is characterized by strain hardening and multiple cracking properties in uniaxial tension and an ultimate tensile strain capacity on the order of several percent. Subsequently, the synergistic effects of composite deformation mechanisms in the ECC and structural members subjected to large shear reversals are identified. Beneficial effects observed in the reinforced ECC structural members as compared to conventional reinforced concrete include improved composite integrity, energy dissipation, ductility, and damage tolerance.

Experimental Studies on Seismic Behavior of Steel Pile-to-Pile-Cap Connections

To investigate the seismic behavior of bridge pile-to-pile-cap connections, five full-scale H-shaped steel pile-to-pile-cap connection subassemblies representing a portion of a typical bridge pile foundation were tested. Two of the full-scale subassembly specimens were subjected to a vertical cyclic load simulating axial forces in a pile caused by footing overturning during an earthquake attack. Two others were loaded with cyclic lateral force and constant vertical load. One specimen was tested under proportionally varied vertical and horizontal forces. It was found that, although it was designed as a pinned connection following the current design standard, the pile-to-pile-cap connection can sustain a significant amount of moment. Localized brittle failure was observed in the vicinity of the pile-to-pile-cap connection, as the results of unexpected moment resistance. Test results also showed that the anchorage details using two V-shape bars could not develop the full-design ultimate tensile capacity. Analytical methods are developed and found adequate to evaluate the strength of the pile-to-pile-cap connection.