Stud Anchors Research Articles

Design Recommendations for Concrete Pryout Capacity of Headed Steel Studs and Post-Installed Anchors

Current formulas to assess the shear capacity of headed steel stud anchors and post-installed (PI) anchors in case of pryout failure (sometimes known as pull-rear failure) have been derived either based on the indirect-tension resistance model or are fully empirical based on push-out test results. In both cases, the predicted pryout capacity is clearly conservative and underestimates the true pryout capacity of anchorages, especially for stiff anchors with low embedment-to-diameter ratios (hef/d < 4.5). This paper proposes an empirical and a semi-empirical formula to predict the concrete pryout capacity of headed steel studs and PI anchors. They were derived based on an improved indirect-tension model which accounts for the stud diameter and the stud spacing in a group of anchors. Furthermore, a database of 214 monotonic shear tests from the literature, including own tests (push-off and horizontally shear tests), is reevaluated and compared to the provisions of EN1992-4. The scope of this assessment proposal includes single and group of headed steel studs and PI anchors attached to a stiff steel plate as well as shear connectors in composite structures without metal deck embedded in normal-weight concrete.

EKSPERIMEN KEGAGALAN BREAKOUT CHEMICAL ANCHOR STUD METODE CAST IN PLACE DAN POST INSTALLED DENGAN MODIFIKASI LUBANG DRILL BIT EXTRACTOR

Anchors are needed to transmit the load to the concrete in strengthening the structure of a building. The anchor is installed in two ways, namely the cast in place method and the post installed method. In the post installed method, given Sika anchorfix-2 adhesive. The study was conducted to determine the type of failure that occurred, the pullout capacity of the anchor implanted on the hef 90 mm, and the average value of the adhesive strength (μ) of the M12 x 160 mm stud anchor on the T beam specimen measuring 390 x 270 x 300 mm as many as three samples. Each method of cast in place, post installed plain holes, and post installed screw holes using 32.30 MPa fc' concrete with pullout test. The results of the study, the type of failure that occurs is a breakout failure. The pulling capacity value obtained in the cast in place method is 14415.78 N, the plain hole post installed method is 77603.29 N, and the screw hole post installed method is 87377.25 N. The anchoring strength capacity of the plain hole post installed method is higher. greater than the cast in place method with an increase of 6.82%, the adhesive strength of the post installed method with threaded holes is greater than the cast in place method with an increase of 8.14%, and the adhesive strength of the post installed method of threaded holes is greater than the post installed method of holes plain with an increase of 1.24%.

An experimental and numerical investigation of concrete pry-out failure after fire exposure: Group effects and failure mechanism

In the present study, the load-bearing capacity for concrete pry-out failure of the single stud anchor and multi-stud anchor groups after fire exposure is investigated experimentally and numerically. The main topic of the investigation is the influence of fire duration on the resistance and failure mode and the group effect on the load-bearing behaviour. The standard ISO 834 fire curve was employed. The numerical simulations were conducted using the thermo-mechanical model based on the microplane constitutive model for concrete, which was implemented into a 3D finite element (FE) code. The numerical model was first verified based on the performed experimental tests. Subsequently, the parametric study was performed in order to analyse the failure mechanism and the load distribution over the studs of the anchor group. It was shown that the employed numerical modelling technique can successfully predict the pry-out failure mode and the load-bearing behaviour of anchor groups after fire exposure. The results show that the group effect on the shear stiffness of anchors is strong at ambient temperature, but moderated after fire exposure. The group effect on the pry-out failure load of anchors, both before and after fire exposure, is significant. The evaluation of the load distribution at the interfaces between anchor and concrete contributes to a better understanding of the concrete pry-out failure mechanism before and after fire exposure.

Bar versus resilient stud anchors used for immediately loaded 2 implants assisting overdentures in patients with history of periodontitis. One-year randomized controlled clinical study.

Bar versus resilient stud anchors used for immediately loaded 2 implants assisting overdentures in patients with history of periodontitis. One-year randomized controlled clinical study.

Anchorage performance of embedments in anchored prefabricated wall–beam joints of BLC–CCWS

The existing wall–beam joints of bundled lipped channel–concrete composite wall structures (BLC–CCWS) are mainly fabricated by welding thin–walled steel tubes and hot–rolled steel plates, and this application requires further improvement. An innovative anchored prefabricated wall–beam joint that does not require field welding was presented in this paper, and the anchorage performance of the embedment, which is the key force transfer component of the joint, was investigated by experimental research and theoretical analysis. The results indicated that (1) the embedments have good anchorage performance in the “bundled lipped channel–concrete” anchorage area, especially the “steel–stud–anchor plate” type of embedment, which clearly demonstrates a mechanical property evolution stage. (2) Embedment construction has a great influence on the anchorage performance. The ultimate bearing capacity, ultimate slip, ductility and energy storage/dissipation capacity of the “steel–stud–anchor plate” embedment are better than those of the “steel–stud” embedment. (3) The construction of the anchorage area has a great influence on the anchorage performance. The bundled lipped channel can substantially limit the range of damage to concrete. In addition, the anchorage performance of the embedment in the “bundled lipped channel–concrete” anchorage area is better than that of the “circumferential steel plate–concrete” anchorage area in terms of the ultimate bearing capacity, ultimate slip, ductility and energy dissipation capacity. (4) The established formula for calculating the anchorage bearing capacity of the embedment is accurate and conservative, and thus can meet the requirements of engineering practice.

Non-contact lap splice connections for steel-plate composite walls - to - reinforced concrete structures

Non-contact lap splices may be considered for connecting steel-plate composite (SC) walls to conventional reinforced concrete (RC) structures. This connection type is preferred over mechanical splice connections because of perceived construction efficiency. The primary components of the non-contact lap splice connection are the steel rebars, which are fully developed in the RC structure and extended and embedded in SC walls to transfer tensile stresses to the steel faceplates. The structural performance of a non-contact lap splice connection depends on the detailing of rebars (embedment length and location relative of stud anchors) embedded in SC walls, and the design of stud anchors (spacing and size) along the rebar length. This paper presents the results of experimental investigations conducted on SC-to-RC non-contact lap splice connections to evaluate the influence of various design and detailing parameters on structural performance, failure modes, and the ability to develop full-strength connection design. Design recommendations developed previously for SC-to-RC non-contact lap splice connections were reviewed and modified based on the results of experimental investigations.

Post-fire concrete edge failure in single and multiple anchors pre-loaded in shear

Concrete edge failure after fire is investigated in this study with the focus on the effect that preloading in shear may have on residual capacity of anchors. Headed stud anchors with single stud, two- and four anchor groups are exposed to the various duration of fire and loaded in shear perpendicular to the free edge of the concrete member up to failure, in both hot and cold state (after cooling) conditions. The influence of the edge distance, embedment depth, number of studs and duration of fire on the load-bearing behavior of anchors are studied. The standard ISO 834 fire curve with fire durations of 15, 30, 60 and 90 min is employed in the simulations. The results of extensive numerical simulations show that anchor behavior is significantly influenced by the fire exposure. Due to the thermally induced damage of concrete the failure pattern, stiffness and load capacity significantly changes. After only 15 min of fire, the reduction of resistance can be more than 50% of the reference resistance. Moreover, the numerical investigations show that the preloading has a relatively strong influence on the residual shear load-bearing capacity of anchors after fire exposure.

Concrete pry-out failure of single headed stud anchors after fire exposure: Experimental and numerical study

In the present study the pry-out failure of single headed stud anchors after fire exposure is investigated experimentally and numerically. For the fire load the standard ISO 834 fire curve was employed. The influences of concrete compressive strength, embedment depth and fire duration on the load-bearing behaviour of anchors are investigated. The numerical simulations were conducted using the thermo-mechanical model that was implemented into a three-dimensional finite element (3D FE) code. The constitutive law for concrete is the temperature dependent microplane model. The numerical results were first verified based on the performed experimental tests. The influence of surface spalling of concrete on the pry-out failure resistance was investigated numerically. Subsequently, further parametric studies were carried out. It is shown the employed numerical modelling technique can successfully predict the pry-out failure mode and the load bearing behaviour of anchors after fire exposure. The experimental and numerical results show that the pry-out failure capacity of headed stud anchors is strongly reduced after fire exposure. Nevertheless, the cold state (after cooling) resistance, which is lower than the hot state resistance, is concluded to be critical for concrete pry-out failure. This is due to the fact that cooling process leads to further damage of concrete. It is demonstrated that the current design formula needs to be improved.

Push-Out Tests on Various Steel Anchors with Partial-Length Welding in Steel–Concrete Composite Members

To investigate the behavior of various steel anchors, push-out tests were performed for 13 test specimens. Test parameters included the geometry of beams (wide-flange beams and composite beams) and the type of steel anchors (stud anchors and Z- and C-channel anchors with full- or partial-length welding). Test results showed that the performance of test specimens strongly depends on the types of steel anchors rather than the geometry of steel beams. The specimens with C-channel anchors showed the highest load-carrying capacity but the most drastic load reduction after the peak load. The specimens with Z-channel anchors showed a similar behavior to those with C-channel anchors but the load reduction occurred at a slightly slower rate. The load-carrying capacity was increased with the length of the Z- and C-channel anchors. The specimens with stud anchors reached the peak load at a slow rate and showed the most ductile behavior. The test results were compared with predictions by various design equations for steel anchors available in the literature, and the existing design equations for channel anchors with partial-length welding were considered applicable to design.

Experimental investigation of concrete edge failure for single stud anchors and anchor groups after fire exposure

In the present study headed stud anchors with single stud, two- and four-stud anchor groups are exposed to various duration of fire and after cooling (cold state) loaded in shear perpendicular to and towards the free edge of concrete member up to failure. The standard ISO 834 fire curve with fire durations of 15 min and 60 min are employed in the experiment. The influence of the number of studs and the duration of fire on the load-bearing behaviour of anchors is experimentally investigated. As expected, the results show that the anchor behaviour is significantly influenced by the fire exposure. Due to the thermally induced damage of concrete the failure pattern is changing from the typical concrete edge failure to a combination of concrete edge failure and pryout failure. For fire duration of only 15 min, the reduction of resistance can be more than 50% of the reference resistance. After 60 min of fire, the reduction factor is approximately corresponding to the reduction factor for 90 min of fire exposure according to current Eurocode 2. Considering concrete capacity method (CC-method), it is demonstrated that simply replacing the compressive strength of concrete at ambient temperature with the reduced compressive strength after fire is not appropriate for predicting the resistance of single stud anchors and anchor groups. However, the projected area ratio of the fracture seems to be valid for predicting the resistance of anchor group based on the reduced resistance of corresponding single stud anchor after fire exposure.

Cyclic behavior of c-shaped composite plate shear walls – Concrete filled

A Composite Plate Shear Wall/Concrete Filled (C-PSW/CF) is a special lateral-force resisting system consisting a sandwiched panel of two steel plates with concrete infill in between them, ideally suited for core-wall structures in high-rise construction. The steel plates are connected to each other using tie bars that are embedded in the concrete infill and, in some instances, steel-headed stud anchors. This research project was conducted to investigate the cyclic lateral load behavior of these walls, in terms of strength, and drift capacity. The testing program includes two large-scale C-shaped concrete filled composite plate shear core walls subjected to flexure and axial loads together. Their dimensions were the same, but different axial loads were applied up to 19% of axial loading capacity. The composite behavior and the plastic hinge development were investigated and compared to results from plastic moment calculations. This provides valuable results on the expected behavior of one composite cross-section that is frequently used in full core wall. This is done to support the development of design guidelines for high-rise core-wall steel buildings having C-PSW/CF as the primary lateral force resisting system.

Monotonic shear strength of headed studs in reinforced infill walls

Headed studs are key components of structures which facilitate composite behavior between steel and concrete elements. In steel building structures, reinforced concrete infill walls surrounded by a stiff steel frame is a common example of a composite structure used to resist horizontal loads such as those produced by earthquakes or wind. To this end, these types of concrete walls need to be anchored to the steel frame with headed studs which must withstand shear and tensile forces (AISC 360). To properly design headed stud anchors in concrete walls, it is first necessary to understand their behavior when subjected to monotonic shear forces considering edge conditions and reinforcing details that may influence the stud strength.Few tests have examined headed studs subjected to monotonic shear with typical boundary effects in reinforced infill walls, so a new experimental study on 17 specimens explores the behavior of headed studs exposed to monotonic shear loading with group effects. The experiments showed that the strength of studs installed in infill walls with edge conditions is well predicted (average error in prediction is smaller than 10%) by ACI 318, AISC 360 and EC-4. However, when group effects of anchors are included in the analysis of infill walls, only the ACI 318 is able to predict the behavior.

Pryout capacity of headed stud anchor groups with stiff base plate: 3D finite element analysis

AbstractConcrete pryout failure mode of a group of relatively shallow embedded anchors welded to a steel base plate has not been extensively investigated in the past. Therefore, the failure mechanism and resistance of such anchor groups needs to be clarified. In this paper a three‐dimensional (3D) finite element parametric study for quadruple (2 × 2) anchor groups loaded in shear with no influence of edges is carried out. In the study, embedment depth of anchors and anchor spacing in both directions are varied. The results show that the increase of anchor spacing perpendicular to the shear load direction has no major influence on the concrete pryout capacity, whereas the increase in anchor spacing parallel to the loading direction significantly increases the pryout capacity. For anchor spacing greater than a particular threshold value, the pryout resistance of a group of anchors is approximately equal to the resistance of a single anchor multiplied by the number of anchors. Based on the results of the study, a design formula for anchor group failing in pryout is proposed and compared with the current design code recommendations.

Aggregate effect on concrete cone capacity

Recently, a large experimental campaign was completed that attempted to establish a link between petrography of the coarse aggregate, the concrete material properties and the system response in terms of concrete cone capacity. The investigation focused on three normal strength concretes having different coarse aggregate types (quartz, limestone, basalt) but otherwise similar mix design. All specimens of each concrete were cast from the same batch, carefully cured following three sets of curing protocols, and systematically characterized. The investigation comprised aggregate and concrete characterization, and structural tests performed at two ages on cast-in headed stud anchors under tensile loading. The aggregate characterization included the determination of Los Angeles coefficient, hardness and Young’s modulus. In order to characterize the concretes, standard compression and indirect tension tests, were performed together with fracture tests. The experimentally obtained material and structural data finally served for the evaluation of current predictive models in terms of concrete compressive strength or concrete fracture properties as well as a correlation study. Aided by photogrammetric analysis, the concrete cone shape was determined for each individual test and analyzed to uncover possible dependencies on the coarse aggregate type.

Steel-Plate Composite Wall-to-Wall T-Joints: Joint Shear Strength

Steel-plate composite (SC) walls are used in the containment internal structures (CIS) of safety-related nuclear facilities. CIS are typically composed of multiple SC walls intersecting each other and forming SC wall-to-wall joints. These joints should preferably be designed to be stronger than the connected SC walls so that the walls develop flexural yielding prior to joint failure. To ensure that flexural yielding of the connected SC walls occurs first, it is important to estimate the shear strength of the SC wall-to-wall joints. This paper presents the results of an experimental investigation on the fundamental behavior and the strength of SC wall-to-wall T-joints. The test parameters included in the investigation were the detailing of the joint region, which they included the presence and number of tie bars and distribution of stud anchors. The results from the investigation suggest that the structural behavior of SC wall T-joints is remarkably similar to the behavior of reinforced concrete beam-column joints. In addition, it appeared that the effects of detailing the joint region on the behavior and strength are not significant. The measured joint shear strength compared favorably with the design equations for reinforced concrete beam-column joints.

Monotonic and cyclic behavior of headed steel stud anchors welded through profiled steel deck

Composite floor systems rely on shear connection, commonly using headed steel stud anchors, to ensure that the steel beam and concrete slab work together as a unit, but also to transfer load from the diaphragm to the lateral force-resisting system. Under cyclic loading, slip and degradation can occur at the shear connection, affecting the seismic response of the floor and building systems. For composite floors using anchors welded through profiled steel deck, the slip and degradation may be more severe than floors with solid concrete slabs. In this paper, a series of push-out tests were conducted to study the monotonic and cyclic behavior of headed steel stud anchors in composite beams with profiled steel deck. The parameters that were investigated include the profile type, steel deck direction, and loading conditions. The results show both the monotonic and cyclic response are affected by the shape of the profile with newer, closed profiles, performing better than others tested. Additionally, comparisons are made between the test results and several design codes.

Features of finite element analysis of steel-reinforced concrete slabs from hollow core slabs

The present article is devoted to the calculation and finite element analysis of steel-concrete composite slabs from precast hollow-core slabs in the software package ABAQUS with the use of ABAQUS/Explicit and ABAQUS/Standard solvers taking into account the installation stage. The behaviour of the fragment imitating the steel-reinforced concrete work section on the basis of a beam with a zone of equal deformations is considered. The load was applied to two beam nodes at a distance of 0.5 m from the support, thus forming a zone of pure bending at the site of the slab’s inclusion in the beam work. The inclusion in the work of precast hollow-core slabs is provided by the installation of stud anchor on the slab’s ends welded to the upper flange of the beam, while the length of the support plates increasing. Based on finite element analysis, carried out engineering and theoretical studies, the authors obtained dependences describing the behaviour of steel-concrete composite slabs. The analysis of the results showed good convergence of the finite element analysis results and theoretical solutions. The discrepancy between the results of finite element analysis and theoretical methods was less than 5%.

Pushout tests on deconstructable steel-concrete shear connections in sustainable composite beams

This paper presents the results of pushout test of deconstructable clamping connectors which are utilized to connect precast concrete planks and steel beams in a deconstructable composite floor system. A specified turn-of-the-nut rotation was first established to ensure reliable pretension in the bolts. Nine specimens were then tested to study the effects of key parameters, including bolt diameter, reinforcement layout, loading protocol, use of shims and number of cast-in channels. It is shown that the clamping connectors have excellent slip capacity, ductility and energy dissipating capacity. The characteristics of the clamps are compared to steel stud anchors in terms of strength, stiffness and ultimate slip. Design recommendations are also provided to predict the slip and peak strengths of the clamps under monotonic and cyclic loading.

Experimental Evaluation of Steel-Plate Composite Walls Subject to Blast Loads

AbstractSteel-plate composite (SC) walls consist of a concrete infill sandwiched between two steel faceplates. The faceplates are anchored to the concrete using stud anchors or ties, and connected ...

Concrete edge failure of single headed stud anchors exposed to fire and loaded in shear: Experimental and numerical study

In the present study the results of experimental tests and numerical simulations on single headed stud anchors cast in concrete member and loaded in shear against concrete edge are presented and discussed. The anchors were exposed up to 90 min of fire and loaded in shear under hot and cold conditions up to failure. The temperature distribution, load-displacement curves and failure patterns were recorded. The numerical simulations were conducted using a thermo-mechanical model that was implemented into a three-dimensional finite element (3D FE) code. The constitutive law for concrete was the temperature dependent microplane model. The results of numerical analysis, including the temperature history profile, load-displacement response and the failure load, were verified by the experimental results. Subsequently, a parametric study was carried out. The experimental and numerical results show that the shear capacity of headed stud anchors is strongly affected by the fire exposure. Especially the cooling process leads to severe loss of load capacity. It is shown that the design formula according to Eurocode 2, Part 4 (Annex D) for concrete edge failure at 90 min of fire is rather conservative for the loading in the hot state, however, it overestimates the resistance for the cold state.