Proposed Modifications to ACI 318-95 Tension Development and Lap Splice for High-Strength Concrete

Safety concerns and a lack of test data are responsible for the current upper limit of 100 psi on the square root of the concrete compressive strength for use in calculating tension development and lap splice lengths. Based on recent research on the lap splice strength of reinforcing bars in high-strength concrete, modifications to current design criteria are formulated that will allow removal of the limit on the square root of the compressive strength, ensure adequate ductility and bond, and improve the overall safety of the tension development and lap splice criteria in ACI 318-95 for concrete with strengths above 10,000 psi. The result of the analyses used to develop the new design criteria indicate that increasing lap splice length, without providing transverse reinforcement, does not provide an adequate level of ductility in high-strength concrete members. Adequate ductility can be achieved by using a minimum splice length, as defined by ACI 318-95 for beams without transverse reinforcement, plus a minimum quantity of transverse reinforcement over the tension development/lap splice length with an area equal to 50% of the area of the bars being developed/spliced

Behaviour of fasteners under monotonic or cyclic shear displacements

An experimental program was carried out to investigate the behaviour of metallic fasteners (undercut, torque controlled expansion and chemical anchors) embedded in cracked concrete and subjected to shear displacements, under shear displacements is similar. Fasteners situated close to an edge and loaded towards the edge exhibit brittle concrete failure. Cyclic loadings are possible only for displacements which are much lower than the values corresponding to the monotonic peak load. Fastenings away from an edge will cause steel failure with large displacements. During cyclic loading, a severe force-response degradation was observed. Empirical formulae are proposed to predict the strength of anchors, as well as strength degradation during cyclic loading

Anchorage to concrete

Summarizing it can be said that material models based on plasticity and stress-strain relationships together with stress criteria indicating failure do not catch all aspects of anchor behavior as observed in experiments. Furthermore the predicted failure load depends on the element size and number of load steps. A better explanation of anchorage behavior can be expected by means of fracture mechanics

A fracture mechanics based description of the pull-out behavior of headed studs embedded in concrete

According to the experiments the behavior of headed studs embedded in a large concrete block and loaded in tension with the support reactions relatively far away from the anchor is controlled by stable growth of the circumferential failure crack up to maximum load. Just before reaching maximum load the area of cracked concrete is only some 25% to 30% of the whole surface of the fracture cone, which is mainly formed in the descending part of the large embedment depth loaddisplacement curve the load transferred in the cracked area is relatively small compared to the total load

Fracture analysis of concrete plane-stress pull-out tests

This paper reports on a parameter study which was performed for the Round Robin Analysis Of Anchor Bolts organized by RILEM Committee TC-90 FMA (Fracture Mechanics Applications). 18 plane-stress pull-out specimens were analyzed by the computer program SBETA which is based on the finite element method and takes into account nonlinear fracture mechanics. A simplified formula for the design of such anchors is derived

Bond between concrete and steel

The bond behaviour under alternating loading is analysed following a short description of the behaviour under monotonically increasing slip and unidirectional cyclic loading, respectively. Various proposals for modeling are discussed and evaluated

Computer models of concrete structures

The application of the nonlinear finite element analysis of concrete structures as a design tool is discussed. A computer program for structures in plane stress state is described and examples of its application in the research of fastening technique and in engineering practice are shown.Die Anwendung der nichtlinearen Finite Elemente Analyse auf Betontragwerke als Entwurfswerkzeug wird diskutiert. Ein Programm für die Konstruktionen im ebenen Spannungszustand wird beschrieben und Beispiele für die Anwendung in der Forschung der Befestigungstechnik und in der lngenieurpraxis werden vorgestellt

Erläuterungen zu DIN 4227, Abschnitt 10

Durch die in den Abschnitten 6, 7 und 10 angegebenen Regeln soll die Breite eventuell auftretender Risse so beschränkt werden, daß das Verhalten von Spannbetontei!en im Gebrauchszustand und die Dauerhaftigkeit des im Verbund liegenden Spannstahls und Betonstahls nicht beeinträchtigt werden. Es kann davon ausgegangen werden, daß die Karbonatisierung der Rißufer bei Einhaltung der für Bauteile im Freien bzw. unter wechselnder Feuchtigkeit geltenden Bedingungen den Spannstahl nicht erreicht, so daß eine Depassivierung der Spannstahloberfläche vermieden wird. Dies ist bei den dort genannten Umweltbedingungen notwendig, um Spannstahlkorrosion zu vermeiden

Behavior and design of fastenings with headed anchors at the edge under tension and shear load

ABSTRACT: In the present paper the theoretical aspects and the application of the non-linear finite element program MASA for analysis of anchorages placed at an edge of a concrete block are discussed. After an introduction the structure of the finite element (FE) code is briefly described. The results of the simulations are shown and compared with experimental data. They confirm that the FE code is able to simulate realistically the behavior of anchorages. Subsequently a parametric study is caITied out and the results are discussed

Creep and fatigue analysis of reinforced concrete structures

A computional procedure for the creep and fatigue analysis of reinforced concrete structures exposed to flexure is presented. The fatigue loading effects are modified into an equivalent creep analysis. The analysis is based on the finite element method employing beam elements. The material behavior of steel, concrete and bond between reinforcement and concrete are described as realisticly as possible. For the reinforcing steel the stress-strain behavior as measured in tests or given in codes is assumed. For the stress-strain behavior of concrete in compression under static loading, the proposal by Park/Pauley is taken. The influence of sustained or fatigue loading is taken into account by using the isochrone σ-ε-relationship valid for t > t o or N > 1 respectively; whereby the creep coefficients for both type of loadings are taken from MC90. For sustained and fatigue loading the isochrone bond stressslip relationship is used. The creep coefficients are taken from MC90. The accuracy of the proposed model is checked by comparing the behavior of some test beams under sustained and fatigue loading with the predictions