EK682
Spreadsheet. Minimum cross-sectional dimensions of a reinforced concrete members under fire conditions according to EC2
EK568
In the splitting test, a cylinder is loaded in compression on two diametrically opposite pads. The concrete is in a biaxial (compression-tension) state of stress and tensile failure occurs on […]
EK563
When a primary flexural crack forms and crosses the reinforcing steel, the concrete adjacent to the crack slips against the steel. Slip, or bond-slip, is defined as the relative movement […]
EK561
Tension stiffening is only effective if a bond mechanism can transfer a tensile force between the steel and surrounding tensile concrete. The nature of the bond mechanism also changes at […]
EK558
Tension stiffening in a flexural member is the additional stiffness provided by the tensile stress in the concrete between primary flexural cracks. The tensile force in the concrete is transferred […]
EK548
Polypropylene and polyethylene ducts did not confine the grout after theformation of widespread splitting cracks in the concrete.
EK543
When the pull on the bar is small, high stresses develop near the loaded end of the bar; some slip of the bar occurs as adhesion between the bar and […]
EK537
The splitting resistance of concrete can be enhanced if confinement stresses are superimposed onto the tensile ring stresses around the reinforcing bar.
EK536
The angle at which the steel rib bears on the concrete changes as load acting on the reinforcing bar increases.
EK535
After adhesion is lost and ribs begin to bear on the concrete, slip occurs by progressive crushing of the porous concrete paste structure in front of the rib. The compacted […]
EK532
Slip of a deformed bar occurs as a result of both the wedging action of the steel ribs pushing the concrete away (splitting), and due to the crushing of concrete […]
EK531
When a ring in the concrete surrounding the bar is stressed to rupture, it breaks and longitudinal (splitting) cracks appear on the concrete surface.
EK530
Radial components of the bond forces are resisted by tensile stress rings in the concrete surrounding the bar.
EK529
The effect of chemical adhesion is small, and friction does not occur until there is slip between the reinforcing bar and the concrete.
EK527
Bond between reinforcing bars and concrete is made up of three components: chemical adhesion, friction, and mechanical interlocking of bar lugs (ribs) with the surrounding concrete.
EK526
Bond refers to the interaction between reinforcing steel and the surrounding concrete that allows transfer of tensile stresses between the steel and concrete.
EK466
Expansion or isolation joints are used to help prevent cracking due to the thermal dimension changes in concrete. They usually are placed where there are abrupt changes in thickness, offsets, […]
EK465
Construction joints occur where two successive placements of concrete meet.
EK463
Contraction joints are used mainly to control locations of cracks caused by shrinkage of concrete after it has hardened.
EK439
Shrinkage for concrete is the volume reduction with time.
EK400
For heavily-loaded columns or those carrying large moments resulting in high compressive forces the bedding should be fine concrete using a maximum aggregate of 10 mm size and a water-cement […]
EK397
Anchorage of the holding-down bolts into concrete foundation should be sufficient to cater for any uplift forces.
EK391
In general a plain or slab base is used for pinned conditions or when there is very little tension between the plate and the concrete.
EK390
The function of a column baseplate is to distribute the column forces to the concrete foundation.
EK335
Some brittle materials, such as cast-iron and concrete, contain large numbers of microscopic cracks in their structures. These are believed to give rise to high stress concentrations, thereby causing local […]
EK321
Too much water in the mix creates water reservoirs. Channels lead from the reservoirs to the surface, where a watery laitance forms. A weak surface results, leading to concrete crazing, […]
EK320
Concrete compressive strength increases with a higher cement content and a lower water-cement ratio.
EK295
If shear reinforcement is not provided, shear resistance in reinforced concrete members is developed by a combination of the following mechanisms: Shear resistance of the uncracked concrete. From 20% to […]
EK284
If adequate splice length is not provided, splitting and spalling occurs in the concrete shell.
EK283
No bars should be spliced as the same location to avoid a weakness in the concrete section and to avoid the congestion of bars at the same location, which may […]
EK278
The joint behavior of steel and concrete in a reinforced concrete member is based on the fact that a bond is maintained between the two materials after the concrete hardens. […]
EK277
The factors involved in controlling main cracks are the reinforcement stress, the bond characteristics of reinforcement, the distribution of reinforcement, the diameter of the steel bars used, the steel percentage, […]
EK275
Main cracks develop at a later stage than secondary cracks. They are caused by difference in strains in steel and concrete at the section considered.
EK274
Corrosion secondary cracks form when moisture containing deleterious agents such as sodium chloride, carbon dioxide, and dissolved oxygen penetrates the concrete surface, corroding the steel reinforcement. The oxide compounds formed […]
EK273
Usually secondary flexural cracks are widely spaced, and one crack does not influence the formation of others. They are expected to occur under low loads, such as dead loads. When […]
EK272
Shrinkage cracks affect the pattern of cracking that is produced by loads in flexural members. When they develop, they form a weak path in the concrete. When load is applied, […]
EK270
Secondary cracks, very small cracks that develop in the first stage of cracking, are produced by the internal expansion and contraction of the concrete constituents and by low flexural tension […]
EK269
In general, concrete cracks may be divided into two main types: secondary cracks and main cracks.
EK268
The design of a D-region includes the following steps: Define and isolate each region. Determine the resultant forces acting on each D-region boundary. Select a truss model to transfer the […]
EK264
Up to four rebars can be bundled when they are enclosed by ties. All bundled bar may be treated as a single bar for checking the spacing and concrete cover […]
EK262
The effect of temperatures below 250 degrees Celsius is small on concrete, but definite loss of strength is expected at higher temperatures.
EK261
A reduction of up to 30% of the strength of unreinforced concrete may be expected when concrete is subjected to a concentric sustained load for 1 year.
EK254
Creep increases with an increase of stress in specimens made from concrete of the same strength and with the same duration of load.
EK253
Creep takes place in the hardened cement matrix around the strong aggregate. It may be attributed to slippage along planes within the crystal lattice, internal stresses caused by changes in […]
EK252
Concrete is an elastoplastic material, and beginning with small stresses, plastic strains develop in addition to elastic ones. Under sustained load, plastic deformation continues to develop over a period that […]
EK250
Generally, concrete shrinks at a high rate during the initial period of hardening, but at later stages the rate diminishes gradually. 15% to 30% of the shrinkage value occurs in […]
EK249
Exposure of concrete to wind increases the shrinkage rate on the upwind side. Shrinkage causes an increase in the deflection of structural members, which in turn increases with time. Symmetrical […]
EK248
If concrete is kept moist for a certain period after setting, shrinkage is reduced; therefore, it is important to cure the concrete for a period of no fewer than 7 […]
EK247
The change in the volume of drying concrete is not equal to the volume of water removed. The evaporation of free water causes little or no shrinkage. As concrete continues […]
EK243
Shear strength may be considered as 20% to 30% greater than the tensile strength of concrete, or about 12% of its compressive strength.
EK241
The concrete specimen under axial compression may fail in combination of shear and splitting.
EK240
The concrete specimen under axial compression may fail in the separation into columnar pieces by what is known as splitting, or columnar fracture. This failure occurs when the strength of […]
EK239
The concrete specimen under axial compression may fail in shear. Resistance to failure is due to both cohesion and internal friction.
EK238
Under 1-day sustained loading, concrete may lose about 10% of its compressive strength.
EK237
Under sustained loads for years, the ultimate strength of concrete is reduced by about 30%.
EK236
The strength of concrete increases with age, and hydration of cement continues for months. For normal portland cement, the increase of strength with time, relative to 28-day strength may be […]
EK235
A water-cement ratio of 0,5-0,7 may produce a concrete strength of about 35 MPa and 20 MPa respectively.
EK234
A water-cement ratio of 0,25-0,35 may produce a concrete strength of about 40 MPa.
EK233
A water-cement ratio of about 0,35 or higher is needed for the concrete to be reasonably workable without additives.
EK230
Concrete floor slabs should have movement joints at around 20-30 m.
EK200
When steel bars or rods are placed across the joint, shear forces can be transferred between elements by dowel action. The dowel is loaded by shear at the joint interface […]
EK183
Shear compression failure occurs if a flexural crack develops into a shear crack which propagates through the member into the compression zone, leading to an eventual crushing of the concrete. […]
EK120
Torsional moments produce shear stresses which result in principal tensile stresses inclined at approximately 45 degrees to the longitudinal axis of the member. Diagonal cracking occurs when these tensile stresses […]
EK119
Concrete is weak in tension. Microcracks begin to generate in the matrix of a structural element at about 10% to 15% of the ultimate load, propagating into macrocracks at 25% […]
EK115
Although concrete has low thermal conductivity, and thus good resistance to temperature rise, the strength begins to drop significantly at temperatures above 300 degrees Celsius and it has a tendency […]
EK100
Typical curve showing the evolution of the temperature of concrete in a structural element:
EK86
Figure represents the distribution of principal stresses across the span of a homogeneous concrete beam. The direction of the principal compressive stresses takes the form of an arch while the […]
EK70
For some materials such as concrete in a simple compression test, there is a region beyond the failure or peak point in which the slope of the stress-strain curve is […]
EK66
Although tension stiffening has a minor influence on flexural strength, additional stiffness is provided at all sections, except right at the cracks, and this has a significant effect in decreasing […]
EK65
Tension stiffening in a flexural member is the additional stiffness provided by the tensile stress in the concrete between primary flexural cracks.