Bridge failures underline the significance of extremely thorough testing of materials. The collapse of the incomplete pedestrian bridge at Florida International University in March 2018 provides an example where design errors resulted in growing cracks as described by OSHA.
Image Credit: Shutterstock/ Felix Mizioznikov
Although failure of material is not the only reason for bridge failures, it is a vital step for choosing the correct materials, the analysis of bridge design, and construction testing.
Bridge members include the superstructure, the upper part consisting of beams, decks, bearings, curbs, and more and the substructure including abutments, piers, beam seats, and wingwalls. The first bridges were constructed out of timber, stone, and masonry.
Bridges are presently constructed by the use of concrete, steel, fiber-reinforced polymer (FRP) composites, and an amalgamation of materials. Material properties considered include durability, fatigue resistance, corrosion, material weight, service life, maintenance needs, and expense.
Material science plays a significant part in choosing the right materials for bridge design and their application in constructing bridges. Each material has its own advantages and must be analyzed with care, depending on the bridge size, locale, environment, loads expected, and more.
Mechanical properties of particular materials like FRP composites can be developed by changing volume and orientation of the fiber reinforcement to enable greater strength. As a matter of fact, FRP composites are engineered materials that have been of use in bridges after material researchers managed to strengthen the reinforced concrete through the use of other materials such as carbon, glass and aramid fiber reinforced polymers.
Material Testing Solutions
ADMET material testing systems can be used in analyzing the mechanical properties of various materials including concrete, composites, metals, and more.
Concrete Testing
ADMET has been engaged with concrete testing for a number of years, from retrofitting simple compression test frames with servo control to supplying advanced high temperature systems to take measurements of the Modulus of Elasticity and Poisson’s Ratio at temperatures of operation. Built into the software are analysis routines for easy usability and quick time-to-results.
Equipment
eXpert 2600 Dual Column Testing Machine
eXpert 2600 series universal testing systems are on offer in table top and floor standing configurations up to 400 kN (90,000 lbf) force capacity. The servo-control motor enables tests to be run at extremely slow net deflection rates. In consequence, greater capacity eXpert 2600 models issued with MTESTQuattro software are frequently of use in running complicated testing standards like ASTM C1609.
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eXpert 2654 – ASTM C1609 Concrete Test. Image Credit: Admet Inc.
eXpert 1600 Servohydraulic Testing Machine
eXpert 1600 servo-hydraulic testing systems, able to measure up to 600 kN (135,000 lbf), are developed to conduct compression, tension, and flexion testing.
Both the eXpert 2600 and the eXpert 1000 universal testing systems can be outfitted with various accessories including the ASTM C469 compressometer-transducer assembly, ASTM C1609 bend fixture assembly with two transducer installed, simple compression platens or spherically seated compression platens, as well as the EN 14651 bend fixture with one transducer mounted mid-point on the fixture.
MegaForce Automatically Controlled Hydraulic Power Unit
The MegaForce Testing System was designed to address the problems with concrete systems that are manually-operated and the high expense associated with typically used servo-hydraulic testing systems designed with big and costly actuators, the system can be used with compression machines that operate up to 69 MPa or 10,000psi.
Dependent upon the indicator selected with the system, automated compressive strength test reports are created, saving time as well as expenses needed to create reports by hand while reducing the risk of errors. Some examples of ADMET indicators of use in concrete testing applications can be seen below.
DFG Concrete Indicator
DFG indicator, commonly used in the running of ASTM C39, C78, and C109 test procedures, reports the peak load and stress together with the specimen geometry, dimensions, time, date, and specimen number. Further test report parameters frequently coveted by testing labs include the average rate of loading and the cylinder correction factor that are automatically calculated, the operator ID, specimen weight and age, submitted by the operator, and the cylinder break type and cap type.
ADMET’s GaugeSafe Data Exchange software is at one’s disposal for DFG indicators to enable the raw test data exported in ASCII comma delimited format for more developed analysis in typical spreadsheet programs.
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Hydraulic Testing Machine equipped with ADMET’s MegaForce. Image Credit: Admet Inc.
Gauge Buster 2 Indicator
Gauge Buster 2 characteristics include an Auto-Test-Reset mode for hands-free operation, bar graph load rate display, permanent test data storage and the additional auxiliary (encoder) and strain (analog) channels for running ASTM C469 testing.
GaugeBuster 2 Basic can have additional upgrades with printer capabilities or the USB flash drive port, which enables the saving of test results, XY data, test settings, and calibration tables straight to a flash drive. Additionally, all GaugeBuster 2 models can be outfitted with the GaugeSafe Basic, Plus, or Live software.
For those that are considering an upgrade from manual to automated concrete testing, ADMET supplies a variety of equipment for concrete testing, which includes indicators to be used with current manually-controlled systems, controllers to retrofit servo-control machines, the MegaForce Concrete Testing system specially made for the testing of concrete, as well as servo-control machines that enable various concrete testing to be performed on a single system.
Composites Testing
ADMET provides a complete line of electromechanical and servohydraulic universal testing machines to determine the mechanical properties of composite materials. Each system is outfitted with MTESTQuattro® the pc-based materials testing software which can conduct tests under strain, force and displacement control.
Testator® will also create stress vs. strain curves and find the strength, modulus and yield properties in compression, tension, shear and flexure in accordance with typical ASTM composite material test methodology.
Operators may select either servohydraulic or electromechanical testing systems to conduct typical ASTM testing standards such as:
- ASTM C273 – Standard Test Method for Shear Properties of Sandwich Core Materials
- ASTM C297 – Standard Test Method for Flatwise Tensile Strength of Sandwich Constructions
- ASTM D3039 – Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials
- ASTM D3410 – Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials with Unsupported Gage Section by Shear Loading
- ASTM D5379 – Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method
- ASTM D5528 – Standard Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites
Equipment
eXpert 2600 Dual Column Testing Machine
eXpert 2600 series dual column electromechanical testing machines are available in table top units to 100 kN (22,500 lbf) and floor standing units to 400 kN (90,000 lbf). These machines have the wide column spacing and force capacities to perform various composite testing including shear, tension, compression, and flexion.
eXpert 1600 Series Servo-Hydraulic Static Testing Machine
eXpert 1600 series static test systems are offered with capacities from 50 kN (11,250 lbf) to 600 kN (135,000 lbf). The hydraulic power supply and electronics are integral with the frame thereby conserving highly valued lab space.
eXpert 1900 Series Servo-Hydraulic Dynamic Testing Machine
eXpert 1900 series dynamic test systems are on offer in capacities from 10 kN (2250 lbf) to 250kN (55,000 lbf). Each eXpert 1900 Series tester is engineered to reach the force-stroke-frequency imperatives of each application. Dependent upon the size of the hydraulic power supply (HPU), the 1900 Series HPU is either free-standing or an integral part of the frame.
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eXpert 1000 Series equipped with High-Capacity Wedge Grips. Image Credit: Admet Inc.
Metals Testing
ADMET materials testing systems define significant characteristics of metals like elastic modulus, elongation, yield, reduction of area, R-value, n-value, Poisson’s ratio, fracture toughness plus a lot of torsional properties.
Operators may choose either electromechanical or servohydraulic testing systems to perform typical metals ASTM testing standards such as:
- ASTM A370 – Standard Test Methods and Definitions for Mechanical Testing of Steel Products
- ASTM A938 – Standard Test Method for Torsion Testing of Wire
- ASTM E8 – Standard Test Methods for Tension Testing of Metallic Materials
- ASTM E9 – Standard Test Methods of Compression Testing of Metallic Materials at Room Temperature
- ASTM E111 – Standard Test Method for Young’s Modulus, Tangent Modulus, and Chord Modulus
- ASTM E399 – Standard Test Methods for Linear-Elastic Plane-Strain Fracture Toughness KIc of Metallic Materials
- ASTM E646 – Standard Test Method for Tensile Strain-Hardening Exponents of Metallic Sheet Materials
Equipment
eXpert 2600 Dual Column Testing Machine
All eXpert 2600 systems can conduct dependable and duplicable compression, tension, peel, and flexure tests. ADMET provides a complete line of grips, fixtures, load cells, extensometers as well as heating and cooling for the systems.
eXpert 1600 Series Servo-Hydraulic Static Testing Machine
The eXpert 1600 servohydraulic testing systems are used in many places to test metal products at load capacities up to 600 kN. ADMET’s simple to use servohydraulic systems offer accuracy by steering clear of having to compensate for piston friction and operate with highly precise, self-identifying ADMET load cell technology. The pumping system can fit inside the machine table on the majority of models, which results in a compact design.
eXpert 1900 Series Servo-Hydraulic Dynamic Testing Machine
The eXpert 1900 dynamic servohydraulic testing machines conduct fatigue testing of metals at forces up to 250 kN (55,000 lbf). These systems enable automatic calculation of vital parameters such as the amount of cycles to failure, the utmost load at failure, fracture toughness, dynamic modulus, and more.
These systems can be changed to the requirements of the operator. Features that can be customized include the separation between columns, the vertical test space, the power stroke, and the piston locale.
eXpert 9000 Series Torsion Testing Machine
The test bed length or frame structure of eXpert 9000 series torsion systems can be changed to accommodate various specimen sizes and lengths. Load cells and displacement sensors can be brought in to take measurements of axial forces and spindle displacement. Torsion testing machines are offered in horizontal or vertical orientations for static and fatigue testing applications.
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Metal Tension Testing per ASTM E8. Image Credit: Admet Inc.
Conclusion
ADMET testing systems are on offer for research and testing on materials used in bridges. Recommended equipment for these materials illustrates the fact that the versatility of ADMET’s universal testing machines enables many types of materials, like concrete, composites, and metals, to be tested with one system rather than being forced to buy separate testing equipment for each new material.
This information has been sourced, reviewed and adapted from materials provided by Admet, Inc. - Materials Testing Equipment.
For more information on this source, please visit Admet, Inc. - Materials Testing Equipment.