Bridge failures underscore the importance of rigorous material testing. The collapse of the incomplete pedestrian bridge at Florida International University on March 2018 is an example where design errors led to growing cracks as described by OSHA.
Although material failure is not the sole reason for bridge failures, it is a crucial step for selecting the right materials, bridge design analysis, and construction testing.
Bridge members include the superstructure, the upper portion made of beams, bearings, curbs, decks, and more and the substructure including abutments, beam seats, piers, and wingwalls. Early bridges were made out of timber, stone, and masonry. Modern bridges are currently built using concrete, steel, fiber reinforced polymer (FRP) composites, and a combination of materials. Material properties taken into account include durability, corrosion, fatigue resistance, weight of material, maintenance requirements, service life, and cost.
Material science plays an important role in the selection of the correct materials in bridge design and their implementation in bridge construction. Each material has its own benefits and must be analyzed carefully depending on the bridge size, location, environment, expected loads, and more. Mechanical properties of certain materials such as FRP composites can be designed by varying volume and orientation of the fiber reinforcement to allow higher strength. In fact, FRP composites are engineered materials that have been used in bridges after material researchers were able to strengthen the reinforced concrete using other materials such as glass, carbon and aramid fiber reinforced polymers.
Material Testing Solutions
ADMET material testing systems can be used to analyze the mechanical properties of a variety of materials including concrete, composites, metals, and more.
Concrete Testing
ADMET has been involved with concrete testing for many years, from retrofitting simple compression test frames with servo control to providing advanced high temperature systems to measure the Modulus of Elasticity and Poisson’s Ratio at operating temperatures. Analysis routines are built in to the software for ease of use and fast time-to-results.
Equipment
eXpert 2600 Dual Column Testing Machine
eXpert 2654 – ASTM C1609 Concrete Test
eXpert 2600 series universal testing systems are offered in table top and floor standing configurations up to 400kN (90,000lbf) force capacity. The servo-control motor allows running tests at very slow net deflection rates. Consequently, higher capacity eXpert 2600 models equipped with MTESTQuattro software are often used for running complex testing standards such as ASTM C1609.
eXpert 1600 Servohydraulic Testing Machine
eXpert 1600 servo-hydraulic testing systems, capable of measuring up to 600kN (135,000lbf), are designed to perform tension, compression, and flexion tests.
Both the eXpert 2600 and the eXpert 1000 universal testing systems can be equipped with a variety of accessories including simple compression platens or spherically seated compression platens, the ASTM C469 compressometer-transducer assembly, ASTM C1609 bend fixture assembly with two transducer installed, 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 developed in order to address the issues with manually-operated concrete systems and the high costs associated with conventional servo-hydraulic testing systems designed with large and expensive actuators, the system can be used with compression machines that operate up to 69 MPa or 10,000psi. Depending on the indicator chosen with the system, automated compressive strength test reports are generated, saving time as well as costs required to manually generate reports while decreasing the chance of errors. Some examples of ADMET indicators used in concrete testing applications can be seen below.
Hydraulic Testing Machine equipped with ADMET’s MegaForce
DFG Concrete Indicator
DFG indicator, typically used to run ASTM C39, C78, and C109 test procedures, reports the peak load and stress along with the specimen geometry, dimensions, date, time, and specimen number. Additional test report parameters often desired 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, entered by the operator, and the cylinder break type and cap type.
ADMET’s GaugeSafe Data Exchange software is available for DFG indicators to allow the raw test data exported
in ASCII comma delimited format for further analysis in common spreadsheet programs.
Gauge Buster 2 Indicator
Gauge Buster 2 features include an Auto-Test-Reset mode for hands free operation, bar graph load rate display, permanent storage of test data and the additional auxiliary (encoder) and strain (analog) channels for running ASTM C469 testing.
GaugeBuster 2 Basic can be upgraded with printer capabilities or the USB flash drive port, which allows saving test results, XY data, test settings, and calibration tables directly to a flash drive. In addition, all GaugeBuster 2 models can be equipped with the GaugeSafe Basic, Plus, or Live software.
Composites Testing
ADMET offers a full line of electromechanical and servohydraulic universal testing machines for determining the mechanical properties of composite materials. Each system comes equipped with MTESTQuattro® our pc-based materials testing software which is capable of performing tests under force, strain and displacement control. MTESTQuattro® will also generate stress vs. strain curves and determine strength, modulus and yield properties in tension, compression, shear and flexure according to common ASTM composite material test methods.
Operators may choose either electromechanical or servohydraulic testing systems to perform common 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 1000 Series equipped with High-Capacity Wedge Grips
eXpert 2600 Dual Column Testing Machine
eXpert 2600 series dual column electromechanical testing machines are offered in table top units to 100kN (22,500 lbf) and floor standing units to 400kN (90,000 lbf). These testers have the wide column spacings and force capacities to perform a variety of composite testing including tension, compression, shear, and flexion.
eXpert 1600 Series Servo-Hydraulic Static Testing Machine
eXpert 1600 series static test systems are available in capacities from 50kN (11,250 lbf) to 600kN (135,000 lbf). The hydraulic power supply and electronics are integral with the frame thereby saving valuable lab space.
eXpert 1900 Series Servo-Hydraulic Dynamic Testing Machine
eXpert 1900 series dynamic test systems are available in capacities from 10kN (2,250 lbf) to 250kN (55,000 lbf). Each eXpert 1900 Series tester is engineered to meet the force-stroke-frequency requirements of each application. Depending on the size of the hydraulic power supply (HPU), the 1900 Series HPU is either integral to the frame or free-standing.
Metals Testing
ADMET materials testing systems determine important characteristics of metals like elastic modulus, yield, elongation, reduction of area, n-value, R-value, Poisson’s ratio, fracture toughness plus many torsional properties.
Operators may choose either electromechanical or servohydraulic testing systems to perform common metals ASTM testing standards such as:
- ASTM A370 – Standard Test Methods and Definitions for Mechanical Testing of Steel Products
- ASTM A938 – Standard Test Mehod 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
Metal Tension Testing per ASTM E8
eXpert 2600 Dual Column Testing Machine
All eXpert 2600 systems are capable of performing reliable and repeatable tension, compression, peel, and flexure tests. ADMET offers a full line of grips, fixtures, load cells, extensometers as well as heating and cooling for our systems.
eXpert 1600 Series Servo-Hydraulic Static Testing Machine
The eXpert 1600 servohydraulic testing systems are widely used to test metal products at load capacities up to 600kN. ADMET’s easy to use servohydraulic systems provide precision by avoiding compensating for piston friction and operating with highly accurate, self-identifying ADMET load cell technology. The pumping system fits inside the machine table on most models, resulting in a compact design.
eXpert 1900 Series Servo-Hydraulic Dynamic Testing Machine
The eXpert 1900 dynamic servohydraulic testing machines perform fatigue testing of metals at forces up to 250kN (55,00 0lbf). These systems allow automatic calculation of key parameters such as number of cycles to failure, maximum load at failure, dynamic modulus, fracture toughness, and more. These systems can be modified to the operator’s needs. Customizable features include the separation between columns, the vertical test space, the power stroke, and the location of the piston.
eXpert 9000 Series Torsion Testing Machine
The length of the test bed or frame structure of eXpert 9000 series torsion systems can be modified to accommodate varying specimen lengths and sizes. Load cells and displacement sensors can be incorporated to measure axial forces and spindle displacement. Torsion testing machines are available in vertical or horizontal orientations for static and fatigue testing applications.
Conclusion
ADMET testing systems are available for testing and research on materials that are used in bridges. Recommended equipment for these materials point out the fact that the versatility of our universal testing machines allows multiple materials, such as concrete, composites, and metals, to be tested with one system rather than having to purchase different testing equipment for each new material.
