Building Vibration Measurement with the VM 40 Vibration

Building Vibration Measurement with the VM 40 Vibration Monitor Metra Mess- und Frequenztechnik in Radebeul e. K. www. MMF. de

Why Measure Vibration in Buildings? • Buildings and other large structures like tunnels or pipelines are exposed to vibration • Buildings must sustain vibrations, structural integrity and bearing capacity of ceilings and other components has to be ensured • Historic buildings require special attention (typical damages are cracks in walls or older cracks become wider) • Vibrations may affect habitability and working conditions Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 2

Sources of Building Vibration Examples: • Construction • Industrial machinery • Road traffic • Railway lines • Explosions Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 3

Purposes of Building Vibration Measurement • Problem recognition: Occupants of a building report that a building is vibrating, measurements are carried out to evaluate the risk for structural integrity • Control monitoring: Maximum permissible vibration values have been established and those vibrations have to be measured • Documentation: Measurements are made to verify predictions of response in the design of a building • Diagnosis: Measurements are made at deeper levels of investigation to provide information for mitigation procedures Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 4

Catastrophic Failure Collapse of Rana Plaza commercial building in Dhaka (Bangladesh) in 2013 Vibrations due to power generators overloaded the Building structure Vibrations and cracks were ignored Death toll 1134 Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 5

Vibration Measurement • Vibrations can be measured with sensors for displacement, velocity and acceleration • Basis for evaluation is the peak value of vibration velocity [mm/s], also called “peak particle velocity” (PPV) Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 6

Vibration Measurement Piezoelectric accelerometers consist of - Piezoceramic or quartz sensing element - Seismic mass Vibration acts vertically. The inertia of the seismic mass causes a force on the piezoelectric material which results in a electric signal. Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de

Parameters of Excitation • Amplitude • Frequency • Duration • Direction Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 8

Guide Values • Some standards, like DIN 4150 -3, give reference values which are based on the experience of a large number of practical measurements • At vibration amplitudes below these guide values damages are unlikely • If results are above the guide values a deeper analysis should be made Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 9

Types of Vibration Duration Transient Vibrations Not strong enough to cause material fatigue Too short and too rare to be increased by resonances Continuous Vibrations May cause material fatigue May stimulate resonances Resonances may increase vibration magnitudes Both types may occur during a monitoring period. In such cases a separate evaluation of these intervals is recommended. Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 10

Standards for Building Vibration • German DIN 4150 -3 with various derivatives in other countries: Vibration in buildings - Part 3: Effects on structures • British BS 7385: Evaluation and measurement for vibration in buildings. Guide to damage levels from ground borne vibration • Swiss SN 640312 a: • Vibration immission in buildings • ISO 4866: Mechanical vibration and shock - Vibration of fixed structures Guidelines for the measurement of vibrations and evaluation of their effects on structures • French Circulaire du 23/07/86 Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 11

DIN 4150 -3: Transient Vibrations (continued) • Maximum values of the two horizontal vibration velocities at the upper floor level are measured and show the maximum response of the structure to horizontal ground vibration • The higher value of the two is used for evaluation • Relevant is the main frequency Y Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de X 12

DIN 4150 -3: Transient Vibrations (continued) • Alternatively: Maximum values of the three vibration velocities at the foundation are measured • The highest value of X/Y/Z is used for evaluation • Relevant is the main frequency Z Y Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de X 13

DIN 4150 -3: Transient Vibrations (continued) • Vertical (Z) vibration velocity can be measured in the middle of ceilings where the highest vibration values occur • Below 20 mm/s peak vibration damage is not expected Z Z Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 14

DIN 4150 -3: Transient Vibrations (continued) Guide values for vibration velocity vi for transient vibration Building Type Foundation Ceiling 1 – 10 Hz 10 – 50 Hz 50 – 100 Hz all Frequencies X/Y/Z X/Y Z Reinforced or framed structures; Industrial and heavy commercial buildings 20 mm/s 20 – 40 mm/s 40 – 50 mm/s 40 mm/s 20 mm/s Unreinforced or light framed structures; Residential or light commercial type buildings 5 mm/s 5 – 15 mm/s 15 – 20 mm/s 15 mm/s 20 mm/s Delicate, listed buildings e. g. historical monuments 3 mm/s 3 – 8 mm/s 20 mm/s Metra Mess- und Frequenztechnik Radebeul / Germany 8 – 10 mm/s www. MMF. de 15

DIN 4150 -3: Transient Vibrations (continued) Graphical representation of the guide values for transient vibration Industrial buildings Residential buildings Delicate / historical buildings Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 16

DIN 4150 -3: Transient Vibrations (continued) Guide Values for Transient Vibrations in Other Structures: • For massive structures like block foundations or abutments a guide value of 80 mm/s can be used Guide values for transient vibrations in tunnels and caverns Type of lining Vibration Velocity vi Steel, sprayed concrete, tubbings 80 mm/s Concrete, natural stone 60 mm/s Brickwork 40 mm/s Guide values for transient vibrations in underground pipelines Pipe material Vibration Velocity vi Steel, welded 100 mm/s Stoneware, concrete, reinforced concrete, pre-stressed concrete, metal 80 mm/s Brickwork, plastic, drainage tubes 50 mm/s Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 17

DIN 4150 -3: Continuous Vibrations • Relevant is the highest horizontal vibration velocity on the highest floor level Y Y • X X Alternatively measurement points at the foundation can be used if the response characteristics of the upper floors are known Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 18

DIN 4150 -3: Continuous Vibrations (continued) Guide values for vibration velocity vi for analyzing the effects of continuous vibration Building Type Upper ceiling level, all Frequencies Direction X / Y (horizontal) Z (vertical) Reinforced or framed structures industrial and heavy commercial buildings 10 mm/s Unreinforced or light framed structures, residential or light commercial type buildings 5 mm/s 10 mm/s Delicate buildings, listed buildings e. g. historical monuments 2. 5 mm/s 10 mm/s Notice: Above limits may be exceeded for short time when building machines are switched on and off. Such vibrations are evaluated as transient vibrations. Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 19

DIN 4150 -3: Continuous Vibrations (continued) Guide values for continuous vibrations in underground pipelines Pipe material Vibration Velocity vi Steel, welded 50 mm/s Stoneware, concrete, reinforced concrete, pre-stressed concrete, metal 40 mm/s Brickwork, plastic, drainage tubes 25 mm/s Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 20

DIN 4150 -3: Measuring Points The following advice is given in DIN 4150 -3 for the placement of sensors: • For foundation vibrations the transducer should be placed on the lowest floor at the foundation or on the outer wall. • In the upper ceiling level the sensor should be placed inside or very close to the outer wall for horizontal vibration (X/Y). • Vertical direction (Z) should be measured in the middle of ceilings where the highest amplitudes can be expected. The highest vertical vibrations do not always occur on the highest floor. • For buildings without a basement the measurement location must not be higher than 0. 5 m above the ground level. Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 21

DIN 4150 -3: Measuring Points (continued) • The measurement location should predominantly be on the side of the building facing the excitation • One of the lateral coordinates (X / Y) should be parallel to an outside edge of the building • Buildings with larger ground areas should be measured at several points. • When measuring pipelines, where possible, the sensor should be placed on the pipeline itself Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 22

DIN 4150 -3: Measuring Report Contents of the measuring report: • General: Institution, customer ID, person in charge, time and date, duration of measurement, reason of measurement • Type of excitation: - Description of vibration source (explosion, pile driving, traffic, machines) - Conditions, frequency of occurrence - Other sources of excitation (man-made vibration etc. ) • Location of vibration source including dimensioned drawing • Measuring conditions: weather, type of ground, groundwater etc. • Measuring object: - Address - Kind of building (residential, industrial, historical) - Description: type of construction, size, foundation, state of repair Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 23

DIN 4150 -3: Measuring Report (continued) • Measuring points: - Location and direction of sensors - Sensor mounting - Duration of measurement for each location - Serial numbers of sensors - Drawing with dimensions • Measuring chain: - Transducer principle and model - Signal conditioners - Recording equipment - Last calibration - Tools for data analysis (equipment type, software) • Recording Parameters - Frequency range, sample rate - Trigger limits Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 24

DIN 4150 -3: Measuring Report (continued) • Special observations (susceptibility, secondary effects like noise etc. ) • Measuring results - Measured vibration values and frequencies - Duration of immission and frequency of occurrence - Special influences • Signature Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 25

VM 40 B Building Vibration Monitor Properties • Stand-alone device including - High-sensitivity accelerometer - Signal conditioning - Recording - Cellular modem - Battery • Triaxial measurement of - Vibration velocity - Vibration acceleration - Main frequency • SMS alerts Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 26

VM 40 B Building Vibration Monitor (continued) Operation Place the instrument on the measuring site. The optional Tripod Floor Plate VM 40 -BP can be used to place on uneven or soft surfaces. Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 27

VM 40 B Building Vibration Monitor (continued) Preparing measurement Press the ON/OFF button Open the menu (F 3 button) Device settings/Axis adjustment and adjust the case so that the dot is in the center Return to the main menu (F 3) and select Measuring mode, choose DIN 4150 -3 Select the type of vibration: - Short time (transient) - Sustained (continuous) Select the type of building: - Industrial building - Residential building - Listed building - Pipeline Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 28

VM 40 B Building Vibration Monitor (continued) • Select the location of measurement: - Foundation - Upper ceiling • Select the frequency range: - 1 to 80 Hz (standard) - 1 to 315 Hz (for blasting) Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 29

VM 40 B Building Vibration Monitor (continued) Measurement display • Vibration values for X/Y/Z • Main frequency and its direction • Limit curve of the chosen standard and vibration spectrum • Battery condition, Date and time Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 30

VM 40 B Building Vibration Monitor (continued) Recording / Monitoring • Open the menu and choose Recording, Start recording • Select the recording mode: - At warning/alarm event: The VM 40 only records a measurement if warning* level is reached or the limit curve is exceeded - Time-controlled: The VM 40 records in given time intervals - Event and time control: The VM 40 records at Warning or Alarm and additionally in time intervals * Warning level can be entered in percent of the alarm limit in Alarms/GSM menu Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 31

VM 40 B Building Vibration Monitor (continued) • Enter the recording interval in seconds Tip: Do not enter short time intervals to avoid large amounts of irrelevant data. The VM 40 always keeps the maximum amplitude since the last saving so that no vibration data gets lost. • Enter a name for the record Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 32

VM 40 B Building Vibration Monitor (continued) SMS notification • Activate or skip SMS notification at vibration alarm events (SIM card must be inserted, only at the first time PIN needs to be entered) • Enter the maximum number of SMS per day, the minimum time between two SMS and one or two receivers from the SIM card's phone book (see GSM/SMS menu) • Activate or skip the key lock function (key lock is released by pressing all arrow buttons simultaneously) • The VM 40 B will start recording Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 33

VM 40 B Building Vibration Monitor (continued) Viewing recorded data in the instrument • Viewing recorded measurements in the menu Recording / View/edit/delete files, the shown header data includes - Name of the recording - Start time and date - Standard and settings - Recording mode • Choose a file (set of measurements) and then scroll between the measurements, each record is shown with - Running number - Time and Date of recording - X/Y/Z amplitudes and main frequency Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 34

VM 40 B Building Vibration Monitor (continued) Transferring recorded data to a PC • Connect the supplied USB cable and install the VM 40 USB driver on the PC • Install the free database software VM 40 -MDB • Click Load data from VM 40 Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 35

VM 40 B Building Vibration Monitor (continued) • The PC software imports header data of the recordings • Click the check boxes of the recordings you like to load from the VM 40 Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 36

VM 40 B Building Vibration Monitor (continued) • Mark a recording and click Show • In the Properties tab you see - Record name - Recording period - VM 40 name and serial number - Used standard - Trigger mode – Number of saved measurements - Number of warnings and alarms - Maximum values for X/Y/Z • Further description text can be entered Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 37

VM 40 B Building Vibration Monitor (continued) Printing a Report • Click Open protocol • Several menu tabs need to be opened to fill in all necessary data for a DIN 4150 -3 compliant report - Customer and person in charge - Details about the source of vibration - Description of the monitored structure - Information about the location and the measuring point - Environmental and other conditions - Measuring results to be included Metra Mess- und Frequenztechnik Radebeul / Germany www. MMF. de 38