Estimation of Live Load Distribution Factor for a PSC I Girder Bridge in an Ambient Vibration Test

Maintenance of bridges in use is essential and measuring the live load distribution factor (LLDF) of a bridge to examine bridge integrity and safety is important. A vehicle loading test has been used to measure the LLDF of a bridge. To carry this out on a bridge in use, traffic control is required because loading must be performed at designated positions using vehicles whose details are known. This makes it difficult to measure LLDF. This study proposed a method of estimating the LLDF of a bridge using the vertical displacement response caused by traveling vehicles under ambient vibration conditions in the absence of vehicle control. Since the displacement response measured from a bridge included both static and dynamic components, the static component required for the estimation of LLDF was extracted using empirical mode decomposition (EMD). The vehicle loading and ambient vibration tests were conducted to verify the validity of the proposed method. It was confirmed that the proposed method can effectively estimate the LLDF of a bridge if the vehicle type and driving lane on the bridge are identified in the ambient vibration test.

Tree Top Walk at Serralves Park, Portugal

<p>The current paper describes the structure and the dynamic behaviour of a footbridge built in Serralves Park at Porto, Portugal. The footbridge, named Tree Top Walk, is located in a slope in the park at the height of the top of the trees. Because it is in a slope, the footbridge develops with an irregular U-shape at a constant level. The total length of the footbridge is approximately 250 m. At its highest level, the height is 15 m.</p><p>Approximately at one third of the course there is a passage between the two branches of the U. At this zone, there is a staircase that allows to reach the footbridge at the middle of its course, from the woods and a small amphitheatre at a level of 14 m. The structure of the deck is made with timber while the columns are made with steel covered with timber across their height and the connection between the columns and the deck is performed with timber struts placed in the longitudinal and transversal directions. Three of the columns are made with a circular profile, while the others are 4-foot tubes connected at the top by a circular tube with</p><p>2.35 m length. The deck is made with four longitudinal girders with a cross section of 8x52 cm. Spans have different lengths, ranging from 5 to 14,34 m. In total there are 23 spans and 22 columns. In the structural analysis, dead loads, live loads, wind and earthquake actions were considered. To assess the dynamic behaviour of the structure, dynamic tests have been carried out. The performed tests include an ambient vibration test, the determination of the damping level and tests with pedestrians.</p>

Using an ambient vibration test to identify damage in a sculpture

<p>This paper describes the studies conducted to assess damage in a sculpture. These include a numerical model and an ambient vibration test based on a dense mesh of points to identify the fundamental natural frequencies and the corresponding modal shapes. From the comparison between identified and calculated modal parameters, it was possible to identify a region of inflexion of curvatures of the second-order vibration modes at a particular location that was associated with a local fragility of the structure. A posterior removal of the cladding evidenced a highly degraded area at this location.</p>

Serviceability analysis and increased axle load performance of heritage arch gallery railway bridge

This investigation deals with the serviceability analysis and increased axle load performance of Bridge No. 541 of UNESCO recognised Kalka Shimla Mountain Railways, which is a multi-storey arch gallery stone masonry bridge situated in the state of Himachal Pradesh, India. For this purpose, a finite element (FE) model was developed based on the drawings and reports available in Shimla Division, Northern Railways, India. Further, the results obtained from ambient vibration test (AVT) and operational modal analysis (OMA) is utilized to model update the initial FE model by modifying the mechanical properties of stone masonry. The serviceability against present-day axle loading (H Class Loading, Indian Railways) and present speed of the train is assessed. At last, a parametric study is conducted to understand the feasibility to attain higher speeds (up to 40 kmph) of the present axle load and higher axle load with different speeds of the train over the bridge to check the serviceability conditions advised in the Indian Railways code and also International codes. Finally, the study concluded that Bridge No. 541 of Kalka Shimla Mountain Railways can sustain speeds up to 40 kmph for current axle loading satisfying serviceability conditions.

Developing a Feature Extraction of Existing Structures Using an Ambient Vibration Test

The paper aims to extract the dynamic properties of existing structures without utilizing the analytical models. The ambient vibration testing could be used on any type of frame such as concrete, steeland masonry to investigate the structural vulnerability.The method could bethe first stage and necessarily forthe retrofit process. To achieve this aim, the ambient vibration testing can also be employed. The experimental data obtained from the methodcan be used to monitor the health, evaluating, and damage detection structures at present. The achieved datacan be comparedin future with the recorded signals at different times.

Developing a Feature Extraction of Existing Structures Using an Ambient Vibration Test

The paper aims to extract the dynamic properties of existing structures without utilizing the analytical models. The ambient vibration testing could be used on any type of frame such as concrete, steel and masonry to investigate the structural vulnerability. The method could be the first stage and necessarily for the retrofit process. To achieve this aim, the ambient vibration testing can also be employed. The experimental data obtained from the method can be used to monitor the health, evaluating, and damage detection structures at present. The achieved data can be compared in future with the recorded signals at different times. So, the ambient vibration test was carried out on the building of Imam Hossein Hospital at Mashhad. Then, its dynamic characteristics of the acceleration records are obtained by using Data Acquisition System with three accelerometers in two perpendicular coordinates. The method is more accurate and practical compare with analytical models of the existing buildings. The ambient vibration test prevents of several points such as destructive testing or may irreparable damage to the building as well as high cost. Even, the ambient vibration test maybe required for every couple of decayed, when noticed of any changes in the condition of buildings after construction. These type of changes could be quality of concrete or welding or some changes in the location of walls that can be affected the dynamic specifications of the building. The method provides real lateral load pattern and actual modes that can evaluate existing condition of the building compare with the time of construction.

Structural System Identification of Elevated Steel Water Tank Using Ambient Vibration Test and Calibration of Numerical Model

This research aims to investigate the feasibility of using ambient vibration testing for system identification of an elevated water tank. To identify the natural dynamic properties, the experimental study is carried out on an elevated steel water tank located in Tehran. The tank is instrumented with a sensitive velocimeter sensor (microtremor), and the ambient velocity of the tank is recorded for 30[Formula: see text]min in three orthogonal axes. Employing the peak-picking method in the frequency domain, the fundamental frequency of the tank is determined as about 1.9[Formula: see text]Hz. Then, the numerical model of the tank is generated and calibrated based on the obtained data. In the primary modeling, the values of natural frequencies of the tank are in good agreement with the results of the ambient vibration data. This finding is judged to be reasonable considering no clear sign of corrosion in the steel material.