When the operating or inventory rating of a bridge is less than 3 tons for any vehicle, the bridge must be closed to all traffic. The bridge is multistringer redundant with welded plate girders see figures 2, 3 and 4. At a minimum, this approach results in more accurate load ratings and many times results in increased rating factors. Repetitive load test on a composite precastdecked bridge. Repetitive load test on a composite precastdecked bridge model roberto a. Bridge failure to pass load capacity assessment is unfortunately not an uncommon problem in bridge engineering and it is a potentially expensive problem for the bridge owner. The first portion of the testing focuses one axle line of a 12ton the current posted weight limit vehicle on each of the structures 5 beams. Load testing of bridges to assess bridge performance has been in practice since at least 1891 in switzerland. The testing apparatus for static load test was designed as follows, 4 testing vehicles on the first span and e nd span. Load test 1 in the first load test, truck c, the heaviest of the four trucks, was driven at crawl speed about 5 mileshour on path 2 figure 3. Appeals 43 appendix drawings site plan diagram 45 bridge elevation diagram 46 bridge plan diagram 47 lateral load test plan diagram 48 vertical load test plan and elevation diagram 49 2020 rules 1. Primer on bridge load testing blurbs new blurbs main. Noel the results of a repetitive load test conducted on a laboratory model to study the deterioration of connections designed to develop composite behavior in precastdecked steel bridges are presented.
Data acquisition using a data logger and a 20 channel multiplexor. In your test book, you will read a question followed by four answers. The test results revealed that the bridge had considerable fixity at both abutment ends and that the girders were acting compositely with the concrete deck. When instrumenting a steel truss bridge for load testing by placing strain gages on builtup members, four gages, one placed on. Condition assessments of an existing bridge may be conducted to develop a bridge load rating, confirm an existing load rating, increase a load rating for future traffic, or determine whether the bridge must be posted in the interest of public safety. Recent reports indicate that of the over 25,000 bridges in iowa, slightly over 7,000 29% are either structurally deficient or functionally obsolete.
All the bridges load tested generally have the theoretical capacity to carry the present malaysian legal loads i. The summary results of the load test for all the bridges are presented in table 2. Bridge load testing is one of the options increasingly becoming popular among bridge owners to extend service life of inservice bridges by obtaining better estimates of the actual load capacity and as a periodic monitoring tool to evaluate new materials and designs. In the interim, the load rating of the bridge was reduced from 24 tons to 15 tons as a precautionary measure. However, a proof load test can be used to confirm that the structure can carry the maximum legal or a given permit load limit, for example. Data was collected for the first three tests at a rate of 100 samplessecond and at a higher rate of 250 samplessecond for the fourth test. Overhead crane means a crane with a movable bridge carrying a movable or fixed hoisting mechanism and traveling on an overhead fixed runway structure.
An echo films production in association with 0period productions. Arch bridges transfer significant lateral loads to foundations, so lateral load test on two fullscale rc bored piles has been performed on site to prove actual load capacity of. Stal short term axle load, but inadequate for ltal. Nchrp 1278report 700 a comparison of aashto bridge load rating methods 2011. This loadtest program integrates optical surveying systems, a sensor network embedded in bridge decks, and surface deflection analysis.
A total of 45 strain gages and 5 displacement gages were attached to the bridge to measure the response. Aashtos manual for bridge evaluation and the 1998 manual for bridge rating through load testing have been generally. Bridge deck load testing using sensors and optical survey. This is the end of the listening comprehension portion of the test. Load testing provides a useful alternative for such cases where current calculation methods, for one reason or another, cannot provide satisfactory answers to performance questions on existing bridges. In most cases, the design live load effect would be equal to or less than that due to dead load. Standard test method for nonrepetitive static plate load tests of soils and flexible pavement components, for use in evaluation and design of airport and highway pavements, astm, us. Before implementing one of these options, one should consider performing a diagnostic load test on the structure to more accurately assess its. This guide specification covers requirements for top running and under running single girder. While many of these bridges may be strengthened or rehabilitated, some simply need to be replaced. Cranewerks has 16,000 lbs of portable test weights and a test weight skid that weighs 2500 lbs. Other objectives of this research included the development, presentation and refinement of a twoday workshop on bridge rating through load testing. A fatigue crack was found in april 2009, which appears to have initiated at the top of the pier 6 bearing stiffener on an exterior girder see.
Development of bridge load testing for load evaluation tr. Bdi, developed hardware and software that is specially designed for performing bridge ratings based on data obtained from physical testing. July 29, 2014montreal, canada the maadi group engineering firms highstrength aluminum work bridge has successfully completed fullscale. This first criterion investigated was the live load deflection for steel bridges. Strengthening and load testing for short span steel bridge. These methods are allowable stress rating asr, load factor rating lfr and load and resistance factor rating lrfr. This report presents the results from a diagnostic load test performed on a reinforced concrete pangirder bridge located in buda, texas. Choose the best answer to each question and mark it. Serviceabilityrelated issues for bridge live load deflection and construction closure pours executive summary this study investigated the design criteria and practices in an effort to improve the quality of bridge designs in the state of maryland and beyond. On june th, 2011 an epic load test was conducted on a scale model bridge. The strain gages are wired together to form a wheatstone bridge, as illustrated in figure 3. Using load test data to justify increase in assessed load capacity is recognised as a viable approach in professional codes of practice. Requests to test a number of structures came from region 8 and the main office structures division.
In times when engineering models were not as accurate and available as today, a critical step in the construction of a bridge was to load test prior to opening or during the opening ceremony of the bridge. To evaluate the bdi system, the research team performed diagnostic load tests on seven typical bridge structures. Now, you will hear several short talks or conversations. To address this challenge, vec introduced an economical bridge load testing and rating system into australia. Therefore, load tests are the only way to find the real behavior of an existing bridge subjected to the rating process. Bridge load test is done to establish the relation between theoretical design and actual load carrying capacity of bridge span. Load ratings are expressed as a rating factor or as a. During the first load test, the sensor network was not yet operational. The vehicle is to cross the bridge at crawl speed, stopping for readings when the rear axle is at each sixth point of the bridge 5 readings per load sequence. Load testing was used to determine if the current load rating of the route 701 bridge could be raised. It is the law title 23, part 650 23 cfr 650 bridges, structures, and hydraulics inspection maximum of every 24 months load rating safe loadcarrying capacity aashtos the manual for bridge evaluation. Development of bridge load testing process for load. Load testing may be indicated when analysis produces an unsatisfactory result or when the analysis cannot be completed due.
These requirements were based on nchrp report 350 impact conditions and need to be revised for the higher impact severity under mash. Evaluation of bridge performance and rating through non. The bridges were load tested using two jkr scania lowloaders. Currently, the iowa department of transportation dot office of bridges and structures identifies structures to be tested and is responsible for determining. Prior to the load testing, the beam geometry was determined and the bridge structure was analyzed using the 1961 aashto specifications. However the load test proved that they are capable of carrying more than ltal loading. April 20 nmdot bridge procedures 11 and design guide chapter one general information the new mexico department of transportation uses the current edition of the aashto. Implementation of physical testing for typical bridge load. Load test the bridge nondestructive test determines actual capacity load testing found 85% of bridges adequate if load test finds inadequate, no chance of meeting aashto guidelines. The results of bridge load tests have generally shown that many structures have greater loadcarrying capacity than that predicted by calculations. During the second load test, the sensor network was functional and was used in the load test of the bridge. A recent mash test 421 with a 32inch tall new jersey profile rigid. Several bridges, including ones in serbia, switzerland, and france, collapsed. Load rating is defined as the determination of the live load carrying capacity of a bridge using asbuilt bridge plans and supplemented by information gathered from the latest field inspection.
Although the use of load testing for the purpose of load rating is not a new technique, only recently have easytouse, integrated tools been developed to facilitate the rational integration of field test results into rating calculations. The dead load is already acting and the test load is some specified multiple of live load more than one. Nowadays, finite element analyses provide information about the performance of a structure, but they are more or less simplified. The number of gauges and transducers used for a test varied depending on the stftlctural system of the bridge. Evaluation of bridge performance and rating through nondestructive load testing 7. Bridge specifications require test level 4 bridge rails to have a minimum rail height of 32 inches and to be designed for a 54kip lateral load. The westbound bridge was to be demolished soon after the load test for the construction of a new bridge. By considering various loading patterns, and associated uncertainties, a rating analysis is developed to determine the truck loads that the bridge can carry safely on a regular basis, called the inventory level, and the maximum permissible loads on the bridge, called the operating level. We are qualified to load test cranes of all capacities using water weights and other static weight options. Actual deflection of span girders should be within the theoretical estimated deflection of test span girders. Bridge analysis guide 4a1 load factor rating and load and resistance factor rating load rating methods there are three methods for performing load ratings. Purpose and scope this project was designed to determine the cause and extent of damage to the deck slab and its structural capacity. Demonstration of load rating capabilities through physical. To accomplish these objectives, a working plan consisting of eight tasks was developed and approved by trb.