STRENGTH RECOVERY OF STEEL BRIDGES WITH CORROSION NEAR BEARINGS

A lot of steel plate girder bridges were erected during the rapid growth in the 1960s in Japan. Currently, the condition of those aging bridges has become marked and a problem in society since over 50 years have passed. Particularly, the corrosion-induced deterioration and damage in railway steel plate girder bridges, which have an open deck, is becoming prominent. Despite that, the evaluations of residual strengths and the strengthening methods of corroded bridges are not always enough. Therefore, firstly, this paper shows analytical-based evaluation results that explain how the residual shear capacities of plate girders, having corrosion near bearings, depend on the condition of the corroded surface, such as a vertical stiffener or a web. The results show the fracture mode as buckling changes as well as the residual shear capacity, according to the degree and form of corrosion. Next, this study proposes a reliable reinforcement measure to recovery the shear capacity by applying said evaluation results and analytical models. Finally, the shear capacity could be improved tremendously by simple attachments as reinforced members.

IoT-Based Electricity Bill for Domestic Applications

This work proposes a real-time electricity bill for quantifying the energy used in domestic facilities in Mexico. This bill is a low-cost tool that takes advantage of the IoT technology for generating an easy reading real-time bill allowing the customers to constantly review and administrate their energy consumption. Using low-cost sensors and the electronic board Particle® Photon, an energy meter is proposed. The presented prototype is extremely compact and satisfies safety measures to be used by anyone in a domestic installation. The measurement data is displayed and processed in real-time, and an appropriate algorithm determines the accumulated kWh. The energy consumed is displayed using an Html interface of easy interpretation for the customers, given recommendations about their consumption habits and some alarms in case of abnormal or high consumption. As a reinforcement measure for avoiding large consumption bills, the system is programmed to send messages to the user, remembering if the estimated consumption is large.

A Theoretical Calculation Method of Influence Radius of Settlement Based on the Slices Method in Tunnel Construction

At present, the empirical formula is used to calculate the influence radius of surface settlement and the width of settlement trough, which lacks theoretical support. Aiming at this problem, this paper derived the theoretical calculation formula for predicting the influence radius of formation settlement based on the slices method. Then, the expression of the width of settlement trough was obtained according to the relationship between the settlement influence radius and the settlement trough width. The rationality of the formula was verified by the Heathrow Express tunnel and the Green Park tunnel. Through analysis and discussion, it was found that in the clay stratum, the settlement calculation formula can more accurately predict the surface settlement, while there is a big error in predicting the stratum settlement within 4d near the tunnel vault. In the sand layer, the internal friction angle is less than 40°, and the reinforcement surface is applied to the unsupported face to reduce the radius of influence; in the clay formation, when the cohesion is less than 50 kPa, the influence radius can be reduced by applying reinforcement measure to the unsupported face.

Stability Analysis and Reinforcement of a High-Steep Rock Slope with Faults: Numerical Analysis and Field Monitoring

This study presents a stability analysis of a high-steep rock slope with two faults during excavations and evaluates the effectiveness of a proposed reinforcement method using prestressed anchor cables. A 3D finite difference model was established based on the strength reduction method using FLAC3D software. The influence of various fault conditions and the effectiveness of the reinforcement on the slope stability during the excavation process were analyzed and compared to field monitoring data. The numerical analysis and field monitoring results showed that the fault close to the slope surface (f20) was prone to the local instability under external forces caused by the excavation, but a fault further away from the slope surface (f14) had insignificant influence on the stability of the slope. Based on the numerical analysis results, the proposed reinforcement measure can increase the factor of safety (FOS) of the slope by 19.2%. The field monitoring data also showed that the displacement of the monitoring point gradually decreased after the reinforcement, and the deformation of the slope was effectively controlled.

Grouting Reinforcement of Large Building Foundation over Old Gob Areas: A Case Study in Huaibei Mining Area, China

There are more than 14,000 square kilometers of mining subsidence areas in China, most of which have been reclaimed for the construction of new buildings. In the past, few special measures were required for the foundations of small buildings above old gob areas. But a plan was created to construct a large office building 100 m in length, 90 m in width, and 100 m in height, above old gob areas in the Huaibei subsidence area. However, the results of exploration borehole data and borehole TV observation indicated a broken bedrock stratum and developmental fractures above the old gob areas, and thus, the space stabilities of the building foundation were poor. Therefore, grouting reinforcement measure was adopted for the old gob and foundation areas. And the grouting effect was examined using borehole TV observation and the water injection test, where the detection results of boreholes TV observation showed that the filling ratio of the stratum fracture was over 85%, and the stability of the foundation was obviously enhanced. In addition, we monitored the settlement of the foundation continuously for 930 days. The results show that the maximum cumulative subsidence was 15.3 mm and the maximum slope was 0.05 mm/m, which verifies that grouting reinforcement is feasible in terms of the safety of large buildings constructed over old gob areas using bedrock stratum grouting in the Huaibei subsidence area.

An Index for Estimating the Stability of the Layered Rock Masses under Excavation Disturbance

The mechanical behaviours of layered rock mass exhibit significant differences in the directions parallel and vertical to the bedding planes. The deformation and failure of a layered rock mass has remarkable weak-plane dependence, which brings a major challenge to the control of the stability of the surrounding rock mass in underground openings. In this study, a layered rock mass is firstly regarded as a composite material composed of interlayered rocks and bedding planes. Then, based on the Mohr–Coulomb and maximum tensile stress criteria, an index of point safety factor for a layered rock mass is established considering the mechanical properties of interlayered rocks and bedding planes. The safety of the artificial layered rock mass specimens in the triaxial test is evaluated using this index. The results show that the distribution of this index is in good agreement with the macroscopic failed zone of the rock specimen, indicating that this index is feasible for characterizing the macroscopic failure of rock masses. Finally, the index is adopted to evaluate the stability of the midpartition between the #3 and #4 diversion tunnels at the right bank of the Wudongde hydropower station before and after its reinforcement. The results indicate that there is a yielded zone where the point safety factor is less than 1.0 in the unreinforced midpartition of the collapsed tunnel section, and it is nearly connected. If it is not reinforced in time, collapse cut-through of the entire midpartition may occur and then endanger the overall stability of the tunnel. After the emergency reinforcement measure with two-ended anchored piles and concrete backfill, the safety of the midpartition is significantly improved. In this case, the safety factor is much larger than 1.0, indicating that the adoption of this emergency reinforcement measure is effective.

A New Reinforcement Measure Suited for Space Truss with No-Fire Operation

A new reinforcement measure with no-fire operation is presented, which is very suitable for space trusses which are located in gas stations. A finite element model (FEM) is presented with shell elements and multipoint constraint elements. With this FEM, nonlinear analyses are carried out. Analytical results show that integral failure of reinforced pipe is caused by yielding of original pipe inside. So it is not necessary to reinforce original pipe using steel pipe bonded outside with high yield strength. With the increase of length of bonded pipe outside, loading according to elastic stage and ultimate bearing loading increase, it is clear that the length of bonded pipe outside is an important factor which influences the bearing capacity.