Xiao Ke Li

A Review of Stee-Polypropylene Hybrid Fiber Reinforced Concrete

The steel-polypropylene hybrid fiber reinforced concrete can take full advantages of macro-scale crack resistance and toughening effect on the concrete matrix of steel and polypropylene fibers. The shortcomings of concrete are improved and there is a wide prospect application in engineering. This paper summarizes the enhancement theories of hybrid fiber reinforced concrete to explain its strengthening mechanism. The research status is reviewed including mix proportion design, working performance of fresh concrete, mechanical behaviors, durability (impermeability, shrinkage and others), and engineering applications etc. Some further researches are forecasted. It would be very useful to apply and popularize steel-polypropylene hybrid fiber reinforced concrete.

Static Loading Test and Evaluation of Single Beam of Highway Prestressed Concrete Hollow Slab Beam Bridge

Since the main beams of a prestressed concrete hollow slab beam Highway Bridge stored for too long, in order to assess its bearing capacity, static loading test and bearing capacity evaluation of single beam was conducted. The hollow slab beam at the locations where the transverse distribution coefficient is biggest was chose for testing, and the transverse distribution coefficient at midspans of the slab beam was calculated by the hinged slab method. By comparing the theoretical and measured values of displacement and stain at key points of the beam, structural performance of the beam was finally evaluated. The test results showed that both the strength and stiffness of the beam was conforming to the requirements of the specification and able to satisfy normal use requirements in serviceability limit state.

3-D FE Analysis on Loading Performance of Tunnel Under-Across Main Canal of South-to-North Water Transfer Project

Under the background of engineering application, a 3-D FE analysis was carried out to evaluate the loading performance of a two-hole pair-arch tunnel under-across the main canal of South-to-North Water Transfer Project. In fact, the tunnel was constructed in integral longitudinally without obeying the design requirement of parting within certain length. The analysis showed that the vertical deformation and tensile stress along the longitudinal axis are obviously affected by the loads from main canal, moreover, the tensile stress exceeds the limit of tensile strength of concrete, which may lead thoroughly cracks on top plate of tunnel. This analysis determined the crack zone which should be dealt with.

Simulated Environment Test on Weather Fastness of Fair-Faced Concrete for Urban Bridge

To keep the perfect, artistic and natural characteristics of fair-faced concrete, it is necessary realizing its weather fastness. This paper introduces the simulated environment test for weather fastness of fair-faced concrete considering the environmental actions at all seasons such as washing of acid rain, sand blown by the wind, exposure to blazing sunlight, salt-fog, carbonization and freeze-thaw. Test methods for sand blown by the wind, washing of acid rain, slow freeze-thaw and exposure to blazing sunlight were invented. The mass change of concrete were measured, and the surface quality was evaluated by the glossiness, the pixel difference and the variance of pixel difference. The results showed that the mass had a little change under the comprehensive actions. The factors decreasing the surface quality in sequence from serious to slight were the washing of acid rain, the salt-fog, the freeze-thaw and the carbonization. The erosion degree increased with the increasing pH value in rainwater and the increasing density of sulfate-ion in salt-fog solution. The surface of concrete damaged by the long-term freeze-thaw and carbonization. The sand blown by the wind, and the exposure to blazing sunlight had little influence on the surface of concrete.

Structural Design and Artistic Expression of Landscape Multi-Span Arch Footbridge

In order to perfectly make the bridge function, structural style, architectural art modeling with the surrounding environment, this paper, based on the design of landscape five-span arch footbridge, studies the span arrangement, structural style, building materials, railing shape, ornament style and color, and lamplight illumination of the bridge considering the factors such as hydrology, geology, surrounding environment (e.g. buildings and park), traffic flow and entire urban planning. To reduce the stress of main arch and the horizontal thrust of substructure, the new structure of T-frame with sloped plate was put forward to bear the deck loads with the assistance of main plate arch. The thin concrete walls were cast on the top sides of the main plate arch, which were decorated by fine stone with the modern decoration construction technology. The white marble railings present lively morphology with carved lotus and pomegranate on the column cap, and many kinds of flowers on the panels. The spotlights make dramatic night sense for the bridge. Therefore, the landscape footbridge in the classical arch graceful shape was constructed by the modern building material and the optimized reinforced concrete structure, which presents the unity and coordination of structural design and artistic expression.

Static Analysis of Prestressed Concrete Cantilever Bridge

Due to geological conditions at abutment, working mechanism and economy, a prestressed concrete bridge with double cantilevers is designed. Main dimensions and drawings are introduced and static analytical results of prestressed concrete cantilever bridge are discussed. The numerical model was built by the integrated solution system for bridge and civil Engineering-MIDAS/Civil. The main loads which affect internal force and deflection at key sections of bridge are studied, such as mid-point, support point and free end of cantilever bridge. The rules which loads affect internal forces and deflections are revealed. The results show that dead weight is an important load to control internal force and deformation of bridge with double cantilevers. The design and numerical results would give some references to the optimization of similar bridges.

A Review on Frost Resistance of Steel Fiber Reinforced Lightweight Aggregate Concrete

Compared with ordinay concrete, weight of lightweight aggregate concrete could be lower 20%-40% under same bearing capacity. Mixed with some given steel fibers in it, crack resistance and flexural strength will be improved. Once lightweight aggregate concrete mixed with steel fibers meets the requirements of frost resistance, it could be applied to most civil engineerings in a cold area. In this paper, the frost resistance mechanism of steel fiber reinforced lightweight aggregate concrete is introduced. The research status of frost resistance of steel fiber reinforced lightweight aggregate concrete is reviewed including the effects of water cement ratio, aggregate, mineral admixture and amount of fiber, frost resistance experimatal methods and engineering applications etc. Some further researches are prospected.

Study on Seismic Performance of Archaized Steel Tower

Combined with the design of Tiantang Site Protection Exhibition Project in Luoyang, China, the seismic performance of an archaized steel tower is studied in this paper. Firstly, a finite element model of whole structure is built accurately with ANSYS software. Then the dynamic behaviors of steel tower are analyzed. The natural vibration frequency and mode shape are obtained. Compared with dynamic test at site, the theoretical values are verified and it is reasonable about adopted loads and boundary conditions in the finite element model. After that, the seismic behaviors of steel tower are calculated and analyzed under seismic intensity 7 degree with methods of spectrum analysis and time-history analysis. The distribution characteristics of displacements and stresses are revealed. The results prove that the seismic performance of the given archaized steel tower can meet the code requirements. It is believed that the results in this paper would give some reference for the design of similar steel tower structures.

Monitoring and Analysis on Erection of Archaized Steel Tower

Combined with erection of an archaized steel tower in Luoyang, China, stresses in key members, displacements of control nodes and temperature variation of steel skeleton were monitored and analyzed. The temperature range for erecting structure is optimized based on finite element simulation analysis with 5°C, 10°C, 15°C and 20°C as closure temperature. It is confirmed by actual test values of steel tower. And the recommended temperature range is given between 15°C and 20°C. In case of dead weight + live load + temperature, test values are consistent with theory values. Maximum tensile stress and compressive stress are 64.0MPa and-61.0MPa respectively. The structure is safe during whole process of erection. The result obtained in the paper would have some references for the design and construction of similar steel structures.

Nondestructive Testing and Static/Dynamic Loading Detection of a Diseased Fabricated Hollow Slab Bridge

Combined with a repaired project, an old twin decks bridge by simply supported the fabricated prestressed concrete hollow slabs with 16m span was detected in-site. The two decks were built separately in 1987 and 1997 because of economic reasons and demands of traffic flow. The aim of test was to decide whether the bridge can be further used or should be strengthened to meet the demands according to the current design code. Firstly, the damaged and corroded situations of whole bridge were investigated. Then the nondestructive testing methods were adopted to detect the concrete strength and carbonation depth of slabs and piers. The static loading test was conducted to make sure the service behaviors such as crack and mid-span deflection of the whole bridge. Finally, whole bridge was detected by dynamic loading test. The results show that the bridge has enough flexural stiffness to prevent larger deflection and most of slabs are in good service performance. But attacked by the environmental factor such as acid rain, CO2 and winds erosion etc., part of slabs, all railings and sidewalk flats should be replaced. Based on service conditions, the suggestions are given to recover the strength and durability of the bridge. The conclusions would serve as a reference for similar engineering structures.