Abstract: A stress-chemistry method was used to investigate the expansion behavior of mortars made with steel slag sand (SSM). The results indicated that periclase and free CaO were the main mineral components resulted in expansion of SSM by means of volume increment and local stress concentration after hydration. So it can be concluded that stress concentration arised from enrichment and uneven distribution of expansile mineral components was the main reason resulted in the volume expansion of SSM. Model of expansion of SSM was built according to the characteristics of crack and types of versicolor particles.
Abstract: Reactive Powder Concrete (RPC) is a new kind of engineering material with high strength, high elastic modulus and high durability. In order to satisfy the low-height requirement, RPC is adopted to design the railway bridge. One simple-supported RPC T-beam with span of 32m is designed and applied in railway bridge engineering. The height of the beam is 1.8m and the height to span ratio is 1/17.8. It is supper low-height beam for railway bridges. The parameters of material properties, mixing proportion, section size and prestressed steel strand cable arrangement of the RPC T-beam are presented. The load bearing capacity, the deflection and the crack resistance safety coefficient are calculated and the results can satisfy the requirements of the code. It is useful for the design and application of RPC in structure engineering.
Abstract: The crack criterion is important to determine the crack propagation for mode I-II fracture in concrete. The paper aims to obtain the initial crack criterion of four-point shearing beams experimentally, which can be applied in the numerical simulation for crack propagation process. A series of experiments of four-point shearing notched beams of concrete with five different heights of 80mm, 100mm, 120mm, 140mm and 160mm respectively were carried out to measure the initial loading Pini. The different combinations of KiniI and KiniII corresponding to Pini were obtained according to different positions of pre-cracks in the specimens, and the initial crack criterion was fitted using the combinations of KiniI and KiniII. With the assumption that the crack will extend when the difference between the stress intensity factor at the crack tip caused by the load P and the one caused by the cohesive force attained the above KiniI- KiniII curve, the criterion was applied to simulate the crack propagation process in the paper. It was found that the numerical analysis showed a good agreement with the experimental results and that the size effect is not remarkable for the KiniI-KiniII curves of different heights specimens in the test.
Abstract: The elastic-plasticity of ten cross-section reinforced-concrete short-limb shear wall specimens under monotonic load are analyzed by ANSYS, which compares the change of load capacity, stiffness and ductility of the shear wall when concrete strength grade and limb-length ratio change. The analysis results show that when concrete strength grade is C30, shear wall of this shape can be made with better performances in load capacity and deformation capacity, and when limb-length ratio is 0.6, the ductility and the ability of the energy dissipation of shear wall is not good, which provides a significant basis for practical engineering section design.
Abstract: Five different types of self-compacting unbonded prestressed concrete beams are designed to study the bearing properties of self-compacting prestressed concrete flexural members. And experimental studies are conducted on their cracking loads, flexural strengths, ductility of members and failure forms. The testing results provide references for design and establishing related codes of self-compacting prestressed concrete structures.
Abstract: This article describes the static experiment of externally prestressed concrete beam under the beeline reinforcing patterns. It adopts the damage mechanics - superimposed load - finite element method, uses damage constitutive equation to replace the constitutive equation, which does not take the damage into account, self-compiled eight-node uniform-parameter element superimposed load finite element program is used to analyze the forced distortion of experimental beam. The value analysis results show: the damage mechanics can soundly reflect the complicated behaviors of concrete materials in the load-superimposing process and has obtained the values of the concrete material damage characteristic parameters and achieved the results that are consistent with the experiment. Therefore, damage mechanics has provided a new way in studying the nonlinear behaviors of concrete materials.
Abstract: Crack control design of reinforced concrete structure focuses on the cracks caused by temperature and shrinkage stress, which is traditionally controlled through “resistance” or “relieving”. Related standard of China adopts easier way of expansion joint to relieve temperature and shrinkage stress. This method, however, is difficult to apply to modern super large buildings. Principle of “resistance in conjunction with relieving” was adopted in the design of Yongjin Plaza in Zhejiang province. No running through expansion joint was made in 136m×124m cast-in-situ multi-story concrete frame, instead, expansion joint is adopted in partial roof and floor. Steel bar quantity in coumns and beams was determined by factors of both load and temperature. Later-poured-zone, low expansion concrete, limited cement ratio and good curing measure were adopted to control cracks successfully.
Abstract: The article makes pushover analysis for two multiplayer frames(one common frame and one abnormity columniation frame)and three small high-rise structures (shearwall, short-climbed shearwall and frame-shearwall structure)based on software ADINA. Consequently, from displacement, vibration period and storey shear force, it is shown that the abnormity columniation frame can meet the seismic requirement and the short-climbed shearwall have better seismic capacity.
Abstract: Finite element models of both the concrete filled square steel tube and a Cuboid impactor were developed, incorporating ANSYS/LS-DYNA. Three stages of time history curve of the impact force of the concrete filled square steel tube including the impact stage, stable stalemate stage, the decaying stage were generalized according to its dynamic response. And with the wall thickness increased, the peak of the impact force and the platform value is also increase, with axial force increased, the peak impact force hardly changed, but the impact platform value have a certain extent lower. Then four stages of time history curve of the impact displacement were proposed according to the dynamic response of the impact of the concrete filled square steel tube based on numerical analysis, four stages include in elastic deformation stage, plastic deformation stage, elastic rebound stage, free vibration stage in the position of the residual deformation. Finally, time history curve of the impact force and displacement according to the dynamic response is analyzed under the impact of the corner of the concrete filled square steel tube, the results show that the anti-impact capability of 45 degree angle is higher than that of the front impact.
Abstract: The flexural strength of shotcrete which prepared for cementitious material incorporated with cements,accelerating agents and expensive agents is studied.By changing the fraction of steel fibers by volume and the addition percentage of expensive agent in binding material,the influence on flexural strength of the two factors is investigated,the mechanism of steel fibers and expensive agents work together to reinforce the shotcrete and the strength development law are analyzed.The result shows that, the flexural strength of steel fiber reinforced shotcrete is improving with the volume fractions of steel fibers increasing.And the flexural strength of shrinkage-compensating shotcrete is decreasing with the addition percentage of expensive agent in binding material adding except 6%. The flexural strength of shotcrete is rather better when the fraction of steel fibers by volume is 1.2%~1.6% and the addition percentage of expensive agent in binding material is 8%,which indicates that the restriction effect of steel fibers can enhance the flexural strength of shrinkage-compensating shotcrete,embodies the effect of synergistic enhancement and compounding effect with steel fibers and expensive agents.