Mass concrete, a common structure in bridge engineering, is frequently threatened by cracking. Based on the gravity anchorage of a long-span suspension bridge that has been in operation for more than ten years, the causes of the cracks growing year by year in the anchorage were analyzed in this paper. The refined numerical model of the anchorage was established via the space finite element software. Taking full account of the environmental characteristics of the bridge site, the temperature sensitivity of the anchorage was simulated and analyzed, and the stress distributions on the surface of each side of the anchorage at different temperatures were analyzed. The calculation results showed that there is little correlation between anchorage cracking and anchorage bolt force. Under condition 2 temperature increased 20 ℃, the principal tensile stress of anchorage reached to 1.5 times of the allowable stress, Under condition 6 anchorage surface from 40 ℃ suddenly dropped to 20 ℃, the principal tensile stress reached to 2.4 times of the allowable stress. Thus, under the dual effects of internal and external constraints, the cold hit effect of the mass concrete anchorage resulted in the sudden drop of the surface temperature of the anchorage concrete to produce "internal constraint cracks", and the overall temperature rise caused the expansion of the anchorage concrete to produce "external constraint cracks". The two types of cracks led to the vertical cracks of the anchorage. Besides, the environmental and construction factors were the main causes of cracking of transverse construction joints. At last, the anchorage was reinforced with high-performance concrete with an anti-crack reinforcement mesh, which presented good results in the follow-up observation, providing a certain reference value for similar projects.

Cable Tower Grouping-Anchorage-System of Cable-Stayed Bridges is a new type of anchorage system, which is only used in Chi-Zhou bridge in An Hui province in domestic. In order to understand the behavior characteristics and the design methods, took Chi-Zhou Bridge as an example. Firstly, the propaedeutics were introduced, and then the finite element models of the whole bridge were built in six different cases and parameters sensitivity were analyzed which included cables layouts, agglomeration forms and steel beams design. Then took introduced the beam-column stiffness ratio, studied the stiffness matching between concrete tower and steel beam and clarified the influence of grouping, agglomeration and stiffness ratio on the whole bridge. Some design suggestions were stated. The results showed that the Grouping-Anchorage-System is more advantageous on the lateral stability and torsion resistance of the whole bridge; The steel beams are the key point of design because of the stress complexity. Changing the length of the steel beam will bring about changes in the local stress and changing the space between steel beams will bring about changes in the whole bridge. Considering the layout spaces and detailing requirements, the length of steel beams should be reduced as much as possible, so as to improve the efficiency of stay cables, which is beneficial to the whole bridge stress and economy.

Aimed at the working life of bridges under the reiteration function of vehicle load, which is not mentioned in the current bridge design codes, this paper introduced the concept of normal working life. The authors regarded reinforced concrete bridges as the research object and proposed a fast method to calculate the working life to judge whether the working life can fit the requirement of design working life. On the basis of the equivalent constant amplitude stress amplitude method of Miner's criterion, the cumulative damages of the bridges were calculated, the average annual damage degrees were obtained by determining the relationship between cumulative damages and times, and the working life of the bridges was estimated. This method was applied to the calculations of T-beam bridges, and the influences of spans, transverse diaphragms, reinforcement ratios, vehicle loads, and S-N curve equations were analyzed. The calculation results showed that vehicle loads and S-N curve equations determine the accuracy of working life. The calculated life in accordance with the fatigue vehicle model in the specification is much longer than the design life. The load varies greatly from region to region. Compared with Guizhou Province, Jiangsu and Liaoning provinces have a higher traffic flow of heavy vehicles over 35 t, which results in years unfilled with the design life. With the increase in spans, the working life increases accordingly because the reinforcement ratios increase with the spans. The diaphragm plates and reinforcement ratios have a great influence on the working life. The working life of bridges with diaphragm plates is 18%-63% lower than that of bridges without diaphragm plates. The reinforcement ratios are lower, and the reduction rates of the working life are greater.