砌体墙—钢筋混凝土墙组合结构混凝土墙数量的优化准则证明

将砌体墙—钢筋混凝土墙组合结构连续化,按振型组合法证明了同时满足规范允许顶点侧移和层间侧移角的最少抗震混凝土墙数量为最优混凝土墙量,相应的设计为最优设计。

合理的钢筋混凝土墙数量对砌体墙—钢筋混凝土墙组合结构变形和受力性能的影响

针对砌体墙—钢筋混凝土墙组合结构的受力和变形特点,采用砌体墙—钢筋混凝土墙组合结构非线性地震反应分析程序MRCSA1.0,对组合结构进行非线性动力时程分析及静力非线性分析,探讨了当钢筋混凝土墙的数量合理时对组合结构变形和受力性能的影响。

砖混组合结构特征刚度系数对混凝土墙数量的影响

根据砌体墙钢筋混凝土墙组合结构的受力特点,提出了在地震作用下混凝土剪力墙合理数量的计算公式,公式中混凝土墙数量的取值参数的主要影响因素为:场地特征周期、抗震设防烈度、弹性层间位移角限值、组合结构特征刚度系数、非承重墙的自振周期折减系数等。并针对刚度特征系数这一主要影响因素,给出混凝土剪力墙合理数量计算公式中混凝土墙数量的取值参数在不同抗震等级、不同场地类别和设计分组的情况下的取值表。算例表明方法简单实用,可用于地震区此类组合结构的初步设计阶段。

砌体墙—钢筋混凝土墙组合结构中混凝土墙的合理数量(Ⅰ)

根据砌体墙—钢筋混凝土墙组合结构的受力特点,提出了在地震作用下混凝土剪力墙合理数量的计算公式;并针对影响混凝土墙合理数量的主要因素,给出了在不同抗震等级、不同场地类别和设计分组情况下的混凝土墙合理数量表。方法简单实用,可用于地震区此类组合结构的初步设计阶段。

砌体墙—钢筋混凝土墙组合结构中混凝土墙的合理数量(Ⅱ)

根据砌体墙—钢筋混凝土墙组合结构的受力特点,提出了在地震作用下混凝土剪力墙合理数量的计算公式;并针对影响混凝土墙合理数量的主要因素,给出了在不同抗震等级、不同场地类别和设计分组的情况下混凝土墙合理数量表。方法简单实用,可用于地震区此类组合结构的初步设计阶段。

预应力混凝土铁路斜拉桥

一、引言预应力混凝土斜拉桥是最近20年迅速发展起来的新型桥梁结构。由于它具有一系列突出的优点,在公路桥梁中应用日益广泛。铁路上因活载引起的振动和疲劳影响较大,至七十年代初才开始出现预应力混凝土斜拉桥。迄今只有西德、日本、英国和我国各建成一座。

世界海峡隧道简介

拿破仑为称霸欧洲,曾设想修建英法海峡隧道,由于当时技术条件的落后,这只能是梦想。然而现代技术的进步和经济、政治发展的需要,这种梦想正在成为现实。现将世界上已经建成或正在施工以及筹划中的海峡隧道简介如下:

桥梁墩台施工技术

一、墩台模板根据《公路桥面施工技术规范》(JTJ041—89)的规定,模板的设计与施工应符合如下要求。1.具有必须的强度、刚度和稳定性,能可靠地承受施工过程中可能产生的各项荷载,保证结构物各部形状、尺寸准确。2.尽可能采用组合钢模板或大模板,以节约木材、提高模板的适应性和周转率。

Air-void parameters measurement of fresh concrete and hardened concrete

Air content, spacing factor and specific surface of fresh concrete and hardened concrete with different air contents, slumps and mineral admixtures (fly ash, slag, fly ash + slag, fly ash + slag + silica fume composite) were studied by the air-void analyzer (AVA) method and the microscopical method. The correlations between the test results obtained from different methods were analyzed. The results show that, there is a close correlation of air content and spacing factor between the fresh concrete and the hardened concrete, but the specific surface correlation is weak. The air content of concrete measured by the AVA method is smaller than that of the pressure method and the microscopical method, because AVA device captures only the air voids with the size smaller than 3 mm. Spacing factor of the fresh concrete measured by the AVA method is greater than that of the hardened concrete measured by the microscopical method, while the specific surface is smaller. When the criterion of 4%-7% air content measured by the pressure method and microscopical method is acceptable for concrete freezing-thawing (F-T) durability in cold weather, the air content measured by the AVA method should be 2.4%-4.6%. For the concrete F-T durability, when the criterion of the spacing factor measured by the microscopical method is 300 μm, the spacing factor measured by the AVA method should be 360 μm.

混凝土减排图解

每年全球水泥和混凝土的生产会排放大量二氧化碳,但这也代表着巨大的减排潜力。混凝土无处不在,它构成了建筑、公路、人行道、桥梁和几乎所有可以想象的建筑结构。在地球上的所有人造材料中,混凝土数量最多。随着经济的发展,混凝土的使用量还在增加。水泥是混凝土中将沙子或碎石黏在一起的粉状黏合剂,也是地球上生产过程中能源使用最密集的产品之一。

Holography,UV/IR Relation,Causal Entropy Bound,and Dark Energy

The constraint on the total energy in a given spatial region is given from holography by the mass of a black hole that just fits in that region, which leads to an UV/IR relation： the maximal energy density in that region is proportional to Mp^2/L^2, where Mp is the Planck mass and L is the spatial scale of that region under consideration. Assuming the maximal black hole in the universe is formed through gravitational collapse of perturbations in the universe, then the ＂Jeans＂ scale of the perturbations gives a causal connection scale RCC. For gravitational perturbations, RCC^-2= Max （H＋ 2H^2, -H） for a fiat universe. We study the cosmological dynamics of the corresponding vacuum energy density by choosing the causal connection scale as the IR cutoff in the UV/IR relation, in the cases of the vacuum energy density as an independently conserved energy component and an effective dynamical cosmological constant, respectively. It turns out that only the case with the choice RCC^-2 = H＋ 2H^2, could be consistent with the current cosmological observations when the vacuum density appears as an independently conserved energy component. In this case, the model is called holographic Ricci scalar dark energy model in the literature.

Evaluation of surface textures and skid resistance of pervious concrete pavement

Surface textures had long been recognized as primary factors to provide the skid resistance on pavements; however, no measurement of skid resistance on pervious concrete pavement with various surface texture parameters had been made. Fractal geometry was introduced in the present work to accurately simulate transect contour curves of pervious concrete specimens through fractal interpolation. It is proved that its fractal dimension (D) can be adopted to measure the skid resistance on pervious concrete pavement, overcoming the shortcomings of both macrotexture depth (DT ) and British portable pendulum number (NBP). Combined with Fujikawa-Koike tire/road contact model, the optimization method of all surface textures was recommended for designing and constructing excellently skid-resistant and noise-absorptive pervious concrete pavement. In addition, evaluating of the abrasion process and attenuation of the surface textures on concrete pavement slabs was also the focus of this work based on accelerated abrasion test. Results show that the surface textures on pervious concrete pavement slabs is extremely durable, compared to those on conventional grooved or exposed aggregate concrete pavement slabs.

Chloride diffusivity in flexural cracked Portland cement concrete and fly ash concrete beams

In order to examine the effect of load-induced transverse cracks on the chloride penetration in flexural concrete beams, two different concretes, Portland cement concrete(PCC) and fly ash concrete(FAC), were tested with various crack widths. Total 14 reinforced concrete(RC) beams, ten of which were self-anchored in a three-point bending mode, were immersed into a 5% NaCl solution with the condition of dry-wet cycles. Then, the free chloride ion contents were determined by rapid chloride testing(RCT) method. Based on the proposed analytical models of chloride penetration in sound and cracked concrete subjected to dry-wet cycles, the apparent chloride diffusion coefficient and chloride diffusivity of concrete were discussed. It can be found that the performance of chloride diffusivity in both concretes will be improved with the increase of crack width, and that the influence of convection action will also be augmented. Based on the two samples obtained in sound concrete after 15 and 30 cycles, the time-exponent, m, for chloride diffusion coefficient was determined to be 0.58, 0.42, 0.62 and 0.77 for PCC1, PCC2, FAC1 and FAC2 specimens, respectively. Finally, two influencing factors of fly ash content and crack width on chloride diffusivity were obtained by regression analysis of test data, and it can be seen that factors kf and kw can be expressed with quadratic polynomial functions of fly ash content, f, and crack width, w, respectively.

首体练习馆综合技术

首体练习馆位于北京市海淀区白石桥东侧,现首都体育馆北面,是亚运会新建的球类练习场地,建筑面积38000平方米。一、预应力钢筋混凝土门式柱施工技术。门式柱柱高23.5米,六边形变截面,下小上大,柱身上半部分向内延伸。每根柱混凝土数量为70立方米,除常规钢筋外,另设4束预应力钢绞线。柱身外表面要求保持原生混凝土面。