Internal Force Analysis of Parabolic Arch Considering Shear Effect under Gradient Temperature

This paper theoretical analysis the internal force of the fixed parabolic arches under radient temperature gradient field incorporating shear deformations. The effective centroid of the arch-section under linear temperature gradient is derived. Based on force method and energy method, the analytical solutions of the internal force of fixed parabolic arches at pre-buckling under linear temperature gradient field are derived. A parameter study was carried out to study the influence of linear temperature gradient on the internal force of the fixed parabolic arches with different rise-span ratio and varying slenderness ratio. It is found that the temperature gradient and the rise-span ratio has a significant influence on the internal force of the parabolic arches, the influence of shear deformation causes the bending moment increase while the axial force decreases, and the axial force of parabolic arches decreases as the rise-span ratio increases.

Ultimate spans and optimal rise relations of steel arches

<p>Arched structures have been in use more than three thousand years. The span length of the arch in bridge construction has already exceeded 550 meters. Even longer arch bridges have been designed. The development of arch structures has not been as fast as in cable-stayed bridges during the resent 30 years, when cable-stayed bridges have reached spans more than 1100 m. However, arch structures are becoming more common, especially in bridges.</p><p>The purpose of this paper is to arouse interest in arch structures as well as to open up basic issues related to optimal arch design. The paper discusses the parabolic arch, the catenary arch, and the constant stress arch. The optimum heights, which produce the minimum amount of material, are solved. The importance of form- finding design is emphasized.</p><p>The optimum heights are solved mathematically. In addition, a non-linear iteration procedure, based on vector algebra solution, is used in finding the optimum shape of the moment-less arch. The applications of traditional graphic static and the usage of vector algebra are useful practical tools for designers, especially during the preliminary design stages.</p><p>The maximum theoretical arch spans are remarkably long. At a stress level of 500 MPa, the ultimate span of a steel arch is 19 635 m. The optimal heights of the arches are bigger than traditionally expected. For example, for a parabolic arch, the optimum span to height relation l/h is 2.309. It can also be mentioned that the optimum height ratio of 2.962, derived for the catenary arch, has so far been an unknown figure for designers.</p><p>The theoretical maximal dimensions resolved in the paper indicate that the dimensions of arches can be increased further.</p>

Simple innovative comparison of costs between tied-arch bridge and cable-stayed bridge

The proposed paper compares tied-arch bridge alternatives and cable-stayed bridge alternatives based on needed load-bearing construction material amounts in the superstructure. The comparisons are prepared between four tied arch bridge solutions and four cable-stayed bridge solutions of the same span lengths. The sum of the span lengths is 300 m. The rise of arch as well as the height of pylon and cable arrangements follow optimal dimensions. The theoretic optimum rise of tied-arch for minimum material amount is higher than traditionally used for aesthetic reason. The optimum rise for minimum material amount parabolic arch is shown in the paper. The mathematical solution uses axial force index method presented in the paper. For the tied-arches the span-rise-ration of 3 is used. The hangers of the tied-arches are vertical-The tied-arches are calculated by numeric iteration method in order to get moment-less arch. The arches are designed as constant stress arch. The area and the weight of the cross section follow the compression force in the arch. In addition the self-weight of the suspender cables are included in the calculation. The influence of traffic loads are calculated by using a separate FEM program. It is concluded that tied-arch is a competitive alternative to cable-stayed bridge especially when asymmetric bridge spans are considered.

Curvilinear steel elements in load-bearing structures of high-rise building spatial frames

The application of curvilinear elements in load-bearing metal structures of high-rise buildings supposes ensuring of their bearing capacity and serviceability. There may exist a great variety of shapes and orientations of such structural elements. In particular, it may be various flat curves of an open or closed oval profile such as circular or parabolic arch or ellipse. The considered approach implies creating vast internal volumes without loss in the load-bearing capacity of the frame. The basic concept makes possible a wide variety of layout and design solutions. The presence of free internal spaces of large volume in "skyscraper" type buildings contributes to resolving a great number of problems, including those of communicative nature. The calculation results confirm the basic assumptions.

Out-of-Plane Elastic Stability Analysis of Parabolic and Circular Arches

Effects of different load modes, rise-span ratios and support conditions on out-of-plane buckling and differences between parabolic and circular arches were studied. With the increase of rise-span ratio, buckling loads of arches under vertical load uniformly distributed along the horizontal line get bigger and bigger compared with those of vertical load uniformly distributed along the axis. With increase of rise-span ratio, the buckling loads of hingeless and two-hinged arch increase after decrease, then decrease. The buckling load of three-hinged arch decreases after increases. When rise-span ratio is small, support condition has a great influence on out-of-plane buckling. The parabolic arch is better than circular arch in out-of-plane stability and economy. But circular arch is better than parabolic arch in manufacture.