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Heavy duty gantry crane is a type of bridge crane, with single girder and double girder types. The main girder is supported by two brackets. It is mostly used for outdoor operations and moves on wheels, rails or rail systems. Workshops, warehouses, freight yards, railways and shipyards use gantry cranes as a variant of overhead cranes as a lifting solution. It is mainly used for bulk cargo loading and unloading in open cargo yards, storage yards, and bulk cargo. The outdoor gantry crane has the characteristics of high site utilization rate, wide operation range, wide adaptability and strong versatility.

Main beam form
1. Single girder
The single main girder gantry crane has a simple structure, is easy to manufacture and install, and has a small mass. Most of the main girder is a partial rail box frame structure. Compared with the double girder gantry crane, the overall rigidity is weaker. Therefore, this form can be used when the lifting weight Q≤50t and the span S≤35m. There are two types of L-shaped and C-shaped gantry legs for single girder gantry cranes. The L-type is easy to manufacture and install, has a good stress condition, and its own mass is small, but the space for hoisting goods through the outriggers is relatively small. The C-shaped leg is made into an inclined or curved shape, and the purpose is to have a larger lateral space so that the goods can pass through the leg smoothly.
2. Double main girder
The double main girder gantry crane has strong bearing capacity, large span, good overall stability, and many varieties, but its own quality is larger than that of the single main girder gantry crane with the same lifting capacity, and the cost is also higher. According to the structure of the main girder, it can be divided into two forms: box girder and truss. Generally, a box-shaped structure is used.
main beam structure
1. Poprečna greda
Konstrukcijski oblik zavaren ugaonim čelikom ili I-gredom ima prednosti niske cijene, male težine i dobre otpornosti na vjetar. Međutim, zbog brojnih tačaka zavarivanja i nedostataka same rešetke, rešetkasta greda ima i nedostatke kao što su veliki otklon, mala krutost, relativno niska pouzdanost i česta kontrola mjesta zavarivanja. Pogodan je za lokacije sa nižim sigurnosnim zahtjevima i manjim kapacitetom podizanja.

2. Box nosač
Čelična ploča je zavarena u kutijastu strukturu, koja ima karakteristike visoke sigurnosti i velike krutosti. Obično se koristi za portalne dizalice velike i super velike tonaže. Kao što je prikazano na slici desno, MGhz1200 je najveća portalna dizalica u Kini sa kapacitetom dizanja od 1.200 tona. Glavni nosač ima strukturu kutijastih nosača. Kutijasti nosač također ima nedostatke visoke cijene, velike težine i loše otpornosti na vjetar.
3. Saćasta greda
Općenito se odnosi na „jednakokraku trokutastu saćastu gredu“, kraj glavne grede je trouglast, na kosom trbuhu sa obje strane ima rupe za saće, a na gornjem i donjem dijelu ima tetive. Nosač sa saćem apsorbira karakteristike rešetkastog i sandučastog nosača, te ima veću krutost, manji ugib i veću pouzdanost od rešetkastog nosača. Međutim, zbog zavarivanja čeličnih ploča, vlastita težina i cijena su nešto veći od onih kod rešetkastih greda. Pogodan je za gradilišta ili dvorišta sa gredama koja se često koriste ili imaju težak kapacitet dizanja. Budući da je ova vrsta grede patentirani proizvod, ima manje proizvođača.